Gone Bananas . . .
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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