SBGK wrote: 
> Must apologise Triode, have found the solution to the high frequency
> problem. 
> 
> I cut the screen on the usb cable connecting the Touch and the VLink
> 192, instant removal of issue I had been having with 0.7 + better bass.
> (note it was the screen and not any of the 4 wires) So there must be
> ground loop issues which were solved by doing this.
> 
> Hope others can make use of this hint.
> 
> Sound now better than ever.
> 
> Thanks again.

further update.

I was still getting quite a lot of hf noise which I assumed was related
to EDO. Turns out it was due to the usb cable, even though I had cut it
down to 20cm and disconnected the ground and had tried another usb cable
which sounded the same.

I had used wires from an ethernet cable to make up a cable to connect
the vlink 192 to the dac1 via xlr with pin 1 dropped to stop ground loop
issues and drain wire connected to the transmit end.

So decided to make up a usb cable using this wire. It is 24 gauge cat5e
foil screen 4 twisted pair with drain wire. �1.49/m from Maplins.

I connected the v+ and ground directly to the Touch board using 2
untwisted wires, these were kept separate to the d+ and d- wires.

I connected the d+ and d- wires to the usb a plug and the drain to the a
plug screen.

then joined the v+, ground and d+,d- back up in the usb b plug. the
drain wire wasn't connected to the b plug.

result - better dynamics, better detail, better separation, no
sibilance. In fact the best sound I have had out of the Touch.

So the usb cable was rather a critical component in my setup. Don't know
if it was the quality of the cable or separating the v+ and ground from
the d+ and d-, but the effect is pretty big. mind you, if you look at
standard usb cable wires they are really thin, so that might have had
something to do with it.

ps I tried various configurations using a twisted pair from a cat6 cable
and tin foil

twisted pair, unscreened - good detail, open sound, bit hard sounding
twisted pair, foil screen - bit enclosed sounding, good bass, less open
than unscreened
twisted pair, foil screen connected to usb a plug - good sound 

final setup - cat5e cable, foil screen with drain wire (integral to
cable) connected to transmit end, used 1 pair and left rest
unconnected.

http://www.maplin.co.uk/cat-5e-network-cable-ftp-solid-13246

also tried ferrites on the standard cable, that had quite a good effect
of reducing the hf noise as well, though I don't need them with the
above setup.


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