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AlterAnthony
8
May 27, 2019
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My CTH+SDAC arrived a few days ago and everything is working fine in general. I've only noticed one weird issue. With the amp turned on and while wearing headphones, if I touch the volume knob, tap or run my finger on the chassis, I can hear the sound of my finger interacting with the metal through headphones. Not a hum, not static -- literally the physical sound my finger makes. Basically, it's as if the amp was acting like a microphone for mechanical vibrations. I was wondering if anyone here encountered the same issue with this amp or somewhere else? I'm at a loss as to what could be causing this. Perhaps the tube? Thanks!
May 27, 2019
Shredder
39
May 27, 2019
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Yes, actually a microphonic tube will be the most likely cause of this. I got this amp about 6 months ago and it has been a joy to swap tubes and explore how the sound changes between companies and tube types. One thing I do notice is that some tubes are more affected by vibration than others: they are microphonic. A tap on the desk is translated to a strange tone coming from the amp, sometimes even during songs, touching the amp is even worse with these tubes, likely the same thing you are hearing. If this bothers you, you can swap the tube and try other tubes in the 6dj8 family: 6922, PCC88, 7dj8, 7308, & etc. For a very sturdy tube, try Voskhod 6N1P-EV, for good sounding tubes, try 7308/E188CC, and for a balance of sturdy and good sound, there are JAN/military spec tubes that are fairly sturdy. Also phillips PCC88 was very sturdy and good. Honestly, I've found good tubes of all types. TL;DR: roll your tubes, enjoy experimenting or study up and invest in a tested one.
May 27, 2019
AlterAnthony
8
May 27, 2019
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Many thanks for the info!
May 27, 2019
AlterAnthony
8
Jun 1, 2019
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For anyone who might encounter this issue in the future, @Shredder got it right: the problem was a faulty tube. Replacing the tube solved the issues.
Jun 1, 2019
Keno18
1
Jun 5, 2019
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I'd put money on the tube. It's called microphonics. Some tubes are more prone to it than others. It's when the elements in tube (filaments, grid wires, etc.) pick up vibrations and act as a microphone.
Jun 5, 2019
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