Crate Gxt-100 looking for any mods

[screamersusa]

Since a Boogie mark2, Engl savage, or even carvin is out of the question.. .
I got a Gxt100 dirt cheap in mint condition.
Could someone point me to any mods for this thing.
I also have a spare tube socket n parts to graft a first stage tube buffer
before the input and maybe an engl stage two after the drive tube.

I am going to add a switch to disable the direct to mix line so the fx mix
becomes a loop.
I already changed the tubes and will probably close the back once I figure
out how much airflow the amp needs.
Thanks in advance

[J M Fahey]

Mod for the sake of modding or you have a specific sound in mind?

[soundguruman]

Since a Boogie mark2, Engl savage, or even carvin is out of the question.. .
I got a Gxt100 dirt cheap in mint condition.
Could someone point me to any mods for this thing.
I also have a spare tube socket n parts to graft a first stage tube buffer
before the input and maybe an engl stage two after the drive tube.

I am going to add a switch to disable the direct to mix line so the fx mix
becomes a loop.
I already changed the tubes and will probably close the back once I figure
out how much airflow the amp needs.
Thanks in advance

This is my favorite mod for Crate amps:

[screamersusa]

Ive owned much better and working with what ive got.

This is my favorite mod for Crate amps:
[ATTACH=CONFIG]26702[/ATTACH]

Ive owned two professionally hot rodded marshalls, a dual rec, upgraded peavey classic,
Soho, multiple fender blackfaces and my favorite Carvin x100b (Robert Fripps personal amp) and another x100b and x60, along with a studio
to play them in at working volume. Life has taken them and I wont be getting any of them back. May you never have that problem at my age.
I bought this cheap because it had real tubes and a hv supply in it.

Moving on..
It's an opamp based preamp. A jet or tube adds a little glass or sheen to it. The fx mix is not too usefull for adding an eq. I would like to get something a little more Mark2c drive and or Engl savage out of the drive channels. I notice there have been a lot of PT issues. Wondering if I should consider using my about to be sold
Randall RG75 closed back as the power engine and disabling the Crate's poweramp.
If nothing else, adding a bright cap to od1, or a dark cap to od2 might be usefull.
I'm trying to get OUT of my GNX3000 for gain tones.

I'd like to wind up with:
Ch1 Mesa/carvin glass clean, (added toggle for marshall broken glass breakup)
One od, middle gain boogie mark 2 style
Other OD Engl savage style.
Clear and articulate not a midrangey piercing buzzsaw. Warm and creamy overdrive
that I can dirty up with a pedal if I need to.

[screamersusa]

Looking at both the engl530 and mark2c I noticed something they both do with one tube.
Mesa at unknown voltage, 220k /1nf on plate, 3k3 cathode resistor, (also a bright sw w 220n on the cathode)
Engl at 320v (i think the savage is 400+) 330k /1nf on plate, 3.3k/10uf on cathode.
Would changing V1 (the overdrive tube) to these help? its currently 320v, 221k on plate and 2.2k/22uf on cathode.
it looks like i can graft a boogie mark 2 eq (have a trimpot version built already) in between the od opamp and the tube
preset for the typical metal boogie settings.
Since the boogie sound is in the post eq, i wonder if the mid boost could be reconfigured into a mid cut at about 700?
I'm thinking that if I could get the overdrives somewhere between a mark2 and engl I'd be quite a happy camper.
I have my Engl savage and Mesa 2c modeler settings quite similar. I like the compression on the engl and find that
on the modeler, I can get over to a marshall grind with my Box of rock or a fender bluesy with the abazache through
a super clean channel. Tossing a jfet or tube infront of or replacing the first op amp should sound pretty nice as my
proir testing has shown. That first stage seems the most critical.

[screamersusa]

If anybody's watching, the first mod set went well.
The easiest quick usefull mod was to pull r79. This makes the effects return a temp master volume.
Next I adjusted V1b (clean+od) from 220k/2.2k to 150k/1.5k. I like the cleans alot more now.
Then I adjusted V1a (od) from 221k/2.2k to 330k/3.3k. The overdrives now have the feel I was looking for.
I can set an early Benatar distortion and add accent runs without needing a compressor (thats the engl part I wanted)
I can set the second for a more brutal drop d overdrive and still have articulation.
The last thing I did was change the clean treble from 100p to 200p, closer to a mark2.

Next up for suggestions is tweaking the od channels:
There appears to be a 221k/.001uf treble peaker between the tube stages. I was thinking of reusing the .001 as the snubber cap
as I dont have another one and I would think I dont need that treble peaker anymore since I'm not overdriving V1b as hard as original.
I am planning on dropping V1a's 22uf cap down to a 10uf.
Next I have to figure out how best to eq the predistortion low end. Either lower the .1 caps down to 22n or insert a Mark2c eq between the OD opamp
and the tube stage with either a Bc549 buffer or Tlo71 for make up gain. What do you guys think would be best?
I'm going to be adding some prebuilt RDL modules in the master section to facilitate: Balanced line out, headphone driver, slave amp out.
I really do not like the reverb at all so I'm considering either a second effects send or converting it to a footswitchable mosfet overdrive for the
clean channel for a slightly gritty tone.
1/2 of IC3 is unused so it will become the new master volume buffer to the poweramp.

I've been building a ton of fet and opamp pedals and none of them could nail the feel I was looking for.
An hour of modding this thing and there it is.
To the Crate bashers: This thing is not typical Crate. Well built, wima caps, decent parts. I was quite surprised.

[screamersusa]

After settling on a couple of mods and playing with the amp for awhile sans speaker and poweramp,
I was surprised to find a mode I don't need to add. I think this thing will work quite well to fit my style with a
few adjustments and a major reworking of the final post preamp stages. Mods I need advice on are as follows:

My Personal Style I'm making this amp fit: Clean/light drive through one effects loop/ clean, sparkle, comp,chorus, gillmore echos etc
Light rock to Neil Geraldoesque OD and Engl Savage OD through second effects loop.
CLEAN BOOST. (I put V2 back to its original resistors)
The clean boost control is tied to the od1/2 switch. I need to split the clean boost away from the od1/2 sw to it's
own switch and reuse the reverbs control line instead. This will allow me to go from od1 rock mode to slight overdrive clean with
one button instead of 2. I use the light od mode more than super clean. I'm guessing its around q26 so i could pull r59 and r70 (reverb)
and move the reverb control over to the clean boost.
I would also like to be able to adjust the gain in boost mode with a recessed trimpot.

OVERDRIVES. I bumped the V1 resistors to 330k/3.3k and like it very much. I also dropped the last .1 to a .022 pre tube.
I'll have to make up the missing low end at the end and have a few bi-polar supply drop in eq options for that including some
dual sweep mid Soundtracs Solo eq sections (Seriously sweet eqs!).
I do notice a gain and eq difference between od 1 and 2. I'm guessing that it happens at r130 and c8?
it looks like there's a bunch of pre eq going on in there i do not fully grasp.

OUTPUT SECTION.
This is a realm I'm quite comfortable with so Its more of a figure out what I need issue.
I did decide to go with a cab sim option but not sure which one to build. I always used
4x12's loaded with eminence pa speakers or wedges loaded with celestion 80w bass guitar speakers.
A bit of a wierd speaker set up but I'm not a lead/solo player. I hate open back with a passion and
like to fit around the vocals and lead guitar not stomp on them.

REVERB:
Simple, Scrap it. I'd like to convert it to another effects send rather than than trying to find
another full size 3 spring accutronics. I hardly ever use on board reverb anyway.
Thanks in advance for any assistance