Preamp Metal Can Shields

[Structo]

I read somewhere that the can shields we commonly use on preamp tubes can alter the tone by changing the characteristics (capacitance?) of the tube.
Hocus pocus or fact?
Do you guys typically shield your pre tubes?

[rfgordon]

I never use shields. As for changing tone, it can have an effect, but I've found it varies with the amp and the tubes involved. Sometimes the can makes the highs seem a bit dull.

[Richie]

depends on the amp, some amps need to have them ,some work better witout. Sometimes with a shield on, it can cause a squeal..and sometimes with one removed it can cause a squeal. I know it sounds crazy, but it matters on the tube used etc. Sometimes you have to try with and without and see if it hurts or helps. Its als better to use a black shield.

[Phil_S]

I only had two spares on hand, but they cut the noise on my TWX variant by quite a bit. As someone else said, the effect varies. It's always worth trying. I tend to use sockets in the pre-amp positions that keep my options open.

[David Root]

I use sockets with shields. +1 on you never know. The most common problem is they can mess up high end harmonics.