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Thorsten wrote:

If you do, do seek out old Air dielectric AM tuning Capacitors. You only need 110pF & 330pF, both can be found suitably. Once you tuned the RIAA to perfection simply superglue the shaft in.... I used to use that trick in prototyping in the old days when tuning Op-Amp compensations and found circuits sounded better with those "Air Variable" capacitoirs than they did with good quality polystyrene for stabilisation.

Brian,

I sourced the air caps from here:

http://www.oselectronics.com/ose_p96.htm

The AVC150 does a wonderful 110pF (I run it 112pF) and the BC14400 does good as 330pF. I did not lock them up but I do not shake them. The AVC150 has very stiff shaft, the BC14400 is very loose. However, I did not see that it drifted, although the corrector once was flying around in my car.

The only thing that you might want to do would be does not let the signal go via the bearing of the shat. In order to do so you would need to solder one contact to the default leg, however theanother one - do not connect to the chassis of the cap but to solder it to the movable plates. They are aluminum (you won’t find any cupper-made variable caps for 350pf) but with a strong solder gun (I use 200W) and long heating the thin aluminum will be solderable. Put some solder in the topmost movable plate, melt it, dial in the correct position of the shaft and then accurately solder a thin wire.

Be advised that although the 110pF EQ HF and 330pF EQ LF but it work reversing for sonic benefits. Changing of 110pF form polystyrene of mica to air (with the same value) will severally affect the quality of bass. Changing the 330pF form polystyrene of mica to air will very-very-very-very strongly affect the cleanness of HF and upper mid range.

Be carefully through, if you try those air caps once and recognize what they could do then you will stick them everywhere! I’m sticking them into my power amps, in any unnecessary and all-imaginary places, I try them on Cat and how I am working on a problem of a permanent attachment of those caps into my woman. I hope she will “sound better” after that… :-(

The caT

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