was thinking of adding a Bias pot to MKIV but

[jamme61]

After searching the internet, for info on, how to install I bias pot on a MKIV boogie. I have been talked into buying tubes from Eurotubes, or Lordvalve, or even Mesa boogie, and forget about it. It seems on Mesa boogie amps bias is not a big deal. I'm a new mesa guy, so I have to learn, the boogie way.

 

[Rayder]

ive heard that mesa from the factory has their amps running cold, maybe to extend tube life???? you could always have a tech set the right bias for you

 

[jamme61]

I'm not a tech, but I think there's just one resistor that needs to be changed, or a bias pot added, to change the bias of the tubes. My problem is my tech will have the amp for at least 2 weeks. That's why I was trying to install a bias pot. My lonestar was cold enough to run the 6l6's on the el34 bias and still have them within the bias range. I do not sugest anyone else try that, you can fry your tubes and amp, if the bias is out of range.

 

[Anonymous]

deleted

 

[stokes]

The current draw(bias) will drift as the tubes age.This is just my opinion,I think Mesa sets the bias on the cold side for liability reasons,if the current drifts higher there is less likelyhood that anything will fry causing Mesa to be responsible.Whenever somebody sells you tubes that "match" your amps bias instead of biasing the tubes in the circuit,it is a very general "match",there is a lot of latitude so the tubes will be "safe" in that particular amp but wont neccesarilly sound their best.Why does your tech need the amp for 2 weeks to perform the adjustable bias mod?It doesnt take more than 10 minutes to do this mod.You just replace one resistor with an adjustable cermet pot and set the bias when you change the tubes.It is a very worthwile mod,allows you to use whatever tubes you want,I dont know what your tech is gonna charge you for this mod but I have never charged more than $20 to do it and have done it for free many times when changing tubes for someone,makes it easier on me so I can bias whatever tubes the guy wants to use and they will sound and perform their best,not just safely.I would find somebody that can do it for you,you wont be sorry.

 

[jamme61]

Stokes, if you live near me in NJ, I'll gladly pay you to add a bias pot. My tech will do it in two weeks for $50. He is always swamped with work. Also If you can let me know the location of the bias resistor on a 2005 Mark IV I think I can add the pot, myself. I was able to add one to my 5150, but I need some direction. Thanks for any help on this.

 

[stokes]

jamme-email me at [email protected] and I'll do my best to walk you thru it.What part of NJ are you in?I am In Staten Island now,originally from Bklyn.If you want to bring it here I'll show you how to do it.I still have a few of those pots left.

 

[jamme61]

sent you an e-mail, thanks.