Need a 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.

As I already suggested to the OP.

Just use the built in attenuator as the volume control, and use an input switch box, like this
http://www.goldpt.com/sw4.html

If he doesn’t want to use them the next best is to turn them up full.

Use the $49 Schiit Sys, which has input switching, is 10kohm and a great match for his 270kohm input ST70 with 1v input sensitivity for full output.

And especially better again if the internal volume controls of the ST70 are completely bypassed.

The ultimate is go direct, and to use the source volume control if used at or above 75%, if not use the Schiit Sys as a preset so the source volume can be used at >75% with it’s remote control.

Cheers George

So I got the Schiit sys but it seemed to have muted the top end. Didn't sound as lively even with the volume turned all the way up. Waiting for my switch box to see how that performs (or ideally not perform 😉). Currently I have my itune from MacBook airplay to airport express and optical link to dacmagic and then directly to the amp. Using the itune volume control, I'm running amp at full volume. This has given me the best sound to my ear at least.  Unfortunately,  the airplay limits transfer to 44khz so best I can get is 16/44 and not the higher resolution files.

So I got the Schiit sys but it seemed to have muted the top end. Didn't sound as lively even with the volume turned all the way up.

This is also a common complaint of passive controls. I'll be interested to hear what you think of the switchbox.