Bias points

[rraawwrr]

I was just parusing around eurotubes.com, and clicked on his Mesa link, which said that Mesa Rectifier amps are set very cold.

What does this mean?

Also, he seemed to suggest that if you run 6L6's in the EL34 bias mode, it "warms" it up, I'm guessing more plate voltage gets through there. It sounds safe enough to try (at least at low levels). What do you guys think? Would this be safe to do? I've read reviews where people have said that their Rectifiers have been considerably bettered by the EL34 bias point with 6L6 tubes.

Ayudame!

Thanks

Eric

 

[Gearjoneser]

Re: Bias points

Don't do it. You'll just burn up your tubes. If you do want to give it a shot, take some old spare 'throwaways' and use those for the experiment. EL-34's have higher plate voltage AND current, so it'll sound like your 6L6's are WAY overbiased, and that doesn't necessarily sound good, just too pushed sounding.

Most Rectifier owners who take tone seriously have a tech install a mini bias pot, so they can set the bias perfectly. Randall Smith's biggest design blunder was NOT installing that pot. He just figured he'd find a good median bias point, that work with Mesa labeled tubes, and make it more user friendly. He shoulda been thinking 'tone friendly.'

 

[kannibul]

Re: Bias points

You could also get a colder set of 6L6's.

One thing to note, is that each tube vendor measures things a little differently.

Things like having their matcher calibrated, how accurate it's been calibrated and to what standard, what kind of power regulation they have on their matcher, what voltages they match them at, and so on.

What results is a lot of variance between vendors.

One vendors "30" is in the middle for what they get, while another says "25" is typical - AND - both of these could be way apart from each other in your amp.

Do yourself a favor, and get a Weber Bias Rite, and a Digital Meter, or the Bias Rite with the Plate Voltage option.

Then you can check to see where things line up with a new set of tubes from your favorite vendor.

 

[Gearjoneser]

Re: Bias points

Sometimes, I'm inclined to think Bob at Eurotubes doesn't know what the hell he's talking about! His idea is retarded. Also, he almost ruined another forum member's Mesa by suggesting that he use GZ-34 Rectifiers instead of the big bottle 5U4G.
This forum member blew up half his tubes, and almost fried his expensive amp because of Bob's erroneous advise. The guy isn't Reinhold Bogner, he's just a JJ distributor. Of course all his advise is "put in JJ's" .....that's all he sells!

Deal with Todd at www.revolutionguitar.com and you won't run into this kind of risky advise.

 

[rraawwrr]

Re: Bias points

Thanks for the heads-upa about Bob, Joneser. I probably wouldn't be allowed to live in my house if I fried my brand new amp...

Will a "colder" set of 6L6's sound better with the cold biasing of the Rectifier?

and,

Is there any way to adjust the bias point without having a trimpot installed? Mesa's, atleast rectifiers, are fixed bias. I'm just afraid that having one installed will cost me more money than I have to spend without getting a loan... :laugh2:

 

[kannibul]

Re: Bias points

Thanks for the heads-upa about Bob, Joneser. I probably wouldn't be allowed to live in my house if I fried my brand new amp...

Will a "colder" set of 6L6's sound better with the cold biasing of the Rectifier?

and,

Is there any way to adjust the bias point without having a trimpot installed? Mesa's, atleast rectifiers, are fixed bias. I'm just afraid that having one installed will cost me more money than I have to spend without getting a loan... :laugh2:

Fixed bias is right - but in most amps, that doesn't mean non-adjustable.
But, sorry to have gotten your hopes up, Mesa's Rectifiers are non-adjustable.

A colder set would probably get it to bias hotter @ idle.