Tube Amps / Music Electronics
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|12/2/1999 1:06 AM|
I read somewhere on ampage something about re-wiring the master vol.on a MK11C(clean channel)so that the volume would not come up so quickly.If anybody out there is familiar with this mod I would really appreciate if you could share this info.Thanks
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|12/2/1999 8:40 PM|
That was probably my post.
The master volume pot need to be rewired as a voltage divider instead of a shunt-to-ground circuit. Looking at the pot from behind, the left terminal should already be connected to ground. There should be two wires that are connected to the middle terminal. One of them needs to be moved over to the right terminal. I don't know what the colors of these wires are, but the result should be that the right terminal is connected to the output of the preamp circuit and the middle terminal connects to the graphic EQ and/or output section of the amp. A schematic might be helpful here to figure this out.
It's been a few years since I've done this mod - sorry I've come up short on the details!
|12/2/1999 10:28 PM|
Hmmm... if I remember correctly, my (now gone) IIC+ only one wire (besides ground) going to the pot, so the other conenction was done at the extremely-crowded PCB. One word of caution: rewiring the MV as a voltage divider may require the use of a small cap across the pot, otherwise highs may be lost at lower volumes.
|12/2/1999 10:54 PM|
I know it's an easy job on the Mark II and IIB. That's too bad if things are more involved on the IIC!
As far as tone goes, I think the problems are worse with the stock wiring of the master volume. True, there isn't any series resistance, but the resistance to ground is very low, even at moderate playing volume, resulting in thin tone. Plus, trying to zero in on the proper rhythm volume level is a real headache unless the mod is done.
|12/2/1999 11:34 PM|
Based upon your post, I guess the IBB is quite different from the IIC+ (which is essentially a Mark III without the Rhythm II deal). For starters, the PCB is extremely crowded (mine had reverb and graphic EQ, which make it even more crowded). Then, I never had any problems at all dialing in a good rhythm sound at the right volume... the Lead has its own master, so it was always possible to dial both sounds (volume-wise) without difficulty. It was a great little amp, my only beef is that I O.D.'d on that sound, there was a particular frequency band in there (midrange, of course), that became annoying... too anoying. And then the fact that the amps are stiff unless the presence is dialed real low, and by then th sound was way compressed.
The IIBs I've played are different animals. Much more open sounding and way fatter too, sound more like a cranked amp than a preamp fuzztone.
|12/3/1999 1:33 AM|
Thanks for the help,guys.Gil is right,only one wire on the wiper of that pot,have to try to unscramble that PCB-way crowded.Thanks again.
|12/3/1999 8:26 AM|
But wait.... here's part two on my post. Your IIC+ dates from the times when Boogie was still using pretty good quality PCBs with thick traces. SO you can put the iron to it and work it out, if you think it will make a difference. The one thing I would caution against is that is it SO crowded in there, that it's failry easy to melt a wire or burn something that gets in the way of you and your target spot on the PCB, so be real careful.
IF you tell me whether there is something that "bugs" you about that amp, I may be able to offer some ideas. I did toy a bit with mine, but actually messing with the Master was something that never really bothered me. Granted, I used a rack with the thing and I played the biggest gigs I played in my life with it, so volume was LOUD -- and that amp is most definitely loud.
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