All parts are NOS and genuine. PayPal. Shipping - First Class package with tracking /
delivery confirmation. Here the list of countries with International delivery tracking
service (excluding unfriendly countries):
https://www.usps.com/international/first-class-package-international-service.htm
Postage to:
USA - 6$
Canada - 17US$
Europe - 18...19US$
All parts are stored in conductive foam. LIST IS CURRENT.

Dual:
2SK270A -BL, -12, $10/ea, better than 2SK270=2SK389
2SK332 -E, -12, $8/ea, (2SK222-E×2, LN, Sanyo) -better replacement for 2SK117•K184•K163
uPA63H -L2, -12, $6/ea

UP07 -C, -22, $3/ea, TO-126-insulated, 100V, several W power, (4-12mA)
UN07 -D, -14, $4/ea, TO-126-insul, 100V, (8-24mA)
2SJ32 -B, -8, $3/ea, TO-39, 150V, (5-10mA)
2SK121 -"2", -6, $2.50/ea, (2.7-5.5mA), Sony, update for 2SK43
2SK163 -K2, -6, $3/ea, (3.5-6mA)
2SK163 -M1, -5, $3/ea
2SK170 -BL, -2, $4/ea
2SK223 -E, -12, $2.50/ea, 80V
2SK369 -GR, -6, $5/ea
J177, Siliconix, -30+, $1/ea

Small capacitance MOSFET -$4/ea:
2SK511 -6, TO-126, Vgs on these 4V+
VN88AFD -8, TO-220, Vgs on these 2V+
2SJ77 -18, TO-220
LND150N8 -8, "big" smd with tab for heatsinking, $2 for 2 pcs, $6 for 8 pcs

BJT:
TO-126, $2/ea
2SC2682 -Q, -4
2SC2911 -R, -10

TO-92L -$2/ea:
2SA1208 -T, -3
2SA1370 -E, -12
2SA1460 -L, -10 + 2SC3733 -L, -10
2SB605 -K, -6
2SB716 -E, -2 + 2SD756 -D, -2

It works just fine but after a while tip gets a qotaing and the solder dont melt anymore .I must have about 10 tips that is like that.
Is there something I can do to get reed of this quoting?

Hi
Some time ago I started thinking about improving my Le monstre. At the same time I was convinced of the superiority of SMD tantalum resistors in audio and I decided to make a complete tantalum version including my regulators which are essentially improved Walt Jung superregulators.
Due to obligations at work, I'm quite late with the plan, so for now I've made new PCBs for the amplifier and the rectifier itself, the regulator PCBs have been made but the regulators haven't been finished or tested yet (except for the positive one). I also have to make some modifications in the box itself due to the different placement of the transformer.
So far, there is still a lot of work to do. To begin with, here are some pictures of how it looks for now.

I know the nytech well, I know the Ion well, but this one, I can not understand his problem and I'm tired of the disassemble / reassemble to repair it.
one channel works well, the other explodes.
I repair the exploded channel, it is the other that fails, and so on 9 times.
no preliminary symptoms, bias / temperature / stable tension,
then he explodes.
all the transistors have been changed several times, only Philips and ST semi originals, all the diodes changed, all the capacitors, almost all the resistances.
several attempts with transistors of the same family but slower, nothing works, it explodes.
I could see the last time for a split second, the consumption mounted on my meter, I did not have time to note the final value but when I looked it exceeded 1A.
the only thing I did not try is another power transformer, but then I'm fed up, I gave up.
maybe one day in the future, someone will have the same problem and find the solution and maybe he'll post it here.

I own English made Ion System amplifier and tube amplifier also. Love listen to good music with particular preference to North European contemporary jazz with my equipment. Mainly from FLAC source.

I’m repairing this amplifier for a friend, and this one has given me several headaches. When I received it, the input board had multiple blown out traces, as well as multiple dead transistors. I did a full electrolytic recap as well as replaced all of the black flag capacitors with silver mica of equal value. I also replaced several zener diodes. I am now at a place where I want to do a bit of testing before I go further with any work.

On power up (on DBT) I found the bulb went bright as the bulk capacitors charged up, and then went dim and then a second later went slightly bright again. Also ans I was monitoring the bias current it went up quite a bit ans well. After a bunch of trial and error as well as input from others, I found that the amplifier was oscillating. I am seeing a 2 MHz oscillation at the input of the protection relay.



Trying to figure out where it was originating from I found that when I removed the pre out/amp in jumpers on the back of the amp that the oscillating went away and no more brightening of the bulb and bias was stable.

So that told me the oscillating was originating in the preamp, right??? Measuring at the preamp output with it disconnected from the amp input I was seeing nothing. No oscillating whatsoever.



If I turned the volume pot all the way up, I would get oscillating, but only at the very end of turn. And the oscillating that I was seeing was not increasing as I turned the volume pot, it wasn’t there, and then all of a sudden appeared at the end of the turn, plus this oscillating was 24 MHz.



I’m hoping to get some suggestions on where to look, I am confused as to why the amplifier goes into oscillation when it’s input is connected to the preamplifier output.

Really appreciate it!

Dan

Presenting the documentation for the F5m appearing shortly in the store.

The Essentials kit consists of the Jfets and Mosfets plus two channels of pc board and 1 power supply pc board.

The Completion kit is everything else except chassis, power transformer, rear panel connectors/switch/ac inlet.

The kit is designed around several chassis available in the store, but is fairly agnostic.

Attached is the article I wrote for this project, and this is the support thread.



2/11/2024 After testing by member 6L6, I revised the power supply layout and made an additional
note about the power supply thermistors with higher output stage biasing. The revised article is labeled
R1, and both are attached below.


Update Alert: It turns out that the insulators we bought were not very insular. Not a disaster in general
but a problem if your heat sinks are bare metal. Different pads are available for this.

See the details in post 1,003 of this thread.

Also note 4/21/2024 revision of the power supply board.


EDIT: Build Guide here - https://guides.diyaudio.com/Guide/F5M+Amplifier/29?lang=en

HI, my name is Cristiano, 49 years old, IT guy with passion on Home Theater and audio related stuff!

Winslow Burhoe has had a stroke; tomorrow they will operate to clear a partially blocked carotid artery. Here's a photo from my birthday lunch 10 years ago: Left to Right, My friend Gero, my adult daughter, and Winslow.

Prayers or positive thoughts, please!

I'll update as soon as there is news.

john

I am a friend of the son of Eric Thomas, who used to own and run Beauhorn. Eric recently passed away and left a number of interesting and unusual pieces of hifi equipement to his family. This included a Tentlabs CD player, which is unfortunately only working on one channel.

Does anyone know anyone in the UK (preferably south east) or possibly Europe that would be able to look at this with a view to fixing it?

Thanks for your help.

Good afternoon all.
I'm jon aka the1eyejon, live in kent (england) and i am trying to better my DIY pcb skills as a hobby. I have good basic electronics knowledge and am more interested in component level repairs.

Hi all,

I'm Connor, a Mancunian currently living in London. I have lots of vintage music equipment and have been recently interested in electronics repair and design. I have been on a quest this year to fix all my broken gear, as well as seeing how the electronics work inside the gear. I teach music production at the Uni of Westminster, and have a strong background in studio and live music production.

Kind regard
Connor

I received a 6 channel headphone amp from a friend of a friend asking me to take a look at it as a couple of channels have hum on them. I figured it wasn’t a power supply thing since only couple channels had the hum on them.



I took a listen and found that channels 1-3 were quiet. Then channel 4 had a very light hum, 5 a bit louder and 6 the loudest. I felt it wasn’t a coincidence that as you get closer to the power transformer the louder the hum gets. Being these three.


It has a single center tapped secondary winding and each side of the winding goes into a 1N4001 and their cathodes are tied together providing a single rail of 30.8V. So at the cathode of one of the diodes I tapped in with one of my power supplies.


With my power supply running the amp it functioned perfectly and not a hint of hum on any of the channels, dead quiet. So this told me it had to be the power transformer. There is a steel sheet barrier, but I used copper tape help seal any opening and create a better shield. First wrapping the power side in kapton for safety.




This really hasn’t helped at all, maybe slightly reduce the hum in channel 4 which was pretty low already, but 5 and 6 are still pretty loud.

Can anything be done?

Dan

Hi, my name is Davor, and all my life I'm an audio and DIY enthusiast. My last projects are mainley related to OB speakers.

We can't always afford polypropylene capacitors, much less
Teflon (tm), so we often make do with electrolytics when
we need those higher values.

There's all sorts of caps out there with claims to being better,
and they certainly are more expensive.

My favorite is the Elna silk capacitors, available from Digikey,
and really cheap. The measure spectacularly, sound great,
and the manufacturer's translated description of why they
sound better is a Babelfish classic.

So before you run out and spend a lot on the highly hyped
spendy caps, try the Elna silk caps.

There's hemp in them, too.

😎

Hi,

I've recently bought a Bose model AV18 Media Center and its brother PS28 II Powered Speaker System. Unfortunately, I do not have the cable to digitally connect the two items (8pin mini DIN connector on the media center, RJ45 on the speaker).

The cable can be found on ebay (for instance here: https://www.ebay.co.uk/itm/16618116...128FgunGWRBezGQ1UoRQ0p7g==|tkp:Bk9SR7qel_icYg ), but frankly speaking I don't want to spend more than 50-60 EUR for it...

