Preamp Musings (group project)

[Luthierwnc]

Hi All,

I've been fighting myself on my next build whether to try a high-plate or low-plate head. As I incorporated both necessary and optional hardware, I started thinking about changing the packaging to have the best of all worlds.

Right now I'm toying with the idea of building a low-plate classic for the head and building a preamp that has a high-plate V1 driving either a high-plate non-HRM or HRM. The box would also include the D'lator. Fenderbluesman and I have swapped a couple emails on the notion of grafting his simplified Minimax into the loop Send and Return.

Attached is a rough block diagram of my thinking at this point. The unit has 4 tubes, four relays and a three button foot-switch. The relays are for the PAB (not shown), two for the OD selector and one for whether the preamp feed from the amp or the separate preamp goes to the loop.

The input could either be an A/B box off the guitar or just jumpered between the amp and preamp with both on all the time. I wasn't planning to have a high-plate clean option just because I much prefer the low-plate cleans. Both of the ODs would have separate masters although the loop Return control would be the last word in volume.

The reason I'm throwing this up now is for comments and to see if anybody else is working on a hair-brained winter project. As I see it, the power amp is the heavy, expensive part of the deal -- the offensive line of the system. The preamps are the skill players. These are all the usual parts, just arranged differently.

Fire away, thanks, Skip

[Structo]

I've been thinking along the same lines as well.
But for now I would build the minimix in a separate enclosure or maybe on a pcb and patch it into my D'lator.

This is how I wired the Bypass Switch on my loop.

[Luthierwnc]

I made the PCB for my current Dumbleator a couple days ago. Without the transformers and relays it fit luxuriantly on my last scrap of copper-clad. By eyeball it is 2.5x3.25". The chassis is a full 10" deep so it will rest easily behind the Send/Return jacks. The donor is the Cisco router mentioned in an earlier thread and it already has -12v/+12v taps for the ICs. The only other thing I have to do is put the kill switch on the panel -- probably in place of the gain pot which I leave dimed anyway.

The next actual project is the 100w head. I'm just building it with the possibility that I can scale in the preamp project if I want. Stuff like a convenience jack with a really short cord, inputs on the same side of the panel ... thinking ahead.

Right now I am designing around a low-plate V1 and a high-plate V2 -- but I'll get extra resistors and caps if they aren't already in the parts drawer.

sh