904C Filter Coupler

System 55 • System 35 • Model 15
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Rarecomponentadsr
Posts: 71
Joined: Mon Aug 24, 2015 5:08 pm

904C Filter Coupler

Post by Rarecomponentadsr » Mon Oct 19, 2015 9:42 am

I posted a similar message a while ago but after completing my 904C clone I'm wanting to determine if its working correctly . It seems a strange module ...sometimes working sometimes not... in either bands.
That is it all depends on where the dials are set and what control voltage is in play. A lot of the time I hear nothing then after adjusting a dial at random audio comes thru. But I believe this is normal ?

My 904a/b are both fully working and are set at the advised settings in conjunction with the 904C

It's strange that there is absolutely nothing on you tube or anywhere that demonstrates the 904C working.

EMwhite
Posts: 1651
Joined: Sun Jun 21, 2009 12:22 pm
Location: Middlesex

Re: 904C Filter Coupler

Post by EMwhite » Mon Oct 19, 2015 3:32 pm

Yes, it's strange, but this is coming from a MOS_LAB owner.

When I first got mine, I thought I would plug it up and play with it in the normal manner (figure it out as I went along).

Shortly realized I didn't know what I was doing, was out of my element, and felt like a novice once again (no or low output) ! so I consulted the manual (the original Moog doc) and what I was doing incorrectly was not having the cutoff and freq range switches on the 'a' and 'b' modules in the proper location.

The right way to use it is to set these and forget these though once you get the hang of it, you can do otherwise; then make all 1/4" connections through the couplers and only mess with those knobs. This is not to say that you cannot or should not mess with resonance or plug additional env gens into the CV inputs on the 904a, for instance, but if you change the freq cutoff pot, you are robbing the 904c from it's job which is to control band width and position.

If you go back to using the other filters on their own, obviously the 904c switch ought to be set to OFF.

Here is a link to a Muffwiggler topic which has the link to the Moog doc posted: https://www.muffwiggler.com/forum/viewt ... highlight=

Hope this helps.
'76 Minimoog, Taurus 3, Oberheim FVS + Son of 2-voice; Sequential ProOne; Juno 106; Moog Model 15; Kurzweil 250; Hammond M3; and a handful of Fender Basses Flickr!

Rarecomponentadsr
Posts: 71
Joined: Mon Aug 24, 2015 5:08 pm

Re: 904C Filter Coupler

Post by Rarecomponentadsr » Tue Oct 20, 2015 6:42 am

Thanks for posting this info, it's the best yet to be found anywhere concerning the 904C which I think is one of the most enigmatic modules. Or at least coupled with the 904a/b. The samples are very useful.

So I think from what I read, my clone is probably working fine ....it's just learning how to use it ..certainly some of the foibles are def akin to my experience with it. I think it is quite an important addition to the filters overall compliment ...but again I would love to see the 904C working......anyone with a fully functioning 904C volunteering to post a video ?

EMwhite
Posts: 1651
Joined: Sun Jun 21, 2009 12:22 pm
Location: Middlesex

Re: 904C Filter Coupler

Post by EMwhite » Tue Oct 20, 2015 9:56 am

I'll post something on YouTube if you want but it won't be high quality (I only have an iPhone so while you'll be able to hear the differences, it won't be HiFi so to speak) and WILL be the MOS-LAB derivative. I have an actual Moog 904a but not a b,c. I do have the full set in MOS-LAB.

Let me know if you are interested and I'll pull something together across the next few days.
'76 Minimoog, Taurus 3, Oberheim FVS + Son of 2-voice; Sequential ProOne; Juno 106; Moog Model 15; Kurzweil 250; Hammond M3; and a handful of Fender Basses Flickr!

Rarecomponentadsr
Posts: 71
Joined: Mon Aug 24, 2015 5:08 pm

Re: 904C Filter Coupler

Post by Rarecomponentadsr » Tue Oct 20, 2015 12:34 pm

Totally !

But please don't feed the coupler with sequencer output! ! I would love to hear a simple waveform (s) put thru the 904C with appropriate dial twizzles just to hear (and see) what's coming out...and perhaps with CV input to ththe controllers ?
Don't worry about the quality ...so far it will be the best video of a 904C in action on the web in the whole world !

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