SOLD

Asking $635 to include insured USA only shipping. New this unit, including shipping, is approaching $1300.

Selling my eTracer tube tester. It requires a Windows based PC to function. You must supply the computer.

It has worked fine for me on a few hundred tubes tested. Results can be output to certain Brother printers.

I have gotten away from tubes and most DIY audio endeavors now, but still have a few things to part with.


Those not familiar with the unit / concept can read about it at their website.

https://www.essues.com/etracer/

This is the tester housed in their chassis, run by a Meanwell internal power supply. You must manually change the position of lead wires for each tube type, but there is an automatic switcher option at the website.

Comes with the tester , lead wires, and copies of manuals as shown. I will supply the necessary config file to calibrate this particular machine to the new owner once the unit is purchased.

https://sklep.toroidy.pl/en_US/p/TSTA-0220001-Mains-transformer-for-tubes/647

2 units. 1 is completely brand new, the other one is slightly used. The used one was glued to metal chassis with polyurethane sealant and has some leftover of it. Other than that it is as perfect as new.
I can provide photos on request.

80euro each. Will do a discount when buying both at once.
Located in Lithuania. Please contact me for shipping costs.

Primary 230v

Secondaries:
300mA 270v-0-270v
2x 3A 6.3v
2A 0-5v-6.3v

Some fun visual of waves, there are many options to choose from in the upper right corner

https://www.falstad.com/ripple/

In a 4-channel amplifier built with two identical stereo modules and PSU, is it better to have each module drive say left speaker's tweeter and midrange (for crosstalk) or left and right speakers' tweeters (even load)?

Hi everyone,

I recently did some testing and had measured I2S signals coming from my different sources. Digital output from the audio precision (exact I2S protocol), my WaveIO and my RPI 3B Running Ropieee as Roon endpoint.

I will show signals in the next posts. My request is, if anyone with an oscilloscope could measure the Wordclock (or LR) and DATA output together so I have a confirmation that something is not 100% or that there is something in my setup not correct, which could be the case of course. Hence this request…. I just need a totally different setup somewhere for comparison of the signals

Thanks in advance !
Doede

I need the Xover design of Proac response 3.8.

The unit is Scan speak 9900 + pair of 8545.

I got one, but it's a little weird.

So I want the check it's original or tweak.

And I think a thread which contains many Xover design is needed.

Thanks..

I have this amp for 15 years in classA 50w, see picture bellow.
At that time I could find from a nearby vendor 2sk2182 as best.
I simplified to minimum keeping decent damping of 40.
This amp is intended to those like me are convinced good sounds come from simple circuits.
It has 0.1% @20khz by far inferior to any speaker. It can make very reliable instrument amp.

Hi there,

Just wondering if anyone who knows this amplifier board can tell me:

If I connect a higher load than the amplifier is specified for, can it protect itself against damage?

I'm going to be using it in BTL mode (I have the bridge board) and I believe this means I will have 450W @4ohms available. If I connect another 120W @4ohms, will the board be able to protect itself?

If not, can I 'manually' ensure the board is not damaged by simply not driving the speakers as hard?

TIA
Peter

I have a Hafler TA-1600 with classic “no bass or midrange” syndrome apparently attributable to failed surface mounts capacitors. Both channels afflicted. I am not competent or set up with proper tools yo remove and replace the caps so I contacted a local shop specializing in audiophile and pro gear. They said complete recap will exceed $350.

I want to go forward with repair because I just hate seeing the chassis, heat sink, transformer and lateral MOSFETs go to waste. What advice does anyone have in terms of going forward or not?

Hello all! I recently acquired a nice working set of Advent Legacy III speakers. This is the version that has a dual 7.1ohm voice coil woofers. The switch changes the crossover to yield a 6 ohm (normal) speaker OR an 8 ohm (when multiple speaker sets are used) speaker. Attached is a diagram of the PARTS and connections I have identified. I am stumped as to how to draw out the two XO circuits. For those who like a puzzle, my request is if any of members could draw out the diagram for the 6 ohm crossover; 2) The diagram for the 8 ohm crossover. Thank you and enjoy the challenge! I am eagerly waiting! :>)

Hello, I am using Camilladsp with volumio an RPI4. It is a 2.1 analog systen for the main speakers and dsp-based sub.

The issue is that due to sub dsp delay - nominal 5ms - there is substantial time mis-alignment. I'm not in a position to move the sub out 3-5 feet into the room.
I have an active crossover at 50hz for sub and main power amp. LR4 slopes.

I propose an alignment method as follows:

Duplicate L channel and the same with R
On first L channel, apply LR4 low pass and on second a LR4 high pass at 50hz. Same with R channels.
Apply 5ms delay on high channel of both L and R.
Combine (sum) both low and high channels for L and the same for R
Pass on to convolution filters for rest of EQ.

Thus delay the main speakers by 5ms allowing me to keep the sub in the plane of the main speakers.

Does this hold water, and what complications could there be?

Cheers

I have a pretty magical pair of bookshelfs, a T-Amp that has surpassed all expectations and a 18650 battery pack to power everything. I have been bringing this setup on camping trips and the sound quality is magical, especially compared to those awful shrill $100 bluetooth speakers other friends bring... which I believe are causing permanent irreparable damage to my central nervous system.

This year I am adding a sub (not really needed) and packaging everything all together in a neat box to make an easier to transport package. The amp/battery enclosure is sized to perfectly fit on top of the small sub. I want the speakers to attach and easily detach from the amplifier/power enclosure. I am an accomplished woodworker and also have access to a pretty decent machining facility.

Any ideas on how to attach and lock the speakers to the main enclosure for transport while being able to quickly detach them for use? Sometimes lighter speakers and no sub would be much easier to transport so I would like to attach different speakers just as easily. I have several pairs of quality but beaten up bookshelf sets that I have picked up used for cheap over the years. I am not worried about devaluing these speakers by adding brackets to them.

I am also sick and tired of banana plugs! Even decent quality banana plugs! I want something quicker and easier... and preferably locking. I am looking at the SpeakOn connectors but get the impression that they are kind of big and clumsy. I spent over an hour searching this forum but couldn't find any great ideas for compact speaker connectors. I do have a small collection of XLR connectors and they are kind of big and clumsy for a small portable system. I am considering RJ-45 female plugs and Cat-6 shielded twisted pair cables for connecting the speakers. I am thinking of ganging together 4 leads for positive and the other four leads for negative with each twisted pair having one positive and one negative wire. This isn't a low powered system. I feel comfortable altering the speakers with Cat 6 RJ-45 plugs.

P.S. I appreciate "out of the box" thinking and ideas!

Hi

Just sitting at work, and having lots of spare time offshore.

So I'll might plan and order caps to do this job.

Plan to use it with a 218 THX, that's also might need some service...

So maybe someone sitting on a cap list and might share it.

Also it's challenging to find a decent service manual with good quality.
The one i got from net, is so so.
Challenging to read some values on it.

Had to fix the motorized volume potmeter. Somehow stuck motor.

I will install a simple BT receiver in it as well.
Did that mod on 2 of my 3400's, with good result.