Any idea about the connectors' pinout scheme of both ends?

As usual, thx a lot in advance to everyone 🙂

I have been building tube amps/preamps for years and a few solid state phono preamps along the way (I am an ex CET). I am intrigued by the many versions of the gainclone type of chipamp and want to build one. I see no point in having my own PCBs made with the many that are out there.

The prices are all over the place some too cheap to be true (ebay etc.) and others quite pricey. Not keen on spending a couple of hundred dollars on 2 signal and 1 power supply PCB. BTW I make my own enclosures.

Are there any decent PCBs for the LM**** chipamps available? Or does anyone here have any? I am not as concerned about the power supply
PCB as that is pretty standard.

Thanks!

I am currently trying to design a portable bluetooth audio DAC, and have made a schematic that I think might work.
I know that the bluetooth wiring works (have tested direct audio from the chip, but not through the amplifying circuit).
I have been getting quite confused on how many capacitors/resistors to use, and what ohms. I want to maintain audio quality/reduce noise, as much as possible.
Am I on the right track, and will the op-amp circuit work? (I haven't tested it on a breadboard, as some of the parts haven't arrived yet).
The raw audio output volume from the bluetooth chip is about half what I would like, so the amplifier circuit should be wired to produce 2x gain.
Everything is powered by a single battery.
Thanks!

For more than 20 years I have made myself available to Steinway & Sons, when they had questions that were up my alley. So, when I had a loudspeaker design client who was willing to pay, I asked Steinway's outside contractor for special finishes (such as a grand piano in high-gloss Danube Blue Polyester) to do the final finishes on the Richlite cabinets. The front panel perimeters however, got seven hand-rubbed coats of violin varnish. The rear panels, also Richlite, are held on by Silicon-Bronze boat-building screws. Gotta Luvvit. BTW, it's my LS/5.25.

Black face Sansui AU-9500 for sale. Everything works and sounds great. I simply have too many receivers at the moment. I am looking to get in the ballpark of $750 but make me an offer. I live in Corvallis Oregon. Shipping is possible but you may have to help make the arrangements. Don't let this one get away.

I read online it was not good practise to run a turntable without the platter. I recapped a JVC QL-A7 turntable and my next step is to check voltages. To check voltages I need to turn the turntable is upside down to get to the circuit board and in some cases turn on the motor. Will this be an issue?

I was looking around for quite some time trying to find a simple buffer to drive my high gain power amplifier and now I am really interested about this B1 project, so Mr. Pass are there any news about it?


Will it contain also volume control and selector as complete preamp unit?

I would like to build the F2J amplifier and would prefer PCB's than perf board for the build. Does anyone have a pair of boards for sale?

hello can i swap those diode the original is ISL9R3060P2 to IDP30E65D2XKSA1 ???????

I recently encountered a request on another forum as to the suitability of Quad 405 for driving Stax headphones as a Class A amplifier. There seems to be a number of about 10 Watts class A output floating around, based on the quiescent dissipation of the "class A" amp of around 5 watts (which is hopelessly wrong in this circuit). I have long been interested in the circuit, impressionably growing up in the 70's 80's. I dusted off the simulation that I did 10+ years ago, of the 306 circuit. I approximately calculated the class A output into 8 ohms of 100uW of the 306 which has a bias of one diode drop between the basses of the "dumpers".

Unfortunately the thread is in a bit of a backwater of that forum and hasn't been critiqued sufficiently for my satisfaction, of if I am in the right ball park, it is a bit of a controversial claim. So peer review please. I am quite happy for my slightly flippant comment about the bridge inductor filtering out the crossover glitch to be criticised, and I know there is more than just that going on with the bridge feedback, but that's what it looks like.

Cut and paste from "another Forum"

Morning, I too have been fascinated by the current dumping spiel of the 405, and a general lover of pre 90's Quad in general. So much so that I did try and build one when I was young (didn't work) and more recently as a grown up engineer decided to simulate the circuit (of the 306, because the audio is not going through an op-amp). Stable biasing of the class AB amplifier is a problem and the Quad seems to present a neat circumnavigation, hence my curiosity.

Most transistor amplifiers have a class A Vas stage, the 405 / 306 is no exception, except it is a bit beefier and is connected to the output by a resistor of around 47 ohms. The voltage generated across this resistor determines when the current dumpers are turned on. Due to the biasing arrangement that is approximately +- 300mV.

300mV / 47ohms is about 6.4mA.

6.4 mA x 8 Ohms = 51mV

Convert that into RMS about 36mV of class A at the 8 ohm speaker 100uW (if my maths is correct) before current dumping occurs. I don't know what the input impedance of the headphones is but presumably significantly more than 8 ohms and everything works out!!

I have not built or tested a current dumping amp in person, yet, but in my simulation of the 306, the area where the magic happens, in my opinion, is the bridge. The basic current dumping amplifier is a class B (sorry) output stage rescued by feedback, to plaster over the switching discontinuity. Yes the super fast class A amplifier huffs and puffs through its 47 ohm resistor, but the magic happens in the bridge.

The switching discontinuity appears to be filtered out by the inductor. I don't really understand what precisely is going on, but it does the trick. It is a remarkable piece of work IMO, especially considering they didn't have the tools available we have today.

Voltage across the inductor simulating 1KHz 8W.

All comments are for entertainment purposes only.

https://www.hifiwigwam.com/threads/rekindling-interest.124470/post-2529901

Thanks

Hi,
my name is dirk, 60 years old and I´ve been sound engineer and trumpet player from cologne/germany.

As the thread title. Not too fond of the previous models as these did not have USB ports but this one has. So I am curious how it looks and how it performs especially via USB. The reviews are raving but maybe we should take those with a grain of salt 🙂

Hello All,

can somebody to share resistors values (R1-R12) of front panel Attenuator for Aikido All in one preamplifier?

I want to sell:
- Yamaha C-4 preamplifier - price 400 Euro. It looks very good and in original condition without repairs
- DAC TEAC D-T1 - price 380 Euro. It looks very good and in original condition without repairs

I can send in EU only and the shipping is around 25 Euro/item.

Please send me DM if you are interested or if you need more details.

Regards,
Vlad

Hi,

I am selling one upraded Marantz CD 50 player.
Is in very good condition and the changes have been made are:
- changed few capacitors from power supply;
- the standard op-amps output stage replaced with tube output stage;
- put in no-oversampling mode;
- changed the decoupling capacitors of the TDA1541 DAC.

The price is 350 euro (shipping included). I can ship only in EU countries.

Please send DM for more details.

I am a friend of the son of Eric Thomas, who used to own and run Beauhorn. Eric recently passed away and left a number of interesting and unusual pieces of hifi equipement to his family. This included a Tentlabs CD player, which is unfortunately only working on one channel.

Does anyone know anyone in the UK (preferably south east) or possibly Europe that would be able to look at this with a view to fixing it?

Thanks for your help.

On the effects is only "2" and "4" the 4 is for the subwoofer, and 2 is for stereo i think(2 and 4 from the total of the 4 outputs of the chip in theory)
I need separate efects for each channels! Not only the "2 " output, otherwise is useless, what to do? 🙁

Hi!

I found two old speakers with fullrange chassis. My idea is to build a bluetooth-corner-frankenspeaker out of them. While I don't think they would be exactly HiFi, I thought the typically warm sound with good point-sourcey understandabillity can be achieved. Subjectively they have a certain quality to them and go quite loud, as proven by feedback. Ooops!



I meassured them in their old enclosures and they seem to have some problems:
There is a huge phaseshift when the small cone starts to load at 1kHz, unpleasant harshness caused by the bump around 2,4kHz (?) and uneven hights, which could be caused by my quick meassurement setup.



Good part: despite the issue around 1kHz, phase response is really nice and it seems to me like they only need an EQ around 2,4Hz (-6dB/Q=1 maybe) to get that pleasant warm sound for a kitchen radio.

Next up would be finally soldering my measuring cable for T/S params, designing a BR enclosure out of scrap parts and buying a china bluetooth-dsp-amp board.

One question: is the phaseshift immanent to that kind of speakers?

All the Best! robo-klaus

Good afternoon all from a rainy England (summer "eye roll" )

I have 2x icepower 1000a boards with the same issue.
The board powers up ok, however produces no audio. It does not trigger standby or trigger the protection shut down. It just sits there with the peotection circuit happy as Larry just producing no sound.

Is there a common issue on these boards that would produce the same symptoms? As I have 2x boards with the exact same issue.

Unfortunately I do not have an oscilloscope, I am very DIY. I do however have a multimeter and good basic knowledge of circuitry.

While the transport I'm presenting in this thread is not really a clone, it all started with me picking inside Shigaraki and posting some pics on audiostereo.pl forum.

As those guys are quite resourceful, they quickly found that the same mechanism and similar chips are used in JVC RC-EZ31 boombox and the rest is history.

Now, after all those months, I'm quite puzzled why nobody so far came up with similar application? After all, Gainclone and Phonoclone gained so much popularity that easily surpasses the originals.

