Valve Advice

Ive been using a valve pre for a few months now and im very pleased with the results....however, I got 5 freebie valves with it ( ecc 86 /6gm8 in various stages of hours used, but all the same make. I know nothing of biasing and the pre has a vol control for both outputs, so im not sure if this matters ???? What i really would like to know, is ...how do I tell from the 5 identical valves ive been given, which ones are on their last legs and which are new? do they have to be matched in any way? ( i often read on here "matched pair" ) what if they arent a "matched pair" and how would i know....thanks banpe

 

The valves in the pre won't need biasing. Unless you have access to a valve tester it is very hard to tell how strong they are. Just use them and don't really worry too much about it.

It is usually the valves in the power stage of the power amp that need biasing. This is usually achieved by auto biasing, which means it is user adjustable, and this is where matched pair/quads are recommended. There is also manual biasing where you can use any valves of the same type and bias by hand using a multimeter.

 

Hi Banpe

What make are they?

Is it a basic pre from China, or a second hand something else?

Sometimes basic pre's from China come with very sonically not-that-great tubes - just to get you going so to speak.

If they are decent ones I personally would just sit back and enjoy.

 

theyre amperex i think...ive just ordered some telefunken from ebay....colomor...but ive been advised not to buy off ebay....why is this? a few people have said this now

 

oh I think that's a bit of a blanket generalisation ''dont buy on ebay''.

I'm sure there's tat on there, but for example Langrex Supplies have an Ebay shop aswell as being a normal audiophile/guitar tube supplier.

I'm afraid I don't know the Amperex brand, so can't say much about them. I'm sure someone who knows more about tubes on the forum might be able to say.

 

I think the Amperex 'bugle boy' valves are quite highly regarded from what I've read on the web, not sure if it applies to all Amperex valves though.

I've bought valves off ebay without any problems, from private sellers and dealers, so they can't ALL be bad!