Does anyone know where I may obtain the schematic/circuit diagram for a Grampian AF100w amplifier type 6642.
It is a combined transistor mixer amplifier using qty 4 2N3771 transistors in the output stage. It appears to be ex military as it has the broad arrow marking on the front panel.

hey, i want to design a subwoofer and i am thinking about the voice coil now. i have this question:
i have read on this forum that for paralel connection, for discusiion, 0.5mm wire x 100 meters is 8.7 ohms. 0.7mm x 200m is 8.9 ohm

parallel connection increase curent while lowering resistance in half, if 2x100m wires used, and in series increse the resistance wile BI stays the same
this seems counterproductive, it has the same effect as driving the single voice coil more without the added mass. maybe i am wrong.
the 0.7 wire would be a better solution ? but why? and how? this i dont know. i undertand that BI doubles with the increase in lenght

Dear friends,
I did this before, adding an SPDIF to a second or third generation,
Sony-based player, using a Ti DIT4192 transmitter.
See this link how I did it with a Sony-based Nakamichi OMS-5EII 17 years ago (Really? Gosh!)
The Nak still plays my CD's every day!

Everything seems to be there in the Sony CDP-101 to achieve SPDIF-Out:
Data / Bitclock / R-L Clock to feed a DIT4192 for converting to SPDIF.
BUT:
The DIT 4192 needs a standard 19.9344 mHz frequency.
Normally no problem, as players with Sony circuits have a divideable of this frequency on board.
As one example, early players used 4.2336mHz (1/4) or 8.4672mHz (1/2), directly provided by a crystal.
Also 19.9344 mHz became very quickly common, or later multiples of it, like 67,7376 mHz.
So a Flip-Flop can be used to derive 19.9344 mHz from the mentioned frequencies and as far as I know
4.2336mHz and its multiples are a must to make a player work.
But being a first generation model, it looks like the Sony CDP-101
does not use a crystal with any of those frequencies.

The service manual
https://elektrotanya.com/sony_cdp-101.pdf/download.html

states the Xtals X501 and X502 are 8.6mHz and 35.022mHz - both frequencies are not multiples of 4.2336mHz
So I assume the base frequency is generated somewhere in the circuitry using PLL.
No hint in the service manual that 4.2336mHz exists (again, AFAIK it must) or where to measure and where grab it.
Does anyone know where 4.2336mHz can be found in this player?
BTW, the CDP-101 should trick audiophiles - there is damping above 15kHz and a delay between channels - it makes the CDP-101 sound "bigger".
All the best,
Salar

Hi,
I'm looking at options for a small near-field desktop speaker options, mainly for low listening levels or medium, not looking into shaking the house, and I want a small speaker / baffle so it doesn't take too much space in my desk, right now I'm looking into two options, both of them will be run with a sub-woofer, the Voxel mini sub by Paul Carmody or maybe one of those 8" kits from Parts Express with a DSP enable amplifier

The speakers will be placed relatively close to the back wall, around 20 cms, so I'm leaning towards design that are not affected by the close wall too much

Option 1
Mark Audio Alpine 7MS in the Sealed Single Surround box, it is not explicit, but I suppose that Scott had been involved with the design of a lot of the plans in Mark Audio site (the 18 mm multiply recommendation sounds familiar), so I trust the design

Option 2
This random project in Parts Express gallery of a miniature open baffle speakers, it seems simple enough and the guy who design it sounds like his know a little bit about speaker design

Something that I always wanted to try is an open baffle, but for now (and a few years), I won't have space to get one of those cool looking, 2 15" woofer OB designs that are loved around here

And I also like the Mark Audio option because is as simple as it gets, but won't satisfy my OB itch

What are your thoughts about the miniature open baffle project?

Thanks
Alex
Edit : Grammar Fix

HI,

Could you please provide your opinion/expertise on the following:

I recently bought a ca. 33 + year old, but fully functional Bryston-4B ST AMP (which apparently was updated mid 2004 by Bryston, Canada to ST specs from a mid 1990's Bryston-4B NBR) .
See attached the Bryston 4B ST schematic.
I plan to refurbish this Amp at some convenient time; I'm now happily using it.

I quickly checked the power supply capacitors (8 X 5600 uF 100V 105 degC Nichicon) and they are still OK (Capacitance, ESR).

However, there are some 2 Tantalum capacitors, C18/C19 (1.5uF 35V), per channel used on +/- 33V stabilized Power rails (stabilized by a R / zenerdiode circuit) .
There is hardly any margin for Voltage overruns, to which tantalums react catastrophically (total shortcircuit, sometimes fire).

There have indeed been reports of catastrophic failure (total short-circuit) of those tantalums in this very circuit, resulting in the blowing of the main power fuse of the affected channel (Full dual mono construction).
https://www.audiocircle.com/index.php?topic=184960.0

Personally I have experienced such short circuits of tantalum buffer capacitors in power rails in 1970's/1980' Tektronix Scopes and REVOX / STUDER tapedecks (also no WV safety factor was employed in those designs.)

My question:

Would (in my Bryston 4B-ST) the blowing of the main power fuse for that channel be the only consequence of a failed +/- 33V power rail ( caused by a short-circuited buffer tantalum capacitor (1.5 uF 35V) C18 or C19), ??
or
could it perhaps lead to much more severe consequential damage: e.g. destruction of some near unobtanium TO3 (BR6521/22) Power Transistors in the TotemPole circuit?

I have not enough electronic skills to assess what would happen if one 33V power rail would die, as a result of a totally short circuited tantalum buffer capacitor C18 and or C19).

I would welcome your advice!

Cheers,

Martin

BTW

I plan to replace the tantalums by 1.5 uF 63V WIMA MKS2 film capacitors, (7.5x5 mm), which (just) can be accommodated on the PCB.
(I have used those WIMA's with good results in similar applications: e.g. REVOX A700, AKAI GX-630D Tape Decks).

Hi all,

I've recently bought a Peak atlas DCA Pro transistor tester and after playing with it for a while, I thought I'd have a go at tweaking some LTSpice models based on actual measurements. I've started with the KSC1845 / KSA992, since I have a bunch and they seem to be popular around these parts.

What I've done is based mostly on Bob Cordell's superb book "Designing Audio Power Amplifiers" and various DIYA contributions from Keantoken, Andy_C, Dave Zan and many others to whom I'm forever grateful for sharing their knowledge. Please note that this is my first attempt and I'm far from an expert, so the usual disclaimers apply: as far as I can tell, the models are much closer to reality than the stock ones (*), and so far they've worked fine in all the various simulations I've used them in, but I'll take no responsibility if using them sets your house on fire or something. Comments and corrections are of course welcome.

I don't want to make this first post too long so I'll give more details later (of course Bob's stuff is published material so I'll just go into things he doesn't cover or I've done differently), just a few initial comments to get things started:

- At the moment I have 10 x KSC1845 and 15 x KSA992. First I took a quick hFE / Vbe measurement of all of them and picked the ones closest to the average to measure in more detail and base the models on. They are both gain group F and have an hFE of around 400.

- As you can see, both have quasi saturation. It is well known that LTSpice's qs modelling has its problems, some of which I'll go into in more detail later. fT modelling in particular is directly affected by qs, and in the case of the KSC1845, so much so that it's impossible to get an fT curve that peaks where it should. For that reason I've also created a model without qs, which could be useful in cases where bandwidth, phase margin, etc. are more important than qs.

- It's frustrating that datasheets rarely (if ever) give any useful info about reverse characteristics, but I always assumed those parameters wouldn't matter much in the usual circuits. Then one day I modified by accident ISC in one of my models and the forward curves, the qs region in particular, changed quite a bit. I came up with a little trick to make the DCA Pro plot reverse curves, so I've had a go at tweaking those parameters too.

- Where neither the datasheet nor my measurements gave me useful info to adjust some parameter, I either left it at its stock or default value, followed Bob's very useful rules of thumb or just made an educated (I hope) guess. I realize that some things require building a specific measurement rig (the DCA Pro has its limitations) but I wanted to see how far I could get with what I have.

