Deluxe Reverb - Adding extra Tubes

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Bombacaototal
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Deluxe Reverb - Adding extra Tubes

Post by Bombacaototal »

Hi all, I am considering adding a PI cathode follower to my Deluxe Reverb.

I am wondering if anyone has done something similar, what would be the drawbacks and positives of adding it?

What worries me as well is finding the physical space to adding an extra set of tubes. Has anyone ever done a 14-tube Deluxe even if the extra tubes had a different purpose?
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TUBEDUDE
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Re: Deluxe Reverb - Adding extra Tubes

Post by TUBEDUDE »

14 tubes or 14 stages?
Tube junkie that aspires to become a tri-state bidirectional buss driver.
Firestorm
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Re: Deluxe Reverb - Adding extra Tubes

Post by Firestorm »

Forgive my ignorance: what's a PI cathode follower?
Bombacaototal
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Re: Deluxe Reverb - Adding extra Tubes

Post by Bombacaototal »

Firestorm wrote:Forgive my ignorance: what's a PI cathode follower?
It is basically adding 2 valves (12ax7) between the phase inverter tubes (v6) and the power tubes, like some bass amps (amped svt) and the dumble sss
Synchu
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Re: Deluxe Reverb - Adding extra Tubes

Post by Synchu »

You are adding 1 triode (half tube) after each PI stage. It is one tube being added in total.
What's the aim?

Niki
Bombacaototal
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Re: Deluxe Reverb - Adding extra Tubes

Post by Bombacaototal »

Synchu wrote:You are adding 1 triode (half tube) after each PI stage. It is one tube being added in total.
What's the aim?

Niki
Yes, that is what I had in mind. Apparently it can increase the headroom
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jelle
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Re: Deluxe Reverb - Adding extra Tubes

Post by jelle »

Bombacaototal
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Re: Deluxe Reverb - Adding extra Tubes

Post by Bombacaototal »

Thanks a lot for the tip Jelle. Have you ever tried the MOSFET? How does it compare to the tube as far as sound? The article seems very positive regarding its sound. I also read that MOSFETs can be placed in push pull mode, just like PNP and NPN transistors
Last edited by Bombacaototal on Wed Oct 26, 2016 2:24 pm, edited 1 time in total.
Teleguy61
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Re: Deluxe Reverb - Adding extra Tubes

Post by Teleguy61 »

Personally I would try less invasive mods first, like working on the PI a bit.
Check out the PI on a 6G6B, different values, higher voltage, and lower voltage on the preamp.
Also, you're talking a DR, not really a headroom monster to begin with.
Bombacaototal
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Re: Deluxe Reverb - Adding extra Tubes

Post by Bombacaototal »

Hi Jelle, I am wondering if you ever tried or even if it is possible to have an amp that has a ON/bypass switch for the MOSFET. When the switch is OFF the MOSFET would be bypassed and the amp would be stock. When the switch is ON the amp would have the PI cathode follower
Firestorm
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Re: Deluxe Reverb - Adding extra Tubes

Post by Firestorm »

A simple way to tweak the headroom of a DR is to reduce the value of the 220K grid return/bias feed resistors on the output tubes. Subtle but noticeable.

As I understand it, putting cathode followers between the PI and the output tubes can prevent overtaxing the PI when heavy drive signals are required. This would hardly be the case with a pair of 6V6s. It would annoy me to shoehorn an extra stage in a tight build and discover little effect. :evil:
Bombacaototal
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Re: Deluxe Reverb - Adding extra Tubes

Post by Bombacaototal »

Firestorm wrote:A simple way to tweak the headroom of a DR is to reduce the value of the 220K grid return/bias feed resistors on the output tubes. Subtle but noticeable.

As I understand it, putting cathode followers between the PI and the output tubes can prevent overtaxing the PI when heavy drive signals are required. This would hardly be the case with a pair of 6V6s. It would annoy me to shoehorn an extra stage in a tight build and discover little effect. :evil:
Thanks for the feedback. My DR actually is being changed to a pair of 6L6s and a fender 40w OT with the stock PT ;-)
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ToneMerc
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Re: Deluxe Reverb - Adding extra Tubes

Post by ToneMerc »

Bombacaototal wrote: Thanks for the feedback. My DR actually is being changed to a pair of 6L6s and a fender 40w OT with the stock PT ;-)
Personally, I would not attempt this with the stock PT transformer with the end goal obtaining more headroom. I would use a PT with an HT current rating somewhat conducive to to the larger glass.

Kind of akin to putting a turbo on a 4 cylinder engine with 20lbs of boost and expecting it to make lots of horsepower with only 7psi of fuel pressure.

TM
Bombacaototal
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Re: Deluxe Reverb - Adding extra Tubes

Post by Bombacaototal »

ToneMerc wrote:
Bombacaototal wrote: Thanks for the feedback. My DR actually is being changed to a pair of 6L6s and a fender 40w OT with the stock PT ;-)
Personally, I would not attempt this with the stock PT transformer with the end goal obtaining more headroom. I would use a PT with an HT current rating somewhat conducive to to the larger glass.

Kind of akin to putting a turbo on a 4 cylinder engine with 20lbs of boost and expecting it to make lots of horsepower with only 7psi of fuel pressure.

TM
Thanks for the advice. The only reason I am not changing the PT is due to physical space. I am unable to fit a 40watt in my DR head. Do you have any recommendation of a PT with an HT current rating somewhat conducive to the larger glass.
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ToneMerc
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Re: Deluxe Reverb - Adding extra Tubes

Post by ToneMerc »

Bombacaototal wrote:
ToneMerc wrote:
Bombacaototal wrote: Thanks for the feedback. My DR actually is being changed to a pair of 6L6s and a fender 40w OT with the stock PT ;-)
Personally, I would not attempt this with the stock PT transformer with the end goal obtaining more headroom. I would use a PT with an HT current rating somewhat conducive to to the larger glass.

Kind of akin to putting a turbo on a 4 cylinder engine with 20lbs of boost and expecting it to make lots of horsepower with only 7psi of fuel pressure.

TM
Thanks for the advice. The only reason I am not changing the PT is due to physical space. I am unable to fit a 40watt in my DR head. Do you have any recommendation of a PT with
an HT current rating somewhat conducive to the larger glass.
http://www.allenamps.com/parts.php#transformers


TM
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