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TPA3255EVM: Input attenuator value if using a passive preamp design

Jack Frederick
Prodigy 50 points
Part Number: TPA3255EVM
Other Parts Discussed in Thread: TPA3255

Tool/software:

Hi,

This is a two part question:

1--Since the TPA3255EVM has an input buffer built in, I assume using a simple passive preamp with a stepped attenuator on the EVM is fine. If so, is there an ideal value or range for the resistance of the attenuator? I currently have a 48 step series stereo stepped attenuator that is 10k ohms, but I have a 48 step stereo shunt attenuator available that is 100k ohms-- any advantage or disadvantage to using one or the other?

2--Also, this design may only involve having only a single stereo input with this same passive setup. This signal will be coming from a device with a balanced stereo output. Since there be no input selector circuit in the signal path, can I send the balanced stereo signal directly to the EVM's differential inputs via a stereo attenuator? So the volume attenuator would be wired directly between the balanced source and the EVM module.

Thanks

Jack

  • +1
    TI__Genius 9175 points

    Hi Jack,

    I am assuming that your attenuator is just stepping down the signal level from the pre-amp output to an acceptable level for the TPA3255. As long as the output level is within the input level spec for the TPA3255, you could get away with either approach. If you are going for the highest quality audio possible, the 10k may be a better option for lower thermal noise in the resistors of the attenuator, but it depends on the attenuators used. 

    You are able to use differential audio with the EVM (and the TPA3255). You can refer to the EVM user's guide and theTPA3255 datasheet for how to configure the EVM for a single differential input.

    Regards,

    Ramsey