Increasing power in a tube amp

Aaron Balano · From: San Anselmo, Ca

Does anyone know of an easy way to increase the power in a tube amp (specifically a Fender Deluxe Reverb)? I like the sound and size/weight of the reissues, but the sound breaks up when turned to about 5. I would not mind if it broke up a little at a higher volume. With out the distortion, these amps would sound great with my Stringmaster in smaller clubs. Thanks for any help.

Dan Tyack · From: Olympia, WA USA

I wouldn't even think about doing a mod to this amp, it would kill the resale value, as well as take out the characteristics of the 6V6 output tubes in the amp. You might look for an amp with a pair of 6L6s, which will give you about twice the power. A Super, or a Pro would be good candidates.

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www.tyacktunes.com

Dan Tyack · From: Olympia, WA USA

Another suggestion:

mike the amp. I have been playing some high volume rock and roll gigs with a THD Univalve, which puts out maybe 15 watts (less than your Deluxe). With miking, it makes the stage volume bearable and puts it through the club really well.

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www.tyacktunes.com

Bobby Lee · From: Cloverdale, California, USA

If the amp has a tube rectifier, sometimes switching to a solid state rectifier will give you more apparent power. I've heard of people wiring diodes into a tube socket so that they don't have to modify the amp. I'm not sure if that will work with your amp, though.

Also, beefing up the power supply filter capacitors can help a bit. But like Dan said, modifications to the circuitry will affect the resale value of the amp. People buy the reissues to get that vintage sound. Anything you do to it will change that sound.

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Bobby Lee - email: quasar@b0b.com - gigs - CDs
Sierra Session 12 (E9), Williams 400X (E9, D6), Sierra Olympic 12 (F Diatonic)
Sierra Laptop 8 (D13), Fender Stringmaster (E13, A6)

Jerry Erickson · From: Atlanta,IL 61723

You can modify Deluxe Reverbs to use 6L6 tubes. It's not a real extensive mod and could be reversed should you want to sell the amp. You mentioned reissue, if it is a reissue amp, the mod might not be possible because of the printed circuit board. Check with a good tech in your area.
Jerry

Scott Swartz · From: St. Louis, MO

In the interest of full disclosure it should be noted that 6L6s draw TWICE the filament current of 6V6s (0.9 A vs 0.45 A) and can also draw more plate current, which adds a lot of stress to the power transformer. For these reasons, I would not recommend doing, although it is true that people do it.

For more clean volume, how about a more efficient speaker, maybe a JBL or here's one you may not have heard of, WeberVST. They make reissues of the old Jensen speakers but also make a line called the California series that is great for steel or clean country guitar. I have several of these and they are great, a nice full range clean tone. In fact I have one in my custom built 2 x 6V6 Deluxe style amp.
www.webervst.com

[This message was edited by Scott Swartz on 26 March 2001 at 09:29 PM.]

Corwin Colebrooke · From: Ames, Iowa, USA

I would check the plate voltages in amps and filter cap ratings before using SS rectification. Especially in a Deluxe Reverb. The 6V6EH may be able to handle the increased voltage, but I have a feeling that the life won't be long.

Ricky Davis · From: Bertram, Texas USA

A friend of mine had a Deluxe just like mine(back when I had one); but his would just totally blow mine away. I asked him what he did to it> He said look at the Rectifier tube. He said he had his tech put the biggest baddest best one you can put in it; and they did make a big difference in out put and sound. I'm sorry but it was 3 years ago and forgot what Rectifier tube was in it>but it was twice the size of the one in mine.
Ricky

Bobby Lee · From: Cloverdale, California, USA

If you change from 6V6 to 6L6 output tubes, you will need to replace the transformer too. It's not minor surgery.

Consider a 12" EVM speaker. They are more efficient (louder) than the Fender speakers, and they have a real nice sound for steel. I used to use a Mesa/Boogie Studio 22, Mesa's lowest powered amp at the time, with a 12" EVM. It had enough clean volume for small venues. (Once a rock drummer told me to turn it down - I got a kick out of that!)

My Mesa/Boogie Maverick has a switch in the back that says "Vintage/Bold". It switches between the tube rectifier (vintage) and a diode bridge rectifier (bold). The diodes make the amp sound more powerful. I think it's because they have a faster slew rate, so the attack peaks have more punch.

