From: croehrig@cs.ubc.ca (Chris Roehrig)
Subject: Re: Wanted: info on Rhodes Mark I Stage Piano (Seventy-Three)
Keywords: electric piano Rhodes 
Organization: Computer Science, University of B.C., Vancouver, B.C., Canada
Date: Fri, 31 Jul 92 20:27:08 GMT


Hi Rob,
   I picked up a Rhodes 73 Mk I last year and went through the same thing.
I found virtually no one who has any experience with it and had to forge 
ahead on my own.   I ended up building an internal preamp (gain of ~10,
I think) and an equilizer with a 2nd order band-stop at around 700 Hz to
get rid of some of the muddiness and a 2nd order roll-off low-pass filter
with moveable corner frequency (from 2kHz to 15 kHz, I think).
  I played around with a graphic e.q. for a while before I decided on this
but now that I've been playing it for a year, I'd forget about the low-pass
filter;  I like the brighter sound, even if the clanging tines are inharmonic.

I also spent a *lot* of time setting up the action.   It can get quite
complicated since each tine has 4 adjustments you can make, all of which 
interact and affect the tone dramatically.
(The tone I was after was the somewhat distorted, overdriven-pickup funky
Rhodes sound, a` la Jeff Beck, Emuir Deodato, Chick Corea, etc.  I'll
assume that that's the same kind of tone you're after.)

The Rhodes sound has two components:
    1)  the vibrating tine:   Mathematically, a vibrating rod that is fixed
at one end gives an inharmonic spectrum.  This is the clanging sound that
you hear when you strike a key.   It dies out fairly quickly and isn't
really the interesting component.   After it disappears, all that is left
is a pure sine wave.   This is what you have to work with for the second
component:
    2)  the overdriven pickup:  The cool funky Rhodes sounds comes from the
magnetic pickup when it is overdriven by the vibrating rod, causing
_harmonic_ distortion.   This is where you change the tonal
characteristics.

Setting up a Rhodes:
There are 4 adjustments to make to each key:
    1)  Tuning it:   move the spring along the tine with a small flatblade
screwdriver.   Warning:  depending on how the tine is situated relative to
the pickup, the pitch can vary over the course of the note.  It helps
enormously to have a good chromatic tuner handy.
    2)  Tine height:   Basically the distance from the tine to the hammer.
(The tine is the small round rod; not the big rectangular brass rods --- 
they are there just for sustain.)   This determines the keyboard's "action".
It's a good idea to get the tines fairly close (down low) to the hammers so 
that you get a good responsive action.  You adjust this with the two mounting 
screws.
    3)  Tine angle: This determines where the tine is located relative to
the pickup.  This is the most important adjustment and is what determines the 
"tone".  You also adjust this with the two mounting screws.
    4)  Pickup position:  Loosen the bolt securing the pickup, and you can
slide the pickup back and forth.  This determines the distance from the
tine to the pickup, and affects how much the pickup is overdriven as well
as the relative volume of that key.   You basically want it as close as 
possible without hitting (you'll have to experiment with pounding on the 
keyboard to get it really close), and then make adjustments so that all
keys are at a uniform volume (and tone!)

These adjustments all interact, so it's not as simple as it seems.
To set up the tone, you have to adjust the position of the end of the tine
relative to the pickup.  Here's the side view:

          -----
----------     \                           tine                 |    |
    Pickup      |   ============================================|    |
----------     /                                                |    |
	  -----                                                 ------


If you position the tine in the dead center of the pickup, you'll get a 
strong fundamental frequency (sine-wave sound) which tends to sound muddy,
and is not at all the sound you are after.
If you move it up or down a bit, the fundamental dies away and the second
harmonic becomes dominant.  This has a more funky sound, like a
Stratocaster in the out-of-phase pickup position  (this is the sound you
want).    It doesn't make a difference to the tone whether you move it up or 
down, but it does matter to the action, so you might want to experiment a bit.   
It also makes a difference in the tuning.   If the tine is in dead center, 
the tuning doesn't change while the note sounds, since it is vibrating 
symmetrically about the axis of the pickup.   But if you move it up or down, 
then as the amplitude of the vibration changes, the tuning actually shifts
slightly (in different directions depending on whether the tine is moved up 
or down).  On some keys this can be quite noticeable, and it gets quite 
frustrating to tune the thing and still get the tone you want.   It's best
to leave tuning until the end.

You also want the tines to be in the dead center of the pickup when looking
at them from on top; otherwise you won't be able to get the keys uniformly
close to the pickups and with uniform tone.   This is not as easy as it
seems;   the factory seems to have slammed the screws through the rubber
grommets and into the wood without a lot of care --- a lot of the grommets
are out of position and out of shape.   A lot of the screws were bent on
my instrument as well.   As it looked impossible to find replacement
grommets, I boiled my grommets for quite a while in an attempt to restore
them to their original shape, but with limited success.   I also replaced
every mounting screw with stronger, straight ones.  Even so, some keys are
still off-center.  (Note that you can shift the entire pickup plate by
loosening the huge screws at either end.)

To get the tines as close to the pickups as possible, I also ground down
every tine to be butt-flat.  (The factory seems to have just broken them to
length and they had jagged ends.)

While I am happy with the low and midrange tone, things seem to abruptly
change around C4 and I can't get a funky tone any higher than that.
I suspect it may have to do with the pickup wiring:  they are wired in
parallel in blocks of 6 or 8 or so, and the blocks are wired up in series.
I don't know why this is and haven't done any experimenting with it yet.
Does anyone know what the differences between Mark I and Mark II are?

Chris Roehrig
University of British Columbia
Newsgroups: rec.music.makers