Just talked to Mike B. He says that the IIC+ and IIC are pretty different in circuitry, and when I asked him about modifying the Quad to be closer to IIC+ schematics, he told me that that Quad is basically a IIC+ and not much like a IIC circuit. I made sure I was understanding him right -- the Quad channel 1 is basically a IIC+ and not a IIC.
He did point out a few things that could make the tone a little different. Obviously there are the differences in the circuitry that I've found, but they really are pretty negligable except for that section after the lead. Another point he made is that the record out circuit loads the preamp a little and could darken it. The solution to that is to either disconnect the record out circuit, or to use the effects send direct to power amp. He said another big thing is the power amp. He noted that the later IIb series and most of the IIIs have basically the same power amp. He also said a 50/50 was very close, which I have.
He made the point that he's taken IIIs, which have a very similar layout, and he's modded them to IIC+, so that the circuit is exactly the same, and the output looks the same on the oscilloscope, and it sounds the same, but it doesn't feel the same to the player.
So basically this mod is probably pretty pointless. Everywhere else I've seen has said that the Quad is based on the IIC, but apparently it's actually based on the IIC+. If I could find a schematic of the IIC I could verify this, but frankly I trust Mike B. on this.
The interesting thing is, I was looking to tame a bit of the high end on my Quad, and he told me that if anything the Quad is a little darker than the IIC+. Anyway, he was very informative. If I get curious, I might try to modify the circuit to make it identical to the IIC+, but it seems like it might be a lot of work for little return.
He did point out a few things that could make the tone a little different. Obviously there are the differences in the circuitry that I've found, but they really are pretty negligable except for that section after the lead. Another point he made is that the record out circuit loads the preamp a little and could darken it. The solution to that is to either disconnect the record out circuit, or to use the effects send direct to power amp. He said another big thing is the power amp. He noted that the later IIb series and most of the IIIs have basically the same power amp. He also said a 50/50 was very close, which I have.
He made the point that he's taken IIIs, which have a very similar layout, and he's modded them to IIC+, so that the circuit is exactly the same, and the output looks the same on the oscilloscope, and it sounds the same, but it doesn't feel the same to the player.
So basically this mod is probably pretty pointless. Everywhere else I've seen has said that the Quad is based on the IIC, but apparently it's actually based on the IIC+. If I could find a schematic of the IIC I could verify this, but frankly I trust Mike B. on this.
The interesting thing is, I was looking to tame a bit of the high end on my Quad, and he told me that if anything the Quad is a little darker than the IIC+. Anyway, he was very informative. If I get curious, I might try to modify the circuit to make it identical to the IIC+, but it seems like it might be a lot of work for little return.
Yeah the only thing I ever did on mine was clip out that input cap too, haha. Even the Mesa manual for the quad says it is based on the IIC:
