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TDA2030A Headphone Amp

post #1 of 5
Thread Starter 

I have a TDA2030A based amplifier that should make a decent headphone amp except that its gain, at about 32 dB, is way too high.

It would be easy to change the gain setting resistor or even put in a switch to change the gain from say 10 to 15 to 25 dB for proper Headphone use. But there is a problem.

 

The TDA2030A data sheet says the chip needs to run at a gain in excess of 24 dB to maintain stability.

 

A resistor could be placed in series with the output. But that destroys damping factor and sound quality. That is not an acceptable solution. 

 

Meier Audio uses the TDA2030A in their Corda Brick. It has switchable gain of -1 to +14 dB. So how do they do that with the TDA2030A?

 

Anybody got a working circuit they will share that gets the TDA2030A down to a stable switchable gain of 10-15-20 dB?

 

Suggestions?

 

Thanks

post #2 of 5

My guess is that the 4 ohm output impedance quoted on the Meier Audio site might have something to do with this, I wouldn't expect the chip itself to have that high an output impedance, so there's almost certainly a series resistor.

 

The TDA2030 is a poor choice for a headphone amp, IMO. It has very high distortion in today's terms and it needs tinkering to get it to deliver a low gain. 4 ohms is an unacceptably high output impedance for a headphone amp given the low headphone impedances commonly encountered.

 

Build an amp with BUF634 or LME49600 or even TPA6120A with an output inductor.

 

w

post #3 of 5
Thread Starter 

Thanks

post #4 of 5

I disagree that low damping factors (due to a resistor in the output) "destroys" sound quality. In many cases I find it to improve things. 

 

Where does the datasheet specify distortion at headphoneish power levels? The plots I'm seeing all stop at 0.1w

 

I don't see any mention of output impedance on the chip's datasheet. While this lack of declaration does cause me to lift an eyebrow, the copious amounts of global feedback and what was hopefully a "reasonable but not quite great" open loop Zo will pull us through. Now that I have made a great argument for this chip having a low low low output impedance why bother? Although the chip has short circuit protection, why tempt fate with nothing between your amp-chip and a TRS jack that *WILL* short the outputs to ground? Stick an insignificant 4ohm5w resistor in there and save yourself a headache. 

 

It is abject stupidity, but incredibly easy to put multiple attenuators in front of an amplifier. You could isolate them from each other with active buffers for basically no effort. Noise may go up, although with such a noisy chip how would you know? 

 

I laugh a little inside when someone cites distortion numbers they cant possibly know in spite of poor noise levels that are clearly stated. 

post #5 of 5
Thread Starter 

I posted this question on several forums. On one of them the original designer of the the Fairchild version of the TDA2030 responded and convinced me to 86 this project. His suggestion was to go with a discrete buffer.

 

Done.

 

Thanks

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