Speedball problem?

[karl.sandqvist]

Ok, I might have located the problem using a chopstick. I did not play music, only listened to the hum. There's something going on in one or some of the solder joints at the top of the stepped attenuator.  I'm too tired right now but tomorrow I'll desolder all the wires from the attenuator and clean everything up. Then carefully solder all wires.

I'll report back once done.

Thanks PB for helping a noob out!

/Karl

[karl.sandqvist]

Ok, desoldered attenuator wires, cleaned up excess solder, resoldered. Still hum in headphones. The hum can be described as a low freq hum with intermittent faint disturbance on top.

It doesn't change by poking the attenuator anymore. I have tried to go through more or less every joint with a stick and resoldered quite a few joints because the poking did change the humming sound.

I'm running out of ideas again. Any suggestions?

/Karl

[Paul Birkeland]

Is there anything else in the amp that isn't stock?

[karl.sandqvist]

The RCA sockets are not stock, everything else (but the attenuator) is. I wanted to keep the bild as stock as possible and get everything working before upgrading parts. I did install the attenuator from the start because I knew I'd have to redo the braiding wire between pot and rca plugs If I'd done the pot upgrade later.

I've listened with my better tubes, 5998 and Mazda 12au7 and I think I have a typical 50hz hum going on. There's not much intermittent disturbance going on, merely a quite consistent quite low hum. If I turn up the volume a bit I don't hear the hum, only in quiet passages.

No effect on the sound when fooling around with the tubes, when doing the chopstick test I found the power tube to be the most sensitive to poking on the joints, even after reflowing almost all of them. I will be a very lucky man If Inget this working, the potential sq is outstanding! Even through the hum!

What to do other than continuing With the chopsticks?

/Karl