It all started when last September somebody asked me to build a PS for Shigaraki transport. I did that and had a chance to play with the transport in my own system. And while I was extensively using CEC TL0, ML31.5 and ML37 at that time, I was quite impressed by Shigaraki. In some ways it offered performance virtues none of my other transports could dream of, specifically the freshness and vitality of the sound, with very well defined PRAT (BTW, the PS based on 70VA Hammond transformer was in no way inferior to original Dumpty).

I was almost ready to buy a used Shigaraki or Flatfish when the alternative option emerged on Polish Forum. And although I was quite involved during all those months in development process, the discovery of the transport source and some fine points of modifications should be credited to other forum members there.

Now, after 6 months, my transport is almost completed and it took the spot of CEC TL0, becoming my main digital reference (I still keep TL0, both Levinsons and loaned Flatfish for comparisons).

The whole story can be read here: http://www.audiostereo.pl/forum_wpisy.html?temat=36475&p=1#k

.


While I was quite hesitant to post this info here, I think that discovery is too good to be kept secret, with time I will provide more details.
I used Shigaclone reference in the thread topic, but after some time will ask moderators to remove it.

Hello everyone,

I'm working on a device that converts audio data received over TCP/IP to AES3 format.
For this, I plan to use the DIT4192 chip together with an STM32F407/417 microcontroller.

The device is intended to support:

1. Sample rates up to 192 kHz
2. Up to 24-bit resolution
3. No audio proccessing is needed

I would really appreciate any help or suggestions, especially with the following:

1. What do you think about the choice of DIT4192 + STM32 for this task?
2. Are there any good C/C++ libraries (for Linux or bare-metal) that can handle audio decoding (MP3, WAV, etc.) and output via I2S (my guess STM HAL/LL does the work, but not sure)?
3. Do you know of any open-source or DIY projects that are similar or could be helpful as a reference?

Thanks in advance!

Hello

Recently I have build VSSA amp (shaan version bit modyfied) and I am very happy with it.
I had few irfp240/9140 pairs in stock so I decided to build another version (as I am not an expert some upgrades may be needed).
Bellow schematic, board, and measurements. The measurements were done on prototyp board and all components weren't matchet (just taken stright from the box).
Bias is stable, cold amp seted to 100mA (15C) hot amp 92mA (78C), I didnt have irf540/530 so I used irf840 instead. I think that amp can use bit higher power supply than +/-35V.
Amp is playing really good.
Thanks to LazyCat and Shaan


Ps
I was thinking If it would be recommended to leave 0,1R source resistors and put 47R gate resistors instead 100R ?
My sound card is not the top notch and is creating some high order harmonics artefacts (there are present at the same place on different amplifiers measurements).

I'm selling a DCB1 board with three current bias options: 1.5, 8 Ohm (Caddock MP930s) and 20 Ohm (Xicon 5W) so you can choose between > 850mA, 200mA or 90mA bias current. In my opinion the higher the bias the better the sound quality.

All parts are very good quality mostly if not all from Mouser
All fets signal and psu are original Toshiba's bought from Mouser, the signal ones are 2SK170GR fets ( > 6mA ) closely matched resulting DC offset which starts at 0mV and settles around -2mV and -3mV for each channel
Psu caps - 10.000uf Nichicon Gold Tune KG, 100uf Elna Silmic II, Wima MKP10
Signal resistors - Dale RN60C precision 0.1 % 50ppm

Soldered with Kester 44 (63/37)

135 euros included shipping worldwide. Paypal for friends

Hi,

I'm planning to build Troels Gravesen The loudspeaker 3, the drivers has arrived. The bass unit - 18 Sound 15W700, has spring loaded connectors with big holes.

What is the best way to connect the speaker cables, do I just strip the wire and let the spring make the connection, or shall I put banana plugs on the cables and push them through the hole? I feel like this is a stupid question but I want to make sure the cables don't come loose .

There are plastic caps on the top of the connections, similar to speaker terminals but I don't think these are to be removed, as there would be no way to differentiate between the positive and negative terminals.

Thanks for your help.

Hi All,

I have a Audio Research D-110 and confirmed the Left Channel modules are non-function. Does anyone can tell me where I can buy the modules? Or simply how can I fix them?

Thanks
Matthew

Would this sound good?

Hi ! Does anybody knows the right way to use copyrated music to record from line out or record with microphone in order to make a wav file with comparsion and post it here at forum or google drive for example ?

I installed SB Acoustics 8" Fullrange(SB20FRPC30-8) in TQWT.

Well-extended bass.
Natural mid and high range with little grating.
High quality throughout the all range, and the performance is above the price.

Login to view embedded media

Hi all,

I would just like to share my project - raspberry pi 24bit/384k I2S card



Here's my page about this project:

alexx DIY audio page

i hope it will be interesting....

Hi everyone! I'm Stefano from Italy.

I'm a master student in electronic engineering (relatively) close to graduation. I normally work on digital stuff (digital radios and digital design for mixed signal applications) but I have a long standing fascination towards analog design, with focus on music and audio in general.

I started out with a thrifted Sony AVR (DB840) with thrifted Revac HP 102 loudspeakers. Now I'm working on a malfunctioning Nikko NA-400 and I'm trying to build my own version of the STK465 amplifier module with modern discrete components to make it available to the community since reliable new old stock by Sanyo is dwindling and clones available on the internet come from unknown sources.

I admit I was highly reluctant to buy a Chinese product, like most of the people in my country, but at the end I did it, and have absolutely no regrets: this Chinese tube amps is probably one the biggest bargains in the audio world.

Description:
12Wx2 EL34B+6N2 SE Tube Amplifier with 5Z4P rectifier

Official Features:
- Input voltage: 220V
- Power supply: 160W
- Output power: 12W x 2 (ultra-linear connection)
- Frequency response: 20Hz - 28KHz
- military grade dual triode 6N2J as voltage amplifier
- Shuguang EL34B as power tube
- Shuguang 5Z4PJ as rectifier
- THD: <1% @ 1KHz
- Output impedance: 4Ohm and 8Ohm
- Input Impedance: 100KOhm (two input signals)
- Input sensitivity: 750mV
- SNR: >88dB
- Power transformer: 96x50mm 0.35mm z11 using imported 96mm slicone steel plates in 0.35mm thickness,Stack thickness is 50MM to ensure sufficiant power and low heating.
- Output transformer: 66x36mm 0.35mm z11 using 66mm slicone steel plates in 0.35mm thickness,Stack thickness is 36MM.
- Mirror surface stainless steel enclosure
- Diamond cutting corner feet
- Alps potentiometer
- Powder coating transformer enclosure
- Dimension: LxWxH 310×268×165mm
- Weight: 12Kg
- Price c.a. $250.00 + $110.00 shipment (purchased at 300 euro in Italy)


Additional circuital info:
-PRO: really amazing quality/price ratio: this amplifier has without any doubt a superb design for its price
-PRO: The mids are clean and the bass/highs are all there (I'm listening with 16 ohms fullrange loudspeakers). Not too much bright (which I really like), it sounds quite veiled and rolled-off (with stock EL34) but sufficiently detailed, thus there is no way you will get ears fatigue with this tube amp
-PRO: voltage amplifier with triodes in parallel to reduce noise and increase gain
-PRO: hybrid bridge rectifier using a valve rectifier and a pair of silicon diodes. You will still get the valve sound without the harshness of the silicon diode cutoff in reverse bias.
-PRO: choke is used as a power supply filter element
-PRO: Panasonic, Philips and Nichicon brand capacitors
-PRO: all components are well dimensioned and never run hot
-PRO: PCB and very clean wiring
-PRO: safety: the amplifier is internally correctly grounded/earthed

-CONS: the noise floor is quite poor, but this noise is modest and does not at all interfere with the listening
-CONS: missing 16 ohm output
-CONS: missing EL34 grid stopper resistor
-CONS: the inside iron core inductor looks not to be well fixed to the chassis (only from one side), which, I think, could be a problem if you think to a very long shipping distance
-CONS: shipping box content is minimal, that is just the amplifier without brand, marks or labels and no documentation (but this is fully justified by the price)

______________________________________________________________________________________________________________

MAJOR IMPROVEMENTS OF MINE (have immediately void the warranty!):

1) Stock version: Ultra-Linear mode connection only
Modification: added front panel “bright chrome” switch to select between Triode and Ultra-Linear mode

Triode mode is more pure, with less distortion and more open sound but the UL has more power and dynamic...it is your liking. In every amp with user-switchable triode/ultralinear circuits, triode usually sounds better.

2) Stock version: EL34B power tubes
Modification: replaced with KT66 power tubes

No self-bias adjustment is required (according to Weber Bias Calculator) since KT66 has the same plate dissipation than EL34 (25W), but KT66 has higher load impedance requirement than EL34. That is also recommended if you run, like me, a 16 ohm speaker to the 8 ohm output since you are doublig the reflected impedance. Optimal burn-in times range from 100 to 300 hours. Most changes are happening in the first 150 hours. Also the 6L6GC high-power tubes have high internal impedance and work great in this amplifier on a 16 ohm load without requiring bias adjustment since exhibit similar consumptions to the EL34B (see last page measurements).

3) Stock version: two 1N4007 (in the hybrid power supply)
Modification: replaced with two ultra-fast SF4007 diodes, bypassed by 10nF snubbing caps

Walt Jung article gives the reasons for using fast recovery diodes and has actual measurements showing the large amount of RF hash generated by common 400x rectifiers.