Hi Everybody,
Have just recapped a Nad C326BEE , only ones with high ESR and replaced some components as advised in the service manual.
I have set the idle current which is stable but I am confused to the setting up of the ISC adjustment. everything is set up as per the text below but can't seem to get anywhere near.
please can anybody help as probably missing something stupid
cheers Vincent

B. ISC adjustment

1. Turn VR304 fully anti-clockwise,
2. Use 500mV, 1kHz sine wave, CD input, 4 ohm loading to both channels
3. Increase the output power of both channels to 8V
4. Slowly rotate VR304 clockwise until the voltage at TP10 is the same as TP11
5. Verify the output at 20kHz 8 ohm loading to both channels are larger than 21V, if not, repeat step 1-4 again
   

Hi Folks, I bought the Pioneer TSA30S4 12inch driver to replace an old Gale one that lived in a ported cabinet, replaced the Amp with a Fosi Audio TP-02 sub amp. I'm getting a weird whistling ( port chuffing? ) noise at around 20-30hz it's pretty annoying. I'm not an expert, but I'm wondering if either the amp is not suitable or the driver is not working as it should. Please have a look at the vid and the amp specs attached. Any advice appreciated!
Thanks Dan

I have a chance to get one of these pretty much new in it's box, looking at the specs you would not think much of this sub but apparently it is one of the best sq subs around, I was going to get an alpine type x 12 or maybe even an Dayton Audio RSS315HO-44 but now the Mac audio has come up and presents a dilemma.

The Mac audio goes low enough, 18hz by all accounts, has quite high sensitivity but the specs say it only has 4mm of xmax.

Anyone ever have or hear one of these subs?

I heard the ten inch version and it was the loudest ten I have ever heard.

Spec sheet below.




Regards

For the diameter input, do you use overall, nominal or cone diameter?

Hey guys got a very good sounding dac it uses these LT1819 for the balanced or single ended output buffer. Is there anything better??
(Note these run on +-5v rails, +- 6v max)

https://www.analog.com/media/en/technical-documentation/data-sheets/18189fb.pdf

Cheers George

I bought 4 of these old stock LME49990 opamps chips from the seller on DIYAudio. I planned to solder them onto SOIC-DIP adapters for my CNC Phono stage but got out of vinyl hobby altogether. I paid $80 for them and $10 for adapters. I will accept $40 + $5 shipping in cont. USA.

I have perfect Audiogon and eBay rating so feel free to check, user id dvzzz.

Hello

About a push-pull vas (the image are a part of a power amp), in the circuit image I include, Q5 and Q6 are the push-pull vas, Q7 and Q8 are the bias.

But what are the fonction of Q11, Q12, etc... ?

And where do I put a phase lead in that vas of a amp circuit ?

Thank you

Bye

Gaetan

Superb quality LEMO connectors size 1B, 4 pin for balanced headphones. Unused and mint.

1 x cable plug & 2 x panel sockets

£40 Plus shipping

I found these in a B2 amp that I’m playing with can anyone ID them? Not your average package for sure.

I started to look at it a few years back. It would be interesting to see if it offers useful compromises in other horns vs venting the back chamber to the external world.

I'm doing some required 'maintenance' on the front-right channel the amp board in this unit.

Transistors were shorted, resistors were fried.

Replacing the PNP/NPN resistors without the bias transistor, I couldn't get the idling current below 100mV. So, I am replacing that and also replacing the transistors again because they are way out of range of what the rest of the transistors read.

What is a good temperature to see these transistors at? I registered 150°+ F (60-70C) with no volume (HEOS is paused).

First question: Should I be looking at other resistors to make sure they are in range or is that a normal operating temperature?

Second question: Other than Lead-free, what other properties should I have with my solder. (Size, Flux core)? T

The first time didn't come out with any perfection at all, I would like to make sure this time looks better.

Cheers from Germany to the friendly folks out here!

I am happy to have discovered this incredible forum. I have already been able to learn a lot by passively reading along, but I hope that I can also receive helpful tips for some specific questions (in the respective sub-forums).

Apart from a brief how-do-I-get-as-many-people-as-possible-to-listen-to-my-music-tastes-through-my-car-system phase now half a life ago, I've never really had anything to do with or interest in audio systems. But recently, I had the idea of trying a record player in addition to streaming music (I wasn't allowed to touch my father's system at the time, so this was/ is really new for me.)

As luck would have it, a very good friend who now also has young kids (pulling on cables all the time) wanted to sell his system but gave it to me as a birthday gift a few months ago, when he learned about this new interest of mine. That was the foundation stone, to which a few other parts (some vintage, but nothing fancy) have since been added. As a result, my home office has also become my listening room. And I'm having really a blast with it.

Then last month I was lucky enough to be shown the main system by a very friendly guy, which totally swept me off my feet. The whole system is the result of a long journey with many iterations, DIY-mods (and certainly a lot of money). Even though I am aware that the individual parts of the entire chain and their interaction and tuning to each other are very important, I assume that the loudspeakers are responsible for most of the wow effect. As I don't have any comparisons with other (high-quality) systems nor any solid acoustic understanding, I'll keep back from trying to describe the sound in detail. I can only say that it was simply a different dimension to anything I've heard before, especially for vocals, but also this feeling of "just beeing there". An album (Made in Japan - Deep Purple) that I have listened to countless times before was hardly recognizable, in a good way, obviously. The speakers are some quite unique OB with PHY-HP 21/15 drivers and piezo tweeter wired in parallel, phase-inverted and without xo.

My goal now is to have, or at least approach, this experience in my own home using the DIY path, with a reasonable budget and little experience with electronics or woodworking. After reading a lot back and forth, I think that the Manzanita might be a promising and managable OB-project. But I'm unsure whether I have a chance of being happy with OB speakers in my room, where the speakers must be placed under a heavily sloped roof. I think it makes sense to ask this question in the respective thread with a more detailed description and pictures.

If this proves to be unfeasible, I also love the idea of going "completely FR" and xo-less with building a set of Pensil speakers.

TL;DR:
I want to built my first set of speakers and hope to find some guidance here, so that I don't mess up to badly. 😉

I began working on this program years ago, back in 2010. Now, having just finished version 3, it occurred to me that sharing it here might be a good idea - especially since I use it regularly myself. Essentially, it’s a simple yet effective tool: while it only simulates SPL amplitude versus frequency, it’s straightforward, intuitive, and gives me exactly what I need when working with loudspeakers.

Some of the features:

• There is a large driver database included, mostly up to date. If you want to add a new driver to carry out a simulation, only six parameters are required: Qms, Qes, fs, Mms, Dd, and Re. The rest is calculated. The small hidden "=" symbol in the lower-right corner serves to rename records.
• The Up/Down keys change the numeric value by +/-1. For fine-tuning, hold down the Shift or Ctrl key beforehand.
• Double-clicking on the form will expand/contract the window; double-clicking in the graphs will quickly draw the response.
• There are a number of tools in Advanced options, for which I might write a simple tutorial later - such as TS parameters calculation, Shift of resonance frequency, Added resistance to voice-coil, Added mass to cone, Air coil, etc.
• Clicking on the counter above the listbox shows a detailed list of drivers.
• There are three types of enclosures you can simulate - Closed, Vented and 4th-order Bandpass. The closed box also includes a Linkwitz transform tool.
• The txt button in the header shows a list of main parameters ready to be copied to a file or a website.
• Blue labels can be clicked on, such as Dd to Sd, litres to cubic feet or Bl to Mpow (which is Motor power-factor - you can see it on loudspeakerdatabase.com or in Punktkilde datasheets as a Bl/sqrt(Re) constant; more on Claus Futtrup's website).
• On the Formulas page, you can see relationships between parameters and copy them into Excel.

You can download the program from Softpedia or directly from the audioweb.cz homepage, where an updated driver database file is also available.

Some antivirus programs - including Windows Defender - may mistakenly flag it as suspicious. This is a false positive. To verify its safety, you can check its status using the VirusTotal API.

