8 posts
DTR, I recently went through the Guv'nor newer model circut (2 plus) with my electronics wiz buddy. There's some strange stuff in there but we basically came up with a fix for the lack of treble... just completely remove C22. Also, we changed the bias to the clipping diodes (red LEDs on this pedal) by changing the value of R12. We stuck in a 50k trimmer and swept around checking out tones, eventually settling on 10k, then replaced the original 1k resistor. Result... best-sounding pedal in a shootout with 6 others last night... very satisfying.
Very cool! Thanks for the update. And, for remembering that the one reason I didn't really dig the Guv II was the lack of open top end. But now you know what I'm going to say next... If you like that pedal that much, you owe it to yourself to buy a kit and build the REALLY good version! The kits (ggg) are of the original Guv'nor and every review Ive ever seen said it was better. Several boutique pedals are based off that version, including the Cruchbox that so many people love.
I don't think it will be as satisfying. We looked at the circuit for the GGG kit, and it is modeled after the GV-1 like you said--which is exactly why we didn't order it! The circuit is completely different. I can see people preferring the GV-1, but not to the GV-2 with these mods... blind it's far superior (I played with a guitarist who used a GV-1 for years so I'm pretty familiar with it).
I honestly LOVE the GV-2 with these mods. For one thing, the EQ on the GV-2 is more flexible, wider, and with better control... GV-1 has bass/mid/treble, GV-2 has that added deep knob which uses a pretty brilliant circuit to blend in low end. You gotta trust me on this one if you still have that pedal... these mods really make it an eye-opening pedal. My buddy Joe (himself a killer electronics wiz, ex-UA, Korg, etc) ordered one off ebay that night just because he was so impressed with it after working on it. Also I don't know if you've opened your GV-2 up, but the circuit is very nice and tight--tiny 1/8 watt resistors, box caps, very tightly engineered for the small pedal form factor. It's really an example of nice hand craftmanship. It's not very often these days that we open up a pedal and are in any way impressed and we were both very impressed with the GV-2. If GGG had that circuit, I'd buy it in a heartbeat.
There's something weird about the reviews I've read online of the GV-2 plus... it isn't anything at all like the pedal I have. But here's teh weird part, when we opened up the pedal the board was labeled GV-1 with a revision number... though it was clearly a GV-2, not a GV-1, for one thing it had two opamps and the original only has one, and the circuit was the schematic we found online. I've seen gutshots online of the GV-2 though where the board is labelled a GV-2... so there is some sort of voodoo there, maybe mine's really old? Anyway I always thought it was my best lead pedal, really does something wonderful with lead notes, but the new world of treble this mod opens up really changes the pedal, makes it match up to my other pedals in terms of treble, and adds a whole bunch of richness to the distortion. The LEDs were not correctly biased in the original...
I put one on my watch list on ebay right after you wrote this... These things go fairly cheap. As you know, I flipped that one and stayed with the Jackhammer instead. Now I have read (may not be true) that the Jackhammer on the OD side (I never use the distortion side. The OD side sounds WAY better) is the same circuit as the Guv II except for the EQ. I think the Jackhammer is a great pedal for the price, for someone looking for the classic 80s type Marshall sound.
I'm going to snag one on ebay and check out what you are saying. I'll open it up and send you pics to see if it's like yours. No surprise at all if the circuit was changed during production without any notice or reference to a difference... that happens all the time in that world. :(
I'll tell you what else I've been interested in. A Bluesbreaker. Thats another VERY good affordable pedal. Guys buying the kits are modding them and loving them and again, several very highly rated boutique pedals are based on it.
I've always said you could have a really good, small affordable pedal board with all Marshall pedals. Jackhammer or Guv, Bluesbreaker, Ed comp, even the chorus is nice. I bought one of those with knob shaft broken off on ebay for $20. i just set it with needle nose pliers.
p.s. IIRC, the "deep" knob adds bass back in after (in the circuit) all the OD and other tone controls, correct? That's a great way of doing it and some others use this method as well, because the bass freqs don't fair as well going through an OD circuit as everything else does.
I think that in effect, the frequencies are divided early, with bass passed bypassed around the OD section, then added back in later. This is cool because the base can get mushed out going through an OD circuit, and can in fact make the rest of the circuit sound bad, but also with this method, the bass is actually cleaner (unclipped) which can make it tighter and punchier.
I know Jamie digs the Guv II "as-is" because it doesn't have much treble, and has a tone of deep bass. Right up his ally. I needed more open top end. The clipping being rebiased would change the character of the OD so this should be a different pedal now. I'd love to hear it.
I'll post some clips when I get a chance. To be honest I didn't expect it to sound this much better, or I would have recorded some "before" clips...
It's pretty obvious if you look at the schematic...
http://www.fileden.com/files/2008/12/25/2237836/Marshall%20GV2%20Schematic.pdf
R12 is a 1k that sits right in front of the LEDs. This biases the LEDs but way too low... bringing that value up hits them harder, brightens the distortion and adds more character to it.
Even though C22 is a low value, it's sole function is to remove treble. Like a lot of this circuit, it's essentially a holdover from an amp design (Joe and I both noticed this several times in this circuit; there are extraneous parts that are added in as if it is a tube amp, and that have no effect on the sound whatsoever)... I considered going to a lower value, 22pf, 33pf, something like that, to preserve some of the high cut, but completely removed I can still turn the treble control almost all the way up and like it... so we just axed it. Joe is buying one and plans to add a 25k or 50k pot in place of R12, so that it's got controllable bias to the clippers... if the case wasn't so tiny and jam-packed I'd think about doing the same.
Oh and the Deep control is really the coolest part of this circuit, so cool, in fact, that Marshall added that entire second op-amp just to create it. You can see that essentially it creates a mixer circuit, with the first half of the opamp taking the distorted tone, filtering and boosting low end with an active EQ circuit, and then the second half of the opamp mixing it back in to the effect out. Having your cake and eating it too! Pretty cool and very effective especially for smaller amps.