Buffalo II crackles

[Salar]

Hi,
I am using a Buffalo II in combination with the Placid Bipolar and Single and the IVY III. I am using them since 2010.
In 2017 one of the Placid BP Transistors died, we fixed that.

Now there is a new problem:
After warming up, the combo shows a random crackling, but crackling is not the correct description.
It sounds more like a spike, i.e like a small, single scratch on an LP or like
spike interference a from switch triggered somewhere in the mains line.
I would say time between clicks can vary from 10 seconds to minutes.

The click is channel independent, more on the left channel than on the right,
very rarely both channels click, no matter what source.
But all sources i have in the moment are 16/44.1 via SPDIF.

I checked 4 CD´s from 2 player/sources.

I also switched the combo off for some time and after warming up
the random clicks came back after lets say 20 minutes.
When the CD Player stops playing, there is no click.

I also tested an infinty zero signal over SPDIF and a full scale signal,
but with 30 seconds they might be too short as they to show clicking
for the moment...

Any Ideas?

All the best,
Salar

 

[Salar]

Good, looks like a human error. I built a digital output, parallel to the Buffalo.I attached a simple RCA cable to evaluate another Dac. With the DAC not attached
(or the cable terminated) noise seems to disturb the SPDIF signal