Moog 984 4 Channel Mixer

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dingebre
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Post by dingebre » Fri Jul 04, 2014 2:34 pm

Stereotactixxx wrote:Thanks for the extensive reply David.
The more I think about it, the harder it is to resist.
If Paul produces a small run of this, I'm getting one.
You're welcome. If you have the space, I think you'll really like it.

David
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dingebre
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Re: 984 matrix mixer

Post by dingebre » Fri Jul 04, 2014 2:35 pm

davebr wrote:I did my own 2 channel final output mixer and feed it with the split from a fixed filter bank. While restoring the Moog, I will say I was quite impressed with the 984 and thought the tone controls actually added a lot. If I wasn't out of space I would probably redo my system and incorporate one. It is a nice design and a very nice redesign.

Dave
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Thanks Dave.
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Stereotactixxx
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Post by Stereotactixxx » Fri Jul 04, 2014 2:52 pm

dingebre wrote:If you have the space, I think you'll really like it.
I already had plans to build another cabinet this summer, so space won't be an issue. Now, lets just hope more people build themselves another cabinet so that Paul's small run of these modules will happen.

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Post by NYMo » Sat Jul 05, 2014 7:40 pm

Boosting the output of the fixed filter is a big one for me..even full boost from a Q125 still doesn't bring the level up enough for me ( just worked out I could use the Q118 for that .. :doh: ) but I've got 5 spaces left..so I could be up for one of these.
I'm presuming the stereo outputs are wired hard left/ right..but I'm not sure what the purpose is, as opposed to the individual outputs, other than save using two cables instead of one.
Someone care to enlighten me ?

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Post by seb17320 » Mon Jul 07, 2014 3:25 am

:mrgreen:
New Mos-lab project clone for this summer :
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Post by ZYKLIFF » Fri Jul 11, 2014 5:57 pm

That looks wondrous, Paul.
krisp14u wrote:Thanks to David for the PCB I am now the very happy owner of a Moog 984 matrix mixer :bacon:

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I have been talking with David about the possibility of making a small run of mixers the same as the one I have built with a panel from Ben

Its maybe not for the space conscious 5U user but well worth the space if you have it

I’m loving the way the EQ and the whole thing colours the sound

I need 5 builds to make it worth it and the price would be around 270-290 GBP + shipping

this is not something I will be stocking but more a one off build for anyone who would like one but doesn't have the skills

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Post by dingebre » Tue Jul 15, 2014 1:06 am

NYMo wrote:Boosting the output of the fixed filter is a big one for me..even full boost from a Q125 still doesn't bring the level up enough for me ( just worked out I could use the Q118 for that .. :doh: ) but I've got 5 spaces left..so I could be up for one of these.
I'm presuming the stereo outputs are wired hard left/ right..but I'm not sure what the purpose is, as opposed to the individual outputs, other than save using two cables instead of one.
Someone care to enlighten me ?

Cheers
When I did the panel, I had the space and decided to add a stereo jack between the individual channels. No real advantage or disadvantage other than I can plug a set of headphones into the output if I want to quietly tweak some knobs... :)

The overall gain is not that high, about 1.25. The CP3 has a higher gain and can easily fit in a single wide panel if you need some extra gain. That said, you can tweak the feedback resistor in the final transistor output stage and up the overall gain.

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Post by krisp14u » Mon Aug 04, 2014 6:04 am

So if anyone wants in on this send me an email with your details by Friday
Price is going to be at the upper end
£290 GBP unless a lot more people come in
Cheers :guinness:

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Post by CZ Rider » Mon Aug 04, 2014 2:51 pm

This is a really nice final output mixer. Gets that controllable asymmetrical distortion that can be fine tuned with the bass and treble cut/boost. Can do the Minimoog feedback loop with more control using the tone adjustments.
I did not have much room so I built the 982 two channel version. Using small 1/8" shaft pots like the ARP 2500 used and smaller knobs, I was able to squeeze it in a 1U Moog panel. I figured a two cahnnel version could still be configured many different ways, from a final stereo out, to a mono with send/return, to a distortion unit. And most important it had that tone I was missing from my unit. Cranking up the bass with a bit of asymmetrical distortion gets a very familiar Moog quality. Very nice tone shaping mixer.

