Tube Question

[Wireneck]

I've owned a Mesa Boogie Nomad 45 short head for a little over a year. On top of living in an apartment and not being active in a band for a while, I have only had a chance to really crank up the amp a few times. I've recently formed a new band and we have rehearsed a few times over the last month.
While playing/rehearsing it has come to my attention that the amp sounds very pushed in the midrange and lacking a considerable amount of low end. It sounds pretty good at the lower volumes but once it gets cranked it sounds overly edgy. The only way I can think to describe it is that it sounds liek someone stepped on a wah pedal and left it set in the upper midrange position. I want to believe that it didn't sound this way when I first bought the amp but its tough to say because I really can't remember.
So on to my question.......is there anyway that the tubes could be affecting the tone in this manner? Does anyone else own a Nomad head/amp? I am curious to know if this is a tonal characteristic of the amp. Its not horrible but its more sharp/edgy than I think it should be. Even with the lows all the way up I get very little chunk.

[joro]

I have a 55......
I can change tubes from 6L6s to EL34s
other than that...it's pretty similar to yours...
and I can't say that the mids sound pushed when cranked......

but, you can adjust your tone....

try setting up your footswitch on a different channel with different settings...
try less gain and more main...
less treble...less mid and more bass...

Your's has something that mine does not though...
a "Normal/extreme Power voicing switch"...
I don't know what it does but, have you tried switching it when you crank?

good luck man..
Joe

[HangDawg]

My rectifier looses a lot of the low end when the power tubes start getting old. Mine is also due for a recapping I'm sure. How old is it? If it's 10 years or older you may want to have her serviced. When I get the cash, I'm sending mine to voodoo amps.

[ermghoti]

Tube amps simply sound different as you turn up. If you can use your tone controls to get the sound you want, you don't have a problem. Make sure your impedance is set right, and if you have an option, try a lower setting, this seems to emphasize lows over mids on my rig. You can also run a slight mis-match, like head set to 4 for cab that calls for 8. It won't really hurt anything, except maybe going through power tubes a hair faster.

[Wireneck]

Thanks for the information guys. Its not that the tone is completely undesirable the amp just seems to have alot more edge than our other guitarist Rectifier regardless of the tone settings. I don't think the mids would be as pronounced if the low end were more present. It seems that the louder I turn up the more it rolls off.
Im not sure how old the amp is. I bought it used off a guy. I don't have the cash to swap both the pre-amp and the power tubes right now. If I was going to take a gamble which would you guys recommend? Its probably time to change them even if they aren't adding to this situation.