Mic Circuit housed in separate enclosure?

[Wordsushi]

Has anyone tried this? Long story short, I have a mic body that used to contain a very small schoeps circuit crammed into a very cramped compartment below the headbasket. The circuit is kaput (it was a bit noisy anyway) and instead of trying to replace it with something as small, I was thinking I'd use a better circuit housed in a separate enclosure. So it would just be capsule in one unit and circuit in the other. I realize this means a much longer connection between circuit and capsule, possibly with connectors involved, so my question is if anyone has any tips.

I'm going to try it just for fun anyway because it just seems like if I could make it work, I could theoretically create other headbasket enclosures with a capsule in them and just connect them modularly to the circuit.

 

[SparkleBear]

My hunch is that the high z signal coming off the capsule should be as close to the impedance converter stage as possible. Maybe with adequate shielding there is a way? I’m not the expert here..:

Question: the schoeps two part mics with the capsule that hangs far from the body— do those have electronics behind small capsule assembly too? Before the wire run… noticed those at the sf symphony hall and started thinking.

 

[rock soderstrom]

It works somehow, but the distance between capsule and amplifier can only be increased to a limited extent, as this is a very high-impedance matter.

The better strategy would be to split the amplifier circuit into two parts. This means that you put the FET directly on the capsule and place the rest of the components elsewhere outside of the mic body.

https://groupdiy.com/threads/lets-talk-about-capsule-holders.83224/post-1076675
https://www.soundonsound.com/reviews/schoeps-v4u

 

[bremusound]

You could use the Schoeps KC circuit, it can be found in the CMC5 schematics

 

[Wordsushi]

Ok, I figured out a way to do it. Using an old capsule box to house the circuit. Cut a small square of mesh that I put on the bottom of the capsule box to make it a faraday cage and it's working, no noise, and I can use the original leads from the capsule without extending them. I just have to attach this piggyback to the mic.

Thanks all for your suggestions. It helped in figuring out how to keep it close to the body. As you can see in the "before" photo there is a JZ V67-like cutout in the chassis that limits the space inside. I'm sure I could have just created a new small circuit for it, but I already had something I wanted to use. BTW, this body is from a BaiFeiLi V10 off Alibaba.

 

[TLRT]

Gefell made this in their first mics after ww2, check GNM14/M14, there was the capsule+tube together, then the mic amp in separated box,and then the PSU. I had some,and when the mic works it sounds good.

 

[kingkorg]

Yes, usual solution for this problem is placing the fet and hiZ resistors together with the capsule. This can be easily, and elegantly done with smd components. Se Electronics GM10 uses this principle among others.

 

[bleepblopblipbloop]

Henry Spragens points out (here: Measurements (again)) that charge amplifier circuits do better in this situation, as they avoid the parasitics that can arise when the transducer is located farther away from the impedance converter circuitry. Really a great discussion in general, as with most of his stuff.

 

[GeorgeToledo]

AKG also had extender tubes for several of their modular microphone, such as the 451 and earlier tube based models. These increased the distance between capsule and electronics.

I think many early tube mics existed that placed the output transformer in the PSU, on to later mics like some Sony tube models. Maybe some still do.

 

[panman]

I think many early tube mics existed that placed the output transformer in the PSU, on to later mics like some Sony tube models. Maybe some still do.

AKG C60 is like that and then of course there are Hiller M59, M60 and M58, that have the electronics and trafo between the mic and PSU in a "Zwischenverstärker"(between-or midamplifier). The mic part on those only has the tube and a 7 G ohm resistor in it and the cable from the mic to the midamp functions as a capacitor and is thus part of the electronics. So the length is critical in order to have the correct capacitance, because otherwise the frequency-responce is affected.

 

[rock soderstrom]

AKG also had extender tubes for several of their modular microphone, such as the 451 and earlier tube based models. These increased the distance between capsule and electronics.

I think many early tube mics existed that placed the output transformer in the PSU, on to later mics like some Sony tube models. Maybe some still do.

Most tube microphones with split/external electronics are cathode followers. With anode out impedance converters this is more difficult to realize.

 

[Lampie519]

You could add a cathode follower and use its output as shield for the anode out signal....