Basic P-P Guitar Amp

Discussion in 'Shock Brother's DIY Amps' started by printer2, Oct 15, 2019.

  1. printer2

    printer2 Poster Extraordinaire

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    A low power 5E3 made its way back home in need of repairs. I built it as a home friendly volume machine but the user has been using it when he did not want to drag his Peavey classic 30 out to house concerts. It is a little under powered for the application. So just for kicks I am going to build an amp that is a hair bigger in size but rather than using 6AK6's for the output tubes putting out 2-4W I am thinking of using 6V6's or maybe EL84's. And instead of a 10" speaker out of a 60's console stereo a 10" Veteran Warehouse Guitar Speaker should take the added power.

    Not one to turn up my nose to silicon devices, the rectifier will be solid state, the phase inverter will be Mosfet powered as well as the source follower before the tone stack. So for now the plan is one half of a 12AX7, the source follower, tone stack, the other half of the 12AX7, fixed biased Mosfet for the Cathodyne PI, then the 6V6's. So vacuum tubes where gain is needed, Mosfets where using a tube is not doing all that much soundwise.

    Here is where it gets messy. I had a pair of transformers out of a console radio that used 6AQ5's. I decided to use a stainless steel chassis I built at work, I normally do not like SS as it is hard to drill and cut. No longer being one that is gainfully employed, I only have the tools I had at home to machine the chassis to hold the parts. I decided the fastest way to do the power transformer cutout was to dimple the SS using a deck screw and a hammer. Once done I used a chisel and cut the section out.

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    Some hammer and file work managed to do an acceptable job of getting a home for the transformer. Then I decided to measure the winding resistance and voltage in order to decide how to proceed next. I ended up confused as the windings had hardly any resistance. Determined which should be the line, I hooked it up and measured the voltage. On the center tapped winding I got 20V - 20V and the other winding about a volt. What the heck? The only think I could figure out is I mistook this for the 6AQ5 power transformer, they both had a copper flux winding on one side of the core. Can't seem to find the other transformers, maybe my mind is playing tricks on me. Would be funny to find them one day. I got too much junk.

    So scrounge through the transformers and chassis I have laying around, found one small enough that it will fit on the chassis and will not weigh too much. It is larger than the other transformer, after weighing options I decided to use one of the holes in the chassis and open up the cutout for the new transformer and drill two more holes. After some more file work I had it sitting in the chassis. Will not win a beauty contest but it is functional. While I was at it I cut a fuse holder hole and one for the power cord connector. And I only broke one drill bit.

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    Last edited: Oct 15, 2019
  2. Deeve

    Deeve Friend of Leo's Silver Supporter

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    improvise
    adapt
    overcome

    well done, @printer2

    Peace - Deeve
     
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  3. printer2

    printer2 Poster Extraordinaire

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    Story of my life.

    Something along the lines of this.

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  4. kbold

    kbold Tele-Afflicted Silver Supporter

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    Wow - that's some nibbling tool!
     
  5. printer2

    printer2 Poster Extraordinaire

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    Used the chisel at an angle to break the metal between a few dimples at a time. Had it supported by a 2 x 4 in behind, took no time at all. I missed a capacitor on the PI side of the master volume, I'll get everything worked out for the final schematic. I did a dry fit in the cabinet to see where things make sense to position them.

    [​IMG]

    Decided on EL84's, I have a few and only a pair of 6V6's.
     
    Last edited: Oct 16, 2019
  6. printer2

    printer2 Poster Extraordinaire

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    Got the holes for the tube sockets and the pots done. Sacrificed a couple of more drill bits. I like working with aluminum better. Made the front baffle for the speaker also.

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  7. printer2

    printer2 Poster Extraordinaire

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    My current pursuit bumping aside the amp project, a bolt together trailer.


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    Unbolted the major bits.

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    Welded up the channel to each other and filled in the Swiss cheese cutouts in the frame. I still have to do the second section's cutouts. How I amuse myself.
     
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  8. printer2

    printer2 Poster Extraordinaire

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    The trailer is on hold till spring, skinned and insulated the sides, we will see what I do with it from then.

    [​IMG]

    But back to the amp. The other 6V6 p-p radio I picked up started a itch I need to scratch. Would have started back on the amp but, (a little bit of embarrassment) I could not find the chassis. Over the last day or so I have been wondering if I should add a preamp tube and make a 18 Watt TMB. I would have drilled the holes differently if I knew I was going to use another tube, I think I can squeeze one in to miss the magnet if I offset it. Been listening to vids, came across this one, it was interesting but I think he could have EQ'd the 18 Watt better.



    Still trying to decide.
     
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