Croft valve rolling question

[Bigbird]

Hi guys hope your all well.

Im after a bit of advice from any Crofties or valve experts.

Ive got the croft 25r with upgraded linestage
And the 7r monos.

After speaking with a few people the unanimous decision was that rolling the linestage 12bh7A will alter the sound the most and that the 50s NOS RCA valves seem to be most peoples go to choice for best of the best valve. It already has a nice nos Sylvania in there but i fancy a bit of fun to see if i can taylor the sound a bit more.

Others also recommended that swapping out the line in valves on the monos has a nice effect. To get the clean detailed sound that i like i had been recommended the Nos GE 5751 in this position BUT luckily i took the top off to have a check as the valves in this position are also 12bh7A not ecc83 or variant types.

Ive pulled the trigger on a nice(but expensive)pair of 1956 RCA black plates, NOS and matched and super strong. I will also pick up one more at next pay cheque to complete the trio that i need.

Anyway enough rambling my question is, has anybody tried any different valves in the other positions?
The rest of the valves in the pre are a Mullard 85A2 and 2 JJ ECC83S

And one ECC83S and one 85A2 in the two mono.

Will changing any of these effect the sound or are they just for power regulation? Its all new to me so not sure, and dont want to spend lots more on top NOS tubes if its not going to make a difference.

Thanks for any help

Karl


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