That's a weird one, I'm trying to wrap my head around it.So, here's a weird little problem:
The relevant bit of the signal chain is:
Cali76 -> Southampton Ictineo -> HWUA
These are not connected to each other directly, but they are in successive loops of a Morningstar ML-5.
When the Ictineo is active and the HWUA is switched on, but not in the signal chain, I get a high pitched whine.
The high pitched whine disappears when I
1. Switch Ictineo off, either by disabling the unit or by taking it out of the signal chain with the ML-5
2. Switch the HWUA off
3. Put the HWUA into the signal chain.
When I switch off the HWUA and then switch it on again, it takes about a second for the whine to reappear. It alters pitch a bit then settles on the frequency.
The pedalboard is powered by a Cioks DC-7 plus a Cioks 4. They are not directly underneath the pedals.
The Cali and Ictineo are powered off the DC-7 and the HWUA is powered off the 4.
Any ideas on how to proceed?
Since the HWUA is out of the chain I'm assuming only the audio connection is switched and the ground connection isn't, which could mean noise is leaking through the ground connection. But then putting the HWUA into the chain gets rid of the whine? That's where it gets weird. Noise is being generated when it's on but not in the chain, but on and in the chain is fine?