A blog of my tube amp design and modification work. Primarily my own builds, but occasionally I feature work I've done on others' amps (with their permission.)

Tuesday, January 6, 2015

The Matange!

So, I've been planning my next project lately. This year, I'm going to build an Orange/Matamp-inspired head, starting with a cheap donor. Still not going to make the plunge into woodwork/metalwork as long as I can avoid it. Someday I might build a high-gain monstrosity, but I'm not a big fan of preamp distortion, so I don't have much motivation.
Fortunately, I have the relevant schematics on my phone!
Now, my thoughts:
Fixed bias quad of pentodes. Sure, though it pains me to turn away from my beloved beam tetrodes, but I'll give these screen-current-sucking babies a try.
Cathodyne phase inverter. Awesome; love it. It's going to need a big grid stopper, and I'll put big grid stoppers on the power tubes too. Definitely going with AC coupling; DC coupling is too big of a pain for little benefit with cathodynes. What can I say, I like em center-biased.
James tone stack. Absolutely. I'll probably add, or at least try, a mid shift control so I can move the notch around.
The "FAC" switchable coupling cap bass control. This is great; I've used it for a bass control after a pentode. The series-connected version does pop; Matchless uses a parallel "one at a time" version with large resistors in parallel to prevent this. Since I've tried the series version, I'll probably try Matchless's take on the Matamp original.
The Matamp drive control. This kind of seems silly. Switchable bright cap, eh, why not. Gotta keep some British in there! I don't see the point in padding down the gain when there are only three gain stages. Also that Orange inductor-based boost control... I'm skeptical. I'm also worried about noise. It's a tricky situation. I might try variable cathode bypassing instead, possibly tied to a treble cut.
As for the order of the tone controls, I think I prefer having the FAC after the first gain stage and the James after the second. Always good to cut bass early and treble late, though there are so few stages...
It should be an interesting project. If there's space for a third preamp tube, I may use a 6GH8 triode/pentode to add reverb. I'll use the pentode to drive the tank and half of a 12AX7 for the recovery stage, and then I can use that medium-mu triode in the 6GH8 for the phase inverter! Mmmmm, sweet, sweet low-ra cathodynes...
More when I actually write up a schematic.

1 comment:

  1. I'm not familiar with the switchable coupling capacitor bass control, although it's pretty obvious. I've just never seen it used. I'll be looking forward to more.

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