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Topic: Increasing power on a Fender Super Reverb |
Dave Zirbel
From:
Sebastopol, CA USA
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Posted 24 May 2004 7:58 pm |
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What is the most power you can get out of a Fender amp that takes two 6L6's? Is this a simple mod that involves swapping the transformer? I would like to get 50 to 60 watts out of it.
Thanks, Dave |
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Ken Fox
From:
Nashville GA USA
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Posted 24 May 2004 8:41 pm
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| The most clean power a 6L6GC can put out is 30 watts each. To get that you have to increase plate voltage to get the voltage swing needed. Itwas done in the later model Super Reverbs with ultra-linear output transformers and higher plate voltages. I have had that type of Super Reverb as well as three I own now (1964,1967, and a 1971). I could not really hear that much if any difference in 40 to 60 watts. An easier way to get more out is with more effient speakers! You can put JBLs, 10" Scorpions, Eminence Delta Lites or even Weber Californias and get a lot more volume than with stock Eminence, CTS or Jensen speakers. For weight, I would look at the Delta Lites. My 1971 has been blackfaced and has two Weber Caliofornias and two CTS alnicos in it. It is by far louder and clearer than my other two amps. Yet those amps sound the same when plugged into that cabinet! |
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John Daugherty
From:
Rolla, Missouri, USA
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Posted 25 May 2004 4:33 am
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Dave, a trick I used on the old tube amps was to increase the value of the cathode bypass capacitor.
I do not have a schematic of your amp so I can offer this advice: look at the wired side of the tube socket(6L6). Pin 8 is the cathode. If there is an electrolytic cap from pin 8 to chassis, I am guessing that it is about 10-20 mfd. Replace it with a 100-200 mfd @ 25 volts or higher.
There may be a cap on each socket but it is most likely one capacitor and all pin 8s are tied together.
If I can locate a schematic, I can be more specific. Good luck and God bless. |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 25 May 2004 5:27 am
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To quote Mike Brown from another thread:
quote:
+3dB=2 x power=Noticable difference
+6dB=4 x power=Moderate difference
+10dB=10 x power=Twice the difference in loudness.
A Pro reverb also has two 6L6s. The ones from the '60s get 40 watts. The '70s silver face with the ultralinear transformer gets 70 watts. That's almost twice the power and is noticeably louder. Its like having the volume knob go to 11 or 12. Ken's right that you can get more bang from more efficient speakers. Of course you could do both, and that would make an even bigger difference. |
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Dave Zirbel
From:
Sebastopol, CA USA
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Posted 25 May 2004 6:22 am
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Thanks for the input guys. I already use JBLs. I feel like I don't need a lot more power, just a little so this may be something I need to do. It's not a Super Reverb combo with the speakers, it was comverted to a head with the option of 4 or 8 ohms. I have 2-12" JBLs and 2 15" JBLs so I have options.
DZ |
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David Doggett
From:
Bawl'mer, MD (formerly of MS, Nawluns, Gnashville, Knocksville, Lost Angeles, Bahsten. and Philly)
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Posted 25 May 2004 6:56 am
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| Just out of curiosity, how do you convert a 2 ohm Super Reverb to one that is 4 or 8 ohm. Does it produce the same power as the 2 ohm? |
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Dave Zirbel
From:
Sebastopol, CA USA
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Posted 25 May 2004 9:03 am
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The transformer in the amp is made by Mojo. It has 3 wires coming of it. 1)2 ohm, 2)4 ohm, 3) 8 ohms. My amp tech, Sal Trentino, wired the speaker jack as 4 ohms and the ext. speaker jack as 8 ohms. The only prblem is that if the amp is on and there are no speakers hooked up, it could damage the amp. I know nothing about electronics so I'm taking Sals word that this can be done. The amp works great. I did see the transformer with the 3 wires.
BTW - if you haven't heard of Sal Trentino, he one of the best in the bay area. He's been Niel Youngs tech for many years and has built amps for bands such as Pearl Jam. Unfortunatly he is closing shop. He just found out he has cancer. 
DZ[This message was edited by Dave Zirbel on 25 May 2004 at 10:55 AM.] |
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Dan Tyack
From:
Olympia, WA USA
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Posted 25 May 2004 2:23 pm
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| You could possible use 6550s or Kt88s and rebias the amp, if the transformer can handle it. These are capable of more wattage, and more to the point, they stay cleaner longer than a 6l6 (they only start distorting towards their rated power output). |
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Ken Fox
From:
Nashville GA USA
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Posted 25 May 2004 7:04 pm
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| Well, if you have a 5AR4/GZ34 rectifier you can get a bit of help by putting in a Webber Copper Cap. I use one in my 1966 Deluxe. If your amp has a 5U4GB it can gain about 20 volts of plate voltage by changing that to a Copper Cap equivalent of the GZ34. You will have to rebias for sure. That also removes the filament current load of that tube, increasing available power supply capability. Your sound will tighten up a lot when switching from a 5U4GB. It's internal resistance causes about a 20 volt or so drop in plate voltage and also adds "sag" the front edge of a note. |
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Dave Zirbel
From:
Sebastopol, CA USA
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Posted 25 May 2004 7:30 pm
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What is a Copper Cap?
DZ |
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Ken Fox
From:
Nashville GA USA
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Posted 26 May 2004 10:28 am
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A plug in solid state recitifier, made by Weber. About $14.00 and very popular with Fender players over on the fender Forum. Looks like a copper tube!
webervst.com |
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