For sale, Focusrite 18i20 2nd gen in like new condition, $260 shipped to continental US.

I've used this less than 10 hours since purchasing directly from Focusrite in November 2021. Comes in original packaging with USB cable and power cord.

Relevant specs can be found here -> https://store.focusrite.com/en-gb/c...rlett-18i20-2nd-gen/MOSC0015UKEU~MOSC0015UKEU. Brief summary of I/O shown below.

Supported Sample Rates
44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz at 24 bit

Inputs
8 ch analog, XLR / TRS combo jacks
ADAT (8 ch at 44.1/48 kHz or 4 ch at 88.2/96 kHz)
coaxial SPDIF
MIDI
asynchronous USB

Outputs
10 ch analog, TRS
ADAT (8 ch at 44.1/48 kHz or 4 ch at 88.2/96 kHz)
2 headphone outputs w/ independent volume control
MIDI
coaxial SPDIF
word clock

This interface is a good option for computer based DSP systems as it is USB class compliant (works perfectly on Linux) and knob on front panel can be used to control volume of all analog output channels. ADAT output also gives option of doing a large amount of output channels with a second interface.

Michael

For sale are 3 pair of Mark Audio Drivers:

-SOLD Alpair 7MS gray cone pair, unused, with all packaging, mounting screws and gaskets. 12 x 6 x 4 inch box, 6 lb. SOLD

-SOLD Alpair 11MS gold cone pair, lightly used, all packaging except original mounting gaskets. 10 x 10 x 10 inch box, 11 lb. SOLD

-SOLD CHN 110 silver cone pair, new, unused, all packaging, mounting screws and gaskets. 10 x 10 x 10 inch box, 10 lb. $85 $70 or best offer, plus shipping. SOLD

I will ship USPS or UPS to continental USA only.

SOLD 7/06/2022. Has been setting in my closet for many years. Need some direction as to value today. Looks totally untouched.

I have a thin mini-itx based Windows 10 media PC that I built. aS part of the build I installed an IR remote control for Media Player. At first I used the audio outputs from the (Asus) mobo. The remote function (using an HP remote handset) worked as intended with Media Player, Kodi, Skype etc.

I then decided to experiment with using an outboard DAC. So I bought a Twisted Pear "USB Receiver/DAC" http://www.twistedpearaudio.com/digital/usb.aspx . The remote control functions still worked as intended when I used the audio outputs from the DAC Receiver board.

I then connected the coax SPDIF output from the TP USB Receiver/DAC to a separate DAC. The SQ improved but the remote control will no longer control the volume or mute functions. It will however, still stop/pause/skip tracks.

I don't understand why this should be. Surely the USB output from the PC is the same no matter what DAC is connected. The remote handset is not at fault as I have two and both behave the same.

Can anyone shed any light on why this should be happening? Thanks.

Hi all,

I got completely dead Evo 200.2 (rev E 5/1/00), make it work (big 6 caps are new) to the point that all voltage are as expected +/- 46.7v, +5v, +/-15v, blue led on, red (protection) on then turn off few seconds later, and red stay off, but no sound at all with RCA input, also not hearing any sound on speakers, no AC/DC on speakers, also cannot hear any relay click - could be they do not produce click at all - little strange.
Looks like nothing else is changed at all. Also notice all three blue 100uf/35v and two gold 100uf/50v are heater than others (around 15 regulators)
Any suggestions, please ?

Hello. My mark Levinson 532H power amp stop working two months ago. No led tun on. The board this dead. My unit is on a oficial harman luxury repair shop official distribuidor in my country waiting for the answer from harman to give me price the part but until now without answer...

So I am trying to make this more faster and looking for the board.

Maybe someone can help me to get this (photo attachment)

Thanks for any help 🙂

I used to have grand plans for a Adire Audio Shiva, but I'm starting to get the perception that it wasnt really intended for home theater. Although I do like the price tag.

Does anyone have recommendations to some top of the line woofers? Size is no object, really. Oddly enough, bigger is better to many extents. Needs to cover 20 hz decently, provide at least a minimum amount of kick. Something to that serves to the weaknesses of two 21W8555-01's 0.5 Q box.

Oh, and what are acoustic's golden ratios again (just need the #'s)?

Applies for both sealed and ported?

In my setup, I have 2 pairs of woofers and a tweeter. I have previously plugged these drivers into the Pam8610. But the problem with it was the Pam8610 has too much noise/hissing sound, I tried many ways to fix the problem but nothing changed. I decided to switch up to a fully filtered amp board. My question is between the TPA3110 and TPA3118 which one is best for my setup and can I power my setup with 8.4v battery?

I'm a newbie in this area btw.
Thanks all,


My setup detail :

x2 Tweeter: 8ohm, 20w
x2 Woofer: 4ohm, 20-30w
x2 capacitor: 100v - 3.3uf (for the tweeter)
x1 QCC3031 Module: it has its own amplifier: tpa6132a2

Hi folks,

I’m on the waiting list for a QA403 but seems like it will be months. Just wondering if anyone is selling their QA401 or newer model?

UK based, but will pay of international shipping.

Dan

Hello.
NAD T748 V1 Amplifier.

Turns on and immediately turns off after 3 seconds.Only NAD T748 on display.
Please let me know how protect mode works on this amp?
it's very difficult access to power transistors and and before that, I would like to understand what signal comes on MCU in order to turn it off.
Where should voltage be measured?

REGARDS
SM
https://www.manualslib.com/manual/2171370/Nad-T748.html

hello. when i plug in my minidsp 2x4hd one chip instantly ignites. here's a pic, the chip in question is the small square one the arrow is pointing at. anyone know what it is?



cheers

How do you sell used tubes without a tube tester to be able to include some claim of their current condition?

