Gone Bananas . . .

Mark McLemore mgm at io.com
Tue Aug 1 00:04:34 CEST 1995

Thank you all for the feedback and advice on connectors
for modulars -- I'm going with banana plugs.  The 1/8"
miniplugs were ruled out almost instantly due to their
overall "cheezyness" (looseness, easy to break, etc..).  
The matrix of TRS jacks is a worthy idea, but I'm definitely
going open-ended modular (add as I build modules), so I 
can't predefine the matrix in advance.  So it came down 
to a shootout between the 1/4" phone plugs and bananas:

1/4" Phone plug Pros:
   - Sturdy, reliable.
   - Ergonomic (big plugs, big cords).
   - Shielded from noise.
   - Readily available parts.

1/4" Phone plug Cons:
   - Expensive use of panel real estate.
   - Can cause ground loop hum.
   - Relatively costly.

Banana Plug Pros:
   - Uses less panel real estate than 1/4".
   - Much cheaper than 1/4".
   - Can stack for multiples.
   - Minimizes ground loop problems.
   - Can color-code (i.e., black - in; red - out).
   - Compatible with Serge panels

Banana Plug Cons:
   - Unshielded cables can pick up noise.
   - Incompatible with existing equipment (my other 
     synths, mixers, microphones).

I re-did my panel layouts with banana jacks over the
weekend and found that each module required only 1/2
to 2/3 the panel space of the 1/4" versions and I even 
had a few more inputs/outputs to spare.  I was able to 
fit most modules into either the single space or double
space FracRack panels sizes (when using 1/4", almost 
every panel required three spaces).

As far as ergonomics, the banana plugs feel big enough 
and plenty solid to me, and far less clunky than 1/4" 
phone plug.  A couple of 1/4"-to-banana panels can solve 
interfacing to other gear; the preamp/envelope detector 
will have both XLR and 1/4" inputs, and the mixer output
panels will have +4dbV 1/4" unbalanced outputs for the 
studio mixing console.

So, the only remaining question was one of noise 
immunity due to lack of shielding.  I opened up the 
Yamaha Sound Reinforcement handbook and found a 
worse-case example of noise from an SCR light dimmer 
which induced a peak signal of around -30dbV.  A typical 
module signal of +/-5V (10V p-p) can be roughly converted 
to dbV by:

        Module dbV = 20 * log( 10 / 1 ) = 20dbV.

Then, worst case, the difference between, say the 
output of a VCO and induced SCR noise would be 50dbV.  
I'm sure that's far better than the ground loop hum that I
would get with shielded cable.  Anyway, I don't have any 
SCR light dimmers, flourescent lights, or Van De Graaf 
generators in my music studio (although the latter would 
certainly look cool next to a huge modular -- "this is 
what I power my synth with" :-).

Mark McLemore  ~  mgm at io.com

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