How do you get inside the cabinet of these speakers to service the electronics?

Hi,

I have a H&K Attax 100 on the bench blowing +/-45V rails fuses, the two output transistors with C-E shorted. (MJ4035/MJ4032). Schematic attached.
One of the connectors connecting the transformer to the PCB was broken, there was a bad contact.

Those output transistors seems to be hard to find. I checked a cross reference table, MJ11015/MJ11016 seems to be a potential replacement and easy to find.
I am not overly familiar with solid state amplifiers, could you confirm that those two transistors are a viable replacement ?

Also, I checked the bridge rectifier, filter caps, T5, T6, T7, T8, D31, D32, D33 and D34, no shorts, no broken solder. What should I check next ?

Thanks

Hi,
I got this CD player and it do not play any CD anymore.
Got a new laser installed (SF-HD65). I measured the 2 potmeters from the old laser and putted same values on new laser.When loading CD it reads TOC and gives remaining time, but when pressing playbutton it spins up again but do not play any songs.In this state i can not open tray so i have to turn off power to have the tray out again.
Any helps for solving it would be nice.

Thanks,

Here's the spot for all to put in your pre-orders. Let's keep the other thread for news directly related to the project.

Thanks in advance for any and all help. A friend of mine asked me to take a look at his JL 500/1 - I opened the case and immediately saw that some of the solder joints had at least been resoldered, the flux wasn't removed. Anyway, the power supply and the output transistors were all bad, along with a couple 47 ohm gate resistors. After replacing those the amp produces clean audio and doesn't make the popping sound when powering on or when the remote is used to turn it on/off, only when power is completely removed from B+ terminal - has anyone else seen this? I don't know if whoever looked at it before me moved the two trim pots, I'm hoping they didn't but have no way to know, are they somehow part of this? Thanks again for any advice,
Edit: Watching with a meter and a scope when the battery power is removed I see -21 volts across the speaker terminals for about 500 mS then it drops down to 0. Is this somehow half of the voltage on the speaker terminals being sent out through the speaker?

I would like to add an external antenna for extended range to a Aiyima 100W TPA3116 bluetooth amplifier board. I assume I have to add a ufl connector. How can I do that ?

Hi guys, i would like to get some feedbacks about my Layout, based on the attached schematic.
Thanks in advance

For sale Folsom DIY7297 Amp and Antipole PSU and transformer.
With transformer -160 €
Without transformer - 100 €
Mundorf filter caps and jantzen input caps.
Europe shipping only.

Hello, everyone,

I hope this is the right section to post my request. I did some searching but couldn't find any similar threads (I was used to the old version of the website, in case of error I apologise).
I need to find someone with audio skills who is very familiar with drawing schematics and creating a gerber file for a pcb.

The aim is to make a tuning tool to use for my workshop; the starting schematic on paper is already available. The design is completely analogue. The necessary steps are as follows:
-analysing the schematic together in order to assess possible modifications
-transport the schematic onto software
-select the components and the case together
-realise the pcb gerber following the correct design rules (track dimensions, space between them, etc.)

If anyone is interested, please contact me via PM and I will provide more details regarding the collaboration.
Thank you

This is going to be a long one

Well my friend was about to throw this amp to the garbage when I said "give it to me, I have a technicall degree on electronics, maybe I can fix it"

So I plugged it and turn it ON without the guitar connected to it. And this high volumen whooom noise started coming out of the speaker. I turned the knobs (volumen, gain for the distorted channel, bass and middle) and made no diference to the noise; only when I turned the knob of the high pass filter the noise seemed to change slightly but rather than that its just noise. Then I plug the guitar and tried to do the same experiments and the noise was the same and it seemed like the guitar signal it is not doing anything, because when I played the guitar the noise did not change and there is no guitar sound coming out of the speaker, just the same noise.

I took out the circuit (unplug the speaker and unscrew the cicuit board) and it looked really disgusting, it was like a roach cementery. So I cleaned it with an electronic cleaning spray and the only thing I could see damaged was a 2200µF 35V cap that was swollen. I took it out and did the dgital multimeter test and it seemed to be ok but I replaced it any way. And then put all the things back together and turned it ON and the noise was the same. I took out againg the circuit and started making additional tests, all the resistors are ok and the other caps seems ok.

So the FAQ begins:

1 About the power supply:

It looks ok, It has an AC 120v to 18v and 18v transformer that I could check and is fine. The AC/DC circuit seems ok for what I Could gather it rectifies to 25V DC.

2 About the TDA2040:

This is the main amplifier, so I dont really know if here is where the problem radicates. I mean, if you turn the amp ON and the only thing you can hear is noise regardless of any guitar o knob movement maybe is the amp that is blown. Acording the datashit the maximun voltage (Vs) is 20V but I am meassuring 25V between legs 3 (-VS) and 5 (+Vs). Is this the problem? Is it the power supply? How can I test this amp?

3 About the RC4558p:

This is the pre am. According to the datashit is a dual preamp, does it means that one of the outputs is used for the clean channel and the other output is used for the supersat (disorted) channel? Could it be that is here where the problems is? because if this pre amp is blown it will mess up the input of the main amplifier (TD2040)?

-----

About the images:

- Rage 108 Circuit. Looking around the internet I found this image, it is the circuit for a rage amp but I can really tell if it is the same exact circuit but it looks really similar, my guest is like 85% exactly. Also you can see in the picture that this circuit was dated 10-Aug-92 but the circuit of the amplifier I have is dated 29-Sep-89. In the picture you can see that de voltage for the RC4558p and TD2040 is 27V and 28V and it makes me wonder about the voltage espesification in the datasheet because it spesifies 20V max for both models.

- Actual Amp. This is the picture I took of the amp itself.

-----

I was thinking on replacing the TD2040 but I prefer to wait and see what responses I get about this, and to understand what is happening before making any changes. I would like to know how can I test the amps. I dont know if I will find the replacements in the local electronic parts stores because down here (Venezuela) is not that easy to find some electronic components. Never the less, I will try to find it. Fixing this amp is great oportunity to learn about audio amplifier circuit.

