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Discussion Starter #1
anyone have this done? I'm wondering how much it costs to be done.

edit: I'm thinking of having a super reverb blackfaced but it already sounds great
 

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sesroh said:
anyone have this done? I'm wondering how much it costs to be done.

edit: I'm thinking of having a super reverb blackfaced but it already sounds great
It depends on the year. The early silver faces are still the black face circuit. They changed more and more as the years went on.

That said, if it sounds good. Leave it.
 

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Definitely worth determining the year of manufacture. If it's a very late one with 70 watt power and ultra linear output transformer it will not have the same character as an early one even if you do blackface the circuit.
 

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Discussion Starter #4
all i know is that the amp does have a master volume and pull boost control. I have no idea what year. Im assuming mid seventies
 

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sesroh said:
all i know is that the amp does have a master volume and pull boost control. I have no idea what year. Im assuming mid seventies
Mid to late probably. You'll need to find out the exact year before someone can get a little more exact on a price. Write down the numbers on the transformers, they'll date the amp for you.
 

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Discussion Starter #7





it is the later 70 watt version. i doubt i want it blackfaced. i already like the sound of it.
 

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"It's the exact same thing, only different..."

sesroh said:
it is the later 70 watt version. i doubt i want it blackfaced. i already like the sound of it.
If you like the sound of it then that's the most important thing!:food-smiley-004:

That being said, I think your model is the one with 4 6L6 output tubes and a master volume. The preamp is pretty close to blackface already. The major difference is in some of the parts values around the phase inverter 12AX7, the last tube in the chain which then drives the big output ones.

I would think an hour's time and $5 of resistors would do it. Since blackface amps never had master volumes the circuit would not be totally blackface but this would pretty well bring the tone around to BF style.

In my shop we'd be talking less than $75, barring any surprises.

If you're truly happy with the tone I advise you NOT to listen to a BF version! It's like not caring about ice cream if you've never tasted it...

Ignorance is bliss! :tongue:
 

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Discussion Starter #9
yeah i dont think i will have it blackfaced. It does only have 2 6L6 tubes though. they're also original which is strange. i have a feeling it was made in 1980.
 

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Discussion Starter #10 (Edited)
i just found out that the extension speaker input is disconnected or something which is a little annoying because even if it's not neccesary, i like to be able to use a cab if i choose to. might have that looked at. same with the pull boost(which is some what good that it's disconnected). im pretty sure a few other things have been done to the amp too.
 

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sesroh said:
i just found out that the extension speaker input is disconnected or something which is a little annoying because even if it's not neccesary, i like to be able to use a cab if i choose to. might have that looked at. same with the pull boost(which is some what good that it's disconnected). im pretty sure a few other things have been done to the amp too.
Fender jacks are a bit tricky, in case you hadn't run across this before. The ext jack is wired as a shorting jack to put the extension in series with the main jack.

This means that you must plug a speaker into the main jack first. Any extras go into the extension jack. This runs both speaker loads.

If you want to run ONLY the extension cab you plug it into the MAIN speaker jack! If you plug it into the extension jack with nothing plugged into the main jack then you hear zilch.

Hopefully this is the case instead of someone hacking the connections inside.
 

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Discussion Starter #12
yeah.. it actually doesn't work either way. i have tried using both inputs at the same time. my cab will only run on the main output.
 

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2 ohm Super Reverbs and extension cabinets

Careful here, Sesroh. The Super Reverb is the poster child for ext. cabinet impedance mismatches because of its 2 ohm output transformer (2 ohm parallel with 4 or 8 ohm ext. cabinet makes the amp "see" less than 2 ohms, thus approaching an open short).

From Gerald Weber, "A Desktop Reference of Hip Vintage Guitar Amps," page 212:

"....I would never use the 'ext. speaker' jack on a Super Reverb without rewiring the stock 2 ohm load (four 8 ohm speakers in parallel equals 2 ohms) to an 8 ohm load (series parallel or parallel series)."

