Interesting audio circuit...

See nothing about FM; the closest maybe is phase modulation.

** See the words " FM modulator " ??

You must be totally blind.

..... Phil

** That is EXCELLENT !!

Thanks a lot.

..... Phil

"Jan Panteltje"

** Looks like that is just how it works.

Varying the ratio detector tuning with the mic capsule appears to give better s/n ratio than any simple FM scheme - while the NFB loop makes the whole thing far more linear at high SPLs.

Axolotyl posted a link to the patent which has lotsa detail.

... Phil

"Phil Allison"

** Some facts are now clear:

** Along with L1 and L2, they form a "ratio detector" or FM discriminator. ** The tuning point of the ratio detector changes - not incoming the RF frequency. ** Simple audio frequency equalisation for natural roll offs at the ends of the audio band inherent in the capsule design. ** That's how a ratio detector works.

** Sennheiser * never * made conventional ( ie charged plate ) condenser mics at all.

With the arrival of low noise Silicon transistors in the early 1960s, they developed an RF circuit that enabled a condenser mic's capsule to operate without the need for high voltages or vacuum tubes. Other makers simply adapted their existing vacuum tube condenser mic designs to use low noise FETs - when they arrived later in the 60s.

Sennheiser are still the only known maker of RF condenser mics - and rightly claim them to be in a class of their own for their combination of immunity from weather conditions, near perfect polar and frequency response curves and very low self noise.

.... Phil

On a sunny day (Mon, 16 May 2011 11:21:00 +1000) it happened "Phil Allison" wrote in :

You really need help with your head.

On a sunny day (Mon, 16 May 2011 13:20:53 +1000) it happened "Phil Allison" wrote in :

I am glad you got it now, sorry if I was rude.

Yea, well, I was wondering if anybody could get away with patenting negative feedback.. Looks like they can.

"Jan Panteltje"

** I have already taken back the above remark.

Get over it.

.... Phil

Phil Allison schrieb:

[...]

That's right - until now:

Bye

Reinhard