I'm in the process of getting an oscilloscope - probably a Siglent SDS804X HD - and thought it'd be handy to add a waveform generator.

I'm fine with doing analysis on my Linux laptop, and was looking at the Uni-T UTG-962G ~£147, and the Siglent SDG1032X ~£277.

So what are you using, and how do you like it? 🙂

Hey guys, would really appreciate some help before I completely reinstall moode. Today I installed mpdscribbler. I recall during the installation it asked if I’d like to overwrite two different configuration files, as they were different than what I had. I said yes to both. I don’t really know why.

Everything has worked correctly since then, besides Bluetooth. When connecting to moode via Bluetooth, there is just complete silence. Connecting works fine, but it’s just completely quiet.

The files that were overwrote are /etc/squeezelite.conf and /etc/upmpdcli.conf.

Does anyone know how I can revert these files to what they were previously?

Hi - newbie here, updating my beloved console and keeping it original as necessary.

‘62 Magnavox 9302 I’ve been working on has me perplexed and I’m trying to run down the issues.

New PS caps installed and checked.
Great sound.

Questions:

1. PT gets 150°F after 1 hr - what can I do to lower this?

2. Heater supply to pins 1 & 2 of the 6EU7’s reads 12 volts - is that right?

3. 6EU7’s plate voltages read 167, 176 (130 nom) and 200, 210 (160 nom)

Those are way out of spec - 30-40%

I changed a .047 coupling cap and there was no change.

How do I get these voltages down and how do I get the PT to run cooler?

How do I check the PT to be sure it’s not toast?

Thanks in advance; I searched extensively but no one had these exact issues.

I looking for waveguide eliptical for tweeter Bliesma 34B....

Hello, This is my first post (I reside in south Louisiana). I picked up this Cambridge Audio A3i and am wondering if the terminal bindings can be swapped out to ones that accept banana plugs. These are solid brass with no "cap" to pry off. They look to be banana plug "friendly" but aren't. I can't find a lot of info on these b/c of the style they are.

Anyone had any experience with swapping these out on a cambridge model ? I really like this little amp and want to clean it up.

thanks in advance

Found my old Polk Cobra cables and wonder if the horror stories of the high capacitance could be a problem with amplifiers using the THF51?

Mine are in ra7's TDV configuration - a buffer - if that makes any difference.

Are these devices sensitive to the high capacitance? I am planning on using them in triplicate which would only make the capacitance even higher.

Any opinion or counsel?

Hello everyone

I've recently acquired a bewitch 6550 amplifier, that I just bought some new tubes for.
Changed the tubes after about 5 minutes it gave a very loud pop in one speaker, and I switched it off.
Then reinserted the old tubes to see if the noise disappeared, it was still there but more of a crackling sound from the same speaker that made the pop sound.

I removed the tubes and unscrewed the bottom plate to see if anything weird was going on in there, this is what I found.


As you can see the resistors in parallel is completely cooked.

How do I fix this correctly?
I know that I need to discharge the capacitors so I don't get electrocuted.
But this is my first tube amplifier and I really need some experienced user's to help me out 🙂

Hi. Wanted to share my newest USB to I2S 8ch board. As always ready to buy boards doesn't fit my projects perfectly, so had to make my own version. It is 8ch out/8ch in USB to I2S. All outputs and inputs are with lvds drivers for longer lines communication. Up to 192khz. First input channel has hardware ASRC if needed. I developed it for use with linux for embedded purposes for interfacing sabre DAC's Mounting holes fit khadas vim3 board or RPI. Based on sabre chip.
Not very universal as it has only I2S no SPDIF or other nonsenses 🙄 In case someone needs just like this I could sell in EU.

I've got way too much stuff in my garage. I tried to get rid of this before my move last year, but couldn't get my act together, so just crammed it into my garage. Now, time to let some stuff go.

I've got two batches.
-the first batch is the entire lot. I don't really want to separate because I want it all to go...
-the second batch is in the next post.

-----
Dayton

RS180 8 ohm shielded pair

RS315HF-4 12” Sub single

RS315 prototype single (this and the one above are very similar, but I can't say if they are identical. It's a long story. PM if you are interested.)

RS 10” prototype RS Sub single shorting ring single

RS 10 RS series sub 2 shorting coils pair

RS225 8 not shielded single

RS28A 4 ohm three

RS28F 4 ohm single

RS52 midrange pair

Dayton dome mid 285-010 pair

TB W5-1685 5” underhung pair

Morel MDT55 pair
(but one has irregular impedance curve so I would imaging FR is suspect)

ZaphAudio ZA14 pair

Viva XG18WH00 pair

Peerless HDS 5” 831883 pair

Hales (Vifa D26AG-38-04) three

Seas Excel T25 C003 one

SS D3004/6600 single

Sub cabinets with 12” cutout maple finish fair condition (cutouts work for the venerable Peerless 830500 or equivalent size) pair

Everything in this post, all as a single lot is $500 for pickup from Lincoln CA.

I’m loath to break anything up out of this lot. If you’re dying to see impedance curves and pictures, I can run a few impedance curves with Cliowin. But, er, don’t ask to run curves for everything. The whole idea is for me not to wast a lot of time with this lot… The only driver that I know is a bit suspect is one of the Morel MDT55’s. (I did actually run curves for pretty much everything here...just can’t find the files…)

Every week the lot doesn’t sell, I’ll drop the price $100… Yes, in 5 weeks it will be free…

Hello. Has anyone made an elliptical waveguide for the 2908/71400 revelator tweeter? Or maybe someone has some information?

Ever since hearing the custom designed Synergy Horns used by Soundstorm Pro at Esoteric Festival in Australia, I've been curious about them. More recently I have read multiple build logs of various interpretations, most recently the MEH design - which at some point I'd love to make when my budget is permitting, in the meantime I was hoping to design a more budget friendly option using the Synergy Calc V5 - but I've ran into some knowledge gaps and I can't find clear answers from the documents I have read so far.

I have several questions about Synergy Horns, specifically related to the Synergy Calc V5:

1. The choice of compression driver is referenced vaguely, specifically the Celestion CDX1-1445, without explanation. Why is this driver chosen? Or more broadly, what makes a particular CD optimal for use in a SynergyHorn.
   
   
2. The Compression Driver is not included in HornResp modeling, only the midrange and woofer. Why is this, and how does the performance of the compression driver change with the Horn Dimensions, impacting the overall design?
   
   
3. In modeling the performance of the midrange driver, I adjust the horn shape to optimize its frequency response. However, when optimizing the woofer, it disrupts the midrange settings. What might I be missing in this process?
   
   
4. Is a flared adaptor necessary for fitting the compression driver to the Horn Mouth, or is directly mounting it sufficient?
   
   
5. The documents mention the distance of the Midrange Expansion Ports in the horn but lack detail on determining the best distance from the throat. What calculation or principle should be used? Is it within 1/4 wavelength of the crossover frequency of the CD? for example if the CD was crossed at 1000hz, it would be 90mm?
   
   
6. How do you determine the position and size of the port opening? For example, once I know how far it will be from the throat, how do I determine the position of the port relative to the driver, as I see it's most often offset and not centered in the middle of the driver position? And then the size of the port?
   
   
7. Most designs use a rectangular expansion port for the Woofer instead of a circular one. Why is this?
   
   
8. Does rounding or flaring the expansion ports enhance horn performance?
   
   
9. The calculator includes a section on maintaining directivity over low/mid frequencies. Why would one want to maintain directivity beyond natural effects, especially in near field applications?

Thanks very much.

