Topic: Schoeps CMBI's - Protecting from DC Potential

[hi and lo]

Ok, need a little advice on the best way to run my CMBI's into balanced inputs that may not be free of dc potential.

For those than don't know, the dc voltage seen at the cmbi output must not exceed +-6v (with battery installed) and measuring my dr-680 or psp-2, both do. The 680 is always around 8.5v not under load while the psp-2 is much more. Once phantom is engaged, the psp-2 will remain at 14 or 48v until a load is applied. If you remove the CMBI battery, it is possible to externally power via 7-13v dc, although I believe I would need to re-wire my cables.

So I think I have two options, both of which might be equally acceptable, but would like some advice.

1) Build a simple dc blocking circuit in a small project box. This is really nothing more than two large capacitors (>= 2.2uF and rated for at least 50v) which blocks all dc from the CMBI's output. The major obstacle is that metal film capacitors of the appropriate capacitance and dc voltage ratings are very large; probably too large to use with an in-line cabling solution. So, I'd have to put the capacitors inside some type of enclosure. If I could build them into an inline cable, that would be great, but I don't think I can do so without using non-metal film caps.

2) Use something like the Naiant PFA to reduce phantom powering dc from 14-48v down to 9v and re-wire the K 5 ISK and KIY 250 cable I have to provide power to the CMBI's. I think this approach is more elegant as I can ditch the internal 6v batteries which are somewhat expensive and prone to dying if I forget to turn off the CMBI's.

All this would be a moot point if I got cmc6's, but sonically there's really no disadvantage to the CMBI's for what I record and have been extremely happy with the tapes they've made. So, maybe there is an alternate solution I've not thought of?