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-   -   TDA 7294 DMOS IC ? (http://www.diyaudio.com/forums/solid-state/1121-tda-7294-dmos-ic.html)

Ricren 12th November 2001 05:49 AM

Hi,
Have anybody used the TDA 7294 DMOS Power amp IC ?
I'm considering building some two-way active biamped speakers and they seem to fit very well. The proposed circuit from the application note is very simple, and the price is right.
Also, I've noticed that some commercial designs use this chip, like Event and Tannoys biamped active speakers and I guess a few more too.
Besides, they seem to be free of some problems that National 3886 exhibit when they work near the limit.
Anybody?

Samuel Jayaraj 12th November 2001 08:48 AM

Yes, I have constructed the version of the TDA7294 that appeared in one of the Elektor issues. One of the parameters referred to in that article was that the rating of 100 watts output rated by the manufacturer, the device's Pd will well be exceeded. Hence, the voltage was lowered and the circuit was configured to deliver 50w into 8 ohms and 80w into 4 ohms.

I should say that the sonic qualities of this amp leaves much to be desired. Midrange was totally withdrawn, the bass was tight and the high frequency not transparent enough.

Look elsewhere for an active speaker system. How about the TDA1514 which is a much better device?


Ricren 14th November 2001 07:09 AM

Sam, tks for the advice.
About the " not so great sonic qualities" issue, I have to agree. There's something there that is not top qualitiy, but I'm afraid the same can be said of the rest of the offerings that I know. DO you know of any commertial speakers that use the 1514?
.
As I said before, the 7294 is inside the Tannoys 800 monitor powered speakers. It's a biamped design, one IC for each band. Tannoy sells them as quality studio monitors. I've tested them. and they do not sound bad at all,but not great.
Another studio monitor thet uses the 7294 is from Event, the model 20-20bas. It carries 3 of them, two in a bridged configuration for the woofer and another for the tweeter. I've listened to them and they sound OK. Again,not great.Not Genelecs, not Dynaudio.

About your recommendation of the TDA 1514.: I did a search for this IC and got some info, like specs and pricing. but couldn't find a supplier of this chip in USA, only. a web page of a German reseller.
Also I found an informative article here: http://www.dckits.com/app1.htm
They compare the 1514 with the 3886 and apparently they are very similar..I'll copy a part of this report:
----------------------------------------------------------------
>I've also found that although the LM3886 has higher output current capabilities than the TDA1514, the LM3886 requires higher voltage supply rails to produce the same power as the TDA1514. On the other hand, the LM3886 performs nicely at voltages that will destroy the TDA1514. "Sound quality" between the two is virtually indistinguishable although the specs make the LM3886 look better on paper. Connected to good speaker boxes, most listeners would not be able to tell which was which, the very few who could distinguish they were "different" would not be able to reliably identify which was which...

My own preferences are for the TDA1514 in automotive applications where power comes from a regulated switching power supply (we use pulse Amplitude modulation rather than pulse-width, but that is a different topic altogether), and the LM3886 for line-powered applications where a transformer can be used to provide an unregulated supply. Neither chip is useful in BTL mode for driving 4 ohm loads. As popular as 4 ohm speakers are in car audio it isn't practical for DC to offer a kit that uses either chip in BTL mode, and price considerations would make such a kit rather expensive. For 50 watts, either IC makes sense economically. For 100 watts and higher, discrete transistor designs make more economic sense when production quantities are involved. For the do-it-yourself builder, an extra three or four dollars is insignificant in a $50.00 to $100.00 project. For production quantities that $ 3.00 is quite signficant.
----------------------------------------------------------------------

So I think I'll have to re-evaluate my options. The main reason that I like to go the Power IC route is that I need 5 biamped powered speakers. That's 10 amps to built. So, the more simple, the better.If someone have an idea, I'd be glad to listen.
cheers

Ric



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