My 'preset box' project for my 'System 15'...

[noddyspuncture]

Hi folks,

My System 15 reissue is expanding..! This is how it looks now. I've had to have another cabinet made for some extra custom modules and some overflow modules from the '15' cabinet..! I put the filters & noise, the fixed filter bank and the attenuators up there along with an original R.A.Moog envelope follower and also a high pass filter and filter coupler which I had also built myself some time ago. I also wanted to add another 921A controller and an envelope generator along with another 4 channels of mixer. The panels for those recently arrived so I got to work. I'd already built the circuit boards and they were just waiting for the cases. And I managed to source an actual NOS Moog cct board for the 911 EG.

So the System 15 case now also includes the extra 921A, the 911 EG and my custom mixer (that I've called a CP3B). These are all modified and ready to interface with the 'preset box' I have built based on Keith Emerson's original unit which came with his system and was used at the 'Jazz In The Garden' event in 1969.

There are also a 901a & 901b which at the moment are just empty cases - I fitted them just to see what it will all look like. Those will be clones of Emerson's heavily modified units which I am building from Bob's notes and drawings in Emo's Modular service manual.

In addition to all of this I've also fitted a reverb tank just above the power supplies and built a 905 reverb circuit which lives next to the CP3 mixer behind the bottom panel. The trunk line sockets are now the reverb input and output sockets - and I'll get a plate made for that to go over the trunk line legends.

I still need to interface the preset box with all this so there's loads of wiring still to be done around the back for that... but I'm getting there, albeit slowly...

[noddyspuncture]

Could only upload three images so here's some more of the modules I mentioned which I just built...

[noddyspuncture]

So that's 2+1/2 cards populated... well, the 2 are not fully because there's still the switching cct to add in the space bottom left - and then there's loads and loads and loads of wiring to do. It's taken me the best part of two full days to get this far, what a job - Jeeez!

Anyway, I'm making three of them initially so I can have two to switch presets between and a third as the one which I examine to remind myself of all the little workarounds I made after the first one I did. It's definitely a "learning curve". I could also install the third into the preset box and switch between three when I demo it.

The other seven that need doing I can do slowly over time and add them as and when but for now I'm seeing a light at the end of a very long tunnel.

[noddyspuncture]

Test fit into the preset box of the three cards I have assembled. Just to check that my measurements were good and the cards don't foul each other. Also to get an idea of how easy it will be to 'programme' them in the 'slid-out' position. Not looking too bad overall...

[analogmonster]

Seems that you got rid of the edge connectors and replaced them by D-SUBs - or are they just not visible on the pics?

[noddyspuncture]

Seems that you got rid of the edge connectors and replaced them by D-SUBs - or are they just not visible on the pics?

Yes, I am using 'D' connectors. It wouldn't let me upload more than three photos... here's the one from the back of the box.

[analogmonster]

Yes, I am using 'D' connectors. It wouldn't let me upload more than three photos... here's the one from the back of the box.

IMG_9149.JPG

Good choice, I'd say. The only thing I still don't know is whether there might be problems in transporting audio signals concerning crosstalk and noise.

[noddyspuncture]

The only thing I still don't know is whether there might be problems in transporting audio signals concerning crosstalk and noise.

No audio runs through the 'D' connectors... it's all voltages & resistances - just like in Emo's... !

[noddyspuncture]

Built the switching circuitry on all three cards and have started wiring one card.... it's took me three days to get this far and there's still loads to add and check..!

[ummagumma]

*whistles*

Impressive!!!

[noddyspuncture]

So here it is... my first time using the preset box which up to now has been over a year in the building.

I also made a section of a close-up of a card where I'm running through and adjusting all of the card parameters...

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

[analogmonster]

Yeah, that's it

Questions:

Do you have to remove the cards from the box to change CV settings?

Why are there three potenstiometers at the front of the cards?

The reverb you used for your demo: Original spring reverb or something digital?

[noddyspuncture]

Yeah, that's it

Questions:

Do you have to remove the cards from the box to change CV settings?

Why are there three potentiometers at the front of the cards?

The reverb you used for your demo: Original spring reverb or something digital?

The cards slide out and all controls can be reached so no "dismantling" is necessary. There are only three 'proper' CV settings actually - the Esus, the fine tune and filter cut-off. The mixer sliders are providing voltages to vactrols so could be classed as a sort of CV. Everything else basically straps across the controls in the synth.

The three mini pots are for fine tuning. I have selected resistor divider values to give me just over a 5th up and down. If you vary values you can tweak it to any interval.

The reverb you are hearing is actually built into the Model 15. I did that first, ages ago. made some videos as well which you can find on my YT channel. I built a 905 circuit and installed a reverb tank from a Hammond Organ - it just fit. I had to shock mount it and also I had to reposition the power supplies and encase them in mu-metal sheeting to minimise the hum pick-up... there is a very slight hum but only audible when no audio is being passed and the levels are turned right up.

[analogmonster]

The reverb you are hearing is actually built into the Model 15. I did that first, ages ago. made some videos as well which you can find on my YT channel. I built a 905 circuit and installed a reverb tank from a Hammond Organ - it just fit. I had to shock mount it and also I had to reposition the power supplies and encase them in mu-metal sheeting to minimise the hum pick-up... there is a very slight hum but only audible when no audio is being passed and the levels are turned right up.

I'm thinking about doing the same. I have a reverb tank of unknown specification and want to access it with a 905 circuit. What analytics concerning the reverb tank do I have to do before trying to access it with the circuit?

[noddyspuncture]

I'm thinking about doing the same. I have a reverb tank of unknown specification and want to access it with a 905 circuit. What analytics concerning the reverb tank do I have to do before trying to access it with the circuit?

The impedances of the driver and pick-up coils need to be correct. I can't remember exactly which is which but you do get different results depending on them. I suppose the cct could be adapted to match but I found it easier to experiment with different tanks as I have a large collection of them.

I'd say just build your 905 cct and experiment like I did...?