I have 3 phase power at my house, on a 20 A breaker.
Yes, that's a ridiculous amount of power for an audio system.
But it does mean I don't have to have any 'bulk' capacitors because I don't have to store power to cover the zero volt crossover of a one phase system.
That would save quite a bit of money and improve reliability, one minor inconvenience is the connector.
A conventional amp can use an ordinary IEC socket to have a removable power cord but there appears to be no equivalent in 3 phase.
The standard 3 phase connectors are the size of beer bottles, and not even stubbies.
Anyone know a smaller connector that meets standards?
Or am I stuck with a non removable cable?

David

In a bid to teach myself about amplifier circuits, I wanted to simulate the Rotel RB850. My intent is to understand classic amplifier principles, not explore the detailed performance of the RB850.

The schematic is available in the service manual, and it appears to be a near textbook class AB implementation, with differential input stage, current source for the bias chain, and paralleled output transistors, all driven off twin plus/minus power rails.

(link to service manual)


And...


It turns out that virtually none of the transistors in it have Spice models available. 🙁

The list is:
pnp 2sa1016
pnp 2sb631
npn 2sd600
npn 2sc1941
npn 2sd1047
pnp 2sb817

OTOH, I have (easily) found data sheets for them all.

Should I:

A) Look for equivalent devices that DO have Spice models?
B) Create my own "rough" Spice models using parameters from the Sheets
C) Simulate another amplifier?


BugBear

Hello.
NAD T748 V1 Amplifier.

Turns on and immediately turns off after 3 seconds.Only NAD T748 on display.

Login to view embedded media

Please let me know how protect mode works on this amp?
it's very difficult access to power transistors and before that, I would like to understand what signal comes on MCU in order to turn it off.
Where should voltage be measured?

REGARDS
SM
https://www.manualslib.com/manual/2171370/Nad-T748.html

These diy cabinets with fostex drivers are avalaible to buy locally. Does anyone here know what design these were based on? What is the idea behind the dual full range drivers?

Here, Altec reseller had the possibility of using brand as he wanted. Some speakers was mounted in differents cabinet then US or even new systems were born.

Today I'm restauring a system made for radio-broadcasting. 6417RFE Is a two ways with a Altec 417 and a T-50

Last owner made a "re-styling" mod using flightcase profile. The result have no name ! But something is good : speakers are in good health.

First, I will take off carpet and glue, fill holes (rivets), sand wood and fix leatherette.

Any advice ?

I have been offered a great deal on a Helix DSP M Six ($750). I have a 2019 Kia Sorento, I've got type r comp and coax 6.5s + 1 inch tweeter ( front and rear). I don't have a sub installed but do have 2 12s, going to downsize to one (too hard to move the box).
I have a NVX 1100 (4x80@4 ohm, 1x600@1ohm).

Perhaps I'm wrong but I feel I'm going to need a few things:

1. Better speakers
2. Get the DSP tuned
3. A mono block (that's fine, no big deal)
4. Deaden the doors (planned already).

The issue I'm concerned with is the better speakers. Also the tuning. I don't know anything about sound theory.

Am I overthinking this or should I stick with what I have for now? If I should proceed, could use some recommendations for speakers if you feel that's needed (probably just front).

SOLD

Asking $25 including ground shipping to the Continental USA

I had previously built up a generic +/- 15 volt regulated supply, but do not need it any longer. It was used for maybe a couple hundred hours, no issues.

I will include the circuit as built on protoboard, the schematic as shown, and an Antek AS-0515 transformer with shortened leads. It was used for around 100mA load, and I cannot remember the calculations about how much more could be had with the heatsinks used.

Does anyone know what happened to ESRC’s inventory? I paid the owner right before he passed away for some tubes flying in from overseas. Not upset but would like those tubes even though I’ll have to pay again.

Pair Of New Old Stock Unused Black Gate FK 10,000uF 63V
Price for Pair £700 Plus Shipping. Pics on request

Selling 2 pairs of output transformers:

- 125GSE £95 biggest of 125 series - 100mA and can be set from 2.5K to 10K

- Assumed 1627SE/SEA. £210 Taken out of a nice 2a3 amp made by Phil at Bluebell and virtually unused. No label

Size and weight is identical to 1627SE and so is primary DCR of around 77 ohms. Makes sense with a 2a3.

However there no UL blue wire. Plus there are other models of the same size it could "theoretically" be. But works with 2a3 fine.

Phil was a Hammond dealer so these may have been special orders. Postage at cost. These are heavy and insurance needs to be added.

I just wanted to get any comments, thoughts, questions, about distortion measurements, because I'm new to this.

I built two pairs of very similar MTM floorstanders, in identical enclosures:

• RS180 metal cone, Seas TDFC tweeter, Fc 1.5KHz, 6th order slopes
• RS180P paper cone, Vifa XT25TG30 double ring radiator, Fc 2.2KHz, 4th order slopes

Both have 30-litre bass reflex enclosures, the port lengths are a bit different.
I wanted to see how different they'd sound.

Anyway, my question is about the distortion measurements I did. I put my calibrated EMM6 mic on-axis, 36" from the tweeter centre, hooked up my Focusrite Scarlett 2i2 v2 audio interface, and did some distortion measurements, first with ARTA STEPS (stepped sine) then with ARTA itself (swept sine).

