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peterfarrington64
Joined: 19 Nov 2004
Posts: 2
Location: Staffordshire, UK
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 Posted: Fri Nov 19, 2004 5:09 pm Post subject: Vox tone circuit query |
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I was wondering the source impedance of the driver circuit for the Vox tone stack was correct. For the classic Vox amps a cathode follower (similar to Bassman/Marshall) feeds the stack, so I'd expect the source impedance to be about 1/gm, approx 1kohm, but the figure supplied is 56k. Of course the TSC is so flexible that this can be edited, but I wondered what the basis was for the 56k figure.
Peter |
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jhadhar65
Joined: 29 Sep 2006
Posts: 5
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| Posted: Sun Dec 10, 2006 6:51 am Post subject: |
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| I'm curious about this, too. No answer so far? |
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Geek
Joined: 17 May 2003
Posts: 40
Location: Rosedale, BC, Canada
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| Posted: Tue Dec 12, 2006 9:57 pm Post subject: |
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Hi,
I believe that it's based on a common-cathode rather than common-anode (cathode follower) circuit. Assuming a 12AX or AT7 in there, 56K is about right.
If you want a low (as in 300 ohms or less) source impedance for flexibility, do an ECC88 follower 
_________________
Gregg |
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