So, without further ado:

.model KSC1845 NPN (
+IS = 52.5f NF = 1.0 BF = 408 VAF = 150
+ISE = 4f NE = 1.5 IKF = 0.8
+RC = 0.28 RE = 0.15 RB = 40 RBM = 4.0 IRB = 250u
+ISC = 1.9p NR = 1.0 BR = 15 VAR = 20 NC = 1.3
+CJC = 4.8p VJC = 0.6 MJC = 0.29 TF = 149p VTF = 4.0
+CJE = 26.5p VJE = 0.73 MJE = 0.162
+RCO = 105 VO = 2.2 GAMMA = 1.6u QCO = 2p QUASIMOD = 1
+EG = 1.181 TR = 10n XTB = 1.728 )

.model KSC1845NQ ako:KSC1845 (
+RCO = 0.0 IKF = 0.39
+CJE = 31p TF = 418p ITF = 68m XTF = 18.7 )

.model KSA992 PNP (
+IS = 48.3f NF = 1.0 BF = 395 VAF = 65
+ISE = 0.5f NE = 1.5 IKF = 0.25
+RC = 48m RE = 4.4m RB = 25 RBM = 2.5 IRB = 3.8m
+ISC = 1.8p NR = 1.0 BR = 5.9 VAR = 12 NC = 1.3
+CJC = 7p VJC = 0.6 MJC = 0.32 TF = 365p VTF = 4.0
+CJE = 25p VJE = 0.855 MJE = 0.4404 ITF = 0.75 XTF = 1.13k
+RCO = 55 VO = 3.0 GAMMA = 490n QCO = 300f QUASIMOD = 1
+EG = 1.16 TR = 10n XTB = 1.285 )

KSC1845NQ is the one without quasi saturation. See attached simulated (top) and measured (bottom) Ic vs Vce curves. More to come...

(*) https://www.onsemi.com/pub/Collateral/KSC1845.lib
https://www.onsemi.com/pub/Collateral/KSA992.lib

It occurred to me, when building compact bookshelf speakers, every mm3 of cabinet volume is crucial to bass response. Every CRT on the planet has been confined to a land-fill. Shouldn't we take a hammer & chisel to that extra magnet?

Do I:

1. connect it to ground but only on 1 side? (which side?)
2. connect it to ground both sides?
3. leave it unconnected?

Thanks for the help.

Can someone please double check their own TSPs they measured with the factory specs on the 8NDL51 midbass? Using Clio and DATS V3, measured Qts is close to 0.5.

Those above results are rather high, plus a few other B&C drivers I have on the shelf also check higher in Fs, Qms, Qes and Qts. Do they perhaps measure at higher voltages or are they just that much off.

I understand there's break in required but even after playing a low frequency warble sine through it at just under xmax didn't change it much either.

I want to model some enclosure designs for the driver in ported and sealed boxes. I plan a 3 way with Scanspeak D7608-9200 and Bliesma T34B.

I have a friend that is about to have triplets and trying to trade and sell off his gear while also downsizing. Almost a year ago after hearing a dual mono F5 I built and loving the sound, he went and bought a Threshold 4000a that had been restored/recapped with XLR inputs on the back.

I am working a trade deal with him now to help him get rid of some of his gear but I would like to try to find out who the repairs were done by as he did not know.

Would there be a way to look inside and know if Jon had his hands on the unit? And which current amp in the DIYAudio store does the 4000a sound most like? I have built an F4, F5, F6, Aleph J, M2x and Amp Camps.

I have a pair of YG Carmel speakers running off F4 mono blocks and a Balanced BA3 and would like to try out the Threshold.

Selling a nice pair of PURIFI PTT6.5M04-NFA-01 medium driver
perfect working

600€ shipping included for E.U

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I made this turntable many years ago and I decorated it with lights to look like this. Do you have a friend you like?

Howdy, I'm looking for some help if possible. I need to replace a Toshiba TC9163N integrated circuit. I've located both TC9163N as well as the TC9163AN variants.

I believe the N stands for the dip package. But I've just spent over an hour trying to figure out what the difference between the N version and the AN versions are. The datasheets don't mention what the "A" stands for.

Can I replace the N version with the AN version?

Any help would be much appreciated!

Thank you

Being curious to see whether the 19ish-dB gain it produced was truly necessary, I decided to experiment by changing the configuration of my Aikido preamp from line stage to cathode follower.

I had thought I'd read how to do this at some point, but I was unable to google-fu any particular details when it came to it. Looking over Broskie's original ACF manual indicated it'd be relatively simple conversion, so I offer the process up here in the hope that it helps anyone in the future.

More importantly, it'd be much appreciated if anyone could confirm that what I've done here is actually correct and not a magic smoke generator.

Comparing the two schematics shows the ACF substituting the triodes, cathode resistors and grid stopper from the gain stage of the Aikido for a capacitor and two 1 megaohm resistors.





My assumption is the ACF resistors R2 & R5 are required to reference the signal AC to half B+, but admit I don't know to what end. Also a mystery to me is the purpose of the input cap. DC blocking? The cap currently in use is 0.1uF, with the manual specifying any value up to 1uF can be utilised.

Adjusting the Aikido schematic to match the ACF, but allowing for the least amount of tinkering with the PCB, the cathode resistors were retained in anticipation of their resistance making negligible difference in conjunction with the new megaohm resistors being fitted.



Because my Aikido board is the 9 pin version I was able to insert the new resistors directly into the tube sockets, connecting the plate pins to their respective cathode. The resistor leads need to be about 1mm thick to fit securely.

The grid stopper resistor was (unnecessarily?) desoldered from its pad on the input side, and the new capacitor soldered directly to the grid leak resistor at one end with the other lead placed into the top triodes grid pin socket.



Initial listening suggests that although the ACF configuration is fine for most listening situations there is now little headroom for particularly quiet material, while the usable adjustment range on my Khozmo attenuator has reduced quite a bit.

Ideally a measure of gain may be my preference but not the full amount the 6N6P tubes I've been using provide. Around 6dB would likely be plenty. My amp is a DIY Aleph J - 20dB gain, 1.5V input sensitivity.

The other noticeable change is that the noise floor seems audibly lower, probably to no surprise.

It was used in Cambridge audio C500, A500 and other entry level gear. I just need a gearbox so it doesn't matter what value of the pot is.

I was building small panels for my drivers using sheets of aluminum (4mm) and Richlite (8mm). The adhesive I used was 2 component urethane (Loctite UK U-05FL) which supposed to have some viscoelastic properties but it comes only in 50ml cartridges. These panels are quite dead, more than a similar panels with Richlite and baltic birch plywood and both versions obviously much less resonant than plywood (including bamboo) alone.
Searching for adhesives for CLD I found often recommendations for green glue (tried it myself) or Swedac. These are water based products and work with drywall or wood derived panels but never cure with nonporous materials. Other recommendations are caulks like for instance Weicon flex 310 PU but thesis cure through air exposure and will cure only maximum 25mm in nonporous materials.
VHB tape would work but gets expensive for larger surfaces and I would prefer adhesives for assemblage. Also I like to avoid adhesives which are available only in large containers like Decidamp DC30.

dear forummembers,

I have several Philips late 1920 and 1930 radio's.
Often do these tuberadios have and 506K or 1801 or 1805 rectifier tube.
But these tubes are beginning to end up out of stock.
Or really expensive $100 or more.

At this moment an AZ1 tube can be used to replaced them.
But if everyone usses that tube, soon or later these are also out of stock.
So i think it would be usefull to make a drop in replacement.
So i have done some searching on the internet, and have found the following replacements (see attached files).

but now i am wondering of these replacements are going to work fine.
And if this affects the lifespan of the other tubes.
Because a vacuum tube ractifier builds the high voltage over a period of time,
where these diodes are goning to directly give high voltage.

Is there somebody here that can give me some good advise?

Hello.
I'd like to buy one Rubber surround for ScanSpeak 18W/8531G00
Does anybody has any available?

Hello,

I am getting rid of a broken subwoofer. It is a neat design, and a skilled person would be able to get it working again. Model is Blueroom Bass Station subwoofer in silver. When powered it produces a loud hum. I replaced the chip amp and supply capacitors in it once, and it worked for a while before it broke again. Chip amp is ST Micro TDA7294V available at Mouser. It might need more trouble shooting to see why the chip amp died. Will ship in original boxes. I am the original owner and purchase it new back in 2003. Selling for shipping cost. Item weighs 31 lbs shipped and box measures 17 x 17 x 24 in. I am in USA zip code 37919. No promises and no refunds. Send me a shipping label (or money to cover shipping) and it is yours.

Hello,

I should have found a pair of CHP-70.2 at less than half of their normal price.
I would like to know which easy build I can do with them.

I've found those that seem quite easy:
https://frugal-phile.com/boxlib/pensils/Pensil10-2-map-211010.pdf
https://frugal-phile.com/boxlib/pensils/PensilP70s3-map.pdf
https://www.markaudio.com/wp-content/uploads/2022/09/CHP-70.2-vented-box-standmount.png

What to expect from those cabinets?
Something else that can be easy to build and well sounding?

