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More headroom for my Reissue '68 Custom Princeton Reverb

Discussion in 'Amp Central Station' started by Grandchamp, Mar 25, 2014.

  1. T Prior

    T Prior Poster Extraordinaire

    Mar 17, 2003
    Charlotte NC
    It's the classic argument , we argue VOLUME when we mean to argue headroom. The Twin reverb is no good as it's too loud . But yet so far, nobody has ever complained about the clean headroom, have they ? Then we commonly read with regard to the low watters, , "for me it is perfect, how much headroom do you need " ? Which is totally irrelevant. I have a Chevy, why do you need a Ford ?

    Headroom, once again, is an artifact of the amp design, which tube circuits and what will be the HI DC Power supply source. Then an OT is selected to match the circuit and the design . We don't change the design by changing a tube or a speaker, we alter the original design. We don't make it better.

    Early Amp break up is exactly what is required for some players and a deal killer for others. It is not a one shoe fits all scenario, far from it.

    TRUE. I bought a first issue 40 watt Hot Rod Deluxe. Loved it until I started doing double duty with it, Pedal Steel and Telecaster. I wanted it to work, I loved the amp, the weight, all that. I went thru speakers , tubes, all that stuff, never really got it to function any better than stock with regard to headroom for the Steel.

    I did finally fix it though. I sold it and grabbed a 60 watt HR Deville, problem solved !

    A PRRI is not going to perform headroom wise like a DRRI and the DRRI will not perform headroom wise like a Blues or Hot Rod Deluxe and a HR Deluxe will not perform headroom wise like a Blues or HR Deville. And , they are all not supposed to !

    But don't get a Twin Reverb they are too loud...:rolleyes:

    The op should at least upgrade to a DRRI and see if that works for him. The good news is that it has a very similar tone stack
     
    Last edited: Apr 2, 2018

  2. Bob Womack

    Bob Womack Tele-Meister

    Congrats! Win-win!!!

    Bob
     
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  3. twobuckchuck

    twobuckchuck Tele-Meister

    117
    Oct 21, 2015
    California
    I’d love a tutorial on this. Does it change the noise floor at all?
     
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  4. TimmyV

    TimmyV Tele-Meister

    408
    Aug 11, 2014
    Ohio
    Not noticeably. When it’s in blackface mode it may be a tad noisier but the 65 prris are noisier that the 68s. As far as the tone stack mod goes . I removed the bass control pot and replaced it with a a250k push pull pot. I removed c23 which is the bass tone capacitor. I then ran two leads from that spot to the middle two terminals of the push pull switch. I then took that c23 cap (.022k 400v) and wired it across the top two terminals of the push pull switch. Then I wired a .047 400v capacitor across the bottom 2 terminals of the push pull switch. So now when the bass control knob is pushed in its in blackface mode or 65 prri and when it’s pulled out it in bassman or 68 custom mode. You do get a slight pop when you pull the switch out the first time. I will probably wire a small resistor in line with the switch to ease that. It’s not a big deal to me. I’ve already revised the negative feedback mod. It involves removing the external speaker jack and replacing it with a 500k pot . Then replacing r10 with a 2.7k 1/2 watt resistor. This mod lets you go from blackface to brownface to tweed breakup . So all in all I have the ability for this to be several different amps in one. Plus throw in the reverb and tremolo and I don’t know what else you could ask for:)
     
    Last edited: Apr 4, 2018
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  5. twobuckchuck

    twobuckchuck Tele-Meister

    117
    Oct 21, 2015
    California
    That’s awesome. Thank you so much. If you happen to open it again I’d love to see some pictures, if not a big deal. What a great amp you ended up with!
     
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  6. TimmyV

    TimmyV Tele-Meister

    408
    Aug 11, 2014
    Ohio
    Thanks:) I’ll do that.
     

  7. Little Jay

    Little Jay Tele-Meister

    371
    Jul 20, 2009
    The Netherlands
    Wow, that’s a smart mod!
     
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  8. jgmouton

    jgmouton Tele-Meister

    Age:
    76
    409
    Jun 21, 2009
    Europe
    I'm surprised because about 2 years ago I ordered a new Custom 68 and returned it because it was too noisy (the reverb and the trem were unusable, far too much hiss). I ordered the 65 PRRI instead and it was ok with the noise. I kept the 65.

    I must say that I'm in Europe and I read somewhere that Fender changed components in the 68 to accommodate EU mains spec. Maybe that's the reason...
     
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  9. uriah1

    uriah1 Doctor of Teleocity Silver Supporter

    Feb 12, 2011
    Around
    I did the dirty deed. This has max overhead.
    prin1.jpg prin2.jpg
     
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  10. bradpdx

    bradpdx Friend of Leo's

    Jul 16, 2006
    Portland, OR
    I use my 68 CPR all the time for gigs and recording. Stock Celestion, MOD long-decay reverb tank. My entire reason for using it is to have less headroom than my good old (loud) original 65 DR. When I need headroom, I grab the DR. When I want that mild dirt all night long, I grab the CPR.

    The 65/68 switcharoo mod is pretty darn cool, though!
     
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