My brother and I are building a 5.1 (6 channel) volumecontrol with OPA134, PGA2310, black gate and polypropylene capacitors. We have finally started this project up, the code has been ready in a draft version for the past year! We had to change op-amp model from OPA627 to OPA134 as the OPA627 had to high DC potentiale on the output, and made the volumecontrol 'click' quite much. Note that you have to use a Sony compatible remotecontrol with the 5.1 volumecontrol.
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Picture of the transformer taken during mounting in the case.