Thank you in advance,
Roberto

Good morning:
I'm back with the box design for my Fostex FE206NV.
Generally, the same boxes are recommended for the Fostex FE206NV as for the Fostex FE206E.
There is a substantial difference between both speakers.
FE206EN has a Qts of 0.19. FE206NV has a Qts of 0.26 which makes them more suitable for Bass Reflex boxes.
For this reason I will opt for an MLTL.
I was studying a design by the GREAT Martin King for a Lowther model that he later used, just changing the tuning of the box, with Fostex FE206E and Fostex FE207E.

http://www.quarter-wave.com/Project04/Project04.html (Lowther)

http://www.quarter-wave.com/Project05/Project05.html (same box for Fostex FE206E and FE207e)

The Qts value of the Fostex FE207E is identical to FE206NV, they only differ in the Fs (39hrz vs 44hrz).

Could I use the same box design for my FE206NV, turning up the tune a little?

I have done the simulations with BASTA!

Unfortunately I don't know how to use Hornsteps, could someone do the simulations for me with said software?

Thanks from Argentina and sorry for my english.
Christian

This DAC has features that I was looking for - Excellent review and measurements at ASR, LDAC codec, volume control with remote, selection of inputs, no headphone amp, etc..

Here is the inside for anyone that might be interested! All comments welcome, especially from DAC designers. Thanks!

The switch is an Elma four-wafer bought from Don Audio. All resistors are Susumu thin film 0805 SMD 0.5% 25PPM, except for R1, which is 0.1%. The switch wafers are made for through-hole resistors, so the SMD resistors have been soldered across the circular pads. Solder is Cardas quad eutectic. The audio taper is taken from a resistor list to be found on the Goldpoint website. Included is a spare resistor of each value.


Please note that the switch bushing is of the new kind. It has two flats and is intended to be inserted into an appropriate panel opening to constrain the device from rotating. There isn’t the familiar tag that slots into a hole in the panel as in older types. The shaft has been cut and drilled (not very well) to accommodate a coupling (included). Never hooked up to any circuit.


€80 incl. postage to UK and EU only.


PayPal preferred.

Got my parts from the store for WLS. The markings on the high output transistors don't match anything on the schematic or in the BOM. I tried searching on the numbers on the transistors themselves and that didn't return any results.The transistors that came in the kit:

239015 C004B
231031 A004B

Which ones are Q8 and which ones are Q10?

Hi guys, I just bought a CounterPoint SA-1000 preamp and can't find an owners or service manual anywhere. Does anyone have one? I am willing to pay if needed.
Thanks in advance, Nut

Sorry recently got done building my second pair of the CSS Criton to 2TDX speakers. And they all sound great but somehow congested a little bit so it took my you Mike and I measured it from different distances and it seems there's a spike at 60 hz I was thinking maybe I didn't wire the crossovers correctly because actually used different parts than the supplied ones I reopen the speakers and everything looks fine The values are all correct and it seems if I pull them away from the wall it's a little bit better but still there's a spike at 60 hz what could be causing this? Could it be their room that's the only thing I can think of is it that bad should I worry about it any input from more experienced folks would be greatly appreciated. Below is a measurement from 20 to 20,000 kilohertz

Hi,

Has anyone tried to replicate the Antony Gallo baffle-less woofer?
https://6moons.com/audioreviews/gallo5/ref31.html

I like its simplicity in design and it seems a aestetially good companion for the Blanda-Gronsaker speaker Dave designed for me.

Thanks anyone,
Roberto

We just got a limited time access to GitHub copilot and copilot chat. It’s a lot “smarter” than I thought it would be. You still need to know how to ask a question and what questions to ask, but it will spit out very usable code.

This is the one technology that has made me rethink a lot of things.

Wanting to try full range speakers. I currently have a 14L bass reflex box which I will use at least as a test bed. I am looking to spend $60 for the pair. I dont like vright speakers with "detail". CHN70 for example seems to bright witb the peak above 10kHz. Considering:
CHP70 - seems ideal for a nearfield
Pluvia or Alpair - might be a stretch on the budget?
Something else I'm missing?

Oh BTW in Arisona.

Dear supporters,
I woluld like to have more gain from my Aleph 2 monobloks.
I know that single ended connection give us 26db gain but rest of my equipment is balanced, and that‘s the only way I’ll go.
Please suggest….
1. maybe good preamp (Aleph P1.7 or other)
2. …or maybe (I don’t know) I could play with 10k input resistors (lower values)
3. …or something else 🙂

Tnx a lot
Tony,

CD tray door won't stay closed. I am trying to locate the tray switch to see what is going on. Where is it located and how do I get to it? It is not shown anywhere in the service manual. Thank you.

Hi, Im looking to build a 2 way speaker similar to the Harbeth 30.2. I know the tweeter it uses and I know the woofer is proprietary and can not be purchased. What 8 inch woofer will provide that smooth forgiving sound? I assume it will need to be a plastic/composite cone. Suggestions are appreciated. TY.

Looking for a couple of 1.5mH inductors. Foil 12AWG or regular air-core 10AWG.

Thank you

Want to Buy: Looking for a very good condition, accurate, Tektronix 2252 Oscilloscope with a higher serial number that starts out with B022 or above. Willing to pay up to $625 for a really good scope. (modified the "starts with" number from my previous posting) I'm hoping that someone in this forum has one they are no longer using. pls send me contact info and photos if possible.

Looking for a very good condition, accurate, Tektronix 2252 Ossciloscope with a serial number that starts out at 2400 or above for working on my preamps and amplifiers. There not easy to find, so I'm trying this group hoping someone out here has one they are no longer using. pls send me contact info and photos if possible.

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Due to file size restriction of maximum 20 images that can be uploaded, only the document text and the first Figure 1 is displayed.
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History
* These Acoustat Model 2 Slimline Series electrostatic loudspeakers with Magne-Kinetic Interface MK-121-2, serial numbers 104333 and 104336 I purchased new in 1980 from Straight Gain Electronics, Toronto ON.


Figure 1. Acoustat Model 2 home setup - photo taken October 2023 after restoration.

• I was extremely pleased with the sound quality of these electrostatic loudspeakers throughout 20 years of worldwide assignments in Canada, Japan, UAE and UK, beautiful sound no matter where they were setup. Sadly, I had to put all my audio equipment into storage in 2001 due to shortage of living space.
• Early 2022 brought my Acoustat Model 2s out of storage and powered them up for the first time in 20 years, and although the speakers were still working and usable, they needed considerable work.
• My goal was to fully restore these speakers to their original (or better) condition, while keeping their external appearance original.
• Having no experience in repairing an electrostatic speaker, I proceeded cautiously with this restoration over 1 1/2 years.
• One advantage of a long-term restoration project like this, it allowed me to evaluate step-by-step the individual improvement in sound quality and reliability that each upgraded or replaced component contributed.

Initial Symptoms
a) When powered up, annoying hum noise coming from both interfaces.
b) "Snare drum" sound whenever speakers are moved.
c) When powered up, persistent clicking noises from the speaker front faces.
* Issue a) is documented in this report, while issues b) and c) are independent of the interface restoration discussed here and will be addressed in future postings "Acoustat Stator Wire Repair: Hints and Lessons Learned", and "Acoustat Diaphragm Heat Shrinking: Hints and Lessons Leaned" - under preparation.

Observations before Restoration

• Removing the interface top cover plates revealed some problems inside.
• Oil had leaked out from the high-voltage audio capacitors, leaving a sticky goo on the inner surface of the chassis (Fig. 2).

Figure 2. Interface 104333, oil leakage from discoloured right-side capacitor - board displayed upside down to show capacitors.

* Discolouration, corrosion in the low-frequency internal wiring (Fig. 3).
Figure 3. Discolouration in low-frequency wiring conductors - sheath pulled back for clarity.

Restoration of High-Voltage Board

• With oil leakage from the high-voltage audio capacitors, priority was to rebuild the high-voltage board. No work had been done to the high-voltage board since these speakers were purchased new in 1980.
• To better understand the component circuitry and layout, circuit diagrams were created for the original 1980 configurations, high-voltage section (Fig. 4) and audio section (Fig. 11).

Figure 4. High-voltage circuit, original as purchased new - 1980.

Figure 5. Interface 104336, original high-voltage board before rebuilding.

Figure 6. Step 1, high-voltage ladder components replaced during rebuild (replaced components coloured in blue).

• Original diodes D1 - D5 and capacitors C6 - C10 on both boards were tested out of circuit and although nothing untoward was found using a low-voltage DVM, these parts were replaced with equivalent or better rated components (Fig. 6).
• On one of the boards, resistor R5 would go intermittent open circuit when lightly pushed. While this did not appear to affect operation, resistors R5 on both boards were replaced with modern components.
• Already just by rebuilding the high-voltage boards with new components the sound quality became clearer.
• Next step was to try and improve the high-voltage bias circuit's storage capacity by adding a 0.01 uF, 6 kV WIMA polypropylene capacitor at the output of the capacitor-diode ladder (Fig. 7).

