Westcam FCBI 2030 Jensen 990 Hardy M-1 mic preamp

I recently came across this on fleabay and picked it up. It was manufactured by Westcam Industries Inc., probably 1984-85. I've done searches to find similar but it seems like maybe it was a one-off. This was 1 module within a rack of 8, it has serial number 108. The 990 has the load termination isolator built in, and while modular, does not follow the typical 990 footprint.

The schematic is nearly identical to the Hardy M-1 with just a few minor resistor value differences. The gain adjustment is on a switch between 6.4 or 16.4dB. I would like to rack this up and add an 12 pos grayhill switch instead. The feedback resistor is 1020R so the shunt resistor is also a much lower value. I've calculated 4dB gain steps from 6 to 50dB. I'll try it out but does anyone see a problem with this setup? Still working on getting the parts for the +- 24 volt power supply for this so haven't run anything through it yet.

Gain steps and shunt resistor values similar to Hardy's M-2 switch:

resistor value/gain/(ideal calculated total resistance)
549/6/1020
215/10/471.72
107/14/254.25
59/18/146.9
34.8/22/88.013
20/26/53.818
13/30/33.309
7.5/34/20.766
4.7/38/13.005
3/42/8.102
2/46/5.138
3.32/50/3.236

I'll replace the electrolytics and use 3 of the output Tx for something else.

I wish I could find another to rack up a stereo pair (or possibly a DIY M-2?) while I'm at it.

Westcam photo

Front view

990 close-up

Nice, what you are proposing seems absolutely fine to me.

One caveat - dump those "Purple" capacitors for some new ones ... '84 was a while ago !!

I had several of those caps on Telefunken and Lawo modules, best to replace them I was told.

Marty.

The opamp (if not the entire module) is probably made by http://www.soundsteward.com/, a very nice guy.

Samuel

Nice pre!

How many outputs are you going to use from those 4? I have a couple of ides where all the unused can end...

JS

I'm using only 1 of the three. I already pulled out 2 of them to use in my PRR-176. Only problem is that they don't have the transformer wrap-around metal part with holes for mounting. I'm sure I'll come up with something.

Samuel Groner said:

The opamp (if not the entire module) is probably made by http://www.soundsteward.com/, a very nice guy.

Samuel

Click to expand...

It seems like it's very well made. Looking at the documentation, it's hard to read, the schematic has what looks like "Applewhite" and a first initial I can't read. There's also the initials "KPJ" on the spec sheets along with the date 6-25-1984.

kramerb1 said:

I'm sure I'll come up with something.

Click to expand...

;D Zip ties

Very nice looking pre!

Nice catch! The design looks very clean.

I would interested to know why on earth would anyone design four separate low impedance transformer outputs to any preamp. Was he running out of storage space or did Jensen used to be very inexpensive?

[edit]

or perhaps it was a requirement for a very hostile remote TV studio type environment.

Yea seems like overkill, or designed for a very specific purpose, I know I wouldn't mind a pre with 4 transformer isolated outs, For overdubs, like tracking vocals or something I could have one clean, one smashed with an la2a, a vari-mu and a 1176.  8)

It could have been for press conferences? One mic, four TV stations recording the signal? Just a thought.

> why ...four separate low impedance transformer outputs to any preamp

It's not a mike preamp; look at the gain. 6 or 16dB.

It is a Distribution Amp.

I've had DAs with 16 outputs. Typically four transformer-ed; the rest of the loads were in-building and benign, but hostile or long-line loads really favor transformers.

Another clue. R14 R15 add to 82 ohms. The 990 can drive 75 ohms clean. So any _one_ load can be DEAD-shorted, and the others will be unimpaired. That's typical of a *serious* distribution amp in a well controlled facility. Shorts happen, but loads B C D *must* continue to get *perfect* audio while load A is digging a backhoe out of their cable.

A wise man, writing about larger more chaotic distributions, suggested that a DA should tolerate "one-third" of loads shorted and the other loads not know there is a problem. I guess 1/3rd of four is very close to one. Or this distibution with just four loads was not expected to run two shorted loads. Even if it did, the resulting 42 ohm load (a bit higher because of winding resistance, plus any line-resistance from here to the short) "can" be driven by 990, just not all the way to 22V peak. If line level is nominal +4dBm and we assume +16dB peak headroom for clipping <0.1% of the time, the 990 can drive that into 40-some ohms. Not steady-sine, it may overheat; but on peaks sure.

This is very different from your vocal tracking. You have (better have!) a clean track which can be re-mangled later. Also your la2a,  vari-mu and 1176 are probably in the same room, little need for transformer lines. No, say the football game goes out *live* from Boston to NYC Chicago KC and LA. If the line to Chicago shorts, you prefer not to *have* to apologize to NYC KC and LA; indeed if the Boston-Chitown line can't be fixed quick you might end up patching from KC back to Chicago, *assuming* KC doesn't lose signal.