Original MIDIJACK Advanced Installation Techniques
Most
advanced
installation techniques will void the Synhouse factory warranty for the
Original MIDIJACK, but some installers will choose to venture outside
this product protection due to their experience in such matters. The
Original MIDIJACK is a high-technology, microelectronic board
with all surface-mount electronic components that is entirely
machine-made
because it cannot possibly be hand-soldered reliably due to the small
size
of the parts involved and the PC board cleanliness required by the
high-speed
circuitry. As a general rule, soldering on the top of the Original
MIDIJACK board will void the warranty. There are a few solder pads
that are drilled and can be soldered by hand from the lower side of the
board. There are many possibilities for customization not described
in the Quick Installation Manual
that are listed here:
1) The MIDIJACK #8 violet wire
(auxiliary
MIDI function input) is not an analog input or output. It allows
control of the MIDI function button by momentarily connecting this wire
to ground. The MIDI function button is a normally-open, momentary
contact SPST (single-pole, single-throw) switch that has one end
of the switch connected to the computer and the other end connected to
ground, so that when the button is pressed, the computer input
is grounded, causing the use of the button to be detected. This is
known as an active-low switch configuration. The MIDIJACK
#8 violet wire is connected in parallel with the computer input line,
so that touching this wire to ground is the same as pressing the MIDI
function
button. This wire can be soldered to a new jack (or existing jack
rewired) on the panel, so that a standard normally-open footswitch
may be plugged in and used onstage to access the functions of MIDI
channel
selection, MIDI panic button, MIDI Off mode, MIDI On
mode, single note triggering, multiple note triggering, and MIDI
transpose select mode. The wire could also be connected
to a switch the synthesizer already has to make for a more discreet
MIDI
installation. If the installer preferred the look of some switch
other than the factory-installed part, such as an older, more
retro-looking panel-mount switch, it may also be wired to the MIDIJACK
#8 violet wire (auxiliary MIDI function input) to perform the same
function
while the stem of the factory switch is cut short enough to fit beneath
the panel. Do not put any voltage into this wire. Leave this
wire open (unconnected) or momentarily connect to ground only.
2) The Original MIDIJACK gets power
to operate from the synthesizer in which it is installed. Although
the MIDIJACK has a very high-quality regulated supply of it's own which
allows it to operate with an unregulated input, it is preferable
to use the regulated supply inside the synthesizer when available, and it almost always is. In some cases, there is no regulated
voltage +12 volts or greater and the unregulated voltage inside the synthesizer
must be used, such as in the Minimoog which has only a +10v regulated
supply. When installing a MIDIJACK in a Minimoog, connect the
MIDIJACK #2 red wire to the unregulated supply (which will be fluctuating
somewhere around +20v). As an extra precaution to help stabilize
any voltage ripple which may become audible in the form of unwanted vibrato
in the CV, two solder pads have been placed on the lower side of
the MIDIJACK board to solder a 100 uF/25v (or greater) radial-lead electrolytic
capacitor in place, upside-down, under the board. The
pads are on the end of the board nearest the header for the wiring harness
and the positive side of the capacitor should go in the square solder pad
marked with a + on the silkscreen. Such a capacitor
is readily available from any electronic supply store, even Radio
Shack with their part number 272-1028. This extra capacitor may be
added in any other MIDIJACK installation as well, but extensive testing
has proven this to be completely unnecessary.
3) Sometimes an Original MIDIJACK
installation may be performed in conjunction with a total change in the
configuration of the instrument. Consider an analog synthesizer in
poor condition with broken keys: Searching for replacement keys for
a tiny and unreliable 3 octave keyboard may seem pointless to some users
when the MIDIJACK will give it a 128-note range through MIDI. One
popular solution is to cut off the keyboard and put it in a rack or configure
it as a free-standing
tabletop synthesizer module. When this is done, there will
be no local keyboard signal to bypass with the computer-controlled analog
switching matrix on the MIDIJACK board. For this reason, there
are two solder pads on the lower side of the board that have unswitched
CV and gate outputs. They are marked on the lower silkscreen. The gate output is marked SP1 and the CV output is marked SP2. The
MIDIJACK #3 blue, #4 white, #5 yellow, and #6 green wires
would then be unused. In the case of a Moog installation, the
MIDIJACK #7 brown wire (S-Trigger output, unswitched) would still
be used because the Moog wire is always unswitched. This installation
method utilizing the unswitched CV/gate outputs may also be used for a
synthesizer that did not have a keyboard to begin with, such as an
Oberheim SEM or RSF Kobol Expander, because they have no keyboard
to bypass.
4) With the full heavy-duty
hardware
installation kit, the Original MIDIJACK is very small, only
extending about 17 mm below the panel on which it is mounted. This
allows it to fit most places, but some users may prefer an ultra-low
profile custom fitting which will require removal of the stock factory
hardware. If the two aluminum mounting brackets are removed, the board
can be configured to be only 7 mm thick. In such a case, it could be
mounted with double-sided foam tape. Such tape is sold
in hobby shops as servo tape for radio-controlled (R/C) vehicles. It
could also be mounted with lower profile hardware, and the tall
plastic switch could be trimmed to be shorter. To do this, you must
hold the switch by the stem (not the PC board) in a pair of pliers, and
then cut it shorter. A good way would be to cut it with nippers
and then file it smooth with sandpaper or an emery board.
