Four 6L6s on a Super Reverb Type Circuit?

[Zippy]

I have 1972 Super Reverb (non-master volume, blackfaced) that will blow the walls out of a small club. There is not a huge difference in volume between 45 Watts and 100 Watts, plus with 4 10" speakers, the Super Reverb moves a lot of air.

Speakers will have a lot to do with that as well. The loudest, cleanest Fender I have owned was a Blackface Twin equipped with JBL speakers. Too clean for my taste, but I traded it of to a guy who played Rockabilly and he loved it.

+1 regarding voume as well as effects of speakers. I had a Super Reverb with JBL's...

OP: The first place to start with your Super Reverb is making sure it is putting out all that it is capable of - fresh tubes and a good bias adjustment.

Did I yet say "KT66"?

[renshen1957]

Check out the tweed twin. It's got dual rectifier tubes, and a 4x6L6 output for a clean 100W

It will definitely melt the hair off the back of your head.

More like 85 Watts, then again Fender claimed in late 50's advertising that the Tweed Bassman pushed 60 Watts clean power (which it didn't, but you know banana oil especially when Ampeg had better Bass amps.).

Gibsonman63 is quite correct, the difference between 45 Watts (or 50 watts) and 100 Watts is 3 dB, a little bit louder. To be twice as loud you would need 10 times the power or 450 Watts, Of course your hearing would close down long before to try. At 100 watts I doubt if you could hear any appreciable Sag (think Mesa multiple Rectifier models which are knock offs of Soldano's SLO) for the same reason.

85 Watts "will melt the hair off.." more so with efficient speakers.

(112 dB at 1 watt compared to 95 dB at 1 watt

Best Regards,

Steve

[renshen1957]

Is there any reason I can't run 4 6L6 tubes off a Super Reverb style preamp? I know I would have to change the rectifier and transformer and so on. Is it possible to split the outputs from the phase inverter and run them to 4 tubes instead of 2?

You would either have to change the OT to about 1/2 the primary or have a OT with the same primary and increase the plate voltages significantly. You would need a new power transformer or an auxillary transformer for the increased current required from the 6V3 heater winding. Just adding to more tubes with the same Plate and OT primary would the same watts out (but would sound more powerful or effortless).

Also, if you like a really punchy sound with clean headroom, is it best to go with diodes, or is a rectifier tube still a good idea? I would think tube sag would limit dynamics and add tasty compression, but I don't really know what I'm doing. I don't want to end up with a solid state sound. Maybe I could back up a tube with diodes and have a switch to cut out the tube at will?

At 100 watts you aren't going to hear the sag at full volume. Diodes would the same; other factors such as power supply filters, etc. Switching between tubes and diodes is possible, if interested PM for some reference material on the subject (some of its copyrighted so I refrain from sharing it on the forum). There are ways to use resistance with diodes to model sag, but doesn't sound like what your buddy is looking for.

One other thing: can we get away with 100 watts into a 4x10 with 25-watt speakers? I know 4 times 25 is 100, but I don't know if there are peaks that go beyond the ratings.

General rule of thumb is twice the amps rating, if playing distorted (power amp distortion) the peaks and spikes would require 4 times the power. Amp makers back in the day figured that amps wouldn't be overdriven (designs were based on a clean sound) so they saved money by "cutting corners." Fender's main market was clean (Country and Western) and never did catch on that distortion was part of rock (silver face master volume models pull switch). It's why Marshall ate up alot of Fender's Rock niche which they never to this day caught up with.

Best Regards,

Steve

Best Regards,

Steve

[The New Steve H]

Thanks for the info.

It sounds like the simple thing is to start with a Twin Reverb schematic, but I am really starting to suspect that the sound won't make him happy.

Why is it that rectifiers won't matter at 100 watts? I would have expected them to work the same way they do at lower power, since it would basically be a parallel circuit (two times the same thing).

[Fischerman]

First you said this:

Talking with my buddy, who dreams of a Super Reverb sound (without vibrato), with about 80-100 watts and lots of clean headroom. I got a question.

Then you said this:

I talked to other guitarists today, and they confirmed the claim that the Twin is extremely loud, so while I am in no position to judge, it sounds like a lower-wattage amp might be the way to go.

Which way do want to go, higher power or lower power?

Almost all those BF amps were essentially the same but with different power ratings and power tubes (and sometimes rectifiers). From lower power to higher there were the Princeton Reverb, Deluxe Reverb, Vibrolux Reverb, Bandmaster Reverb, Super Reverb, Vibroverb, Pro Reverb, Twin Reverb, Dual Showman Reverb. The preamp circuits are all almost identical.

AFAIK, one notable difference between the Super Reverb and every one of the others was the .022uF mid cap (most if not all others used a .047uF). More mids (esp lower mids), it's no surprise that the SR is one of the best BF 'overdriven' amps.

[The New Steve H]

My friend is talking about higher power, but it sounds like he may be asking for the wrong thing. I should get him to look for a Super Reverb and a Twin Reverb he can try side by side.

[renshen1957]

Thanks for the info.

It sounds like the simple thing is to start with a Twin Reverb schematic, but I am really starting to suspect that the sound won't make him happy.

Why is it that rectifiers won't matter at 100 watts? I would have expected them to work the same way they do at lower power, since it would basically be a parallel circuit (two times the same thing).

Hi New Steve H,

Tube diode sag only occurs when the amp is at full power and really pushed. One hundred watts is very loud; your ears close down to protect your hearing from the high sound pressure levels. In a very large venue (outdoor) with sufficient distance (nose bleed seats) the SPLs would have decreased enough that sag may become apparent. Then again, the number of musicians that play Twins dimed aren't that many.

