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Old 2nd May 2014, 09:02 AM   #581
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Maybe we could use lower compensation with more gain

http://jimmy.thomas.free.fr/temp/TDA...93-MESURES.pdf
page 8 : 6X gain is stable without compensation

so it could be completely stable with a small compensation

Last edited by UltimateX86; 2nd May 2014 at 09:06 AM.
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Old 2nd May 2014, 12:15 PM   #582
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Quote:
Originally Posted by aparatusonitus View Post
No, you are right about gain...also note heavy RC compensation on input to make it stable for such a low gain.
I am wondering at the purpose of such a design ?
presumably low noise ?

3 mhz oscillation at 3.2x gain!
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Last edited by jayadev; 2nd May 2014 at 12:18 PM.
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Old 2nd May 2014, 12:39 PM   #583
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Lower distortion by virtue of greater NFB. Its only handling the bass freqs - there will be greater noise beyond the passband of the woofers by virtue of the RC network (4n7 - 2k2).
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Old 2nd May 2014, 01:46 PM   #584
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Maybe it is not a 3,9X CR if R80 has an impact on the CR

39/((10*2,2)/(2,2+10)) = 21 ...

Last edited by UltimateX86; 2nd May 2014 at 01:53 PM.
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Old 2nd May 2014, 02:27 PM   #585
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At HF the effective input resistor is 1.8k (10k//2k2), giving noise gain X22.6. LF gain is around 4X as you've pointed out.
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Old 6th May 2014, 09:07 AM   #586
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Quote:
Originally Posted by UltimateX86 View Post
http://www.diyaudio.com/forums/attac...7293-hi-fi.gif
Hi Daniel,
what do you recommend as other changes in this diagram ?
Mute and STBY are optimal ?
In fact, what is the best TDA7293 diagram uncompromising ?
Thanks
I do have a Parallel TDA7293 thread that produces an excellent 90 Watts for your very loud party.
However, there's no such thing as uncompromising with audio although there IS the possibility to fine tune per your particular usage.

If you want a lesser amount of compromise, see the SSA discrete amplifier projects (some odd 40 watts of high end sound--quite good!).
Or, if you want a loud blast of rather authentic concert sound (with a palatable tone to make that useful), see my mods in the TDA7293 Parallel thread. In either case, using them for what they're made for, yields best results.
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Old 6th May 2014, 09:45 AM   #587
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Quote:
Originally Posted by still4given View Post
Sorry, not yet. I had another amp that needed my attention. I will try to get to it this week. As good as the one channel sounds this looks promising.

Blessings, Terry
Alternatively,
one may cut the gain and use the TDA7294 with a 13.5+13.5vac through 15vac+15vac transformer (anywhere in that range) and a 1u input cap. The low voltage allows decreasing the gain (and you should). Sometimes even the ill datasheet component values could even work. At the voltages that I mentioned 2k7+60k is "in the ballpark" for an optimal gain divider. One can use 220u cap (plus a suitable and/or crazy bypass) for inverting input coupler, and use 220u (or parallel 220u) for power decoupling. In this case of undervolting, you get the flea power mod, which is excellent unless you wanted to break ears and plaster. As described, it should run cool and stable and image very well.
By description, it seems that you have gotten some fake TDA7294's (the real thing hasn't been seen in many years, so that's not a surprise).
Version 6 ("V6") TDA7293 = old TDA7294 with advanced feature set enabled. Version 7 ("V7") TDA7293 = real TDA7293. Version 6 ("V6") TDA7294 = TDA2030A (lower voltage and lower gain, simultaneously). SO, if it behaves poorly, the power voltage (and gain) is probably far too high for what it actually is.
If your TDA7294 was made in March and version 6, then it is surely a fake, meaning that your power voltage is probably too high for the NEC UPC core (which is delightful, but is a low voltage piece).
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Last edited by danielwritesbac; 6th May 2014 at 09:51 AM.
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Old 6th May 2014, 01:33 PM   #588
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So V6 TDA7293 not good as V7 ?
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Old 6th May 2014, 09:11 PM   #589
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Quote:
Originally Posted by Cuda View Post
So V6 TDA7293 not good as V7 ?
TDA7294 and TDA7293 printed with "V6" and "MAR" is highest probability of a fake. However, there are some authentic chips with that same marking and there's no way to tell by visual appearance. TDA7293's are easier to validate by the clip indicator pin, the predrive output and see if they work flawlessly in parallel without ballast. TDA7294's can't be checked any of those ways.

TDA7294 printed with an entirely numeric code and "SINGAPORE" is probably authentic (and old stock, made carefully, not last week).
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Last edited by danielwritesbac; 6th May 2014 at 09:14 PM.
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Old 19th September 2014, 05:35 AM   #590
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Cool got another fake!

made this , with fbstring : 68k - 2k2-100u100u047u ; 1uf input cap, 47uf bootstrap, 220uf power cap and 38 V rails unloaded, i tested with lamps in series it was ok then without...
it just made a tiny snap, like a match or something... and died!
its the second with 7293
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