Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DummyLoad on February 05, 2017, 01:41:40 am
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fun amp. sounds really nice and is quiet. loves single coils and growls well with humbuckers. love the EL34's married to a classic fender preamp. i us3ed marshall PT 7 OT with fender choke and reverb driver OT. planning on installing in a marshall style combo cabinet with 2x12 celestion greenbacks or alnico gold.
https://www.dropbox.com/sh/1ax5fslgzorieo9/AADUo1WIwnRFV3ADC0jB17rGa?dl=0 (https://www.dropbox.com/sh/1ax5fslgzorieo9/AADUo1WIwnRFV3ADC0jB17rGa?dl=0)
--pete
EDIT: add schematic. ho-hum it's just a redux.
EDIT: add schematic in .SCH format for library.
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Pete,
Wow! Nice job on this amp! THANKS for sharing the schematic and photos. Looks great.
IF you have the SCH version, could you please include it in the SCH Library of schematics. I think this is one that others would be interested in
building.
With respect, Tubenit
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Very Nice Amp !! :thumbsup: :thumbsup: :thumbsup:
BTW I like the bias PS arrangement, no problem if the wiper connection fails, good :bravo1:
Franco
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Good lookin' amp! Very clean layout.
Several people have built that reverb circuit lately and have had hum problems with the recovery circuit. How is yours?
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Wow! Nice job on this amp! THANKS for sharing the schematic and photos. Looks great. IF you have the SCH version, could you please include it in the SCH Library of schematics. I think this is one that others would be interested in building.
thanks tubenit! i do have the .SCH format and i'll upload it shortly. you can add it to the library if you wish.
Very Nice Amp !! :thumbsup: :thumbsup: :thumbsup:
BTW I like the bias PS arrangement, no problem if the wiper connection fails, good
thanks franco! yes, i like the bias PS to not connect off the wiper.
Good lookin' amp! Very clean layout.
Several people have built that reverb circuit lately and have had hum problems with the recovery circuit. How is yours?
thanks steve! the reverb path is very quiet as built.
thanks again all for the kind words. i started concept on the amp around september-october of 2015. i just finished it last friday.
--pete
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Nice work!
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"Quiet reverb", gotta like that. My last AB763 build was rather noisy. Any grounding tips? Awesome build.
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I always love your work. I have been partial to eyelets lately.
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PT & ed, thanks! and ed, yes i'm partial to eyelets - much easier construction.
clyde, follow these guidelines:
- preamp circuits get one grounding point near the input jack or filter cap that powers the first stage if it's near the input jack. use isolated input jacks if you can, if not the jack is the ground point for the preamp circuits.
- heater CT, if there is one, get's it's own ground, and if it's a virtual tap as well.
- power tubes supplies and and bias supply, if there is one, get their own ground and if there is a HV CT it goes there as well. IF you have a multi section cap that feeds the power stage, and one of the sections feeds the phase inverter circuits, then tie the phase inverter ground back to the power amp ground point.
- tie output tube cathodes and OT secondary common to the their own ground point.
- use low noise resistors for the input (1st stage) grid leaks(s).
- use low noise gid leak resistors for reverb driver and recovery stage and tie them to separate grounds near or on the jacks to/from the reverb tank.
- AC input jack gets it's own ground point.
--pete
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almost done. waiting for mesh for cooling slot & the baffle is not the one i'm going to keep, so not painted black. cabinet maker made the baffle out of 3/8 ply: i wanted 1/2" baltic birch.
--pete
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Forgot to mention we don't need no stinking master volume. They are always just in the way. :laugh:
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Dude...sweet
Love seein the wood on the cab....much sexier than tolex :thumbsup:
Please stay on this side of 'the wall'
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That is some fine work.
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thanks for the kind words guys!
SG - i have one of your most excellent cabinets in the next build. hope to be finishing the chassis on that one this weekend.
--pete
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love the EL34's married to a classic fender preamp.
Nice Pete! I designed something similar in that a couple fender-y preamp channels but into EL84s for purpletele about the same time? No verb as it had to fit into a 1974x chassis and cab replacing the existing circuit. Also included a switched presence for no NFB to go with a paralleled tweed-ish channel for that raw tweedy type goodness and a twin stage ab763-ish channel along with some presence nfb. Purpletele reported lots of good stuff about the outcome.
But if there was room it would be great to have the verb, the tremolo not so important. My personal plan is to build the same preamp sections but into an EL34 output section similar to yours? I'm sure it would sound terrific! This gives me more inspiration as soon as I can get some personal build time of my own? Perhaps by next month but already some more things are lining up along with a gig or two...must prioritize and keep multitasking!
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Hey, I heard my name mentioned.
I am very pleased with Joe's Hybrid, it is quite a unique amp. It is perfect for what I wanted it to be which was the cool studio/shop amp.
That was the third circuit that I built for that rig. I am getting some magic and mojo thanks to some guidance from Joe and many others.
The speaker cabinet has a Gold and a Cream in it. It's a bit overkill but it sounds glorious.
Brian V