Amp builders... I could use your input

[_ej_]

I want to take on a new project. I recently cleaned up and got a Doberman Hi Octane build working and I want to try something a little more intense. I built a JCM800 clone at one point, it worked but had some faulty components and I had no luck tracking them down so I sold it.

I want to do another JCM, but I want it to be 2 channel. I want a clean/crunch sort of setup. Would it be difficult? From what I understand it could be as simple as adding a relay between the inputs and tweaking some components to equalize the volume. But what I really want is a setup like the Blackstar amps, full TMB on the crunch channel and just tone/volume on the clean. What would that entail? How feasible do you think it is? How good a clean channel could I get?

Any input would be a appreciated.

[clipless bumper]

check out a schematic for a 1974X (or original) and run it into a JCM800 power section.
It has two channels just as you described, and I am sure you could come up with a channel switching scheme - even an ABY pedal would do it, AND give you the option of running both channels together.


edit - actually, I'm not sure that they are fully independent channels through the preamp section - they may share some components along the way. But it is a good place to start looking for a simple two-channel circuit.

[Zozobra]

Buy this: http://www.valvewizard.co.uk/Book1.html

It has a section on switching in the 2nd edition (which I need to buy, I only have the 1st) and generally is a very useful and well written book on tube guitar amps.

Edit: as for how good a clean and crunch you can get then that depends on the preamp really. Look at the VH100R for example. It has an amazing chimey clean channel and all the gain you could want on the other. There are some good simple control preamps out there that you could take inspiration from. The latter version of the hot cat 30 has a very simple clean channel that only has a volume control for example:



There are some simple additions that could be made to that to make it more flexible using a few switches rather than adding a tone control (single pot controls are sort of sucky anyway),eg:
1) use a smaller value cathode bypass cap and then use a dpdt on-off-on to add caps in parallel to change the boost frequency range from hi mids (off), low mids and full range
2) same trick on the coupling cap to change the bass content
3) same trick on the bright cap on the volume pot

[_ej_]

Buy this: http://www.valvewizard.co.uk/Book1.html

It has a section on switching in the 2nd edition (which I need to buy, I only have the 1st) and generally is a very useful and well written book on tube guitar amps.

Edit: as for how good a clean and crunch you can get then that depends on the preamp really. Look at the VH100R for example. It has an amazing chimey clean channel and all the gain you could want on the other. There are some good simple control preamps out there that you could take inspiration from. The latter version of the hot cat 30 has a very simple clean channel that only has a volume control for example:



There are some simple additions that could be made to that to make it more flexible using a few switches rather than adding a tone control (single pot controls are sort of sucky anyway),eg:
1) use a smaller value cathode bypass cap and then use a dpdt on-off-on to add caps in parallel to change the boost frequency range from hi mids (off), low mids and full range
2) same trick on the coupling cap to change the bass content
3) same trick on the bright cap on the volume pot

I've actually been thinking of picking up that book! I guess I'll have to now.

[Zozobra]

You wont regret it. I bought it when the 1st edition came out and its been useful ever since.