Here they are:

Asawari 5: metal cone and Seas tweeter: stepped sine


Asawari 5: metal cone and Seas tweeter: swept sine


Asawari 4: paper cone and Vifa tweeter: stepped sine


Asawari 4: paper cone and Vifa tweeter: swept sine


My mic is not calibrated to any specific SPL, so the SPL values on the Y axes are not absolute.

What do you think? Are these graphs useful? Can they be improved? I really wish ARTA had the ability to smooth the STEPS distortion graphs, or even average them over multiple recordings.

Hey everyone. I'm looking to eliminate so much cable swapping and just go to switching. Basically I'll have 3 sources that I want to be able to feed into three different preamps/amp combos. Then be able to choose two different sets of speakers between the three amps. All sources, preamps, and amps will be powered on individually. so only one source, one preamp, nd one amp at a time will be powered. No bi-amping or anything like that. I'm assuming I need to add some 10W/8R load resistors at the speaker selector for the tube amp (just in case protection). I have some relay based input selector boards, but nothing for speaker level. Any suggestions?

Basically looking to do this:

Short Version of Providence: Bought this scope at the Grand Rapids Community College Physics Department Garage Sale in 1993ish for 15 bucks. I am sure they bought it new, and at the time we had much newer scopes than this, so it probably hadn't been used in twenty years. From there I used it exactly twice, then it sat under the basement stairs at my moms house until 2017, at which point I moved it to my basement. It worked fine the last time I turned it on in 1994. I have not tried recently.

I had always thought I would use this someday, especially now that I have picked up this electronics habit, oops, I mean hobby. Knowing what I know now, it seems like a mountainous project. I have been restoring an old McIntosh tube amp recently and I see a bunch of the same issues here. There are about a half dozen tall can capacitors in the power supply that I am sure are all dried up. I am not sure how I would even go about replacing them since I haven't had any luck on a service manual to tell me the values (Radio museum has five pages but not even close to the whole thing). It has a half dozen bumble bee caps in it, and half of them are cracked. I spotted what look to be multiple selenium rectifiers all over it. And the tubes - There are like 30 of them in here. Only one was cracked, but replacement tubes for this monster would cost more than a decent used modern-ish scope.

I guess I am wondering - is restoring stuff like this even a thing? I am thinking about just grabbing all the great vintage tubes out of it and calling it a day. I was shocked to see a half dozen Telefunken 12AU7s in at as well as a few 12AT7s too (labeled HP but probably made by someone else).

Thank you.

-Geoff

I'm trying to decide between two compression drivers. I'm not looking for max SPL comparison, but sound quality.

Shootout is between B&C DE780TN and Beyma CD14ND.
My experience so far shows me that I don't like the sound of Ti diaphragms, so I'm specifically looking for that effortless HF reproduction with fast transients and no metallic fatiguing hiss/harshness.

B&C DE780TN (Ti diaphragm)
https://audioxpress.com/article/test-bench-b-c-speakers-de780tn-8-compression-driver

Beyma CD14ND (proprietary PM4 polymer diaphragm)
smaller 1" exit brother tested here:
https://audioxpress.com/article/test-bench-beyma-cd-11nd-compression-driver-and-td-194-horn

So I would expect the CD14ND to have a cleaner waterfall graph. But comparing the DE780TN with the CD11ND I'm slightly confused to see that the Beyma seems to have more HF resonances (around 9kHz and 15kHz) than the B&C (around 15kHz and 17kHz). Overall the decay time is longer for B&C though.
What's to be concluded from that?
Does anybody have some experience with a Ti compression driver that is not fatiguing?
Am I being too dismissive of Ti diaphragms?

Hey,
I own a pair of Tannoy 402 Studio monitors and i was wondering, is it possible to buy a subwoofer(the monitors cant go low enogh), and some electronics to make a portable speaker out of them?

If yes, i would appritiate if some1 could tell me what commponents to look for that will work with the drivers my monitors has in them.

Here arew the monitors specs: https://www.sweetwater.com/store/detail/Reveal402--tannoy-reveal-402-4-inch-powered-studio-monitor

thanks!

Sony originally used oilites/sintered bronze bearings in most of their turntables,the TTS-8000 is no exception.
2 oilites are used along with a nylon? spacer.





The merits of using Lignum Vitae for bearings are well documented, see here, https://www.google.com/search?client=firefox-b-d&q=lignum+vitae+bearings
I have heard Torlon bearings in the past and they greatly reduced any noise coming from the spindle/bearing surfaces,my train of thought was LV bearings could also be an
improvemnet.

So a few bids on ebay and i won a couple of old lawn bowling balls,i cut them up into 25mm square pieces and selected the best grain orientation to experiment with.



I turned and fitted 4 pairs before working out which working method produced the best tolerance, the spindle measures 10.98mm so an 11mm H7 reamer was used
to finish the bearings.

Bearing housing with bearing fitted and being trued up after initial drilling.



Top bearing fitted.



Whilst i was at it i also made a LV thrust pad to go with the bearings,the Sony one was Nylon.



The new LV one.



So thats it,job done,like the torlon bearings the LV ones have reduced the overall noise floor over the standard bronze bearings.The question left is which sounds better
Lignum Vitae or Torlon? My plan is to use the LV for a few months to bed in and then turn some torlon ones for comparison. 🙂

Hi everyone,
I designed this version of the instrumentation amplifier as a line input, but these values should give a gain of 60 (around 35dB) cause I initially wanted to use it as a microphone preamp input section. If I want to use it as a regular line input, should I give it unity gain? 2? 4? Also I added two bypass caps (C5 and C6) in between each rail and the 0V (power ground). Do I need another set of these for each IC or is this enough? Do I need a 47uF electrolytic decoupling cap from rail to rail like you might do in a single supply circuit? Will I need to hook up the power (0V) and signal (GND) grounds together? (The PSU will be on another board)

I want to rebuild my crossover, I would like to remove all the parts from the current board, and start over. Rubbing alcohol is supposed to be good for removing hot glue, will it damage any of the crossover components? Some of my current components I want to reuse. I can just tear them off, but that doesn't look great.

