Nuther dumb tube question

[nhslim]

I bought new tubes for my Peavy Delta Blues (Sovtex EL84's and 12AX7LPS's) same as it had in it. Do i need to have it biased ? The EL84's are two matched sets is there a special order they are installed in?
Thanks.
Judd

[wixedmords]

Re: Nuther dumb tube question

A lot of EL84 driven amps are cathode biased, not needing to be biased, but I still like to check mine.

A fixed biased amp must be biased, a cathode biased amp has a "certain range" of bias built in, so to speak, usually allowing you to plug in tubes and go. Think of "fixed" bias as it needs to be set to a specific bias, not that the bias is unable to be set.

It is good to check the bias on cathode biased amps to make sure it isn't off the map. I have seen cathode biased amps go off the map (too hot), usually an issue with certain brands of tubes in certain amps.

From what I have read, your amp is cathode biased.

[nhslim]

Re: Nuther dumb tube question

Wixedmords
Thanks!

I don't see any thing on he amp that says fixed or not, I guess I'll need to find an amp guy in Mobile.

[wixedmords]

Re: Nuther dumb tube question

Wixedmords
Thanks!

I don't see any thing on he amp that says fixed or not, I guess I'll need to find an amp guy in Mobile.

I would just cruise the internet looking for information on if the amp is fixed or cathode biased.

The problem is in the misuse of the term. You may see statements like 'It is fixed biased, so you don't have to bias it." It really is cathode biased you don't have to bias.

Sorry to keep on this, but it is one of the most mis-used terms in the amp world.