Figure 7. Step-2, high-voltage polypropylene capacitor added to high-voltage ladder (new component coloured in green).

• Adding this one polypropylene capacitor to the high-voltage ladder produced a noticeable improvement in sound quality, less graininess but more remarkable was a substantial improvement in the bass frequencies delivering more "punch". It really surprised me.
• Based on the sonic improvement from the addition of this capacitor, I decided to add a second 0.01 uF, 6 kV WIMA polypropylene capacitor to the output of the capacitor-diode ladder (Fig. 8).

Figure 8. Step-3, high-voltage polypropylene capacitors added to high-voltage ladder (new components coloured in green).

• Adding this second polypropylene capacitor to the high-voltage ladder resulted in only an incremental improvement to the sound quality, suggesting that the first capacitor on its own made the biggest impact and was probably sufficient. Nevertheless, I left the circuit as is with both WIMA polypropylene capacitors connected (Fig. 9).
• Safety! As others have kindly commented, these added capacitors hold their high-voltage charge for considerable time after power has been disconnected. Recommend waiting 24 hours after powering off before attempting work on the interface.

Figure 9. Bottom side of rebuilt high-voltage board (added 1st capacitor in centre, added 2nd capacitor at top-left).

Figure 10. Top side of rebuilt high-voltage board, showing 1st capacitor ground wire (Black), 2nd capacitor positive wire (Red).

Restoration of Audio Circuit

Figure 11. Audio circuit, original as purchased new - 1980.

Figure 12. High-frequency input enhanced with added capacitors (blue colour) - 1982.

• After the input capacitor enhancement (Fig. 12), no other work was done to these electrostatic speakers between 1982 and 2022.
• While the original 5-Amp slo-blo audio input fuse gave no problems, based on the recommendation from Andy Szabo on the diyAudio site, for safety I changed to a 3-Amp slo-blo (Fig. 13). Pleased to report no issues using this lower rated fuse, even at high sound volumes.

Figure 13. Final configuration of audio circuit, 2023 (component changes coloured in blue).

High-Voltage Audio Capacitors replacement
* The original high-voltage audio capacitors that leaked oil I replaced with 0.01 uF, 6 kV polypropylene capacitors (FKP1Y021006F00JSSD, WIMA). While the DC voltage rating of these capacitors is 6 kV, I was concerned about the lower AC voltage rating of 700 VAC RMS (Fig. 14).

Figure 14. WIMA high-voltage capacitors, type FKP1Y021006F00JSSD

• To double the voltage rating and achieve a wider safety margin, capacitors C4 and C5 were configured as a set of 4 (total 8 for one board) in a series/parallel configuration (Fig. 9), providing 0.01 uF with effective voltage rating of 12 kV DC and 1400 VAC RMS.
• With these new polypropylene capacitors installed in the audio section there was a noticeable improvement in sound quality, clearer signal with reduced distortion.

Implementation of C-Mod
* Following the detailed circuit documentation (AJS 6-03-2003) described on the diyAudio site by Andy Szabo, I replaced the high-frequency input capacitors with the following types and quantities (Table 1). Fortunately there is adequate space within the MK-121-2 interface chassis for mounting all components.

Table 1. Description of WIMA polypropylene capacitors used in the C-Mod.

• These WIMA capacitor voltage ratings are not critical, 100 VDC / 63 VAC rated capacitors are sufficient.
• To minimize transmission of vibrations with the metal chassis, the base and side of the WIMA capacitors were isolated using foam sheeting (Fig. 15).
• The original 6-ohm potentiometer was retained, adding a 10-ohm 50W metal clad resistor to achieve a combined resistance of 16-ohms.

Figure 15. C-Mod with WIMA polypropylene capacitors and 10-ohm 50W metal clad resistor - before Low Frequency repair.

Figure 16. High-voltage board temporarily removed to show fastening of power resistor - before Low Frequency repair.

Low-frequency Circuit Updates
* Although both original 1-ohm 10W power resistors tested fine, as precaution I replaced them with new 1-ohm 20W bifilar type (Fig. 17).

Figure 17. Original Huntington Electric 1-ohm 10W resistor (top), Mundorf MResist Supreme 1-ohm 20W resistor (bottom).

• The corroded low-frequency wiring was replaced with new Oxygen Free Copper (OFC) speaker cable that I had spare from another project (Fig. 18).
• The 2-panel Red wire from the low-frequency transformer was removed from the terminal strip and soldered directly to the low-frequency cable, with the redundant 3-panel Orange and 4-panel Yellow wires disconnected from the terminal strip and tied back. All terminal strip connections can be returned to original if desired.

Figure 18. Terminal strip connections for low-frequency wiring and new 1-ohm resistor.

Minimization of 50 Hz induced hum noise

• As luck would have it, minimizing the annoying 50 Hz noise was an inexpensive and straightforward remedy.
• A sheet of thick 3~5 mm synthetic rubber sheeting (Fig. 19) simply laid on the top surface of the interface significantly reduced the hum vibrations. To supplement this another sheet can be laid on top, and as colour of the sheeting material is black, same colour as the chassis, it's hardly noticeable.

Figure 19. Thick synthetic rubber sheet to lay on top of the interface chassis.
* For attaching to the underside and internal sides of the chassis, I used INOAC's 0.5 mm self-sticking dampening sheet "CALMFLEX" (Fig. 20). https://www.inoac.co.jp/en/solution/calmflex.html

Figure 20. Self-sticking dampening sheet attached to the underside of top chassis plate.
* For such a straightforward and relatively inexpensive fix, transitioning from an initial annoying hum noise to being almost inaudible was remarkable.

Wood Frame Repair
* Both speakers suffered from a slight sideways tilt with uneven leveling, caused by splits in the particle board wooden frame (Fig. 21). Although not directly related to this interface restoration, with the interface detached from the speaker's frame it's an opportunity to carefully inspect each wooden frame's condition.

Figure 21. Underside of wooden frame base showing split in the particle board.
* Using wood glue and C-clamps the repair is not difficult (Fig. 22), for my first attempt I used a general-purpose wood glue but after a few months a split reappeared. For my second attempt at repair, I used a stronger brand of glue "Gorilla", and as of this writing the repair has remained intact. Both speakers now align level when viewed from the front.

Figure 22. Clamping of wooden frame base - a spacer board helps even the c-clamp force.

Support Legs

• There are 4 support legs for each speaker, thread type 1/4 inch diameter with pitch 20 threads per inch, with 2 support legs on the front that screw into the base of the speaker frame (Fig. 21), and 2 on the back that screw into the chassis of the Magne-Kinetic Interface.
• Perhaps from uneven levelling caused by the broken wooden frames, the support legs had become twisted and stuck within the base feet (Fig. 23).

Fig. 23. Original threaded support leg (4 pieces per speaker)

• While there are many aftermarket brands to choose from, I replaced the original support legs with IsoAcoustics GAIA IIs, the GAIA II series being suitable for speaker weights up to 120 lbs. (54 kg). You can see a partial view of these in Figure 1.
• Whichever brand and model you choose, ensure they support the weight of your speakers and are supplied with the common thread size of 1/4 inch - 20.

Speaker Cable Connections

• I have had different speaker cables fitted with banana pins that did not mate securely with the MK-121-2 interface banana sockets, and in worst cases the speaker cables worked loose.
• While other contributors have kindly shared their experiences of machining the interface chassis to install heavy duty banana sockets, one of my goals was to preserve the Acoustat original external appearance.
• In keeping with the original sockets, what worked for me was the Furutech FP-202 series banana connector (Figs. 24, 25). With the thumb screw fully tightened to expand the locking spades, I was unable to pull it out from the interface socket.

Figure 24. Assembly of Furutech FP-202(R) connectors with Furutech u-2T speaker cable.

Figure 25. Completed FP-202(R) connectors with u-2T speaker cable.

Measurements after Restoration completed

• For the following tests the input AC Voltage was maintained at 115 VAC, 50 Hz.
• AC voltage measured at output of the step-up transformer exhibited a clean sine wave ~720 VAC RMS (Fig. 26).

Figure 26. Measured output of AC step-up transformer.

Voltage loading on the WIMA high-voltage audio capacitors

• As mentioned, to double the voltage rating and achieve a wider safety margin, the WIMA high-voltage audio capacitors rated 6 kV DC and 700 VAC RMS were configured as a set of 4 (total 8 for one board) in a series/parallel configuration (Fig. 9), providing 0.01 uF with effective voltage rating of 12 kV DC and 1400 VAC RMS.
• With my version of Acoustat speaker, measuring the actual RMS voltage across this capacitor configuration while playing loud music revealed there was enough safety margin.

