Mechanical decoupling of microphones and their capsules and tubes.

[rock soderstrom]

Also silicone O rings around the tube are effective.

Really? I think they have less effect because the internal structure of the tube is microphonic, not the glass.

Check these out, good for mounting the tube socket or anything that needs vibrational loss.

Yes, they look good.

 

[MicMaven]

I wonder whether anyone has investigated Sorbothane or other such materials that are sometimes used in structures to isolate from vibration?

Yes. The HEIL PR35 micrphone and HEIL Handi Mic are both supposed to have sorbothane internal mounts to reduce handling noise. ... or so they say! Ham radio operators have used these for years. James

 

[Cqwet Dbdfte]

There is no magic bullet for vibration damping, some thinking and experimentation is needed. Adding mass to a spring will lower the resonant frequency. Making the spring (including elastomeric parts) harder will increase the resonant frequency. Power transformers are noisy, to some degree, and potting them in wax, tar, and dry sand have been used to reduce that effect.
The original 47 condenser mike from the 1930's made by Western Electric had a cast 6lb. brass body. We can guess the reason.
( that mike also had a separate heater lead and 200V plate supply, plate current ran thru the output transformer).

 

[Tubetec]

In my experience an O ring or two around the tube does help brace the internal structure a little better ,
I think the red silicone O rings are best , there made for higher temps , the black is only rated to 150C .

 

[Cqwet Dbdfte]

Tube sockets with shields add mass and may help.

 

[Tubetec]

A sheilding can around the tube will make a difference to the incidental capacitance ,
Heat dissipation and air flow may also be effected by the presence of a tube shield .

In one mic I made I used aluminium tube with an ID very close to the tube diameter I was using , it turned out some versions of the EF86 wont fit in , the Mullards fit , the later East German/Russian varieties dont .
The aluminium part the tube fits into is bolted to the the frame ,so has a chance to dissipate heat by conduction .

You do see some better domestic tube gear with very close fitting mu metal tube sheilds , they have a short lenght of braided wire making the 0V bond at the appropriate point in the circuit .
Tube reel to reel players from Tandberg have it , the reason is that both a motor and power transformer are in close proximity in a tape machine ,so extra precautions need to be taken to exclude the AC feild .

Anyway in the context of a hi-z tube mic the proximity of the tube screen will have an effect on the tone , it might be favourable or not depending on what your trying to achieve .

 

[Cqwet Dbdfte]

Added capacitance yes, main use for shields is for RF, but the actual numbers do not add up to much. Mike tubes are often metal cans anyway. Correct with sizes, Russian Noval tubes I've seen have a larger diameter.
Metal cans do add mechanical rigidity to the tube.

 

[metalockpick]

I wonder whether anyone has investigated Sorbothane

 

[rock soderstrom]

There is no magic bullet for vibration damping, some thinking and experimentation is needed. Adding mass to a spring will lower the resonant frequency. Making the spring (including elastomeric parts) harder will increase the resonant frequency.

True. My impression is that mechanical decoupling at several points with different materials (-->resonant frequencies) improves the result. I'm still experimenting...

 

[Cqwet Dbdfte]

Sorbothane is a great material, but do not expect miracles.