Very interesting loudspeaker topology by Keels and Button. Look at the sims comparing vertical directivity which considers the floor reflections between point source, normal straight line array, and CBT array 😎

http://www.xlrtechs.com/dbkeele.com/PDF/Keele (2005-10 AES Preprint) - CBT Paper 5.pdf

Aside from the cost of buying large number of drivers, this looks very interesting. The large number of drivers must make for a very low distortion loudspeakers.

Hello!

I have a question concerning preamplifier gain. I designed a preamplifier which is now set for 6dB gain (2x voltage), but I started wondering that my laptop can output higher signal than my mobile phone. Also a RIAA amplifier will output less than the cellphone outputs.

So how is gain controlled in commercial amplifiers? Do they use some sort of autogain or limiting technologies or is it just fixed gain?

I once had an idea of rotary switch which would select the audio input and also select a desired gain level by switching a resistor.

My goal is to amplify or even attenuate the signal to 750mV rms line level using my different audio sources.

I would also be interested in what gain figures are you using in preamplifiers.

Thanks for the answers!

Amp came in with a multitude of issues. PS fets shorted. PCB un-grounded to case. Main rectifiers broken. 1N4936 rectifiers shorted. R83/R122 'shield' resistors shorted. C13/C21 caps blown, RCA shields detached, and probably several other issues I've missed noting.

Combed through everything I can, and the LEFT channel still has a problem. Under load, sometimes the amp will draw excessively and cause the voltage across output emitters to be excessive.

I carefully serviced the driver board in the Left channel, and then eventually replaced this board with a known good one to no help. I replaced main 2n6487/2n6491 output transistors because I noticed one not matching and that seemed to help just a bit; but did not fix the issue. I pulled, tested, and replaced the bias transistor MPSAxx. Cleaned the bias pots. Also pulled the output buffers (TO-92) and drivers (TO220) and they've tested ok so I re-installed them. The output pre-drivers on the ceramic boards are measuring OK.

The bias pot in the right channel operates fine, but left channel is very sensitive to any change, and then causes the amp to hit my PS current limit. I've measured up 40mv across emitter resistors. The left channel is also very sensitive it would seem to my oscope which gets better if I set the probe to 10x.

I've got current limiting set to 3A. Cold power-up and the amp idles at 1.25A with bias pots CCW. Transistors clamped, loaded channels. Right channel pulls clean to 3A. Left channel starts out clean but after the amp starts drawing about 2A under load the left output transistors pull to the limit with what seems like bias over-shooting. I immediately pull power to the amp when this happens. I then disconnect RCAs and all load within a few seconds and attempt to power the amp back on; but it still pulls hard to the limit. If I wait with the power off for a few minutes the amp will eventually power on no problem, and then repeat the problem if driven with slight load.

Any advice?

Let me give a simple example.
Used to describe PWM amplifier. Ordinary analog amplifier. And the principle of class a amplifier.
For example, we need to design a regulated power supply (the amplifier is actually a regulated power supply)
For example, we need to stabilize the DC voltage of 30V to obtain 12V DC voltage. No matter how 30V changes, or it will become 31 or 28V in a moment. But the output DC 12V voltage will never change.
Then we have two plans.
1. Use PWM regulated power supply. That is, PSU. Get 12V voltage. This is the same principle as class D.
2: Use LM317 regulated power supply to obtain 12V voltage. This is the principle of traditional analog amplifier.
3: If LM317 plus constant current source is used. Get 12V voltage. But it keeps its current at maximum. This is the principle of class A.

In fact, we can draw a conclusion through this principle.
No matter it is a good place. Or worse. We can all understand it easily.
For example, PWM will save power. But its output signal is worse than LM317. There is no purity of LM317 power quality. When the current fluctuates greatly. PWM may cause the output 12V voltage to drop more.
However, LM317 will have a high voltage difference. So it will generate relatively large amount of heat. Of course, this is related to the output current. The voltage is also related to the input voltage minus the output voltage.

So it's actually easy for us to judge. What are we doing. What kind of products are needed.
But many people don't understand this.
If the output voltage is very low. electric current. Then I think LM317 will be better for this regulated power supply.
If high current output is required for a long time. And it is not particularly sensitive to the voltage fluctuation of the output.
Such as TV. Charger. I think it would be better to use PWM power supply.
PWM= CLASS D。 Lm317= linear amplifier, CLASS AB. LM317+Current constant load= CLASSA

In the past I've soldered 10AWG wire to thick copper binding posts and it took long time to get the wire and connector hot enough for the solder to make a good joint. The wire insulation melted a bit and the copper changed color. Now I'm thinking that tining the wire and the connector before soldering them would only reguire that the solder on the tined components only need to reach the solder melting point to make a good joint. Does that make sense.

I am looking for a pair of 10k mono stepped attenuators for a subwoofer crossover that I am building. In the past I have bought them from Valab on ebay, but I can't find that seller presently. I looked at the DACT offerings, but they are way too expensive for this project. Linear taper preferably, but log is workable. Where can I find them?

Hello,

I'm in portland oregon and I love to ride with my friends on huge mass bicycle rides. We all have speakers on our bikes - interconnected with radios.

I'd like to add some lower end to our crew. Its not easy outdoors, but I'd like to try my best. I need help sourcing a woofer and an efficient amp for a speaker box in the 3.5-4 cubic feet size. (smaller is fine too)

• full range not needed (other speakers are around)
• Loud over deep bass - if tuning up higher helps volume, lets do that. (but still low and warm)
• NOT high fidelity... just the best we can do while prioritizing volume
• DC of course. Can't draw a ton of juice - but I'll get the right batteries.
• Affordable, simple, lightweight are pluses

If I wasn't asking for help, I would drift towards a dual coil 15" PA speaker in a box ported up a little high for volume, run on a two channel 24v dayton amp board. Maybe run wide open just for more music. But I'm open to anything.

Does anyone have time to tell me what to purchase?

