Need a preamp?

The Nobsound doesn’t mention if the two balanced and RCA inputs and/or outputs can be used at the same time. I suspect not. It appears to be just a volume controller for a single source.

Interesting since any active preamp would seem to add some colouration.

That's a matter of intense debate. Many think that no preamp has its own colorations too (of which I mentioned earlier).

@jaferd,
I have the Parasound A21 with my Backert Labs tube preamp.

Many think that no preamp has its own colorations

Then they are kidding themselves

No preamp is "true to the source" with no colourations.
As the output stage of the source is just as matched to a poweramp input, as it is to a preamp input, in nearly all cases.

The "only" time a direct source to poweramp can get "coloured", is when the digital domain volume control is used down too low (<75%), then "bit stripping" can occur, which is a lowering of the 16bit resolution to 14bit or 12bit 10bit ect.

If this is happens then it's best to leave the digital volume control up full, and use a passive preamp, the next least coloured way of controlling the volume, and you can also "use it as a preset" to enable the digital volume control in the source to be used up much higher (>75%) then so it does'nt "Bit Strip" 

Cheers George   

Then they are kidding themselves

Actually they aren't. Loss of impact is the most common complaint aimed at passive controls (the exception being when the control is already in the power amplifier). Loss of impact is a coloration.


The problem is that in many circumstances the digital is making so much output that the volume control can't be run up to full volume, so the user is not able to find out how much impact is affected. And this doesn't happen universally. So like so many other things in audio- you just have to try it and see. But in this case, there's no point in an outboard passive control, since the OP has controls built into his amp. He only needs a switch box.