New toy

going to get it right now…

A friend connected me with some folks who are disposing of a spotmaster broadcast console, going to get it right now, looks something like the one in the picture below, will post a pic ASAP:

Well, it’s a Broadcast Electronics 8S100A, 8 channel broadcast board with 8 stereo preamps cards with big transformers in them. I also got a Tascam 4 track R2R and some miscellaneous stuff.

Pictures tomorrow. :)

Sweet !

Don’t that look great… The one you’re getting… What vintage would you say it is? Give us some idea of it’s weight…


1979, in pristine condition, well maintained by a very good enigneer, weighs about 20 pounds I’d say. I can’t find a manual for it, although BE has a manual posted for the succesor model, the 150, on their website.

I have a feeling this is really going to sound good. The preamps are on separate cards, 8 stereo preamps, as I said, with big trannies. gonna find some schematics so you experts can tell me what to do. :)

Looking at that picture made me think a little… I bet they’ve replaced the “cart” machines and a whole host of other goodies with a PC or other dedicated hardware digital box. I use to “help” a buddy of mine DJ the night shift at a little AM station. We had a ball making all kinds of spoof commercials and gag recordings and slipping them in the cart machine during the wee hours when we felt sure the station manager would NOT hear them! :D

Have fun Tom. You are the ultimate scrounger man. You probably won every scavenger hunt you’ve ever entered… right? :wink:


this area is the greatest place to scavange in ever. :)

I got two cart machines as well. Cheap tape delay units, perhaps? :)

Bill, that is exactly what they were doing - going to computer based automation.

So, here’s what I know about the board. I will have pictures in a few minutes, but I’d sure like your input, Bill (or whoever).

The preamps are stereo, 8 of them, based on the LN748CN op amp. The trannies I saw are actually in the line amplifier and headphone amplifier cards (which look identical to me - is that possible?).

Data sheet on the LN748:

Pictures - what can you tell me, Bill?

That sure looks well made. I don’t fully understand the terminal strip in there, but…whatever. Stereo I/O was pretty standard on broadcast boards. Beyond saying “cool”, I can’t comment too much.

The cart machines are more than likely two head, and if so, they won’t work as delays. You need separate record and repro heads, and you need to be able to monitor record and repro independently for a delay. Many of those machines only have a sync head (record and repro on a single head). That 1/4" machine though…that’s a tape delay waiting to happen. If I do wind up seeing you in the next few weeks like we talked about, I’ll bring my 1/4" MRL and a few other tools and we could spend a little time dialing that thing in if you want. I like making old tape machines live again, and I especially like tape delays…

Hi Gents:
I expect that the terminal strips allowed the config. of how the various channels connected to the Monitor and Output busses… Maybe… Stereo/mono… ?? AND… I’m sortta thinking that there may have been some Rack mounted mic pre-amps and EQ’s and signal conditioner’s around somewhere… to “Feed” some of the input channels… Maybe??


The terminal strips are all the inputs and outputs, all nicely labeled, really a beautiful design. They gave me the external box they used for a patch bay - a radio shack thing with lots of rca inputs, into which they directly plugged the cart machines, the R2R, turntables, and the like, out of which comes a bundle of wires that each have the little u-shaped connectors to hook up to the strip. The engineer who took care of this stuff was a model of neatness.

Clava, I got the idea of a tape delay for the cart machines from a DJ fried of mine, who used to use them that way. I have the manuals for the units, and the wiring harnesses, so I could give it a go, just haven’t had time. If what you say is true, I’ll be sort of disappointed. Oh, yeah, I guess I won’t be, since there is that big old R2R to play with. :D

BTW, clava, the Optigan has developed Alzheimer’s or something - it starts out fine but the disc tends to turn more slowly after a few minutes of playing, and then goes down down down lower and lower in pitch and then halts. Sort of a cool effect, but I’m just guessing that it isn’t a good sign. What a crazy instrument. Folks who go for these things really are in for lots of maintenance time.

OK, I found the manual, it turns out the unit was mislabeled, it is an 8S150 rev A, manual here, 100 pages pdf:

Looks like a typical broadcast console. 30 to 20K freq response, good noise figures etc… I’d rig that thing up to a patchbay and use it to feed a soundcard or whatever recorder. Save a bunch of cable juggling…


Well, I have 16 ins and 4 outs, and you are correct, D, the specs say it’s pretty darn flat in that range, really looking forward to hooking it up, but I suspect it will not have a particuarly special sound, given that it’s op amps. But who knows? :)

Bill, if you can tell me how the heck to hook up low impedance mics to this, I’d appreciate it. I think I understand the manual, but…I dunno… :)

I figure I’m going to get 16 xlr inputs and 4 out, and put them in a rack box.

