Stereo amp with TDA7293

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I built one of these amps some years about with the parallel mode boards from jamesaudio but sold them after the amp sat unused for some time.

In a week or two i will be building one again, i have two TDA7293 left from a set i bought on ebay back in 2005-2006

At first i was gonna P2P wire them, but realized a board on ebay is just 6 dollars so i went ahead and bought one.

Where would you place the TDA7293, better than the LM3886 or worse ? Good overall or just a waste of time ?

The TDA7293 does seem to have more "audiophile" and "High End" aura over it though, judging from the kits on various web sites.
 
Do check the boards thoroughly. I have a 6 dollar 7293/7294 combo board where e.g one of the zener diodes is drawn the wrong way round (for the powersupply of the NE5532 (?)) and iirc some resistor values are a little different from what I'd pick (around the uPC1237, I use a 24V relais, but I think there were some other values that didn't make sense).

If your board says NE5532 + TDA7297/93 then you have the same board.:D
 
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OK, different board and you are going to look at it carefully anyway not having a schematic I guess. Good price BTW.
Mine's a copy of taoboa or something board ($6, no free shipping and the accompanying schematic is for a different board :D), my bridged TDA7293/4 board from my same seller ($10, free ship.) does say XY on it.

Have fun building!
 
These boards known for having errors in them ?

I'd doubt it. They couldn't get away with that for long. Maybe something on the silk screen, but there's not much to get wrong on that in this instance, is there? Anyway you'll have to go through it carefully because they are not sending you a schematic apparently. That's probably a good discipline anyway.
 
Well it looks like most of these chipamp boards are based off the "typical application example" circuit in the datasheet.

But why do they show a 22µF feedback capacitor ? This gives almost no bass response what so ever.

In my opinion 100µF is absolute minimum and is what i'll use on mine.

That jamesaudio parallel TDA7293 amp i built back in 2006 had almost no bass at all due to this low value feedback cap.
 
It's not just any mosfet output stage, it uses depletion mode output fets, something i've never seen in audio before.

But i don't really see how that can be better than the quasicomplementary BJT output stage of the LM3886.

And the LM3886 seem much more popular as well, even though the TDA7293 is significantly cheaper.
 
But why do they show a 22µF feedback capacitor ? This gives almost no bass response what so ever.

In my opinion 100µF is absolute minimum and is what i'll use on mine.

Hmm, good to know... So the subamp in custom speakerenclosure and specific active filtering I build in ~1995 had little chance of working properly between 20 and 100Hz?
It had this 22uF capacitor and a 7294 in class H...
 
-1dB at 21Hz is not good enough. Instead try 100µF and 1.2-2k, -1dB around 10Hz and -3dB around 1Hz.

With -3dB at 10-11Hz, a bass drum sounds like a knock on a table.

I experienced this with the LM3886 kit, i turned it up to where the treble was deafening and the woofers barely did anything, wheres with my amps that has 100µF, the woofers flop like tissue paper in the wind at the same volume, which is how it should be.
 

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You can try 220u for bootstrap since the need doubles when you double the number of chips in parallel. For example if you had intended to use 100u for one chip, then use 220u if using 2 chips. See the datasheet.

You can try paralleling a larger cap onto the NFB cap if you want more lowest bass, and you can try an extremely tiny film cap parallel if you want more highest treble.

For clearer midrange and probably cooler running, you can try adding a pair of 220u to the power circuit.

For a bit of filtering, you can try adding ONE 2.2uF Polyester cap at the power input tap (vias) of the amplifier board, one pin of the cap to V+ and the other pin of the cap to V- where the cap could turn some high pitched noises into DC which is more useful than noise. This should make the midrange quieter but clearer, slightly, since the effect is mild.

Gain: Here's the sore spot. These are miller comp amplifiers. Not only does the quality take a dive if you increase the gain (meaning that you'll really want to build a preamp) but also the quality varies by feedback current. In my case, I appreciated decreasing the feedback current with 60k feedback / 2.7k feedback shunt. The larger feedback shunt resistor value also decreases the capacitance requirements of the NFB cap. Gain settings and current in this area will have a major effect on this amp. Just don't set the gain higher than ~23 unless you're prepared to design and add an anti-compensation network--I would suggest adding a preamp instead.

P.S.
To overcome the problem of gain limitations versus modern sources like PC, Digiplayer, I really did add a preamp to mine. I added MooseFet from Classic Valve design, with 0.47 Nichicon ES input cap, 47uF Elna Cerafine//1uF Nichicon ES output cap and IRF510. I bought the boards, the little ferrite beads, the larger value resistors and the trimmers from them, I bought the audio caps from Handmade Electronics of New York, and I bought the shielded transformer and the Fets from Radio Shack. :)
Although all of the prices were individually modest, it did add up a bit.
This expense could happen with any Miller Comp amp since you don't want to increase the gain thereby decreasing quality, and since a bigger power amp doesn't make the computer bigger, doesn't make the digiplayer bigger. . . so there's a gap that needs a preamp.
 
And the board arrived and have been assambled.
A video, the feedback and bootstrap caps are 100µF, the rest are the 22µF specced on the board: TDA7293 - YouTube

http://i.imgur.com/oaqJB.jpg
Hello. Is there any schematics for that kit? View image: 11894868 384879655041406 1923448972 o The sound when i plug the second channel sounds like an echo like a surround when i plug the second input. When only the one is working it is fine. Also when i shorted the two inputs it makes a sound . what could be wrong?all the capasitors are 47mfd exept from the green in the center who is 22mfd and i get the input from the 22Kohm resistors that i have market on the foto because the boards islets have been damaged so i get the input directly from them. Have i done anything wrong? Image codes: 11894868 384879655041406 1923448972 o
 
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