Power Amp and HiFi Berry+ DAC

Diy and Tweaks
1

Hi, Do I need a pre-amp configuration to output from My DAC of can I go direct to a Power Amp? I have a Power Amp I was considering using. If I do need a pre-amp what’s the most elegant solution?

2

In principle you can feed the DAC O/P direct to a power amp. But it is a compromise compared to a good preamp. The extent of the compromise may be fairly minimal or negligible though.

  1. Check that the volume control in the volumio app works OK
  2. Does it always re-start from the position you last left it in? You might not want it to start every time at 100% volume for instance.
  3. Is the input sensitivity of the power amp broadly compatible with the DAC max output voltage? The HifiBerry DAC is reviewed here:

We see it outputs 2.1V - in broad agreement with the HiFiBerry spec.
Now most power amps require approx. 2V for full output so with such a power amp you can plug it in and go.
But, in a less likely scenario, if the amp is a lot more sensitive (say 200mV) you would end up using -20dB on the volume control setting in order to reduce the max. signal on the DAC down from 2V to 200mV. The consequences of this are 2:

  1. You will throw away 20dB of dynamic range on the DAC
  2. If you accidentally set full volume you will overload your amp by 20dB and possibly damage your loudspeaker

The solution to this is to use a passive 20dB in line attenuator in each channel between the DAC output and the amp input. Because demand isn’t very high they are expensive but can be readily DIY’d by someone with basic electronics and soldering skills. I’d use a resistor divider - say 9.2K Ohm and 1K Ohm for approx. 20dB

3

Hi,

@EdW - thank you for the very exact explanation.

i just wan‘t to add 2 more considerations

1.) Leaving out a preamp will save you a little noise (even the best ones have a very little of)

2.) Some power amps do have gain control which will also help. If not - instead of the voltage divider you could also use a good potentiometer (varable resistor) like one from e.g. ALPS

  • and follow the guide lines of EdW - otherway it could not only destroy your speakers but also you’re ears and mood. :slight_smile:

br
Josef