Safe to try out some E34Ls from a Peavey XXX in my Mark IV?

[dolinja]

Hey all, As mentioned in a post two days ago, I'm a new Mark IV owner. The amp that I got has all 6L6 power tubes, but I'm pretty interested in switching the outer tubes to the EL34s. My previous amp was a Peavey XXX combo, and had it tubed with JJ E34Ls from Bob at Eurotubes.

So the question is whether I can simply take those tubes from the XXX and put them in the Mark IV or whether I should order a new matched pair that were specifically for the Mark IV bias. I know Bob selects the tubes specifically to match the current draw of the amp you are buying them for, so how far off is the Mark IV from the XXX?

Any opinions?

 

[dolinja]

So it turns out that the tubes I had in the XXX were JJ KT77s, not actually EL34s. I read that this was also safe (I'm not 100% sure about that), so I gave them a shot, and they sound glorious. Thicker, bassier and more compressed than the all 6L6 set that I'd had in there. Of course this can also mean that the tubes that were in there when I got the amp weren't quite as new or good as the previous owner told me.

Anyway, is it safe to keep the KT77s in? Anyone have an idea about how the EL34s would differ from KT77s? Thanks!

 

[stokes]

If the tubes are not red-plating and they sound good to you,then you are good.

 

[dolinja]

Hmm, they may actually be red plating. They at least glow quite orange.

I've typically (on weeknights), run the master super low so I don't get my neighbors all pissed off. So I've obviously been putting most of the work on the preamp tubes.

This morning I just tried an experiment of running in tweed mode, keeping the channel volumes down and pushing the master up, and something is definitely wrong on R2 and Lead channels. The volume gets louder and softer. And bringing the master back down that problem went away.

Anyway that experience is enough for me to go and order a full JJ retube kit anyway with the E34L matched pair. The amp was used, the previous owner said the existing tubes were in good shape, but I probably should have just switched them out anyway.

 

[stokes]

Do you see the plates get brighter red when you have the volume fluctuating?Is tit actually the plate you see glowing,or just the orange glow of the filaments?