Where can I get a bias pot installed in So-Cal?

[Sludgenutz]

Where can I get a bias pot installed in So-Cal?

I called the Mesa Hollywood store this week and asked for the amp shop portion of the store. The fella that answered the phone said that he could advise about amp mods...and without hesitation said, "I don't recommend it".

Did I get some sales floor @ss on the phone...or should I ask for an actual human being, with a name in the rear of the shop ?

Mesa, or other So-Cal recommendations are much appreciated.

edit: This is for a 1989 .50 Caliber + (6L6 tubes).

 

[MesaDCLP]

Call Mesa direct and they will advise.

707-778-6565

 

[nocluejimbo]

Call Mesa direct and they will advise.

707-778-6565

Mesa will recommend you not to do it. They have designed their amps to work the best within the range of the tubes that they sell. This is for the optimal sound and greatest reliability.

 

[jamme61]

When I called mesa about their tubes, running to cold in my new MKIV, they transferred me to a tech. Once I got the tech on the phone, he helped me with what value to try on the outside bias resistor(the one for the two outside tubes) then when I asked him how to identify the main bias resistor, so I could install a bias pot. He told me where to look, and what to measure to find the right resistor. He did also tell me that any one of these changes void the warranty. The guy was great. I understand about the mesa, no bias pot, just use our tubes ect. if your a guy with a lot of good tubes laying around, you want to use them. Even if you use Mesa tubes, you should still make sure they're running hot enough, for good tone. To me Mesa should still offer the Mesa tubes for whoever wants to use them, but please include the $2 bias pot for the other guys. What a load of SH!@ this bias pot thing is. Mesa just wants to sell tubes. With that said, the Mesa tech told me what I needed to know, and was great, about everything.

 

[Sludgenutz]

Thanks for the response jamme61. A large part of the reason why I want to install a bias pot is to dial in the cleanest headroom current 6L6 I can afford, or my favorite...the 6550. I am trying to get acheive a more articulate power amp section.

That was great you found a tech with the info to be "real". I do understand Mesa's thinking and philosophical direction with the fixed bias system, but my Mesa is my property, mine to improve or destroy...and is 17 years old.

It is kinda like the "old days" with muscle cars. You could run a hydraulic tappet cam forever...but to to get that portion of the upper RPM band, one suffered as a labor of love adjusting each valve with a solid tappet cam.

I am not a newb when it comes to electronic theory/methods associated with a bias pot mod. From what I have seen, there does not seem to be much involved in creating and installing a "Mesa bias/aftermarket bias" toggle switch feature. I'm not going to jump into this with reckless abandon.

Again, many thanks!

 

[jamme61]

Sludgenutz that's great, go for it. I want to get the most I can out of my stuff too. That's why I spent so much for the amp. hey be careful with those outside tubes, I already melted one in class A mode. I think it was a bad el34, but still when you go to class A, it bumps up the voltage to those tubes. On my MKIV it goes from 445 to 453 which messes with your bias. you probably know about this, but just in case. also KT88's are cool for headroom with big bottom IMHO. all the best.

 

[Paul Secondino]

If you don't find anyone in your area and are willing to ship your amp, I can highly recomed Joe at Dursonix in West Haven, Connecticut. He has a humble shop but did a superb job installing a trim pot (external ) on my Mesa Mark 3 head.

He's a gear head and I was nervious the first time I met him but after trusting him with my Mark 3, I was very impressed and he corrected my understanding about setting the correct bias range. I thought I had a clue but I didn't :shock:

Anyway, just figured I would throw the info out there just in case. Also, I know that John Suhr from Suhr GUitars is willing to work on other manufacturers amps and he is in Lake Elsinore California. Perhaps you can hook up with him.He's a complete genius with amps and instruments

 

[Sludgenutz]

Hey, I know Lake Elsinore...I almost drowned there in my foolish/ignorant/reckless youth! :roll:

Not too far away! Thanks for the tip!