NOVAMOD (accent problems)

[Philip]

matt wilson wrote:
> 
> (so much for bragging last night...oh well)
> 
> i can't get the accent button to work at all on phil pilgrims novamod.
> if you read last nights jubilant posting, you know everything else
> works.
> i noticed that phil's diagramming is slightly different than his written

HI Matt, 

Yep I made a mistake. I will correct it in the upcoming new
instruction.  In the mean time, I'll describe the circuit so you can
figure it out.



The op amp's feedback loop through R140 is now routed through R140 AND
the rotary pot (which is inserted in series with R140). The normally
closed switch is in parallel with the pot thus bypassing it. Upon
opening the switch, the feed back resistance increases (becoming  R140
plus the resistance of the rotary pot) thus an increase in gain
(volume). To control amount of gain, the center tap of the pot is
soldered to the cw lead on the pot.


                                  NC switch
                                    |  
                               ____ | _____
                              |   __|__    |
                              |            |
                              |      ______|
                              |     V      |
     ___ /\/\/\/\_____________|__/\/\/\/\__| 
    |      R140                ccw POT  cw |
    |                                      |
    |                                      |
    |                                      |
    |                                      |
    |                                      |



This is a very "dirty" way to add accent but the typical CV increase to
VCA was too difficult to implement on the 101. Surprisingly this method
does not seem to add noticable noise!!! :)

The latest NovaMod variation features a 1/4" jack connected to the coil
of a TTL triggered relay. This relay's NC connection is in series with
the NC switch. It is fun because the NovaMod now clicks inside...kinda
like a "thumper" on a Chroma!  A possible addition to the next batch of
NovaMod kits is a solid state relay with zerocross switching to reduce
clicking (but they cost $17 each!). The latest NovaMod variation also
has the same 1/4" and relay circuit but it is connected to the
portamento switch for external control of portamento off/on. This allows
for easy midi to cv control of:

Note CV
Note Gate
Accent
Slide (portamento)
VCF cutoff CV
LFO Clock

With the "way-cool" FM of VCF,  killer "better than 303" sweeps, accents
and slides can now be realized on the 101.

 
> instructions on this particular mod (regarding which lug on the rotary
> pot is connected to the center lug: the diagram says its the CW lug,
> whilst
> the instructions say its the CCW lug: neither worked for me).
> if anyone encountered this problem (the only one out of the bunch)
> please contact this now humble novamodder.
> 
> also: i didn't do the AR mod. is it difficult?

No but test it before installing. Two 9V batteries in series will give
+9, gnd and -9V.  Connect these to the AR board's +V GND and -V. Touch
the GATE IN wire to the +9V to simulate a key gate signal (key press)
then watch the AR OUT signal rise and fall (rate depends on the A and R
pots of course) It is best to observe using a scope with a 1 sec sweep
or use a voltmeter (analogue needle type is best)

Philip
 
Matt Please copy this to AH (I'm not subscribed thus I can't post) :(


Finally  I will hopefully have more kits for sale before Christmas...ho
ho ho


-- 
Philip Pilgrim                  The Lab Audio Works
5 Evan's Drive                  - Analog/Digital Recording/Processing
Hammonds Plains                 - Computer/Synth Interfacing
Nova Scotia, Canada             - Hardware/Software Development
B4B 1M8

Phone     +1.902.835.7844
Email      mailto:thelab at sprint.ca

Web Page: http://www.robotnik.com/the_lab