epluribus
Member
- Messages
- 9,170
Got the nomex ready to go, halon bottle in hand... 
This used to be a Kalamazoo Model II, and in some distant future will become a hard-wired FrankenZoo. Meantime, to prototype circuits, I started out with alligator clips, graduated to perf board and jumpers, then to perfboard with RF and noise control, and most recently to what you see below.
The point of this build is to make it easy to re-wire tons of different circuits within more or less "Champ" boundaries--single ended, small wattage, either cathode or fixed bias. In addition, the chassis is set up to run any combination of 9-pin and octal tubes throughout, (aka 6SJ7 to 6V6, EF86 to EL84, 12AX7...you get the idea) though obviously not all at once.
But the non-Champ intent is to be able to add cascading gain stages, various types and locations of tone stacks, use several types of rectifiers, add FX like trem and verb, and even remove and replace transformers--all without soldering a thing.
So now that you know the why of the build...I'd love to hear your input. I have several issues with the build thus far, some of which I briefly covered after the pics. But to avoid coloring your thinking or missing ideas that fall outside my box, I'll just let you look and form your own opinions at this point.
The grounding plan was to use a star-ground of sorts, with each bus connecting at the main ground bus and going to the center tap of the PT. The ground busses would include heat, Preamp B+, Power Amp B+, signal, chassis/shield, jacks/pots, and power cord/switch. (Hence the eight-terminal barrier strip.) However, an article at AX84 calls star-grounding into question, so remarks and theory are especially welcome on this point.
Heater lines would run pretty much all on the back of the chassis, with B+ being distributed under the circuit board on the front panel side of the chassis, and the power rail located above the PT on its own board. The two blue sub-chassis are sheet metal, btw.
Courtesy of the various terminal blocks, power can be connected or disconnected for heat, B+, rectifier supply voltage, and plate-to-OT feeds on power tubes. In addition, pre-wired tube sockets can be removed and replaced to accomodate different types of pinouts.
BTW, all of the barrier-strip terminal blocks are velcro'd and can be moved easily, same's true of the perfboards--all on velcro 1/2" standoffs.
The upshot is that not all of the tubes would be active at once, obviously, thinking about the Champ-style PT and all, but A/B'ing configurations would be relatively quick and painless with only the briefest of power-downs.
Anyhoo, this rig actually works, but it's never been put together in one neat hunk like this. That alone should be a major improvement over perf-boarding with the boards jumpered and laying on the workbench. Trouble is, when you pull it all together on one chassis, scads of layout issues arise, not all of which I'm familiar with. So I look forward to suggestions, links, questions, and maybe even a flaming arrow or two.
--Ray
Oh yeah, the rectifier--a Weber substitution box made just for this type of work...and of course the poor little OEM 6X4..
This used to be a Kalamazoo Model II, and in some distant future will become a hard-wired FrankenZoo. Meantime, to prototype circuits, I started out with alligator clips, graduated to perf board and jumpers, then to perfboard with RF and noise control, and most recently to what you see below.
The point of this build is to make it easy to re-wire tons of different circuits within more or less "Champ" boundaries--single ended, small wattage, either cathode or fixed bias. In addition, the chassis is set up to run any combination of 9-pin and octal tubes throughout, (aka 6SJ7 to 6V6, EF86 to EL84, 12AX7...you get the idea) though obviously not all at once.
But the non-Champ intent is to be able to add cascading gain stages, various types and locations of tone stacks, use several types of rectifiers, add FX like trem and verb, and even remove and replace transformers--all without soldering a thing.
So now that you know the why of the build...I'd love to hear your input. I have several issues with the build thus far, some of which I briefly covered after the pics. But to avoid coloring your thinking or missing ideas that fall outside my box, I'll just let you look and form your own opinions at this point.
The grounding plan was to use a star-ground of sorts, with each bus connecting at the main ground bus and going to the center tap of the PT. The ground busses would include heat, Preamp B+, Power Amp B+, signal, chassis/shield, jacks/pots, and power cord/switch. (Hence the eight-terminal barrier strip.) However, an article at AX84 calls star-grounding into question, so remarks and theory are especially welcome on this point.
Heater lines would run pretty much all on the back of the chassis, with B+ being distributed under the circuit board on the front panel side of the chassis, and the power rail located above the PT on its own board. The two blue sub-chassis are sheet metal, btw.
Courtesy of the various terminal blocks, power can be connected or disconnected for heat, B+, rectifier supply voltage, and plate-to-OT feeds on power tubes. In addition, pre-wired tube sockets can be removed and replaced to accomodate different types of pinouts.
BTW, all of the barrier-strip terminal blocks are velcro'd and can be moved easily, same's true of the perfboards--all on velcro 1/2" standoffs.
The upshot is that not all of the tubes would be active at once, obviously, thinking about the Champ-style PT and all, but A/B'ing configurations would be relatively quick and painless with only the briefest of power-downs.
Anyhoo, this rig actually works, but it's never been put together in one neat hunk like this. That alone should be a major improvement over perf-boarding with the boards jumpered and laying on the workbench. Trouble is, when you pull it all together on one chassis, scads of layout issues arise, not all of which I'm familiar with. So I look forward to suggestions, links, questions, and maybe even a flaming arrow or two.
--Ray
Oh yeah, the rectifier--a Weber substitution box made just for this type of work...and of course the poor little OEM 6X4..
