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Harvard Build Idea - Your Thoughts

Discussion in 'Amp Central Station' started by gabasa, Nov 16, 2020.

  1. gabasa

    gabasa Tele-Meister

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    Hey All,

    I'm thinking of building a tweed Harvard style amp, but my problem is the eternal one with Harvards: nobody seems to make a chassis nor a kit. I don't want to get a tweed Princeton chassis and start punching holes in it so I had this idea to build a 5E3 with a few changes:
    • Change the first coupling caps to 0.02 uf
    • Omit the bypass cap from V2
    • Add in a 56k negative feedback resistor
    • Build it as a 1x10
    This way, it'll be a two-channel Harvard that's cathode-biased. It won't be a Harvard. Rather, it'll be a Harvard-voiced 5E3.

    You think this is worth pursuing? I feel like it'll sound great.
     
    ping-ping-clicka likes this.
  2. jhundt

    jhundt Doctor of Teleocity

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    You could build a 5f11 Vibrolux, which is virtually identical to a 5f10 Harvard, with a bias-vary vibrato (aka tremelo) added.
     
    scook, kingofdogs1950, Nickfl and 3 others like this.
  3. ping-ping-clicka

    ping-ping-clicka Friend of Leo's Ad Free Member

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    electronics circuitry , I know nothing about .
    I do appreciate what it is that you are trying to do, your thinking is inspiring. Thank you.
    I know that I like the sound of older fender tube amps.
     
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  4. Dacious

    Dacious Poster Extraordinaire

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    I've seen 5F2 chassis kits, I'm sure. A Harvard's just a Vibrolux with no trem isn't it?

    I think the
    +1. Mojo has a chassis kit .
     
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  5. Kevin Wolfe

    Kevin Wolfe Tele-Meister

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    Indeed, go the 5f11 route. Turn down the trem and you’ve got a Harvard. Even with the changes you mention, it will still be a fixed bias amp, not a re-voiced 5e3. A 5f10/11 and a 5e3 are two totally different animals.

    As a bonus they make a wonderful acoustic guitar amp with just a wee touch of tremolo.
     
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  6. zook

    zook Friend of Leo's

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    No, The Vibrolux is a Harvard with Tremolo :)
     
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  7. gabasa

    gabasa Tele-Meister

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    No, Tremolo is a Vibrolux without the Harvard! :)
     
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  8. schmee

    schmee Doctor of Teleocity

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    Just build the Harvard in a 5E3 chassis, they are cheap. $40?. Been there, done that.
     
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  9. printer2

    printer2 Poster Extraordinaire

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    Build a volume-tone tone one channel, volume treble bass on the other, drill a hole for the bass control, mix with 220k resistors.
     
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  10. jsnwhite619

    jsnwhite619 Friend of Leo's

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    It will probably sound great, but not necessarily like a Harvard. Even with caps change & NFB, a 5e3 won't sound like a Harvard.

    If you really want a Harvard but stuck using a 5e3 chassis I would
    • Build the stock fixed bias Harvard circuit
    • Use the Bright 1 & 2 so that the vol & tone knobs are beside each other
    • Use the Normal 1 & 2 inputs for bypass cap switch, maybe a cathode resistor option switch for V1 - something to take up the holes.
    • And maybe use shielded cable to run a NFB pot as the Normal channel Volume knob. A 50k pot would give a pretty good range in addition to the stock value. Or a lower than stock if you wanted since you have the adj. pot. Either way, you can go from snappy clean to loose & rowdy with the NFB pot.
    • Follow the vol/tone wiring for the Harvard.
    Fixed bias, NFB, smaller cap values, different input wiring on the pots -- all add up to a Harvard being different than a 5e3. Stick with an 8k primary OT if you want the vintage feel & tone.
     
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  11. David Barnett

    David Barnett Doctor of Teleocity

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    It's only two holes - a third input jack and a 7-pin tube socket.

    And I dare say the third input is superfluous anyway. The 6AT6 is the key to Harvard-ness. That and a 10" in a Princeton-sized cabinet.
     
  12. FiddlinJim

    FiddlinJim Tele-Holic

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    ... and a second output tube socket... I also drilled a hole for the bias pot. I did that with a 5F2a chassis. My only regret is that I didn’t get the three inputs to line up as well as I wanted. Sounds great.

    FA7BDED6-D1E9-4F52-8367-DF4E50087C40.jpeg
     
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  13. kingofdogs1950

    kingofdogs1950 Tele-Afflicted

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    +1

    M
     
  14. David Barnett

    David Barnett Doctor of Teleocity

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    Oh yeah...
     
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