Help needed I have just set up my new subs, each one is housed in a custom 700mm wide, 600mm high, 700mm deep box, originally it sounded great then once I applied some filters from REW it messed up it is no longer acting like a sub but a speaker. I have since removed the filters hoping it would bring back the sound of the sub but it has stayed the same like no filters where applied. I have attached pictures and mdat files of the current REW results, and setup. The Dayton Audio are not sounding any different than my previous monolith plus subs. It seems like the speakers are acting as high pass all of a sudden. I have tried changing every part of the setup including using the amp from one of the monolith plus subs to power one of them. I have also tried it without the miniDSP connected to see if that would make a difference, however this did not change anything either. Please help this is driving me crazy all I want to hear is the deep bass shaking down my house 😂

Setup is as follows

• Yamaha RX-V585 AVR also tried Denon X3400H
• to MiniDSP 2x4 HD
• to Cleanbox Pro
• to Behringer NX4-6000
• to Dayton UM18-22

Afternoon
Ok, beginner here with limited experience. I have a pair of Dayton PS180-8 and a pair of RS225-8, looking for advice on how to best employ them. At one point I had the PS180's in a simple vented enclosure based of Dayton audio recommendations and they sounded descent. No low and a little harsh on top end. After reading some post I see a notch filter should help. Any ideas would help.

Real question is is it possible to make a fast system with them? or does it even make since. Looking for quality sound with good low end.
Dayton RS225-8 + the PS180-8?

Hello everyone. I'm new to this forum and to the DIY world. Really appreciate if anyone here can help me. I
found this set in a thrift store today. Can anyone help identify it? I see it says "Pass Labs Clone" on the circuit board in one.
Anyone know anything more? Thank you very much in advance.

Hello,

I am in need of a DIY person to troubleshoot and repair two Chinese DAC's. The first one is an 1865 NOS DAC that I bought from Aliexpress.. The DAC is cutting out in one channel (left) going from music to distortion to pure noise. Sometimes it sounds like both channels distort but they way the sound goes in and out it is hard to tell. Sometimes the DAC will work for an hour with no issues. But turn it on the next day and the problems return. This problem was intermittent at first but seems to be progressively worse.

The second DAC is a TDA 1387 x 8 DAC I bought on ebay but also a product from China. This DAC has a non working left channel. I can faintly hear some popping and very distorted music from the left channel. The right channel works perfectly.. This DAC was non-working straight out of the box. I am waiting to hear back from the seller on this one

I will of course pay shipping both ways and compensate you for your time and for any needed parts. I do not want to try and send these back to China and pay shipping both ways. That would almost be the cost of the DAC's.

If you are interested you can contact me by pm

I had a hard time finding these a while back. I just got a notification that they came back into stock so I ordered 250.

Anyways, if you guys like the Panasonic metal films, get them while you can. They are scheduled for obsolescence and will be discontinued.

Link 3W Panasonics

Maybe to make this thread more valuable, please post another source for these or what substitutes you use for your source resisters.

I have some Pete Millett filament regulators and I'm evaluating how best to orient the boards/heatsinks?
Assume the heatsinks will be the same size and some ventilation holes will be drilled above the heatsinks. I think the boards will benefit from not being baked in the heat but am I worrying about nothing? The blue surface is the bottom of the top plate and is 0.125" thick,

DRV134 DIP8 are currently not available from distributors.
Does anyone know or has experience with DRV134 chips or assembled boards from China?
Are these original DRV134?
If they are fake, what kind of chips are used?

Hi guys.
A friend of mine has a EM-U Proteus 2500 synthesizer, its internal power supply shuts off after a few minutes and then tries to turn on again. When turning back on immediately after the first shut-off, the few minutes become shorter each time. When checking the PSU output voltages after the first shut-off, they are lower than expected (+12v and -12v becomes +11.4 and -11.4v). On the pcb right next to the power input connector, it says +/-15V but the PSU only throws out +/-12V. The unit turns on just fine. I don't know if this means anything...
On the GearSpace forum, some user had a similar issue with this PSU, here is a quote from one particular thread:

"The power supply is easy to remove from the command station., is attached to the bottom with 3 bolts. I removed it and sent it to the technician. He has never seen a Command Station or similar, .....
After checking it, he asked me if the "device" had a soft or standby switch , apart from the ON/OFF at the back panel. He said a resistor or a capacitor in charge to receive or process the signal from the Soft ON/OFF button was faulty.
He replaced it, and the sudden shutdown problem was resolved. And also the loud white noise never came back....

"

Click to expand...

Well, I replaced 2 caps and about 4 resistors in the "Soft ON/OFF" path, and removed as much of the gump as possible and it didn't do the trick. I know that if it was a faulty cap in the output stage. it would not turn on at all.
Any ideas?
Thanks in advance.

Hi. I recently acquired an iFi iPhono (version 1) preamp on eBay for $28. It was known bad, with the seller indicating distortion was coming from both channels.

I confirmed that there is a loud (for line level) sort of rapid clicking distortion coming from both channels.

The distortion takes maybe thirty seconds to start. After being plugged in, the unit's power LED illuminates, then the class A LED, then a few seconds later you hear the output turn on (a soft click and no distortion at this point) at the same time the ready LED illuminates. Then it sites for fifteen seconds more or so and then the distortion starts.

I disassembled the unit and powered it up with the board on my bench and got the same startup results followed by the same distortion. I unplugged the power and with the back of my hand felt around and felt a lot of heat on one of the corners.

It seems the heat is being generated the component in the picture, at which my bamboo skewer is pointing.

Right next to this surface mount component is an LED marked "class A."

Any guesses as to the type of component that may be? It sort of looks like a TVS diode that I sometimes lift/remove from hard drives that won't otherwise spin-up.

Any idea what that component may be or general troubleshooting ideas?

Thanks in advance.

It's with a heavy heart that I announce the passing of my long term friend, forum member and speaker builder John Busch. John passed away last night, July 3rd. It took a kidney infection, two brain tumors and COVID to finally take him down. John was a tough old farm boy from Iowa, who had worked for Heathkit, brokered sales of large aircraft, ran a wholesale filtration company and loved his bourbon.

John and I met on the Parts Express tech forum almost 20 years ago and became fast friends, working on countless Open Baffle and other speaker projects and attending many audio shows together, such as LSAF and RMAF. John had an uncanny sense of hearing, in level, tone color and in frequency. He also had a vast knowledge of drivers, and loved sharing his knowledge of them. That allowed him to build some amazing speakers. I've never met anyone who built better passive crossovers. He taught me a lot.