Does anyone have any schematics of some 304tl se amps?


Just looking for ideas?


Thanks,
Nick

So I came across the attached schematic listed below here on diy, but would like to use a cheaper driver than the EML-20B ($500). I have ordered the 304tl's, 3b28's and their sockets. Heyboer will be making the output transformers.. From reading it appears that a 6sn7 may be an acceptable replacement for the 20b but I am not confident in properly sizing the components to make this a simple replacement.. particularly the chokes and capacitors.. I am open to other driver stage candidates if a better suited tube exists. Any gurus here that can assist?

EML-20A-20B-30A Data sheet. By Emission Labs.
http://www.radiostation.ru/tubes/6SN7.pdf

http://www.diyaudio.com/forums/tubes-valves/94663-304tl-based-class.html

WTB - working Single Hypex NC400 and / or UCD400 HG Hxr module

WTB - working Single Hypex NC400 and / or UCD400 HG Hxr...

Thanks

I decided to clean my space from some Sansui parts what I collect durring many last years... Some of them are used, the most of them are NOS, never connected to some power supply.
So, this is the list, first never used NOS boards:

- Board F-1075 for amplifier PA-100
- Board F-1267 for amplifier AU-555
- Equalizer/Tone Board F-1303 For Amplifier AU-505
- Board F-1319 for Quad Amplifier QR-500
- Tone Control Board F-1436 for Receiver Six & Seven
- Equalizer Board F-1435 for Receiver Seven
- Tone Control Board F-1207 for AU-777A
- Board F-1378 for QS 500
- Board F-1216 for Receiver model EIGHT
- Motor for Turntable model P 50
- Board F-1371 for Receiver model QR-4500
- Board F-1328 for Quad rear amplifier model QS-1
- Board F-1357 for Quad Amplifier QS-500
- Filter Board F-1208 for Amplifier model AU-999
- Equalizer Board F-3015 for Receiver TA300 & TA500
- Board F-2701 for Receiver 6060 and 5050
- Selector-Equalizer Board F-2727 for Amplifier AU117 & AU117mkII
- Tonearm for Turntable model PD 10
- Tonearm for Turntable model P 50
- Driver Board F-2661 For AU9900A/11000A
- Driver Board F-1278 For EIGHT
- Buffer Amp Board for TU919 F-2875
- Power Supply Board F-2963 for BA-F1

And now some used boards, but in very good condition:

- Loudness Board F-3084 for G9700
- Power Supply Board F-3070 for G9700
- RF Power Supply Board f-3071 for G 9700
- Equalizer Board F-3219 for G9700
- Audio Switch Circuit Board F-3079 for G9700
- Pre-Power Supply Board F-3073 for G9700
- Tone Control Board f-3050 with Volume Control Board
- Digitally Display F-3088 Board for G9700
- Power Indicator Board F-3082 with F-3083 and F-3077 for G9700
- LED Power Meter Board for G9700

I would update this post with new parts and I would remove sold parts.
For the prices and many pictures please ask, I can say the most parts are about from 40 to 60 US$, but some of them has higher price (like "Driver Board F-2661 For AU9900A/11000A" or "Tone Control Board f-3050 with Volume Control Board")
Some of pictures:











For more info, please send a PM, or better way... please send an email to kale_021@hotmail.com

I have a little project to make a DIY DAC using the Soekris DIY board. I was thinking about going direct to the Soekris from an RPI using the I2S GPIO pins. These would be side by side with very short hook up wire. My thinking was that I could get a better quality signal than using the USB to I2S converter suggested in the Soekris manual. Anyone see anything wrong with this idea?

Hi I acquired a pair of acoustat monitor x servo amps and am looking to replace the tubes. The issue I am running into is I am not able to find any information on what to use for values when biasing the new tubes. Would appreciate anyones help in this matter. They are original servos so the run the 6hb5 tubes

Brand new and unused. Original cost £110, will sell for £80 - free postage to UK.

I've obtained the Mullard Three-Watt amplifier circuit, looking to build it from scratch. Apart from obtaining suitable transformer, valves etc., might there be any recommendations or improvements that i'll need to take on board?
Apologies for not posting (04-07-2022)

I am modifying some old ML Aeons using the GRS dipole mid/tweeter attached to a 250x250mm 3mm alloy or copper plate. (the speaker is mounted to the rear of the plate so this should be as thin as possible and 3mm seems like a good compromise)

I am undecided whether to bolt this plate to the baffle or isolate it using 25x10mm neoprene foam strips and just screw it on the long edges to the Aeons frame.

The protoype below shows the speaker front mounted.

Which is best - isolate or bolt to the baffle?

I am interested in getting a spectrum analyzer.
I work on mostly tube gears.

Could you guys tell me which one to get and what to look for in a spectrum analyzer ?

What kind of bad effect in this NFB connection.

Output signal feed to input gate.

Thank you

Hello guys,

time has passed. The last time i opened diyAudio everything was blue and looked like the 2000s of the Internet... Nice to write something again in the new environment.

