The Doepfer A-100 system uses a 16-pin IDC connector with the following pin assignment:-

The main issues with these assignments are:-

1. Only 2 pins are assigned to +12V which, in addition to 0V (which has 6 pins), is the most heavily loaded power rail

2. Having +12V on pins 9, 10 mean there is no room on the PCB footprint at all to expand tracking to these pins so compromising current capacity and track impedances

The specification changes are as follows and simply involve removing the +5V and CV/GATE lines from the Power Bus and enhancing the definition of the main power rails:-

Busboard designs should aim to achieve an absolute maximum impedance for all power rails of 10milliOhm. This measurement is for any power terminal on a module to its source at the main power supply connection and so includes modules power cables and any busboard-busboard and busboard-power supply connections.

Many EuroRack modules currently use a 10-pin IDC connector as these modules do not require accesws to the CV/GATE buss and either do not require a +5V power rail or generate it internally. The change of busboards to usinga 10-pin IDC header instead of the standard 16-pin header only really impacts the EuroRack market in that the user would need to change the module power cables.

For those modules requiring access to the CV/GATE signals it is proposed that a separate 'DATA/CV/GATE' bus be implemented, and those few modules requiring an external +5V power rail, the inclusion of an inline adaptor is a suggested solution.

IDC connectors have a relatively high contact impedance (typically 30mΩ) compared to, say, 0.156" MTA (typically 10mΩ). To retain backward compatibility with EuroRack, It is proposed that the EuroSynth system retain the IDC header but utilise crimp terminals as shown here.

The basic arrangement of the power pins remains the same as that for EuroRack so any EuroRack module can be fitted in to a EuroSynth system although it will require either a 16-pin to 10-pin power cable or a 10-pin to 10-pin power cable. Normal IDC ribbon cables with an insertion-displacement mechanism can also be used if desired.

Mains Earth Grounding (*)

It is expected that most EuroSynth systems will use an external DC power supply. It is a requirement that these be fully compliant Class II supplies with appropriate certification from the users country. The use of these double-insulated power supplies negates the specific need to apply earth bonding for all metalwork in the EuroSynth. This does not, however, change the need for providing chassis ground to prevent static build up and subsequent discharge. It cannot be under-emphasised that the topic and application of EARTH Grounding and Chassis Grounding to any system must be done under the strict guidance of a fully licensed electrician and/or people both qualified and authorised to implement them.

Chassis Ground (*)

Chassis Ground is to be used solely for providing a ‘ground’ connection for the metalwork in a system and for screen connections and should not be connected to 0V accept at the designated point.

Panel mounted components that have a leg (or legs) that will be connected to the chassis when installed, must not have a PCB connection to the modules 0V rail.

Example of EuroSynth Grounding Practise

5V Deletion

The EuroSynth specification does not recognise 5V as a standard power rail and so has removed it from the power system.

Any EuroRack module that requires an external 5V rail will need to use an inline 12V-to-5V adaptor such as the EURO-5V. It is also possible to use a -12V-to-5V adaptor given that the adaptor pays due attention to emissions and does not pollute the -12V rail with switching noise.

CV/GATE Bus

Few modules, currently, utilise the CV/GATE pins. Also, the single CV/GATE pairing is only really beneficial in a single-voice/monophonic system.

As such, EuroSynth is dropping these pins from the power bus. A separate 'DATA BUS' will be defined later.

Power Rail Specification

Both the +12V and -12V should meet the following criteria:

• Voltage Tolerance - better than +/-10mV
• Load Regulation - better than +/-10mVRMS
• Output Noise - better than +/-10mV between 10Hz and 10kHz

All module cables must assign pin 1 of the IDC socket to electrical pin 1 (i.e. -12V) to ensure correct orientation of module power cables.

All modules and busboards should use 10-pin boxed headers to ensure correct orientation of module power cables.

To promote a more integrated system permitting easier mixing of products from different manufacturers the proposal recommends that all power-to-busboard and busboard-to-busboard connections be made via 1/4" quick-connect terminals.

NOTE:

Removal of the +5V rail and CV/GATE still allows existing busboards to continue to be used. EuroSynth modules use a 10-pin header so just need to use a 10/16-pin IDC cable (which is already a common part in EuroRack) or a 10/10-pin IDC cable.

(*) The information given here is for guidance only. Manufacturers/designers must employ suitably qualified personnel (eg fully licensed electricians) to ensure that the final equipment is fully compliant with the relevant electrical health and safety regulations for the country of use. This may involve submitting the equipment for safety testing.