And from page 210:

"....Series parallel.... more branch inductance and therefore will have less high end, better low end, and an overall crunchier tone.... wire two speakers is series and the other two speakers in series... Next wire one set in parallel with the other set... Impedance is 8 ohms."

"....Parallel series.... less branch inductance and therefore will have better clarity in the high end, a little less low end and an overall cleaner tone.... wire two speakers in parallel and the other two speakers in parallel.... Next wire one set in series with the other set.... Impedance is 8 ohms."

Every late 70's SF 6L6 Fender amp I have heard already had enough high end clarity.....

Peter
 

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Discussion Starter #14
ahh interesting stuff. I think I'll leave it be then. everything else seems to function. but now I'm going to have to find a head to use with my cabinet :DevilGuitar:
 

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peter benn said:
Careful here, Sesroh. The Super Reverb is the poster child for ext. cabinet impedance mismatches because of its 2 ohm output transformer (2 ohm parallel with 4 or 8 ohm ext. cabinet makes the amp "see" less than 2 ohms, thus approaching an open short).

From Gerald Weber, "A Desktop Reference of Hip Vintage Guitar Amps," page 212:

"....I would never use the 'ext. speaker' jack on a Super Reverb without rewiring the stock 2 ohm load (four 8 ohm speakers in parallel equals 2 ohms) to an 8 ohm load (series parallel or parallel series)."

And from page 210:

"....Series parallel.... more branch inductance and therefore will have less high end, better low end, and an overall crunchier tone.... wire two speakers is series and the other two speakers in series... Next wire one set in parallel with the other set... Impedance is 8 ohms."

"....Parallel series.... less branch inductance and therefore will have better clarity in the high end, a little less low end and an overall cleaner tone.... wire two speakers in parallel and the other two speakers in parallel.... Next wire one set in series with the other set.... Impedance is 8 ohms."

Peter
Haven't had my coffee yet so I'm probably missing something but are you talking about running an OT designed to deliver to a 2 ohm load into a speaker cab running 8 ohms?

Wouldn't this raise the primary load to the 6L6's by a similar factor of 4, that is the usual 6600 ohm load to the plates would become 26400 ohms!

To me this would be similar to running the OT into an open load, allowing sky high voltage peaks and possible arcing between windings.

As for Mr. Weber's thoughts on differences between series and parallel combinations, although the difference in inductance is obvious did he give any actual numbers? The reason I ask is that we're talking audio frequencies here. I would think that the inductance value would be so small as to present a trivial amount of inductive reactance.

In other words, this appears to be an idea taken from theory without necessarily being appropriate when the actual values are trivial. If I were wiring coils for a radio frequency device the amount of inductance involved would present a high enough inductive reactance to noticeably change the characteristics of the circuit.

At audio frequencies the same amount of inductance presents a reactance that is too trivial to matter. If you've got a NASA lab of expensive test equipment you can measure it but in the real world - should we care?

Perhaps there are some factors I've failed to consider.

Hopefully I'll be "coffeed" up by the time I read your reply.
:food-smiley-004:
 

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Wild Bill, Weber is talking about running an extra cabinet with the Super Reverb. In that situation only, he wants the 4x10's in the Super to reflect 8 ohms, and the extension cab to reflect 8 ohms, so the Super's OT will "see" 4 ohms (100% mismatch) which it can handle.

You are correct to notice that the minute you unplugged the ext. cab you'd have to rewire the Super back to stock or else be running 2 ohms to 8 ohms for a 400% mismatch, which is bad.

As for Weber's inductance argument, and yours, I merely noticed his tone comments and tried to imagine Sesroh's tone situation, given the possibility that he might choose between a series/parallel and a parallel/series wire-up. He'd have to choose one or the other to get 8 ohms. It's very possible that the inductance business is an impractically moot point, but if Sesroh had to choose.... Weber is a fairly well-known authority on amps.

Peter
 

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Discussion Starter #17
yeah, it all seems complicated for me ahah. I don't know too too much about amps. I think I'll leave it alone until I actually need to run a cabinet as well. as for now, I'll probably find an old bassman, showman or band master head to use with the cabinet.
 
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