Tube amp project started

JohnnyCreepy

JohnnyCreepy

Well-known member
Started a new topic on my WIP. Long story short I have gutted my old headache-inducing Peavey Valveking 212 to plain chassis. Circuit was same as in VK 100w Mk1 head. Plan is to use VKs original PT, aftermarket OT and maybe a choke I have around.

Be free to recommend, instruct etc on my plans. And as a disclaimer I do not mess with HV and take it seriously with proper precautions.

So far what I’ve gathered about transformers and what aiming circuitwise.

Transformers
  • Valveking PT, not sure about VA or exact winding voltages, but forum talk listed it approx 350V-24V-40V with no center tab (really?).
  • Hammond OT 1650T 120w, primaries for UL connection
The plan so far
  • 3 x 12AX7/ECC83 & 4 x 6L6GC
  • As simple and reliable amp as possible without transistors or relays. No FX loop. Gainy circuit would be preferable to get proper distortion without pedals too.
  • Circuit schematic simplified from Super Bass, Model T and Bassman (any suggestions?)
  • Turret/P2P build
  • Fixed bias with bias balance or pots for both halves
  • More farads on mains filtering than circuits mentioned have originally
Things to figure out
  • UL or pentode power stage? 6L6-family shines more with pentode, but UL is simpler and needs less parts.
  • Input stage; one or two inputs? If using only one halve for one input stage, the leftover halve could be used for more gain.
  • Input stage, one (or two gain) stages with cathode follower before TMB tone stack. Master vol before LTPI?
  • If only one input stage, maybe making a toggle switch for one gain stage would work for having the amp as more pedal friendly?
  • I have one 150mA 5H choke, on UL topology it isn’t necessary
I’m open for suggestions and opinions. Gonna draw whole thing on layout creator and still think about topology between different schematics before anything.

Gonna update this thread as journey goes on.
 
Thanks for reply @owlexifry

I looked into Fender schematics you posted and to be honest they just appear too similar to the amp I have. Maybe I need to ditch considering Bassman completely to avoid ending up with two too similar amps.

To easen up things, this is schematic of the amp I have now. Some values are changed, but I have ’em on handwritten notations on printed schematic back at home.

Simms-Watts AP100
IMG_6912.jpeg IMG_6913.jpeg

Taking back my words about Bassman, there’s 135UL version which output section could be used to do a mockup between Model T/Super Bass and Bassman 135.

Bassman 135 output stage
IMG_6909.jpeg

Model T schematic, Uraltone version
IMG_6911.jpeg
 
Did some chassis measuring yesterday for choosing right sized turret board. 300x40cm board with 30x2 lug stands will fit nicely. Still need to do some ahead planning figuring out power filtering section placement and doing a checkup on parts I already have on storage shelves.
 
IMG_6929.jpeg
First thing wired and had some difficulties getting thick solid wire through pin terminals. Gonna make it more tidy, trim wire ends and add next twisted pair leading to PI heaters before soldering.

Oh, and preamp circuit is going to be mix between 1gen model T and EL34worlds Plexi with hot switch. Power amp is from 135w UL bassman with few value changed for adapting UL ratio difference between 20% vs 43% screen grid tap.
 
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