EML 101 mods
2003-10-08 by David Cornutt
I sent this out to synth-diy a couple of days ago, but I
thought I'd send it here too...
EML 101 owners: What mods have you made or considered to
your synth? I'm about to undertake a set of mods with mine, and
I thought I'd ask around to see what other ideas there are out there
while I've got mine on the bench. Here's what I'm thinking about
right now:
* An input jack to override the KB1 control voltage. This should
be fairly easy; I'll tap in at the OSC 2 control mode switch. I'll
replace the CM2 output jack with a switching jack that will
override the source when a patch cord is plugged in. This will
provide me with a more usable CV input point for a MIDI-to-CV
interface. (A note here: I still want to be able to use the keyboard
when I'm playing with patches, so I don't want any mod that
permanently disables the keyboard jack.)
For the mods below I'll appropriate one of the groups of
multiple jacks:
* An input jack to externally gate envelope 1. My 101 already
has an external gate in for envelope 2; I'd like to have separate
gate ins for each envelope. This gives more flexibility in connecting
the gate out of the MIDI-to-CV interface (as opposed to hacking
in to the keyboard jack).
* An input jack to override the oscillator 1 source input to the
sample-and-hold. The fact that the S/H source is hardwired to
OSC 1, with no patch point is about the only thing I think they did
really wrong with the original design.
* A jack to access the output of exponential amp 3, which is
dedicated to the filter in the original design. The main use for
this would be to have a V/Hz control voltage source for use with
oscillator 1, which lacks its own exp amp and so doesn't track
properly if you feed it a V/octave CV. But I could see it being
put to other mischief...
* A input jack to override exp amp 3's connection to the filter.
This way, I could drive the filter with an external source while using
the filter mixer, and exp amp 3, for another purpose.
What other ideas are out there? One that I've heard of is a mod
to the filter to eliminate the attentuation that occurs when you turn up
the resonance (and prevents the filter from self-oscillating). Is the
EML filter suitable for this kind of thing? (I have a feeling it isn't,
which is okay; it's a unique filter and I can get self-oscillating
filters
elsewhere.) I'd like to avoid doing anything that would be
irreversible;
I'd like to be able to put it back in factory spec if I decide to sell
it
someday.
P.S.: one reason I've got it open is that the keyboard S/H suffers
from S/H droop. Is this likely to be just the capacitor, or am I
possibly looking at having to replace one of those FETs?
thought I'd send it here too...
EML 101 owners: What mods have you made or considered to
your synth? I'm about to undertake a set of mods with mine, and
I thought I'd ask around to see what other ideas there are out there
while I've got mine on the bench. Here's what I'm thinking about
right now:
* An input jack to override the KB1 control voltage. This should
be fairly easy; I'll tap in at the OSC 2 control mode switch. I'll
replace the CM2 output jack with a switching jack that will
override the source when a patch cord is plugged in. This will
provide me with a more usable CV input point for a MIDI-to-CV
interface. (A note here: I still want to be able to use the keyboard
when I'm playing with patches, so I don't want any mod that
permanently disables the keyboard jack.)
For the mods below I'll appropriate one of the groups of
multiple jacks:
* An input jack to externally gate envelope 1. My 101 already
has an external gate in for envelope 2; I'd like to have separate
gate ins for each envelope. This gives more flexibility in connecting
the gate out of the MIDI-to-CV interface (as opposed to hacking
in to the keyboard jack).
* An input jack to override the oscillator 1 source input to the
sample-and-hold. The fact that the S/H source is hardwired to
OSC 1, with no patch point is about the only thing I think they did
really wrong with the original design.
* A jack to access the output of exponential amp 3, which is
dedicated to the filter in the original design. The main use for
this would be to have a V/Hz control voltage source for use with
oscillator 1, which lacks its own exp amp and so doesn't track
properly if you feed it a V/octave CV. But I could see it being
put to other mischief...
* A input jack to override exp amp 3's connection to the filter.
This way, I could drive the filter with an external source while using
the filter mixer, and exp amp 3, for another purpose.
What other ideas are out there? One that I've heard of is a mod
to the filter to eliminate the attentuation that occurs when you turn up
the resonance (and prevents the filter from self-oscillating). Is the
EML filter suitable for this kind of thing? (I have a feeling it isn't,
which is okay; it's a unique filter and I can get self-oscillating
filters
elsewhere.) I'd like to avoid doing anything that would be
irreversible;
I'd like to be able to put it back in factory spec if I decide to sell
it
someday.
P.S.: one reason I've got it open is that the keyboard S/H suffers
from S/H droop. Is this likely to be just the capacitor, or am I
possibly looking at having to replace one of those FETs?