Banana jack colour schemes

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Banana jack colour schemes used by modular synth brands for which some reference has been found. Note that there is no universal accepted standard.


In the UK Rapid only sell 4 mm bannana sockets in  black ,  red ,  white ,  green ,  blue  and  yellow .[1]

There isn't always a clear distinction between audio and control signals. It's more important to distinguish between inputs and outputs. There might be some unusual connections such as inputs with restrictions and ground for external patching.[2][3]

Patch cords are color coded to indicate their length.[4]

Buchla 200e

On Buchla synthesizers the audio and contol paths and control are kept seperate. The control path uses EF Johnson banana jacks and swings between +/-15V, while the audio path is at 1.228V RMS, (+4dBu professional line level) and uses 0.141" Tini-Jax.[5][6]

Signal Color[6][3][7] Comment
Pulse input  orange  Gate/trigger/clock.
Pulse output  red  Gate/trigger/clock. Until the late 70s red was for both pulse input and output.[8]
CV input  black  or  grey  Grey for 292e velocity CV in.[9]
CV output  blue ,  green  or  purple  Green is second channel/style of some CV out (e.g. velocity out), purple is third channel/style of some CV out (e.g. 296e even outs).[9]


Most modular synth signals can be thought of as either audio or control. The system ground jack provides a ground for connecting to external systems with screened (3.5 mm or 1/4") jacks, so that the signal can be carried with single wire cables (white in Bugbrand interface packs).[10][11]

Signal Color[12] Comment
CV in  blue 
CV out  red 
Audio in  yellow 
Audio out  green 
System ground  black 

Castle Rocktronics

Tries to have a different colours for each different type of input, although just one colour for all outputs.[13]

Signal Color[13] Comment
Output  red  Often audio, but also CVs, envelopes and triggers.[13]
Input  black  Audio, CV or digital. Examples: Filter input, mixer input, data input.[13]
CV in  yellow  Envelopes, LFOs and other analog control signals. Anything where the actual voltage matters. Examples: Cut-off frequency, gain.[13]
Clock in  blue  Digital. Not necessarily a fixed frequency, any input that causes the circuit to “step forward” by one on a rising or falling edge. Examples: Counters, step-sequencers.[13]
Trigger in  green  Digital. One-shot events that trigger on a rising or falling edge. Examples: percussion, resets.[13]
Gate in  white  Digital inputs that act according to whether they are high or low, rather than triggering on an edge. Examples: Analog switches.[13]


CGS mostly uses the Serge scheme, sometimes colorful just for fun.

Signal Color[14][15][16] Comment
Audio or signal  black  AC coupled signals
CVs  blue  DC coupled signals
Pulse in/out  red  Trigger signals
Wired-OR capable gate/trig output  orange 


Cool colors are inputs and hot colors are outputs.

Signal Color[17][18][19] Comment
Ground  black  To connect other gear.
CV in  blue 
Clock/trig in  green 
FM in  purple 
Pulse out & clock/trig in  brown 
Random out  grey 
Audio out  white 
Ultrasound out  yellow 
Pulse out  red 
CV out  orange 

Elby Designs Panther

Elby Designs Panther 3.5mm (EuroRack) and 4 mm banana jacks colour scheme is expanded from the one used by Serge (AC, DC and logic). Differentiating between input, output and special for each signal type.[20]

signal colour comment
in out special
AC  black   white   grey  e.g. VCO
DC  blue   green   purple  e.g. CVs
Logic  red   yellow   orange  e.g. gates and triggers

Loudest Warning

People have also used the Serge STS or Random*Source schemes.

Signal Color[21][22] Comment
CV in  blue 
CV out  grey 
AC/audio in  yellow 
AC/audio out  green 
Logic/trigger/gate in  white 
Logic/trigger/gate out  red 
Sync in  purple 
Special out  orange  e.g. wirable OR
Ground  black 

Kilpatrick Audio

Front panel

Regards audio and control signals as interchangeable.[23]

Signal Color[23] Comment
CV/audio input  black 
CV/audio output  grey 
Pulse and gate Input  white 
Pulse and gate output  red 

Internal power

Signal Color[23] Comment
+15V  red 
-15V  grey 
AGND and DGND  black 


Signal Color[24] Comment
Signal in  grey 
CV in  white 
Signal or CV out  yellow 
Gate/trigger/logic/sync in or out  red 


The Serge scheme is more about the type signal than its function but with some flexibility e.g. some CVs can go negative. Many black inputs are AC coupled, but most black outputs are not.[25][26]

Signal Color[27][28][29] Comment
Trigger pulses in/out  red 
CVs in/out  blue 
Bipolar CV in/out  black 
Audio in/out  black 
Special functions in/out  yellow , orange , green [30]
Sync in  purple  Pink noise out on the Animal panel[31][30]
White Noise out[32]  grey 


  1. ^ 4 mm Insulated Test Socket, Rapid Electronics Limited
  2. ^ Frac rack Banana Jack...some spec guidlines, Electro-music forum, March 2009
  3. ^ a b If you could color code your inputs...., Mod Wiggler forum, April 2010
  4. ^ Buchla 200e User's Guide, p. 2
  5. ^ Why Buchla?, Buchla tech blog, 4 Oct 2008
  6. ^ a b The Good Thing About Standards: So Many To Choose From, Buchla Tech blog, 7 October 2007
  7. ^ Buchla 200e: Part 1 by Gordon Reid, SOS, Dec 2005
  8. ^ The 266 project, Buchla tech blog, 4 Oct 2008
  9. ^ a b serge jack color logic, Mod Wiggler forum, May 2011
  10. ^ OldBlue Overview (archive), BugBrand
  11. ^ Connecting eurorack with bugbrand 1 frame (grounding), Mod Wiggler forum, Jan 2016
  12. ^ Technicals, BugBrand Modular Synth
  13. ^ a b c d e f g h Power distribution & system overview, Castle Rocktronics
  14. ^ Serge Fans FAQ
  15. ^ Serge Guidebook by Rich Gold.
  16. ^ Ken Stone
  17. ^ Plumbutter by Ciat-Lonbarde
  18. ^ serge jack color logic, Mod Wiggler forum, Mar 2013
  19. ^ Plumbutter 2 quick start, Mod Wiggler forum, Jan 2018
  20. ^ Panther Jacks – 3.5mm and 4 mm Coloured Jacks
  21. ^ Charlie Kerr
  22. ^ [IC] 4U Single Function 'Sergesque' panels, Mod Wiggler Forum, 20 Aug 2014, 09:24
  23. ^ a b c Kilpatrick Format Technical Specifications
  24. ^ Modcan A Series manual
  25. ^ Serge Maintenance Info, Mod Wiggler forum, Nov 2010
  26. ^ If you could color code your inputs...., Mod Wiggler forum, Apr 2010
  27. ^ Introduction to the use of the Serge Modular Music System, 1976, p. 14
  28. ^ Serge Fans FAQ
  29. ^ Serge Guidebook by Rich Gold.
  30. ^ a b Best of CGS Build Thread, Mod Wiggler forum, 1 Jul 2011
  31. ^ The Serge "Animal" - a massive modular in 4U
  32. ^ Serge Maintenance Info, Mod Wiggler Forum, Nov. 2010

External links