Okay well, to report back, I tried it and it did not really change much at all!!
I rolled in a few other sets of tubes to see if any differences could be noticed, and slightly less gain was apparent on the following combination;
Brimar CV4004, GE JAN 12AT7WC
This also sounds great (except for the first time I turned it on there was good deal of buzzing whilst turning the volume dial on low levels - although it went away after a while, any idea what could cause this?).
I will now head down the in-line attenuator path I think....
I rolled in a few other sets of tubes to see if any differences could be noticed, and slightly less gain was apparent on the following combination;
Brimar CV4004, GE JAN 12AT7WC
This also sounds great (except for the first time I turned it on there was good deal of buzzing whilst turning the volume dial on low levels - although it went away after a while, any idea what could cause this?).
I will now head down the in-line attenuator path I think....