4) Stock version: 220uf Panasonic Electrolytic (FC Series) cathode bypass capacitor (in the power output stage)
Modification: replaced with bipolar Sic-Safco 470+470uF back-to-back (+--+) capacitors, plus 2u2F polyester cap

Many folks have found that Bipolar Electrolytic Capacitors can make a noticeable difference when used as cathode bypass capacitors in tube amps. Read "Bipolar Electrolytic Capacitors" by Matt Seniff.

5) Stock version: unbypassed gain bias resistor (in the common-cathode triode amplifier)
Modification: added bypass cathode capacitor (bipolar Rubycon 1000+1000uF back-to-back (+--+) capacitors, plus 1uF polyester cap)

By adding bypass cathode capacitor you increase gain (recommended by KT66’s higher gain requirements) and rise mostly even harmonics. Being an even order harmonic, this is not a critical tonal issue, since even order harmonics stay musical (multiples of an octave).

6) Stock version: 220nF/400V Philips (MKT series) coupling capacitor between stages
Modification: replaced with 220nF/500V metallized paper-in-oil K42Y-2 Soviet Military Capacitor

PIO dielectrics are appreciated for their tonal balance that is very neutral and smooth. Audiophiles, studio guys, vintage collectors can all hear the difference with their own opinions on what is best. The main thing is that I agree that the cap upgrade is a good thing.

7) Modification: added bypass film 1uF/47nF capacitors in power supply (on the back side of the PCB) in parallel to electrolytics to filter out high frequency noise.

8) Stock version: three-pronged power cord with ground (earth) connected to the chassis
Modification: remove earth connection by plugging into a continental power adaptor which breaks the ground (earth)

By removing earth connection, the amplifier sounds quieter and better.

9) Stock version: no Global Negative Feedback
No Modification: give up to any Local/Global Negative Feedback

I tried from -1 to -6dB of NFB which makes a great influence in the final sound, but additional NFB made the amplifier sounding more and more as "solid-state". I preferred the stock version (no GNFB at all) since it sounds more harmonically rich which results pleasant to me.

10) Stock version: for safety reasons the common (or zero ohm) end of the OPT is grounded
Modification: floating outputs, and separated isolated L/R zero ohm returns

Amplifiers with no global feedback can leave the output transformer secondary floating, even if it is electrically unsafe. This opens the soundstage a little bit. Probably the floating outputs provides the (RF) noise-reduction benefits of balanced lines.

11) Stock version: EL34B self-biased at plate dissipation of about 15W (out of 25W max) by 500 ohm cathode resistor. That means cold/average dissipation.
Modification: KT66 self-biased at plate dissipation of nearly 19W (out of 25W max) by a reduced 410 ohm cathode resistor. That means hot dissipation.

Biasing the power tubes hot gives it a brighter and fuller sound.

12) Stock version: 5Z4 rectifier
Modification: replaced with Sovtek 5V4 rectifier (or even JJ GZ34)

The KT66s’ new adjusted bias is now drawing extra current, about 120ma, so too much close the maximum forward current of the 5Z4 (125ma max, 350V, 20V drop). The replacement with 5V4 (175ma max, 375V, 25V drop) or with GZ34 (250ma max, 450V, 17V drop) is just recommended because both tubes are low drop-out equivalents. At the end, after listening test, I even prefer 5V4 to the GZ34, probably due to the highest voltage drop and sag: the GZ34 is too close to “solid state” in the response and in some cases it yields voices quite metallic and fuzzy, for sure never as smooth and natural as delivered with the 5V4. Of course by using the 5V4 makes the KT66s running a bit less hot due to the higher drop in power voltage supply.

13) Stock version: the shared cathode resistor of the parallel 6N2 triodes is Rk= 2Kohm
Modification: triodes in the driver stage are re-biased hotter (Rk=840ohm)

The optimal plate load for a triode is around two to three times the plate resistance (which is nearly 47Kohm for the 6N2), thus the stock anode resistor looks well-dimensioned and I didn’t modify its value (75Kohm). Remember that parallel operation needs shared plate and cathode resistors at half the single triode value.
Pay attention that 6N2J (or 6N2P, 6N2P-EV) is not full equivalent to ECC83 (or 12AX7): both have an amplification factor nearly of 100, but, a part of the filament connections, the last has higher plate resistance (62.5Kohm) and slight shifted grid-voltage vs. cathode-current curves.
Since 6N2 triodes are now bypassed by a capacitor for a higher gain, changing the cathode resistor doesn’t modify the voltage gain, but only shifts the bias point: this modifies the headroom of the driver stage and the distortion level. As the bias point is shifted, the amplifier will clip more on the top or bottom portion of the waveform.
By lowering the cathode resistor from 2K to 840ohm, not only we increase and better centre the bias current, but also we obtain a better sounding harmonic distribution, the so called waterfall of 2nd > 3rd > 4th > 5th. Cathode resistor value was in fact chosen where the measured third harmonic component was minimum and the second harmonic dominant at an output power of 1 Watt. The soundstage turned out to be more "open" and "natural" that confirms all Psychoacoustics studies which say that even harmonics give a warmer, organic, and natural sound while odd harmonics impart a more harsh and metallic sound.

14) Added a Zobel RC network between the amp and the full-range 16 ohm speaker

Any amp is inductively loaded by a speaker, so the correct form for interpreting an inductive load on a plate current/voltage curve is an ellipse which may exceed the Max dissipation curve limit. A Zobel RC Network is designed to achieve a flat impedance, safer load.
This amplifier looks to sound more comfortable driving a flat-impedance resistive-like 16 ohm load, (from its 8 ohm output taps), which results in a better 3D image and stable focus

15) Stock version: input grid stopper resistor (in series with the grids of the driver triodes) is 10Kohm
Modification: input grid stopper resistor lowered to 3.3Kohm

The stock input stopper grid resistor is 10Kohm (but the triode, originally unbypassed, had a lower voltage gain of nearly 20). After bypassing the common cathode resistor of the parallel driver triodes for a higher gain, the voltage gain reaches nearly 70, and the grid resistor needs to be reduced of about one third, from 10K to 3.3K, due to the increased input Miller capacitance.
In fact the Miller capacity (that is twice for parallel triodes) is:
Cin = Cgk + Cgp*(A+1) =~ Cgp*(A+1) =~ Cgp*21 (when unbypassed)
or
=~ Cgp*71 (if bypassed)
then, Cin_bypassed =~ 71/21 Cin_unbypassed =~ 3.3 Cin_unbypassed thus, Cin_bypassed =~ three times Cin_unbypassed
The input capacitance of the tube (Cin), in conjunction with the impedance of the grid stopper resistor (Rg), forms a simple RC lowpass filter with a -6dB/octave slope. To maintain the original low roll-off frequency, Rg resistor should be reduced to one third, since Cin has been tripled. Frequency response is now back to be ± 1dB at 16 to 20000Hz.

16) Stock version: the interstage coupling capacitor is C=220nF and the KT66/EL34 grid leak resistor is R=470Kohm. Also the 6N2 grid leak resistor is R1=470Kohm.
Modification: coupling capacitor doubled to 440nF and KT66/EL34 grid resistor halved to 220Kohm, preserving the original RC cut-off frequency. The 6N2 grid leak resistor is cut from 470Kohm to 150Kohm.

A lower value grid leak resistor will be harder to drive, but will give a more constant load at different frequencies, and hence a more extended high frequency performance. In fact, the grid to plate internal capacitance of the following stage (whose value is also multiplied by the gain of the stage, due to the Miller effect) reinjects a fraction of the output signal back to the grid. It is nothing else that a local negative feedback whose effect increases with frequency and the gain. The Miller effect can cause loss of treble if the grid resistor is too high; the lowest the grid leak resistor, the lowest the feedback, the wider the bandwith. Miller capacitance not only affects high frequency response but it adds phase intermodulation distortions as well.
By halving the size of the grid leak resistor, we double the cut-off frequency and increase it by an octave, cutting the bass response. Viceversa, by doubling the size of the interstage coupling capacitor we halve the cut-off frequency and reduce it by an octave, allowing more bass response. By choosing a lower value of the grid leak resistors, we also lower the gain a tad, but not significantly. If we make both the modifications, the two effects will compensate each other, maintaining the original RC time constant, thus the original the cut-off frequency.
It is important that we should always aim for a corner frequency of one tenth of 20Hz (2 Hz) to avoid any phase shift in the lowest bass region.
We can easily double the existing capacitance by putting another identical capacitor in parallel. Putting two identical caps in parallel is a good thing and brings small advantages because we halve the intrinsic resistance and the cap's inductance.
Many folks have done intensive testing of input capacitors: parallel film capacitors sound better to their ears as they were found to sound "faster" than a single capacitor of the same value, but we are straying into highly subjective territory here.
Moreover, we could test to put a "PIO" together in parallel with a film and foil capacitor of the same value to create a tone circuit, because a pure PIO capacitor has been found to sound smooth but rolled off in the highs.
The output impedence for two 6N2 parallelled triodes (output taken from the plates, bypassed cathodes) is about:
Rs= Ra/2||Rp/2 = 47K/2||150K/2 = 23.5K||75K = 17.9Kohm
The impedance of the following stage (KT66/EL34) is just the grid resistor reduced to R= 470K/2~ 220Kohm.
The coupling interstage capacitor has been increased to C=0.22x2= 0.44uF
The new cut-off frequency at -3dB of the low end of the band will result equal to 1/[2*pi*(Rs+R)*C]= 1.5Hz, that is a desired pole frequency less than one tenth of 20Hz.
To change the grid leak resistors brings major tonal improvement to the tube amplifier, creating a soundstage with focus and realism.

