Lambda + chip question

From Haible_Juergen#Tel2743
Sent Mon, Oct 9th 1995, 18:37

>> I finally found a Korg ES-50 "Lambda". It will be shipped
>Can you tell me/us more about this beast? I've never heard of it.

My lambda arrived on Friday, and first I was a little dissapointed.
It didn't sound as good as I remembered. Then I found that one
of its oscillator banks didn't work. (It has 3 HF-VCO's and 3 complete
TOS / Divider chains.) I found that one of the TOS IC's was blown.
It's an S50241, and I was quite desparately looking for it on the weekend.
Then, after scanning loads of documentation in the archieves of TBS,
I found that I could also use a 50240, the one I got from an old Crumar
Performer many years ago. As I have no datasheet for either I was
saved by finding one strange string synth ("String Melody", maybe
this was a Hohner) which could use either the '41 or rthe '40, according
to its service docs. So I went home, desoldered the '41 and put
a socket and the '40 in, and everything was just fine. What a great
I'd really be interested in the difference of the 50240 and 50241 IC's.
So if anybody knows something about these, please do tell!
Now here's a brief description of the ES-50 "Lambda".
49 Keys, but only 48 working (the 49th would have eaten up another
divider chip (;->) ). Fully polyphonic. Two (!) discrete envelope generators
for each (!) of the 48 keys (hundreds of diodes used as voltage controlled
resistors). 96 voltage controlled Envelope Generators !!
Mixing of different footage rectangles, supposedly to get
staircase-type saw waves. The three oscillator chains are controlled
by a 60 degree / 120 degree / 360 degree LFO to get the basic
string-ensemble chorus sound. You can also manually detune two
of the HF-VCO's, and two LEDs on the front panel nicely show the
beating of the oscillators, caused by detuning and by the complex LFO
modulation.There are formant filters for String and Choir sounds,
and finally the wole thing can be routed thru a BBD chorus.
You can change the chorus speed by a Joystick left to the keyboard.
This "Ensemble Section" I have described so far has also a Brass
and an Organ Preset, but I don't think they are worth that much.
I get this great lush ensemble sound with "Chorus" (=Choir) +
"String I" + "String II"  switched on simultanously. Attack and
Release are switchable from fixed to variable, and unlike the
global envelope on a Solina You get a real AR contour for each
individual note.
In addition, there is a "Percussive" Section which uses the second
set of envelope generators. These are AD-types with a fixed and
switchable Sustain level and Release switchable from short to
Release = Decay. The Presets are E-Piano, Clavi, Piano and
Harmonics. Forget about the names - but E-Piano plus Harmonics
make a nice bell-like sound that fit to the ensemble section very well.
There is a pot for "Key Click", but what it really does is adding a
nice attack sound to the E-Piano preset. The Percussive section
has a nice Tremolo (AM) feature with modulation rate adjustable.
You can route the Percussive and the Ensemble section seperately
or both thru the BBD chorus sections - Yes, it's actually two BBD's,
one for each section, but they re modulated from a common LFO.
The reason for separate signal chains in the chorus is that You
both sections go to VCAs and can be mixed together with an
expression pedal.
Speaking of mixing: There are a (rather effective) tone control
and a master volume slider for each section.
This was my brief description - sorry it was all mixed together,
inside and outside of the beast, hope You enjoyed it anyway.
As I posted before, one of the Lamda's greatest features is its
flat top, so it Dousn't actually take much space as You can stack
anything above it. You shold see my nice keyboard stack:
Kawai Piano, Lambda, MS-20. Ah, and routing the Lambda thru
the MS-20's filters is nice, too.
Besides being a great ensemble machine, the lamda will be the
main basis (sonically and physically (;->) ) for my Vocoder, when it
will be ready.
Oh and I don't know it I will do it, but as each key just switches between
15V and ground (Key contacts go to GND, and there are 4.7k pullups),
It would be very easy to get both, Midi In and Midi Out, with Doepfer