biasing a peavey classic 50

do i need to? or can i just pop the tubes in

Just pop em in and go.

sweet

Mario, that amp is a fized bias amp, which is kind of rare for an EL-84 amp.
Thsi means that if you install thos enew tubes and the plates don't go 'red' and you
like the sound, then you can safely play the amp. IF the tubes start redplating...the long dark elements in the tube start glowing red..., those tubes are drawing too much current and you would want to shut the amp off immediately. IF the tubes don't go redplate but you think the sonics are a bit cold andharsh, the tubes are drawing too little current. IN either of those cases, you will need to have the bias checked and adjusted.

i did this with a peavey classic 20 and no damage yet. if the glow is orange there should be no problem right?

Marzio, the Classic 20 is a cathode biased amp. IT requires no biasing...that is, it is self-biasing.
THe Classic 50 is fixed biased. That doesn't mean that there is no adjustment or that adjustment is not needed. THat means that the bias voltage is set at a fixed point.
Orange glow? THe heater filaments do have a small orange/reddish glow in the center of the tube.
Redplating takes place on the plates of the tube. These are the long, dark elements that are easily seen when you look at the tube. IF there is any indication of a reddish/orange glow to these plates, shut the amp down ASAP.
AS I said in my earlier post, if the plates aren't glowing red and the amp sounds good to you, the bias is set at a usable and safe point. THat doesn't mean it is optimal for that amp or for you....it just means it is safe. IT is good to know a good tech for these amps.
There is a range of 'correct' current draw, and it is interesting to understand what is available for you as a player.

An amp tech told me it would be very easy to install a bias pot in there and that he could do it within his bench fee. He said although the amp is fixed and you could just plug and play, you would need to change the bias if you really wanted the best sound out of any given set of tubes.

BTW, check out this list of tubes from Eruotubes. If you like JJ's, they've put together some matched sets specifically for getting the most out of what different tubes can do for your sound. I haven't bought from them before, but I find this interesting:

https://ssl.eurotubes.com/cart/index.php?page=view_products&category_id=8&sub_category_id=33

An amp tech told me it would be very easy to install a bias pot in there and that he could do it within his bench fee. He said although the amp is fixed and you could just plug and play, you would need to change the bias if you really wanted the best sound out of any given set of tubes.

The 'fixed' part of fixed bias doesn't mean that it can't be changed. ....and it can be changed without putting in a bias potentiometer. That's a good price for a bias pot installation, too.
Plug and play with a fixed bias amp???? Plug in some tubes with the wrong performance specs, turn it on without observing, and play away. Within a few minutes your amp might well be up in smoke.

wow, those retube kits are cheap! i'm interested in that blues combination.

yeah i think i'll probably take it to an amp tech just to be sure.

i emailed eurotubes and they told me this:

The C50 has a fixed bias, so there is no adjustment to be made and your tubes will be plug and play. All you need to do is clean your tube sockets during installation.

so how big of a difference would there be if i just plug them in instead of biasing. if it's not that big of a deal, i don't want to take it in and pay a bench fee.

Years ago I got a matched set for a classic 50 from eurotubes, can't say if they were "specially" matched to the amp's bias rating or not but they sound fine.

Marzio, if it interests you, reread this entire thread. The advice you got from eurotubes
that your amp is a 'plug and play' amp is erroneous. Plug and play may or may not function for any certain set of power tubes in your amp. REread and/or go to
http://www.aikenamps.com/ for a fuller understanding of biasing. 'Plug and play' in a fixed bias amp may function safely adn yield good sounds, it may burn those tubes and possibly your transformer dodwn, or it may be safe but cold and harsh like a SS amp. There is a range of correctness when considering the bias point with a fixed bias circuit.

Bias it or don't get it biased.....the choice is yours.

FWIW, I ran a C50 for 8 years and currently run 2 C30s. I've changed tubes in all of them several times so while I'm not an amp guru, I do have practical experience with these amps. All I've ever done is told the tube dealer what amp I was putting the tubes into and what I wanted (more/less/average break up) and then put them in. While I don't doubt that there problems could exist regarding bias, I have never experienced problems of any kind nor has anyone else I know that plays one of the classic series amps ever had any in changing the tubes this way.

Take it for what it's worth...which might not be much. :wink:

Bias it or don't get it biased.....the choice is yours.

FWIW, I ran a C50 for 8 years and currently run 2 C30s. I've changed tubes in all of them several times so while I'm not an amp guru, I do have practical experience with these amps. All I've ever done is told the tube dealer what amp I was putting the tubes into and what I wanted (more/less/average break up) and then put them in. While I don't doubt that there problems could exist regarding bias, I have never experienced problems of any kind nor has anyone else I know that plays one of the classic series amps ever had any in changing the tubes this way.

Take it for what it's worth...which might not be much. :wink:

AS long as the tubes don't have performance parameters that put the level
of current draw in to the danger zone, you are safe donig this. Put in a set of tubes that draws excessive current draw and DON'T observe the tubes when you fire that amp up, and you may have the choice of whether to buy a new tranformer or a new amp.
PUt in a set of tubes that draws minimal current draw, and you will have a tube amp that sounds like a bad (not a good) SS amp....cold and harsh.
I am not against 'plug and play'.....I just add the caveats...watch the tubes when you put them in for redplating and listen to the amp to hear if it produces good, musical sonics. Within those two extremes of redplating and cold,harsh soncis, one can plug and play as they wish.
I have had good luck with plug and play, also. I do observe for redplating and sonic quality, though.