owlexifry
Well-Known Member
just thought i’d share this recent build story (well, rebuild), might be interesting to some.
I've had a heavily modified mojotone(stewmac) 2204/JCM800 kit build sitting around since I first built it in late 2020.
(did the usual mods like José master volume and switchable zener diode clipping, and other mods I tried that probably didn't sound that great)
- stripped it down
- designed wiring layout to allow switching (DPDT) between clean / crunch modes - as per SLO100 normal channel.
- rebuilt with new layout (+ improved grounding)
at this point - the preamp here, with the single DPDT switch - was essentially a direct clone of the SLO normal channel (clean / crunch) - with exception to other variables like B+ voltages and filtering etc. + bright cap hardwired on (i never turn it off on my SLO100 clone build).
Sounded great.
Did some reading on the forums, and saw a lot of people talking about how the X88R rack preamp versions of the crunch channel are more aggressive than the SLO crunch. Found some schematics, and yeah I could see what they were on about.
- So I retroactively decided to add switches to modify x2 values to match soldano X88R-spec as seen on available schematics.
(2M2 to 680K via parallel 1M; 1uF cathode bypass (V2A) to 100nF)
Also added another switchable gain boost mod that i tried and really liked - cathode bypass cap on V1B (470nF)
Finished gut-shot:
band prac shake-down: (discovered most of the volume range is in the first 1/4 turn of the MV lol)
The last couple days I've been unwell, so not at work and house-bound.
Was a great opportunity to play with this amp some more, so I decided to crack open the treasure chest and actually tried out something different other than a JJ for V1.
I've mostly been pretty lazy/sketpical about rolling tubes, but i assume V1 would be most vulnerable to tube changes, and since this amp only has x3 12AX7s, I gave it a go.
- tried an EHX, sounded much the same as JJ, maybe a little smoother.
- then i tried a Tung-Sol.
HOLY SHIT.
Now I get why there's people that rave about this one.
I could feel it immediately, it was like the blooming of the distortion/grind was opening/breathing with greater ease / more dynamic. It's hard to describe and I'd hate to use mojo terminology/jargon.
As objectively as I could tell, it sounds like there's a little bit more high end sizzle in the Tung-Sol than the JJ.
V1 position for a high gain amp - i would definitely recommend this one.
other specs:
x3 12AX7 (V1: Tung Sol V2: JJ V3: Sovtek LPS)
x2 KT77 (Genalex)
B+1 filter cap - 200uF (F&T 100+100 cap can) - for maximum punch / low end response.
since I had so much free time at home off work, I've attempted to showcase the tones this amp is capable of with some demos.
I'm very pleased with how much tight saturated gain this has for an amp with just x3 12AX7s.
CRUNCH CHANNEL DEMO (BOOSTED)
CLEAN & CRUNCH DEMO (FULL SWEEP FROM CLEAN TO CRUNCH, +/- BOOSTING)
I've had a heavily modified mojotone(stewmac) 2204/JCM800 kit build sitting around since I first built it in late 2020.
(did the usual mods like José master volume and switchable zener diode clipping, and other mods I tried that probably didn't sound that great)
- stripped it down
- designed wiring layout to allow switching (DPDT) between clean / crunch modes - as per SLO100 normal channel.
- rebuilt with new layout (+ improved grounding)
at this point - the preamp here, with the single DPDT switch - was essentially a direct clone of the SLO normal channel (clean / crunch) - with exception to other variables like B+ voltages and filtering etc. + bright cap hardwired on (i never turn it off on my SLO100 clone build).
Sounded great.
Did some reading on the forums, and saw a lot of people talking about how the X88R rack preamp versions of the crunch channel are more aggressive than the SLO crunch. Found some schematics, and yeah I could see what they were on about.
- So I retroactively decided to add switches to modify x2 values to match soldano X88R-spec as seen on available schematics.
(2M2 to 680K via parallel 1M; 1uF cathode bypass (V2A) to 100nF)
Also added another switchable gain boost mod that i tried and really liked - cathode bypass cap on V1B (470nF)
Finished gut-shot:
band prac shake-down: (discovered most of the volume range is in the first 1/4 turn of the MV lol)
The last couple days I've been unwell, so not at work and house-bound.
Was a great opportunity to play with this amp some more, so I decided to crack open the treasure chest and actually tried out something different other than a JJ for V1.
I've mostly been pretty lazy/sketpical about rolling tubes, but i assume V1 would be most vulnerable to tube changes, and since this amp only has x3 12AX7s, I gave it a go.
- tried an EHX, sounded much the same as JJ, maybe a little smoother.
- then i tried a Tung-Sol.
HOLY SHIT.
Now I get why there's people that rave about this one.
I could feel it immediately, it was like the blooming of the distortion/grind was opening/breathing with greater ease / more dynamic. It's hard to describe and I'd hate to use mojo terminology/jargon.
As objectively as I could tell, it sounds like there's a little bit more high end sizzle in the Tung-Sol than the JJ.
V1 position for a high gain amp - i would definitely recommend this one.
other specs:
x3 12AX7 (V1: Tung Sol V2: JJ V3: Sovtek LPS)
x2 KT77 (Genalex)
B+1 filter cap - 200uF (F&T 100+100 cap can) - for maximum punch / low end response.
since I had so much free time at home off work, I've attempted to showcase the tones this amp is capable of with some demos.
I'm very pleased with how much tight saturated gain this has for an amp with just x3 12AX7s.
CRUNCH CHANNEL DEMO (BOOSTED)
CLEAN & CRUNCH DEMO (FULL SWEEP FROM CLEAN TO CRUNCH, +/- BOOSTING)
