Princeton Reverb Scratch build

Discussion in 'Shock Brother's DIY Amps' started by 2pupwonder, Feb 1, 2017.

  1. 2pupwonder

    2pupwonder TDPRI Member

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  2. 2pupwonder

    2pupwonder TDPRI Member

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    So here are my thoughts on sourcing etc...:

    - Make my own Cab - probably last step, or very first, probably charcoal grey tolex with silver fender grill cloth and black piping. (colors are irrelevant at this point but having a mental image of it keeps me on point) Going to use a blackface stock.
    - make or buy a turret board from Hoffman, probably buy the turrets from him and make my own with GA-10 boards from McMaster-Carr
    - Get chassis from someone who makes them (i have someone in mind) doesn't matter who as long as it fits.
    - ClassicTone tranformers - may want to upgrade to DR tranformers, any thoughts here?
    - Reverb - probably a MOD unit - anyone have issues with these?
    - Small parts from either Hoffman or Mouser.
    - Jacks pots etc.. probably same as above.
    - Speaker - i have a Champ XD 10" i could use for testing, would probably go with a Eminence GA-10 or Legend 1058 finally.

    I'm going to go thru the schematic and make a parts list from Mouser. If anyone is interested in my resources, i'm willing to share them in exchange for nuggets of wisdom on building :)
     
  3. BobbyZ

    BobbyZ Doctor of Teleocity

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    If I, a guy with zero woodworking skills can learn how to build cabs, anyone can. I'm OCD so had to do 1/4 finger/box joints. Watched a couple of YouTube videos and slapped a jig together for my very cheap little table top table saw.
    Also learned, from my brother, that I didn't need a Dado blade set up for 1/4 in cuts, just two blades stacked.
    That set up sometimes isn't real clean but the rounding over router cleans it up nicely and anthing else gets filled with body filler. (Bondo drys in minutes and sands easy)
     
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  4. BobbyZ

    BobbyZ Doctor of Teleocity

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    Since you're building a PR looking at gut shots of originals will be helpful. Notice the way the filiment wires are twisted on one of Leo's compared to the way alot of builders do it. Two hundred feet of wire wound up so tight it fits inside. You don't need that much. lol

    Here's a shot of a 64 AA764. 20160308_212323.jpg
     
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  5. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    Those can be tricky if you have never done them before. In a BF/SF amp they need to be twisted as tightly as possible and arched over everything (with no wires near them); in tweeds they are tucked in along the chassis edge after twisting.

    But it's the twisting that's tricky - it's nearly impossible to do by hand and have them tight enough. Use solid-core wire only on filaments (and possibly grounds) - it holdss the twist better than stranded wire.

    Then insert the two wires in a drill chuck and twist them using slow speed. THAT will get a tight twist! And a tight twist aids noise reduction.

    Last, when soldering them in place be sure the power tube filaments are all wired to the same pins (observing polarity - even though filaments are usually AC consistent polarity is important). Then do the same with all the preamp tubes and driver.

    That's something not usually mentioned in the instructions (neither is proper sequencing following the power flow, with testing after each stage - power section, power amp, preamp, jacks & controls)
     
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  6. Sandhill69

    Sandhill69 Tele-Holic

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    And echoing BobbyZ's comment about two hundred feet of wire, be generous when you buy, and if your tightly twisted pair is just a bit short, pitch it and start over. Don't give in to the temptation to unwind a turn or two to gain a quarter of an inch.
     
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  7. Silverface

    Silverface Poster Extraordinaire Ad Free Member

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    +1
     
  8. 2pupwonder

    2pupwonder TDPRI Member

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    It looks like a lot of layouts have a cap can recommended for the filtering. according to this white paper, cap cans can introduce noise. they recommend having at least the primary filter cap being a standalone, not in the cap can. Does anyone have experience with this? i may try it both ways as the caps are only 10-15 buck either way... however if anyone has had experience with a particular method and found it distinctly superior, i'd rather do it that way.
     

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  9. 2pupwonder

    2pupwonder TDPRI Member

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    Thanks for the tip, very interested in having the lowest noise floor possible. that's one of the reasons i'm scratch building.
     
  10. 2pupwonder

    2pupwonder TDPRI Member

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    any reason to go with DC filaments?
     
  11. Dan Miller

    Dan Miller Tele-Meister

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    Watching with interest, as I will be resuming my PR build when I get home in March.

    Dan
     
  12. 2pupwonder

    2pupwonder TDPRI Member

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    Nice! interested in your descisions, what kind of transformers etc... if you have time.
     
  13. mgwhit

    mgwhit Tele-Holic

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    Nope.
     
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  14. Phrygian77

    Phrygian77 Tele-Afflicted

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  15. 2pupwonder

    2pupwonder TDPRI Member

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    Didn't realize Zach sold on Reverb as well as Ebay... This is what i was gonna get. Every review i've seen on him is positive.

    BTW did you scratch build one of these as well?
     
  16. Phrygian77

    Phrygian77 Tele-Afflicted

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    It's really nice. It looks like it's CNC punched and folded. No sharp edges or burrs anywhere.

    No, I built a 5F1 Champ in mine! LOL! I actually bought the chassis to experiment with. I had a silverface PR years ago, so I'm not really interested in building one. If I do build out a blackface circuit in it, it would be a single channel AB763 Deluxe Reverb w/o tremolo (or maybe try to squeeze in bias trem using an SS rectifier, and an octal to 9-pin adapter plate).

    This is my build thread for the 5F1:
    http://www.tdpri.com/threads/5f1-in-a-pr-chassis-for-now.700778/
     
  17. clintj

    clintj Friend of Leo's

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    Want to squeeze a little more noise reduction in? Check out this:

    http://www.aikenamps.com/index.php/where-to-connect-the-outside-foil-on-capacitors

    If you look at gutshots of vintage Fenders, you'll see the black stripe on the coupling caps consistently follows this article.

    Since you're shopping Hoffman or Mouser, upgrade your resistors to 1W metal or carbon film. Metal film is slightly quieter, and larger components are quieter.

    Tight twist on heater wires is good, but not so tight you overwork and make the copper brittle. What's more important is that they twist tightly right up to the pin. If you untwist them to make your connections, you undo all the hard work you just put into it. That last inch is really close to signal wiring, and is the most important.
     
  18. dan40

    dan40 Tele-Afflicted

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    You asked about a cap can versus using single caps for the power supply. Using the single caps will allow you to ground the preamp cap with the other preamp grounds and the screen and reservoir cap with the power grounds. The only problem with this method is that you may not have room to add the extra caps if you are building an exact copy. Using the cap can does free up alot of space in the chassis but you are limited in your grounding scheme.
     
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  19. 2pupwonder

    2pupwonder TDPRI Member

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    Thanks. Also, is there any advantage to stiffening the primary reservior cap? spec is 40-47 microfarads, is there any avantange to using a 100?
     
  20. Mart the Hat

    Mart the Hat Tele-Meister

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    Which rectifier are you using? The datasheet for that tube type will specify the maximum reservoir capacitor. IIRC 100uF is higher than recommended for either a GZ34 or 5U4.
     
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