Thanks to Dave Brown's photos, I was able to match the original layout for my 982 clone. The 984 had two of the same boards, so I only needed the one. I built this into a R.A.Moog style frame using the same Vectorbord that Bob Moog used on the original modules.
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Here it is all wired up showing the component side.
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And a view of the back wiring.
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Clone matches original layout and parts very closely.
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The 982 in it's new home.
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Since I added this to my system, it is a must have module. And configurable many different ways.

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Post by goom » Mon Aug 04, 2014 5:44 pm

Wow CZ, that is SLICK! Nice job! I'd love to build one for myself like that...

How different is the 984's sound compared to the CP3's sound?

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Post by CZ Rider » Mon Aug 04, 2014 6:48 pm

goom wrote: How different is the 984's sound compared to the CP3's sound?
Very, very different. The tone shaping is really the key soundwise. While the CP-3 is more of a utility mixer, being a DC mixer with +/- outputs. The only tone shaping on the CP-3 is with either the click filter (A fixed low pass) or by overdriving a mixture a bit to change the tone. (To overdrive the CP-3 with 901 level sources it needs all four inputs, or a feedback loop, or sometimes cascaded to another CP-3.) While on the 982/4 those tone controls really push the overdrive in a different way. Easy to see the effect monitoring a saw wave with a scope. Overdrive like the CP-3 can be asymmetrical where only the bottom of the wave is distorted. But with added bass and treble boost/cut that distortion can be shaped a bit more. The 25K linear pots I used have the zero setting at almost the 1 O'clock position and not straight up. Might be why the Moog 984 dial is calibrated 0-10.
Bob Moog also made a 981 final output mixer. That one had 4 inputs and no tone controls or master volume. There was one on the Carlos system from SOB days and Max Brand had two of them in his system. I guess these were thought of a nessessary to block out unwanted DC from monitors and recorders.
The 1U 981 final output mixer.
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I do not have a clear photo of the original 3U wide 982, but it looks like Bob designed it with a pan pot between inputs 1 and 2, so it would have two less knobs than the clone I made.
It sounds really good though. I was surprised just how nice this mixer with tone controls worked. Has that odd asymmetrical distortion where too much and it's a square wave, but just the right ammount and it clips the bottom of the waveform. Add in the tone controls and it's quite a vintage Moog sounding mixer.

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Post by NYMo » Mon Aug 04, 2014 7:55 pm

When I did the panel, I had the space and decided to add a stereo jack between the individual channels. No real advantage or disadvantage other than I can plug a set of headphones into the output if I want to quietly tweak some knobs... smile
Thanks Dingbre..headphones..I didnt think of that.
( i was more thinking stereo fx output)
Is there enough gain for headphones in the output ?

cheers
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Post by revmutt » Mon Aug 04, 2014 8:44 pm

A couple of quick questions that I may have missed in the thread.
1. What is the panel size difference?
-I have a blank panel where the mixer should be in my Moog

2. what kind of power connector does it use?
-Since I am running a system that is all Moog except for the Dot Com sequencer I could theoretically do either one.

Thanks,
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Post by goom » Mon Aug 04, 2014 9:38 pm

CZ Rider wrote:
goom wrote: How different is the 984's sound compared to the CP3's sound?
Very, very different. The tone shaping is really the key soundwise. (edited)
Thanks for the info, CZ. I hope to build one at some point.

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Post by krisp14u » Tue Aug 05, 2014 6:01 am

revmutt wrote:1. What is the panel size difference?
-I have a blank panel where the mixer should be in my Moog
the one I'm building is 5MU
revmutt wrote: 2. what kind of power connector does it use?
it will have Dot Com power on the finished units if we get that far
Cheers :guinness:

Paul
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Post by BKehew » Sun Aug 10, 2014 7:12 pm

Indeed the 984-series modules really are exceptional EQ additions. Once you play with it, you'll rarely want to be without. It's THAT cool. I do think a single channel version (not like the 981, sans EQ) with EQ and one input would be amazing. It's not the mixing, as such, that I like... it's that EQ. Although having stereo/quad output options are nice, this form of mixer is not really ideal for anything but static work, which is ok sometimes...

Glad people are working on these designs... very cool!

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Post by krisp14u » Fri Sep 05, 2014 4:22 am

Thanks to all for helping me do this limited run

hope to get them in systems by Xmass
Cheers :guinness:

Paul
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Post by Dave Peck » Fri Sep 05, 2014 6:49 pm

BKehew wrote:Indeed the 984-series modules really are exceptional EQ additions. Once you play with it, you'll rarely want to be without. It's THAT cool. I do think a single channel version (not like the 981, sans EQ) with EQ and one input would be amazing. It's not the mixing, as such, that I like... it's that EQ. Although having stereo/quad output options are nice, this form of mixer is not really ideal for anything but static work, which is ok sometimes...

