amp crackle

bloomer

Hi all, wondering if anyone might be able to help me diagnose a crackle in my cornford harlequin. Some info that might help, no guitar plugged in:

1. master on 0, volume on 0, no crackle
2 .master on 0, volume turned up even to full, no crackle
3. volume on 0, master gradually turned up, crackle present and gets gradually louder
4. whatever level the master is on, increasing the volume increases the loudness of the crackle and also adds in significant white noise.

Be very grateful if anyone has any ideas!

ICBM

Try replacing the first preamp valve. It sounds like the noise is probably coming from the second gain stage. The volume control is a dual-gang pot, one half before the second stage of that valve and the other afterwards, but the after half doesn't go right to zero, there's a resistor in series with it.

If it's not that, try changing the other valve just to be sure. If changing neither of them fixes it it's likely to be a tech job since it's probably a failing resistor or cap in that same part of the circuit.

Full marks for giving an accurate description of the problem .

bloomer

Thanks very much for the advice, I'll try changing the valve and see what happens.