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'68 Custom Princeton Reverb vs. '68 Princeton Reverb

Discussion in 'Amp Central Station' started by EsquireOK, Apr 17, 2020.

  1. Bob Womack

    Bob Womack Tele-Afflicted

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    That is my understand of the threads I've read. A cap and a resistor in the tone stack and a resistor in the negative feedback circuit, if I remember correctly. One of the resistors doesn't even need to be changed or removed - you just need to jump over it with a piece of wire, so you can go back and forth really easily. The speaker is also different. Wait a sec - I found the site that has the exact component swaps and it lists SIX for exact duplication. It shows what to do to switch either amp to the other. It is HERE. I hope that helps. You can pick and choose the items you want to change for their effect.

    HERE is a thread on just the jumper bass mod. It references THIS thread on the TDPRI.

    Bob
     
    Last edited: Apr 18, 2020
  2. bradpdx

    bradpdx Friend of Leo's

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    I’m the guy who did the frequency response charts for the 68 CPR. I still use it as my primary amp for a lot of things, and I’m very fond of it “as is”. The only change I made was to replace the reverb tank with a longer delay version. I even like the silly Celestion speaker.

    No, it’s not a reissue per se. It’s another small tube amp variant based on the Princeton. It definitely has more bass, which I keep turned down to 2 or 3. But with the treble at 7 or 8 it really gets a wonderful character for Tele and Strat, with a throaty middle and always a bit of grime around the edges due to the reduced negative feedback.

    I’ve played plenty of real BF Princetons. The 68 CPR feels like a cousin to those - definitely in the family, but not identical.


    Sent from my iPad using Tapatalk
     
  3. randym

    randym Tele-Meister

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  4. 39martind18

    39martind18 Friend of Leo's

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    off of evilbay. Got several, for the PRRI, my 2X10 Deluxe Reverb, and one for my lead player's Twin. Since he's respeakered the Twin with Jensen Neos, due to age and weight issues (amp weight and his age), that badge is probably available.
     
  5. randym

    randym Tele-Meister

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    Let me know if it's available. None on ebay right now.
     
  6. radiocaster

    radiocaster Poster Extraordinaire

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    Actually it looks like only one of the caps on the tone circuit of the 68 is from the 5F6A, one of them isn't and it's the same as on the 65 (and perhaps other blackface amps in general), the last cap is common to both.

    I might not know what I'm talking about, but I don't think the other caps in the 68 make it bassier. I would bet just the negative feedback resistor does. The other changed resistor just lowers the reverb level.

    The speaker probably makes it bassier too.
     
  7. Wally

    Wally Telefied Ad Free Member

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    I stand corrected.....Fender did not go as far as I usually do in ‘tweedifying’ that tone stack. If there is too much bass, change the bass cap to a smaller value. Change the slope resistor from the 100K to a smaller value to move the mid bump up. Don’t blame the NFB loop,for the bass....that is not where the ‘problem’ is, imho. I would not have that 18K resistor in the circuit, either.
     
  8. branbolio

    branbolio Tele-Meister

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    Anyone still digging their 68 Custom
     
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