17) Stock version: single value of cathode bias resistor on power tubes
Modification: added a front panel “bright chrome” switch to select among three different BIAS options: HOT, AVERAGE and COLD

This three-positions switch allows you to select among different cathode resistors (connected in parallel) that determine three different BIAS currents and consequently let run the power tubes slight colder or slight hotter than the average.
In Single Ended amplifiers (which always run in Class A, ergo do not suffer from crossover distortion) decreasing or increasing the bias current brings little tonal improvement due to the asymmetrical clipping and waveform compression which increases the content of the second harmonic distortion and enhances its ratio compared to the third and odd harmonics.
Bias adjustment is highly recommended after having swapped different tubes or after having switched between Triode and UL mode: you can observe in the attached table that various tubes (EL34/6L6GC/KT66) show slight different measured voltages and consumptions, thus exhibit distinctive tonal behaviours.
Hot bias shortens tube life and usually sounds more dynamic and fuller, but potentially harsher. On the other side, cold bias, for which tubes will last longer, in certain circumstances produces more natural tones, even if sometimes the sound results thin and lifeless.

_________________________________________________________________________________________________________________

Attached curves of the A10 amplifier after all my modifications, both simulated via LTSpice and measured on a PC-soundcard.

I measured a maximum power of 3.5 Watt on 15 ohms (10% THD) in Triode mode and 6 Watt in the Ultralinear operation, both channels working.

I would not comment the curves since I think almost everything is self-explanatory: I just ask you to bear in mind the mismatched impedance between the amp and speakers (I’m running a 16 ohm cab through the 8 ohm amp tap) and that now there is neither global nor local negative feedback in the triode mode, and just a negative feedback applied to the screen grid in the ultralinear operation.

I can't disguise the fact that the ZERO LOCAL/GLOBAL FEEDBACK TRIODE CONFIGURATION satisfies me completely regardless of the higher distortion and lower power output.

ANY COMMENTS ARE WELCOME!



My Homemade Tube Amplifier website: The Sound Grail, design, schematic, simulation and measurements http://tubeamplifiers.wixsite.com/thesoundgrail

I have a DIY build that is effectively a Cura CA10 - the cabinets were remaindered when the company went out of business, and it seems they had PL18s and Seas H519 25TFFC tweeters. I managed to get new old stock of both, and I have them set up active with minidsp crossovers. I never found a crossover schematic for them. They've been 'on the bench' for a while but are now back in-system.

I've had a fairly simplistic crossover running on them with a very steep filter at 2.5k but I'm wondering if I could do better.

The tweeter nominally resonates at 1200, has stored energy between 1200 and about twice that, and it rolls off second order with -3db at about 1800 and flat at about 3500, it looks like Q is about 0.5.

I'm wondering if I could:

• use an LT to flatten the tweeter's response and push the natural rolloff down so its flat above about 1000
• then add a 4th order (might try 2nd) LR at about 2300, maybe a bit less.

The PL18 cone geometry means that the 60degree plot diverges from about 1800 and the 30degree plot from about 2500, so I would like to keep the crossover as low as I can given the tweeter's limitations.

Does that sound sensible? I don't think the woofer is up to higher than 2.5k without directivity issues

The 'ears' on the tweeter are next to each other and the cabinet is cut for that rather than the more spaced out terminals on newer tweeters, otherwise I'd probably replace with an SBAcoustics or similar. I may yet take a saw to the cabinet, but I thought I'd try first.

Not sure how I'd approach a passive crossover for these without using the tweeter's rolloff and accepting all the stored energy and raised distortion, but that's not my immediate problem.

I finally finished the extended B1-R2 buffer I have been working on after receiving the chassis and finding the time to do the work.
For those not familiar, the B1-R2 is the Rev 2 version of the Pass B1 single ended buffer re-designed by Papa to work with a bipolar, rather than single ended, supply.

This build is for my office that also uses an ACA-Mini with boards created so it will mount in a more standard chassis with heat sink.

I modified the B1-R2 to use the output buffer pretty much as designed by Papa (Thanks Papa! 🙏) but I also added a few other things I wanted,

This one has an adjustable LM317/337 based power supply w/RCRC front end, a volume pot and a configurable gain stage on the same board.
The AC source is a 24V AC wall transformer connected by a standard 2.1 mm barrel connector.
It is laid out so the gain stage, which uses an LM4562 op-amp, can be omitted or the gain can be easily changed. The gain resistors and the op amp are all socketed and easily changed, bypassed or omitted. Or could be soldered in if no changes are expected.

The pot is an Alps RK27 at 20k Ohms. The next build will use a slightly wider chassis that will function the same but have an additional front panel 1/8" input, an LED power indicator and use a 10k pot with a higher input Z. Using that 20k Pot with 50k input impedance was pretty silly of me. The new build will go in the main rig.

So how does it sound? I think it sounds utterly fantastic! Really open, detailed and dynamic. My office stereo has never sounded this god. It's quite a change, But of course I may have builder's bias. 🙂

I created the board in KiCad. If anyone is interested and wants the design files or Gerbers I'd be happy to share. I can also share the chassis source at AliExpress. Drop me a PM if interested.

Attached is the schematic as built. I have a new rev with tiny improvements not yet built, And it probably never will be built. I ordered the five board minimum for the first build and expect to only build one or two more.



So

I have to share this. Found these beauty’s at two different garage sales last week, got them for $10.00 per pair. The holey basket had one where the surround was separating from the cone and the other was perfect. I have only seen pictures of the black non rib cones holey baskets. The AKAI had surrounds partially separating from the cones. All have good surrounds, not stiff. I have glued the surround on them. What a great find!

I am starting this thread to discuss the construction phase of building an Shigaclone MKII Black CD player / Transport .
I will post photo of building and some modding I will do on this board.

Hi,

I stumbled across the B&C DCM50 in the search for a midrange compression driver. It seems like it has only been used by very few people, but the ones that have used it recommends it highly. It seems to fit well into a 200 Hz tractrix or similar round horn, but any inputs on using it in a Yuichi 290 Hz horn? I have not been able to find the exit angle of the driver to evaluate if it matches the rather narrow throat of the Yuichis.

Recommendations for other horns to fit the DCM50?


Thanks!

Making other projects priority, so letting these go... photos to come.

Pair of NEW IN BOX Faital Pro 15PR400 4 Ohm.
$420 + Shipping

Bohlender Graebener (BG) Neo 3.5.
New old stock $140/pair + Shipping

Three near new Bohlender Graebener (BG) Neo 8, with gaskets.
$75/each + Shipping.

Used pair, but in excellent condition, Seas CA15RLY.
$80/pair + Shipping.

I also have wired up together...
Pair of near new Jantzen Audio 0.40mH 15 AWG Litz Wire Air Core Inductor
$30/pair + shipping

Pair of near new Jantzen Audio 3.3uF 800V Z-Silver Capacitor
$45/pair + shipping

I'll cover PayPal fees.

Open to reasonable offers.

Thanks.

I just read an article written by Intel board members. "Professor Yoffie, Mr. Hundt, Ambassador Barshefsky, and Professor Plummer all served as longtime directors of the Intel board."

I worked for Intel Corp in the late 1980s until 1997. That was when Intel Corp ruled the CPU world- Intel 286, 386, Pentium. New wafer fabs were being built in NM and AZ. Intel Corp was/is highly dependent on corporate welfare. And there was a consortium of taxpayer funded photolithography research going on. It all ended when SVG corp was sold to ASML. I always wondered how a Dutch company could buy a US funded company?

The photolithography tools were the bottleneck because the geometry of the chips were limited by the frequency of light waves. Nanotechnology. In the 1990s, the limiting factor was the placement/position of the photolithograpy tool, but magnetics were used to resolve that resolution. Talk about a gnats ***.

Today, there is talk about TSMC taking over Intel chip factories. Intel Corp might die.

