tube question

[Sling75]

i'm going to post this here becuase i know i'll get a good answer. please don't mind my writing i'm holding my baby girl with my other hand. anyways, i have a peavey bravo 20 watt head that is powered by el84's. recently i have noticed a volume difference in the clean and gain channels. when both are set to 5 half way turned up, the clean channel is twice as loud and has much more punch as the gain channel. if i turn the gain channel up more it gets muddy and i start to get feed back noise. could this be tubes? i just did a retube to grove tubes. would the power tubes or pre amp tubes effect one channel and not the other? any ideas?

 

[stokes]

Its possible that the new power tubes are biased too hot,I dont have a schem for that amp,so I am not sure how they generate the additional gain for the lead channel,so it could be something else as well.I am basing the power tube scenario on my experience with Boogie amps and adjusting the bias.The preamp in a Boogie is overdriven a lot,and the output is kept fairly clean,I like a little more power tube saturation,but if you try to bias it as hot as I would a Fender type amp,I get a good strong clean channel and the lead channel will crap out as you describe.The clean channel on a Boogie is basically a Fender,but the drive channel is too much and sends the output too close too cutoff when biased that hot.

 

[Sling75]

Good call man! i just put the original tubes back in the little devil and it sounds much better. The channels are even again. i guess if i want to retube it i'm going to have to go through Doug at Doug tubes.

 

[stokes]

When changing power tubes,the bias should always be checked.You were lucky,tubes that are biased too hot can do serious damage to an amp.