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TAS5630evm / OPA1632 Gain

Bernhard Waechter
Intellectual 620 points
Other Parts Discussed in Thread: OPA1632, TAS5630

Hello,

I'd like to use a TAS5630evm board directly on a smartphone or mp3 player. If I do so, the output of the amp is very low. Now I tried to change R62, R66, R68 and R72 of the OPA1632 input stage from 10k to 22k. It's a bit better now but I need much more gain. The smartphone delivers a output of about 350mV. The Tas5630 needs about 6V to bring full output amplitude.

So the datasheet of OPA1632 tells to use values as small as possible for better audio performance. There is also a shematic with 270 Ohms for these resistors?! 270 Ohms to 10kOhms?? I'm a bit afraid of using higher values. How can I solve this problem without adding a addition input stage to the evm?

Thanks a lot.

Regards

Bernhard

  • 0
    TI__Mastermind 37045 points

    Hi Berhard,

    Do you hear any increased in noise with your speakers with the gain is increase with resistors change? The feedback resistor (and the gain) is recommended to be as small as possible for best noise performance. Here is a good apps note on this topic. In this case, it looks the TAS5630 noise will still dominate with your gain change. Do you hear any difference in noise at idle?

    http://www.ti.com/lit/ml/sloa082/sloa082.pdf

    reg,
    Paul.

  • 0 in reply to user5276421
    Intellectual 620 points

    Hi Paul,


    no there is no hearable noise. So you say it's ok to use such high resistors for feedback until it is not noisy and not oscillating?