5) The Original MIDIJACK works in
synthesizers where others don't, such as in the EMS Synthi and VCS-3
Putney, the EML Electrocomp 101, and in the improperly calibrated
Moog Micromoog.
This is due to the nearly infinite analog scaling capability of the
MIDIJACK. It is fully adjustable so that any analog synthesizer with
exponential
VCOs can be controlled, whether it is 1 volt per octave, .9
volt per octave, .32 volt per octave, or 1.2 volts per octave. It is
simply a matter of turning the scale adjustment trimmer up or down. An
EMS Synthi or VCS-3 Putney has an oscillator sensitivity much greater
than 1v/octave, much more like .25v/octave or .33v/octave. This can be
tuned-in perfectly with a MIDIJACK by turning the trimmer
counterclockwise. The Micromoog is
known to deviate from the 1v/octave sensitivity the factory claimed for
it, being something more like .9v/octave. This is no problem
for the Original MIDIJACK, as the trimmer can be turned counterclockwise
until the proper intonation is found. This Micromoog
application is described in great detail in response to a question posed
by a MIDIJACK user posted on the Synhouse website at http://www.synhouse.com
under Analog User FAQs. The EML Electrocomp 101 is known to have
a VCO sensitivity of about 1.2v/octave. A way to configure a MIDIJACK
for this application is to turn the scale adjust trimmer all the way
clockwise, then set the MIDI transpose select mode to transpose down
two octaves (-24
half steps) as described in the Original MIDIJACK Analog User manual.
The trimmer should then be turned slightly counterclockwise until the
correct
intonation is found.
6) On many synthesizers, the
portamento is disabled and doesn't function while the synthesizer is
under
external CV/gate control. This has always been the case with many
synthesizers, even though glide is generally thought to be an
oscillator
function, not a keyboard function. The portamento circuit is
placed between the local keyboard voltage and the CV/gate input jacks,
so when the jacks are used, the keyboard voltage is cut off and so
is the portamento circuit. The portamento circuit needs to be rewired
to function correctly. On most analog synthesizers of this type, the
original circuit may be isolated and inserted where it belongs, between
the CV/gate input jacks and the VCOs. Not for neophytes, this is an
advanced modification for real synthesizer technicians only. The
MIDIJACK is exactly the same as using external CV/gate control, so if
the synthesizer has no glide while under CV/gate control, it
won't with the MIDIJACK, either. The modification suggested
here is not only a good solution for use with MIDI, it is a good
and meaningful improvement to the instrument overall. Generating
glide is so trivial that it may be slightly simpler to build a new
exponential
glide circuit. This can be done quite simply by taking an audio-taper
potentiometer of at least 500K or 1 meg Ohms wired as a straight
variable
resistor (so the resistance goes up when turned clockwise) and
connecting
one end of it to the MIDIJACK #4 white wire (MIDIJACK CV output) and
the
other end to a 10 uF (or greater) capacitor which has the negative end
to ground. The junction of the cap and pot should be connected to
an op amp configured as a buffer-follower. This buffered output goes
to the VCOs. This puts a lag generator between the MIDIJACK and the
VCOs, and you need to find a place to mount the new knob you have
created. If the op amp used is of the standard older variety like
the ones used in the synthesizers themselves, the negative power
pin should be connected to the negative supply in the synthesizer and
not
the ground. If this is not done, the op amp will be unable
to reach ground, causing a tuning problem that will be accentuated
when the MIDIJACK is MIDI transposing -36 for super deep bass, but
the synthesizer octave select is set to 32'. A cross between these
two methods that would preserve the original look of the instrument
would
be to use the original glide pot on the panel, rewired to the new
glide circuit. Before any work is done, check the synthesizer
portamento first. Some synthesizers, such as the Moog
MG-1, Moog Rogue, and Roland SH-101
have
the glide circuit correctly wired in the post-jack position already. If
any of this terminology is not immediately clear to you, you should
not even try this modification!
Warranty
The Original MIDIJACK Quick Installation
Manual must be read fully and understood completely to qualify for
warranty coverage and technical support. Although MIDIJACK technical
support is a part of the warranty, every reasonable effort is made to
provide information to customers after that period has expired. The
Original MIDIJACK is warranted against defects in parts and manufacture
for a period of 90 days from the date of purchase. Warranty covers a
single synthesizer application and becomes void if in the opinion of
Synhouse Multimedia Corporation the Original MIDIJACK has been
subjected to unauthorized service, modification, or unintended
installation or usage. No liability is assumed by Synhouse Multimedia
Corporation for any loss or damage, direct or indirect, resulting from
the use of or inability to use the Original MIDIJACK. More Terms and Conditions
Copyright © 3/15/2010 Synhouse Multimedia Corporation