Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com
Asher Guitars WD Music Products Amplified Parts Mod Kits DIY Nordstarnd Pickups Warmoth.com

6aq5 Princeton from scratch on steroids

Discussion in 'Shock Brother's DIY Amps' started by nasdak, Dec 4, 2017.

  1. nasdak

    nasdak TDPRI Member

    41
    Mar 22, 2013
    france
    Hello,
    I'd like to share my new build, it's basically a princeton reverb without reverb, with a deluxe LTPI, 6aq5 power tubes with fixed bias and tremolo on the power tubes. rectifier is a EZ80 to fit the PT.
    All parts came from an old B&H tape recorder and a Radiola tape recorder, except for some caps, pots, and OT.
    I added a 3rd amp stage to get some more grit (sounds like mean fuzz actually), that stage can be bypassed with a dpdt switch (you can see the red tip near master volume pot)
    I also fitted a master volume in the "dual lin pot" style.

    Beside aesthetics i'm really pleased with the beast, i have to say it sound really cool, and is dead silent (i had to use shielded cable for all pots and work on the ground very carefuly).

    [​IMG]
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  2. nasdak

    nasdak TDPRI Member

    41
    Mar 22, 2013
    france
    I forgot the schematics :)
    [​IMG]
    ampli3.JPG
     

    Attached Files:

    Last edited: Dec 4, 2017
    dan40 likes this.

  3. rocksmoot

    rocksmoot Tele-Meister

    159
    May 6, 2012
    Rogers, Arkansas
    Great cabinet, love that look. It's nice to have a little room to work, isn't it? How close is it's tone to a blackface Princeton?
     

  4. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    So...you have an AA165 Bassman with small power tubes, bias vary trem and a switchable gain stage to make it into an AB165 Bassman. Hot amp, I would think. Kudos...
     

  5. nasdak

    nasdak TDPRI Member

    41
    Mar 22, 2013
    france
    Thanks :)
    Yes it's nice to have space, but i didn't use any board so i have to mount "on the fly" and it can be tricky :D
    I never heard a real BF Princeton (only youtube samples) but it seams really close, especially with vibrato :) and on the clean side.
    When pushed, the LTPI must make it somehow different. And with the 3rd amp stage engaged its another story :). Plus it's wired to a 12" weber alnico...
    Thoose 6aq5 are great tube, and you can get NOS for cheap!

    I'll try to make some samples later :)
     
    Last edited: Dec 4, 2017

  6. nasdak

    nasdak TDPRI Member

    41
    Mar 22, 2013
    france
    I have one question though : i used the lar-mar (?) master volume trick, but with bias-vary trem. I don't think i've ever seen that. Is it ok ?
     

  7. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    Nasdaq, what you have built has the basic AB763 BF preamp along with the bias vary trem from the BF Princeton. The PI is a fair difference...just a bit more gain than the cathodyne. when you engage that third gain stage, you then have a preamp like the AB165 Bassman Normal channel....which is unlike any other BF/SF circuit in that the third gain stage is not inhibited by the loss of gain that occurs in the reverb amps. The reverb amps have three gain stages in the Vib channel, but the effects in this channels suck a lot of gain out of the circuit. The AB165 Bassman has a hot Normal channel...and that is what you have built...albeit with 6AQ5’s, which are small bottle versions of the 6V6.
     
    nasdak likes this.

  8. nasdak

    nasdak TDPRI Member

    41
    Mar 22, 2013
    france
    Thanks :)
    I tried to use a 3rd stage as i had a spare triode to use (only one half of the 12ax7 is used for the trem).
    I got the idea from the tw express schematics.
    But righr no i'm not very pleased with my switch because i cannot use it as a "boost".
    I'll try to explain, let's say it's position 1 with 3rd stage off and pos2 with 3rd stage on.

    On pos1, i can get a very nice clean note, with the gain low and master volume at noon. 2nd vol pot has no effect as i is bypassed too.

    Then i switch to pos2 ; i still get clean unless i crank the second vol pot, and then the gain is there volume is way much higher than pos1. I have to lower the master volume to maintain about the same volume.

    So basically i'd like to lower the volume on pos2 only :) so i can use it as a "lead channel" live

    Any idea ?
     

  9. Wally

    Wally Telefied Ad Free Member

    Mar 17, 2003
    Lubbock, TX
    okay, I now see that third stage is a cold clipper as in the Express. I have no cures for the imbalance you have there...except to find the balance with the 2nd gain.....that is, don’t dime it. If the Gain in that pot comes on all at once at the end of the sweep, perhaps you need to consider a different pot there??....or....it just occurred to me that you might move that second gain control to a position following that third stage???
     
    Last edited: Dec 5, 2017

  10. nasdak

    nasdak TDPRI Member

    41
    Mar 22, 2013
    france
    Yeah i thought about it too : move the 2nd gain pot after the third stage, so 2nd triode its the 3rd stage hard and 2nd gain pot can be used to set the volume. It would then be a "lead channel volume" pot :)
    I'll try that !
     

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