NAD 68 princeton reverb custom

Discussion in 'Amp Central Station' started by Buffalo0993, Sep 24, 2013.

  1. Buffalo0993

    Buffalo0993 Tele-Holic

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    I'm not getting a new speaker anymore, I ordered a new speaker because the sound when I first got it was horrible but it had a loose tube it sounds great now
     
  2. tgftele

    tgftele TDPRI Member

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    Me too, why oh why does Fender not mention this fact, that the PRRI has wired tube sockets, and even show the open chassis so people can see it! Looks tight to me--much better than online research would have one believe...
     
  3. barfoden

    barfoden Tele-Meister

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    The changes to the circuit are in the tonestack. THey announce it as a bassman stack but i think the placement of the tonestack is similar to the blackface tonestack. I just think they altered the values of the existing tonestack to get it more into bassman range allthought the tweed bassman tonestack is feed from a cathode follower.

    Yes and decreased the negative feedback to give you more of a vintage feel. A wilder less tamed sound with less speaker damping, which will break up a little earlier on the dial and allow more of the circuits resonance overtones.

    A
     
  4. Guitarace

    Guitarace TDPRI Member

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    68 Custom Princeton Reverb Bias Trim Pot

    Buffalo, thanks for sharing the pic of the 68 CPR guts. Is that the bias trim pot located just off the NW corner of the circuit board? Is the adjustment of this pot accessible from the tube side of the amp? I can barely see some kind of access hole on the tube side of my 68 CPR kind of under the speaker baffle behind a big black transformer thing. Just trying to verify I can retube the amp and adjust bias without having to go into the guts and be exposed to the high voltage. Thanks for any input!
     
  5. Joe K

    Joe K Tele-Holic

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    I hope someone can answer as I have the same question. Thus far, it looks like you have to drop the chassis on this amp. Hope I am wrong.
     
  6. Buffalo0993

    Buffalo0993 Tele-Holic

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    No it's not accessible externally
     
  7. deytookerjaabs

    deytookerjaabs Friend of Leo's

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    NICE amp. I've played through a few of these in the past year and am always overly delighted with the tone.
     
  8. Guitarace

    Guitarace TDPRI Member

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    Do you know what the hole is? Seems like it would be directly under the spot where your guts pic shows the bias trim pot. Thanks for your help!!
     
  9. Buffalo0993

    Buffalo0993 Tele-Holic

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    Not sure honestly, don't own the amp anymore.
     
  10. Johnny Cache

    Johnny Cache Former Member

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    Sounds like you may have had a loose tube. I think the Custom 68 is a great amp on it's own merits, I think the speaker and lower NF were intended to have a more break-up than the PRRI. Don't know if a new speaker will improve that or not.
     
  11. Guitarace

    Guitarace TDPRI Member

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    Joe-
    I slid the amp out of the cabinet. Yes, there is a bias trim pot adjustment, but you do have to slide the amp out about half way to get to it. image.jpg it is on the tube side of the amp behind the black transformerlike thing.

    Good luck, I'll be biasing my amp when the tubes arrive.
     
  12. gryffsmyth

    gryffsmyth TDPRI Member

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    I can't quite see from the pics - does anyone know if the screws holding in the tube sockets have nuts securing them on the inside? One of the screws on a pre-amp tube socket on my 68CPR is rattling and spinning in place - I assumed it was stripped but now I'm wondering if there's just a nut on the other side? Anybody know? Wanted to check here before I open it up or take it to a tech.
     
  13. gryffsmyth

    gryffsmyth TDPRI Member

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    Also, and please correct me if I'm in the wrong place to be asking this - but if the hole is stripped and there's no nut, couldn't I fix the rattle by securing the screw with a nut on inside of the chassis?
     
  14. jimash

    jimash Friend of Leo's

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    I love mine.
    I was very gentle with the speaker for about 2 weeks of playing an hour or two a day.
    About that time the extra-extra bass calmed down to just extra, and the speaker started to react to the higher levels and distortion much better.
    I am very much in favor of gentle break in, because all the ones I tried in stores sounded broken.

    http://celestion.com/speakerworld/guitartech/3/104/How_to_break-in_a_guitar_speaker/
     
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