There are presently three different types of Eurorack power supplies available - Linear, Switched Mode and Hybrid (Switched Mode
with Linear post regulation).
Linear power supplies, which were used exclusively on vintage analogue synthesisers, are very low noise and very suitable for sensitive
analogue modules such as the Gemini 2412 filter. Likewise, hybrid power supplies such as the Doepfer PSU3 are also very low noise
and equally suitable. Switched Mode supplies are generally usable; however, under certain conditions some switched mode power
supplies can be problematic - this is because of the way in which they work - they switch the power rails at a very high frequency
(typically between 100kHz and 1MHz) and the resultant power line noise noise can be up to 150mV per rail, however it is argued that
this is well above the audio spectrum and is therefore inaudible - but we have found that in some cases (due to load level, asymmetric
loading etc) that heterodyning can bring this down into the audio range, so we may experience up to 150mV of digital hash on the
power rails at audio frequency. The powerline noise rejection of the module itself cannot remove such high levels of noise and it can
therefore find its way to the outputs of the module itself where it can be heard as low level noise on the output. Thankfully this is a
fairly rare occurance, but if excessive noise is noticed on the GEMINI 2412 outputs then the first thing to do is try it with a different
power supply - ideally a Linear or Hybrid suppy.
Also, there are a few Eurorack modules which are badly behaved and can introduce noise back onto onto the Eurorack power rails too
- the way to find these is to disconnect all modules from the case, then re-connect modules one at a time while monitoring the output
of the GEMINI 2412 until the culprit is found.
This information relates to analogue Eurorack modules in general - most modern Eurorack modules are digital in nature and much
more tolerant towards power line noise than their sensitive analogue counterparts!
GEMINI 2412 - Specification
Information on suitable Eurorack power supplies:
Dual 12dB / Octave state variable filters, with integrated panning
mixer, Dual Frequency CV source with external input and CV panner,
Audio Inverter and switchable combination modes.
28HP x 3U Eurorack,
141mm x 128.5mm
+12V, -12V and a 10 pin to 16 pin Eurorack power cable is supplied.
Reverse polarity protection is built in.
Power consumption: Positive rail: 50 mA, Negative rail: 45mA
IN 1 & IN 2 - Expected signal level 10V p/p, centred around 0V. Audio
signals only, DC signals are ignored.
All VCF outputs are nominally 10V p/p, noise <35mV
FCV 1 & FCV 2: - The accepted signal range is -5V to +5V. Any voltages
higher or lower than this will be capped to +5 or -5V. Maximum
permissible voltage to this input is +/-12V.
D-FCV: The accepted signal range is -10V to +10v, and the maximum
permissable voltage to this input is -12V to +12V.
RES CV & MIX CV: The accepted signal range is 0V to +5V. Any voltages
higher or lower than this will be capped to 0V or +5V, so negative
voltages are ignored. Maximum permissible v,oltage to this input is
+/-12V.
Description:
Dimensions:
Power usage:
Inputs:
Outputs:
CV Inputs:
