Hi Tim,
This seems a very odd beast indeed. Serial number 502 is not so early
as to be a prototype and it should have a full Calrec control unit with mic
inputs, matched A/B module, B Gain module, metering module and so on.Our
own mIII CM4050 is somewhat newer than this one, but I have a control unit
for mic no. 571, which is not much more recent and that has all the
facilities (I was given it by Mike Beville of Audio Design as redundant
since they no longer had the actual mic) .
This sounds like something somebody made from a mic head and their own
electronics, though I can't conceive how you would make a passive A-B
module, because of the filtering needed. Howard Smith at Calrec did do a
few deals with people where he sold individual system components - we got a
mic head, mic pres and the matched A-B module which I put in our own box
with a UHJ encoder board, plus a decoder, four channel metering (preceding
that on the later versions of the mic by several years) and digitally
controlled attenuators instead of a pot for gain control. However, I can't
understand anyone not getting the matched A-B unit with the mic head as
they were tested and aligned together, so the mic, I believe, wouldn't even
have been produced without it.
Dave
On Dec 12 2010, Tim BC wrote:
I have been fortunate to be the steward of a Calrec CM4050 microphone
and related accessories for the last 18 months or so. Sadly I have not
been able to do much with it, partly due to a lack of adequate time and
partly due to a slight mistrust of the mains power supply. I am about to
return it to its rightful owner.
From its appearance and low serial number (502), I suspect that it is a
prototype particularly as the pre-amp is covered in handwritten notes on
masking tape and the connectors are RCA phonos and TS 6.35mm jacks. The
connector on the base of the microphone is a 6-pin male XLR. The
connecting lead is a 6-pin XLR-F to four TS 6.35mm jacks and is about
1m80 long. This lead is connected to a pre-amp with coarse and fine gain
switches and then to what would appear to be an A-format to B-format
converter, the outputs of which appear on 2 sets of 4 RCA phono sockets
marked NOPQ. I have not had the courage to open the cases to investigate
their contents. The mic-preamp is mains powered and I suspect provides
the polarisation voltage for the capsules. The A/B converter appears to
be passive.
Also included was a Calrec Surround 1215-02 module which is dated
30/06/81 and marked with the engineer's initials, RL. On the front panel
is a dual concentric switch/potentiometer and a 2nd pot. The switch
selects mono, stereo, Quadruple, Ambisonic and B (-Format) [my
parentheses]. The concentric potentiometer would appear to vary
infinitely the output configuration from wide width/shallow depth
through square to narrow width/deep depth. The second potentiometer
controls the output level.
I have taken some digital pictures and would happily post them if
someone could let me know how to do this. If anyone can provide any
details or history of this highly original microphone, I am sure the
owner would be delighted.
Season's greetings to all
Tim Boissaud-Cooke
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