Anyone used these things before ? are they any use ?

[bencat]

Saw this on e-bay and have to admit not seen anyhting like them before .This is porbably just my ignorant and sheltered upbringing but do not hold that agianst me. So do these work effectively and are they a good idea ?

http://www.ebay.co.uk/itm/Vintage-Valve-Sleeves-Aluminium-x1-Screening-Cans-ECC83-ECC88-EF184-EZ80-/161074804893?pt=UK_Sound_Vision_Valves_Vacuum_Tubes&hash=item2580ce789d

 

[Valvebloke]

They are electric (not magnetic) screens. So they will shield sensitive valves, typically input valves, from any stray electric fields. Sometimes this can help reduce hum pickup, particularly in preamps. They can also be useful in valve radios and TVs where RF pickup/leakage is an issue.

But you will need a suitable valveholder i.e. one to which they will attach (usually these have a 'skirt'). And the valve will inevitably run hotter inside this can than it would without. This can shorten its life and may, under some circumstances make it noisier ! Morgan Jones is pretty rude about this type of screening can in his book Building Valve Amplifiers. They work a little less badly if they're blackened since that helps with thermal radiation. But the convective cooling is still largely eliminated.

VB

 

[naxos10]

I have used something similar but they were the black ones mentioned in Valvebloke's reply above. Seem to have a small effect on noise and may have added a little bit of physical damping ( I had a 'singing' valve in the preamp section.

The inside gripped on my valves via a number of metal strips inside the can acting like a spring clamp on the valve.

BR

Alan

 

[rabski]

As VB rightly says, they need a specific valve base to attach to.

They were initially intended for RF applications, where external interference can be a serious issue.

Frankly, though others may disagree, they are pointless in audio designs unless the design is poor in the first place. There might be a potential application in extremely low-level high-gain applications such as an active MC phono stage.

If you have a seriously microphonic valve, change it.

 

[ERICLIMPIT]

I have these fitted on my mono blocks and have used them with and without the sleeves in place, not surprisingly there is no discernabe change in the sound whatsoever, though I do now run them without purely to aid cooling the valves.

 

[bencat]

Thanks think I will gi e these a miss and stick to the silicon rings already fitted to my pre amps valves .