IIC+ mod to Quad?

Triaxis, Quad Preamp, Stereo Power series, Recto Preamp

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schnarf
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IIC+ mod to Quad?

Post by schnarf » Mon Feb 12, 2007 9:10 pm

I've heard the first channel of the Quad is based upon the IIC. Does anybody know the differences between the IIC and IIC+ to enough of an extent that it would be possible to mod my Quad to IIC+?

4nkam
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Post by 4nkam » Tue Feb 13, 2007 12:31 am

Funny that you ask :) This idea has popped in and out of my mind for quite some time now since I own a Studio (based on the IIC preamp) and a Quad. Theoretically speaking, it is possible because the quad ch1 is pretty much a IIC preamp section that would require a few tweaks overall including the lead circuit. Even ch2 could be modded since it's also pretty close.

I actually printed out the schematics for my quad and some C+ schematics to compare and there's only a few differences which "should" be easy to change. Now I'm only talking on a very basic level, swapping out components so they match on paper. How would it sound? I dunno :D

I DO know that snowman had his studio modded to C+ specs so it can be done. Bendinelli supposedly really digs the Quads too :)

schnarf
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Post by schnarf » Tue Feb 13, 2007 12:40 am

I'm thinking about doing it. I was considering doing what you said you did with the schematics, and maybe I will do that if it's as simple as you say. I'll check it out. I'm also thinking about adding just a tad more available gain to the ch1 lead.

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Post by 4nkam » Tue Feb 13, 2007 12:58 am

Yeah I have started to go down that route, then I open up the quad and slowly turn away :D

schnarf
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Post by schnarf » Tue Feb 13, 2007 1:03 am

Yeah, just took a look and tried to trace out what I'd need to do. Basically adding a few capacitors and resistors to the lead stage, and possibly changing a few thought the values are pretty close so it'd probably be unnecessary. Also the lead master/master volume circuit after V12B needs to be changed significantly.

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ytse_jam
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Post by ytse_jam » Tue Feb 13, 2007 5:07 am

Do you all think the differences between IIC and IIC+ are more relevant in the preamp or in the poweramp section?

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4nkam
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Post by 4nkam » Tue Feb 13, 2007 12:19 pm

I think they're equally important but having the preamp section would probably be better than just having the power section you know? I mean look at JP's current rig where he's using a C+ preamp, external graphic EQ, and a recto poweramp and he's still getting great tones :)

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ytse_jam
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Post by ytse_jam » Tue Feb 13, 2007 4:43 pm

you're right, I forgot JP's rig! That ugly green rack unit... :?

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Post by rickgk » Tue Feb 13, 2007 5:18 pm

Where can i find pics of the JP rig your referring to?

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Post by schnarf » Tue Feb 13, 2007 6:18 pm

I just drew the schematic for the Quad channel 1 lead circuit with IIC+ modifications. There are still other modifications around the lead drive/master volume section which I'll draw up sometime soon. Added components are in red, components whose values are changed are in blue, and components whose values do differ but not significantly are in green (I don't think it's really worth changing out the green ones).

Edit: I screwed up the schematic. Here's how it should look:
Image
Last edited by schnarf on Tue Feb 13, 2007 10:26 pm, edited 1 time in total.

4nkam
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Post by 4nkam » Tue Feb 13, 2007 6:59 pm

rickgk wrote:Where can i find pics of the JP rig your referring to?
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4nkam
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Post by 4nkam » Tue Feb 13, 2007 7:16 pm

schnarf wrote:I just drew the schematic for the Quad channel 1 lead circuit with IIC+ modifications. There are still other modifications around the lead drive/master volume section which I'll draw up sometime soon. Added components are in red, components whose values are changed are in blue, and components whose values do differ but not significantly are in green (I don't think it's really worth changing out the green ones).

Image
Which C+ schematic did you use? I don't recall the two additional resistors on the input :)

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Post by schnarf » Tue Feb 13, 2007 10:18 pm

It was posted somewhere on here. Here it is:

Image

Also I realized I screwed up the schematic a little bit. Here's how it should look:

Image

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Post by 4nkam » Sat Feb 17, 2007 6:05 pm

Have ya tried anything yet? I got all the way to the point of pulling the quad out of my setup and removing the cover again...then stopped dead in my tracks. Mesa and their crazy super nice tight wiring :P

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Post by tommyhawk13 » Thu Apr 26, 2007 7:09 pm

bump

Did anyone try this yet? Is it worth the effort?
1987 .50 Caliber, no eq
Quad preamp
50/50 Stereo power amp
4X12 Half back 280w MC90's/Eminence vintage 50's
4X12 Half back 460w MC90's/EV's

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