Biasing an Orange or80m

[dread1]

Hello all!
New to the forum and have a question about the bias on a 1978 orange or80m. I've read that they need to be bias pretty hot in order to sound right. Right now in the power section I have sovtek's and in the preamp are mazda's. The amp sounds pretty cold to me. That meaning it sound's dry with not that great sustain . Although it has decent distortion , it just seems it's lacking something.
Any help would be greatly appreciated.

[drgonzoguitar]

Welcome to the forum!

A few questions:

1) Did you bias the after you replaced the tubes? The hotter the bias does not necessarily equal better tone. 70% of max tube wattage is where you want to target for (EL34 = max 25 watts x.7 = 17.5 watts) You can go higher, but you will be reducing your tube life.

2) Have the electrolytic capacitors have been changed? There are a ton of problems associated with old caps. These are the caps that filter the ripple from the rectifier (tubes like clean DC!).

Unless you know what you are doing inside an amp, do not open it up. Take it to a tech you trust.

[dread1]

Thanks for the welcome and reply!
The amp is bone stock and nothing has been changed. I just bought it from a friend that I've known for years. I didn't even change the tubes or do anything yet. I've just been reading alot on these models about not biasing it like it's a marshall and that they needed to be biased hot. I'll bring it to Louis from Louis electric amplifiers and have him take a look at it. I just figured I'd find out as much as I could about it first.
I guess he would know if it needed a cap job right?

[wixedmords]

70% of dissipation is not the goal, it is the upper-end of the specification. I have rarely found an amp sounded the best at 70% dissipation, but it does happen occasionally.

Try biasing ever few mA between 50% dissipation and 70% dissipation and where the amp sounds the best is where the bias pot stays.

Biasing an amp basically happens the same way no matter what the model.

PM incoming to the OP.

BTW, Welcome to the forum

[drgonzoguitar]

70% of dissipation is not the goal, it is the upper-end of the specification. I have rarely found an amp sounded the best at 70% dissipation, but it does happen occasionally.


Agreed. I like my Fender amps a bit on the cold side (55%), though my Super Reverb is great at 65%.