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Transformer-fed TDA8932 25W/8R mono amp kits

@ernesternest LM317 doesn't have a ground pin as its adjustable. The Vref for it is being set by a pair of zener diodes. I've never used TPS7A4700 but from the DS it looks as though you set the output voltage using internal resistors - you would need to set it to the max 20.5V by grounding all the control pins. Then the zener diodes on the PCB would be redundant.

Guglielmo - LM317 is U3 that's the only one I'm using the shunt reg on. A shunt reg replacement for U4 would be impractical.
 
Hi everyone,
posting this here for all to see and also because a credit should be given when due!

Stumbled upon this thread while looking for solutions to lower the gain of two TDA8932 amps which i absolutely love. After reading the whole thread i realized i won't be able to do the smd soldering myself so i asked Richard if i could buy the finished boards instead. The answer was yes and a month later
(due to covid related shipping disruptions) i ve got the two boards. Now, i must say i was surprised to see this level of quality at this price.
I mean the packaging was courierproof, the soldering top notch and cables were also included which made conecting the amplifiers a breeze.
Now, the sound...I have sold all, and i mean all my other amplifiers including a Bryston dual mono when i furst incorporated 2 TDA8932 blue boards in my system, later replaced by 2 red boards. The satisfaction i was getting from these made me realize this is the way to go for me. I run my system on 12v batteries so i asked Richard if he could do a 12vdc version of his mono amps. He said yes so fast forward here i am listening to Music, writing this. Been listening for a month now and can't get enough. Honestly, since they are battery powered and all, theres no ear fatigue or any hint of distortion that i could normaly hear with my old system ...i'm talking 6+ hours listening sessions and still not enough. Piano sound like piano, cymbals sound like cymbals, that sort of thing! Spent half my life playing and recording music so not a newb in this regard.
The little chip chinese boards are good, raw, wild...i love them. Richard's design however is on another level. Its hard for me to describe the difference but i feel the Monoamps have a better grip on the music. Total authority!
Anyway, what i am trying to say is if anyone is in doubt - don't be! Just go ahead and get these. You will not regeret it. Might end up selling your other amps though :)

Thank you Richard once again! You are a master of your craft!

Ross
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Fantastic news. Thank you for the great feedback and encouragement Ross! I have been lurking here for some time contemplating different Class D amp options to try. I will follow your advice then – “Just go ahead and get these.”

As a matter of interest – what preamp are you using here?

Thank you for posting pics of your setup. Good to see other plank amps and a plethora of cables. So, I’m not alone. Reminds me of the telephone exchanges when I was a kid. Oops, I’m giving away my age.
 

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Hi twocents,
Just go ahead and pull the trigger. I cannot see you being disapointed. The Monoamps fitted perfectly in my system. Just PM Richard (abraxalito) and he will advise you.
I am not using any preamp, just 10k pots, generic ones, one for each amp. I havent felt the need to go overboard with anything in my system. I stream Spotify via wifi on Arylic Up2Stream V3 Pro (i chose that one as it has a DSP) feeding Khadas Tone Board DAC and a cheap Subamp. The Subamp is powering two tactile transducers, which i installed in my bed, but could be installed in a sofa or a chair depending on how you like to listen. Now this a game changer for me. I do not use subwoofers. The Subamp volume is also independant. This way you can control the amount of bass as no 2 recordings are mixed/mastered the same. The DAC is feeding the Monoamps through the 10k pots. Amps powering two Fane Sovereign 12-250TC. The cables are leftover from an electrician doing a job on the house. Yes, the cheap, twin and earth ones. Have not heard better yet. The Fanes are triple cone full range, so no crossover, in 50l aperiodic (or should i just say poorly sealed) boxes, going up to 17kHz covering all my needs. The two amps, the DAC and the V3 Pro are 12V 7Ah SLA battery powered, the Subamp is powered by 12vdc adapter. No distortion is evident. All is pure music. Of course this is subjective but if i wanted to mesure i would have gone to the scienists forum.
I think i just described music paradise 🙂
 
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I think i just described music paradise 🙂
Thank you for sharing details about your music paradise. Great to know that you can drive this amp directly from a (2.2 Vrms output I assume) DAC. I also seriously considered those Fane drivers and would love to try them, but SWMBO will never allow two 50L boxes in our house. I am restricted to a smallish area in the lounge for all my audio projects and endeavors.

Thanks – I pulled the trigger. It was easy. I will report back one day.
 
Oh, lol, thanks.
Something that us less complicated than I was expecting.