Dual and Triple Recto Mesas were originally SLO clones (later models had a few component tweeks in the caps) (Peavey's 5150 also traces its lineage too SLO, and everything of Ule Behringer's Behringier/Bugera are clones). As High Gain Amps these are all played either loud with a master volume (not pushing the power amp) or if played loud, the preamp is the source of the distortion not the power amp stage. The Recto tubes were a marketing ploy, not much more)

Best Regards,

Steve

PS Every Tom, Dick, and Harry is named Steve

[NickC]

I have a 1993 Fender Concert Pro Series. 60watts. It is WAY too loud, even in large clubs playing next to a loud drummer. The problem is the tone of the amp doesn't sound good until cranked up half-way or more .... and club owners (and fellow band-members) simply won't tolerate it. I tried using Yellowjackets, but even then it was still too loud. Thus the amp is useless to me in it's present form.

[The New Steve H]

So it sounds like the tubes DO matter, but you need a thousand-foot cord or a concrete isolation cab in order to be able to appreciate it.

[Zippy]

My friend is talking about higher power, but it sounds like he may be asking for the wrong thing. I should get him to look for a Super Reverb and a Twin Reverb he can try side by side.

... or try sending the output of the Super Reverb to various different cabinets.

You can always pull the SR chassis and put it in a head cabinet or a different combo cab.

[renshen1957]

My friend is talking about higher power, but it sounds like he may be asking for the wrong thing. I should get him to look for a Super Reverb and a Twin Reverb he can try side by side.

Hi Steve,

High power means different things to different people. Some musicians want more headroom to maintain a clean sound at all volume. Others want a very loud sound, not always popular with management or soundmen.

In some amps (Marshalls back in the day) more power produced a different sound quality in the 100 Watt version to the 50 Watt version, (but this was from different NFB resistors, power on the plates, under or over amounts of filter capacitors in the power supply).

You can build an amp that can have the tone of a larger amp (but at the same watts) by an additional parallel set of tubes. This amp would have the 100 watt sound with 4 tubes, disable (or remove) a pair and presto chango the 50 watt sound. Or you coud have an amp that is 4 tubes and loud with a half power switch to remove 2 tubes (Jim Kelley did this in his 60 watt 4 tube 6v6 amps that bear his name).

The Dual Showman (non-reverb) was the Fender Twin (without reverb) in a head and close back cab combination and later joined by the reverb version. Fender had a number of Amps built on the Fender Twin chassis with different configurations of speakers. The Twin is a combo amp with an open back. Something to consider if one speaker arrangement is preferrable to the other.

And which speakers? Jensens, Oxfords, and JBLs to name a few were used by Fender in the Twin Reverb, the JBLs were an upgrade. This makes a difference in the sound. (JBLs speakers and Head and Cab configuration were first used by Standel amps, which Leo copied shamelessly; imitation is rampant in the musical instrument industry. Outside of the industry it is called theft.) Possibly all that is needed is a Super Reverb with different speakers.

The recommendation of your buddy going out and listening to both types of amps is a good one, except many an amp (and car for that matter) was bought during a test drive, although that might solve which type of amp you were going to build for him. It might be better to arrange for him to try out a friend's or friends' amps to prevent impulse GAS. This would give him time to think about what he liked in the amps without the sales clerk hovering over you both ("Well, are you going to buy something, or not?")

A good question is what type(s) of music does he play and perform? Is this amp going to be his workhorse on gigs, or something to enjoy at home? Does he want headroom and clean, or does he want it to break up earlier? Power tube distortion (Jim Kelley), an overdrive sustain (Dumble), or none of these. 2 channel switching preamp? You are starting with a blank aural canvass, make sure he wants a tonal landscape instead of a sonic portrait.

Best Regards,

Steve

[renshen1957]

I have a 1993 Fender Concert Pro Series. 60watts. It is WAY too loud, even in large clubs playing next to a loud drummer. The problem is the tone of the amp doesn't sound good until cranked up half-way or more .... and club owners (and fellow band-members) simply won't tolerate it. I tried using Yellowjackets, but even then it was still too loud. Thus the amp is useless to me in it's present form.

Hi Nick C,

You might want to check out London Power's Power Scaling. Powerscaling.com is a good introduction to the concept. (You might also know this as variable voltage by someone who does not want to acknowledge the lineage).

It does work well, and prolongs tube life unlike using a powerbrake, etc.

Best Regards,

Steve

[The New Steve H]

He plays blues with a lot of delay and so forth. Kind of a spooky, far-off sound.

When talking about performers whose tones he likes, he has mentioned SRV, Robben Ford, and Otis Rush. He's also a fan of Derek Trucks, but I don't recall him talking about his tone.

He plays an American Strat with some kind of new vintage pickups on it.

[Gibsonman63]

He plays blues with a lot of delay and so forth. Kind of a spooky, far-off sound.

When talking about performers whose tones he likes, he has mentioned SRV, Robben Ford, and Otis Rush. He's also a fan of Derek Trucks, but I don't recall him talking about his tone.

He plays an American Strat with some kind of new vintage pickups on it.

Now your getting into Dumble territory. Search Robben Ford on this site and you will see what I mean.

FWIW, all Super Reverbs were not created equal. Check out mid to late eighties Robert Cray and early nineties Ian Moore. Both pro players, both used Super Reverbs and they sound dramatically different, but good. I saw both of them at different times in small clubs and both sounded great. Ian Moore was unbelievably loud though.

[The New Steve H]

My friend knows about Dumble, and he would love to have something like a Steel String Singer. Unfortunately, if there are schematics out there, I am not privy to them.