Question for Jim Sliff or another Fender amp guru

Jeremy Steele · From: Princeton, NJ USA

Can a Super Twin Reverb be safely operated with less than a full compliment of 6 power tubes? 4? or even 2? Would any modifications be needed?
Please advise.

Donny Hinson · From: Glen Burnie, Md. U.S.A.

Theoretically , you could, since the tubes are just push/pull trios (paralleled). As long as you played smooth and clean, it would work (despite some internal impedance mismatching). If the amp was pushed, though, (like trying to get distortion through overloading the final), I'd predict a rapid death for the remaining 6L6's. This amp is already running 'way over design parameters for the 6L6 tubes. You could modify the power supply for less voltage, and then re-bias it, but then you're carrying around 95 pounds of amp when 50 pounds (in a smaller amp) would work better.

I just don't see the benefit in doing all that. If you want a lower output amp to "push" to get distortion, why not buy one?

Jim Sliff · From: Lawndale California, USA

What Donny said - it's not a good design for pulling power tubes. The iron is much too heavy (i.e. the transformers) and you will not gain much warmth and only a miniscule drop in volume. You'll lose some headroom, but the result with these amps (peculiar in the Fender line) is the resulting sound will be harsh, not warm and smooth lie pulling two tubes from a Twin.

If you need to pull any tubes from one of these monsters, you have "too much amp" Sell it, get a decent used 85-watt Twin and a Deluxe Reverb. Or just get a silverface Pro Reverb if you want ONE amp, learn how to bias it, load it with good speakers and you'll be pleasantly surprised.

To directly answer the question, though - yes you can do it, yes you need modifications (at minimum a knowledge of bias settings and installation of an external nias pot and purchase of a Weber Bias Rite, Allesandro Bias and Matching Meter, etc, or similar...and if you had to ask the question I would NOT suggest attempting it! Plus, to repeat - you're not going o get a huge difference due to the transformers.
_________________
No chops, but great tone
1930's/40's Rickenbacher/Rickenbacker 6&8 string lap steels
1921 Weissenborn Style 2; Hilo&Schireson hollownecks
Appalachian, Regal & Dobro squarenecks
1959 Fender 400 9+2 B6;1960's Fender 800 3+3+2; 1948 Fender Dual-8 Professional

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

I agree with Donny and Jim. The point of having such a powerful amp is - well, to have a real powerful amp. There are people out there who love these for steel. Why carry around all that weight if you don't want the juice? A Twin or Pro Reverb makes much more sense to me too.

People do sometimes remove one push-pull pair from Twin Reverbs. To match impedance, one generally uses just one of the speakers to give a nominal matching load of 8 ohms (4/2 or double the normal impedance of 4 ohms). I bought one like that a while back reasonable - I expect they did it because that other speaker sounds bad. It's still real loud even run on half-power, but I'm gonna go ahead and replace the funky speaker and then set it up for the full 135 watts. It sounds real good for steel and jazz guitar, even as it sits now. But I want full juice if I'm gonna carry that beast around.

Note that this impedance matching trick doesn't work so easily when pulling tubes from a Super Twin. If the nominal load is 4 ohms (2-8 ohm speakers in parallel), then if you use 4 tubes, you'd need a 6-ohm load (6/4 or 1.5 times the normal impedance), or for 2 tubes, a 12-ohm load (6/2 or 3 times the normal impedance). I'd skip it.

Jeremy Steele · From: Princeton, NJ USA

Thanks for the info guys...I had a chance to buy one relatively cheap but took a pass...I think it's just much more amp than I need...I have been playing through a buddy's Deluxe and I LOVE the tone, but would like a bit more in the way of cojones...I will most likely wind up with a Twin or Showman head.

Craig A Davidson · From: Wisconsin Rapids, Wisconsin USA

Ok on the Twin it is tubes 1 and 4 or else 2 and 3 that you can pull safely right?

Forum Index > Electronics		Next oldest topic :: Next newest topic

All times are GMT - 8 Hours	Jump to: