Crystal valve diodes for clipping?

[bancika]

Anyone tried those diodes for clipping? I've got few vintage NOS diodes marked "CV425 crystal diodes", I don't know what are they originaly for buit I guess it's about radio. Couldn't find any data sheet, but I measured forward voltage about 450mV
Tnx

[KerryF]

You mean the crystals for time machine? 

Could be the next clipping fad... but who has them to try it?

[bancika]

I've got for of them, so old that I can't find data sheet But never used
Will try them in my TS and get back with results

[Thomas P.]

How 'bout this:

Part Number = CV425
Manufacturer Name = Marconi
Description = Germanium Diode
V(RRM)(V) Rep.Pk.Rev. Voltage = 65
I(RM) Max.(A) Reverse Current = 1.0m
@V(R) (V)(Test Condition) = 50
V(FM) Max.(V) Forward Voltage = 1.0
@I(FM) (A) (Test Condition) = 4.0m
I(O) Max.(A) Output Current = 30m
Status = Discontinued
Package = DO-14
Military = N

[R.G.]

The diodes used for crystal radio sets are seen as valuable in proportion to how low a forward voltage they begin to conduct at. Normal germanium diodes are OK, but some of the special diodes for crystal sets begin conducting at very low forward voltgage. A "cat's whisker" set using a needle-pointed contact to a galena crystal is prized for this because it makes a point contact diode that begins conducting at nearly zero forward voltage.

The reason low forward drop diodes are useful here is that they directly rectify the incoming RF signal from the antenna. Voltages too low to forward bias the diode are not picked up at all. Some germanium diodes were made especially for this purpose, don't know about that particular part number. Conduction voltage picks up at higher currents, of course.

There is a device called a "backwards diode" that was used for this. It was doped in such a way that it began conducting slightly - enough for radio signals - at essentially 0.0000V across it in reverse. The normal forward voltage was used as a blocking voltage. It was great for crystal sets, but as you can imagine not many were made.

How will they sound? Gotta try them to tell.

[markm]

I heard George Harrison mention the "cat's whisker" radio set in the Anthology DVD.
Interesting.