John's legacy is his open baffle designs, often quirky, usually huge, but always great sounding. He was a prolific speaker designer and builder, all for his own amusement. To see a little of his work in a simple, easy to build form, have a look at this thread: https://www.diyaudio.com/community/threads/fast-fun-inexpensive-ob-project.110583/

Ive lost my linearx lms install on the pc. The card still passes the self calibration process, so I would like to put it to use.

An older v3.x install would be helpful. However, I don't have documentation for the older versions and v4.x would be much preferred.

Any help or leads would be much appreciated.

Thanks,
Jeff

Dear all,

First, thanks a lot for the amazing forum, I have already stolen lots of ideas here... Great job!

Some time ago I bought an old tube radio thinking it wouldn't work, a Schaub-Lorenz Goldy20, with the idea of building a guitar amp but... it works!! I think it is a pity to destroy it to make a guitar amp, the FM side sounds great (even though should be better for winter due to that temperature XD), but maybe some refurbishing could do?
It actually has an external input so, by selecting LW+MW it does in fact connect the external input to the EABC80 as pre-amplifier, and then the EL84 (I think).

I made a modification in the cathode of the triode of the EABC80, by placing a 10K pot in series of the cathode to ground, and in parallel to the pot a 22nF cap. The idea is to get some overdriven sound by increasing the gain of the EABC80 (positive grid excursions? Like a variable bias cathode resistor if it makes sense).
It actually kind of work, since when it is in FM mode, and minimum volume, rising the resistance of the 10Kpot, the volume rises until it starts to sound distorted. The point is that, when it is in TA mode (by pressing LW+MW switches) it does nothing.
I don't know if:

• The external input doesn't even use the EABC80?
• The AVC (automatic volume control) is cancelling this increase of gain?
• Something I can't even imagine...

Maybe some of you could give me an idea how to move forward...

I post also the schematic with the modification I made. To follow the schematics, the switches labelled L and M in the schema represent the LW and MW switches, needed to select the external output. The position in the schematic show when the selector switch is not pressed.

I would appreciate any help to avoid destroying the radio and still add the guitar amp functionality.

Thanks in advance.

Cheers!
José I.

Does anyone know what is inside this little amplifier? Found here A Kinter A7 with bluetooth

I'm pulling the trigger on it anyway because for 11 bucks and all the other goodies it's a cheapie to play around with.

Shipping is in addition to the prices listed.
Drivers ship from Ontario, Canada.
Please e-mail me for offers, details or photos.
Most of these are new, unused, and in original boxes.
Some are new but loose with no boxes.

Polydax HD13D34 8ohm 1.5" textile dome tweeters
Round faceplates.
Legendary parts used by Monitor Audio, ProAc, Kef, Infinity and others.
Almost impossible to find, I have 3 units in original boxes, unused.
Asking $30 USD each.

Audax TW025A13 4ohm 1" Titanium dome tweeter with chamber.
One only.
Asking $10 USD.

Audax TW025A18 4ohm 1" Titanium dome with neo motor assembly. Excellent tweeters.
Over $100 ea from the usual sources.
One pair available.
Asking $100 USD for the pair.

LPG 26AT 1" Titanium dome tweeter.
Made in Germany, excellent quality.
Multiple pairs available.
Asking $40 USD per pair.

LPG 51AT 2" Aluminum dome midranges.
Made in Germany, excellent match for the 26AT tweeters.
Multiple pairs available.
Asking $80 USD per pair.

Many great parts here.
Thanks for looking!

Hi all,

In the last couple of weeks I put together two nice little 16L sealed boxes for a fellow audio enthusiast. These contain one SB23MFCL45-4 each and the idea is to EQ them in to response submission - all good there.



However, when I was putting them together I expect the boxes to come up a little small in volume as I had added bracing and was expecting to stuff them and lower the Q. They are cubes (265x265x265mm internally) so I knew I would have to tame a resonance anyway so the plan was to lower Q and eliminate the standing wave in one go.

As it turns out the box shows a lower Q and a higher standing wave than expected. The aim was for a 0.7> Q and I thought the standing wave would be around 325hz. However, the Q is 0.66 and the standing wave resonance is 775hz. Perfect but sheer luck!



TBH, I don't think I need to stuff these cabinets as the resonance is so far out of the pass band that with even a modest L12 @ 100hz the resonance is down 40db. I don't really want to lower the Q any more as it is fine for EQing as is.



Any reasons TO stuff? I can't see the resoance effecting the system.


Cheers! 🙂

I bought mum a Sony TC-FX211 a few years ago. The belts are all gummed up so is due for a service... I was thinking I might do a recap while I'm at it. Worth the trouble or not really?
In the meantime, I jumped on ebay to source some belts, but I'm not sure which suppliers are any good? I'm not so sure I can trust dodgy ebay sellers that are just proxies for alibaba and the like... And only to find the new belts stretch and melt after a single summer...
I also had a look at picking up a blank chrome and metal tape just testing purposes... and needless to say my jaw hit the floor! I never knew they were so expensive! LOL
Anyone know where I can buy just one that's affordable? Or even if I could just borrow one as it's only for testing? (I'm in Sydney Australia btw)
Also, it's probably a good idea I pick up one of those wow/flutter test tapes, though I'm not sure what ones are good value for money these days...
Thanks all, in advance.

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Hi I have for sale 2 sets of SEN ( Single Ended IV Kit - PCB/FETs and Special Heatsinks originally offered by EVUL. Contact me by PM. Prefer US member as shipping is economical - Paypal
kannan

I'm looking for some Panasonic FC 100uf 63v caps and and a good film 4.7uF. Pls direct PM to me. Prefer new for lytic and new or used for the film. Thanks

Hi,
attached is a pic and the schematic for the Delta 1010 power supply. Im looking to replace the 470uF 35volt and the 2200uF 50volt electrolytics but dont know how to choose the best brand and series to replace these with.
Any help or suggestions would be greatly appreciated.
Thx

I have a pair of LXmini variations that I purchased assembled a few years ago. The 2x4HD MiniDSP has stopped working - full story here.

