valve dilemma

[Baxter]

Im selling an old roost combo guitar amp. Now its got two working mullard el34s in it. Do I keep these and swap them with the electro harmonix ones in my Selmer tnb before it goes. Obviously Ive not advertised the roost as having these valves in it.

[franzbassist]

Why not sell it with the EH ones fitted and offer the Mullards as an "upgrade" for £x extra?

Unless you plan on keeping the Mullards for something else?

[Mr. Foxen]

Can you bias it to suit the other valves? Can you test the mullards?

[spaners]

[u]dose it sound any different with the mullards in there ? [/u]

[Mr. Foxen]

[quote name='spaners' timestamp='1376331343' post='2172301']
[u]dose it sound any different with the mullards in there ? [/u]
[/quote]

It will do if it isn't bias right for the other set. Or if any of them are clapped out.

[Baxter]

the valves in both amps all seem to be working fine. is it a bad idea just to swap the valves over Mr Foxen?

[Mr. Foxen]

Plain swapping power valves sort of works, but the bias won't be set right, which compromises sound or valve life.

[Conan]

How does one go about biasing valves?

[paul_5]

very, very carefully. Best leave it to someone who knows...