Andrew

They've got eight tubes, four per channel, in the phono stage of the SP-10, plus another four in the high-level stage! What are they doing with all these tubes? The only other phono stage I've seen that uses eight tubes is the Aikido design (http://glass-ware.store.turbify.net/ph2.html), which says in the notes that it uses one gain stage before the RIAA network, and another after, to account for the insertion loss of the RIAA network. Is Audio Research doing something similar? How do other designs with less tubes handle this?

SP-10 reference: https://www.arcdb.ws/model/SP10

I have the first I believe Maya200 from Hugh.

I've been burning it in over Christmas after Aussie Post lost it for 9 days silly silly wombats.

I must say it sounds very musical and powerful sounds like more then the 250W it pushes into 4ohms.
The low end driver grip is very strong and the sound stage is very wide.
No fatigue or SS glare at all tube like but with power.

Looking inside there are only two output devices per side for each channel.
I'm very happy with this AMP much better then the Bryston SS7T's it replaced.

Highly recommended.
Happy New Year
Garry

This is a good video to talk about open baffle speaker...
Login to view embedded media
Why open baffle sounds better... ?

Some of you might remember my article in AudioXpress of a few years ago for a tube amp high voltage delay. Many people build it, but it was time for a New & Improved version (really!).

AudioXpress published it and agreed to allow free download for diyaudio members (nice people there!).

Jason agreed to make a kit available in the diyaudio store.

Let me know what you think and we can disuss details of the design here.

Jan

I’m trying to work out the best way to supply heater voltage to eight JJ E88CC or EH 6922 via PCB. AC is right out. Regulation is unnecessary (and wasteful). There are totem poles in the circuit, and while I don’t necessarily have to elevate the heater supply, I hear it’s good practice with an eye towards cathode lifespan. Doing it bipolar seems to make more sense than stacking the heater voltage atop a reference voltage. Luckily, two diode drops and two Vbe drops get me from rectified potential back down to filament spec. My lack of a center tap does complicate things.



R and C values are generic for scale. That’s millifarads, not micro. I didn’t draw the RFI stuff and inrush current limiting on the primary, but it’ll be there.

Do I need loads from my new rails to the reference voltage? At the 7.5V mark, the 6.3V mark, or from the bases? Could I nix the center reference entirely after the rectifier and just cap across the rails? Any suggestions for the right NPN / PNP pair in through hole? Are there significant advantages in moving to a Sziklai approach in this capacitance multiplier application?

Hi,

I offer here my F5 Board Set, please see picture.

Cost: 45€
Shipping:

• D (without islands): 8€
• NO UK too much paperwork for me to the customs declaration, sorry!
• Prefered EU
• World Wide: please ask

Best regards ...Carsten

I'm trying to identify a suitable replacement transformer for my Arcam Alpha 8 CD player, which was purchased back in 1996. Arcam's customer services has told me they can't assist, due to the product having been discontinued so long ago.

Is anyone able to advise on any of the following please?

1. Is replaceing the transformer a relatively straightforward DIY job?
2. What currently available transformer would be suitable and where can I buy it?

Thanks in advance! 🙂


Background:
My hi-fi is Arcam Alpha 8 integrated amp + Arcam Alpha 8 CD player + Acoustic Energy AE109 speakers.
The transformer in the CD player hums / buzzes when connected to mains power, even when the power switch on the front of the CD player is turned off (when powered on, the noise gets significantly louder). I would expect a quiet hum that's audible from 1-2 metres away, but this is a loud hum that disrupts quiet / silent parts of music when I'm sat 5 metres away, and was not present when the CD player was new. It is a mechanical noise from the unit, not noise coming through the speakers.
I'm keen to resolve this, as I'm otherwise very content with my hi-fi system and have no intention of upgrading it anytime soon. However, if it's not realistic to resolve this (without paying over the odds for an expensive repair), I would be more comfortable with buying a modern CD player than a 25+ year old Alpha 8/9, due to the risk of that old transformer developing the same problem and/or other issues down the line (e.g. leaky caps). I have no idea what I'd need to pay on the current market to get something of comparable quality that would blend in with the rest of my existing system.

Warning, I don’t know much about amp design. So, having said that….

Years ago I bought a cute SE 6bx7/6bl7 amp off of Ebay. It had a single 6j5 per side along with the output 6bl7. Also used some open frame output transformers. It was cheap but I liked it quite a bit. Gave it to a girlfriend so now no longer have it. I’ve read that the 6bl7 isn’t a good basis for an amp but I really enjoyed it and I’m thinking it would be cheap enough to replace. The power was sufficient for the speakers I have.

It was so cheap that I’m sure there weren’t any mosfet followers or anything. I assume that both triodes in the 6bl7 were paralleled for the output, would there be any advantage of using one of the triodes for something else? Do you think the 6j5 tubes were directly coupled to the output tubes? Is there a better way to design that? Thanks for any insight you can send me.

Hi. First preview of an upcoming pair of monoblocks, the Goldmund Telos 2500.
It is a long term project of mine, being working on that since the last 5 years, slowly putting together pieces of the design. I listened to a pair a few years back at the Montreal HiFi show and they sound superb! It was always a dream of mine to have a pair. The PCB design are my own, as well as the firmware. Never had a real Telos to look at. I compiled different schematics over the years, and saw the PCB silkscreen, so my parts location are close to the original. But since this is my own Firmware and control section, the rest of the amp has to match, and it is not an exact clone.

One of my problem was that the Telos use a processor and firmware to control the amp, and start, stop, switch between the different options (Mute, Analog or internal Dack, etc...) and safe shutdown in case of failure. This amp is very powefull, fast and can be prone to oscillation in some setup. So extensive protection is a must.

I wrote my own firmware using an Arduino Nano. My son a softawre engineer give me some help. The amp has sofstart (similar to Mark Johnson ACPRSS), multiple start option (Autostart on input signal, external 12V or dry contact). Mute function, etc... The small DSHP display controller, inclidng PIC code and PCB gerber came from this excellent site: HDSP 2000 Display Controller Board - Instructables

The Firmware is a State Machine, use two interrupts for the more critical faults (DC/HF & Overload) and stay in a loop after to check the remaining fault and control the amp (Mute, Digital/Analog switching, Dack Unlock/Lock indicator, etc) and the user interface (button, leds and optional display). Arduino controller is different from the original, use modern I2S interface bus and bus expanders. The Amp analog and Digital (controller) sections are completely separate and are isolated by opto-couplers. So no controller noise or dangerous analog supply levels can reach the controller.

It has more or less same interface as the original Telos: 2 buttons press power-on, 1 button for Mute, selectable Analog or internal Dac (optional), three leds for various indication (standby, Power On, Mute, Failure flash, startup sequence, etc...). I even add a small HP HDSP display module to display messages, such as Power-On, Firmware version, etc. It also display the heatsink temperature while in Mute. This small display is optional, and you'll need to get the difficult to source HDSP display. It is just nice to have since the amp is operating fine with just the leds display...

There are extensive protection and fault detection: Power Supplies Shutdown power Mosfet switches (as the original), Overload fault (using Current sensors, as the original), DC fault, HF oscillation fault, overtemp fault (an I2S temp sensor give in real time the actual temp) and speaker disconnect relay. I added a thermal AC disconnect switch in the main AC line as well as an extra thermal protection.

All these faults will shutdown the amp, a led will flash according to the fault code, and a message will be display on the display module. You need to power down completly the amp in order to clear the fault. Naturally the controller test for DC and Overcurrent faults at startup, so if a fault is still present the amp won't start...

