some help on TDA7293 boards off Ebay - Page 5 - diyAudio
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Old 25th March 2012, 09:29 AM   #41
axa is offline axa
diyAudio Member
 
Join Date: Mar 2012
Hi.

This seems to be the place to discuss / warn people about these cheap amps that you get on ebay. I wasn't using it as a hi fi amp, but I'm sure this will help people considering buying one of these.

My experience with the yuanjing 4 x tda7293 btl amp module, orange pcb

I was using it as a replacement power amp in a 70's Yamaha B100 bass amp. The B100 has a stunning discrete transistor preamp, great eq, beautiful. Unfortunately the triple bias diode in the power amp is very hard to obtain and very expensive if you can get it .. which is why I decided to give the tda7293 a go.
It's now used as the power stage in a peavey heritage.

The information with this product is very sketchy. No schematic, no other specs regarding gain, input voltages, heatsinking etc

One of the important things to note is that you don't earth one side of the output. The output goes straight to the +ve and -ve termainals of the speakers.

Mine had a slight hum on it, acceptable for my purposes, but not hi-fi. It wasn't in a grounded enclosure, so that could have been improved upon, maybe.

The biggest problem with these is heat, I put mine on an ample 35 x 8 cm finned aluminium heatsink, @ an estimated 100W output, the sound starts cracking up in under 10 minutes - I can't see that you're ever going to get the rated 350W out of one, even with fans & a larger heatsink.

My impression of these amps is that they are a bit of an experiment - certainly not a tried and tested item from a reputable company, but for 25, what was I expecting? They do sound pretty good though and it works well enough at low volumes. They do have thermal shutdown and are forgiving to work with, so there is room for a bit of experimentation. If anyone else has had better luck with these, or if I can help them with their project, then please let me know.

I certainly wouldn't go for the boards with 4 chips on them, it might be possible to disconnect the 2 slave chips and get something that doesn't overheat, that would kind of defeat the object though.
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