NooB question about tubes

[Ailean]

Hi all

First let me say 'Hi' as it's my first post on this forum.

I'm currently awaiting the delivery of my VH4 and H412R, the cab is still in Germany, and possibly not even built yet! Hurry back from Frankfurt boys! (but enjoy yourselves while you are there )

Anyway, my question...

The VH4 is an ex-recording stock unit, and I don't know what power tubes it has, or how old they are or how hard they've been worked, so I figure I may as well drop a new set in there.

I've ordered a matched quad of these (I'm liking the sound of the cleans
http://www.watfordvalves.com/product_detail.asp?id=1317

Now I know I'll have to re-bias the amp (Bias rite on order too), but will I need to make any other changes? These tubes are rated at 35W each so there is going to be an overall power increase I imagine.

 

[petereanima]

as far as i know, there wont be a power-increase because (i'm not a tech, but thats how i understood it) because you dont run them on full power.

 

[Ailean]

Hmm.. good point. But I see in the VH4 specs that it will take KT88's and they make the amp 150W ? Or am I reading that wrong?

 

[MARK2C]

I don't think you will see to big of a volume increase with 7581A's.
At least I did not. I did bias them as a 35 Watt tube though. I still prefer
the SED 6550 over the Phillips 6L6GC and Phillips 7581A. Very punchy,
neutral and yes, a bit louder. You might want to ask Diezel what tubes are in it.