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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Philbert
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?

User avatar
8len8
Posts: 180
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

Philbert
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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