Monica 2 + gain stage; High pitch noise problem

[spacemen12]

Hi,
I have a high pitch noise commin out of my DAC. I want to get rid of it, but don't know how. Here is how I found that it is from my dac.

Set-up 1:
cambridge 540c v2 (as transport), Monica 2 + Rudolf Broertjes' SS I/V Gain Stage as Dac, passive preamp (resistive serie shunt), gainclone, fe103e in blh

set up 2 (modification of the first set up):
cambridge 540c v2 (as transport), Monica 2 + Rudolf Broertjes' SS I/V Gain Stage as Dac, cmoy, Sennheiser HD250 II

My psu for the dac is an smps that I regulate at 12VDC (Monica) and 15VDC (gain stage) using lm78**. The cmoy is battery powered (18VDC).

I added "Newava Technology S22083 1:1 pulse trans" between the RCA plug and Monica 2.

I have the noise with the two set up. with the passive pre, it is there all the time. With the headphones, is is there only after "3" on the volume pot (zero is at "7").

It doesn't matter is the coax from the transport to the dac is plugged, the noise is there.

I only have a multimeter to test, but I don't know what to test.

Thanks