Figure 27. Test leads connected across WIMA capacitor configuration (test repeated for configuration on opposite side).

Figure 28. PC setup for logging AC voltages from True RMS Multimeter.
* Playing loud music through one channel into a single speaker produced sound pressure levels ~85 dB C-weighted as measured on my mobile phone app (Fig. 29), while the maximum True RMS voltage measurements peaked between 250 and 300 VAC (Fig. 30). Depending on your model and version of Acoustat your results could be different from mine.

Figure 29. Measurement of sound pressure level during loud music volumes, one channel feeding single speaker.

Figure 30. Logging of AC RMS voltages measured across a 0.01 uF capacitor configuration.

• Even allowing for some averaging, the maximum RMS voltage levels measured during this operational test fall safely within a single WIMA high-voltage capacitor's rating of maximum 700 VAC RMS.
• Side comment regarding the sound pressure levels of ~85 dB C-weighted when measured in front of a single speaker driven by one channel, had I conducted this test with two speakers in stereo mode it would have made for very high sound levels, enough to me get thrown out of the house!

How did this MK-121-2 Interface Restoration Impact the Sound Quality?
* In the absence of professional audio measurement equipment, to discuss three modifications that gave a clear noticeable improvement in sound quality and listening pleasure. To put this in perspective, the original Acoustat speaker already produced exceptionally clear sound, with these changes it became even better.
1. Rebuild of High-Voltage Board

• Changing all components on this board for newer or higher rated components produced a clearer sound across the full audio frequency range. Difficult to say what made the biggest impact, one theory could be the original high-voltage audio capacitors that had leaked oil being replaced with new high-voltage polypropylene capacitors.
• Also on this board is the high-voltage polypropylene capacitor added to the output stage of the high-voltage ladder, which gave a substantial improvement in bass frequencies delivering more punch.

2. C-Mod Implementation
* I concur with others who have previously commented on improved clarity in the upper frequency range this modification brings.
3. Vibration Absorbing Sheets
* Applying these vibration absorbing sheets produced a welcome reduction in 50 Hz hum noise, important when listening to quiet music passages.

Parts Replaced

Figure 31. Original components replaced.

• Top bin: HV audio capacitors, HV diodes, HV ceramic disc capacitors, HV audio capacitors.
• Lower bin: 10 uF and 0.01 uF capacitors, 220 uF bipolar capacitors, 500 M-ohm resistors, cable clamps and 1 ohm power resistors.
• Not shown: 5-A slo-blo fuses, speaker support legs, low-frequency cabling.

Final notes

• Although there's a lot of detail in this writeup, when detached from the speaker frame the MK-121-2 Interface components were straightforward to access and not difficult to work on. There is also sufficient space inside the chassis for installing the C-Mod components.
• The reason for this writing is to share my experience restoring the MK-121-2 interfaces in my beloved Acoustat electrostatic speakers. It's not an endorsement of any component supplier, just to share what worked for me.
• If I was to do another MK-121-2 interface restoration, what might I do differently? As this was my first experience working on an electrostatic speaker I proceeded slowly with extreme caution, but knowing what I know now with the measurements made, I believe it would be safe to stay with single WIMA 0.01 uF high-voltage audio capacitors rated 6 kV DC and 700 VAC on the HV board (rather than the set of four I configured in a series/parallel configuration). However, as the circuitry is performing flawlessly and has a wide safety margin, I'm happy to leave my configuration as is.
• At time of this writing pleased to report both MK-121-2 interfaces have been operating without issue, now enjoying listening to my restored Acoustat 2s with their superb sound quality.

Appendix
Referencing the setup displayed in Figure 1 "Acoustat Model 2 home setup", to share restoration projects of other vintage/classic audio equipment.

• Left side, below top shelf, "ReVox B739 FM Tuner Preamplifier restoration" https://www.audiocircle.com/index.php?topic=184978.0
• Left side, middle shelf driving the Acoustat Model 2 speakers, "Bryston 3Be Power Amplifier repair - Hints and Lessons Learned". https://www.audiocircle.com/index.php?topic=184960.0
• Right side, top shelf, "Oracle Premiere Turntable: A Successful Restoration". https://www.audiocircle.com/index.php?topic=186862.0
• Right side, below top shelf, "Spectral Model DMC-10 Preamplifier - A Successful Repair". https://www.audiocircle.com/index.php?topic=186474.0
• Right side, middle shelf, "Krell CD-1 Player: Successful repair of Remote Control unit". https://www.diyaudio.com/community/...cessful-repair-of-remote-control-unit.402329/
• Right side, lower shelf driving an Acoustat Model SPW-1 Woofer (not shown), "Bryston 2B Power Amplifier repair - Hints and Lessons Learned". https://www.audiocircle.com/index.php?topic=184949.0

Hi,

I just got myself a vintage Neutrik RT-1M multitone audio analyzer. Next thing I need is the manual and the PC software to run it...

Anybody can help me?

Jan Didden

7 new
5 gently used

really would like to see you mail a money order to me...................

Just wanted to say I've had a great experience using this crossover module from Zinamp http://www.zinamp.co.uk/

Really easy to integrate and power etc. Dead quiet. It's easy to adjust the crossover points on the fly which is really what I was looking for. You can even change the shape of the slope depending on how your driver measures. It has baffle step compensation that you can use or not. Bass boost!

I'm still using the op amps that it came with but there are higher performance ones available

And if all of that wasn't great enough the technical service from the owner or whoever does his tech support has been flawless and so quick.

I guess this might be a review at this point. I just haven't seen many people talk about it on here and I feel like it is a really simple solution. It sounds really great to me

Same goes for neurochromes preamp power supply, super great to have such simple modules out there for those of us who have a tendency to blow things up

Hello!
I have recently re-discovered my Realistic PortiPlay 13-1163 ladybug phonograph, after being put away for months, if not years. It was working OK, but then it all went downhill from the point when I dropped the stylus on the textured platter mat to see what would happen. I am revisiting the project, but I cannot find an affordable stylus that would fit in this machine. Looking for somewhere that I could find one, please.
Thanks!

Hi fellow audio geeks.

I bought a couple B3N Drivers on sale awhile back. Now I'm trying to decide if I just build a couple boxes for them, ala Zaph. OR, do I buy a couple more, and make a sound bar with 2 + 2?
There's a 6" alum Airborne subwoofer on sale too, so I can use that. it's smooth past 1khz, so it would tie nicely close to the B3N's with a 200hz cutoff.

I haven't designed or built a crossover in EONS, so I'm looking at Zaph's parts list:
http://zaphaudio.com/audio-speaker18.html

QUESTIONS:
1. What kind of wattage is needed for these components... especially resistors? I see R5 is parallel with 2 others... so 3-5W ? but 30ohm... would 250mW be enough? I imagine most of the current there would flow through LF & C3, correct?

2. I'm in Canada, and the Inductor cost on Solen.ca is $9 each! makes the total parts for each speaker as much as the driver itself. I'm looking here: https://store.walectric.com/electrical/ but they have too many options... Any recommendations as to crossover parts? I'd be willing to order from US too.

I'm tempted to buy a couple more drivers, and put 2 in each side of a soundbar, with the sub in the middle (facing up or down, obviously a deep sound bar). If I paralleled them, this would change the impedance to 4ohms. Obviously, I could go to 16ohm in series too.
3. If I did this - what values would change for the crossover? Would a 4 or 16ohm load make for more affordable crossover parts?

thanks in advance!

I'm selling 15 pcs of these rare jfets,
New and unused (NOS).

I've measured their Idss (@9V/25°)
and the results are as follows:

10.14
10.56
10.89
10.91
11.30
11.86
13.80
14.08
14.13
14.21
14.40
14.60
14.62
14.96
15.25

As you can see, there are at least 3 pairs of them with very close Idss.

Guarantee they're authentic, if not, just send them back to me (I'll cover the returning cost) and get your money back.(you can write it on PayPal when you buy them).

Asking for SOLD

PM me if interested

Thanks!

Hello DIYaudio,

Im giving designing my first subwoofer a go, for a La Voce SAN215.30. Its based on the cyclops design and then a design of a friend who came up with the plan originally, the idea is to not worry so much about size and get as much output in the 20 - 60/80 bandwidth, whilst still sounding nice. Any ideas welcome, TH, TL etc etc

I understand I need half SD for one of the horns/paths but cant seem to find any reading material on what other parameters need halving or leaving alone. I have looked! perhaps even scrolled past it. New to hornresp but am slowly working it out, I knew this day would come and am happy I have such a plethora of drivers lying around to design boxes for.