The rear panel has Analog (SE/BAL) Input, Digital SPDIF In/Out connectors, ANA/DIG and Left/Right DAC switches, Gain selector rotary switch (-9dB, -6dB, -3dB, 0dB, +3dB, +6dB). It will also have external power On +12V or Dry Contact inputs, Chassis and Audio GND binding posts, and GND Lift switch)

Anyway this is just a preview, being working almost full time on this since th last 6 months (almost 3 months just to design the complex pcb). Presently I'm doing extensive testing, found all the pcb errors in my first prototype and finetuning the firmware. So far everything is working but I still have to check the DAC.

If there is enough interest I may offer this pcb set with controller firmware as a group buy... Kit will come with complete detailled BOM, PCB silkscreen, interconnect diagram, Spice model to look at the actual circuit behavior, voltage and current, detailled testing and startup procedure, step-by-step and per PCB. Complete kit has these PCB: Main PSU/Controller PCB, Front Panel PCB, Input/Front End PCB, Output Power PCB and a few smaller accesories PCB such as the I2S temp sensor, and optional smd to DIP op-amp adapter. The internal DAC PCB will be optional, as well as the HDSP display PCB with PIC controller.

As I said the internal dac may be an option, you can drive the amp directly from a music server, and operate in the digital domain up to the amp, as using JRiver and computer for example. The Amp has a SPDIF input and you can select what amp play Left or right channel. A SPDIF digital output then connect to the other amp. I'll make a set of DAC pcb for me, but I still need to test the prototype. Dac may also be available (all smd, very small parts design) so if you don't like smd, I guess you don't want it...

Here a few pictures. Prototype is working fine on my lab power supply, 470ma bias for 6 parallel Mosfets, 78-80ma per Mosfet (Exicon ECW10N20 & ECW10P20, selected part directly form Profusion, UK). This is a low power test, 2 Vac/1Kz into 8 ohms. Output waveforms are prefect, no oscillation, see waveforms. The output stage MOSFET are closely thermally coupled being mounted on a copper block, that is then bolted to the rear heatsink. The original Telos use the same arrangement, but thier copper block was gold plated. Mine is just protected by clear lacquer.

More to follow. Once I have a complete, runnning, assemble amp I'll update the thread...

SB

I'm building another SSE, and of course that means I have LOTS of questions! This time it's about TUBES. On my last SSE, which I used for a short time before selling it, I had EL34 tubes in there. Never swapped out with anything.
For this build, it might be fun to experiment with different tubes. I understand the 6L6 tubes can be used, maybe KT88, maybe others...
Is trying different tubes as easy as switching them out? Or do other modifications need to be made in order to switch from type to type?

Fully working pass b1 korg board, $50 shipped

Someone on Facebook was asking about the Danley BC subs, and I personally think that the concept is fairly straightforward, and it's come up on FB a few times so I thought I'd do a quick "brain dump" here.



On Facebook, I (sorta) joked that: "'Boundary Coupled' is just marketing speak for "the baffle is really big.'"

So let's elaborate on this a little bit:

First off, the primary reason that radiator has higher output on axis when it's on a horn or waveguide is because the waveguide takes the output from a radiator and constrains it into a narrower beam.

This is no different that now a light bulb can barely illuminate a room, but a ten watt diode laser can cut through wood:





A diode laser takes it's energy and focuses it in a point, a woofer in a baffle that is sufficiently small will radiate in all directions (spherical) and if you put a radiator onto a big flat baffle, the baffle itself will keep the energy from radiating backwards.

Next thing that we do is figure out "What is that frequency?"

Danley BC-218 measures five feed wide by five feet tall by 2.5 feet deep. That's a baffle face of 152cm x 152cm. The exit of the BC218 is NOT in the center of it's baffle, and that has an impact, but describing that effect is beyond the level of this discussion. (You can sim it in ABEC or VituixCad.)

This next thing is pretty important I think: Keep in mind that the radiation from the radiator has to wrap around the enclosure before it can radiate in 360 degrees. If we just looked at the front of the baffle, we could constrain radiation down to 224Hz. This is because the front of the baffle is 152x152cm and 224Hz is 152cm long.

BUT - once we include the sides of the enclosure, we're looking at radiation control down to 112Hz. That's because the additional thirty inches, on each side, increases the baffle size to 120 inches wide.

Now at his point you're probably wondering "what's the point of a subwoofer that "controls radiation" down to 112Hz?"

The answer to that, for the Danley BC Subs and Danley's B-DEAP subs that he made at Sound Physics Labs, is that they're really designed to be arrayed. That's why I didn't do a deep dive into the mouth location. The subs don't make a lot of sense when used in singles. Add a second BC-218 sub and you're controlling radiation down to 56Hz, easy.

The next step in this, is that once you place the sub on the floor, the floor itself increases the on-axis efficiency. This ALSO gets tricky, because the floor isn't a perfect mirror of the loudspeaker. But chances are good that you will be putting your speaker or subwoofer on a floor, so it stands to reason that you would want to leverage it to improve the performance of your speaker.

On a side note, if it's not obvious, you could avoid a lot of this by just cramming a subwoofer into a corner. But BC subs arguably are best outside or in a big room, where that huge baffle can constrain radiation. I think this is particularly important for festivals where you don't want the subwoofer to "bleed" into the next stage over, or the stage behind it.

I think it's also useful for clubs and the like, because it's controlled radiation reduces energy radiated into adjacent buildings.

Hello Everyone,

I am trying to modify a project my father was working earlier, the question I am having now is on local power rail bypass.
I know there has been a lot of discussion on bypass and I know bypassing at the cap bank is no no, but a good practice to have local bypass if the main cap bank is some distances (maybe inches) away.

I will be doing 2 PSU for each amp board, one to drive the output stage with a bigger PSU, and one smaller PSU to drive the input and VAS. Both PSUs are approx 12~15cm away from their respective power entry points on the amp board. Each power rail is 35VDC, from 25v transformer secondaries.

The bypass method I am using is have in mind is really a copy from an article from TNT Audio by Dejan Veselinovic. What I think is good is the RC right before the device.

Main questions I have are:
1. Should I also have the 220uF bulk filter cap for the PSU2 (driving Input stage and VAS)? Currently I have no plans to but I can still add in if that is a good thing.
2. Which is preferred (X7R SMD type or MKP box THT type) for the 100/220nF bypass as well as the 680nF RC filter? Their cost difference is really very small for DIY, and while X7R is smaller in footprint, I am doing double layer board so space is not really an issue.

Hope to get some feedback soon as I'll be having a one-week break soon, and will be a good time to make some progress.

Hello All,

Got a Boston Acoustics PV800 Subwoofer needing some help. I really like this sub and would like to save it if possible. I know that it is a BASH amp and that I have very limited knowledge and skills. I probably know the names of about 25% of the components involved and I know a guy who can solder pretty well. I'll give a description of it's behavior and what I know and and have done so far. Hopefully someone here sees or reads something here for a fix.

Plugging the sub to power usually results is a dim (about 20% of expected brightness) LED indicator. This is regardless of the subs power switch setting (on, auto, off). If the switch is "off or auto" you get dim red, if the switch in "on", you get dim green. This sometimes give a faint, shrill squealing type sound from the sub. When powering on to a dim LED indicator you always get 160V from the power supply board (see circled areas in pics). . . the board that receives the 160V will then always output ~12V (see circled area in pics)

When the sub gets plugged in and works, of course the LED behaves as it should. The one other obvious difference is that the board that was outputting ~12V is now outputting ~30V

When the sub doing the dim LED behavior, I can jump start the sub as follows. For about 4 seconds, I run a hair dryer on the left half of the BASH labeled board then plug in the power cable. Sub immediately comes to life. If I now leave the properly working sub plugged in overnight and everything get warmed up, unplug the sub then plug it back in. . . I get the dim LED fail again.

