Cgs synth

Ok

So making sure each jack sleeve lug has a low resistance path to pcb ground via wire. They are all connected via metalwork to the ground on the next module as well though! But is that insignificant because aluminium/steel etc has a much higher resistance?

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On 10 Feb 2018, at 14:51, Richard Brewster pugix@yahoo.com [cgs_synth] <cgs_synth@yahoogroups.com> wrote:

Regarding the 0v connection for panel jacks, the method used by Synthesis Technology (MOTM) for the 5U modules is to run a shielded cable from the PC board out to each jack.� The shield is connected to 0V on the PC board and to the sleeve lug on the jack.� Point being that there is no worry about ground loops.

For CGS boards that I built myself I often ran a twisted pair, instead of shielded cable, from the board to each jack.� Sometimes there were not enough ground lands in the PC board, so I had to improvise a little.� For some connections to jacks I ran a single wire, but then wired all the jack grounds together and brought that back to the board.

Richard Brewster
http://pugix.com

On 2/10/18 8:59 AM, Mike Burnham mikejburnham@hotmail.com [cgs_synth] wrote:

When I built my modular I was in such a rush to get it built I made no plans as regards layout, ergonomics, power and grounding and I placed modules next to each other as I built them and hooked them up to power supplies with whatever wire I had around.
When I finished a 64mu system I gave myself a big pat on the back, jammed around for a couple of years then started to get annoyed with its many failures and inconsistencies. Cheap crackly pots and jack sockets, noise, hum, strained power supplies, faults and incompatibilities between modules. As a result I gradually fell out of love for it and it became mere eye candy for my studio punters.

Anyway last year I got tired of just looking at it, realised what a powerful instrument it could be and decided to get the system running to its maximum capability. Wow what a mission! The more work I did on it the more I realised how much was wrong!

Well I'm well on the way now and I've corrected a lot of problems that have been bugging me for years. However although my skill in electronics is leagues better than when I first built modules I realised that there's a few holes in my understanding that I really need to clarify. I'd really appreciate some help on this.

Screened cable

I realised that in my whole modular I have only used screened cable a couple of times. To connect a spring reverb tank and the CGS real ring modulator. In pro audio, screened cable is generally used for every audio connection. Should I be using screened cable connected at the PCB end for audio�connections to front panels? I believe not.�I generally see in module builds that�screened cable is not often used. The reason for this I believe is this correct me if I am wrong. That�screened cable is only completely necessary for low level high impedance�connections for instance microphone and pick up inputs, mix buss connections. Audio levels on a modular a�sufficiently big for this not to be a problem and wire lengths are short back to the PCB. Also screening only achieves its goal if the module is completely shielded in a chassis which is grounded. This is not the case with most synth modules which only have metal front panels and sometimes not even metal.

Chassis, jack sockets, grounding

Is it necessary to connect the sleeve of�jacks back to�PCB 0v

On my module builds I�started with one scheme and stuck to it. I connected the 0v to all controls that needed it and then to one jack socket's sleeve connection. The rest of the jack sleeves are connected via the panel aluminium (providing the jacks are�tightened!).

On a Neve mixing console (which are completely hum/noise free) electronics ground and chassis ground are kept separate and only connected to the consoles power�input ground and�at this point only.

Is my module ground/panel wiring ok or would it be better to not connect the jack sleeves/front�panel back to the PCB 0v but all module jacks/panels are connected via screwing to an�aluminium fixing rail which at one point is connected to the power supply ground and mains earth directly? Or is this overkill and unnecessary? It seems as if my module grounding�scheme (and most others I can see on the�web) would induce more ground loops due to the fact that the metal is connected to both its own PCB 0v and all the�other�modules in a cabinet through touching front panels?

Layout

Like I said I never payed much attention to layout. But I figure that I should try and separate different kinds of modules into their own power supplies and rows in a cabinet for ergonomics also.

All digital, gate and pulse, LED heavy modules, sequencers etc should should have one separate�supply.

Cheap jacks and pots

I've bought a lot of cheap Chinese jack sockets in my time. Because of the shear amount of them I wanted to save money. But it seems like that was not a good idea. What is other peoples experience of how�different sockets hold up over time? I guess the encapsulated types are the best way to go because it affords more protection from the corrosive elements but even these won't be completely immune to corrosion. Is the real problem the quality of the�plating? I guess you get what you pay for.�

Pots. I bought most of the pots from Dick Smith in Australia as I was living there at the time and they were nearby and cheap. They look like Alpha pots but I cannot find a manufacturers identifier. My experience is that a lot of them have become really dirty/crackly over time and can be really annoying especially in sequencer CV pots and VCO tuning pots. What do people recommend as good pots that exhibit reliability and are also reasonably priced.

However these problems are not helped by the fact that I built horizontal cabinets for 16 modules each and the backs of these cabinets are open. So there is little protection from the environment. I guess thats just common sense. But things are only apparent over time

Phewww! Thats it for the moment.�

Many thanks for any help�

From: Mike Burnham <mikejburnham@hotmail.com>
Sent: 10 February 2018 12:08:11
To: Mike Burnham
Subject: Modular layouts, power and grounding schemes

�

When I built my modular I was in such a rush to get it built I made no plans as regards layout, ergonomics, power and grounding and I placed modules next to each other as I built them and hooked them up to power supplies with whatever wire I had around.
When I finished a 64mu system I gave myself a big pat on the back, jammed around for a couple of years then started to get annoyed with its many failures and inconsistencies. Cheap crackly pots and jack sockets, noise, hum, strained power supplies, faults and incompatibilities between modules. As a result I gradually fell out of love for it and it became mere eye candy for my studio punters.

Anyway last year I got tired of just looking at it, realised what a powerful instrument it could be and decided to get the system running to its maximum capability. Wow what a mission! The more work I did on it the more I realised how much was wrong!

Well I'm well on the way now and I've corrected a lot of problems that have been bugging me for years. However although my skill in electronics is leagues better than when I first built modules I realised that there's a few holes in my understanding that I really need to clarify. I'd really appreciate some help on this.




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