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previous: Steve A. Joe:  &nb... -- 1/13/2000 5:37 AM View Thread

Re: Mesa Boogie Preamp

1/14/2000 1:36 AM
Joe L
Re: Mesa Boogie Preamp
quote:
"With the OD channel active, is the signal from the Clean channel also present?"
 
 
Yes it is Steve and it is out of phase. But it is so swamped by the lead channel that I don't find that it is significant.  
 
quote:
"Isn't there a "Warren Haynes" mod for the SLO100? I just saw it on my hard drive last week but have not been able to find it again. 8-("
 
 
The "Warren Haynes" mod is simply the removal of the .001uF cap that bypasses the OD Lead Volume pot. This cap is missing on your drawing so it's basically the "Warren Haynes" mod as is.  
 
quote:
"BTW Dennis Claessens sent me some notes on modding the SLO100 that I posted as:"
 
 
Cool stuff and thanks for posting it! I've done 3 clones and one that I built for a friend I used Tesla and EI preamp tubes in it with great success. My favorite preamp tubes so far are some old RCA/Fender pulls and one particular NOS Tungsol 12AX7/A I had hanging around the shop at work that we were about to throw out. The Teslas were a bit weak on gain but had nice tone. Here is a quick clip I did to demo the amp for my friend right before I shipped it to him - http://www.communique.net/~jlemoine/rapsamp.mp3. No EQ was used on the recording and it was done on a homemade 2-12 cab loaded with 12T-75s using an SM58b mike right here in the living room.  
 
BTW, I have gotten good pics of the SLO and was able to proof the schematic. I have already mentioned the missing .001uF cap bypassing the OD Volume pot. In addition, the feed to the Clean channel is connected to the point BEFORE the paralleled .002uF/470K, not after it like the Lead channel. The 100uF filter cap in the Opto supply is actually 1000uF.  
 
A few other quick notes:  
 
All caps .002uF and smaller are ceramic. All electrolytics are Mallory TC series. All coupling caps are 400v Mallory PVC mylar/polyester types which I think are about the same as Sprague 225P/418P. The exceptions are the 1uF cathode bypass caps which are marked Philips 1/100. That confuses me because the only caps that I can find that Philips sells are ceramics and they do make a 1uF/50v ceramic. I just used some poly CDEs as subs and they work just fine.  
 
Good info for anyone interested in building one. Cap types do make a difference in sound. I went thru the amp trying different types of ceramic and poly on a switch and there were big differences between the two. It's all a matter of tastes as to which is better.  
 
..Joe L  

 
Replies:
Steve A. Joe:  &nb... -- 1/14/2000 4:10 AM
Wild Bill Joe, I sold Phillips film caps for ... -- 1/15/2000 3:07 AM