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Bobby Lee - email: quasar@b0b.com - gigs - CDs
Sierra Session 12 (E9), Williams 400X (E9, D6), Sierra Olympic 12 (F Diatonic)
Sierra Laptop 8 (D13), Fender Stringmaster (E13, A6)

ajm · From: Los Angeles

I would like to address some of the suggestions here. I base this upon what I've read in several books and numerous magazine articles over the years (Vintage Guitar magazine, Gerald Weber's first Kendrick book, and the Groove Tubes book). I personally am not an expert, but once again am basing these comments on the information provided by others. If there are any disagreements maybe we could get Mr. Weber or Mr. Pittman to respond to our needs.

I totally agree with the comment about not modifying this amp. If you want more power get a different amp. If you want it louder, mic it. As Dan said, that way you can give everyone in the audience all the volume they want and not kill your own hearing. Another great suggestion and maybe the easiest thing to do is to is to replace the speaker with a more efficient one. The difference between a stock speaker and an EVM, for example, can be mind blowing. And lastly, don't forget to suggest that everyone else should maybe turn down because they might be the problem, not your amp.

According to Mr. Weber and Mr. Pittman, you can put 6L6 tubes in any Fender amp that uses 6V6s, but you CANNOT do the opposite. Filament current should not be a problem, but you will need to rebias the amp. This is an easy job for any competent tech. I haven't heard anything about needing a different power or output transformer, but as in all cases double check all information with a good amp tech. (By the way, it appears that 6550 tubes are the ones that are a real problem. They seem to draw a ton of filament current.)

Mr. Weber advises NOT switching to a solid state rectifier with 6V6s because of the increased voltages, but that was before the new Electro Harmonix tubes that are advertised for more voltage.

Getting the power supply caps checked is probably worthwhile no matter whatever else you decide to do, especially if the amp is older and has never had it done.

Matt Farrow · From: Raleigh, NC, USA

OK - here's the scoop on Deluxe Reverbs. Fender wanted the loudest, cleanest sound that they could get in these amps, so the tubes are run fixed bias, (stiffer "envelope" of attack and decay) and are run at about 415 VDC on the plates of the tubes. The DESIGN MAXIMUM for a regular 6V6GT is about 350 VDC. Fender knew that the tubes of the day could handle the 20% increase in plate voltage. Modern, Chinese and Russian tubes have not been able to take this kind of voltage, until the 6V6EH. HOWEVER, that plate voltage takes into account the resistance of the tube rectifier in series with the power supply. If you switch to a solid-state rectifier, you'll get about 10 to 15% more voltage out of the amp (depending on the rectifier tube that was in there in the first place.) Add to that the fact that the transformers were spec'd at 110V from the wall, and today's outlets are usually more like 115 or 120V, so you might end up with more than 450V on the plates of your 6V6s!

So what can you do? Well, you'll never get more power out of the amp, no matter what you do. The limiting factors here are the power supply and the output transformer. However, your question seems to be more about increasing headroom, so there are a few things you can do.

1. Substitute lower gain preamp tubes in your amp. You can try 12AT7, 12AY7, 12AU7, 12AZ7 in the first preamp tube slot, or for the phase inverter. This will give the amp less gain, so it won't break up as early.

2. Swap out the power tubes. You can put in 6L6s, but have a competent tech do this for you. You will need to re-bias the amp so that the tubes pull the correct amount of current at idle. You won't have to change the output transformer (necessarily) but you might want to especially if it's a vintage piece. Save the old tranny in case you ever want to sell the amp.

3. Go to a solid-state rectifier. I know I said not to do this, but if you change the power tubes to 6L6s, you might want to swap out the rectifier tube for a plug-in solid-state rectifier. The rectifier tube draws between 2 and 3 amps of current at 5V from your power transformer, and by using the SS device, you will reduce core heating which will also offset the extra current draw of the new power tubes.

If you have any doubts about doing mods to your amp, DON't MOD IT, and take it to a tech in your area with a good rep. If you can't find a good tech nearby then there are a few places that will do repairs by mail, including me. If you have any questions, please email me.

Matt Farrow
Pharaoh Amplifiers

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Matt Farrow
Marlen 9-string 6+2
Kustom K150

http://surf.to/pharaohamps

Bobby Lee · From: Cloverdale, California, USA

I stand corrected on the transformer issue. Sorry to have misled anyone.

Aaron Balano · From: San Anselmo, Ca

Thanks to everyone for the input. Pharaoh is correct in that I don't necissarily want more Power, but more headroom. The amp is loud enough for most small clubs, it just breaks up too soon. A little distortion at loud volumes is ok, just not alot at mid volume. Thanks again for the ideas.
Aaron

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