Thanks in advance.

While playing music outdoors for a friend's kid's grad party, a rogue storm rolled in fast and blew the tent covering my system off while it was playing before I could get to it to turn it off. Strangely the amp still functions, but both speakers are completely dead. They appear dry inside, I checked both fuses, and they seem fine, and still no sound from any part of the system. It breaks my heart to think they are done for this world, so looking for ideas on what I can check or try before giving up on them. Thanks!

Hi I wonder can someone help please. I have 2 ev Zx4 passive speakers. Am replacing the drivers. Because they have blow. Can I put different drivers in. With same wattage and oms. Or can I put more powerful woofers I them. Any help would be much appreciated

Dear friends,

In the future I like to re-built my wonderfull Vifa Basis 95 speakers.
They sound very nice and powerfull but I don't like the design of the original cabinet.
The drivers are in very very good condition.

My plan is to design separate cabinets.
One cabinet for the bass and one for the mids and highs.
I did not change the volumes of the new cabinets as you can see.
I also did not change the baffle width of the top cabinet for the mids and highs.
What I like to check is the port dimensions of the bass cabinet.
So I'm looking for a correct data sheet of the woofers.
See also my other thread.

Specifications:

Drivers : 5x
Power handling : 360 W
Sensivity : 91 dB
Frequency respons : 25 Hz tot 25 kHz
Nom. impedance : 4 Ohm

Bass: 2x M25WP-00
Low mid: P17WJ-00
Dome: DM-760/2 / D75MX-31
Tweeter: D2905/950000

Can someone give me some advice / comments?

Hi

I have a Crestron CNAMPX16x60 for sale, local pickup only (San Francisco, or Sacramento/anywhere in between). This is the amp with amplifier modules by ATI so audiophile quality.

I also have the Crestron power supply with Phoenix connector to override the Crestron control board (needed for non Crestron systems, if one is handy can rewire the amp to bypass the Crestron control board)

Specs are 60W/channel into 8 ohms x 16 channels

90W/channel into 4 ohms x 16 channels

Channels can also be bridged (either internally or with XLR to RCA cables)

Bridged power is 220W/channel into 8 ohms (Can have upto 8 bridged channels)

$325 OBO.

Weight +100lbs so no shipping.

Thanks

Shri

Hi

I have a Rotel RSX 1065 (note this is a better product than the 1055). comes with a Harmony remote that has been programmed for the 1065. Can be used as a multi-channel amp also.

Weight is 45 lbs, so no shipping. Pickup in San Francisco, or Sacramento (somewhere in between also possible)

$300/OBO.

Product Description from Rotel Website

Rotel ’s RSX-1065 Multi-Channel Receiver is the high performance alternative to complex multi-component home theater systems. In honor of Rotel’s audiophile origins, the amplifier provides enough high current output to drive even the most difficult speakers.

In multi-channel mode the RSX-1065 delivers 5 x 100 watts per channel RMS, all channels driven, and up to 200 watts per channel under dynamic conditions. A generous Rotel-made toroidal transformer forms the heart of a prodigious power supply to ensure unblemished reproduction of the most dynamic crescendos and most delicate sonic nuances.

The RSX-1065 easily handles the most demanding system configurations. Custom ID capability allows users to program the source selector so that it displays exactly which component has been selected. Digital inputs are assignable. Multi-zone, multi-source capability? Of course. The RSX-1065 also handles two component video sources and provides a component video monitor output.

Advanced Crystal Semiconductor microprocessors handle Dolby Digital, dts, and Dolby Pro Logic II decoding as well as several music modes for optimum enjoyment. In addition to conventional 5.1 capabilities, the RSX-1065 boasts two additional preamplifier outputs to feed, through appropriate amplification, an additional pair of speakers.

This gives home theater enthusiasts the spatial benefits of the latest enhanced surround modes. For custom-installed systems, the RSX-1065 includes an RS232 interface, 12 volt “trigger ”outputs, and discrete on/off remote control command codes. A fully programmable remote control is standard.

Thanks

Shri

Hier,

I try to find a compatible display for my Wadia 9 DAC, but no way..

Do you know where I can find one ?

Thank you

Id like to hear how you measure yours?

I'm a back seat driver and still learning 😊

Dear members, Does anyone know of a good source for CD replacement belts? I have a Simaudio CD3.3 player that needs some love.

I've rescued a garage find Quad 303 and recapped and rebuilt the PSU and amp boards to the Dada list, switched on with nothing connected it works fine, 67V present 33.5V present and able to set the bias which is at ~6mV on both channels.

Now this is where things go wrong, connecting a signal to it (someone's put phono sockets on the front panel, these are uninsulated) and watching the trace on the scope, it'll get to about 1.5 - 2 volts out then the heat sink will get very warm, set to about 4V out it starts to clip then R115 the 2.2ohm resistors on both amp boards start to overheat and smoke.

Any ideas welcome.

Thanks

Chris

Hi, I just bought a preamp with a "Main Out" but need two outputs. I do not have a tape player and am wondering if it would be detrimental to run a wire from the board from the main trace to the "Tape Out"?

I have two units (2x4) and want to tidy things up by putting both in a case with a single power supply. They run from 5v to 24v and draw 150mA (at 5v).
The obvious solution seems to be to run both from a SMPS (in parallel). I have a 12v Meanwell that would comfortably handle the current draw, but... I haven't seen any examples of people doing this. Is there a reason for that?
If it's not a good idea then I could just get another one, or maybe go linear. I have a torroid with 2x15v secondaries that could feed one of those two output Studer based boards on AliExpress. The Salas l-adapter looks great but presumably I'd need two and I don't want to overdo things. Any advice gratefully received. Thanks.

Hey guys, been awhile since i've been here!

Ran into a strange issue last night while re-connecting my Holfi battriaa phonostage to my toshiba sa7100.

I lost the left channel from the phono input side so i took the cover off and found the whole chassis to be microphonic. If i tap on the metal chassis it creates thumps from the speakers.

Some kind of grounding issue maybe? The holfi is grounded via mains earth using a spade connection. The toshiba SA7100 has recently had its reservoir caps replaced with Mundorf AG+ (4 pole), so i'm not sure if this has anything to do with it? From what i could gather the transformer centre tap is no longer used with the 4 pole caps.

The turntable (rega RP3) grounds through the phono plugs as far as i know and dosent have a separate ground connection.

If you are reading this and are unfamiliar with my escapade so far, I'm building a 3 way set of speakers the size of a set of bookshelf speakers. For the Mid and Tweeter, I am using a KEF SB1632. For the Sub I'm using a dayton E150HE-44 5-1/2" speaker.

In a prior thread, we went back and forth concluding MFB would be a pretty cool addition to my design. But then it hit me...

I'm trying to put a subwoofer in a relatively small enclosure. Already I'm looking at some interesting design challenges... some of which I guarantee I haven't even thought of yet.

So yeah, what would be some design considerations I should take into account while making this thing?

I have a question in when I was checking these voltages (see attachment) as you can see, they don't match up. What would be my next step in troubleshooting this problem??
Pat

The amp came to me with one channel blown. The signal board was a mess. I replaced it with a Hoppe's Brain board. Installed and tested. Amp is playing both channels. I am unable to get any bias adjustment from the original blow channel. Any thoughts or direction on where I should be looking?
Thanks

I acquired a pair of Cain & Cain Abbys, and the previous owner refurbished them. Part of that refurbishment included the replacement of Fostex FE166E's with Audio Nirvana Super 6.5" Alnico drivers.

I've never heard Abbys before, but have read much about them. Without working much yet on placement, I haven't been able to get the speakers to "disappear". I'm very aware of what's coming from right and left. This disagrees with what I've read.

I'd like to hear what the original drivers sound like; but Fostex has discontinued them.

Has anyone had experience with the combination I'm using? Can anyone recommend a replacement, in Abbys, for the FE166E?

Thanks in advance.

Boxsim uses a grid of dots to create wires. Easy to use but only connects adjacent dots.
A number of the sample designs show wires that miss adjacent ones, curved or zigzags that pass over other wires.

Tried all sorts of key presses but no luck. Anyone know how to create these? Tried V1.2 and V2. No joy

Hi everyone. Got a question I recently purchased two macrotech 5002vz they work great and everything but one of them seems to play more loud that the other, it even clips earlier than the other. Any clue what may be the problem here.

I noticed that one seem to be made earlier than the other not sure though, I also noticed the one that plays louder uses crown oem output transistor, and the other uses crown and onsemi transistor. So if anyone have any idea please let me know.. TIA

MM Input Stage: RIAA Equalization with Shunt Feedback - not often to find; why ??