Hi TomS:
I got to download that PDF File you posted the link to… When I attempt to open the link I get a Pop-up screen that says I need Adobe Reader v7 to see/read it… Then… I say yes to the screen and My browser just sits there and nothing happens, except that my modem appears to be downloading something… still… nothing… From the photos you posted, it looks like you have 16 inputs that are inputs to each of the eight pre-amp cards… But that looks like 8-mic inputs and 8-line inputs… for the eight cards… From that photo, it also looks like the northern electric set I built back in the '60’s… That being said… the mic input have no Trim/attenuator circuits… The mic gain/inputs will run at “Full-Tilt” … with no control over attenuating the mic inputs… Now… I stand corrected, with saying this till I can see the prints of the pre-amp cards… Maybe, you can post those prints… It will save me from trying to download the PDF Files… including the input transformer prints…

I stand corrected again… This would be a nice place to insert a “Patch Bay”… with 8- mic inputs and 8 line inputs… With a patch bay normalization for each input you now would/will be able to connect (Through Patch Cables) any mic input to any of the 8 channel(s) and any line input to any of the 8 channel(s)… I think??? ??? :O

Again… This could be the place where you provide In/Outs and Outputs/Sends… to go to the likes of an 8 in/out DAW Card… e.g. a “Berry” or a Moto or an RME audio card… OR… this is where you “TIE” your DAW to the SET-UP… Normalized through a Patch Bay…

O.K. that could be “Over-Kill” but the 16 inputs could be in the Control Room or Studio Room so the inputs could be selectd “At Will”…

From what I can see… On the terminal strips there is a (+) and a (-) and an “Earth” for each of the mic-and-line inputs…

Not to get “OverZellous” here… But this is where you install a “Switch” so as to install a “Phase Switch”, for each of the 8 mic in’s… and maybe, for each of the “Line In’s”, as well…

It seems to me that the unit should have a pair of meter amp cards and a pair of “Final” out amp cards… or maybe the meter amps and output cards are on the same cards… I expect there should be some calibrate pots to adjust the meter response as to level output…

My imagination is running away with itself… I think I’ll just contemplate all this the see if you can post some of that pdf file/schematics…

By-the-Way… did you get to power that board up, yet?


The board was in operation when they pulled it. How about that? :)

OK, I got it, + and - and ground for each mic input. No problem. If I have time tomorrow I’m going to hook some stuff up and see what happens. :)

Funny thing is, they had it wired to a breakout box, all unbalanced, including a balance mic - an EV 635 - how could that work?

I dunno how much of this you’ve figured out by playing with it, Tom. What I read means it can’t be configured the way I’d want it. 'Course it ain’t my mixer, so who cares how I’d want it configured…

Basically, to use the preamp cards as mic preamps, you’ll need to make sure the jumpers on each card are in the right configuration. This jumper business isn’t too unusual for this level of gear. If you look at pg. 73 in the manual, you’ll see the component map of the preamp card. This will help you locate the jumpers that you’ll need to check. Page 17 (among others) tells you which jumpers need to be used if you want each card to be a mic in or a line in.

Wox is right with how to land wires on the terminal strips. I’d add that your “+” wire is generally pin 2 on an XLR, the “-” is pin 3, and the ground is pin 1. Try to get one or two mics working with the thing, then you can get crazy with configuration.

Just off the top of my head, you might want mixers 1-4 set up for mic ins and mixers 5-8 set up for line ins. That way you could have mics going to your soundcard and lines coming back from your soundcard and you could use this thing as a summer for your tracks instead of using the sum buss in n-Track. One problem I see is that the preamp cards don’t have direct outputs, so I don’t see an easy way to use more than 4 mics at once into your soundcard. Also I suspect that, given the single stereo rotary fader nature of the thing, when a mixer is set as a mic input, you’ll really only be able to have “1 mic per knob” sort of operation. That suggests using the thing as a buss mixer for drum inputs to get your drums into n_Track as 2 stereo pairs or some such thing. This is all running before walking, but I think you have a powerful device there that can be far more than a rack of 16 mic amps that only has 4 outs.

Go slow and MAKE NOTES on routing of a signal to figure this thing out. “If I put a mic in HERE and route it THERE, then the signal shows up in THIS PLACE” is invaluable stuff to know. It takes time to build your knowledge on routing signal through something like this but you’ll figure it out. My chief engineer and I are still finding out routing options on our MCI, mostly by asking “how do I…” questions, then looking at the block diagram for a channel and patching stuff, one channel at a time. On this kinda gear, once you know how one channel works, you know them all.

Good luck and have fun! That thing has +28V rails on the input amps. Bet it has tons of headroom…