JR. wrote:ricardo wrote:JR. wrote:I am not very sure what exactly are these hurdles. Are you talking about current leakage in the 48V blocking caps as the P48V problem?
I think current leakage can be solved with the right Electrolyics and perhaps leaving P48V on all the time.
And is protection another source of noise? Perhaps some series R to limit current ?
Yes. 0.6nV/rtHz (Earthworks spec) is Rnv 22R36 which is nearly taken up by the 2x10R series protection THAT recommend.
Of course my STC 4038 example is a red herring cos it doesn't need P48V. It's then straightforward to get well
under 1nV/rtHz short circuit noise with a dedicated ribbon mike amp. using
Cohen without any P48V and protection.
But the 4038 ribbon is a passive nominal 200R source. The important noise spec isn't Short Circuit Noise (spec'd by Rnv) but Noise Factor .. how much the preamp increases noise above the theoretical noise of a 200R resistor (1.82nV/rtHz). THAT 1510/12 can get within 1.3dB of perfection for this.
My guess is Earthworks use the Cohen circuit. What I can't figure out is if it is immune to shorted cables on one side with P48V connected. Their stuff is encapsulated.
One could argue the 0.6nV/rtHz Earthworks is overkill. I can't think of any P48V mikes that would benefit from 0.6nV/rtHz over the 1.6nV/rtHz or so of a competent THAT 1510/12 P48V design. It's also not quiet enough for the, once common, 30-50R nominal dynamic/ribbon mikes .. for which I've got my own variant of a Cloudlifter type device.
But 0.6nV/rtHz isn't harmful PROVIDED it doesn't compromise protection against The Phantom Menace etc.
BTW, for the wannabe LN gurus out there, 'straightforward' & 'competent' doesn't mean 'easy'. Your PCB layout, earthing, decoupling & other skills need to be first class to get the above numbers.
think the government has stockpiled helium, not sure where it comes from and too lazy to google it.
I believe the USA has more than 90% of the World's known sources of Helium.