I have an old bluetooth speaker with a Yuan Jing 2.0 TPA3116 (black board) which is bridged to mono.
https://de.aliexpress.com/item/1005001936964672.html?gatewayAdapt=glo2deu

I wanted to modify my source/dsp section and disassambled the box. Since everything is lying on my desk the TPA doesnt work anymore. It just goes into protection mode when i connect a speaker to it. Which is very bad because i`m going on a 10 day vacation trip and as always i`m responsible for the music...

I must have destroyed something but cant find the mistake. Can someone provide me the instruction for bridging the TPA 3116 and the schematic? Back then i bridged it myself and i would bet that i just ripped something off.

Sorry for the bad english and greetings from Germany.

Hello,

I want to model a voice coil and use a voice coil calculator to help. The gap length is determined in the calculator using the magnet thickness and top plate thickness. Now I have the case that I have twice as long a winding length as the gap length.. can that be right?

MM phono preamp made by myself with ha12017 and ad797,the circuit diagram is also designed by me. The power supply part uses LM317 / LM337 to stabilize the voltage, and the power filter capacitor uses Germany's Mundorf capacitor, which has good performance, but I haven't found a decoupling capacitor on the amplification circuit board with good sound quality until I use Audio Note STD capacitors of various specifications. I made all the holes on the chassis by hand. The final sound quality is very good. Next, I want to use LT1963 and LT3015 as regulated power supply to see how the sound quality and timbre change

hi to all..... can anybody recognize this amp design? i saw this from i think a russian website, i could not understand the language, it looks interesting and uses just ordinary parts... thanks

Hi,

Im trying to model a scoop design in akabak, similar to the superscoop 18.
I seem to be having some issues in the simulation or meshing stage.




As you can see from the picture it looks as if the program isn't recognising some of the edges of the horns and the fields is spilling out at places. There also seems to be some irregularity from the driver where there are gaps with no field. Has anyone encountered a similar issue before? Is it likely to be a problem with the meshing?

I've included the akabak file if anyone wants to have a look at it.

Cheers!

UPDATE: Switcher has been Sold.


Regards,
Subbu K

FS a pair of Dynaudio Esotar² 650 Car Speaker

from 02-02-22 used only for experiments

price 517euro + delivery

Hi,

I am looking for a pair or maybe quad of these tube, if someone has them. It would be nice if they are inside EU.

Please, contact me via PM.

Regards

Restoring a pair of Hale speakers and require a pair of 8 ohm MCD 25s. It doesn't matter if they are single or double magnets, I believe the diaphragms are all the same.

I have 4 ohm bass driver which my amp disapproves of. I was planing to use 2 x 2 ohm resistors in series on the positive side to increase the resistance to 8 ohms (2+2+4). However, if I place the resistors 0ne on each of the speaker terminals (2+4+2) will it make any difference?

Well, a couple of my nice neighbors insisted on my lugging my homemade jukebox out of my garage where its sat for the past 7 years, unused.
Of course, they helped in the venture, thank god it's on wheels but weighs maybe 200 Lbs.
My neighbor and good friend Joe wanted to throw a BBQ/party on his side yard for a bunch of us.
The function was a total blast, everyone enjoyed the food drinks, and music.
Since I never heard my juke outside of the garage, I was also enormously surprised.
Those 8 speakers and 200 watt amp sounded absolutely amazing outdoors!

A few pics of the event......

Hello, Guys.🙇‍♂️I am using Pi3b+ with picoreplayer OS for my main audio system. I have different DAC hats for my Pi but it can use one hat only at once. Thus, I want to use the inactive one as a stand alone dac for my PC. I purchased a usb to I2s converter from Suptronics and plug-in with my dac hats and power hat. However, there are no response from all my dac hats. I tried the coxial output from this converter and it worked. Therefore, I don't know how to fix. Does anyone use it before? Thank you so much.

Hello, a friend brought me his amp because of a problem he couldn't solve.
It was only a broken RCA pin stucked in an input socket.
As the amp was on my desk, I would have liked to adjust the quiescent current, but I can't find the service manual. Based on the PMA-280 manual, there are two posts to make the measurement, TP1 and TP2.
I measured 5mV on both channels. Is it acceptable?
Thanks

I put a new head unit and a couple of amps in one of my cars recently. They didn't have the head unit I wanted, but had something similar so I took it. Well, after getting everything in I wasn't too pleased with the amount of bass from the sub. That is when I discovered the head unit I am using only has a 2v rms preout, while the unit I originally was going to use has a 4v rms pre out.
So, is there a pre amp of any sort I can use in this car to boost the pre out signal? Otherwise I will have to get a different amp for the sub.

I did a previous project of a transistor matcher for bipolar and mosfet transistors.
I have sold quite a few.
However a few people have asked for a 1 amp version for more real world testing.
My previous matcher used 45mA max.
So I have reworked the circuit to do up to 1amp.
Power to DUT is from 10 volts through a 10R resistor.
Base current is from a up to 10 volt source through 100r resistor.

The circuit itself is basically numerous differential amplifiers measuring Vce and Vbe to get Ic and Ib.
From this I can work out Hfe.

A while back (quite a while, actually) I posted a Class A design using an Ixys depletion mode fet as a substitute for the usual Aleph top side modulated current source, I actually had some boards done back when I was still using OSH Park for board fab (yes, they're purple...). I've returned to that design with a different scheme for biasing the topside current source. Attached is a picture of the partially assembled board waiting for a matched diff pair front end and some selected output mosfets. More action on this may happen over the weekend. When I get home, I'll post a prelim schematic (it's on my home computer).

Spec'ing #'s for upcoming tube amp project for buddy w/ plus size mancave...
Have decided on below EICO super mod schema which uses quad of 7591's... however I'll be using 6GM5's. B+ lists 450vdc @ 320ma using full wave SS w/ CT PT.

