Reverb Driver Voltage Supply

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Bombacaototal
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Joined: Thu Oct 06, 2016 5:53 am

Reverb Driver Voltage Supply

Post by Bombacaototal »

I am wondering which of the 2 options (circled in red under the attached) would be best to add a voltage dropping resistor to the Reverb Driver

1) The one on the left, just next to the Screen Grid supply seems to be the approach Two Rock took on the Matt Schofield amp (although I cannot confirm 100%). Although I would assume an extra 20uF would be needed for this
2) The one on the right between the mixer and PI supply is the one Two Rock used on the John Mayer amp (which I can confirm)

My circuit is most similar to the Schofield (Fender blackface).

Blurry gut shot of Schofield amp here http://ampgarage.com/forum/viewtopic.php?f=4&t=30074
Mayer's amp here: http://ampgarage.com/forum/viewtopic.php?f=4&t=29774
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tubeswell
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Location: Wellington. NZ

Re: Reverb Driver Voltage Supply

Post by tubeswell »

What type of reverb driver tube/stage? (12AX7, 12AT7,12AU7, or some type of tetrode or pentode?)
He who dies with the most tubes... wins
Bombacaototal
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Re: Reverb Driver Voltage Supply

Post by Bombacaototal »

tubeswell wrote: Fri Apr 21, 2017 1:27 am What type of reverb driver tube/stage? (12AX7, 12AT7,12AU7, or some type of tetrode or pentode?)
It's a 12AT7 from a Fender Deluxe Reverb like circuit
tubeswell
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Re: Reverb Driver Voltage Supply

Post by tubeswell »

Then any supply around 400-440ish will be okay. So it'll be fine at the screen node - put the driver tube's circuit returns at the same filter cap ground.
He who dies with the most tubes... wins
Bombacaototal
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Re: Reverb Driver Voltage Supply

Post by Bombacaototal »

tubeswell wrote: Fri Apr 21, 2017 9:22 am Then any supply around 400-440ish will be okay. So it'll be fine at the screen node - put the driver tube's circuit returns at the same filter cap ground.
Thanks for the reply
Bombacaototal
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Re: Reverb Driver Voltage Supply

Post by Bombacaototal »

As far as the blackface tremolo (roach) a 22k dropping resistor should be fine?
tubeswell
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Re: Reverb Driver Voltage Supply

Post by tubeswell »

Copy any AB763 circuit
He who dies with the most tubes... wins
Bombacaototal
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Re: Reverb Driver Voltage Supply

Post by Bombacaototal »

tubeswell wrote: Sat Apr 29, 2017 8:31 am Copy any AB763 circuit
Id rather have a power supply for each. That is why :-)
tubeswell
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Location: Wellington. NZ

Re: Reverb Driver Voltage Supply

Post by tubeswell »

a 12AX7 will draw ~2mA, so 22k x 2mA = 44V drop. That should tell you where you will land with the HT voltage for the oscillator. Any HT voltage between about 250 and 440 will be ample for getting the oscillator to work.
He who dies with the most tubes... wins
Bombacaototal
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Joined: Thu Oct 06, 2016 5:53 am

Re: Reverb Driver Voltage Supply

Post by Bombacaototal »

tubeswell wrote: Sat Apr 29, 2017 11:30 pm a 12AX7 will draw ~2mA, so 22k x 2mA = 44V drop. That should tell you where you will land with the HT voltage for the oscillator. Any HT voltage between about 250 and 440 will be ample for getting the oscillator to work.
Great! Thanks a lot
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