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Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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Old 12th September 2019, 01:41 AM   #451
deafbykhorns is offline deafbykhorns  United States
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Quote:
Originally Posted by adam1016 View Post
Hello, I have been using my 01a for quite a while now, it's based off of Ale's Gen2 Design, and I am still having noise issues despite redoing my grounding, and shielding some of the signal sections. The hum really isn't too bad unless I turn my amplifier up, but the microphonics are a real killer. So much so that if I turn my amplifier up too loud, even with nothing playing, and tap a valve, it will pick up the vibration from the speaker and ring louder and louder. Also, at higher volumes, the tubes will ring on bass notes. I've bought 5 extra 01a's now and these are the least microphonic of the bunch. My chassis is a 12x12 aluminum plate mounted on wood, bottlehead style, connected with umbilicals to my power supply. I know the mounting isn't doing it any favors, but I didn't expect it to be this bad!
Put the volume control on the output
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Old 12th September 2019, 07:57 AM   #452
awkwardbydesign is offline awkwardbydesign  England
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Originally Posted by deafbykhorns View Post
Put the volume control on the output
I use a TVC on the output, which adds another layer of isolation.
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Old 12th September 2019, 03:13 PM   #453
deafbykhorns is offline deafbykhorns  United States
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Originally Posted by awkwardbydesign View Post
I use a TVC on the output, which adds another layer of isolation.
That is exactly what I did, it's the best way to quiet those tubes.
I had a box of 10 tubes, all very microphonic until I added the volume at output. It works with a resistive volume control as well but the TVC works even better. I went to Dave Slagle for mine
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Old 12th September 2019, 04:56 PM   #454
awkwardbydesign is offline awkwardbydesign  England
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Originally Posted by deafbykhorns View Post
That is exactly what I did, it's the best way to quiet those tubes.
I had a box of 10 tubes, all very microphonic until I added the volume at output. It works with a resistive volume control as well but the TVC works even better. I went to Dave Slagle for mine
TVC or AVC from Slagle?
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Old 12th September 2019, 06:35 PM   #455
euro21 is offline euro21  Hungary
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01A question
Quote:
Originally Posted by awkwardbydesign View Post
I use a TVC on the output, which adds another layer of isolation.
Without low output impedance transformer (for example next stage /SiC/FET source follower, or -at least- CCS/gyrator as active load of tube) it's a bit optimistic advice. :-(

01a has very bad behaviour to such complex load (very high inductance+not so low capacitance) as AVC/TVC. Low output impedance driver helps a lot.
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Old 12th September 2019, 06:42 PM   #456
euro21 is offline euro21  Hungary
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Originally Posted by deafbykhorns View Post
10 tubes, all very microphonic
Unfortunate collusion.

I have a dozen of Sylvania 10/10Y tubes. Non of them -very- microphonic in my 10/801 preamp.

I usually use graphite anode 801 tubes, because it's musicality is outstanding.
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Old 13th September 2019, 01:28 AM   #457
deafbykhorns is offline deafbykhorns  United States
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Originally Posted by euro21 View Post
Without low output impedance transformer (for example next stage /SiC/FET source follower, or -at least- CCS/gyrator as active load of tube) it's a bit optimistic advice. :-(

01a has very bad behaviour to such complex load (very high inductance+not so low capacitance) as AVC/TVC. Low output impedance driver helps a lot.
Quote:
Originally Posted by awkwardbydesign View Post
TVC or AVC from Slagle?
Using his AVC modules
They work fine driving a 6E5P on my GM70 amps
It also drives my solid state s500 threshold without a problem
No source follower required
The added plus of the autoformer at the output is that your output Z worst case will be the Rp of the tube and will quickly go down as you attenuate. At -12dB you will be around unity gain and have a Z-out of around 600 ohms.

Last edited by deafbykhorns; 13th September 2019 at 01:51 AM.
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Old 13th September 2019, 01:25 PM   #458
awkwardbydesign is offline awkwardbydesign  England
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Originally Posted by deafbykhorns View Post
Using his AVC modules
They work fine driving a 6E5P on my GM70 amps
It also drives my solid state s500 threshold without a problem
No source follower required
The added plus of the autoformer at the output is that your output Z worst case will be the Rp of the tube and will quickly go down as you attenuate. At -12dB you will be around unity gain and have a Z-out of around 600 ohms.
I considered an AVC, but bought a pair of Sowter TVCs already made up into a pre very cheaply. I wondered if the lack of isolation with an AVC might cause any problems, but have no experience of them.
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Old 13th September 2019, 02:05 PM   #459
merlin el mago is offline merlin el mago  Europe
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I own an AVC and only needs a low source impedance to works.
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Old 13th September 2019, 03:54 PM   #460
Cappy is offline Cappy  United States
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Ale's excellent Gen2 01A design = 18.55dB (or 8.4) gain.

Typical CD Voltage in to the preamp = 2v. That is a pretty high voltage out = 2 * 8.4 = 16.8v .

This is going to swamp the capabilities of most AVCs or TVCs, when they are put on the output of the preamp -- too much voltage in.
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Last edited by Cappy; 13th September 2019 at 03:57 PM.
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