Didn't I tell you not to do this in a previous thread? The datasheet does claim that your amp is short-circuit proof, but it can't be good to be connecting one of the outputs to ground.
Use a proper op amp circuit as your preamp, not a power amp.
Right,
I have done some reading I think I get it now
I did not quite get the difference between the two. So I guess an op-amp to act as the first stage then feeding its output in to an LM386 or similar would be the best bet for a not very noisy high frequency with a decent gain output?
Sorry for this, I only learnt op-amps and audio amp ICs exist about a week a go.
Scouring the internet for a "basic" answer on the main difference between an opamp and power amp.
Anyone know of a site that kinda breaks this down for me?
Is the opamp simply to amplify the difference between two inputs (say the -ve and =ve terminal of my transducer?) to a set gain and then the power amp takes that singular output and power amps it so it can drive a low impedance speaker/headphones etc?
There's nothing inherently wrong with using a power amp as a signal amplifier, it's just not the best use of the circuitry. It all depends on the characteristics of the input and output of the amplifier.
The main problem with using your TDA as a preamp is that the output is not single-ended, it's bride-tied load (BTL). This means that it has a differential output, ie both outputs are "hot". Grounding one of those outputs creates a short circuit, which is very bad.
The TDA is specifically designed to drive speakers or headphones. It is not meant to be used as an intermediate amplifier.
Is the opamp simply to amplify the difference between two inputs (say the -ve and =ve terminal of my transducer?) to a set gain and then the power amp takes that singular output and power amps it so it can drive a low impedance speaker/headphones etc?
An op amp is an incredibly versatile piece of circuitry with near infinite uses. One use is as a differential or instrumentation amplifier. The only common thread between all the op amp uses is that they are mainly used as signal amplifiers. They are meant to drive relatively high impedance loads and can rarely put out more than a few milliamps of output current.
You are correct that a power amp takes the signal and allows it to drive lower impedance loads such as speakers, antennas, and other transducers.
An audio amp is essentially an Op Amp but with the negative feedback internal, the input ground referenced, and the output designed to drive a low impedance.
There are some potential problems with using an audio amp as a small signal amplifier. One is noise. The amount of noise voltage on the output that is inaudible in an 8 ohm speaker may be intolerable when used as a small signal amplifier, especially when followed by another amplifier. The outputs may be a bit unstable when run with no or a high impedance load. The frequency compensation is suited to an audio amp, and may result in decreased gain above 20kHz.
Oh yes, the TDA7052's noise performance is definitely inadequate, looking
at the output noise graph - they don't say what bandwidth for that graph's noise
measurements but it's pretty shocking however you look at it.
Another issue is the unknown bandwidth v. gain behaviour - it claims 300kHz
bandwidth at -1dB, but at what gain level? Bandwidth is likely to fall as
gain increases, so its not clear it can handle 40kHz at max gain (after all it is
an audio amp).