Three Q's related:

1. Should PT B+ supply be center tapped (2 diodes) or not using bridge?
2. Related to first Q, what should AC V spec be (CT or not) to achieve full load DC requirement?
3. See below hand scribble- can I hook fixed bias voltage tripler (-19v) up to 1/2 preamp fil supply?

Thanks,
Jim

Looking for help and ideas: See picture: I believe this might be called a 5th order band pass using a 3” woofer. The idea is to give an extra boost in the bass without the 3” woofer adding to frequencies beyond 400 hz (thereby adding to the higher frequencies) by using a passive radiator whereas a port might leak some out.

The picture shows the bass section is enclosed with fabric all the way around and is solid in the front and back with audio out the sides. Assume the passive radiator is 2 times the SD and the PR plus woofer surrounds can handle the sag problem and no crossover (full range drivers.) My questions are:

1. Will there be a polar cancellation of the bass if I sitting in front of it? If so, then I will “unsolid’ the front and back and make it a 360 outlet.

2. To find the port length, should I simulate as if it is a basic reflex enclosure (as if the pink area is not there?)

3. I’m committed to the design, so are there other enclosure (non – electronic) ideas that might make the bass more prominent, i.e. place weights on the PR and/or driver and increase the power to the max excursion.



Thanks

I have a leak trouble line II FM radio. The audio signal line is mono channel. When I came, it was connected to DIN 3 pin. Now I want to change it to 2rca plug. Can I directly split two left and right channel lines here? The positive and negative poles are divided into two lines, which are connected to the left and right channels of the amplifier. Attach the schematic diagram of the machine. Please help me have a look. Thank you,🙂

Hello all,
Just want to preface this post by saying i have very little experience
building or repairing any tube gear, so i’m reaching out to the experts for help.
My objective here is to lower the capacitance load my MM phono cartridge sees. It's a ClearAudio Maestro and according to its specs, it likes 100pF.
As things are right now, the 1.2 meter cable and the tone arm wiring are 200pF.
Additionally my preamp’s (MFA Magus) phono section has 47K shunted by 200pF according to the manual.
So total it’s 400uF not including any Miller Capacitance. I can swap out or shorten the cable as i don’t need 1.2 meters and knock off 100pF.
My issue is the caps in the phono section. I’d like to remove them or replace them with a lower value. Only trouble is i can seem to locate them, either by looking at the board or the schematic. The closest i’ve seen is a pair of .22k caps (C3 & C 11). I’m attaching the schematic hoping someone can take a look and advise. I’d appreciate any guidance. Thanks

​

SOLD

Asking $45 including shipping to continental USA

Pair of fixed +24 volt 1A regulated DC supplies and power transformer (Amgis donut on pcb)

Comes with supply documentation, schematic. Uses the 7924 chip.

Regulator boards from overseas, used in a proto amp, nice regulation when both boards run at same time off of the torroid using 100mA per supply resistive load. It may be a stretch to get to 500mA per channel from a regulation and heat standpoint.

Universal Socket Prototyping 2-sided PCBs for Vacuum Tube/Valve DIY Projects.
1) Extra Large 250x165mm / 9.8x6.5" - 22 Euro/pc
2) Small 180x110mm / 7.1x4.3" - 10 Euro / pc

My own design with universal tube socket mounting pads.
Unlike cheap versions from eBay/Aliexpress, made with 2mm FR-4 and are very sturdy, doesn't easily bend when inserting vacuum tube(s).

Compatible with miniature noval B9A base (12AX7, 6N2P, ...), B7G heptal, octal (EL34, KT66, 6550, ...) and B8G loctal PCB-mounted sockets.

Please note mounting loctal socket require ream (enlarge) central hole with 4-5 mm drill, and heptal needs ream (enlarge) 1 or 2 holes with 1.6mm drill. Noval B9A and octal sockets can be inserted as is. Leave message if you need to mount loctal or heptal sockets, I will make all required PCB mods for you.

On Large PCB adjacent groups of holes on borderline connected together to make easy assembly of power rails. It is the BIGGEST vacuum tube prototyping PCB 250x165mm available today (vs 200x160 sold on eBay), and provides a lot of space for assembly.

Pitch between holes 5mm.

Shipping in European Union 6 - 7 Euro. Other counties/regions please ask.
Payment via PayPal.

Would the ir21834s work as a sub for the ir21844s

Dear all,

I was testing out a Dayton Audio HDN-8, and I needed somewhere to put it while I was fiddling with wires. I attached it to a cardboard model of a horn that I'd put together last year, and the output was instantly noticed. I screwed it into the top panel of the horn, which was flat.

Has anyone tried combining this with an already working horn? I just thought I'd ask in case it was worth investigating further. It might make for an interesting 2-way point source that doesn't require all of the synergy horn 'fun' 🙂

Thanks!

Hi, in this picture i made this schema of an input for lm1875 amp and i wonder if its all good or if i can make anything better.

The CN3 is 50K potenciometer.

And i will connect it directly to amp input, no other filters.

