@Jay Omega just a demo of the clean and lead channels. I’d love to hear how much gain and saturation is on tap.I can put something together. Any sounds in particular you’d be interested in?
When you say +/++, is it switchable with a mid pull pot? I’d love to do an amp with a switchable ++, but haven’t seen a schematic or good pictures. JRB32 sent me some pictures of a ++ amp that also had an R2 mod, so I wasn’t able to tell what was ++ and what was R2@Jay Omega just a demo of the clean and lead channels. I’d love to hear how much gain and saturation is on tap.
Typical settings I use on my Mark IIC+/++ HRG
Volume 1 = 7
Treble (pulled) = 6
Bass = 2.5
Middle = 2
Master 1 = 4.5
Lead Drive (pulled) = 6.5
Lead Master = 4
GEQ settings
80hz = above middle bar
240hz = barely below middle bar
750hz = just above lowest bar
2200hz = middle bar
6600hz = barely below middle bar
Thanks for the compliment!Stunning work!
From what I have gleaned between schematics and looking at exactly one ++ mod in person, the mod is:
1) A 3.3M + 20pF cap (in series) are added parallel to the existing 3.3M + 20pF cap (that are in parallel) that bridges across the lead channel gain stages. The tonal change by itself was pretty subtle if memory serves.
2) A 15uF tant cap was added across the 1.5K cathode resistor in the third gain stage (the one that drives the reverb tank and the 'send' part of the effects loop). This has the largest impact on the sound - the amp gets significantly louder, and the level driving the EQ is significantly hotter.
3) A 330K resistor is added in parallel with the 'lead drive' pot, and the 680K series resistance is increase to 1M. This cuts the signal going into the lead gain stages and softens the distortion a bit.
In some situations I find #2 a bit too much, and it can really eat into the clean headroom of the preamp, however you can get a more aggressive lead tone with it engaged. In one of my preamp boards, I added a Vactrol to this cap so that it only kicks in when then lead mode is engaged, and that has been my favorite iteration of the ++ mod.
EDIT: in the Mark 3, the cap in #2 above was switchable in and out via a relay in that amps 'Rhythm 2' channel. In addition, the voltage divider leading to the 'send' of the amp also kicked in (R130), to reduce the gain jump when adding in the cathode bias cap. The R2 mod involved converting R130 into a pot so you could dial in the amount of gain reduction to your tastes.
Does the above mods apply to the IIB ? There are similarities to the C+ schematic by JRB32. I tried the V2 B mod on the C+ schematic. I tried a 2.2uf tantulum with the 1.5kR . I really didnt notice much in the way of tonal differences just a slight increase in white noise .It's alive!!
It was pretty late by the time I finished wiring everything and finding / fixing a few goofs, so I haven't had much time to fully test and wasn't able to crank it up.
One thing I wasn't expecting, my IIB lead drive pot switch is pull to open rather than pull to close like the others. So basically it became a "PUSH LEAD" or "PULL RHYTHM" LOL. This doesn't bother me, but thought it would be good to let folks know in case they convert their own and want to change the pot.
Also, when changing from lead to rhythm I get a volume swell. This is probably vactrol hysteresis
I'd like to start looking at sound clips, does anybody have an IR they recommend? I have a Torpedo Captor and an Axe FX II, but might be able to figure out how to apply a software IR in a DAW.
Awesome !! I want one looks great !!
