Moog VCO which modern equivalent?

van · Post by **van** » Sat Feb 28, 2009 11:11 am

and to continue...the 921A can drive 3... 921Bs if I'm not mistaken correct me if I'm wrong so its a matter of real estate. The 921B frequency range is 1 to 40,000 hz. The 921 has a frequency range from .01 to 40,000 hz really a super LFO that also does the audio range. A unique feature of the 921 is waveform clamping at any point in the cycle...by S and V trigger signals.

EricK · Post by **EricK** » Sat Feb 28, 2009 11:52 am

THats very right. I might add that any real fully blown oscillator is also a LFO.

Thats according to synthesizers.com when asked why they didn't have a dedicated LFO module.

Kevin Lightner · Post by **Kevin Lightner** » Sat Feb 28, 2009 12:59 pm

I'm not sure if these are Synth.com specs or Moog, but if Moog, they're not absolute gospel.

For example, a 921B can go as slow as a 921.
Just give it some negative voltage.

I've measured their top frequency and 50-55Khz is common.
I'm pretty sure a 921B can go slower than 1hz when set to LO too.
A 921 is a much better LFO than a 921B though simply because it's not paired with additional VCOs, it has inversion and there's an output volume control.

I've also had a 921A drive six 921B's before, fwiw.

Voltor07 · Post by **Voltor07** » Sat Feb 28, 2009 2:20 pm

Great info, as always Kevin! This discussion is most helpful to someone who would like to enter the world of modular synthesis, but who has no real understanding of it. Thanks everyone!

EricK · Post by **EricK** » Sat Feb 28, 2009 2:47 pm

According to the Moog System 15 sales literature:

the 921B has a frequency range from 1-40,000hz
the 921 has a frequency range of .01 to 40,000hz

921b
AC and DC coupled frequency control imput jacks-linear responce

921
3 frequency control input jacks-exponential responce

Kevin,
Im not contesting you, im just quoting what the literature says.

If you want to think about it, generally, I was told by Mike Bucki who built my Modusonics 921a that it will drive 3 921b's. Now Im sure with a harness it will probably drive more like Kevin said. But generally you see a 921a driving 2 921b's(system 15/35) or 3 921b's (55).

So a system 55 will have generally 2 921a's and 6 921B's taking up a total of 8 spaces in a cabinet. In a portable cabinet thats an entire row.......very space consuming to have the extra voices.

6 921 modules will take up 12 spaces. (2 space width each) So from the side of my mouth I will say that a bank of 921A/B combo provided more voices per space than a pure, fully loaded 921 module in a complete synthesizer setup and thus was the reason for the option.

From Modusonics from april 07 prices, a 921a was 425 dollars, 15 shipping. THe 921B is 685 dollars with 15 shipping. (of orded on an individual basis. A desktop power supply would be 100 bucks.

THe 921 module costs 1285 dollars plus 15 shipping and 100 for a power supply if you don't have one already.

So It is a little cheaper to go the 921AB route as it probably was in the 70's.

Kevin, do you think this is accurate?

Eric

Kevin Lightner · Post by **Kevin Lightner** » Sat Feb 28, 2009 2:59 pm

I've no problem with those specs.
They're probably guaranteed figures (derated) and 40Khz is nothing to sneeze at anyways.

My comments basically address that the two versions of 921s use the same boards and have the same tonality.
They're implemented slightly differently when it comes to linear CV and sync abilities.
Overall I think they were good choices / compromises.
Remember, a 921 is twice as wide as a 921 A or B.
A Moog 15 would have been half filled with oscillators if it was all 921s.
You'd run out of mults quickly too.

Voltor07 · Post by **Voltor07** » Sat Feb 28, 2009 3:03 pm

EricK wrote:
921b
AC and DC coupled frequency control imput jacks-linear responce

921
3 frequency control input jacks-exponential responce

Kevin,
Im not contesting you, im just quiting what the literature says.

That confirms what Kevin said. And after 20000Hz, who cares? Unless you're making music for your dog. Some hi-fi horn piezo tweeters are rated up to 20kHz, but I've measured frequencies from them up to 50kHz.

Trigger · Post by **Trigger** » Sat Feb 28, 2009 3:11 pm

OK, here's a question:
Why are all Moog modules a 900 series? Were there series 100-800 that didn't make the grade? Or did Bob just decide "921", "911", etc., just sounded cool?
Any one know or care to weigh in on this one?
Mr. Bucki?
Mr. Luther?
Mr. Lightner?

Kevin Lightner · Post by **Kevin Lightner** » Sat Feb 28, 2009 3:21 pm

I've no clue, however the Bode frequency shifter was number 1630.

JohnLRice · Post by **JohnLRice** » Sat Feb 28, 2009 3:41 pm

Kevin Lightner wrote:John,

A 921 basically IS a 921A with a 921B together.
The boards to both the A & B modules are contained in the 921.
There's no difference in the sound between the two configurations.
The larger 921 has a mixed bi-polar output that's a bit hotter than a 921B delivers and the sync has some minor changes between the two, but otherwise they're pretty much the same.

Awesome, Kevin! Thanks a bunch!

Trigger · Post by **Trigger** » Sat Feb 28, 2009 4:49 pm

Kevin Lightner wrote:I've no clue, however the Bode frequency shifter was number 1630.

Right, wasn't that because it was Harold Bode's design, not Bob Moog's?
Also, there are the Control Panel (CP) series modules as well as the 900 series.

Maybe some detective work is in order...

JohnLRice · Post by **JohnLRice** » Sat Feb 28, 2009 5:20 pm

This wiki page has a pretty good list of module numbers (hopefully it's correct!

):
http://en.wikipedia.org/wiki/Moog_modular_synthesizer

And just FYI for people really into the gutz of Moog instruments but haven't seen Donald Tillman's excellent site check out:
http://www.till.com/articles/moog/patents.html

EricK · Post by **EricK** » Sat Feb 28, 2009 5:26 pm

There were also other modules of designated numbers for the Moog Drum Machine for Eric SIday.

Im guessing these were fast envelope oscillators of various frequencies and timbers.

Voltor07 · Post by **Voltor07** » Sat Feb 28, 2009 7:49 pm

EricK, I remember seeing pictures of this drum unit/thing on several diferent websites. I have never seen action shots of it in use, however. How was it played? Drum controllers, similar to the 1130?

Trigger · Post by **Trigger** » Sat Feb 28, 2009 8:11 pm

EricK:

Good catch on the drum module...