Vintage Deco Champ! SUCCESS!!

Discussion in 'Shock Brother's DIY Amps' started by Jewellworks, May 9, 2021.

  1. Jewellworks

    Jewellworks Tele-Meister

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    This has taken me on quite a journey. some of you may recall, i started this last October.

    my original idea was to scratch build a Vintage style amp in a 1934 Art Deco Tombstone radio cabinet, using oddball tubes i had on hand from another tube amp i dismantled. my first idea was to use a Grid Leak Biased 6SJ7 pentode preamp with a Bone Ray tone stack to a very low gain 6J5 octal, to a vintage, big bottle 6L6.
    i couldn't get the grid leak bias to work. or at least i DID, but it was noisy and i didnt like it.
    changed to a different tube set. 2, 6SF5 tubes i discovered online somewhere, that were Octal versions of 1/2 of a 12AX7, with a mu of 100. so i thought id build an Octal version of a 5F1 Champ, with the Bone Ray tone stack. that worked, but again, it was noisy and sounded terrible. i tried a simpler tone stack based on a Gibson G10, with the treble coming from the cathode. still sounded awful. terrible un-musical distortion and hum and buzz and squeals...
    come to find out, the squeal was because i wasnt using shielded wire to the tone controls, and the hum and buzz was because my grounding scheme was a disaster, and my un-musical distortion was caused by a ton of blocking distortion, that was fixed by adding a small bypass cap on the 6L6 in parallel with the 22uf, so it would discharge quicker. i reworked all that, and changed to a single 6SL7 with the Bone Ray. that worked great, and the shielded wire made an enormous improvement. BUT, when i put the chassis in my Deco cabinet, it howled mike a mad monkey! turns out, a 6SL7 is microphonic! works great as a head, but since this was designed to be a combo, this wasnt going to work either. RRRGH! :mad:
    so i decided to completely start over. Chassis and everything, since my layout was all wrong, i had high voltage wires next to low and criss crosses and ... :eek: frgt-it.. just start over. so i started building up another chassis, keeping all the high voltage far away from the low, moving my transformers to one side, with a minimal amount of criss crossing. and i started a new design using 2, 12AX7s, with a cathode follower to a simpler Big Muff tone stack, then using the other half of the unused 12AX7 as a parallel input on a switch. a Super Champ. i added a built in attenuator, so i can crank it in the living room, yet turn it down so the wife can still watch TV in the bedroom.

    then i started working out of town and didnt touch it for the next 2 months.

    when i got back, i began to think that my earlier designs were probably good, now that i fixed everything with shielded wire, proper grounding and that small bypass cap. so i went back to the 2, 6SF5 version, replaced the Bone Ray with the Big Muff, and attenuator. drew it up, the next day i did a layout, and the next day i installed it all in the same old chassis. not the new one, as it wasnt ready yet.
    Lo and behold, it sounded great! and dead quiet! which is is amazing considering what an out of control noise machine this was at the beginning! :eek: i spent another week tweaking my Big Muff circuit till i got it sounding REALLY good. and for the last 2 days i kept trying to tweak it even more, only to go back to what i had already settled on. so i guess its time to stop.
    today, i put it all together for the first time. i put the chassis in the cabinet, added the lady jewel for the pilot light, and secured it all together. its a thrill to see and hear this amp after all this time. ive always dreamt about using an old radio cabinet as a guitar amp, and this is literally a dream come true. im all wiggly inside. :D
    ive learned a lot along the way. i had epiphany on the math and how to use Ohms Law to get the results im looking for, regarding the load lines and estimated voltages and current draw. i know the importance of a proper grounding scheme, how much stray RF/EF there is inside the chassis, the importance of keeping high and low voltages away from each other, and using shielded wire! i feel way better prepared for the next amp.
    ill be making a video soon, but here are pictures. too bad i can only post 10.

    Final Deco Schematic 5_3.jpg
    20210508_214321_1620533503056.jpg

    20210508_214505.jpg

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    20210509_192747_1620603576597.jpg

    20210509_192829_1620603640133.jpg

    20210509_193323_1620603938651.jpg

    id like to thank @Lowerleftcoast , @mrriggs , @andrewRneumann , @Nickfl and everyone else who chimed in with help and advice.
     
