Reverb mod=phase cancellation?

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Searing
Junior tube assistant
Posts: 66
(1/16/04 12:24 pm)
 Reverb mod=phase cancellation?
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 In my blackface twin with Dougs AB763 board in it I ran a wire from the hot jack of the reverb to pin 2 on tube 1. I now can control the reverb tone with channel 1's tone controls. Gerald Weber has this mod in his second book. Even though it did not do exactly what it said it was going to do in his book, it sounds pretty cool. Then I was reading more and realized that channel 1 and channel 2 are not in phase. So by connecting the reverb to channel 1 am I causing phase cancellation? It doesn't sound like it? Let me know what you think! Thanks!
Chris
 
GroundhogKen
Forum Moderator
Posts: 2226
(1/16/04 12:36 pm)
 Re: Reverb mod=phase cancellation?
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 The dry guitar signal and the signal returning from the reverb springs are completely different, so I don't think it makes a bit of difference if the reverb goes though an odd number of inverting stages compared to the dry signal.


Ken
 
Searing
Junior tube assistant
Posts: 67
(1/22/04 11:41 am)
 Re: Reverb mod=phase cancellation?
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 Thanks Ken!
Can anyone tell me why when I turn up the pots on channel one the reverb effect goes down, or get's drown out by channel one. I thought channel one should only be controlling the reverb tone not the signal tone? Thanks!
Chris
 
GroundhogKen
Forum Moderator
Posts: 2229
(1/22/04 12:38 pm)
 Re: Reverb mod=phase cancellation?
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 Did you disconnect the wire that carries the reverb signal back into the standard mixing stage? If you didn't, then you would be mixing the regular reverb with the channel 1 reverb and those signals may well have opposite polarity.


Ken


EDIT: I guess you could accomplish the same result by keeping the regular reverb knob all the way to '0'.

Edited by: GroundhogKen at: 1/22/04 12:42 pm
 
Searing
Junior tube assistant
Posts: 67
(1/23/04 10:34 am)
 Re: Reverb mod=phase cancellation?
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 Ken,
I followed Gerald Webers words in his second book on doing this mod exactly, I think. The only thing I disconnected was the input wire on pin 2 on preamp 1. To this pin 2 I connected a wire from the hot (output jack of the reverb) The master volume on channel one does not increase reverb rather volume that actually defeats the reverb. I am a little confused here. Is there a way to make channel 1's volume knob the reverb mix control. That is what the mod was supposed to do, but it did not work out that way. I like the way the amp sounds now though as I seem to be able to blend the two channels tones together. Any thoughts?
Chris
 
Searing
Junior tube assistant
Posts: 69
(2/3/04 1:02 pm)
 Re: Reverb mod=phase cancellation?
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 Ouch!
I just realized that I connected pin2 on v1 to the reverb input (the one with the tranformer attached to it) rather than the output. It was working like this, but only to blend the two channels, having no real effect on the reverb itself. At our last show my amp lost volume and distorted and would keep doing this, especially with certain notes and when I played aggresively (most of the time) I opened it up and discovered the wiring mistake I made. I corrected it and replaced tubes 1 and 2. It seems to be working fine now, but I have not gigged with it yet. Could I have damaged something? Also, with this reverb mod set up, should I leave pin 2 on v4 hooked up to the reverb output? Thanks!
Chris
 
GroundhogKen
Forum Moderator
Posts: 2238
(2/3/04 1:15 pm)
 Re: Reverb mod=phase cancellation?
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 I don't think that mistake would damage anything.

Ken

 
 
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