ohms

[Robert Strusz]

Hi I have a 74 Super Reverb. It is too loud. At 2 ohms I can't seem to
find an attenuator. I had a THD and didn't like the sound. I like to
play between 3 and 5. Can I change the OHMS to 4, 8, or 16 ? Replace
tubes. Love the sound of this amp. Is there anything I can do the
won't destroy it ? Thanks, Bob

[kevin thomson]

Bob, You have a 40 watt amp with 4 speakers. I don't want to be insulting but that amp was designed to do what it does and do it well. Instead of attenuators, hot plates and gimmicks, why not buy a Vibrolux, Deluxe or Princeton....that is in descending volume order from the super...very similar sound.

Changing the ohms won't do it. Rebiasing, and cutting the plate voltage to accept 6v6's instead of 6l6's might do it but why go to such lengths when fender designed other amps to do precisely what you are looking for? Even if a Deluxe or Prinny is not quite loud enough, you can put an extension cab underneath and grab volume that way....and then leave the cab out for rehearsals or home use.

I am telling you this as a person who used a Super for years in conjunction with a Hiwatt Custom 100. The super did not have too much trouble keeping up with the Hiwatt. LOUD!

don't get discouraged and best of luck in your search for your perfect tone....kt

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[Robert Strusz]

Hi Kevin I have a Deluxe and use it all the time with a Dr.Z
Brake-lite, it works great.I put the Z on the 1st or 2nd notch. I'm a
60 year old blues player know what I like . They all sound different .
I go for a pretty clean sound. Outside the Super works great. Mine
kicks in wonderfully at 3. If I could somehow get it to work in my
small club gigs I would be happy. The Super I had in ' 72 was louder
than this one. tone wasn't as good either. This amp sounds too good I
hope there is a way. Thanks for your help. Bob

[frank]

this is supposedly the best attenuator avail. (2 ohm opt.) good enough for sonny landreth:

 

http://www.ultimateattenuator.com/index.html

 

expensive, though.

[KT]

Oh heck... Sounds like you've found the right tone at the wrong volume.

Pass the earplugs!

KT

[B L]

Bob,

I think Kevin makes a good point about going smaller. However, if you can't see your way clear to get a Deluxe, Princeton, etc., you might try a couple other things. Some of these will sound counterintuitive so bear with me.

1. deliberately replace your original speakers with something less efficient. That can be tricky but it is not impossible. Your tone may change some, but you might even like what you hear. You should be able to lose 3-5 db of efficiency without too much trouble, effectively reducing the loudness of your amp. 5db doesn't sound like much on paper...but if you understand how the (deci)Bel scale works, you already get the idea. Half a Bel is a big change! Could be some big tone changes though, plus potential weight gain, and of course expense. :-/ Fortunately, cheap inefficient 10" speakers are abundant...but AVOID the big ceramic magnets, they'll kill your back! :-)

2. Speaking of killing, kill the b+ drive to your grids, thereby reducing your output power by 4 watts. Makes a small but audible difference.

3. Find and install some coke bottle 6L6 (not 6L6GC or 6L6WGB) tubes. At equal voltages, 6L6 produce only 80% of the power of the 6L6GC. You'll hear this as well, and it is easy. Your amp is supposed to have 437 volts on the plates, which is just barely outside the rated max voltage for a 6L6 plate...I wouldn't sweat it too much...but test it out before you just swap them and go play a gig. Many 6L6 are now quite elderly and may not be up to the task, though I've done this for years in several of my regularly gigged amps and only lost 1 tube. It was a late 30's (!) 6L6.

4. Convert your amp from fixed bias to self (cathode) bias. Not too hard either, and that will reduce your output power from a (theoretical) 40 watts to 26ish watts, if using a 190 ohm cathode bias resistor, (presuming you actually have 437 volts on the plates of your tubes.) This is going to be a real game changer for tone and volume.

5. Your amp is a 1974. I believe Utralinear output transfomers were generally added by Fender in 1975...but check anyway. Examine the output transformer to verify that it is not an ultralinear design.  LATE 74 manufacturing seems right on the cutoff for the beginning of ultralinear OPT in Fenders, though I am not finding any Fender schematics which indicate that UL's were put in Supers. I've heard it both ways. Anyway, the definitive way to know is to count  the total number of leads in and out of your output transformer. If it has five, it is not ultralinear. If it has seven or more it is. No need to replace it if UL...just remove the 40% screen grid taps, which should connect to pin 4 on each of your output tubes. connect them via a 470 ohm 1 watt resistor to the ouput of your filter choke and you are good to go, or simply tape them off if you want #2 above. This is a "must do" if you want to get the blackface tone...but I really doubt your amp has a UL...but you never know.

For my money, I would swap to 6L6CG for regular 6L6 tubes and convert it to fixed bias. That ought to put you in a position to crank her up to 8 without killing yourself. :-) It is an easy mod, and in non-destructive to the amps collector value if properly done, since you can easily revert it back to the original spec without any hole drilling, transformer swapping, etc. Naturally I would dump the ultralinear taps as well, but again I doubt you are going to find that your 74 amp is so equipped.

Of course, you could do what Kevin says and get a Princeton. That's a viable solution, though some who move away from the 4x10 wall of sound to a single 10 not always happy with that. I have both setups and I find myself missing the 4x10's when I use a single Princeton.

Cheers,

CBG

[mdmar...@bellsouth.net]

Or, install a half power switch in place of the unnecessary ground switch. A basic pentode triode switch with 1K 5watt screen resistors. Use a DPDT to move the screen resistors from the screen supply to the power tube plates.
Mike

Sent from my Verizon Wireless BlackBerry

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From: B L <coolbl...@gmail.com>

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Date: Fri, 3 Dec 2010 08:41:18 -0600

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Subject: Re: [The Amp Guide] ohms

[frank]

did you try yellow jackets from thd?

-----Original Message-----
From: B L <coolbl...@gmail.com>
To: the-amp-guide <the-am...@googlegroups.com>
Sent: Fri, Dec 3, 2010 9:41 am
Subject: Re: [The Amp Guide] ohms