Thanks for help guys 😉

This custom electronic crossover is based loosely on the Dahlquist DQ-LP1 crossover, in that it is passive (first order) on the high end and active 3rd order on the low end. Power supply and parts are significantly upgraded from the Dahlquist version, starting with a large 120VA power transformer with a Sulzer low impedance regulated power supply with pre-regulator. The audio section uses selected and matched WIMA polypropylene caps, Holco resistors, and OPA2604 op amps. The low pass level control is a Noble dual pot. The low pass frequency selection is accomplished via gold plug-in sockets, and a modules are included for 100Hz (in the unit now) and 40Hz, plus some blanks to assemble any frequency you need. The circuit also includes a fixed 3rd order high pass filter at 18Hz. Includes schematics of both the power supply and audio circuit. This unit completely re-capped a few years ago. Cosmetically, the faceplate looks excellent, but the rest of the case shows some wear and use marks, especially on the plexiglass cover. Note that the unit has a power-on thump, so the front panel muting switch should be in “mute” during power-up. Asking $450 plus shipping.

I own a SUT with two primaries 0-40R parallel connected, to do the calculations for loading what's the primary value 20R because are connected in parallel?

I am new to the forum but I have been reading about the 833A based SE amps. I have a supply of 304TL tubes. Would this tube be suitable for a class A SE? Any suggestions for a circuit? Would the driver and output transformer selection be similar to the 833A?

Thanks in advance.

Frank

They where quite popular for audio a couple of years ago...

Hi there, I am repairing a Cambridge Audio A1 that has the LM4766T chip, and I can only find Chinese versions these days, ebay seems to be pretty much the only outlet since TI stopped manufacturing them. No stock on RS, Rapid, etc

I have had mixed experiences with Chinese semiconductors over the years. Does anyone have tales to tell on the quality of these particular chips, good or bad? There are some that are described as being made by National Semiconductor. Are there any particular stamps or codes to watch out for?

Thanks,
Dan

Hi I’m finally finished. Se mono block. Amp. Tube no 304tl. Run with 700v vp. Around 100ma. Idle

It's a Lenovo desktop installed in an old Carillon case (only the power switch on the front panel connected) with i5-4570 CPU, 8GB ram, and 100GB SSD. Windows 2012 R2 with Acourate installed. It's built in 2012 for configuring my 5-way diy speakers. Now the speakers sold. I will include the hard copy of Accurate Sound Reproduction Using DSP. Lynx AES16 PCI card installed. Please feel free to let me know your interesting with or without the Lynx AES16 card.

Hi,
I've just built an LM3886 kit and it's all good when test outside the case. The odd happen when I put in the case. The big resistor was almost burnt. What happen?

I don't have circuit diagram but I traced the PCB and the almost-burnt resistor are in Zobel network (R9, R11). I was able to repeat the problem when connect input wire and when I checked, the input signal ground was shorted to the chassis (I didn't connect any source). Speaker wires are open circuit when this happen.

Another thing I didn't do prior to this is that I've omitted C3, C4 which seems to be negative feedback network. This PCB use 33pF and 220k resistor in parallel. Would this be the reason for open circuit oscillation?? Is it even oscillation? The capacitor was left out because one local builder suggest that he felt it's restricted the treble response of the amp.

So, I fixed this by redoing the input signal connector and ensure that input ground is isolated from the chassis. I also soldered C3, C4 in. I left the almost-burnt resistors in since they are still measured good at 10 ohms. The amp is working good now for few hours, but still curious what was the cause.

Any thoughts?
AP

I just wanted to re-configure my nu3000dsp and i did not save previous installer file, but when i google it no link is active anymore even on behringer site. gezzz what happen? 😕

Behringer | Product | iNUKE REMOTE CONNECT
Behringer™ Remote Control(C)

if anyone keep the installer file, please share it in any hosting website or google drive

thanks alot

This thread is for my "Use Your Illusion, II" OB design, combining OB with Polk's SDA driver arrangement.

As we know, Stereo itself is an illusion and a pretty good one. Dipole effects from an OB (or other arrangement) casts, IMHO, a wonderful 3D "soundstage" where the out of phase backwave is contributing. This design augments that effect with the "Stereo Dimensional Array" effect from adding two additional speakers in the typical Polk arrangement for doing that.

That arrangement involves something called the intra-aural distance, which is simply the distance between your ears. I measured the back of my skull with a caliper and came up with appx 5.5", which is the horizontal distance between the drivers in the SDA arrangement. So on each baffle plane there is the main speaker and to the outside of it, 5.5" away, the SDA speaker.

The electrical arrangement has the right SDA speaker running out of phase with the left main speaker - and vice versa. Because the drivers I used are 4 Ohm, I decided to connect them in series to avoid a 2 Ohm load on the amplifier. Speaker cabling consists of the usual pair from the amp to each speaker and a single pair running between them. However, to make the circuit I swapped grounds between the channels; each channel makes a loop from amp to speaker, to the other speaker and back. Each speaker cable pair carries L on one wire, R on the other. Unsure what this does "speaker cable effects" wise, but it's unlike any other.

I have an 8 Ohm non-inductive resistor across each of the SDA speakers, padding them down a bit, so the main OB speakers are somewhat prominent. Of course, reactive elements can be used as well, to change to frequency content on the SDA drivers; I've read where the SDA driver doesnt have to emit the full frequency spectrum. For simplicity at the outset, I'll leave them full range.

One acoustic trick I've implemented is enclosing the SDA drivers, to prevent rear-radiation from those. It's not clear to me if augmenting the rear radiation of the main driver with an opposite channel, out of phase signal is useful regarding the OB depth illusuon. It's certainly a factor to experiment with, for now I'm going to leave the SDA drivers enclosed. Of course, that enclosure type can be improved from what's shown here.

