Ab568 Super Reverb headroom

Discussion in 'Amp Central Station' started by jc4yr, Jan 10, 2019.

  1. jc4yr

    jc4yr TDPRI Member

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    hey yall,

    I just got a 69 drip edge super in a trade. I love it.

    I thought it was AB763 but a look under the hood has shown me otherwise. It looks like the bias was set back to 763 though. It sounds great!

    My question is about the 5u4gb in it. I’m wondering if it would raise headroom if I switched it back to a gz34 (in theory)??Looking to raise my clean threshold.

    I’d have my tech swap it to make sure the tube agrees with everything in the amp.
     
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  2. fendrguitplayr

    fendrguitplayr Poster Extraordinaire

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    One of the best amps I ever played through. Congrats!
     
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  3. Old Tele man

    Old Tele man Friend of Leo's

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    GZ34 will raise voltages, it's designed for 5U4GB voltage drop.
     
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  4. jc4yr

    jc4yr TDPRI Member

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    Bumb about gz34 headroom pleaseeee
     
  5. schmee

    schmee Friend of Leo's

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    I doubt there will be much audible difference. You might have your bias adjusted a bit colder if you want more headroom, but you should have tons of headroom from that amp.
    What speakers are in it? What pretubes in V1 or V2?
    Keep your bass and mid settings 5 or below. 4 better.
     
  6. Wally

    Wally Telefied Ad Free Member

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    Jc4yr, has the amp been recapped? If not, all other avenues to achieve whatever are of little value until the caps are fresh, ime. A healthy SR should have enough headroom/clean volume to do almost anything one would want to do. If not, get a Twin Reverb.
    With the volume at 5 and the tone controls at 5, the amp should yield clean and lively tones....and be louder than most folks would use these days....or so I am led to believe by what I see and read.
     
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  7. BobbyZ

    BobbyZ Doctor of Teleocity

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    Totally agree with Wally, make sure it's healthy, old or original electroltics will suck the life out of an amp.
    To put it in prospective, I recently bought a 66 BF Super Reverb, that amp cranked way up 7-10 was only about as loud as my 73 Super Reverb on about 3 and distorts the bass notes. (farts out)
    Crank the 73 that much and the cops show up! I ran a speaker cable from one amp's speakers to another just make sure it wasn't speakers.
    The 73 has the 5u4, I can't see changing that to a GZ34 or SS to add more headroom or volume, it's got more than enough now.
    Unless you're playing stadiums, without a PA not enough headroom isn't going to be an issue ever with a healthy SR.
     
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  8. jc4yr

    jc4yr TDPRI Member

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    Thanks for that. I agree. The caps are original and I really like the way it sounds so I was trying to avoid a recap. But I’ll uave to get it done it sounds like. Appreciate your wisdom. Thank you
     
  9. bigben55

    bigben55 Friend of Leo's

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    I'd get that cap job.

    My 66SR, with its low watt alnico speakers, had more headroom than I'll ever need, probably more than I'll ever be able to use. Haven't been able to gig it above 3.5 vol yet. I kind of quit trying.
     
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  10. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    Never, ever, leave original caps that old in anything but a museum quality amp that will never be played. The service life of the caps is 15-20 years, - that amp should be on its THIRD set of filter and bias caps at this point.

    The amp may sound fine, caps may look fine - but both are totally irrelevant. Old caps are time bombs and can blow with NO warning. And that can be a real expensive mistake - not just in the repair cost, but in lost value.

    With original caps I would not turn it on. Every single time you turn it on you're rolling dice with about a $500-700 "bet" on the line (transformer replacement plus lost value).
     
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  11. Wally

    Wally Telefied Ad Free Member

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    I have witnessed this type of scenario countless times...”I really like the way it sounds...”...when in reality the amp sounds nothing like it would have when it was working with string electrolytics. Once the amp is recapped and serviced, their eyes go wide with the difference. The amp has a firmer attack, more sparkle, more harmonica, elimination of out of tune subharmonics, and.....more headroom with a three dimensional sound stage as opposed to a flat and sterile soundstage. It happens every time, ime.
    Check out the 5th fret A on the low E string. Pick it and listen....the attack is soft and the note doesn’t have a good tone. There are some out of tune subharmonics there. Go up the fretboard on the treble strings....their is no real BF/SF Fender sparkle there. All of that changes with a recap and proper service, ime.
    I was raised a mechanic’s son back in the age of mechanical creation of spark for engines. There was a set of points and a condenser in those distributors. Whenever the pints were replaced, we replaced the condenser as a matter of course....because that condenser was a capacitor that stored and released the electrical charge. The analogy for our amps would be this. You could change the plugs in the engine...those are the tubes in the amp. Well, thatmight not get the job done...because the plugs only provide the means for using that electrical spark that comes to them through the wires from the points. That electrical charge begins in the condenser...a capacitor. You could change the points if they were worn out. That might not do much good either IF that condender(capacitor) was weak. When you provide a fresh capacitor to store and provide the electrical charge, only then could the points and plugs do their job.
    We didn’t even question it...that condenser got changed...every time. The dialectics in these caps weaken with age.....even if they ‘work’ they cannot possibly do the job for which they were designed in the way they did when they were fresh.
     
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  12. sds1

    sds1 Tele-Holic

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    If the caps are original there's no way the amp sounds better than it should, that's for sure. At best you are just kicking the can down the road, at worst the amp sounds like crap compared to what it should.

    I agree that the rectifier change is not a massive clean headroom upgrade.

    Repair and scheduled maintenance aside, if your power tubes are tired and especially if they are out of balance (drift and or bad bias balance setup )... Bye-bye clean headroom.
     
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