For such input stages the 47k load works in serial mode to the cartridge inductors.
Main disadvantage is probably the not sufficient signal to noise ratio cause the large resistors.

But I have heard, that the peaks by scratches on records much less aubible.

Are there experiences concerning this topology ?
Some links in this matter
http://audioqualia.prophpbb.com/topic60.html
http://www.diyaudio.com/forums/solid-state/29772-overload-considerations-riaa-preamps.html
http://www.vinylengine.com/library/john-linsley-hood/1450.shtml
http://www.diyaudio.com/forums/analogue-source/249557-riaa-amp-using-shunt-feedback.html (post #40)

I'm trying to fix this amplifier. Can't find a schematic but I have attached images, it's a pretty simple circuit.

Most transistors were burned and shorted, and there was a shorted zener diode.
I replaced all BC327 transistors with BC328s
I replaced all BC547 transistors with BC546s

I also replaced 3 electrolytics and the shorted zener diode (with a random one i had, no idea what this should be, but it measures similarly to the other non-shorted one in diode mode.)

I replaced a burned up resistor with a 4.7k - it was impossible to tell what the old one was but it had one line still intact which was the same as, and was the same size and shape as a nearby 4.7k resistor.

You'll notice a burned film cap next to the other components which i didn't replace as it still measures ok.

On power-up, the MD8003 dual transistor got really hot and started smoking, so i quickly switched it off. This transistor measures fine with my peak component tested (no leakage), however i replaced it with dual 2n2240 transistors to be safe. Sadly - they also heat up rapidly in a few seconds after switching it on.

The amp uses an MJ3001 an an MJ2501, which are both missing - I have them on order but obviously there's a major problem here i need to fix first. I have checked really, really thoroughly for shorts and I cannot find any - I don't know what could still be wrong here. I have tried lifting the resistor I fitted in case it was that, but still the same issue.

Would really appreciate any thoughts.

SOLD
I built this as external IV stage for my Miro AD1862 dac.
Of course they can be adapted to be used with other current output DACs. eg. TDA1541, PCM63, AD1865 etc
Two stacked AD844 op amps per channel, goes into OPA627 op amp as buffer at the output.
Discussion, schematics and gerber can be found here:
https://www.diyaudio.com/community/threads/using-the-ad844-as-an-i-v.227677/page-98#post-4954595
https://www.diyaudio.com/community/threads/using-the-ad844-as-an-i-v.227677/page-121#post-7245864

USD65 shipped to you. Hardly cover my costs in parts.
Paypal Friends & Family only please.

NOS pair of discontinued 4 ohm, 15" woofers. Claude's recommended replacement/upgrade for transforming Klipsch Cornwall into Super Cornwall.
$350 plus shipping.

NOW ASKING $45. Class A Headphone amp in a mint tin by XRK971 back when he was selling fully assembled amps vs. just boards. Tuned to support 50 Ohm cans, build #37. There is a review out on the interwebs that features #36. The tin looks horrible, I was trying to improve cooling ventilation, that said the amp is fully functional. I can send extra pictures if requested and I have copies of the purchase/build conversation with XRK971.

Hi!

I'll get a blown HK amplifier soon to repair and I'm on the preparation phase so I checked the schematic, and the protection part in focus.
Here is the schematic which is 90%-ly clear, but I can't understand the Q4 section... 🙄
Could you help me what the purpose could be?
I also simulated it in LT but still not clear.

So far the sections I understand:

1. on the left Q401 + 2 FETs: they mute the input stages
2. the top-right: is the PS for the protection (D3, D4, C10 etc)
3. R5 + C11: forms the "power on delay"
4. Q2 + Q3: protection latch config with some "+" FB (via R8)
5. Q8 + Q7 + Q1: the overcurrent detection
   (Q8 base gots a positive voltage when there is ovvercurrent situation which shunts C11 finally)

But what this Q4 + D5 + R16 are doing..?

Thanks in advance!

PS: In the simulation I increased C10 to 100uF as with 4u7 I got "heavy" ripple ot the "-4.8V" line.

Does anybody has an application or know a bluetooth remote switch ?

One or two pushbutton switches , battery powered, BT transmitter -> BT Receiver with GPIO output

The BT Remote should have very low power consumption ( like an Apple TV Remote control )
It should pair constantly as soon the receiver is powered on.
The BT receiver should have either GPIO or Relais.

I rebuilt channels C and D of this amp only to find the driver card for channel C has a trace problem. I replaced 3x MPSA42 and 2x MPSA92 on the driver card to no avail. All SMD components are measuring correctly while in circuit. I re-soldered all the components a few times but still cant get the driver card to operate correctly. I moved this driver card to another channel and its definitely the card thats the issue. There are not too many components on the card but I cant figure it out. Any channel will go to -26vDC with this driver card.

Any clues or a schematic? Has anyone seen one of these amps? Im almost wanting to just replace the driver card at this point but dont know where to source parts.

It looks easy, but its been kicking my behind even after checking whatever I could compare for about an hour with a working card.

Thanks

I’m building a TDA7293-based power amp according to Fig. 1 on the datasheet.

* What is the recommended V+s/V-s for roughly 100W output at 8 ohms and 0.1% THD? The datasheet says anything up to +/-60V, but I tried 45 and it blew up and caught fire (at the voltage supply inputs).

* How much supply current will it draw at full volume? The datasheet only says 100mA quiescent.

I really can’t figure this out, I need your help.

Good day. I am working with a Deaf Bonce AAP 800,2D which has a flashing protect and clipping mode. I just found out that 2 output FETS are shorted, Removing it, then
the blue light is on and out from protect mode, As you all know the power supply and output FETS on some of the design of Deaf Bonce have their FETS re faced which is
difficult to know the correct part and written only H1 (power supply FEts) and H8(output FETS). I tried fixing with 200v ,104A (IRFB4115) Fets for the output, from Stetsom 3000EX but no luck because they are getting hot without load although gate signals are correct. Can anybody know the correct part number of these Fets? Thank You.

If you would, please, tell me how to remove the pop-up 45rpm spindle on a Rek-O-Kut Rontine turntable? I want to play with mats and it kind of sticks up and gets in the way.

Responses that tell me that I shouldn't do what I want to do will discreetly be ignored. Thank you kindly.

I admit that I'm proud to be a scrap merchant. I got a home-theatre active subwoofer. I only wanted the driver. But the sub box contains all the gubbins. As usual there is a multi-pin cable connecting the (failed) head unit to the system.
I really don't want to throw away a 5.1 plate amp that claims: 120w + 80w x 5. ( I know it doesn't) but that's respectable grunt for a home theatre system. Can I rewire the board input to accept simple stereo phonos and an on/off switch?

Schematics are here: Service Manual

Good morning everyone, Jeff from Canada here.
I have a new toy and I was disappointed when I found it dead, I removed the monsters cover (barn) and found its 8Amp fuse had been replaced with a 14Amp fuse and this was blown. I nearly spit my 🍺. The fuse it to protect the wire and fear this could get expensive. I am looking for a schematic online and will be looking for.a short.
I will keep you posted and no doubt be asking stupid questions.

I have a working unit im looking at and it has a couple of items i am going to look at but havent come across yet and thought i would see if you guys had any ideas before i started.
sound is generaly ok, and not distorted at all, but the levels are lower than what i would expect.
tone controls appear to be ok.
loudness doesnt seem to have any effect.

when volume is turned right down you can still hear the slightest of sound.
when you turn balance left to right and visa versa you still have sound coming out of the opposite one, not fully, but noticible.



There isnt any problem with the phono/aux/tuner switch so thats ok


im thinking it might be something to do with the fact it has mic/source mixing

when you turn that down to source only with the tape/source switch in 'source' it seems ok, but if you turn it to tape and leave the switch as it was, you can still hear it,but at a reduced volume(unless its supposed to be like this)


im just starting to go through the schematic, but the quality isnt brilliant
the amp is pretty dirty inside and i will clean all the switches and pots as this may be having some effect.



could this just be poor/failing caps??

Hi all,

I own a Mercedes-Benz W109 S-Class for quite a while now.

This is one of the later models of the series (1972), but the design was basically before 1965 (and even from the 50’s as it is heavily based on the predecessor). Back in those days, hi-quality audio in the car was not really a thing. Remember, at that time there was an ongoing debate if listening to the radio was dangerous as it could divert the driver’s attention…

I was never a big fan of audiophile audio setups in cars (as opposed to home/pro audio setups). All I am looking for is a decent, basic setup with 2 speakers on the front and 2 in the back so I can listen to some music and audiobooks while driving.

