Moog Music Forum

Great pics, info and DIYing, CZ!

Quick update to the photos I posted of the blank modules.
Now that I have all the hardware sorted out, I began wiring up the 982 two channel mixer.
Those Vector Plugbords use .062 pins, type T-28. There is a special insertion tool to help push them in without bending them up. So first I needed to insert about 130 or so pins in the pattern I had drawn out on paper.


Once the pins are in place, the parts can be soldered in. Those pins have a "V" where the component leads go, and have serrated edges to hold the part in. There is also a through hole on the side for wires. Can see why Bob Moog refered to these as "Hot Rod" boards as making changes or rewiring is very easy to do.
First few components. Resistor with leads before soldering in.


Since this was a clone, I used the exact layout of the bigger 984 mixer with the same parts. All 1/2 watt carbon resistors, Mullard "Tropical Fish" caps and the 2N2926 transistors.
All the components for one mixer strip. The 984 had four of these, my 982 will have two.


After the components are all soldered in, the back of the board needs to be wired up. This would be the equivalent of wiring the copper traces on a standard PC board. The bottom of the Vector pins have a large through hole for making the connections between the various components.
Here is the start of the wiring. The component layout is set up to minimize flying wires and mostly use buss wire.


During construction I print out a flipped image of my drawing, so the back side connections appear as I would wire them.
Finished wiring with a minimal ammount of flying jumpers. (green=ground,red=positive supply voltage,blue= negative supply voltage)


Due to panel space I used a smaller type pot used in ARP 2500's. Went with small 1/8" shaft Clarostat pots. High quality units with stainless steel shafts. Just did not have room for the R.A.Moog typical AB type J pots. Had to fit 10 pots on a single 1U panel with four 1/4" jacks/sockets. Each strip has four 25K linear pots and one 5K linear.
Fitting in the first strip in the frame for testing. Can see those smaller pots.


Time to test this out. Just used jumpers to the pots. Want to make sure the pots were wired in the right order. The volume pots are easy but those tone controls could go either way, and sure enough my first guess was backward. Just flipped the connections and made note on a diagram for wiring to pots.
Ready to test!


So...what does it sound like?
One word, WOW! This mixer is awesome. Very responsive tone controls. Mixes great and can get that soft to hard clipping/overdrive. Feeding back into itself I was able to come up with some interesting tones. Although this is not voltage controlled, a 902 VCA and 911 EG in the feedback path yielded some great contoured filtered tones. Almost like the Minimoog feedback patch, but with tone boost/cut controls to shape the overdrive. With two channels, many patch configurations are possible. From just a final stereo output mixer, to a mono mixer with a send/return. Or a feedback overdrive/distortion with asymmetrical clipping.

Really like these original Bob Moog designs and circuits. Many of the earlier systems had these various final output mixers. Perhaps thought as needed as these were AC coupled mixers and would block out any damaging DC from going to the recording unit and monitors. Bob even made a 981 four channel, single output mixer. (no tone controls.) Noticed one of these on the early Carlos system from the SOB days. A few other 981's on the Max Brand system. Still have not seen a close up of the original 982 mixer, but guessing there was only four pots per strip and used a single panpot to mix between the two inputs.

Have to get busy and finish the other strip, now I know it all works and sounds awesome!

Love the idea to use jumper clips to test things out before soldering...

Stephen




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Great job! Can we expect a "CZ Synths" or "Rider Modular" company in the near future?

JohnLRice wrote:Can we expect a "CZ Synths" or "Rider Modular" company in the near future?

I'm sure that is how many started out. Finding those parts used in the old Moog is quite fun and there are great deals out there, you just have to find them. For instance, they still make those Vector T-28 pins today. They are a bit different with ROHS and are phosphor-bronze. The price for anything Vector is expensive, about $11 for 100 pins and around $70 for a thousand. In my search at a radio ham fest/flea market, I found a box of what looked like junk with 1100 of those pins scattered about inside. Paid $5 for the lot. One of my best scores at those. Another E-bayer had a 1000 pin bag and the insertion tool for around $14. Just have to know what and where to look. But is is getting more and more difficult to find those exact parts, even though there are many out there. So it is limiting to a small scale personal production.

If I was going to make any kind of Moog modules for sale, I would try to do it all on SMT boards with discrete components. Just recently saw the same idea with the Moog filter set in Eurorack. It is really do-able with some minor substitution of parts. But all of those early Bob Moog designs are made with discrete parts. That mixer I just did could have been done on SMT with different low noise transistors. The only difference is I would not try to change the modules to work with modern voltages. +12/-6 rails, S-triggers, and those low level signals that sometimes need to be amplified. And no IC's of any kind. All part of the way those work and interact with each other. Would be really cool to see a minature set of 900 series R.A.Moog modules in a small Euro format. I'm really surprised no one has done it yet. Could be a small market for those if done right.

Seems like every clone out there changes resistors to handle today's typical gates and voltage signals. Some of the Moog modules amplify by a factor of 2, like the 902 VCA and each input on the CP type mixers. All that clipping and distortions from the small offsets and amplifing and inverting those asymmetrical signals is part of the sound and function. Not going to work the same if the signals are already too hot. Too many engenieers that know better try to "fix" these. I would leave the design alone, it is perfect for what it is. Just make them smaller.


EDIT:
Almost done the 982 Two channel mixer.

Was able to finish that 982 mixer. Wiring the front panel was time consuming. Perhaps more due to the restricted space in my condensed panel choice. But it is now all together and works beyond what I expected. Very nice addition to an old Moog.
Here it is all wired up showing the component side.

And a view of the back wiring.

Clone matches original layout and parts very closely.

The 982 in it's new home.

This is a really handy module. Perhaps I will get a proper etched front panel in the future. Wanted to make sure I was happy with the layout first using the smaller knobs.

Next module will be a discrete component ring modulator with dual reversable attenuators. Not much to it, standard Moog reverse attenuator circuit. And a CP-3 type mixer/amplifier with extra inputs, after the ring modulator to bring up the ring output to match the level of the 901's. The mixer will be basically a CP-3 without any attenuators, 4 input with +/- output where each input amplifies by a factor of 2. A small switch for input 1 and 2 will bring in the ring mod or just standard inputs to the mixer. Making it multi-functional.
Ring mod frame with the mounted transformers. Was tricky to get those to fit in the bottom.

And the front panel. Attenuators on top, and ring mod/mixer inputs (4) and +/- outputs.

I'll post some pics when I finish construction.

Most impressive, CZ!