I'd like to use these speakers but I have very little experience with DSP, crossovers, or speaker building, and I don't have much time to give to figuring these things out right now.

I'd like to buy some kind of plug-and-play solution that would replace my MiniDSP. Maybe you got the analog crossover and no longer use yours? Maybe you built an analog crossover that you're not using? Maybe there's another option I'm not aware of.

Thanks,
Will

Elekit TU-8500 Pre-amplifier. Employing the finest components this pre-amplifier features Takman 1% and .1% resistors Mundorf Phono Caps, AudioCap line stage capacitors, NOS Sylvania JAN 6189W tubes, and Burr Brown OPA2227P opamps in the phono stage. The preamp is in good condition, sounds great and functions as expected except for a slight 2ish dB imbalance between the left and right channel. I'm not sure if that is a mismatch between the tubes or the stages of the potentiometer but it would be easy to fix by adding a resistor after the pot. Kit price without upgrades is $585. I am asking $450 plus the actual cost of shipping. Box is 12x12x7" and 10 lbs.

I have had a project for an offline switch-mode power supply for a multi-channel power amplifier in mind for a while
While I wait for my business to ease up so I can work on it properly, I have time to think it over, in particular how to make it electronically quiet.
Cuk converters are often discussed as potentially a less noisy option but not without problems, R. Half Plane Zero(es) for a start.
I don't think this is a major issue for an audio amp, transients are fairly slow compared to the switch frequency and the Power Supply Rejection Ratio at audio frequencies should minimise the problems.
But one issue is how much the circuit stresses the (transistor) switches, best expressed as the required switch capacity Vstress * Istress compared to the output power Vout * Iout.
Call this the utilisation, denoted U, typically a function of the duty cycle U(D).
I found a bit of discussion of this in "Fundamentals of Power Electronics" by Erickson, available on the Uni. of Colorado website.
But it seems to have a few mistakes, some of them probably just typos, others I'm not sure.
I have included a short extract, anyone know which edition this is from? Edit: Looks like it's the 2nd Edition
And if there is an Errata list, or if it's different in the later editions? Edit: Looks like it is different in 3rd edition. Not sure if just moved or edited and corrected.
The isolated Cuk looks fine for utilisation of the switch, actually a fraction better than the more common (isolated) Full B. or Half B. if the table is correct...

David

You participants have been awesome and inspiring to my 62 year young dynamic never grew up something, differing opinions. Great interesting and personal response to the Dumpsters Dive post. Gets a little insight into people we really not know at all but usually draw a picture of them in our own colored perspective. That good for everyone to express what they normally would never do face to face. Imagine that? Another cool thing would be to share everyones favorite live performance single song. Mine is Joe Banamassa Mountain Time at Royal Albert Hall on YouTube. Any artist that exposed their soul and unbridled talent in a song that MOVED you post here so we can all share in the genius! Michael

As the title says. I made a separate thread so this might get more views, rather than bumping My For Sale thread. will swap for your choice, but particularly the sets of vcaps or blackgates may be of interest. For the right drivers I would certainly make it worth your while. Mostly looking domestic to minimise shipping large drivers.

I'm posting this in subwoofers because the bass portion (and the crossover to the rest) is the only part I really designed and have questions about, at least so far. This project isn't particularly reproduceable because I used random pulled drivers from cars, though the bass section was designed to be replaced by a dayton driver if/when it fails.

Parts:
-Mids and tweets are self-contained 4ohm 'premium sound' speakers I pulled from a car, and presumeably have their own crossover inside.
-Bass driver is an unlabeled 2ohm+2ohm dvc 8" pancake driver I also pulled from a different car. Should be replaceable with a front mounted DS215-88, though it would need a different grill
-Passive radiator is a Dayton DS315-PR
-Amp is the same 2.1 bluetooth model found in the Blast Box and Executive kits
-Batteries and charger board are the big ones from parts express (5x26650s)

The design is intended to be used outside away from any boundaries. Cones of the woofer and passive radiator were enamel painted and polyurethane coated.

I expected much more of a underdamped/boombox style tuning, with a peak around 70-80hz and a droop extending below that, going by HornResp and WinISD. I figured that would at least make it 'loud' at the expense of flat response. 1m outdoor measurements (not completely away from reflections, but away from the corner of the nearest building at least) suggest that I ended up more of a hifi tuning, with flat response down to 50hz and a steep rolloff below that. I am completely happy with that, both in theory and in how it sounds, I'm just a bit baffled as to how I got there. FWIW I didn't measure with different amounts or no weight on the passive radiator as I was too happy with the response I got.

My main question is; my understanding of crossovers is largely amateur (matching levels), but I hear phase is just as important. Did I just stumble upon an ideal 150hz crossover, given the controls I have and the drivers I'm using? 150hz 1st order HP, lowpass is wide open so ~150hz 2nd order, gain shown down a little on the mid/tweets, as well as maxed out (unhelpfully labelled 'flat'). This appears to have a very smooth phase line all the way through the crossover region, but I don't know if that is what I should be looking at.

Hello everyone, I have an NAD 1020 preamp I bought back in 1980, some time in the 90's the power switch stopped working- I made a lot of phone calls at the time but could not get an answer on a replacement switch, I finally just soldered in a jumper on the bad side of the switch,(double pole switch) it worked until I put it into storage, now using it again looks like the other side is going- light flickers when turning on- I've taken to leaving it on with the volume all the way down when not in use. Does anyone know where to get a suitable replacement switch? If not I'm thinking of jumpering altogether, otherwise the preamp is good- the pots were scratchy when I took it out of storage but I cleaned them up and all are good except for one spot on the balance pot which I never use anyway. Thanks for reading!

I am looking, no luck on the net or in lit., for the dimension locations (angular and circular) for the 12 possible pins for the nuvistor base. Help me if you can!
Thanx, E

Hi all,

I have for some time now been trying to set up a realistic ADC/DAC PSU decoupling capacitor LTSpice simulation model that will give a quite realistic impression of what a given selection of decoupling capacitors will look like electrically.

I have attached a copy of the model I currently use (based on Saturn PCB Design toolkit estimations for trace inductance, - etc.), however, I am unsure as to how to model the internals of the ADC/DAC itself ... ?

