Siegfried Meier said:
32 preamps, so a bit of a pain but I will check this out when I get back to the studio.
For what it's worth, this reply just came in from Cloud Microphones:
Hello Siegfried,
Yes, the Cloudlifters are very good at canceling hum-field and other
noise from long cable runs. Certain dynamic and ribbon mics will pick
up RF/EMF in certain environments, due to the magnetic structure and
(sometimes) lack of sufficient grounding or hum-bucking wiring. The
CLs phase out the noise due to the matched dual stage JFET amps on
both the +/- side. By the way, we just started shipping a new
Cloudlifter CL-4 four channel rack unit, ideal for professional
installs.
I'm glad the Cloudlifters have helped you with this problem!
Best Regards,
Rodger Cloud
Ah...manufacturers!
He forgot to mention it cures ingrown nails
But seriously.
Dynamic or ribbon mics do not pick up RFI/EMI.
It's the preamp that receives RFI/EMI and eventually rectifies it into an audible form of noise.
The Cloudlifter is probably relatively impervious to this phenomenon. It's 20 or 25dB of gain help the signal overriding whatever noise is on the line. No magic here, just an application of the well understood notion that low-level signal path must be kept as short as possible.
One thing they mention is susceptibility of said electrodynamic mics to external magnetic field.
If that was the culprit, the tell-tale sign would be that hum changes with orientation, which does not seem to be the case. Using a preamp such as the Cloudlifter would not solve this issue at all, since the noise would be amplified as much as the desired signal.
Having used a product similar to the Cloudlifter, I can vouch that it is useful at solving specific problems such as noisy lines, or providing additional gain for weak signals.
In my case, I use it in conjunction with a crappy ribbon mic that has an actual impedance of 2500 ohms, although being labelled 200!
As a conclusion, I would say that a preamp system such as the Cloudlifter is not a substitute for a clean wiring. I really suggest you check the line noise, with proper equipment and a 200 ohms dummy load.