There is only one repair that I have done (and it didn't change the behavior). In one of the circled areas in the pics, there were two transistors that had their faces blown off, I had them replaced.

Thoughts anyone?

Thinking about using 1 or 2 of these on each side for a nearfield monitoring application, in between a TC9FD18 and NE19VTS. Crossover points likely 900 Hz and 2 kHz. Yes, would have them as 4-way monitors if this comes to fruition. Reason for these two drivers specifically is because they look pretty good and because I need the minimum size possible that is "lower" than a tweeter; I want to achieve, as close as possible, a point source on a flat baffle.

Any thoughts as to which of the two might be better-performing?

G'day Guys,

I am intending to use some 125x75 mild steel angle as a bracket to mount a Toroidal transformer on its side.

My local supplier has 6mm, 8mm, 10mm and 12mm thickness available.

12mm seems a bit silly. Its only a 300VA transformer.

Is 6mm going to be rigid enough?
10mm also silly?
8mm a happy medium?

Just go with the 6mm?

I'm planning a new build and going the route of full range drivers. Not sure if the new speakers will be OB or in a box. I was very interested in Lii at first, but in looking and reading I came across the Cube Audio drivers, especially the FC8 which is their least expensive offering. They look the part and reviews of their finished speakers are all very good. Has anyone used the FC8? I'd love to hear any impressions. I have a feeling even their cheapest driver will outrun the best Lii has to offer.

I've had a VPI HW-17 record cleaner for some time, but have always wondered if there was a way that could deliver better cleaning results along with less contact with the vinyl . So, after reading threads here and elsewhere about using ultrasonic cleaners to get the dirt off of vinyl, I thought I'd rig up my own unit.

I started with an ultrasonic cleaner that uses 60 KHz transducers. It was a little harder to find and a little more expensive than the typical 40KHz Chinese-made units, but the higher frequencies theoretically do a better job at cleaning the very small grooves of a record and there is less risk of damaging the vinyl from the cavitation. Those two points are a big advantage of 60khz units over 40khz units.

To rotate the records, I wanted to minimize motion in the cleaning solution. My target was a 4 minute cleaning time for the vinyl surface. Given that about 1/3 of the record is submerged in the solution at any moment, the math told me to find a 5 revolution per HOUR synchronous motor. Synchron makes such motors in almost any rph or rpm you could want. The 5rph motor yields a 12 minute rotation time. My plan is 1 rotation = 1 cleaning cycle.

I fashioned a spindle out of 9/32 W1 drill rod. It was was easy to machine a 1/8" diameter hole in one end of the spindle on my lathe to fit over the motor shaft (1/8" diameter).
The motor and shaft are mounted in place using an electrical connector box and conduit. The arm is mounted to the ultrasonic unit using L-brackets and pipe straps. The setup allows the motor and spindle assembly to be rotated up to load records, and then rotated down into the bath.
My spacers are 4" diameter, 1/2" thick cork rounds. [Oct 2012 note: I have since found different spacers, which are much better: I've ordered these from the UK: 110mm by 105mm tapered cork stoppers - they cover the record label completely and very little of the lead out groove. They are just a touch over 1" thick, which is optimal spacing.
No.37 Natural Cork Stopper 110mm from Just Cork No. 37 Large]

[Dec 2012 Note: I added a sintered bronze bearing and a bearing housing to support the weight of the spindle, records and spacers, and eliminate the bending moment on the motor shaft.]

I'll report back after I clean and play some vinyl. My first batches will use distilled water and isopropyl alcohol at about 7 to 1 [Sep 2012 note: I've since gone to a much lower concentration of isopropyl, about 50 to 1] , with a few drops of Kodak PhotoFlo. This solution, combined with the very slow rotation, will allow the liquid to drain off the vinyl surface very easily.
The cleaner can still be used for any items you'd normally put in an ultrasonic unit. It does a great job on some fairly intricate gold jewelry I've cleaned.
Photos below. Questions and comments welcome.

[Feb 2013 Note: I have built a second, sturdier design using a metal frame and hinge assembly that fits over the top of the Ultrasonic cleaner. Here is a direct link to the description later in this thread:
Version 2 of BB's URC
And here's a direct link to the post with the parts list for Version 2:
BB's URC Version 2 Parts List ]

Feb 2015 Note: I've built a 3rd version, designed to be assembled with fewer tools and be more adaptable to different cleaners. Description and pics for Version 3 start here:
BB's URC Version 3
Parts list for Version 3 reposted here: BB's Version 3 Parts List

Happy building.
Cheers,
BB
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Hi guys,

I know you all have tools that you use (and the creators of which are on this forum) and I certainly don't want to tread on peoples toes! But I have been creating a TL modelling application that I would appreciate any comments on.

So far it has all been theoretical and I have not had much chance to compare it to other models or real life enclosures, so a little bit of testing against known parameters would be useful.

Other than that, any suggestions/constructive criticism is always very welcome.

Kind regards,
Pete

leonardaudio.co.uk

P.S. This is very much in a Beta state, so be prepared for a lack of error checking...

I had a recent laptop crash, so I had to load MiniDSP 2x4HD software on my new machine. Trouble is, I couldn't find the old UI. All I could find was "Mini DSP Device Console," which seems to be complete crap. Does anyone know if the old tuning UI is still available?

I was hoping someone could help me out with telling me what measurements I should see with these transistors. Looking for VBE,HFE, and so on.

Time to lighten the load.

I have a set of Pass M2X PCBs along with the Edcor 600:15k autoformers and the five attendant driver PCBs as well as a pair of the XRK daughterboards. New, unused. $50 plus shipping.

I also have a pair of the Cinemag CMOQ-4HPC autoformers. These can be used in place of the Edcors listed above (though the PCB footprint is not compatible) as well as in other Pass DIY builds. These are PC mount, so a perfboard and perseverance will help considerably. New, unused. $65 plus shipping.

I also have a pair of 6” coaxial drivers from DIYSG. Details here. These are $100 each. Purchase includes cut bamboo baffles and PCBs for the crossovers. These would be a great bookshelf speaker or surround speaker project. Photos and project details at the link. Shipping across the country from the Bay Area is about $60 via UPS. New, unmounted.

I’ll add pictures soon and possibly more drivers.

I’ll split shipping with whomever buys the whole lot.

There has been so much ink spilled over the years about the DH-200 / DH-220 amplifier.
And I've had one for years - more or less stock and while it's always been a decent amplifier it's definitely showing its age.

I know that there are plenty of upgrades out there. Musical Concepts mods have been around forever but they're expensive. https://www.musicaldesign.com/Haf_pwrmods.html
Frank Van Alstine has been taking these apart for decades but he rarely does anything to Hafler amps anymore. But I'm almost certain his built amplifiers have borrowed a lot from early Hafler designs.
There's a few boards on eBay including this JFET input board kit. https://www.ebay.ca/itm/284376015343

None of them really turned me on because, well, there's nothing really written about these things. They're closed-source designs and the designers ain't talking.