Glad people are working on these designs... very cool!
If it's the tone controls rather than the summing circuit that accounts for the great tone, how about a single-space 5U module that includes just two separate channels of these tone controls? You could use them separately for unrelated duties within a patch, send their outputs to two channels of whatever mixer you already had, etc. You could also make the output jack of the first channel a switching jack, so it sums the two signals after their tone controls and routes both to the OUT2 jack, and you interrupt this and use them independently by inserting a patch cord into the OUT1 jack. Viola:

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Post by CZ Rider » Fri Sep 05, 2014 8:02 pm

The input and output attenuators are also a big part of shaping the sound. The master attenuator is like a final volume for your instrument, but that channel input attenuator can be used like a drive ammount, and controls how much signal goes into the tone controls. With the combination of those two attenuators one can dial in either a distorted/driven tone at the same volume as a cleaner tone. So a cleaner mix of 2 on the input and 8 on the master could be the same volume output as the input mix of 8 with the master at 2, giving a more distorted/driven tone. (Just an estimate.) Lots of tonal variation especially with the bass and treble controls to further shape the sound. I would say the bare minimal controls for a single channel version would be 4 regular size knobs with two 1/4" jacks/sockets. So the input(drive), bass, treble and master output, with a single 1/4" input and output.
The smaller knobs I used really do not impede the useability of the two channel version. It's not really a performance type module, but I am always using it to set the final volume. And it all fits in 1U of space.

Actual 1U two channel version with lettering photoshoped in.
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Looks and works great sitting on the far right middle row. I seem to use it all the time and wonder how I managed without it. 1U with four knobs would work just as well as a single channel unit. Did not have the 6U of space for the full version, but still wanted that tone control and final volume I was missing.
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Post by Dave Peck » Fri Sep 05, 2014 10:35 pm

Heck yeah. That looks like a really well thought out feature set. If anyone is thinking of making some kind of 1space version and releasing it as a product for sale, that one looks like a good one.

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Post by ualslosar » Fri Sep 05, 2014 10:42 pm

Hi,
This snip is from the Moog spec for the 984.

- Isn't the arrow pointed the wrong way for this patch ? (You can use an output as an input ?)

- If this patch were reversed, would you get the same result, please ?

Image

Thank you
Larry

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Post by CZ Rider » Sat Sep 06, 2014 12:55 am

I noticed that in the manual too. Makes it difficult to understand as the arrows are the wrong direction. Four inputs on the left bottom 1 thru 4 and the four outputs on the right bottom A thru D. It works where output A is being fed into the echo unit and returned on input 2.
The matrix would be easier to understand it the outputs were lined up vertical at the right side of the module.
So the patch makes sense with the synth signal at 5 on the bottom horizontal "D" strip. While the top "A" strip has the synth signal at 5 with the "A" output master at 5 sent to the echo. Returns on input 2 set at 5 on the "D" strip, mixing the straight signal and echo each at 5 with final "D" master at 5. Final mix out from the "D" output.
Would not work if the arrows in the drawing were correct and the echo input was the mixer input. (I tried it just to be sure, you never know?)
My smaller 2 channel works the same way. Can be patched like that example as a mono effects send, or a stereo final output, or two independent mixers, even a feedback loop with tone control. Quite versatile, but there are only two inputs. The four channel version not only adds two extra channels but all the attenuators for four inputs on four strips. So 16 input attenuators where I have only 4.

Edited: Wrote vertical, changed to horizontal strip.
Last edited by CZ Rider on Sat Sep 06, 2014 10:41 am, edited 1 time in total.

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Post by ualslosar » Sat Sep 06, 2014 1:34 am

I can't believe it's a glitch in the Moog docs after all these years, but it looks like you proved it.

So the arrow is in the wrong direction.

Thanks for checking it out, CZ Rider.

Regards

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Post by CZ Rider » Sat Sep 06, 2014 2:22 am

Needs to be fixed.
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Quite a few mistakes in those Norlin era documents and schematics. Most were simple copy mistakes from the original docs. But at least they published the docs and schematics.

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Post by NYMo » Sat Sep 06, 2014 3:18 am

That looks better..I was wondering about that too !
Thanks CZ Rider !

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