Custom Emerson 901's...

System 55 • System 35 • Model 15
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analogmonster
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Re: Custom Emerson 901's...

Post by analogmonster » Sat Jul 24, 2021 5:04 am

How is the temperature stabilization done? Not with the diode arrays, I assume. And is the dual pot solution of the frequency vernier changed also?

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noddyspuncture
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Re: Custom Emerson 901's...

Post by noddyspuncture » Sat Jul 24, 2021 6:24 am

analogmonster wrote: Sat Jul 24, 2021 5:04 am How is the temperature stabilization done? Not with the diode arrays, I assume. And is the dual pot solution of the frequency vernier changed also?
Yes, the complete oscillator section of the 901B is discarded so the dual pot is also gone. The new oscillator is on the piggyback daughter board. The stabilisation is done with a tempco resistor and the whole expo convertor is redesigned and now lives in the oscillator... it's all rather like the 921's ended up being - only without any IC's.... :)

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analogmonster
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Re: Custom Emerson 901's...

Post by analogmonster » Sat Jul 24, 2021 6:42 am

Ah, that's good :) Is the wave shaper also redesigned? That would be a pity, as the old circuit added such a nice and smooth buzz to the waves I like very much.

Rarecomponentadsr
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Re: Custom Emerson 901's...

Post by Rarecomponentadsr » Sat Jul 24, 2021 7:43 am

This is good . Are you planning to make the information available ?
ie circuit schematics etc ? I guess you put a lot of time and effort into this Can you tell us where the original information was located ? I can only think you had access to Keith’s stuff…choose what, great effort.

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noddyspuncture
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Re: Custom Emerson 901's...

Post by noddyspuncture » Sat Jul 24, 2021 9:24 am

analogmonster wrote: Sat Jul 24, 2021 6:42 am Ah, that's good :) Is the wave shaper also redesigned? That would be a pity, as the old circuit added such a nice and smooth buzz to the waves I like very much.
Yes the wave shaper section is indeed retained - obviously Bob had the same opinion as both you and I... :D

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noddyspuncture
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Re: Custom Emerson 901's...

Post by noddyspuncture » Sat Jul 24, 2021 9:30 am

Rarecomponentadsr wrote: Sat Jul 24, 2021 7:43 am This is good . Are you planning to make the information available ?
ie circuit schematics etc ? I guess you put a lot of time and effort into this Can you tell us where the original information was located ? I can only think you had access to Keith’s stuff…choose what, great effort.
No I'm keeping it safe, as I promised my source.

I'm also building a full 'preset box' system based on Emo's original one to interface with my Model 15. And again, I'll keep that info safe too. In fact, there was a lot of it missing and I had to experiment with it and work it out myself over the years..!

Rarecomponentadsr
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Re: Custom Emerson 901's...

Post by Rarecomponentadsr » Sat Jul 24, 2021 6:17 pm

Okay..keep safe !

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ummagumma
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Re: Custom Emerson 901's...

Post by ummagumma » Sun Jul 25, 2021 10:13 pm

That is an awesome project!!

Congratulations on getting it figured out & working

It's also a great tribute to both Keith and Bob

RIP

EricK
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Re: Custom Emerson 901's...

Post by EricK » Fri Jul 30, 2021 8:00 am

noddyspuncture wrote: Sat Jul 24, 2021 9:30 am
No I'm keeping it safe, as I promised my source.
It sounds like an interesting historical document, why must it be shrouded in secrecy?
Support the Bob Moog Foundation:
https://moogfoundation.org/do-something-2/donate/

I think I hear the mothership coming.

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noddyspuncture
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Re: Custom Emerson 901's...

Post by noddyspuncture » Wed Aug 04, 2021 7:03 pm

Today I finished the preset box button selector unit.... and it's working nicely..! :D

https://www.youtube.com/watch?v=jRqs00c9PKg

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ummagumma
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Re: Custom Emerson 901's...

Post by ummagumma » Fri Aug 06, 2021 7:52 pm

Looks slick!

That is a crapload of wiring...

Did Keith's have 10 presets? I thought he only had 4-6?

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noddyspuncture
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Re: Custom Emerson 901's...

Post by noddyspuncture » Sat Aug 07, 2021 4:24 am

He had at least 14 or more at one point. He has two preset boxes in some photos around 1972/3. Maybe he used the Moog a lot more around then, he did make lots and lots of different sound effects in the middle of Tarkus and Pictures around that time as can be heard on the boot-legs.

His original box had 7 or 8 loaded - you can clearly see not all slots are filled in photos. In '77 he had the new revised 'module' type preset enclosures, although there will have been a master module which they all connected to somewhere.

They had two presets each and there were six of those 'modules' in some photos, making 12 presets. In later years and up to today with the restored system at the museum there are just 5 of those 'modules' making 10 presets. I decided to go for 10 as the steel box I had and the size of 'cards' it could take dictated it. :D

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noddyspuncture
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Re: Custom Emerson 901's...

Post by noddyspuncture » Sat Aug 07, 2021 8:54 am

So, basically having now built and interfaced everything with regards to the Moog Modular preset box - (except the preset cards and also the 901's, I'm still waiting on the FET from the USA for those...) - it occurred to me that I should maybe test out a few of the features. I could do that by replicating what a card would do... basically connecting points to ground and applying some voltages here and there so I picked the lines into the 921B oscillators which control the footages. I also picked one of the lines into the 921A controller for fine tune and then I found the two lines which control the mixer inputs I'm using. I fed a sawtooth from the first 921B osc and a triangle from the second into the mixer, The control here is just on & off... or 'sounding' and 'muted'. The card will allow for in between, so voltage controlled 'mixing' will be possible. I used my little breadboard and pins to change the settings. The functions I'm not changing here are the filter cut-off, the resonance level and also none of the EG parameters. Adding those to this demo would have been too big a job and as I've already had problems with those bundles of wires shorting, it wasn't worth the risk..! And also as those are a massive part of the 'perceived effects' on a patch change this demo is quite a simple and basic one - just to confirm my wiring is "something like" and also to give you an idea of what this thing will be doing.

https://www.youtube.com/watch?v=rPg9eEdCu7g

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noddyspuncture
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Re: Custom Emerson 901's...

Post by noddyspuncture » Mon Aug 09, 2021 7:12 am

Thought I'd try a rough layout of the bits which will populate a preset card.

Ooooh... it's looking a bit cramped on there, even more so when you consider that I also have to fit a small (6 resistor and 4 transistor) circuit into that small free space bottom left.

So I had to do a quick redesign of that circuit's layout and it looks like I'll be able to do it. I mistakenly labelled the drawing '5 ROW' - when it it's actually '5 COLUMN'.

IMG_9142.JPG

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