IIC+ mod to Quad?

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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.
 
I had heard that both the Quad and Studio were the IIC and not the IIC+.
 
Very interesting man :) 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:

To achieve greater tonal flexibility and footswitchable freedom, the Quad is separated into two
channels sharing one common input. Each channel offers two modes and a pre-assignable 5 band
graphic equalizer. Channel 1 is very similar to the Mark IIC, while Channel 2 is very much like the
Mark III.
These were the premier guitar amps for the last five years, winning the praise of such
guitar giants as Steve Lukather, Lee Ritenour, Michael Landau, Stevie Ray Vaughn, and many
more. We found that many of these players used more than one amp and switched between them
for different sounds. A great idea but very heavy and bulky to move requiring custom made
switching systems. Thus, the need for the Quad. Two incredibly versatile amps in one taking up a

So even with the differences that *are* there, he says it's pretty much the same huh? Interesting indeed :) The C+ed studio that sold on ebay also had the recording outs disconnected as part of the mod.
 
Yeah. He did say that there were a few differences, mostly in some of the pf caps, but didn't have the schematic in front of him. He was pretty clear about the point that the IIC+ and IIC are very different circuits and the Quad is basically the IIC+. The changes do seem pretty minimal. I guess the point of the "IIC+ mod" is just to bring it to be exactly the same as the IIC+ circuit, to hopefully make it have the same mojo. For me I don't think it's worth it.

Did taking out that input cap do anything noticable?
 
FWIW, when I had my Quad pre, I did exactly what Mike B recommended and sent the pre out directly to my effects (tc2290 back then) and from there directly to my old strategy 400 power amp. It sounded so much better. When I used the effects return and then out of the regular output, I noticed it did get darker and more compressed in a way I did not care for. I used the 2290's ability to adjust the volume out via program presets to control the overall volume. My strategy was set with the masters at no more than 5 usually (plenty loud!!!!) I have some old VHS tapes of me gigging in 1989 and 1990 and still love the tone (even though my playing has improved since those old "hair metal" days LOL!) Mike B told me the same thing about the Quad being closer to the IIC+ than the IIC.
 
This tuesday or wednesday I'm going to be doing an A/B with two things: effects out vs. normal out, and my never replaced filter caps vs brand new ones.
 
schnarf said:
This tuesday or wednesday I'm going to be doing an A/B with two things: effects out vs. normal out, and my never replaced filter caps vs brand new ones.

Could you make some clips? Especially from the effects out / normal out A/B? You've got a 20/20, right?

(this is Mhgny_JP from JP forums btw)
 
So, are the overall output controls disabled when using the send fx instead of the normal output? Do you control the overall level with the master pots? Last question: is it really safe to do this or could it damage something after long time use? thanks!
btw, I'm asking 'cause I own a studio pre...

4Draw said:
Could you make some clips? Especially from the effects out / normal out A/B? You've got a 20/20, right?

It would really be a great thing!
 
I'm definately going to be making clips. I've got a 50/50. ytse_jam, it should be completely safe to run the effects out instead of the normal output.
 
ytse_jam said:
So, are the overall output controls disabled when using the send fx instead of the normal output? Do you control the overall level with the master pots? Last question: is it really safe to do this or could it damage something after long time use? thanks!
btw, I'm asking 'cause I own a studio pre...

4Draw said:
Could you make some clips? Especially from the effects out / normal out A/B? You've got a 20/20, right?

It would really be a great thing!

Mike B told me that there is no possible way to do damage to the Quad in this config. The master pots do become useless at this point though, but you can program your effects to adjust the overall volume fed to your power amps. This is also true for the Studio Pre.
 
Yeah the overall output is useless but you can still use the channel masters. I have tried both my studio and Quad running via the fx send into my poweramp and it does sound a bit better, a bit....more, if you will.
 

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