HT40 self-generates noise

Discussion - HT Venue and HT Venue MkII amplifiers. Inspiration from Studio to Stage. The Valve Amp Redefined.
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Posts: 2
Joined: Wed May 16, 2018 2:15 pm

Wed May 16, 2018 2:23 pm

My HT-40 MK II is about 2 months old and I really like it. Lately it has developed a problem.
It has started generating it's own low-level noise, that sounds like static or old-school modem sounds. I have done some troubleshooting, and determined that it will do this by itself, with nothing connected at all, in standby mode! If I take it out of standby mode, the sound goes away. And one more thing, changing to low-power mode will reduce the sound but not eliminate it. This is during at-home practice sessions, so I'm keeping it below half volume anyway.
This is annoying, because standby mode should be silent. Has anybody else had this? Any solutions?

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Posts: 164
Joined: Sun May 08, 2016 8:26 pm

Sat May 19, 2018 8:10 am

Static usually means one of three things:
- bad tubes
- dirty tube sockets
- bad solder joints at the tube sockets

Posts: 2
Joined: Wed May 16, 2018 2:15 pm

Sun May 20, 2018 2:47 pm

TY for the reply.
Since the issue disappears when the amp is taken out of standby (ie, the power stage has plate voltage applied), I am discounting those possibilities, as adding power would amplify them, not cure them. Also, with the output stage off, that sort of noise really shouldn't get through.
I am speculating on these possible faults:
1. Output stage is not really turned off completely
2. Poor shielding is allowing noise form the digital bits thru.
I would love to have a complete schematic of this amp. I was a wireless communications tech for 30 years, and my training and apprenticeship came when tubes were still very much in use (and my career ended in the digital era) , when they were still better at power stages than solid state, and to this day tubes are still the choice in high-power transmitters. Back in the day, some customers were still using 60's vintage all-tube gear, and I had to know it pretty well. And tube theory was still a part of the FCC license exam.

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