Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 2stepz on July 04, 2022, 05:06:57 pm
-
I am building an amp that can accept any 1 pre-amp tube, any 1 power tube and any 1 rectafier tube. It will not be in a normal enclosure, it will be an 'open-face' electrical shock hazard. Where different tone stacks can be dropped in with aligaor clips. The main problem so far is coming up with a way to power these various tubes. It looks like using 3 variable power supplies (plate, heater, bias) would be agood solution. I was also looking at london powers PSU-COMP/SV1 but think having power supplies for other uses would be a better use of money. Im not an electrical engineer (or all that great with amps) so I was hoping someone might have an elagent solution to this problem. Thanks!
-
Is your purpose with it to simply try out different tone stacks?
The number of gain stages, whether there is a cathode follower, where the tone stack is inserted in the topology, type of power tubes, speaker choice, etc.........
all impact the tone.
I think the single ended 3 tube approach won't inform you much at all about tone stacks and how they might sound in another amp?
Let me give an example, one of my favorite tone stacks is the James tone stack which I think sounds great in a 5E3, Carolina Blues Special, Dano Centurian 275, etc...... And yet I have never had it sound "good" in a Marshall topology behind a cathode follower.
Are you familiar with the Duncan Tone Stack calculator? TSC (duncanamps.com) (http://www.duncanamps.com/tsc/)
With respect, Tubenit
-
an amp that can accept any 1 pre-amp tube, any 1 power tube and any 1 rectafier tube.
For the ‘any 1 preamp tube’, are you only considering dual triodes in Noval bases with the same pin-out? (Or do you also want to try subbing in different octal base preamp tubes where the octals have the same pin-out?). What about small signal pentodes (in noval or octal bases)? They have different pin-outs. But wait, there’s more - what about dual triodes wired as cascodes? Or SRPP? Or preamp tubes with triode and pentode in the same envelope? These different possibilities will all require differently wired sockets connected to different circuitry.
Same for the output tube. Do you want noval or octal base types? Or either? Or both? Lower power or higher power? Tetrodes and/or pentodes?, or output triodes? Tubes with triodes and outputs pentodes in the same envelope? Different output tubes may want different output transformers (to ensure optimal loads) and different B+s, and different ways of biasing, to get the most out of each tube type.
For either preamp tubes or output tubes, different types can also have different heater requirements.
For the rectifier, do you want octal or noval base? 5V filament or 6.3V filament? Low power or high power?
You might want to think about your goal a bit more and whittle down the options. (Or not?)
-
Just build a breadboard.
-
So I was hoping to do something like this. Choose a pickup (cause i make those too) and tubes and desired amp characteristics (touch sensitive, early breakup, style of music its good for, etc). Say a 50/60's strat pick up, a KT66 power tube, a 12AY7 preamp tube, with early onset Output distortion that can be controlled by picking harder, woody, raw, bell-like chime that sparkles. Then I plug the tubes into this prototyping platform amp and get the heaters, plate, screen, grid voltages/currents dialed in. Then I would go to the signal chain and try out differnet tone stacks. Then say I decide the 12AY7 isn't what I want then I can replace it with a 6SJ7 (I intend to have all sockets to accomidate all pin-outs).
I was hoping to avoid buying a bunch of transforners and parts for experimenting with new. To make something where I could try WIDE variety of ideas out and work out my own original amp schematics.
-
An SE amp will not SAG, so, no problem if the current disposable at the PT Is high, to solve the problem about a correct B+, use a High B+ PT with a VVR, this way you are not obliged to use a multy tap PT
BTW, if your interest Is about SE amps, you can avoid the use of a tube rectifier ed use SS diodes, as told, there is no SAG on SE amps
Franco