Then I came across Bob Cordell's article in AudioXpress: https://audioxpress.com/article/you-can-diy-the-dh-220c-mosfet-power-amplifier-part-1-the-circuit
I was hooked from the second paragraph and onward where (gasp!) the schematic was revealed with no irony. Plus there was more information here: http://www.cordellaudio.com/poweramp/DH-220C_MOSFET.shtml and the article mentioned that PCBs were available on eBay. So I bought them and bonus (for me) the seller was in Canada, so no importation BS: https://www.ebay.ca/itm/225582185620

Good evening everyone 🙂
I wanted to know if anyone can help me with a Rockford Punch 60.2 trans.ana, I would need the diagram to know what model of diode is fitted on d2 and d3 as well as to be able to repair it 🙂

Hello,
I'm looking for a working RC-123 remote for my Denon PRA-1500 preamp.
Thanks
Damien

I just finished a few modifications on my Art Djpre II, and thought I'd share them with the DIY community.
The first thing I changed was the power supply.
Many owners of this unit report that it sounds much better on battery power, or as reported in this post it can sound just as nice with a good quality regulated supply.
Cheap upgrade for Art DJ Pre ii owners : vinyl
I looked at the one they suggested from Parts Express, but given that it is made by Mean Well, who to my knowledge only makes switching type supplies (which would introduce a lot of switching noise) I chose instead to build my own ripple filtered & regulated supply.
The original wall wart was 9VAC, which is rectified inside the chassis with small SMD diodes in a full wave bridge configuration.
The first filter cap is a 470uf, immediately after which the voltage is regulated down to 5VDC.
Since battery power improves the sound so much, my assumption is that everything after the regulator is of sufficient quality that little improvement could be made from there on.
So, I saw the 470uf cap as a good place to start.
The original is made by Junfu.
They are generally considered low grade crap, so I began the hunt for something better, and decided after reading probably way too much about the subject that an Elna Silmic II would be a substantial upgrade.

The first change was to replace the first filter cap C5 with an Elna Silmic II 470uf @ 25V.

The Elna is slightly larger than the original, but did fit with a slight bend in the leads.

The power supply I came up with is pretty straight forward, and has a nice clean output.

It should be adjusted to 12VDC.

I was a bit skeptical of the difference these changes would make, but listening tests confirmed what others have noticed.
Quieter, more dynamic, improved depth & clarity.

I could have quit at that point, but then I had another small thing to work out.

I am using the Djpre II with an Ortofon 2M Blue.
The inductance of this cartridge is rated at 700mh, which I confirmed measures 728mh with an inductance meter.
With the capacitance of the tonearm cable, interconnects, and the Djpre II internal loading capacitance of 100pf, I was getting a resonant peak at roughly 11.4khz give or take, which was readily apparent in listening tests.

This page has a calculator to estimate resonant peaking with various capacitance loads, and explains really well the effects of changing the cartridge load.
Hagerman Technology LLC: Cartridge Loading

So, it seemed pretty clear that I needed to shed every pf I could to get closer to ideal frequency response from this cartridge.
I tried low capacitance cables, which helped a bit, but it still wasn't low enough capacitance to get rid of that resonant peak within my hearing range.
I briefly considered going with a lower inductance cartridge like a Grado, but where's the fun in that?

I contacted ART and asked for a schematic, but they said that they no longer provide schematics for their current line of products, because they have had some of their designs stolen by other companies.

Since I was only looking to tune the input capacitance, I really didn't need the entire schematic, so I contacted them again and described my problem, and what I was trying to do.
The ART QC engineer consulted the Design engineer who both shared their knowledge of this circuit and helped me to get rid of that last 100pf load capacitance, which in turn got rid of the resonant peak (at least to my ears).

I would like to thank both of them for their help.
It was much appreciated.

So, here it is.

C20 & C23 are the 100pf cartridge load capacitors.
They stay across the input all the time.
C36 & C37 are both 100pf capacitors which are switched in parallel with the fixed capacitors (C20 & C23) to achieve 200pf loading.

Removing C20 & C23 gives you 0pf load on the 100pf setting, and 100pf load on the 200pf setting.

It's as simple as that.

Without giving away any of their trade secrets, I made the overly simplified schematic of the input loading circuit as a way to visualize the effect of removing C20 & C23.

Hello everyone,

I want to build this (plan below) bass reflex cabinet for the Cube Audio FC8 driver. This is my first attempt and I have some questions.

1. Are there any acoustic downsides to screwing the back panel in place so access to the interior can be maintained ?

2. There is a label on the side elevation drawing which says "This section might be filled with sand". What are the pros and cons of doing so, and what would be the process for filling / removing the sand ?

3. I have an oak floor which is laid on concrete. What sort of speaker feet would be best ?

Thanks in advance for any help,

Mark

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Front and rear coaxial 8"s (from JBL 328CT) on a sideless enclosure as shown- I'm currently running it as a front/back dipole (coaxes out of phase front and rear) but it's designed to allow for a "dipole/bipole" configuration where cancellation will be more like a pair of traditional open baffles firing front and rear. They are set up on top of subs rather than on the floor (as shown).

Dipole cancellation's pretty straightforward, either the "inside" of drivers cancel and the front and rear have an effective baffle width of the baffle width plus 1" (Added waveguide effective depth) plus 7.5" (1/2 the total system depth between baffles)

When run as "bipole dipole" effective baffle width is simply Baffle Width + .75 (1/2 of the 1.5" thick baffle) +1" (Added Waveguide effective depth)

I haven't had a chance to measure in the current setup, but I'm currently crossing at 140hz, which is probably an overly aggressive high-pass (could probably be lower), but I'd love to hear any thoughts people have on such a setup.

The coaxes are normally ceiling mounted with a shallow waveguide, my waveguide is somewhat improved, in that it closely tracks the cone profile and is slightly larger, deeper, and smoother than the JBL ceiling mount metal waveguide. This is important as the horn leverages the cone as the waveguide so that transition must be as smooth as possible.

I'd love to hear any thoughts- this is an experimenter system, regardless of the (rather ridiculous) effort required to create the waveguide. Naturally I have my own ideas for what might work in this highly configurable system, but I figure this is the best place for such conversations.

They must be busy as beavers putting kits together ( we hope ). Be nice if they offered a 90+ spl desktop speaker kit. Maybe just a baffle routed out for the drivers? That seems to be the missing piece.

I've been working on a single ended parafeed headphone amp that I've had for the better part of the past decade. Every few years I take it apart to try something new. Most recently, I converted it from 6S45Ps to 6E5Ps and can't seem to dial these new tubes in.

I've attached the schematic of the amp section and a photo of the amp. The power supply uses a big SumR toroid followed by a 6BY5 rectifier and LC filter (5H + 420uF MKP). The raw supply is shunt regulated. The regulator is a simple IXYS DMOS CCS with no cascode set to 120mA. The shunt leg is a high voltage MOSFET with 3 0C3 glow tubes spanning from the drain to gate to generate a 330V regulated B+ supply. All tubes are heated with AC, with the rectifier tube and signal tube on different windings.

The amp section is quite simple. The 6E5P has about 4V on the cathode and is biased to 30mA with a CCS on the plate. There's a 2k grid stopper, 10R on each cathode pin, 100R on g2, and I've experimented with plate stoppers but ended up taking them out. The tubes are on teflon sockets which mount directly to a small PCB, and the stoppers are 0603 thin film resistors that are physically no more than 2mm from their respective pins.

The issue I'm hearing is really strange. Certain notes seem to excite a microphonic resonance in the tubes right around 3.5k. As the volume is increased, the intensity and duration of the ringing inreases, too. Hi-hats just sound miserable.

I had a couple of hypotheses: either the tubes were oscillating at RF, making them more prone to microphonic ringing, or there's some junk sneaking in through the power supply. Here's a partial list of things I tried.