  2. Mongo Park

    Mongo Park Tele-Afflicted

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    Well done man, what’s a journey you have taken. With this build under your belt you learned enough to take on anything you want. I remember you started this a while back. It is nice to see people getting over that hump of copy/clone build into the world of making it go together from your own design, an amazing leap of learning
    I am liking the original look of the cab as well as the appropriate Art Deco touches. That big coke bottle tube really sets off the look from the back.
    What was the difference you found from the bone ray to big muff tone stack and why you settled on what you finished with.
     
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  3. Telekarster

    Telekarster Tele-Afflicted

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    Wow man.... what a cool way to repurpose that old radio cab! I'm a big fan of art deco. I really like this, and like the details you put on the chassis! Great job!
     
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  4. jondanger

    jondanger Poster Extraordinaire Silver Supporter

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    Beautiful work!
     
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  5. ThermionicScott

    ThermionicScott Poster Extraordinaire

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    That's great! Looks authentic, and the circuit isn't too "modern" either. Love the use of metal and big shouldered tubes. :cool:

    I was somewhat discouraging about the Big Muff tone circuit in your other thread. How are you liking it now?
     
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  6. printer2

    printer2 Poster Extraordinaire

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    Nice work. Priceless journey.
     
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  7. Jewellworks

    Jewellworks Tele-Meister

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    the difference between the Bone Ray and the Big Muff is the Big Muff has permanently scooped Mids, whereas the Bone Ray you can adjust the mid scoop down or up. but my biggest reason for going with the Big Muff was its 1 knob, and i wanted the other knob to be the 8 ohm attenuator so i could turn it down. i later discovered you can do what with a simple 10% switch posted by @robrob , and ill probably do that on my next SE Build, and stick with the Bone Ray. but this cabinet only has 3 holes for knobs, so i did that.
    ill be making a video soon. i just did a little show-n-tell at work, and one of my co-workers was very surprised by how good it sounds. he was expecting something "ok" from this old cabinet, but this blew him away.

    thank you. yeah, no one decorates their chassis, which is understandable. more often than not, its hidden away in a box. i thought this was at least half-exposed, and i liked the idea of someone far in the future coming across this and discovering the artwork. its a piece of 30s Art Nouveau by an artist named Mucha. my "new and improved" chassis (that i never used) had a different piece of artwork on it by John Held Jr. -an Art Deco cartoonist. his work is incredible for cartoon drawings. im still considering building that up and moving all this over... i love Art Deco too. and this lil amp has been a dream come true.

    thank you everyone. i hate to brag, but sometime you gotta. i especially feel like ive learned so much from this amp project. there were times it was so frustrating i was ready to give up and build another champ clone. in a way, thats what this is, but not quite... and getting here was an experience.
    now im seriously considering taking on a Dumble. Dumble-lite. D'Lite. 2 EL84s for about 18 watts...
     
  8. Jewellworks

    Jewellworks Tele-Meister

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    s'more pictures

    20210509_192842_1620603669561.jpg
    Big Muff curve.jpg
    Tube Chart.jpg
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    20210509_193119.jpg

    BTW, im running right at 19W on the big 6L6, which is its Max.
    its got a surprisingly full sound with just a 6" speaker. i had to make a speaker baffle to go from the original 5" to a 6". i used the speaker pegs (seen on the front) to secure the baffle, and just screwed the speaker to the baffle. i also had to rubber cement the speaker cloth to the wooden cutouts on the front, as the speaker was moving so much air, it was causing it to vibrate and buzz against the cutouts.
    video coming soon
     
    Last edited: May 10, 2021
  9. jays0n

    jays0n Tele-Holic

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    Wow is right! What a great living room amp that is.

    Beautiful. Good job man!

    j
     
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  10. printer2

    printer2 Poster Extraordinaire

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    I have a 30's radio and some 40's waiting to be redone. The 30's has a 6" field coil speaker that I can reduce the voltage to the winding and act as an attenuator. I also have a floor standing unit that has Art Deco styling in the design.
     
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  11. NTC

    NTC Tele-Holic

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    Congratulations, Jewellworks. It looks great. I am glad this worked out in the end. I know I contributed to your misery along the way.

    Hopefully you can post some sound clips eventually.
     
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  12. Cali Dude

    Cali Dude Tele-Afflicted

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    That's amazingly cool.
     
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  13. Jewellworks

    Jewellworks Tele-Meister

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