I made up a working mock-up out of scrap 24" square plywood shown in the pictures below. The drivers are Mark Audio, CHN50 and Alpair 5.2. Due to workmanship difficulties with the baffle cutouts, I ended up with the 50s as the main and the Alpairs as the SDAs. I left them to cross at ~200 to the bass drivers being a pair of H frames. (Part of the justification of getting to have these in the BR, is my wife gets to use the H frames as a platform for her flower and veggie starts in the spring. Done deal! So the bass changes some when I push them back toward the window...)

Their sound really is a true combination of the OB sound I'm used to plus the SDA fattening of the image width, such that it's no longer just between the inside edges of the baffles. The panels seem to respond to a deep amount of toe-in, regarding inside image focus. This to me suggest the SDA drivers need to lead a little in phase, relative to the main driver. Effects from the sloppy mock-up build seem to be the main drawback at this point; when you play loud, those thin plywood panels start to emit their own driver mounting conducted crud and I can hear it.

I've lots of material I can fix that issue with. Plenty of 1-3/16" MDF to make a couple higher mass panels or other shapes (barrel?) out
of. The machining of the driver cutouts such that the back of that Alpair 5.2 really radiates freely, while the front remains free and clear
also is challenging. It would be great to mount the Alpair to the baffle front plane, the CHN50 to the back plane of a 1+" board to get a little mechanical offset, but I'm having difficulty imagining the cutouts nevermind executing them. Example, what's the proven waveguide curve for the front of one of these small diameter drivers, the back of the other - that still allows screws to hold it fastened? Seems I'd have to make a tool to impart that curve, whatever it is...

Anyway, I find it a pleasant listen and so easy to do. Any inputs, encouragements, thoughts are most welcome!

It seems that most 1210mk2 users either go with Technics factory alignment, or goes with Lofgren A (better known as Baerwald) as alternative, so let me start with my short insight of them.

As known, Technics factory alignment is variant of Stephenson, with null points somewhat closer to the spindle. What bothers me with both is tracking distortion rising fast above inner null point, reaching higher max. value between null points compared to Lofgren A. So, at 70mm from the spindle, which is still close to the last groove, distortion is quite high.
From my experience, Lofgren A gives overal improvement in sound but with inner null point at 66mm last groove performance may be compromised, especially with cheaper carts/styluses. Also it requires 2,82mm of extra overhang and 1,66deg of extra offset, so cart looks weird in a headshell. Some carts even cant be aligned like this with original headshell beacuse you cant move them far enough to the front.

So, I came with two custom alignments between these two, both offering some improvements. I worked with them for the last four years with no negative effects on my records or carts, so they are safe to try. They will work on all Technics TT models with arm pivot to spindle distance of 215mm.
Results are calculated and presented with graphs made with vynilengine Alignment Calculator Pro. Thank them very much for this wonderfull online tool.

First custom alignment has extra 1mm overhang and extra 0,5deg offset angle compared to factory setting, giving 16mm and 22,5deg total values. Null points are 62,35 and 114,45mm. This gives same distortion level in a last groove (at IEC 60,3mm), so performance at this point is not compromised, but with reduced distortion between null points and at first groove. As result, average rms distortion drops from 0,53 to 0,46% and max rms distortion drops from 0,9 to 0,84%. Distortion is increased below 60,3mm but still only half compared to Lofgren A. Since very small number of my records have modulated grooves there, I found this aligment much better compromise compared to factory setup and its now my "official" alignment for this TT. With this, you get best of both worlds. Some of reduced distortion from Lofgren A, especially between null points, and improved last groove tracking from Technics alignment. Also, appearance of cart in a headshell is not compromised beacuse you practicaly wont see visual difference.

I made this setup with hand-drawn arc protractor and tried it with few combinations of Grado Prestige carts and styluses. Blue1, Blue1 with Red2 styli and now my old Gold(no number) with Red3 styli. All at recomended 1,5gram vtf, antiskating at 1,65 and arm heigt at 1-1,5 for most of my records and with original platter mat. Iam very pleased with performance which resembles Lofgren A setup. Regarding IGD, those Grados are not known as pristine trackers, but so far they behaved very well. No problems on good, well preserved records. But be careful with styli which are of quite mediocre quality. From my experience they dont last long and deterioation in performance may occur with less than 150 hrs of play. When that happens, it will become worse fast, so dont hesitate to order a replacement. And dont try to prolong the life of worn styli by increasing the vtf unless you want to screw your records.

Here are the graphs, showing tracking distortion and tracking error for custom 16mm/22,5deg alignment (yellow), Technics alignment (red), Lofgren A or Baerwald (blue) and Stevenson (green). I will present second custom alignment in my next post. Be free to comment and share your experience with alignments for 1210mk2.

No teardown photos this time, but here are a few response plots of two Radian LT3 drivers I got. I've also attached the 3D model for the waveguide.






I think these drivers internally must be very similar to the Neo3, only with bigger magnets and fewer but larger holes on the front. There is a striking similarity to the two dips in the response of Neo3 drivers at about 3KHz and 7KHz.

Shanti is sold, please see other post for USBridge

I swear long ago there was an outfit selling paint intended for speaker cabinet interiors. Trade name was "Black Hole", claim was paint the interior of your speakers cabinets with this stuff - they'll sound better. I cant find it on the market these days...

We do have the so-called rubberized paints, for tool handles and - I guess people fix car interior upholstery, paint their alloy wheels with such stuff. "Plasti-Dip" and "Flex-Seal" are two current brands.

My question is, has anyone used this stuff for their speaker cabinet interiors, in an effort to improve panel damping and absorb sound - as the original product I think I remember once existing was supposed to do?

I've got the back-sides and edges of a couple panels to paint yet and I was wondering of there would be any advantage to using this stuff, versus ordinary paint. It wouldnt be that expensive to try.