Shielded or Unshielded

Shrapnel · Post by **Shrapnel** » Sat 04/04/09 2:53 am

Is the general consensus to run the preamp tubes shielded, or unshielded? Or does it just boil down to proximities?

Post by **zaphod_phil** » Sat 04/04/09 6:56 am

I normally run them unshielded in my own amps. I actually once read a technical note from the BBC which said that cans aren't good for tube ventilation. Anyway, amps I build for customers have the shield cans, mainly to guard against the tubes falling out in some unforeseen circumstances, and especially in combos with the tubes hanging upside down. For my own amps I use a small blob of silicone goop at the base of the tubes to keep them in place.

stevesuk · Post by **stevesuk** » Sat 04/04/09 7:31 am

I experimented with both, on and off.
In my cage amps it would have spoilt the view. So I leave them off and use wire retainers for double security. I send the amps with the valves in place and the retainers on, never had a problem yet.
Steve UK
www.valvepower.co.uk

Shrapnel · Post by **Shrapnel** » Sat 04/04/09 10:37 pm

I was thinking of a layout w/o the shields, but was just checking. I'm thinking of about 2" between the tubes (translate: approx. 2.75-3" centers.) Probably wouldn't want them spaced any further apart anyway.

Steve, are those modified EL84 types, normal sized, or ready-made sized for the shorter valves?

Z_Stingray · Post by **Z_Stingray** » Sat 04/04/09 11:30 pm

I like'em open. It's a shame to cover those beauties with a useless shield.

stevesuk · Post by **stevesuk** » Sun 04/05/09 4:36 am

The retaining springs are purpose made for 12AX7's
They took a bit of finding, but they are the same style as the EL84's, they fit the ceramic valve bases (22mm hole) which are good, but terminal holes could be bigger.
Steve UK
www.valvepower.co.uk

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Shielded or Unshielded

Shielded or Unshielded