Some Noob-Type Tube Amp Questions

[Big Red]

Hi Folks,

I bought a Peavey Valve King 112 (50 watt) about a month ago... and I'm loving the thing. I have a few basic, tube-amp questions since this is my first tube-amp, and I'm starting to think about the longitivity of the tubes.

My playing scenario: I live in a small apartment and never really put the volume over 2 (the gain is set at about %75, with an internal gain-boost on). Sometimes I use a Boss Blues-Driver, and a Line 6 Uber Metal (never at the same time...LOL) on the clean channel. I use the amp about 3-4 hours a week (I still use solid-state/digital stuff for various other things).


Questions (please don't laugh too hard):

a) Because of the fact that I'm barely pushing the amp, is it safe to assume that I will be able to use this amp for several years without changing a single-tube (barring a faulty tube, or something else stupid happening)? I've done some research, and from what I've read, pre-amp tubes can last decades, while power tubes should be changed once every two years under normal use (whatever "normal" is). Is that correct, based on your first hand experience?

b). What is the difference between the lead and clean channel in terms of pre-amp and power-amp tube operation? I'm trying to properly conceptualize this. What makes the gain channel a gain channel, etc....?

c). Will my pedals, particularly the Uber-Metal, *dramatically* shorten the life of the pre-amp tubes since they are being pushed that much harder?

Thanks in advance. Cheers.

[Vim Fuego]

a) This is a bit like the how often should I change my strings question. Valves or Tubes age during use and will eventually fail even without shocks or impacts (the vacuum is not perfect and some air diffuses in through the hot glass over time). However some people think that used tubes sound better than new ones so only change tubes when needed, others change them regularly.
I almost always change my power tubes (EL34) before I notice a problem with them probably about every 12 months or so. The pre-amp tubes (12AX7) I only change if I notice a problem with them so they last years (although I did do a full re-valve recently!)
My Laney amp has a high gain channel and I do change the pre-amp tubes in that channel more often than the others but only if I notice it is noisy or microphonic. In terms of use, I have band practices every week and gig about twice a month.
b) Most multi channel amps use the same power amp tube configuration for all channels. The diffference is usually in the number of gain stages in the pre-amp for each of the channels. This approximately corresponde to the number of tubes. For example my Laney has 2 tubes in the clean channel and 3 tubes in the drive channel pre-amps.
c) I guess most of the distortion when you use your stomp boxes comes from the boxes themselves. The only thing which would drive the pre-amp tubes more would be if you turned the output level of the stomp box way up. You *may* want to do this so you get a combination of stomp box and pre-amp tube distortion. I guess this would shorten the life of the tubes a bit, but they're pretty reliable electrically (just not mechanically) and I doubt any stomp box manufacturer would allow you to set a level so high it would cause damage.
Jim
'98 Jem7VWH
'91 Jem77BFP with GK-3
RG470FMR
Charvel EVH Art Series (red/white/black)
Burns Brian May
Epiphone G-1275 double neck
Epiphone Sheraton II

Laney VH100R
Boss GT-8
Roland GR-30
Roland VG-88
etc. etc....

[Big Red]

Thank-you for the thorough response Vim. That helps me a lot.


Cheers