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Updates on 81 Pro Reverb problems

Discussion in 'Amp Tech Center' started by Axer57, Sep 28, 2017.

  1. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    I've always just heard audio or linear taper - I figured there were levels of each but hadn't got into that.

    Still, @Axer57's volume shouldn't jump quite like that.
     
  2. D'tar

    D'tar Friend of Leo's

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  3. Axer57

    Axer57 Tele-Meister

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    When I get the tone I want at the lowest possible volume , here are my knob settings. It's the same for both channels:
    Vol-3 , Treble-8 , Mid{vibrato channel only]-3 , Bass -6
    I have played thru 3 guitars. 50's Tele RI , 60's Strat RI , and a 72 Thinline RI. They all sound fantastic at these settings. When I turn either volume to 4 , I get outdoor volume.
     
    Last edited: Nov 16, 2017
  4. LudwigvonBirk

    LudwigvonBirk Tele-Holic

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    are the pots the right value? If the amp is "wide open at 4", that seems like it could be too-little resistance value in the volume pot.

    1Meg Ω, Audio taper is (I believe) what should be used.
     
  5. Axer57

    Axer57 Tele-Meister

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    yep , I ordered all the pots from Mojotone. They are all exact to the AB763 layout. Possibly I just wasn't aware of how an old Super Reverb sounded. I've never owned one. I have been watching 65 Pro Reverb videos and it seemed that everyone gets the tone I like at much lower settings. Today I started watching Super Reverb videos , quite a bit of difference. They all talk about how loud Supers are and I can believe it. This amp reminds me more of a twin. It gets really loud. I tried each number all the way to 10 and this thing just keeps climbing. At 8 it sounds like full arena volume to me. Maybe it's been too many years since I played anything this loud...lol
    Only reason I thought there might be a problem was , The sound doesn't come on till about 2 1/2 and is very muffled until I reach 3 .
     
    Last edited: Nov 16, 2017
  6. clintj

    clintj Friend of Leo's

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    Supers are beasts. I'm running a set of inefficient speakers in mine, and it can still shake things above 5. Plenty of plate voltage, huge transformers, and that speaker array give it some real authority.

    And yeah, mine sounds a little thin/muffled below 3. From there on up, it starts to breathe and sound full.
     
  7. Axer57

    Axer57 Tele-Meister

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    ok...that means mine is running right....cool. I did buy a different set of speakers. I don't know if they will be better , they are 1963 Rolla 12" , 8 ohm , 50W alnicos. Got the set for $75.00 . They supposedly came from an old Hammond . Don't know how they will sound in the amp but they looked like a pretty good deal.
     
  8. grolan1

    grolan1 Friend of Leo's

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    Not sure I agree with a SR sounds thin below 3, I play mine all the time around 1-2 and it sounds fantastic.. a key is when you play at low volumes the EQ settings are much different than higher (low volume=EQ set much higher than higher volume settings) - but each to their own right... ;)
     
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  9. Axer57

    Axer57 Tele-Meister

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    I generally go for the early SRV sound {El Mocambo}. This amp gets pretty close. I just wasn't prepared for the volume. This thing would rival an old Super Twin Reverb I used to own...
     
  10. Axer57

    Axer57 Tele-Meister

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    I watched a video of a guy doing SRV and he used a Super Reverb . He said he pulled V1 and V5 to give more sustain. I tried it in mine and I didn't really notice a big change. Anyone ever try something like this?
     
  11. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Pulling V1 is suuuuper common since it increases the gain on the reverb/vib channel. Pulling v5 is what...the reverb? So you wouldn't have anything loading down that portion of the circuit, but not sure that would result in an increase or change of anything.
     
  12. Axer57

    Axer57 Tele-Meister

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    I think V5 is the Vibrato tube.
    Honestly the biggest difference I have found is all about what overdrive you use. I have about 6 or 7 different OD's , everything from a maxon 808 to a TS5 modded. The best SRV sound I have found is an EH East River drive. I swapped all the Jamecon Ecaps for Nichicons and replaced the non-polar 1uf caps with Panasonic stacked Polyester film caps and it sounds very close to the early SRV sound.
     
  13. Axer57

    Axer57 Tele-Meister

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    can anyone tell me , how high voltage the 10pf cap , running parallel to the 3.3M resistor , needs to be?
     
  14. clintj

    clintj Friend of Leo's

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    It's a low voltage spot; it really shouldn't see more than a few volts AC and very little, if any, DC. I can't remember what the lowest rating you can get a 10pf in is, but even a little 25V one will do nicely.
     
  15. Axer57

    Axer57 Tele-Meister

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    ok thanks. My amp has a 500v silver mica there. I am guessing that was all the tech had laying around. Is it the same for the 250pf cap in the tone stack?
     
  16. corliss1

    corliss1 Friend of Leo's Platinum Supporter

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    Yup - that one gets pretty low voltage too.

    There's nothing wrong with using high-rated voltage parts - it just ensures that you have a higher margin of safety is something other part were to short out or have an issue. The voltage rating of parts doesn't affect how the circuit behaves at all.
     
  17. Axer57

    Axer57 Tele-Meister

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    ok thanks. I'm just not used to seeing silver mica in a Fender amp.
     
  18. clintj

    clintj Friend of Leo's

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    The tone stack caps see 270VDC per the schematic. I'd follow the schematic recommendation of minimum 400V rating there. The reverb circuit one earlier is connected to the grid of a normally biased 12AX7, and is surrounded by larger blocking caps, plus has a few leakage paths to ground on either side. It shouldn't see DC if the rest of the circuit is working right.
     
  19. LudwigvonBirk

    LudwigvonBirk Tele-Holic

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    Axer57, how is it going with this amp?

    (You were really persistent with the fixes and debugging, and cool about it, so hope all is well but if not please surface the prob!!)
     
  20. Axer57

    Axer57 Tele-Meister

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    Sorry bout the long absence.... Life has thrown me a few curves this year...Wanted to let everyone know. The Pro Reverb is still purrin and sounds great. Haven't had any more issues. Thanks again for all your help.
     
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