TDA7293 IC

Status
Not open for further replies.
Jump to Latest
S

santitrucco

Member
Joined 2004
#1
Hi , friends.
Iam building an stereo amplifier with tda7293.

I prefer sound quality , not maximun Watts for output power.

I would like to use Feedback closed loop 22k resistor with 1k shunt resistor..

Do you believe is a problem use those resistors values ?

Thanks you a lot for your responses.

Santiago
 
#5
Spec sheet says closed-loop gain must be > 26dB (20x). Therefore, 22k/1k is fine (and I've used those TDAs at gain=20), but only when you don't have unknown capacitance at the output and you know exactly what you are doing. Definitely *not* recommended for a general purpose amp.
 
#11
santitrucco said:
I have 30+30vac transformer , maybe 42vdc.
Is posible with this voltage obtain a good hifi amplifier ?
or i need less v transformer , like 25+25v ac transformer ?
Click to expand...


Daniel recommends supply rails of maximum +/-33V (posting #7) and a 2x22Vac transformer (posting #13). Daniel is probably one of the most experienced in making TDA7293 sound good. Also, there is a tendency that when you use a chip-amp nears its maximum supply voltage the stability of the loop with output voltages near the extremes becomes marginal. I would rely on Daniels expertise.
 
#16
Kay Pirinha said:
Both datasheets show applications in class G or H (don't know exactly), which allow using rails of +/- 40/20 Vdc and +/-48/24 Vdc, resp.
Best regards!
Click to expand...

The problem with 40 volts is the regulation of a none regulated power supply. This can change by as much as 10%.
Also at 40 volts you can easily over drive the chip amp if too heavy on the volume control.
Even at 35 volts you can easily over drive the chip amp.
 
#17
Kay Pirinha said:
In details they aren't identical...
Click to expand...
It is slightly more complicated.

Current TDA7294/TDA7296 are functionally similar except label. Maybe a die-shrink. For stability, use the TDA7296 datasheet. These make delightful 8W amplifiers or useful 20W amplifiers, but pushing it much higher makes mediocre results with less longevity. Best used for its strengths--small scale.

NOS TDA7295 and TDA7294v-Singapore, aren't in current production. These match the TDA7295 datasheet.

TDA7294 Stereo caveat: If you want stereo, order extras. Getting the earlier and current part shipped in the same box is a frequent problem and your stereo channels won't match that way. Avoid the problem by buying TDA7296 or TDA7293.

Current TDA7293v6 matches the full featured authentic TDA7294S, no 'nc' pins. Here is the datasheet: TDA7294S datasheet(1/13 Pages) STMICROELECTRONICS | 100V - 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY
Using it as a ~44W high fidelity amplifier is far less labor than pushing it.

Authentic TDA7293 is the version 7, big, shiny, and available special order from ST, maybe in lots. This is the part that matches TDA7293 datasheet.

For all:
Four iterations of same part by voltage range indicates simplistic small signal section with fixed values...instead of using CCS that could have helped it track output variances better.
If over-volted, including the datasheet headline figures, variance while driving a speaker is high so that you either use more gain or it loses stability at high output, eventually 'wearing out' or explode.
If under-volted, variance while driving a speaker is much smaller, so you can use lower gain and get higher quality. Remaining completely stable while driving a reactive load also brings the heatsink expense close to trivial.

Compare:
If more voltage at the amp, loudness difference at the speaker is only a couple of decibels, and given the higher distortion, the higher amplifier voltage example gives a Decreased proportion of useful signal. For these chips, disregard voltage headroom because current headroom is more important for them. This is mainly a problem with the small signal portion's limited capacity to track variance, so it doesn't apply to chips set in slave mode per the datasheet.

Workaround for any TDA7293:
Make a normal amp, then set it to slave mode, replace crude inbuilt small signal amp with a driver chip, discrete parts small signal, or make a tube hybrid utilizing the TDA7293 output FETs.
 
Last edited:
#18
FauxFrench said:
Daniel recommends supply rails of maximum +/-33V (posting #7) and a 2x22Vac transformer (posting #13). Daniel is probably one of the most experienced in making TDA7293 sound good. Also, there is a tendency that when you use a chip-amp nears its maximum supply voltage the stability of the loop with output voltages near the extremes becomes marginal. I would rely on Daniels expertise.
Click to expand...
I wouldn't promise that you can rely on my expertise. Fortunately, that wasn't involved. It was actually labor. And, that is somewhat more reliable.
Also, thanks!!!! Loop stability is right, preferably measured at the onset of clipping, while driving a real reactive load. That also helps to identify what chip you have.
JHUSTON said:
Save yourself tons of money. You can purchase non working AudioSource AMP 100s on Ebay for $35.00. They are 2 channel amp with toroid and it uses TDA7294. Same basic IC
Click to expand...
This sounds like fun! However, what is the voltage of that transformer? I'm thinking that if they pushed for power, the voltage isn't suitable for optimal results with chips. However, maybe it would suit a discrete amplifier?
 
#19
Daniel,
is it possible to combine the »modular« approach with the »economic« approach in the TDA7293 datasheet? That means paralleling the output stages of two or more chips and arrange them in a class g/h (whatever it may be...) environment?
Best regards!
 
#20
The g/h topology relies on the 7293 output stage running the lower rail and handing off to an external output stage for the higher rail. IMO, with that complexity, there's dozens of kits that provide much higher performance.
 
Status
Not open for further replies.
Top Bottom