Hi everyone, I am a long time amateur DIY-er in loudspeakers (both kits and self made) and now amplifiers. I have been browsing this forum for years for inspiration and tips, and now that I am starting an amplifier project (class D kit) I will surely need to ask some basic questions along the way 🙂

A few weeks ago I found this random cabinet in a dumpster that somebody alerted me to. It was a pristine farfisa cabinet for a br-80 amp combo. A whopping 80 watts of Italian made germanium-powered instrument amplifier, with a very nice pristine JBL d130 in the cabinet along with a tell Ray oil can Echo unit. I found the actual head unit on reverb in non-functional condition. I bought it and had it mailed to me and got it functioning straight away. A few weeks later I got an actual schematic and went about shoring up any other Loose Ends. I now have the unit as restored as can possibly be, thankfully to my large collection of germanium transistors that I've accumulated over the years. But it still has a rather present 120 Hertz hum, which is entirely from the power unit, as with all of the inputs shorted or even with the input cards removed the home is still there. I realize there is a lot of possible reasons for this. For instance that this was a unit made for 110 volts now getting closer to 120, and the age of the amplifier possibly having some incongruities. I figured there has to be some way to balance the hum, as I have seen on a lot of other amplifiers. I recapped the whole thing, or at least every electrolytic that was in it. I read some post somewhere that said that the Falcon caps that were in these things were usually pretty stable. That's complete nonsense by the way! Any capacitor from 1967 that I know of is in no way stable! Certainly not in an 80 watt monster from this era. There were very few solid state professional amplifiers back then that were 80 Watts. I'm wondering if they were limited by the state of the capacitor technology of the time, or the state of tech in Europe and Italy to be specific. If made nowadays if they would have capacitors with several thousands of microfarads versus the highest being I believe 1,000 or 2,000 in a preamp circuit. I think most of the larger capacitors in the power amp were only about 500 to 1,000. And a lot of those were hooked up in series with others which would make them lower. I'll include a few pictures and a YouTube link and the schematic that I scoured the planet to find! Thanks for all of your help and information in advance, though I know this is kind of a big ask! Also I'm trying to figure out how to turn one of the record heads in the Echo unit into an erase head, as I have heard of erase heads in these, but not being tape oriented I'm not sure what any race head would be!? I don't even know how they bias the record heads on this particular unit beings it is recorded via electrostatic energy and the regenerated Echo is gotten by simply not being erased entirely on the first pass. This unit is also significantly brighter than the others I've heard, and I made it even more so by speeding it up a little bit by increasing the width of the motor Drive pulley.

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So I’m totally new to DIY audio and have yet to do my first speaker build, but I do have experience in building furniture cabinets and thought I’d pass on a few insights into the sheet materials available (as I’m in the UK this is obviously from a UK perspective).

Birch Ply (and it’s lesser sibling, Poplar Ply )

I personally love Birch Ply, or Baltic Ply as it is often referred to. If you’re going to build in Birch ply I personally would leave it on show in all its glory and not paint or veneer it (kind of a waste of money if you do this in my humble opinion). Troels’ speakers for instance all show off Birch ply in all its glory - especially that lovely layered cut edge.

Here in the UK, all of our high grade birch ply came from Russia. With the pandemic and then the Ukraine war this led to a total end to Baltic ply from Russia coming to the UK (some timber merchants doubt it will ever return). At present I am told all of our birch play now comes from Lithuania (it’s not quite as good as the high quality grade that came from Russia, so I am told). It also literally tripled in price over night and it still hasn’t, and is unlikely to ever return to pre-pandemic pricing.

Birch ply comes in many grades, and for the layman in the UK, it can be tricky to find the good stuff (during the pandemic this stuff was gold dust). You will not find it in the big DIY merchants here in the UK - you’ll need to find a specialist timber supplier.

It will come graded like BB/CP or BB/BB etc. For cabinetry you want the highest grade which at my supplier is classed as B/BB ‘unplugged.’ This is the important bit, a lot of so called premium birch ply here in the UK is often ‘plugged’ - this is the process of removing (literally cut out) a defect like a knot in the surface layer of the sheet, and glueing down a replacement patch. The repairs are highly visible and do not look nice and will ruin the look of your build unless you can cut around them - some sheets have multiple plugs which makes this difficult.

I have seen a number of online UK suppliers selling so called ‘premium’ birch ply which is plugged - my advice is read the small print or ask.

As of December 2024, at trade prices you could be looking at £110 per 8’ x 4’ sheet of 18mm ‘plug free’ birch ply. A 24mm sheet would be in the region of £140 (those prices are inclusive of VAT).

As an example, one online retailer is selling an 18mm 8’ x 4’ sheet of ‘plugged’ premium ply for £264!!!

Poplar ply can be found for less money here in the UK, looks like Birch Ply but is made up of fewer layers - not as strong, not as dense, not as nice, and still quite expensive so personally I wouldn’t bother (unless you plan on painting or veneering).

MDF

Again, there are lots of different types of MDF and they aren’t created equally.

Go into any large chain DIY store here in the UK and you will find MDF - it’s brown and comes in different thicknesses and is relatively cheap (compared to birch ply).

This is what we (in the trade) class as trade MDF and it really isn’t designed for making furniture with. Instead, I would look for Moisture Resistant MDF (often referred to as MR MDF). You can tell the difference because this stuff is more green in colour - certainly the inner section will be green in colour. A popular and well known manufacturer is Medite and this will be brown on the outside and have a distinctive green core to it.

Moisture resistant is more dense and cuts really cleanly - it is far superior to ‘trade’ mdf and this is what I would recommend for building furniture (speaker cabinets).

Medite is a brand name, and it’s quite expensive, but there are others that are a little cheaper, like Fibralux - still excellent quality, moisture resistant mdf. It looks a little different to Medite MR in that it is a greenish brown throughout, whilst Medite has a very distinctive green core compared to the brown outer. Medite also do another product called Optima - this is moisture resistant and also even higher density to the MR MDF.

As an example of trade prices here in the UK, 18mm MR Fibralux is in the region of £32 per 8’ x 4’ sheet, 22mm is £44 a sheet and 25mm is £51 per sheet. You can expect to pay more for Medite, and these are trade prices so likely 10% or so more to the public.

If you are planning on painting or veneering your cabinets I would opt for MR MDF or Optima, just note that a cut edge of MDF is easily damaged compared to Birch Ply so you have to be quite careful with it.

If you want coloured throughout MDF then the name banded around most often is Valchromat. I understand that Valchromat actually went out of business some years ago but another company bought the rights to the name and manufuctures the boards themselves under the Valchromat name. It's nice stuff, but it's expensive, very expensive! You can find black throughout MR MDF though from Fibralux though at cheaper cost - it's decent quality and can be sealed/treated much the same as valchromat with a hard wax oil etc to finish.

One of the biggest sheet material businesses here in the UK is a company called Lawcris - thankfully they are based near me but they will deliver (but I think you need to spend at least £300! ) They have an enormous selection of sheet materials in general - from mdf to plywood, from veneered to bendy ply etc so may be useful to someone perhaps.

Hope that helps some builders out there who may or may not be so clued up on the woodworking aspect. Please note I have no affiliation with Medite, Fibralux or Lawcris and these are just branded materials/companies that I am familiar with because I have used them - I'm sure there are others too.

I hope Dave at Planet 10 doesn’t mind that I am posting this question here too. I’m sure he’s busy and I thought maybe others can benefit from the answer to this question and/or share their experiences with similar builds. (Dave, ignore my email lol)

I am building an Em-Ken using a 10” Eminence Beta10cx using plans Dave created for me back in 2021.

Basically, how much dampening is supposed to go into this thing? Dave’s plans say line the walls with 12mm felt and stuff the cabinet with UltraTouch, but all of the newer Fonken/Onken plans say line the walls or stuff the cabinet, not both. So, which is it?

If I did stuff it in addition to lining with felt, how much stuffing? 1lb per cubic foot like standard practice?

The plans say line the holey brace with lower density felt, but does that mean cover the holes? Or line around the holes?

I got the wood cut except for the front baffle as I’m trying to decide if I want dark cedar to offset the light maple cabinet or should I use curly maple veneer on the baffle and keep it all the same color? Hard decisions…lol….

Nothing groundbreaking here. I've started developing a 2A3 SET amp by trying different published circuits, and will use this thread to record information for those who come after and foster discussion for those currently interested. At the moment, I'm trying different topologies from well-known circuits to gain a sense of what the general behavior and sound characteristics are like. Once I discover a favorite, I'll either just do a final build or tweak it to taste.

The order of progression will be as follows. For now I'm sticking to cap- and direct-coupled designs because I don't want the expense of an interstage transformer. I might add more circuits to this if I feel like it.

1. JE Labs simple 2A3
2. JE Labs SRPP 6SL7- 2A3
3. 5842 - 2A3
4. Radiotron 6C6 - 2A3
5. Lipman direct-coupled 6SF5 - 2A3

So far I've done # 1-3. The attached LTSpice screenshots show operating parameters that are fairly close to the actual breadboard conditions. In all cases I elected to run the output stage at the traditional 250Vak/60mA with a 750R cathode resistor, even when it differed from the published schematic (i.e. some use an 880R resistor and about 270Vak/55mA, and some even exceed the 15W maximum rating of the 2A3 plate, which I didn't want to do).

1. Joseph Esmilla's simple 45/2A3 circuit, which uses 1/2 6SL7 per channel as a simple voltage amp. I was surprised by how enjoyable this circuit is to listen to. Gorgeous and highly developed timbre on acoustic instruments, fast, dynamic, very detailed, and very musical. Jazz guitar and small ensemble classical like Ravel and Stravinski were excellent.

2. Joseph Esmilla's SRPP 6SL7 - 2A3. I ran the output stage at 250Vak/60mA and made sure to elevate the 6SL7 heater voltage with the power supply divider and 6.3V winding center tap as in Joseph's schematic, so as not to exceed the heater-cathode limit in the 6SL7 datasheet (the upper triode cathode is at nearly 150V). This circuit was "better" than the simple version in the technical sense that it provided even more detail and noticeably greater bass extension (not that it was lacking in the simple version). It's perhaps a little more neutral and polite than the simple 2A3, but still develops all the layered timbre and dynamism. I could live with either circuit and was very happy with both, maybe with a slight preference for the simple. If I swing back in this direction I'll try both again.