• Increasing all stoppers and adding plate stoppers. Bumping up the grid stopper to 20K helped just a bit, but now I don't manage 20kHz bandwidth.
• Converting the power supply to an LCRCRC, or a cLCRCRC where the first C is about 100nF. Currently, the three caps are in parallel with no Rs, and no small input cap.
• Elevating the 6E5P heaters to 50V (surprisingly, didn't impact 60Hz noise at all)
• Starving the 6E5P heaters to 6V to reduce gm
• Redoing all the ground wiring
• Changing the bias current from 40mA to 30mA per tube to reduce gm
• Adding input transformers
• Adding an EMI filter on the RCA input connectors
• Adding an EMI filter on the IEC power connector
• Trying out 6 different 6E5Ps, two different manufacturer stamps with different date codes. These all rang within a few 100Hz of each other.
• Adding a ground loop breaker between the circuit ground and IEC earth
• Removing the power supply regulator entirely
• Measuring with the inputs shorted (gave slightly lower noise than with RCA cables)
• Switching between a standard parafeed connection (primary returning to ground) and a WE parafeed connection (primary returning to cathode)

Here's a frequency response sweep with a 20k grid stopper. Every tube seems to ring within a few 100 Hz from each other. When I run the frequency sweep, you can hear the sweep through the tubes (and not through the transformers). Once it hits the 3.5kHz mark, the tube ringing becomes quite loud and continues for about a minute after the sweep is complete.



And here's the noise floor, with input transformers, taken before running the FR sweep. Note the peak at 3.5k and the rise in the noise floor centered around 7k. This measurement was also taken with 20k grid stoppers, and the rise at 7k was much higher with 2k in place.


I know the tube is well liked here. Any thougts on how I can get them to sound good?

I see these have been off the radar for awhile. I'm about to dive into a SA I have that has been out of action for too long. The last round a few years ago found some of the gold plated small transistor legs broke down. And had under the gold plating literally turned to dust. Causing them easily rip loose. Since then I have acquired a PSA parts unit so I'm headed back in. I've already worked thru the output modules and they are now up to spec. So the only known issue is the main motherboard which is the location of these transistors. This doesn't seem to be an issue with them all. So perhaps it's due to some past environmental exposure.

Nevertheless any recent service advice would be appreciated.

Many thanks in advance,
DD

I need 2, WELL MADE, 2.0UH coils spec'd for the new V5 version of the PeeCeeBee amp boards.

PM me with details.

Rick

Anyone know of a usb soundcard that works fine i Linux.USB for my Laptop.
Around 100$

Hi everyone. Was hoping to get some help diagnosing and hopefully fixing this amp. The amp blew a vintage MB Quart speaker. Very sad about that since it was one of my favorite speakers but that's another story. I checked the voltage on the right speaker terminal and it has 30v DC. From my research, it seems to be a bad output transistor. Any help will be greatly appreciated.

I've got a couple of QCC3008 modules that I just can't connect to via SPI (I keep getting an 'error detecting chip type' message in the WIN1.0.167 version of PSTool) and I'm wondering if its because they have the later type bluetooth module on them rather than the older BTM308-C. My USB to SPI interface is working fine on the older modules (8630), I've tried connecting SPI_En directly to 1V8 and 3V3 via a resistor. I can't even change the firmware as Blueflash doesn't recognise the chip.

This is the older type

This is the later ones I've got.

I was just wondering if anybody had had success connecting to these later type modules as in the Youtube video series from Dariee, he uses the older type and I can't find anything out about the later modules.

Many thanks.

I am planning to build a pair of 2 way bookshelf speakers. I have seen in some speakers that the tweeter is not aligned with the center of the front baffle. I understand that this is supposed to help with diffraction. Is positioning the tweeter closer to one side a straight forward benefit (while keeping it as close to the midwoofer as possible), or does it require other considerations to be worth it?

Dear all o have an akai AJ480fs tape recorder with 4 band radio .I bought it from a vintage collector .unfortunately the radio not working kindly help me with schematic diagram or some ideas .The radio Circuit is a bit confusing with its power supply.
A 220mf electrolytic cap is connected with 220 ohm resistor from a zener diode connected from 12 volt dc through 100ohm resistor the zener is grounded .but the +ve and -ve terminals of the cap is shorted with looping ground of mainboard .so when ever I am connect all cables across the cap no dc bias .when I checking with meter it's shows grounded .all the caps are tested ok
Kindly help
🙏

After a lot of reading about how to match transistor for the differential input stage in a amp, I came across this video which makes sense to me. So a constructed the circuit, but substitute the matched resistor with a multi turn pot instead. Also I used my old Wavetek signalgenterator for the square wave. After some tweaking with the oscilloscope I got it working. Had to use grandpas old analog scope though, cause my digital was way to noisy. I plugged in channel A at collector of one transistor and channel B at the other one, then subtracted B from A, to make the scope show the difference between them both.

The circuit seems to be working as it should. It takes about half minute or so for the current to stabilize after I change transistors. Toughing the transistor with my finger (of course I use tweezers) make the curves go way of. Attached are to pics with one properly matched pair I think, the other one not so good. Resolution is 2 mV per square.

My question is what is exactly I am measuring, Vbe of hfe? Or both? Seriously I am not shore. The transistor under test are close to saturation but there yet not, so hfe should matter. But since there is not a separeta and identical voltage source for the base, Vbe should affect the base current. Or, I am not sure...

Years ago I bought a Schiit Modi dac so I could play out of my computer directly. But BT seems to have improved greatly over the years. The BT on my Emotiva is quite good. Do any of you avoid BT preferring a DAC?

I recently finished a simple stereo tube drive stage with tube regulated power supply. Aside from a 56hz hum (grounding I assume) it has a consistent periodic pop at 560 hz, and a regular (on ~10 seconds, off 10 seconds) digital buzz/ whine at 5600 hz. Any ideas? I tried different tubes but same result.

I was trying to set up an xover sim in Xsim and get this error trying to input component values. It happens in every field. Anyone have a clue whats causing this?

Hello, I have a pair of older RS12 PA Speakers from Samson. They are about 20 years old. The manual says they can "be stand mounted via their standard 1 3/8-inch speaker stand receptacles". I purchased Samson LS50P speaker stands which have standard 1 3/8" pole adapters, which are round, like a cylinder. The RS12 speakers have hexagon-shaped pole mount holes. The posts fit in the holes, but are tight and a bit difficult to disconnect. Here is a photo of the pole mounts:



Am I doing this correctly or are there different pole adapters for the hexagon-shaped holes? I looked and I see no mention of adapters like this, but maybe they are just too old?

I contacted Samson, but the answer I received seemed a bit lacking. They said "It must be very old. The new units are very different. I don't think you are doing anything wrong. It should be tight, but not too tight."

Does anyone know if this is just the way it is and that I am not doing anything wrong?

I appreciate any info. I'm just a hobbyist, but wanted to get this correct.

Thanks.

Hi all.

What sort of considerations need to be made with swapping one inductor for another in terms of gauge? I would like to replace a 0.3 mH 18 AWG inductor with a 0.3 mH 15 AWG inductor. The reason for the switch is that I want to try the Jantzen Audio litz wire inductor (https://www.parts-express.com/Jantz...itz-Wire-Air-Core-Inductor-255-908?quantity=1). Would it pose any issues to swap out the air core inductor (https://www.parts-express.com/Jantzen-1313-0.30mH-18-AWG-Air-Core-Inductor-255-218?quantity=1) for the litz wire inductor?

Thanks!