Weird crackling from speakers when preamp connected

I sent the preamp to the manufacturer and he couldn’t figure it out (he retouched some solder joints, replaced a few resistors, and declared victory); luckily the local technician did.

@OP Assuming the VTL has a non-captive mains, try a different mains cable. Also, try plugging into a different mains socket.

Check if any new source of RF could be present since you sent the pre for service.

Those are long shots as crackling is almost always a bad joint, cap or tube - but they are worth a shot on the basis of ruling things out.

I remember Davy O’Brian telling me that at  McIntosh they cleaned contacts until they got tired of cleaning them. Then they used sealed rotary switches. Then then had to drill holes in sealed rotary switches to clean the contacts. I have a similar problem on my c28 preamp. I turn the rotary switches all the way in one direction and then all the way in the other 4-5 times. My problem may not be your problem but it is cheap and easy. 🙄🖖

https://forum.audiogon.com/discussions/crackle-from-tube-preamp?highlight=speaker%2Bcrackling%2Bbad%2Bpreamp%2Bcapacitor

maddog,

 I had the same issue after I bought some NOS tubes. I thought I would clean the connections with DEOXIT to bring back the shine and theoretically improve the connection. Silly me, I forgot to dry off one of the tube's pins from the wet DEOXIT. It was then throwing some aggravating crackling and drove me nuts until I took my air compressor to the socket and gave it a good spritz of air. That took care of my issue. It was only in one channel though. Good luck!!