3. Self-designed 5842 voltage amp into a 2A3. Given that the 6SL7 runs at very low current in the above schematics (about 0.6mA), wanted to hear what would happen in an arrangement with more current driving the 2A3. So, I picked 5842 and attempted to run it at its published op point of 150Vak/25mA, using a 60R cathode resistor and a 6K plate load resistor with a supply voltage of 300V. In the load lines I layed out, this one (red line in the attached screenshot) seemed the most linear. When I first switched on the breadboard, using the same rectifier (5R4GY) and power supply as in # 1 & 2, the voltage was expectedly lower than before (5842 at 125Vak). So I swapped in a 5U4GB and now the 5842 is at 130V/24mA (the light purple line in the attached screenshot). This arrangement is not bad but sounds a bit lackluster, without quite the timbre, detail, and dynamism of the 6SL7 circuits and a less perceptible soundstage. It's also a little grainy. I might switch in a GZ34 to see if the 5842 gets up to 150Vak and sounds different. Then I'll try lowering the 5842 current to 10mA or so to see if the sound gets more dynamic. But at this point I'm more inclined to move on to the 6C6 circuit, which appears to be an answer to the WE91A.

One thing I need to do is learn how to calculate the amount of current needed to drive the following stage without slewing problems. I think Gordon Rankin demonstrates that in his Bugle 45 article in Sound Practices.

Hello

Currently I am trying to design and build prototypes similar to danley BC218, divided in half for easier transport and multiple possible deployment configurations. I will be using 18SW115 8ohm version as i already own them and it seems Danley also uses them a lot in his designs. My goal is not to make a identical copy of his design but to make a sub with similar preformance and same design benefits. Aiming for same dimensions and about same frequency response (-3db@ 28hz).

I've been following @weltersys folding prediction and made a 3d model, but 18SW115 sadly doesnt fit and i am not exactly sure how to model in hornersp with decent accuracy.

I am relatively skilled in Solidworks, Catia and cabinet building (designed and built my own version of TH118 and 4 way synergy horn), but lack experience for simulating such advanced horn sub.
Any help would be appreciated, as i said looking forward do design 3d model first from usable simulations, then build 2 or 4 prototypes - I have a huge free area near my house and I will keep this thread updated with build progress and measurements.

Looking for support in simulating this folding or exploring possible different horn foldings

Attaching picture of a very rough model

I read somewhere that Sanken transistors are specifically designed for audio applications but they're difficult to acquire (Japan only mostly, and some fakes on AliExpress which I won't touch).

Are there any other BJT transistors recommended for the output stage of an audio amplifier?

Hi all,

I'm desperately trying to find service manual/schematic of the JEDIA L2.2 / JD-MEDIA LX2.2 / R.C.S. LX2.2 power amp. I asked to the manufacturer but they didn't respond yet. Have you any suggestions to find service manual of this particular amp please?

I need to figure out input stage topology because this amp seems much more prone to the interference comparing the other amps that I have dealt with. I'm also trying to figure out purpose and equivalent schematic of the HIC-VOLT21 proprietary daughter board/module at the input stage.

Thanks in advance.

Paul Voigt was an audio pioneer, who left a legacy of patents that is fundamental to high quality reproduction today. One of his classic achievements is the Voigt Domestic Corner Horn.

While I think it is probably more famous, it is actually a domestic adaptation of his Voigt Tractrix cinema horn. That was a square tractrix horn with probably a fullsize hornmouth for the calculated cutoff frequency. The domestic cornerhorn is intended to be placed in a corner, and has the horn pointing up. Because of the boundary loading, it has a smaller hornmouth and because the horn is pointing up, it also doesn’t stick out into the room as much. It is the smallest way to make a large frontloaded horn. Voigt added/integrated a quarter wave pipe to add bass to his fronthorn design.

While the big Western Electric Cinema horns are quite different (because they use a compression driver, a lot more length etc), the corner horns are similar in having a wide range and having a large mouth area.

I think anyone who has ever played around with building frontloaded horns for fullrange driver has probably experienced that bigger fronthorns have a more dynamic sound and a larger scale. There are of course also downsides, for instance that large horns beam a lot. Voigt solved this by adding an elaborate reflector to his horns. Instead of a simple 45 degree reflector or a single curve, he has a double curve reflector.

During and after World War II, materials for these loudspeakers were in short supply in England, and Voigt created a simplified cabinet design that could be made with fewer materials and made by consumers themselves. It was called the Voigt Home Constructors’Corner Horn. I am not entirely certain, but I think they are the same in terms of horn parameters, just laid out to use materials a bit more efficiently and to reduce complexity for the homebuilder.The reflector is now reduced to a single curve. I have actually seen photos of a version by a DIY-er that had added a reflector from the earlier model.

Due to its elegant simplicity, I believe the Home Constructor’s Horn is an ideal horn for DIY-ers that want to make ridiculously low frontloading horns for their fullrange drivers. We should/could basically use the existing plans to make our own horns for our drivers and requirements. However, it really helps when we know the horn parameters and can use them for simulations in software like hornresp or other software options. That way we can select suitable drivers, or adjust/scale the horn design to our drivers of choice.

So what we really need, is to understand and intimately know the horn. In this thread, I intend to ask questions and use some of your conscious and unconscious knowledge to assemble the best model and understanding of the Home Constructors’ Horn.

Hi everyone!

I'm new to diyAudio and just getting into speaker building. I recently started my first big DIY speaker project because I wanted a good bluetooth speaker and figured I'd just build one myself.

For the main speaker, I’m using the Dayton TCP115-4 woofer and the ND25FW-4 tweeter. For the EQ and Crossover I'm using an ADAU1452 DSP. I also added a 128x128 OLED display with an ESP32 and a rotary encoder for controlling things like volume, source selection, bass boost, etc.

Since I like bass, I also built a wireless subwoofer using the GRS 8SW-4HE-8 driver. Both the main speaker and sub sound great, but I’m running into one big issue: port noise.

I was aware of chuffing as a problem before building and tried to keep air velocity below 20 m/s peak using WinISD, but in practice, especially on the sub, the ports are just too noisy. That’s why I signed up here, hoping to get some advice on where I may have gone wrong.

I’ll post more details about the sub in the subwoofer section soon. I'm looking forward to getting some advice on where I went wrong.

This is the layout of the input section of a PA amplifier I have. The Positive input is grounded to pin #3 of the balanced input connector. I'd like to change it to a single ended input because I don't have anything balanced and don't plan to. Is that something thats easily possible?

This short video showed up in my YouTube feed. Good interview with various people, a few of them having been with Nelson since Threshold. Quite clear that Nelson has created a great environment to work in.

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With the age became a tube guy, hence sell this diy clone. Not my build so can't respond your smart questions except to post pictures. I recapped it 3 months ago, you know temperature ages fast.
I price it 750eur thinking it's fair but maybe I am wrong? That case just make me your offer and I might accept it. Shipping to Europe only. It's a heavvy beast, cost of packing will not be cheap side.

Lately I have become curious about the DS Audio optical pickups and I think sooner or later I will get me one.
They are a bit pricey, but it's possible to purchase a DS-pickup without the equalizer, so DIYing the equalizer safes a fair amount of money.
Here I just want to gather some ideas on the construction of such an equalizer…

There is a pdf "Optical cartridge technical info" which can be downloaded on the DS website https://ds-audio-w.biz/products_info/
I've got all my information from there.

PSU requirements


The pickup consists of an IR-LED (one for both channel for the 2nd generation pickups and one each channel for the 3rd generation pickups) which needs to be powered
and two photo-diodes -one each channel- which need an negative bias voltage.
An LED (the “front light”) is in parallel to the IR-LED and seems to be an on-indicator without further purpose.

The IR-LED is powered from 8V via 68Ohm resistor. Diode Current is said to be 65mA for the DSE-1 and 80mA for the DS003.
There is a resistor in front of the IR-diode shown in the pdf, which probably serves to decouple the IR-LED from the indicator LED.
So the IR-LEDs forward voltage is likely to be approx. 2,9V.
The Photo-Diodes are reverse biased (photoconductive mode) and need a -10V bias voltage each channel.

Output voltage of the DS-E1 pickup is said to be 50mV. The schematic has a 16kOhm resistors to convert the diode output current to a voltage.
Diode-current therefore must be 50mV/16kOhm=3,125µA (5cms/sec at 1kHz???)

In the DS Audio pdf the RIAA equalization is shown as a passive network right behind the 16kOhm resistor.
I’m not shure if this is the optimal position. Also the I-V-conversion could benefit from an active solution.

In the following schematic I use a transimpedance amplifier to transform the current to a voltage.
I “lifted” the output of the TIA to -10V by putting this voltage on the non-inverting input- which in turn sets the bias for the photo-diodes.
This reduces the headroom of the Opamp. One solution could be, to make the Opamp supply asymmetrical: +5 to -25V.
The following capacitor removes DC from the signal and can be part of the succeeding equilazation-network (can we call this still a RIAA-network?).
The channels are phase inverted to each other, so the right channel still needs an inverter stage.



Any comments so far?

Cheers, Boris

A viewer sent me this made in China "Little bear" phono stage to look at, and out of the box it was nothing special. But with some simple mods, it really sounds quite good.

