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6V6s in a Twin Reverb/Dual Showman ????

TheAmpNerd

Member
Messages
1,056
I have a 70s Twin Reverb/Dual Showman amp that is just way too loud...

...so thinking that I'll plop some 6V6s in it.

I'll know I'll need to change the bias
resistor to enable a bias point of about
9 watts per tube.

RCA Receiving Tube Manual, RC-22
has these tubes Max values as shown:

Plate = 350 volts
Screen = 314 volts
PlDiss = 14 watts


So, with this twin having 410 V on the B+
any thoughts to using the following tubes?

BlackPlate RCAs
Mazda NOS
JJ 6V6s

Anyone have an Idea about cathode biasing these? I would use
separate pairs or break them down
as:

1 cap/resistor 4 tubes
2 caps/resistors 2 tubes
4 caps/resistors 1 tube (4x)

This might be an interesting project
for the Guitar Amplifier Magizene.

Thanks.
 
Messages
6,116
Originally posted by TheAmpNerd
I have a 70s Twin Reverb/Dual Showman amp that is just way too loud...

...so thinking that I'll plop some 6V6s in it.

I'll know I'll need to change the bias
resistor to enable a bias point of about
9 watts per tube.

RCA Receiving Tube Manual, RC-22
has these tubes Max values as shown:

Plate = 350 volts
Screen = 314 volts
PlDiss = 14 watts


So, with this twin having 410 V on the B+
any thoughts to using the following tubes?

BlackPlate RCAs
Mazda NOS
JJ 6V6s

Anyone have an Idea about cathode biasing these? I would use
separate pairs or break them down
as:

1 cap/resistor 4 tubes
2 caps/resistors 2 tubes
4 caps/resistors 1 tube (4x)

This might be an interesting project
for the Guitar Amplifier Magizene.

Thanks.






Spike, the output transformer primary
is way too low for 4 6V6 tubes in the twin circuit.
You could try a 4K primary, but I wouldn't cathode
bias it with the stock driver circuit, the OD will
sound terrible when cranked. Doug
 

TheAmpNerd

Member
Messages
1,056
Originally posted by Roccaforte Amps
Spike, the output transformer primary
is way too low for 4 6V6 tubes in the twin circuit.
You could try a 4K primary, but I wouldn't cathode
bias it with the stock driver circuit, the OD will
sound terrible when cranked. Doug
Thanks Doug,

Yeah, that is what I wasn't sure about
as well, how it would sound cranked.

Typically the load resistance of a pair of 6V6s in push pull is about 8.5K and with
two pair we would halve that getting to about 4.2K. So knowing that 6L6s
load resistance is about 4.2K per pair,
or 2.1K for two pair...that twin output tranny would need to go.

It looks like a standard 6L6 pair Tranny would work for this project. I'm wondering now about the driver circuit.

I supposed I could use a driver circuit from an EL84 amp; that would get me in the ball park for the 6V6 quad before I started tweaking it wouldn't it?

Regards,

Spike
 
T

theelectic

You know, with the amount of work & expense you're describing, you're pushing yourself into the "sell my loud amp and buy a smaller amp" territory :) :)

That being said, I have put a pair of THD Yellowjackets in my SF Twin with good results (to my ears, anyway).
 

TheAmpNerd

Member
Messages
1,056
Originally posted by theelectic
You know, with the amount of work & expense you're describing, you're pushing yourself into the "sell my loud amp and buy a smaller amp" territory :) :)

That being said, I have put a pair of THD Yellowjackets in my SF Twin with good results (to my ears, anyway).
OH,

And there ya go upsetting the balance
of the universe with common sense.


Just one pair of EL84s at work there?

Interesting.

The simpler, cheaper, more elegant solution may be at hand.


That said, and I'm a preacher of the
don't make an amp into something it is not, find the right amp to begin with.

Then again, there is that evil tweaking side to me that says...I think I can.

LOL
 
T

theelectic

Originally posted by TheAmpNerd
That said, and I'm a preacher of the
don't make an amp into something it is not, find the right amp to begin with.

Then again, there is that evil tweaking side to me that says...I think I can.

LOL
Ha ha, you're right there. In my Twin I tried various combinations of the Yellowjackets: 2x6L6 with 2xYJ, 2xYJ alone, 2x6L6 alone. I liked the first combo at first (very nice low end and mids) but it was still a hair too loud, so I settled on the 2xYJ alone.

I did not want to do alot of soldering mods since I KNEW eventually I would want that big bold hellacious 100W power, and it would be a PITA (compared to plugging/unplugging) to put it back. Yup, I've got 4x6L6 in there right now :)
 

Jon Silberman

10Q Jerry & Dickey
Silver Supporting Member
Messages
42,554
In the Dec. '04 (yes, it's already out :rolleyes: ) Vintage Guitar mag, on page 112, Gerald Weber provides 5 options for converting a 6L6 Fender amp to 6V6s.
 






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