ProtoDAC TDA1387 X8 project

[hifinet]

Using 100 ohm I/V resistors (TX2575) and a NE5532 based preamp with 15dB gain. The same C3/C4 caps and output caps. This sounds very nice. I think the sound quality is better than 420 ohm I/V resistors without the preamp. Bass is better. I am not familiar with the sound of this particular preamp. If a preamp is added, it will determine much of the sound character.

Measured output with the 100R I/V resistor playing a 0dB 50Hz sine wave is 0.235VAC rms. That works out to -14.3dB compared to the 420R I/V resistor and about -18dB from 0dBFS.

If you have 15dB of gain to spare, I can recommend using 100 ohm (or possibly even lower, if you have the gain). I/V resistors in ProtoDAC.

I think a tube preamp will probably have a better impedence match with the 420R I/V. For solid state, the 100R would probably match better.