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Post subject: Blackfacing an early 1970's fender amp vs. Keeping it stock
Posted: Sat Mar 23, 2013 10:21 am
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Roadie
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Hello. I'm new to the forum. I have a 1972 Super Reverb-totally original. With all the talk about blackfacing, how many folks prefer the sound of a stock Super Reverb to one that's been blackfaced?


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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Sat Mar 23, 2013 10:28 am
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Have you ever actually played a pre-68 Super Reverb?

Arjay

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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Sat Mar 23, 2013 10:39 am
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You know, if that amp is reliable and has fresh lytic caps in it --- maybe you should look for good tubes. Good 6L6GCs and perhaps, a nice GZ34 rectifier to replace the 5U4GB (if that is what is in the amp now). Have the output tubes correctly biased.

Just a thought. Nice amp. Have any photos?


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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Sat Mar 23, 2013 12:10 pm
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Krankster...I owned a very nice 72 Super Reverb and it was a GREAT amp...get it up back to factory spec and enjoy it for the amp it is. Don't blackface it!

Here is a pic of mine and what a great sounding amp it was!

Image

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T2

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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Sat Mar 23, 2013 3:36 pm
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Totally agree!!! I would optimize the amp in stock form and find the sweet spot!!! Art

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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Sat Mar 23, 2013 4:09 pm
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aclempoppi wrote:
Totally agree!!! I would optimize the amp in stock form and find the sweet spot!!! Art


+1!

That plus the "right" speakers will generally yield the legendary Super Reverb vibe.

Arjay

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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Wed Mar 27, 2013 10:16 am
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Thanks for the responses. I have played a blackface Super, not sure of the year. I own a 1964 Concert and used to own a 65' Twin. I shouldn't have sold that one. The Silverface amps sound different-brighter, breakup is not quite as smooth-but they still sound great. That's a pretty Super T2stratman. Mine is not nearly as nice looking. I would agree that keeping it stock is the way to go. The electrolytics look good as do the rest of the components. With a 5U4GB, it biases around 33.5 ma using GT6L6GE #5 tubes. It's nice to be able to balance those tubes due to the poor matching. I think many folks like to run their tubes hot. Silverface amps are set on the cool side which accounts for much of the tone. So, if it ain't broke don't fix it.


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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Wed Mar 27, 2013 10:41 am
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Generally, the silverface amps push higher plate voltages in an effort to achieve more clean headroom. This accounts for their diminished propensity for compression and breakup, which is usually manifested by a tone that's perceived to be "brighter". As well, by 1968 Jensen was no longer providing OEM speakers to Fender and the Utah's that replaced them lacked a balanced midrange frequency response.

HTH

Arjay

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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Thu Mar 28, 2013 12:54 pm
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One more question. If you look at any AA270 schematic or Layout, you'll see a .02/100v cap that is in series with the 820 resistor inbetween the second .1uf/600v cap and the .1/200v cap. It connects to the .1/200V. It's on every AA270 model, but I have never seen one in any amp and don't see one in my 72' Super which has never been touched. Is this cap important?


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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Thu Mar 28, 2013 1:47 pm
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Krankster wrote:
One more question. If you look at any AA270 schematic or Layout, you'll see a .02/100v cap that is in series with the 820 resistor inbetween the second .1uf/600v cap and the .1/200v cap. It connects to the .1/200V. It's on every AA270 model, but I have never seen one in any amp and don't see one in my 72' Super which has never been touched. Is this cap important?


I see no such cap in the schematic. However, the wiring diagram shows a cap (can't read the value) in parallel with the 820 negative feedback resistor coming off of the speaker output jack. Looks like some sort of treble bypass cap. I've not seen one like that.

http://ampwares.com/schematics/super_reverb_aa270.pdf

It also shows up in the wiring diagrams (but not in the schematic) of the AB568 and AA1069. It does not appear at all in the AB763.

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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Thu Mar 28, 2013 4:19 pm
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That wouldn't be the first "phantom component" shown on a silverface schematic and/or pictorial diagram. The CBS engineering poindexters were notorious for such tomfoolery.

:lol:

Arjay

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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Thu Mar 28, 2013 5:41 pm
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Are we talking about the ceramic disc cap (circled in yellow)? This is part of the PI's input and has HF cutoff to reduce oscillations.

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http://www.webphix.com/schematic%20heav ... _schem.pdf


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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Thu Mar 28, 2013 7:35 pm
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I can't see it in the schematic either, but it's definately on many layouts. I read it as .02/100v in parallel with the 820 resistor and the same scribble is on many silverface layouts. A true mystery. BMW2002Ti, it would be to the left between the silver .1 and the red .1/200. If anyone has an answer, please share.


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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Thu Mar 28, 2013 9:00 pm
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That is an "after-thought" bypass cap on the global feedback network to reduce induced parasitic oscillations. Similar to the one used in Chris; original Bassman setup.

See the 100 pico-farad bypass cap on the GNFB resistor of Bassman AA371 model?

http://ampwares.com/schematics/bassman_aa371.pdf


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Post subject: Re: Blackfacing an early 1970's fender amp vs. Keeping it st
Posted: Thu Mar 28, 2013 9:59 pm
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BMW2002Ti wrote:
Are we talking about the ceramic disc cap (circled in yellow)? This is part of the PI's input and has HF cutoff to reduce oscillations.

Image

http://www.webphix.com/schematic%20heav ... _schem.pdf


BMW,

No, I don't think that is the cap that Krankster is talking about. He referenced a 0.02 in series with an 820 ohm resistor. The closest I can find is a 0.02 in parallel with the 820 ohm feedback resistor. I have circled the two here as best as I can. The cap does not appear in the photo you posted.

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