Thread: Why a peltier in Sony C800 mic???

I'm not trying to split hairs, but just so no one gets confused the Peltier device is on the C-800G, not the C-800.

I read in some Sony literature several years ago that the device helps reduce the mic's self noise. I've also heard it may help with the 6AU6A's microphonics, though I think that was someone's opinion, and not something I read. I personally don't understand it much at all. I'd love to know more myself.

Peace

I actually measured the noise on several of these with the peltier connected and then disconnected. I found a max 1.5dB improvement. But when the noise is already down somewhere around -122 anyway
thats quite an improvement. I think the BIG secret
is the tube. They call it a 6AU6 but its not. It
has a larger envlope (aprox .187 taller) than any
6AU6. I tried subtituting all types of premium grade 6AU6s GoldAreo, Telefunken equivalents ect and the noise when up 10 12 dB from the original tube. (if anyone really knows what tube it is, Let us hear from you). Anyway it's a very good mic with a very transparent sound. BTW the 800G
was developed by an amature audio enthusist in Japan. The last I heared SONY hasn't paid him anything for his idea. This may not be so it's just what I heard from the SONY rep.

posted by Gus 08 November, 2003 23:27 *** ** * ** * * ** **
------------------------------------------------------------------------
I was looking at some triode curves of the 6au6. I found the chart at frank tube page the GE one has one graph triode connection.
It looks like the PS might be <=300VDC. Why do I think this? One it would give a little more than 60v to the capsule 288v would give 60v. 2ma in the plate would give about 200 V dropacroos the 100K plate R, 2ma would give about -2 grid bias
2v drop across the 1kcathodeR
The -2v curve crosses 2ma at about 95V at the plate. If they used the u67 circuit for inspiration maybe they set the grid bias at -1.8V for 1.8ma tube current.
Could/would someone else check my math. From the triode curve it looks like 295V would be the right voltage 200V drop on the Plate r, 2V drop cathode R -2vbias, 95V at the plate.
I have not heard a C800G yet some people like it. I just bought a LL7503 big and can be wired 8:1. FWIW tend to like the non sound of big well made transformers.

Looks reasonable to me, Gus (but my knowledge is limited). Does someone have one that they can measure to check this out? The mic seems over-engineered to me. I think they are going for super-quiet with the super caps and peltier etc. Looks like a lot of current wasted on the capsule polarisation circuit (compared with other mics which use many megs or even gig resistors). Why use 300V PSU when you only need 100V at the plate?

I've just popped a 6AU6A into my MXL2001 guinea-pig mic for laughs. Will let you all know how it sounds.
Stewart