If you're suffering intermittent volume drops on one (or both) channels it could be the series vactrols on the tube outputs playing up. To test - hot air makes them go OC.
An easy permanent fix is to replace with DIY shrink wrapped LED/LDR vactrols, but do both to ensure consistent output levels. Works perfectly.
An easy permanent fix is to replace with DIY shrink wrapped LED/LDR vactrols, but do both to ensure consistent output levels. Works perfectly.