reverb tube/circuitry Q

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tubenit
Junior tube assistant
Posts: 40
(3/8/04 7:40 pm)
 reverb tube/circuitry Q
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 I am looking at switching a 6CG7 tube out that is driving a piezo-tranducer reverb for a 12AX7 driving a spring reverb tank. The amp is the DanElectro Centurian. 2(12AX7)
preamp, 6CG7 reverb, 6AU6 tremolo,2(6V6) ouput, 6x4 rectifier. Voltages on a Gibson Scout 12AX7 doing both driver/recovery are pretty similar to the Dano 6CG7. Both are twin triode 9 pin sockets. I understand that the resistors and caps will have to be changed accordingly.
On this amp, I don't care about preserving the vintage goofy reverb.

I looked at numerous schematics and as near as I can understand it looks like one tube can serve as reverb driver and recovery. (left out caps/resistors below in illustration)

DRIVER:
- grid to plate of 1st preamp
tube
- cathode to ground
- plate to "powerline" (+)
RECOVERY:
-grid to reverb tank & ground
-cathode to ground
-plate to "powerline" (+)

Am I understandng this correctly that one tube can serve for both Driver/Recovery and the driver side ties into te plate of the 1st preamp tube? And that tying it between te 1st & 2nd preamp tubes allows the 2nd preamp tube to amplify the reverb recovery? tubenit
 
Dmichel1984
Junior tube assistant
Posts: 1
(3/9/04 4:55 am)
 me too
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 I want to do this on my Silvertone Twin Twelve,
I believe the only changes would be to ground pin 9, right????? :




 
tubenit
Junior tube assistant
Posts: 41
(3/9/04 7:06 am)
 Re: me too
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 The Gibson Scout GA-17RVT I rebuilt does NOT have pin 9 grounded (no caps, resistors on it either). (see schematic heaven.com for schematic)
Hope that helps. I would be curious to know if your twin-12 has a piezo transducer reverb??
 
Dmichel1984
Junior tube assistant
Posts: 8
(3/9/04 6:00 pm)
 re
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 I'm not sure what piezo transducer reverb is, but I think this is a spring tank, although very small. I need more 'verb, and a 12AX7 is a higher gain, higher heater voltage twin triode than the 6CG7, with the same pinout except the 6CG7 has nothing on pin 9... you can ground pin 9 and be able to use both...


the 6EU7 is similar to a 12AX7 with different pinout, but 6V heater, so thats diff. from a 6CG7...
 
Dmichel1984
Junior tube assistant
Posts: 9
(3/9/04 6:13 pm)
 btw
--------------------------------------------------------------------------------
 by the way, the silvertone does not have a transformer for the reverb
 
tubenit
Junior tube assistant
Posts: 42
(3/9/04 9:32 pm)
 Re: btw
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 The Scout GA-17RVT actually has a 12AX7 for the reverb. The schematic lists a 6EU7 and the tub layout lists the 12AX7 contradicting the schematic.
The layout with 12AX7 is correct for the reverb. I rebuilt a Scout and the reverb is great on it!

I'm curious about no reverb trans and the small reverb?
The piezotransducer reverb looks like a cigar holder only slightly larger. Is that what you have or is yours actually a reverb tank that is small?
 
Dmichel1984
Junior tube assistant
Posts: 11
(3/10/04 1:47 pm)
 verb
--------------------------------------------------------------------------------
 I'm curious about no reverb trans and the small reverb?
The piezotransducer reverb looks like a cigar holder only slightly larger. Is that what you have or is yours actually a reverb tank that is small?


This may be what I have (silvertone/danelectro are the same) It does have a spring in there i think, but yeah about that size.......
 
Dmichel1984
Junior tube assistant
Posts: 12
(3/10/04 1:53 pm)
 btw
--------------------------------------------------------------------------------
 I rewired the heater on the 6CG7 driving the verb to accept a 12AX7(12AT7 or 12AU7, etc) not by grounding pin 9, but by moving pin 4 to pin 9 and bridging 4&5, It sure has alot more spring to it now....
 
tubenit
Junior tube assistant
Posts: 43
(3/10/04 6:51 pm)
 Re: btw
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 Interesting! Thanks for the response. The Gibson scout had the 4&5 pin bridged and the 9 pin open like you have done. Glad to hear it has more spring to it. I'm still leaning towards using a spring reverb and adding a reverb trans if needed.The Dano amp will be sent to me by my son-in-law.
 
Dmichel1984
Junior tube assistant
Posts: 14
(3/11/04 6:51 am)
 CALLING: WESTBURIAN
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 Yeah, I think I'd still rather convert it to tranny driven w/ Accutronics tank...

Westburian should be able to help us.....
 
 
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