tube preamp with hum??emf

[prorms]

i know hum come form the wire that lead in to the socket iam just using regular wire with plastic covering copper wire
i know that copper and aluminium wrap around out side can stop it but be hard with the socket pin be that close together what kind of wire think i should get to stop the problem if that what it is also when put a sheet of copper near these wire hum louder with ground the sheet of copper its a 12au7 tube

[dsavitsk]

http://www.correctpunctuation.co.uk/

[kevinkr]

The pre-amp should be built in a fully enclosed metal box, shielded wire is only necessary in extremely low level circuits and would be of benefit only on the input to the first grid.

Tightly twisting and routing filament wiring away from sensitive low level circuitry helps as does generally good construction and grounding practice.

I highly recommend Morgan Jones "Building Valve Amplifiers" for good construction technique, and his book "Valve Amplifiers" for a path to a basic understanding of how tubes work. They're both available from Old Colony Books online or Amazon.com. Worth the money and worth a read..

And oh yes, Doug is right - your post is indecipherable as written. We all want to help, but decent grammar and punctuation make it much easier on the rest of us, and particularly those in the crowd who are not native English speakers.

[kevinkr]

Grid stopper resistors in series with each grid connection mounted right at the socket would be a good idea. Your amplifier circuit might be oscillating.. 220 ohms ought to be enough.

How about some pictures of your project and a schematic that we can see? Details on power supply would be helpful too.

[prorms]

put a 220 ohm between the 2 grid before the first 0.1uf and second grid
thxs