Also, when modeling the DAC/ADC power draw as a variable current source, it looks as if the damping brought about by the decoupling capacitors is quite limited - only - 24 dB at lower frequencies and already at ~ 13.5 MHz the attenuation is 0 dB.

I reckon something is amiss here and it would be great to actually have a simulation model that can be considered realistic. Thus, if you have any experience with - roughly - simulating ADC/DAC decoupling capacitor network I'd appreciate your input.

BTW the attached simulation model's DAC pin specs are based on the distant wires (from pin 1, 14, 15, 28 to internal silicon) of an 28 pin SSOP package.

Cheers & have a good day,

Jesper

Hello hobbist,

i have build this kit YouTube, sounds good. I use Hammond 125ese transformer, the transformer has good sound but missing high notes. They sell Edcor transformers in Germany, can you help which one would be upgrade from Hammond 125ese? I mean xse or gxse series. Thx

Recently came across a Silergy's pre-amplifier IC, SA51023, which looks a great performance upgrade to NXP's TDA8579 with 106dB CMRR. Has anyone ever used it before. How's the actual performance?

I'm trying to construct an umbilical for a phono-stage. I am planning on two regulated DC boards in the power supply chassis and a 5-6 foot umbilical to the audio chassis. Each board will supply 1.3A @ 6.3VDC. The connectors I'm using will accept 18 AWG wire in the solder cups. The B+ will run in a separate umbilical
My questions are:
1) Should I twist two pairs of 18awg wire and bundle them in some shielded braid? Is shielding needed at all?
2) Is there any need to twist them at all? Could all four wires be just bundled?
3) Should I source some twisted quad wire? (18awg quad is not easily found though)
4) I have some wire like below but I'd need more to complete the project.
Any of the above will require a purchase of additional wire.
I've read most of the other threads on twisting heater wiring but most of those addressed AC.
TIA
Dave

Hello!

I ran a pair of Mark Levinson No 20.6 for many years. Later switching to a more conservative Sony TA-F808ES to lower my power bill. Not the same color sound as class A but still pretty good

What about you guys?

Stumbled across this free Deringer-Ney contact design handbook. Though most of us aren't designing relay contacts, it contains a remarkable potpourri of interesting design issues applicable to audio contacts, potentiometers, lubrication and connections.

https://www.deringerney.com/resource-library/

I would like to ask where can i find some good cabinet plans for Mark Audio Alpair 10 and 11 MS or MAOP series.

Thank you

Hello, can anyone help me .
I have a PROAC EBS and I have replaced the ATC SM75-150 medium with an 8 ohm medium.
I have done some Wilmslow Audio crossover but the result is worse than leaving it original.
I just want to modify this part of the crossover the ATC SM75-150 that comes from 16 ohm and put the new 8 ohm.
I include the original diagram.

Hello all. I own a TU8600 some month already. I have done a lot of tube rolling and at least I found the tubes like me (12AU7 RCA clear top, Tesla E83CC and EML300b Mesh or ELROG 300b.
Well, using the ELROGs, I have measure the distortion pattern (1Khz, 1Wrms at 8 ohm). Really horrible.. But the sound is wonderful.
Can somebody explain me because this horrible distortion pattern sound so good????

Hi All
I’m considering constructing some Sonab clones. In what brands and models of speakers, radiograms, stereograms, consoles, etc. was the Philips 9710 fitted? In other words from what items could I potentially extract a pair of 9710s?

thanks

PS Please don’t respond telling me “other Sonab speakers”! 🤬

Doug

dave

Phase plug extension for 2" exit compression drivers.
3D printed, 100% solid, .15mm layers.
4xM6 bolt holes on 102mm.
$100.00 per pair shipped to CONUS.
Please PM me for PP instructions.

Somebody could do me a favor…
I am working on a new build, GU-50 PP and in the PCB design phase. I did order tubes and sockets and got a serious question about the GU-50 sockets I decided to use.

If somebody has these sockets, see attached picture, lying around at home, or knows somebody who has, I need some info.
Please post a Straight picture bottom view, onto the pins with the mounting flange on the cage visible. I am trying to get the distance of the mounting holes on the flange on the cage and most importantly the angle of this virtual square —4 holes on the flange— towards pin 1. I have the suspicion that pin 1 is not at 90° (or 45°) to the holes on the mounting flange. It looks like 5°-10° off. I do have the pin layout information, angles, diameter of the circle they are aligned at. Don’t need that. Need info about this specific cage and mounting flange on the cage only.

From that perspective view picture it is impossible to gather any useful information in regards to dimensions.

Daniel inquired about simple, LTP-free discrete designs.

Here are some examples, mostly based on application notes from Motorola, Siemens, RCA, Philips, Sescosem, etc

Anyone looking for a nice 6bq5 amp should really build one of these (SPP). Triode mode,Listening right now through a Broskie CCDA 6sn7 linestage A little hiss through my Lascalas, guess I'll have to work on that power supply.Built two identical amps years ago, this is a revisit.Detailed,dynamic,smooth as silk.Thanks George.Really impressed.

Hi, i have this Ground Zero GZHA4120X, that i never used, i was testing it comparing to other amplifiers (jbl, edge, mac audio, etc etc normal mass market amp) and i noticed that the highs on this GZ are much softer and warmer, almost like it has no highs, to my ears not being that clear on voice and highs...all other amps that i tested had more brighter highs.
Is this a general characteristic of the GZ amplifiers or it might be something wrong with my amp?

Never heared another GZ's amps so don't know if this is how they sound.

This being nice and shiny (2 chrome plates) was thinking to buy another one of 4channels and do an open rack in the trunk, and now i don't know what to do.

Thanks.

Hi everyone,

I've done a small four part review of the Bowers & Wilkins 685 stand-mount loudspeaker. It contains a lot of loudspeaker and driver measurements and some Mod suggestions on how to improve the sound quality of this loudspeaker.

You can read more about it here:

AudioExcite - Bowers & Wilkins 685 review part 1
AudioExcite - Bowers & Wilkins 685 review part 2
AudioExcite - Bowers & Wilkins 685 review part 3
AudioExcite - Bowers & Wilkins 685 review part 4

Regards

/Göran

G'day guys,

I'm tuning a Glassware audio 12vac Aikido board.
https://glass-ware.stores.yahoo.net/aikido12vac.html

I'm doing the 12AU7 implementation.