I was wondering if this was a way forward.
Used car batteries are kicking about all over the place.
What i've found is that each amp must have its own battery. The sound degrades otherwise. I have four, one for each component of my system. The subamp does not need to be battery powered. They go as little as 11GBP at CPC, Farnel etc. for 12V 7Ah. The ones that power the monoamps last for about 10 days and the once for the dac and the streamer for about a week depending how long i listen. Charging time, depending on the type of charger is about 12 hours, Car batteries should last way longer if you have the space but they are pricier. This way all is fitted in a 300x300x420mm box. Of course one could argue if this is the way forward...i was considering buying balanced mains unit for 500GBP but decided to go the other way. My whole set up is less than that, including the speakers.
 
Thank you for sharing details about your music paradise. Great to know that you can drive this amp directly from a (2.2 Vrms output I assume) DAC. I also seriously considered those Fane drivers and would love to try them, but SWMBO will never allow two 50L boxes in our house. I am restricted to a smallish area in the lounge for all my audio projects and endeavors.

Thanks – I pulled the trigger. It was easy. I will report back one day.
Those Fane drivers are the best i've tried so far. They need to be eq'd a little as they're too shouty by nature. I've had severel projects of my own and also plenty of pro monitors during the years. My partner never liked any of them. Once i built these ( put the Fane drivers in old 70s cabinets) she said '' These speakers sound realy good!'' And this was before i went with Richard's Monoamps. Now they sound even better. After 10 years i was able to please someone who is very hard to please :) Of course that was not my intention... 50l is not that big at all. And to get any decent bass performance i think you need at least 12''. Cannot stress enough the importance of the tactile transducers...Theres so much information in music that youd rather feel than try to hear.
 

jean-paul

diyAudio Moderator Emeritus
2002-09-20 7:20 am
Germany
Oh, lol, thanks.
Something that us less complicated than I was expecting.

I was wondering if this was a way forward.
Used car batteries are kicking about all over the place.
One must ventilate adequately when using lead acid batteries. Personally I think these don’t belong IN a home although I used themself in the past.

They have optimal lifetime/performance when kept between 20 and 25 degrees temperature. Make sure to distribute DC power safely and use sturdy cabling, switches and correct fuses. The most important being the main fuse located as close to the battery as possible. Mechanical switches will wear out so maybe the main switch could be a mechanical heavy duty type and distribution with very low RDSon MOSFETs. Each group should then have its own fuse adapted to the load.

Optima Red top 50 Ah is a good type but it has scary short circuit current.
 
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One must ventilate adequately when using lead acid batteries. Personally I think these don’t belong IN a home although I used themself in the past.
Ah, right, thanks.
I thought there might be a reason I didn't see them used more often.

I use an old car battery out in the garage for a little pi zero playing music.
It is well ventilated.
Main reason was to free up a socket.

I was pondering them indoors.
 
@ernesternest LM317 doesn't have a ground pin as its adjustable. The Vref for it is being set by a pair of zener diodes. I've never used TPS7A4700 but from the DS it looks as though you set the output voltage using internal resistors - you would need to set it to the max 20.5V by grounding all the control pins. Then the zener diodes on the PCB would be redundant.

Guglielmo - LM317 is U3 that's the only one I'm using the shunt reg on. A shunt reg replacement for U4 would be impractical.
Hello Richard,
I really liked this amplifier and would like to build my second pair, but it would be nice if I could provide as an extra, the kits of a shunt regulator with the same footprint as the LM317 to use instead of the U3 so no modification to the original pcb would be necessary.
What do you think about?
Thanks for your infinite patience.
 
Hi Guglielmo - thanks for the suggestion. We already have that shunt reg as a PCB but it gets too hot - as shunt regulators do tend to run rather warm - so I'll look into improving the heatsinking and let you know when (or if) we have a solution. You'd need to modify the components on the PCB to use the shunt - the zener diodes feeding U3 need shorting out (replacing with wire or 0R resistor) and the resistor feeding them (R15) needs to be removed.
 
I would suggest maybe getting a parctice board off aliexpress or something.
I had not done smd before. (I haven't done this kit, but have done the Kubelik, this is on my list.)
A few things that I found helped was 0.3mm leaded solder, and I used this tip:
https://uk.farnell.com/pace/1124-0001-p1/tip-cartridge-td-100-0-8mm/dp/4132130

You will want some tweezers.
Plus something to drop the components into when you drop them out of their packaging so that they don't bounce into next door.
Plus a decent mount to hold the pcb. You want no wiggling about.
 
Sorry, I just looked, the one I got isn't there any more.
It was Luxianzi (the make)
We had a discussion about it in the kubelik thread, it seems some different ones are available depending on where you are, so another suggestion might still be there.
I am quite pleased with my stand.
I made it with a sheet of metal and the pcb stands are stand offs with doughnut shaped magnets at the base.
 
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