From the factory, mine was equiped with a single mono speaker on the center of the dashboard and another mono speaker at the center of the rear shelf (the latter was already an option). Luckily, it was already prepared for stereo speakers in the rear, the body pannel of the rear shelf was already pre-punched at the factory. So for the rear, no problem, I managed to install a pair of standard 2-way car speakers without any problem.

The real issue is the front/dashboard. There was another factory option for stereo speaker in the front, but I really don’t like how they did it. These are small speakers mounted in the footroom, not even pointing in the same direction (on the driver’s side, it is pointing towards the transmission tunnel and your legs, and on the passenger side it is pointing towards the seat. These speakers can still be ordered but cost a mint and I really don’t like this setup.

There is one aftermarket solution which consists of installing a special stereo-speaker (1 cone, 2 tweeters) in the original place in the center of the dashboard, but I like this even less.

Of course, drilling 60mm holes in the wodden dahboard is out of the question, but I wouldn’t mind fixing speakers on top ot the dashboard for instance, provided that it looks decent and that it could be removed if needed.

If, by any chance, where are other w108/w109 drivers here, or anyone who has some ideas, please share!

Here are a few a pictures of similar cars (not mine, but the dashboard is the same), just for reference…









Cheers!



Denis

I've heard a couple of requests for shorting rings. I'd like to briefly give a couple of my thoughts, and hear a few of yours. First of all, I am not well versed in loudspeaker design. Most of WBAL is a combination of good networking and dumb luck. I'm learning all I can, and that is part of the fun.

I had the opportunity to compare back to back, a couple of Burro ancestors that had only two difference. One was mostly cosmetic, and the other was a shorting ring/copper pole sleeve. It's a tiny part that fits nicely on my pinky, but it makes an absolutely huge difference in the way the driver behaves. Basically, it eliminates a bunch of distortion, and causes the impedance curve to remain quite flat into the high frequencies. That sounds good, right?

Here is the rub: that rise in impedance, in combination with most amplifiers, helps keep the frequency response flat. Loudspeakers naturally have a rising frequency response above a frequency related to their diameter. Physics can be a bugger. When the impedance limits the power the amplifier puts out roughly in proportion to that rise, you get, for an 8" driver, maybe a 5 db rise on axis. Then, when you listen a little off axis and keep in mind that your room absorbs HF, you can get a pretty flat response out of a single driver.

But, when the impedance stays low, you get maybe a 10db rise on axis. Don't believe me? Check out the FE206E and FE207E response charts. See the difference? Think that is do to the 206's slightly lower Q? Take a look at the Betsy and BetsyK. They have a Q difference much greater than the 206 and 207, yet their rise is nearly identical. As a matter of fact, if you lay the BetsyK's response over the 207's (when measured on the same setup) they are very, very close. When you lay say, the BetsyK's ancestors (with the shorting ring) curve over that of the 206, you get, again, a response that is very, very close.

I can't tolerate the on axis rise of the driver with a shorting ring. In my system, they sound incredibly bright. Searingly bright. Shouty. It ain't a peak, it's a general trend. One of my customers owns another makers 8" driver with a shorting ring, and talks about a notch filter to cure it's ills. But, it isn't a break up mode, it's just 5-6db too much HF.

Folks tend to deal with it by using cabinets that have considerable bass gain, and gain up into the midrange. Some find that sound to be very detailed, and preferable. I also suspect that some shorting ring fans are a little older and have some hearing loss. Don't yell at me, there is nothing wrong with that. I'm 30 and I can only hear to 16K (I grew up on a farm, with shotguns, and went to play in incredibly loud orchestras and big bands). But, don't assume that the top end you like is the top end everybody likes.

If you like that sound, I won't stop you from using such a driver. I encourage everyone to use equipment they like, and I don't judge. I think different folks ears and brains prioritize different things. But for folks that like a reasonably flat in room response, with most cabinets, most rooms, and most amplifiers, if you have an 8" fullranger with a shorting ring, you need a compensation circuit.

That might be a good way to go. Theoretically, you could get lower distortion, and maybe better sound. Most of the customers I've heard from don't want to use any capacitors, inductors and resistors. I don't want customers unhappy with their speakers. But, for those that understand the effects of a shorting ring, not just those who assume it is better, I would consider offering a speaker.

So, who wants one? I would need a few customers to justify having them built. It wouldn't add more than a few bucks to the cost.

Speak up! Let's keep this thread focused on related motor issues though. If you're looking for something else, start a new thread.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

I have started a new project. It is a new line array derived from Don Keele’s seminal Constant Beamwidth Transducer (CBT) activities. At this point the cabinet has been designed and built but surface finishing (painting) and detailed assembly need to be completed. Likely, it will take 4-6 weeks of work to complete this effort and hear music.

This project evolved from a fortunate snap decision I made late in summer of 2016. Madisound ran a sale on SBA 65 (SB Acoustic SB65WBAC25-4) drivers which reduced their cost by nearly 50% so I purchased more than 50 of these jewels. The SBA65 drivers have a molded plastic frame with a neo magnet. Usually, I over think my DIY speaker design before buying drivers but in this case I did have a specific idea in mind. My goal was to eventually build a full range line array with these drivers. During the past year I considered various configurations—straight arrays in either monopolar or a dipolar arrangement but had not settled on the best way forward.

While I have read Don Keele’s CBT work over the years, I really did not seriously consider a CBT design. But at the 2017 MWAF in Dayton I had a chance to talk with Keele about some of his latest work and to see/hear his CBT24 that he developed for Parts Express. Don sent me pre-release copies of his October 2017 AES Convention presentations. One paper, coauthored with Canadian researchers, was on a dipole CBT design. After reading that paper I was convinced that a dipole CBT was not what I really wanted to pursue. Don also shared several details about the CBT24 (called the Epique by P-E).

Keele’s sales points for the advantages of the CBT24 vs. conventional systems including: Even coverage with no sweet spots, elimination of floor reflections, reduction of ceiling and floor reflections, broadband constant directivity, flat power radiation, ability to play extremely loud with low distortion, and the system is time aligned and phase linear. He says that it can reproduce square waves at all locations in front of the speaker when properly equalized.

After studying the CBT24/Epique design I decided to proceed toward using my SBA65 drivers in an improved version of the CBT24. Thus my new line array project is a modified version of Don Keele's CBT24/Epique arrays.

What didn’t change in my version versus the Epique was the number of drivers and the arc. The new array is still 24 drivers and 36 degrees arc. Beyond those basics my new DIY array deviates from Keele’s work. I'm using a different (and better) 2.5" driver than the units used in the Epique units. The SBA65 is a 4 ohms driver vs. the Epique's 16 ohms. Several users on DIYAudio and other forums have commented upon or directly compared the SBA65 to other 2.5” to 3” diameter drivers. Most notable in comparison the SBA65 has a relatively flat frequency response with a rise in the 10k-20kHz range.

The drivers used in the Epique have 16 ohms nominal impedance while the SBA65’s 4 ohms impedance which necessitates that the shading network used in the Epique need changes for my modified CBT24.

For my arrays the cabinet--while looking similar to the Epique's--has several key changes. The new baffle is customized for the SBA65 drivers as there are significant mounting changes vs. other 2.5” drivers. A single unequalized SBA65 in a sealed box will get down to an F3 of 140 Hz for a half to one liter volume. For the modified CBT24 I changed the width of the tower to 4.5" vs. 3.5" for the Epique. Internal bracing is added which strengthens the enclosure. The SBA65 drivers are spaced 2.625” center-to-center apart.

One focus for me was on improvement of the base/tower interface. My needs were for stronger attachment of the two elements plus addition of easier separation for moving and transport of the arrays. The solution was to add an internal U-shaped metal plate with welded nuts inside the enclosure. Screws attach the base to the bottom of the tower and thread into the captured nuts inside the tower.

Just like the Epique my modified CBT24 is intended to be used with subwoofers and equalization to cover the entire frequency range. As mentioned earlier the lower F3 of the basic array is 130 to 140 Hz without equalization. For realistic bass levels subwoofers would be needed. I expect that equalization will be necessary to tweak the frequency response to perfection.

Kevin Kendrick has started a build thread on the modified CBT design on the Parts Express Tech Talk forum so you can link there for construction details and in process photos.

Kevin's construction thread is at:

Jim's new CBT Arrays - Techtalk Speaker Building, Audio, Video Discussion Forum

I'm trying to build my own guitar amplifier, but I want to add 4 potentiometers to this circuit. Volume, Mid, Bass, and Treble. I am a complete newbie to audio engineering and electronics, so any help as to where I can add these potentiometers, as well as their resistance would be greatly appreciated.

I'm an absolute beginner and want build enclosure for my subwoofer for which i don't know the Ts parameters can any one suggest me how to measure those parameters as near good as possible.
Thank you.