My heaters are currently running at 12.85vdc.

Is this within an acceptable range of 12.6v or is this likely to shorten tube life?

Is it worth performing pcb to lower the heater voltage or just leave well enough alone?

Hi All

I have just bought a 3020 myself, but have a hum on the right channel any ideas.
Also this bloke is doing a nice 3 way test with the 3020 against the a60 and 8000a its quite interseting to hear the differences in the sonics these 3 produce Login to view embedded media
Rav

This new HPA from Schitt touts an output stage that has no output transformer and no output capacitor between your headphones and the tubes. How can this be?

https://audioxpress.com/news/schiit-introduces-limited-edition-10-tube-dc-coupled-otl-tube-amplifier

Ladies and Gentlemen

I have a defective Mark Levinson 333 here, which unfortunately has a couple of output stage transistors that are defective. Now I've swapped them all (all paired with a Tektronix 576).
But now I would have to set the quiescent current of the output stage, while the circuit diagram I have says that a voltage of 34mV should be set between points A and B. Is it correct?
Or should this value be set from point A to GND and point B to GND?

What is the difference between the 333 and the 333.5 ??

It would be nice if anyone could help me

Hi, I'm new to this forum. I build this little amp with the power output in the milliwatt range and I would love you opinion. Is based in 3 projects. The Alembic Preamp, The Real McTube Power Supply, and an idea from a guy named Kris Slyka where he use a Chinese pentode (6j1) as output (https://hackaday.io/project/177987-the-milli-amp), but he settled for low Voltage (24V) I put his idea on steroid and I increased the Voltage to 120V. It works, the sound is perfect for midnight tones and for me sound louder for what it is. What are you opinions? what would you change? Thanks for your time.


EDIT 07/14/2022.
This are the latest changes, thanks for your help.
-Negative Feedback point was changed (like a vibrochamp).
-Negative feedback resistor was reduced to 2.7k.
-Master Vol was entirely removed
-First transformer was reduced from 18VAC to 12VAC.
-Cathode Resistor of 220 was added.
-Grid leak Resistor was increased to 470k.
-Tone stack mistake was fixed (100k resistor)
-Speaker was grounded.
-Capacitance before 7812 was increased (100u)

UPDATE 07/18/2022.
-Clean Headroom was measured to be 0.15W

Does anyone know what the thing in the photo is?. Looks like it is made for an EL156 output valve. Strange thing found at an auction.

Most ultimate Passive and Active (NFB) Tone Control Network based on Peter James-Baxandall's topology

This was the developer:
https://www.aes.org/aeshc/jaes.obit/JAES_V44_9_PG796.pdf
Around his topology there are a very extrem amount of proposals about google - thus this don't help me.
here some examples and a basic article (overview)
Tone control circuit - Wikipedia, the free encyclopedia
https://web.archive.org/web/20090225070322/http://www.schmarder.com/radios/tech/tone.htm
https://web.archive.org/web/2007012...l.gob.pe/publicaciones/rvargas/red-activa.htm
(analyses of a Baxandall-type Active-Tone-Control Network -
Ing. Ramón Vargas Patrón Lima-Peru, South America July 23rd 2004)
https://web.archive.org/web/2012121...omcast.net/~stphkeri/NegativeFeedbackTone.pdf
Baxandall Tone Control Using CA3140 Op-Amp | Circuit Diagram
http://www.ti.com/lit/an/sloa042/sloa042.pdf
post #30+31 under
https://www.diyaudio.com/community/threads/looking-for-very-good-tone-control-schem.21307/
and post #1 under
https://www.diyaudio.com/community/threads/a-usable-tone-control.199130/

There are two basically topologies:
1) passive version (between two line gain/buffer stages) - go to first attachment.
2) active version - i. e. in the negative feedback loop - frequency dependent NFB (from an inverted mode amplifier and from a non inverted mode amplifier - both in voltage amplifier gain stages (preamp) and power amplifier stages in cases without separate preamp line stage) - go to second attachment.

I need the best circuit topologies for both applications. The most important features for me are follow:
1) the insensibility (immunity) against electromagnetic hum sources and against microphonic effects.
This means, low impedance character (i. e. the contrary of such circuits, where the variable resistors/pots have values between 5 meg-ohm and 10 meg-ohm, often to find in tube amp/preamp stuff and vintage tube audio devices).
2) the establishing of any cutoff frequencies for the lower and upper area

Where I can find such circuit topologies both here on diyaudio and by commercial devices?
Thank you for your advices

Haven't been on the tools for a while. Previously, have dabbled with Altec, Tannoy, Azura, Iwata, Jabo horns.

For my own use, I'm now building a large stereo centre channel speaker, which will also double as my two-channel speaker for the living room. (We live in a unit, so there is not a lot of room.) See pic where the word PEACE is shown...just below the large TV.

Box:

x2 36 liters (1.26 ft3) boxes anchored together, ported, 36Hz @ F3, 780mm wide x 250mm tall x 300mm deep. 18mm MDF, braced.

Drivers:

SB Audience Bianco 44 CD-PK compression drivers, one inch
SB Audience H225 one-inch horn, 800Hz Fs
Dayton RS225 8-inch woofers (Reference Series)

Xover:

Initially, first order @ 1,600Hz to get me started.

Amps:

Cheapie valve/Bluetooth preamp/DAC
Rotel 60-watt power amp

Source:

TV
Bluetooth (Spotify)

Hello dear folks,
does one of the forum members have an idea or a clue if there is such a cabinet for the Mark Audio Alpair 12 P gen. 2 - or in what context these two TL designs needs / has to be modified?

For MA Alpair 12:

http://frugal-phile.com/boxlib/woden/Aln-0v82-map-281209.pdf

for the MA CHR 120 driver:

https://www.kjfaudio.com/wp-content/uploads/2020/04/CHR-120-twin-pipe.pdf

or another example:

https://www.dagogo.com/feastrex-makoto-loudspeaker-system-review/2/

The frugal horn “Joan” or the “Super Pensil” are eliminated from the outset due to their large footprint and the “Avebury” for the 12 P due to its “Empire State “ sky scraping style. To scale a appropriate footprint I prefer a maximum depth of 35cm with a maximum width of 28cm and a maximum hight of 150 cm should’nt be a “huge” Problem.