The main issues IMHO were the coupling caps were the wrong sizes: stage 1-2 was a 0.1uf which is fine, stage 2-3 was a .47uf which only needs to be a 0.1uf, and the output cap was a .47uf which needs to be a 1.0uf. The output cap change in particular resolves the low bass output this pre-amp had. I used Mundorf Alum/oil but if you are on a budget, other types could be used. I have a feeling the supplied "Wima" film caps are fakes and I would replace even the correct size 0.1uf first stage cap while I was in there.

The China 12AX7 tubes it came with were noisy and lifeless. Some new production Mullard 12AX7 gave it some life but were still noisy. Ended up with some EH7025 tubes, which massively reduced the noise yet kept the spunky sound of the Mullard 12AX7 tubes.

They also have 62K resistors for the cart loading/input caps which should be 47K for the vast majority of MM phono carts out there. And finally I swapped the ceramic caps in the feedback loop for high precision mica caps, which made a very audible difference! I also did a bit of lead dress while I had it open.

At the end, this is a nice sounding little pre-amp for a small amount of work. I still think my EAR834 clone sounds better, but if you already own one of these, it's worth doing these upgrades to it.

Here some videos on this phono pre:

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The appearance of 2.5- and 3-way speakers look similar, actually identical for some designs. Suppose they both have 3 drivers per cabinet for the same; a tweeter, a midrange, and a woofer. The difference that I could realize is the presence of the “high-pass filter” for the midrange. That means the 2.5 ways will allow its midrange to simultaneously play woofer’s frequency. By the way, I couldn’t think of the benefits of the 2.5 ways except for economic purpose. Furthermore, it may yield inferior quality to the 3 ways as the midrange driver will play mid-frequency based on low-frequency waves. I’m not sure if it could be viewed as the midrange in the leaked box, couldn’t it? So anyone please tell me what’s the benefit of 2.5 ways speakers over 3 ways?

Make offer in thread and how many you want.
I think these are used mostly as power switches, no?

Marquardt SWITCHES 250V 2A 4-pole device switch off switch Toggle LUND -- NH USA --

There is a new rave review of home speakers using 1.4" TexTreme CD, Oaudio Icon-12. Only candidates seem to be FaitalPro HF1460 and Eminence N314X, with the former at double the price at $730/each. Any experience with either one? (Rooting for cheaper one to be as good...)
BTW, anyone recognize the horn or the 12" driver used in that speaker? Hoping for DIY/oem alternatives.

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Hi all! I was asked to create this topic as one of the authors of the acoustic design of subwoofers, which was called PPD (Petrenko Petrushevsky's Dipole). In fact, this design, in our opinion, is an improved version of the traditional ripole by Axel Ridtahler. Its main advantage compared to the Axel rippole is the absence of significant unevenness in the frequency response in the region of 150-300 Hz. Additional benefits are lower overall distortion in the subwoofer's operating range and smaller dimensions. With the right choice of TSP speaker parameters, very good results can be obtained, since the smooth frequency response allows the use of second-order filters.
In this video, an example of using a PPD subwoofer on a 15-inch speaker in triphonics.

I am going back to the beginning and building the Radiotron 2A3 single-ended amp. I plan to start with the original and work from there listening as I go. My first mod will be taking the bypass caps to 100uf and the coupling cap to 0.22uf. My question regards the resistor values which are given as what looks like .25, .5, and 1,5. I assume those values are in mega-ohms, correct?



Happy listening,

John

I am working on this power supply PCB. It's double layer, 2.5 mm thick, and pretty much cooked to a crisp after decades in an inadequately ventilated case.





First cap that I desoldered, I ripped a trace off the top side of the PCB. I figured the solder wick method wasn't going to cut it this time, so, not wanting to cause more damage, I ordered a Hakko FM-301 tool which I had been wanting anyway (it's a fantastic tool, by the way).

Second cap I desoldered (with the Hakko this time)... I ripped a trace off the board again. But I noticed that the trace was pulled up by a repair eyelet that was stuck to the cap pin. Then I saw that the exact same thing happened with the first cap.

Next I desoldered the DB9 power connector, and 9 out of 9 pins came out with an eyelet attached. I realized the eyelets were on the pins pretty tight, and that they were being pulled up not necessarily by leftover solder but by mechanical friction.

Now, I'm pretty sure those Roedensteins and DB9 connector I pulled out are original, yet every single hole had an eyelet in it, so it looks like the factory built the PCBs that way instead of plating the through holes? Isn't that unusual?

Anyway it is what it is, and I have to deal with it. These eyelets and pads are incredibly fragile, so the less work the better. But, seeing how baked this thing is I think it's reasonable to do a full recap, test all components, put fresh thermal grease on the transistors, etc.

Where I have access both top and bottom sides I can apply heat to both sides at the same time, so I think pulling out diodes, transistors and resistors without breaking anything else will be OK.

Not sure what to do about the caps though. They're mounted flush with the PCB, so there's no room to cut the pins off. Maybe I can just tear them apart to expose the top of the pins

The PCB traces are .35 mm thick and they are super strong, so it shouldn't be too hard to epoxy them back down. Then I can replace all the eyelets and pads. Which will leave me with a severely cooked board that looks like absolute crap, but at least it will be in better shape than now.

I also thought up two other (creative!) ways out of this mess:

• Have the PCB cloned by one of those shops in China
• Toss the PCB and rewire the thing point-to-point

I don't know what else is there? What would you guys do??

Thanks in advance, all thoughts are welcome! 🙂

Due to a clerical error on my part, I now have 4 pairs of 2 way monitors going spare. Wharfedale delta 30.2, mordaunt short ms20, mission 731 and 732.

In my house, I like to have two systems. One for the office, and a surround sound for the TV (got a standard 2 channel amp for the office, and a 5.1 avr for the TV, I'd upgrade to 7.1, but I'm really not sure if it's a good idea for the space).

Originally, with a spare amp too, I was going to give away one pair, keep one pair (most likely the 732s), and sell the other two, but I was tinkering with some of them the other day, and I was really enjoying the difference in the characteristics. I won't say they're all on the same tier exactly, but they're not that far apart, and I do enjoy the variety, even if they're not crazy different.

Recently, I bought this pair of custom speakers. Way cheaper than they should have been, and absolutely massive. I think the previous owners liked them for parties, and I got a horrible overpowered amp for the asking price thrown in for free. Thankfully, it plays nice with the avr, and the added depth it gives the sound at not insane volumes (I like my neighbour, and it's a semi detached, what can you do) is very nice.

It had me thinking "how hard could it possibly be to whack some MDF together, do maybe 5-10 minutes of soldering, and unscrew drivers for transplanting".

I did do a little research, and the advice seemed to be "why would you do this", but I guess I'm just after answers with my specific set up.

My current thinking was:

1) don't mess with the 732s. They're nice, I like them, perfect for the office. Keep those as is (once I've repaired a tweeter).

2) give away the 731s + amp. It's getting a bit silly having this many unused cabinets lying around.

3) unholy Frankenstein combination of what, iirc are some wharfedale lasers (please don't make me walk downstairs to find out which) I'm using for rear surrounds in the TV set up, the mordaunt short ms20s, and the delta 30.2s into a disgusting mttmm or mtmm floor standing speaker, then flog the unused parts on the bay. Potentially add a woofer for fun too, then use them for my rear surrounds in the 5.1 set up.

What I want to know, is on a scale of 1 to 10, 1 being bad, and 10 being good:

1) how good/bad could it sound
2) how much will I regret my decision on this as a project
3) chances of success? (Part time tinkerer + audio refurbish and repair. I won't say what I achieved is aesthetically pleasing, but I also won't say I care, or that it doesn't function)

Answering a few of your questions in advance:

-this is a waste of time. If you want floor standing speakers, why not buy a kit, or just get some off eBay?

For the same reason that god made grapes but not wine, and milk but not cheese, so that we might share in the divine act of taking something cool and making something stupid but tasty

-why not sell the speakers that you have, and get more sensible drivers at the very least?

I'm emotionally attached to some of them.

-that doesn't explain why you're okay chopping them up for parts... How about this, why not sell two pairs and your avr, upgrade to 7.1, and then you get to keep more of them?

For 1, the room is already pretty unbalanced to begin with, and it'd be too big of a job sorting that out, and for 2, it really is a space thing at the end of the day. The spots where the surrounds are at the minute could go up to the ceiling, but it'd be a bad idea to remove square footage.

-interesting... Sounds like that's quite a small room, why do you want such big speakers then?

Mind your own business. For reals, depth of sound, clarity, quality e.t.c. I'm not here to blast my, or anyone else's ears off, but I do like nice sound. Also, I can see myself moving in the not too distant future. While I'm not above paying silly money for larger removal vehicles, or doing some to-ing and fro-ing myself, I anticipate my views on sound aren't going to change anytime soon.


Also, fyi, I will be looking into wiring kits, I think whatever configuration I end up doing won't really lend itself to reusing any of the existing ones.

I would like some help about some good modifications on a hafler 120 power amp .🙂

Hi there. My name is Gena. I am and embedded engineer from Belarus. Previously, most of the time, i was developing software for uCs, but recently i changed the job and became a hardware developer as well. My current project includes audio data converting/transiving and would like to get some help from more expirienced embedders.

Hope to have some good time here, and wish you all the same <3