Cooperative Amp builds on TDPRI

Discussion in 'Amp Central Station' started by rolloman, Jan 28, 2019.

  1. rolloman

    rolloman Tele-Holic

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    Are all the complete cooperative amp builds in one place where I could look at them and maybe pick one to build?
     
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  2. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Great question - I wish they were! I don't know of any way to search the Shock Brothers forum that will yield results by amp builds. One of the issues is that the titles of the threads are so varied. I am no expert, but you are more than welcome to look at all the pages I dedicated to my amp builds so far. And I have another (5f4 Super) coming soon:

    5f2a tweed Princeton: http://www.tdpri.com/threads/new-and-first-build-5f2a-tweed-princeton.779349/

    5e3 tweed Deluxe: http://www.tdpri.com/threads/new-adventures-in-5e3.796187/

    6g2 brown Princeton: http://www.tdpri.com/threads/brown-princeton-6g2-build.856867/

    BF Princeton Reverb: http://www.tdpri.com/threads/princeton-reverb-build-and-a-question.868246/
     
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  3. rolloman

    rolloman Tele-Holic

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    Well, just you letting me know about the Shock Brothers is a great help. Didn't know about it.
    What I am looking for is a low wattage studio/bedroom type amp.
     
  4. theprofessor

    theprofessor Friend of Leo's

    Aug 8, 2016
    Chattanooga, TN
    Sure thing! Easy: you want a 5f2-a tweed Princeton (in my humble opinion). If you want a blackface sound with reverb, you want a Princeton Reverb.
     
  5. rolloman

    rolloman Tele-Holic

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    Also, I play teles mostly clean, chickin pickin/country or some blues light distortion. I have never really heard those amps. Would they fill the bill for me.
     
  6. rolloman

    rolloman Tele-Holic

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    Wow the 5f2 looks cool. Very simple design.
     
  7. SacDAve

    SacDAve Poster Extraordinaire

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    Warring

    Shock Brothers once you enter you don’t return.
    just ask “theprofessor”
     
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  8. rolloman

    rolloman Tele-Holic

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    Oh I already know how addictive it can be. About time I think I have finally arrived at a place I can begin enjoying actually playing, I find something else to build. Lol

    Just completed a ground up Deluxe Reverb build last week for a friend, and here I am again. Haha.
     
  9. jimgchord

    jimgchord Tele-Holic

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    I agree with the professor. I build and sell these amps often and it sounds like a perfect amp for you.
     
  10. rolloman

    rolloman Tele-Holic

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    Okay, so below I have the links for an output tranny. I have practically all the parts for the 5F2A and I'm gonna build the version with the choke in the power supply. For the output tranny I have and so would like to use the Hammond 125C. Looks like can wire it using speaker lugs (4 & 6 with 4ohm speaker) or (2 & 5 with 8 ohm speaker). What do you think. Am I on track. Lol Still just learning this stuff.


    http://www.classictone.net/40-18115.html
    http://www.classictone.net/40-18115.pdf
    http://www.hammondmfg.com/125.htm
     
    Last edited: Jan 30, 2019
  11. mitchfinck

    mitchfinck Tele-Holic

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    The 125C should be good. I have used the 125DSE on a number of small builds. Your most important factor on which lugs to use is your output tube's load impedance (by output power desired) and speaker impedance. Check out the datasheet for whatever tube you're using (6V6GT if a 5f2a) to look at the Class A (assuming that this is your output configuration for your small amp) and find the load resistance which is then in the matrix you linked.
    From there you should be able to figure out exactly the configuration for you. The tube data sheet will be very helpful in getting everything set up.
     
  12. JuneauMike

    JuneauMike Friend of Leo's

    May 5, 2015
    Alaska
    You can also find amp building resources at EL34world.com and ampgarage.com. Shock Brothers is very very user friendly, but these two have loads of guidance as well as layout drawings etc.
     
  13. muscmp

    muscmp Tele-Holic

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    Jul 1, 2008
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  14. rolloman

    rolloman Tele-Holic

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    Cool. Thanks guy's I will check those out.
     
  15. rolloman

    rolloman Tele-Holic

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    Okay so I built the 5F2. All I had was a 6V6S so chose to try it for output tube. Also used diode full wave bridge PS. It sounds great but has more overdrive and I would like to be cleaner. Can that be achieved by resistor/bias changes? Or will the correct tube help. Following is the voltage readings I took at the places shown on the schematic at the tube pins.
    SCHEMATIC https://el34world.com/charts/Schematics/files/Fender/Fender_princeton_5f2_schem.pdf

    12AX7
    Pin-1 183.7
    Pin-6 186
    Pin-3 1.319
    Pin-8 1.368

    6V6S
    Pin-8 19.82
     
  16. Commodore 64

    Commodore 64 Friend of Leo's Ad Free Member

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    Mar 1, 2010
    Kent, OH
    Well, what you want to try to do, in order to maximize clean, is fully drive the 6V6 with as clean a preamp signal as possible. If you want to get really analytical, you could plot load lines in your preamp (at your actual voltages) and see what you should modify to get you with max clean signal. See Merlin Blencowe: http://www.valvewizard.co.uk/

    Something to consider:
    1. Guitar strum 150mv (single coils?)
    2. V1A = gain of 26 = 3.9V out.
    3 Tone stack. Princeton not very lossy. Let's say 70% of signal comes out so 2.7V out
    3. V1B -= gain of 26 = 2.7*26 = 70V out.

    70V shouldn't clip too, too much in your preamp. Thinking most of the time I scope a 12ax7 I see clipping around 90V.

    So, pretty sure 70V is way more than needed to drive a 6V6, which at your cathode voltage would be able to support a max voltage swing of about 40V before clipping. So there are 2 things causing your overdrive:

    1. Non center biasing of preamp (180/1.3 might be cool bias)
    2. Power tube Overdrive.

    In case 1 you can mess with cathode resistors.
    In case 2 you can mess with the bias of your power tube a little, but you pretty much have what you have. Try a EH or JJ 6V6GT (14 watt tube).

    disclaimer: I'm a noob and rusty to boot. been a year or so since I was messing with amp builds. So grain of salt should be taken as necessary.
     
  17. rolloman

    rolloman Tele-Holic

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    Ok thanks. I will try some of those things in the next couple days and let you know.
     
  18. printer2

    printer2 Poster Extraordinaire

    May 24, 2010
    Canada
    If I may throw a curve ball in to the mix, I would do a Blackface bass and treble amp rather than Tweed. More versatile with the tone controls. Also I would have a pull switch for the treble control and use it to parallel up a 2.2nF capacitor across the 250 pF cap. This should give a full midrange tweed sound with the treble control acting as a treble boost or cut control. It gives more control than a tone stack bypass switch.

    [​IMG]
     
  19. rolloman

    rolloman Tele-Holic

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    Hmmm. Wouldn't be very hard to modify it. Would be more versatile. Thanks.
     
  20. rolloman

    rolloman Tele-Holic

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    Duhhh. I put a output tranny for push-pull. Learned since that's not the really the correct thing to do. Ordered the correct Single Ended transformer Mojotone (Mojo0771) I can't wait to try that one.

    @printer2 I think in the schematic of the Blackface you posted, isn't the bottom of channel 1 grid stopper 68k supposed to connect right at the tube socket along with channel 2's grid stopper? Correct me if I am wrong. Otherwise the signal is shorted to ground once it makes it thru the 68k thru channel 2's jack switch if it is not being used for a 2nd guitar.
     
    Last edited: Feb 13, 2019
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