ProtoDAC TDA1387 X8 project

[wolf7250]

Issues of pops. Some issues with ProtoDAC reported to me by a kit customer.

A pop when switching the preamp/amp input to ProtoDAC, with ProtoDAC powered. This is due to the fact that ProtoDAC is missing a "polite part". This part is a resistor from the center RCA to ground. It can be anything from 100k to 1M. It is not included for simplicity and sound quality.

Since ProtoDAC output is not tied to ground with a resistor, a charge can develop when the input of the preamp/amp is switched to another component. Then when the input is switched to ProtoDAC, that charge is suddenly discharged to ground and is amplified. The simple solution is to turn the volume down before switching to the ProtoDAC input.

The signal not passing through a signal to ground resistor is your signal. No resistor is a perfect resistive device (metal foil get close). It also has inductive and capacitive properties. Signal to ground resistors will affect sound quality, especially before an amplification stage. Some advocate for metal foil resistors in all signal to ground positions. That can get expensive. My recommendation is to just turn the volume down before switching the input.

The same customer reports a pop when turning on ProtoDAC with the amp already on. It is best practice to turn the amp on last (ProtoDAC-->preamp-->amp), and turn it off in reverse order.

The third pop is at the start of the first playback track. I think this is module related. My TeraDak TDA1387*8 always made a sound of a record skipping grooves at the beginning of the first track.

I can rarely get a tick after the last track of the playlist.

Thanks! Really great information and advice