Early tube compression - should I change the bias resistors?

[joey_truelove]

I'm trying to get the full picture of what makes a valve/ tube into what it is but sometimes I get a bit confused over it.

For example: people tend to use hot and cold rather arbitrary depending on how they see things. I was told Mesas were biased cold, in this case meaning the bias current is low, not that it runs the valves cold. This further adds to the confusion.

Myles Rose and the guys over at GT claims a lower rated valve would distort earlier, and I must say I like that idea. But then would that mean the bias current draw would be even lower than it is already? In that case it wouldn't be very good at all as that would be sacrificing tone.

I know the red Mesa rating goes all the way down to a 4 on the 1 - 10 GT scale - would going with a red rated valve get me that pushed sound I'm looking for or am I barking up the wrong tree here? Would changing the bias resistors help to achieve this sound?

Cheers!

 

[212Mavguy]

Hi Joey,

biased hot or cold depends on the model of Mesa amp and in some cases there are switches to select bias levels.. Your question can be answered from writings of others who have posted papers online. In your browser window, type in www.aikenamps.com, you will come to Randall Aiken's site, and clues to answer your question here can be gleaned from opening the introductory technical papers section. Aiken has built some of the most wonderful boutique guitar amps ever crafted. There are buttloads of useful technical info on his site, not all are his.

Since this IS the boogie board, helpful papers can also be found linking from the home page found by entering www.mesaboogie.com on the address bar. Near the bottom of the home page in small blue print is the word "articles." The next window contains the famous white paper, and persuasively written document passionately explaining the Mesa tube biasing philosophy. Also, if you are into humorous explanations, there is some good reading on Irishmen in pubs in the Lonestar Special owner's manual, downloadable...some of the best tiolet seat reading anywhere, you butt might fall asleep from its holding your interest way longer than a normal trip to the john!!!

Hope you enjoy the reading. Thanks, because your question allowed me to find some articles I want to review to satisfy my own curiosities...peace to you and all who read and share on the boogie forum!

 

[212Mavguy]

type in the aiken site into the address bar, when hotlinking from the post the comma at the end of the address given screws it all up

 

[joey_truelove]

Cheers man. The amp in question is the Fifty/ Fifty rack-mount