1 post / 0 new
admin2

MM 115-65 distorted tone--HELP!

AuthorMessage
 

Keith Wilkes (woody96)
Username: woody96

Registered: 06-2007
Posted on Thursday, July 21, 2011 - 05:04 pm:   

Picked up a very nice condition 115-65 MM. Played it briefly and was on my way home with it. Once home and playing it out a good bit, noticed the following: It has a "distorted" kind of "fizzy" tone at anything above bedroom levels...AND, the distorted/fizzy tone gets worse with stronger pick attack or stronger strumming. Played softly at low volume it sounds pretty good.
I tried several known good EL34's thinking these old Sylvanias were tired....nothing changed; if anything, the distorted tone got worse with these other el34's..
Any ideas? Simple fixes or things to try before off to the tech it goes???
THX!!
Bill Traylor (bozzy369)
Username: bozzy369

Registered: 02-2008
Posted on Thursday, July 21, 2011 - 10:58 pm:   

That could be other things ,but I'd be betting on the speaker being bad .
Keith Wilkes (woody96)
Username: woody96

Registered: 06-2007
Posted on Friday, July 22, 2011 - 03:15 am:   

I was hoping for that, but plugged in some speakers from another cabinet, alas, the same tone and distortion!....
Mike Kaus (mm210)
Username: mm210

Registered: 05-2006
Posted on Friday, July 22, 2011 - 09:03 am:   

with or without tube PI?
Lars Verholt (lmv)
Username: lmv

Registered: 11-2009
Posted on Friday, July 22, 2011 - 08:30 pm:   

I may be asking an obvious question here: Did you try both channels?

Cheers,
Lars Verholt
Keith Wilkes (woody96)
Username: woody96

Registered: 06-2007
Posted on Sunday, July 24, 2011 - 03:54 pm:   

It has the 12ax7 PI and I did try both channels...the mildly dist tone is on both channels.....
Mike Kaus (mm210)
Username: mm210

Registered: 05-2006
Posted on Thursday, July 28, 2011 - 12:06 pm:   

The fact that it has the 12ax7 PI and the fact that you call it "fuzzy" almost leads me to believe that it's suffering crossover dsitortion from being biased TOO cold. THe fact that you say it changes with the other tubes kind of makes me suspicious of this. Try biasing the amp properly and see what it does. Mike
Keith Wilkes (woody96)
Username: woody96

Registered: 06-2007
Posted on Friday, July 29, 2011 - 07:16 am:   

Thanks; appreciate it!.....I was thinking maybe the same thing---biasing problem......