Crate Stealth GT50 voicing mod?

[rockon1]

Thinking of trying to tame my GT50's metal voicing a bit-perhaps make it switchable. Its very single minded and has a very strong treble/upper mids emphasis. Great for metal but not easily tweaked for anything else. Does anybody know/think by lowering R11 I might mellow it a bit? Am I correct in thinking this is the slope resistor? Thoughts?, thanks Bob

http://music-electronics-forum.com/a...schematics.pdf

[Phostenix]

It looks to me that IC1A is where most of the tone shaping action is on the gain channels.

[rockon1]

Thanks. Im somewhat of a noob with this stuff. I can replace parts and did a bunch of mods to my V32 with good success. Like in my trade(transmission rebuiler) youve got " parts replacers" and then you have "rebuilders". The difference being that a good rebuilder knows hows things work. With this stuff,unfortunately Im pretty much a "parts replacer". I do know to drain the caps,check with a meter for voltage and I have a desoldering gun and Im not afraid to use it! Any suggestions? bob

[Phostenix]

I'm hoping the more experienced modders will chime in.

[rockon1]

Me too! It would be nice to be able to have a switchable type mod. the stock voicing is quite aggressive. A switchable more vintage voicing would be awesome. Bob

[JerryP]

I've never modded one of those, too much solid state stuff for me. Here's a few things I might try if I had one here.
Change C70 from a .0022uf cap to a .0047uf or .022uf 400V cap
Change R40 from a 475 ohm resistor to a 1K-2.7K 1/2 watt resistor
Change R86 from 100K to 47K

Change the tone circuit to be more like a Marshall:
R42 33K
C21 & C22 .022uf

You might try just changing R42 to a 68K first and see what that does.

If you need more bottom end you could add a depth mod/resonance control.

Never tried any of these, but if I had to mod one these are a few changes I would try.
Jerry

[rockon1]

Originally Posted by JerryP

I've never modded one of those, too much solid state stuff for me. Here's a few things I might try if I had one here.
Change C70 from a .0022uf cap to a .0047uf or .022uf 400V cap
Change R40 from a 475 ohm resistor to a 1K-2.7K 1/2 watt resistor
Change R86 from 100K to 47K

Change the tone circuit to be more like a Marshall:
R42 33K
C21 & C22 .022uf

You might try just changing R42 to a 68K first and see what that does.

If you need more bottom end you could add a depth mod/resonance control.

Never tried any of these, but if I had to mod one these are a few changes I would try.
Jerry

Ok I "piggybacked" a 100K on the R42 for a 50K value. Seemed to tone it down a bit. I swapped the speaker and so far just with the R42 change and a different speaker I seem to be able to get into more of a classic rock territory and still do its signature 80's Ratt tone-nice.....

On my V32 the components are soldered all the way thru the board-seems much nicer actually than just soldered on the bottom like this amp is. I'll have to pull the board to try anything else...... Like you said the amp has a lot of SS stuff in it! Still its never murky at least! Pretty tough sounding in stock form but very single minded. I bet you could make this amp into a more versatile monster!

Question-The C21 and C22 caps are big poly 400V. Do I need to replace them with the same type? Thanks much! Bob

[Guitarist]

Yes, high voltage caps are required. Also try a couple of old 12au7 in V2 and V3, then tell us how it sounds...)

[rockon1]

Originally Posted by Guitarist

Yes, high voltage caps are required. Also try a couple of old 12au7 in V2 and V3, then tell us how it sounds...)

Thanks. Ive got plenty old old stock 12AU7's.... Usually to much of a gain loss for my tastes. I may try the caps. Brought it to pratice last monday and with my p100 equiped Les Paul Special it sounded pretty good for classic rock tones. Bob