[sdiy] Pots vs Encoders, was Re: [sdiy] dave smith *instruments*

[Mike Pepper]

I'm doing a broad strokes reply, so have not quoted.

There is very much a horses for courses thing here, and also a sad
reflection that the synth business is still making a fairly basic use of
encodres and control surfaces in general.

Outside our world, encoders are used very well in test equipment and
communications gear. Often the encoder will have it's own dedicated micro
attached. One of my 'scopes, and several communications receivers I have
worked on/with implement 'ballistics' on the encoders, where faster turn
rates speed up the update rate. In comms gear this helps simulate the
flywheels fitted to  older mechanically tuned devices, and Cheater is right
about muscle memory, though it applies here too - I've seen Air Force radio
techs tuning very rapidly to a new frequency with a swift flick of the knob
followed by a slower fine tune. They often seem to have the knack of landing
the fast setting just below the needed frequency, (like 'aiming off' in
orienteering), and then zeroing in with the knob in slow mode. Ballistics
can be switches in and out, and in some cases, personally preset.

Instruments like violins are not just muscle memory driven, though it is
important. I was once. as a young lad, helping at a recording sesson, and
couldn't understand why very nice female violinist didn't like the playback.
She asked me to try and play her violin, to much amusement all round, but I
quickly realised that she was getting a lot of her sound by bone conduction
through the chinrest, and more tactile feedback via her string and bowing
fingers. The thing felt alive! I later made more use of this knowledge when
dealing with any insrtument where the player has such direct contact - most
wind and stringed instuments do this to some extent.

Synth type instruments, (and I include it's distant ancestor the pipe organ
here), don't provide as much feedback. If you've ever played a direct action
pipe organ, you'll know that the chord attck is much better than that of an
electric action - the player can feel the servo effect of the wind snapping
the pallets open, (a kind of 'stiff then loose' feel). Even a piano provides
some tactile feedback. The speed advantage of plastic keyboards is
wonderful, but seems to come at the cost of expression. Funny, but I think
it might take more technology to add expression to synths than the note
generationg part uses.

I've been working on a variant of the 'Pultec' equaliser, for mastering use.
The post are replaced with resistor stacks that should provide 05,dB steps,
and the capacitors are switched in parallel to give more turnover
frequencies than the original, whilst keeping the standard fequencies. I
started with rotary switches, but the wiring got nasty, and went instead to
good quality reed relays.  I added a micro to control the relays, and
hopefully, once I have a display format I like, I will have an old style
Pultec, but with perfect snapshot and recall. Encoders are the only sensible
choice here, and will track fast enough if some idiot wants to try doing
special effects. Opticals, or encoders made from old stepper motors are
probably the way I will go.

For a performance resonance control, I can't see a better solution than a
real pot or pot type controller, (wheel, joystick etc). By the way: I have
changed out quite a few high grade conductive plastic ones in my time, they
just take longer to wear out, but the contacts or the tracks will fail
eventually. My personal take though, for performance, would be to have
patchable performance controls, and route them where needed, some controls,
are less likely to get repeatedly tweaked than others, but if you are
playing music where you do a lot of that, is patch recall a big thing? Part
of the interest, to me, of electronica is the interaction between the UI and
the player. Personally, I actively dislike VSTs, unless I can have a control
surface hooked in. I got lucky with a cheap batch of small cermet pots and
have been thinking of a MIDIbox64 style unit, with plug-on panels, laid out
for different intruments, and bankstick patch storage to go with them,
taking me back to my days with analogue computers, another ancestor of the
modular. On my Electronic Associates TR-48, (now in the Bletchley Park
Computer Museum), the whole patch panel could be dismounted, (with a kind of
60's chic Thunderbirds style motorised thing), you still had to restet the
grid of 10 turn pots by hand though.

It's back to a personal choice, in the end: you can't get instantaneous
recall with a pot, you can't fast tweak a cheap encoder. Our call.

(sorry for the meandering post - it gets me this way sometimes)

||\/||ike