Even a folded ML - TQWT for the MA 12.2 P with this footprint and a line length above 200cm would fit.

Many thanks in advance for all of your suggestions and tips!

Kind regards

Stefan

Hi folks,

I am considering finding an alternative to a TDA7498E board that I have used for almost 8 months now, because I am getting sick of the low bass issue that the board has. As youtuber Willison audio pointed out, he said that there was weak bass and I agree with him. When I switched from a Class AB TDA7379 amplifier to this one (as the chip blew), using the same speakers it sounded like there is a high pass filter at around 80hz, making the bass seem weak.

I used TI based amp boards (like the tpa3110 and tpa3116), and they all have this power on/off pop that really annoys me (especially with having 92Db sensitivity speakers). I heard that the issue is even worse with the tpa3255 amp (likely due to a higher voltage).

Any ideas on what boards/chips are good? The speakers previously described were some small 3D printed speakers that were low sensitivity and were 4 ohms. The speakers I use now are JBL control 28s and they are rated 87W pink noise and 175W continuous program power and they are 8 Ohms, demanding more power. I am thinking about getting the wondom audio AA-AB32516 or a board based off the IR2092, but the 2092 requires a dual symmetrical power supply that might cost alot. Any suggestions?

Hi

I would like to build a tube amp for headphone. Preferably that can drive 32r load. Main headphone is hd6xx

I have seen bottleneck crack. But shipping is too expensive to asia

Wondering if there is any other alternative and suggestion

Thx in advance
Erwin

$150 shipped, CONUS, paypal F&F or personal check. Please DM for international shipping arrangements, which are likely to be slow and expensive.

This is a completed ACA Mini "almost clone", with the PCB of Mark Johnson's design, obtained via the Group Buy administered by KevinHeem. It features matched Toshiba JFETs and Harris MOSFETs, a gift of Papa's as I understand. It's mounted on a little plinth I made from a piece of salvaged flooring. I'm not looking to make money on the efforts and generosity of others, only to recoup roughly the value of the completion parts I put into it, and to acknowledge that I've hardly listened to it after building it, some months ago, and would rather it were in the hands of someone who will let it sing.

I tuned it to work with the Meanwell brick I use with my ACA, the one that comes in the diyaudiostore kit, which I don't really want to part with as I have a working ACA that needs power. So it is my strong preference not to provide my ACA's SMPS brick. Uou will need your own SMPS brick to use this. That said it was dialed in as follows, warm, some time back in April:

L: 11.67V Vo; 0.30V Vb
R: 11.71V Vo; 0.30V Vb

Thanks for looking. Hope I haven't stepped on anyone's tail here.

Looking for replacement woofers for ar 2ax speakers. The speaker has a rabbit tweeter with dicast frame and cloth surround. Can anyone recommend to replace the unit? I can see there is a cheap one from PartsExpress:

GRS 10PF-8 10" Paper Cone Foam Surround Woofer

Looks dirty cheap but not sure it is good in sound quality.

Thanks,
Peter

what is your opinion about porous absorber calculators online such as:

http://www.acousticmodelling.com/8layers/porous.php
and

http://www.whealy.com/acoustics/PA_Calculator/index.html
how do they compare to high end acoustic softwares and simulations?

i think the above calculators sometimes gives really strange results that just can not be accurate and that contradicts measured performances

Hello I am new here and this is my first post so I do thank you for the opportunity.

I have an old NAD 7240PE that smoked and blew a capacitor when plugged in. This happened several years ago and I shelved the NAD since then. Recently I took it out to visually inspect the PCB and I am using it as a platform to learn electronic components etc. So a bit of an odd ball project. Don't worry though, I love this little amp and will do everything I can to revive it. It has a special place in my heart.

As I was busy removing all the old electrolytic capacitors I also spent several hours reflowing almost every solder joint on the amp side PCB (there are two PCBs in this NAD). I followed up with cleaning the flux off the board with using 99.9% isopropyl alcohol and a brush. To my dismay I discovered that a shiny coating applied over the PCB washed off with the flux. The said PCB now has a rather dull flat looking finish as compared to the other remaining PCB that has been barely touched. I don't know what the name of the coating or finish on the PCB is and whether it is a deliberate process to maintain or protect the PCB or if it is a left over residue from what might have been wave soldering.

The coating, as I call it, leaves the board with a shiny non-tacky finish and makes the green color of the PCB really have a nice punchy color to it. I would like to restore the said PCB with an equivalent material. The remaining PCB does have this shiny surface, as mentioned, still in place and its appearance seems to suggest that it may have applied manually with some sort of a brush or maybe sprayed but it is a bit clumpy to suggest that latter. Does this coating/process have a proper name and can I still buy this material so that the board can be returned to an out of the box finish?

I am leaving a few images of the PCBs as a reference.

---

This first image illustrates what I call a coating. You can see that the lower board has a much shinier finish. On touch, it is non-tacky. It also comes off very easily with isopropyl alcohol.

---

This next image is a the glossy finish coating from another angle.

So Dv247 have let me down on the 4 tins of warnex that I will be using to paint some new subs. I'd ordered these nearly 2 weeks ago and should have been delivered last week but the tracking says they are still somewhere in Germany (at a guess). fail!
Assuming these arent going to turn up before thursday I need an alternative which I can just go and buy in somewhere like B&Q or even a specialist paint centre. any ideas? Would furniture paint be any good?

with reference to the Helios speaker design displaying the ability of wo24p in a compact 35 litre cabinet with passive radiator
, I am wondering why would people still chose 15pr400 as their bass driver,

what qualities wo 24 p is missing from 15pr400 except from the efficiency it self. is there a big sound difference between a 15 inch woofer and 9.5 inch woofer

https://www.ciare.com/prodotto/?codice=HM500

This looks an interesting mid dome, priced around 60 Euros, with an FS of of 550hz and stated usuable range of 700-5,000hz.

Has anyone used or heard it?