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plexi gain


 
11/29/2005 12:24 PM
Joe
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plexi gain
Seems like an old, and possibly an overasked question, but just how much gain can a cranked MKII type circuit really have. I only ask because I don't come across them too frequently, or really find my self in a situation where I can turn one all the way up when I do. Building one is on my list, but I have other projects that I have to finish first, including an SLO build that I haven't touched in nearly 3 months.  
 
Joe
 
11/30/2005 2:29 AM
Chris/CMW amps
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Hi Joe  
 
More then most guys do expect. With a "nice" (let's say post '67) plexi (good OT, cathodebypasscap on V2A) you can get early EVH sounds. Lots of classic late 60s and 70s records where made with such amps.  
 
Hope this helps/keep on building!  
 
Chris
 
12/2/2005 6:53 AM
Matt
Just my opinion based on my limited experience but if the amp's gain structure is just right, they can have quite a bit of distortion. However often it seems that they aren't just right and the gain gets 'choked' somewhere (i.e. something gets too clipped or overdriven or something). Hard to describe but it will often have too much of a 'fuzz' quality to the distortion, the attack will sound 'dead', and it won't sustain like it should. It will also often have too many higher harmonics and lack warmth when cranked. But when it's just right, the distortion is rich, the attack is crisp, and the amp sustains/feedsback perfectly, and the high-end isn't so harsh and in-your-face (the tone has warmth).  
 
Now, once you figure out how to get it 'just right', let me know! ;)
 
12/3/2005 9:45 PM
Rick Erickson
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quote:
"Now, once you figure out how to get it 'just right', let me know!"
 
 
Simple - send it to me for service. ;)
 
12/9/2005 7:02 AM
Matt
quote:
"Simple - send it to me for service. ;)"
 
I'm tempted but this was my first build from scratch (late 90's). So, it's not so pretty and I'd be embarrased for you to see it. Besides, it's one of those Hoffman turret boards and I've done quite a bit of parts swaps in it over the years. Those turrets just don't seem to take to multiple parts swaps very well.  
 
Then there's the Hammond 272JX PT...for a 50W amp...in a smallbox cabinet (which had to be butchered a bit to get that huge tranny in)! Big, low value resistors to get the filament voltage down. Just ugly but it has been very reliable. The clean tone is quite good and it's loud as hell but I never can get it to sound great overdriven without a Tubescreamer in front.  
 
And I thought it looked so pretty when I first built it (prior to trying to shoehorn it into that smallbox cab).  
 
At least it's got an OEI OT.;)
 
12/10/2005 4:40 PM
Rick Erickson
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quote:
"this was my first build from scratch"
 
 
Oh, nevermind then... ;)  
 
RE
 
12/21/2005 6:57 AM
Chris/CMW amps
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Hi Joe  
 
A couple of customers and buddies did hear an "upgraded" 1959 SLP re´ssue (MM OT and choke, post pi mv and some little voicing-tweaks) amp (still stock topology) and some of them were asking how many preamp tubes I did add... none!  
 
Keep on rocking and building, merry Xmas,  
 
Chris
 
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