Cripes! .. The ol' blackfacing a silverface question again.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by drano, May 3, 2005.


  1. drano

    drano Member

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    Twin Reverb bought new January 1977. Never modified. Still has original tubes in preamp section (never been played regularly). Probably appropriate to re-tube the preamp section at this point.

    Is there a difinitive list of modifications to get this silverface to blackface specs? In my reading so far it appears that different "experts" consider changing certain things more or less important than others. Also it appears that there was some evolution in the amps during both the blackface and silverface periods. So it seems that you have to know exactly which silverface you are starting with and exactly which blackface you are trying to get to.

    Am I on the right track here? Are there resources for iron-clad info on what these conversions involve and their respective effects?

    Thanks
     
  2. John Phillips

    John Phillips Member

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    Most Important: DO NOT RETUBE THE PREAMP. Especially if you're just going to throw out the old tubes. Those original RCA tubes are some of the best-sounding ever made (especially for Fender-type amps) and are almost certainly in perfect working order. I've worked on many Fender amps of this period with them in, and they're usually just fine. Don't change them unless they need changing. There's even a good chance that the original Sylvania 6L6s will be fine, particularly if the amp hasn't been used heavily.

    In fact, the things that are most likely to need changing - due to age - are the filter caps and other electrolytics.

    Is it an 'Ultra-Linear' 135W model? - it will say so under the speaker jacks. These came in in late 1976, so it's possible that yours is. If so, it's not really possible to 'blackface' it, at least not without a lot of modification. They're very good-sounding amps in their own right, for what they do - loud, clean and clear - though. You won't get a good overdriven BF tone out of one, even if you modify the circuit, since the transformers are both different, as well as some other major differences (no choke, for example).

    If it's a 100W model, it's much easier to blackface.
     
  3. garfight

    garfight Member

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  4. drano

    drano Member

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    JP -- don't worry I'm not going to throw away those cool old Fender Special Design Tubes. Even if they failed I could still make them into some kind of a display. I've never seen one so I know it would be unusual to have such a thing. Unfortunately the original 6L6s are long gone. A friend replaced them with RCAs long ago that were not new at the time and probably not matched. When I finally got new matched tubes recently that made it a completely different amp. But how long can the preamp tubes really last?

    The amp is not one of the 135 Watt models. It has an unmarked set pot between the power tube choke and the front of the amp which I'm guessing is the bias trim. But the article garfight references above seems only to discuss replacing caps and resisters with higher quality components, mostly of the same valuues. This seems more like a minor re-manufacture than a "modification." And "good overdriven tone from a Twin" sounds like an oxymoron to me. Will new filter caps really give me that or is there much more to it?
     
  5. hasserl

    hasserl Member

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    You ever hear Toy Caldwell of the Marshall Tucker Band? :dude
     
  6. arfy

    arfy Member

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    There is a pretty thorough checklist of blackfacing steps on the Tonequest site here under the heading Blackface Mods for a Super Reverb:
    http://www.tonequest.com/askour.htm.
    Based on my own limited experience I feel that making sure that last cap before the phase inverter is a .001 instead of the bigger values was very important, although Gerald Weber and some others whose opinions I mostly agree with recommend going a lot bigger there. The bigger values are pure mud to me, especially when pushing the bigger 6L6 amps with a Tube Screamer or other driver. I also found that some of the dropping resistors in the power supply varied from the Blackface to the CBS values and the blackface values brought lower preamp voltages and a 'browner' sound that I liked a lot better on a '72 Deluxe Reverb I used for a long time.
    And don't forget to put in new cathode caps on the preamp tubes, new ones should wake any 30 year old amp right up.
     
  7. drano

    drano Member

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    Yeah, the flute player, right? Does he use one of those old Barcus Berry transducer pickups like Tim Weisberg and then run it into a hot-rod Twin? Mmmmm-mojo, Dude!

    No, seriously though, thanks for the suggestion. My Twin sounds pitiful when the preamp starts breaking up and that seems to happen before the power stage does. But, maybe I don't know what I'm talking about. Can you mention any specific song titles that make it particularly easy to examine this tone Mr. Caldwell has? Or just could you just make it really easy for us and post us an mp3? And, please, not "Can't you see?"
     
  8. hasserl

    hasserl Member

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    If you don't have the album "Where We All Belong" do yourself a faovr and get it. Toy's tone on that whole album is one of THE BEST of all. Absolutely incredible. A Les Paul into a couple of modified Twin Reverbs, the amps pulled from the cabs and mounted into head cabs powering two 4 x12 Marshall Cabs each filled w/ JBL D120 speakers. Awsome tone! The song "Ramblin" stiocks out in my mind, but the whole record is great. Their best IMO. A double record, one from the studio and one live. Get it!
     
  9. Reeek

    Reeek Member

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    I have a 1969 BF'ed Silverface w/JBLs done by Ron Veil, Uncle Spot. I was saying to myself yesterday with my Carvin CT6M how awesome this thing sounds and the natural overdrive is tremendous! I'm runnning JAN Philips 7581As in it with Mullard 12AX7's. The other drivers are RCA.
     
  10. drano

    drano Member

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    I think that's a dead link there, Arf. Are you sure that's the one you meant?
     
  11. arfy

    arfy Member

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  12. drano

    drano Member

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    This may seem like a ridiculously simple question but: what kind of volume are we talking about here? Don't you have to be blowing your windows out to get that kind of sound from a Twin? Where are your knobs set when you get this tone?

    As I turn my channel volume pot up past 5 it just starts working its way from clean to crap. It's a thin useless buzz that I can't imagine anybody using. Pulling the Master pot out just makes it worse. I get better tone from a cheap distortion pedal. As I recall this amp has always sounded exactly like this.

    But I played Bogner, Buddah, Dr. Z, and Zinky this week and didn't think any of their "clean" sounds held a candle to my Twin's clean. I guess after 30 years of playing nothing else I've been conditioned to believe that my Twin is what "clean" is supposed to sound like.
     
  13. TheAmpNerd

    TheAmpNerd Member

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    Depends on how the power supply is set up.
    If you really tighten it up, then the larger value
    caps can sound great and the amp won't sound
    so thin.

    Don't forget, you have tone knobs on your amp
    and on your axe, use them.
     
  14. Reeek

    Reeek Member

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    Funny you should mention "5" on the voluyme pot because that is exactly where my Twin starts to give up that Bluesy grind that we all enjoy. My favortie volume setting for the Twin is 6-7. Yes, it's loud but it's sweet. Other settings are:

    Treble = 5
    Mid = 5
    Bass = 3
    Reverb = 2

    To date, over all, this is the best amp I own. Emphasis on "over all" however. I have many amps that kick ass in their own right but the Twin is never going away. Never.
     

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