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Null-A
is an all-in-one analogue synth packed into 42HP.
2
It features:
2 VCOs
1 state variable VCF
1 ladder VCF
1 VC Delay
It does not feature MIDI, micro-processors or any software.
There are several presets that run between the switches of the jacks. If you
insert a patch-cable into either jack the preset is disconnected.
a) VCO1 pulse out > state variable VCF input
b) VCO2 pulse out > ladder VCF input
c) state variable VCF LP output > VCA1 input
d) ladder VCF output > VCA2 input
e) VCA1 output > mixer
f) VCA2 output > mixer
g) Mixer output > headphone amp
h) ADSR output > VCA1 CV input
i) Clock divider /8 output > ADSR gate input
j) LFO 1 square output > S&H clock input
k) LFO2 triangle output & Sloth chaos output & sequencer CV output > S&H
sample input
l) LFO2 square output > Clock divider input
m) LFO2 square output > Sequencer clock input
Preset patches a, b, c, d, h, i, l, m from the above list
nonlinearcircuits
NULL-A
Build & BOM
2
3 VCAs
2 LFOs
Mixer
Headphone amp
Sequencer
Clock Divider
Sample & Hold (S&H)
Sloth chaos generator

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Summary of Contents for Nonlinearcircuits Null-A2

  • Page 1 NULL-A Build & BOM Null-A is an all-in-one analogue synth packed into 42HP. It features: 2 VCOs 3 VCAs Sequencer 1 state variable VCF 2 LFOs Clock Divider 1 ladder VCF Mixer Sample & Hold (S&H) 1 VC Delay...
  • Page 2 Most of these are simply to save a few patch-cables. The interesting one is the signals from the Sequencer, Sloth chaos and Tri from LFO2 are mixed and fed to the S&H sample input. This means it is continually generating stepped and smooth CVs (for there is a Slew pot) that are different but related to everything else that is going on.
  • Page 3 PART VALUE COMMENTS NUMBER 100p 100p 220nF 100n 100n 100n 100n 470p 100n 100n not on vers 2 100n 100n 100n 100k 100n 100k or thru-hole 220R 100k 100k 100k 100k 100k 100k 100k 100k...
  • Page 4 100k 470K or thru-hole 470k 330R 220R 100k 100k 100k 180k 180k 100k R100 470R 100k R101 470R 150k R102 220k 100k R103 100k R104 100k R105 100k R106 100k 470k R107 330k R108 200k R109 100k R110 R111 47k* R112 10k* R113...
  • Page 5 R138 R193 R139 100k R194 optional, see R140 R195 notes R141 R196 R142 R197 100k R143 R198 100k R144 470R ADSR LED R199 R145 470R R200 R146 220k R201 R147 R202 330R R148 R203 100k R149 R204 R150 R205 330R R151 R206 R152...
  • Page 6 R247 100k Trimpot 1k SOT23-6 AKA R248 100k SOT-457 R249 Q13, Mouser Part No: R250 BCM847 771-BCM847DS115 R251 SOT23 Q1, Q3, There is no Q25 R252 Q5, Q7, on vers 2. R253 R254 Q10, R255 Q14, R256 100k Q15, Q16, R257 100k Q18,...
  • Page 7 COMPONENT QUANTITY COMMENTS 2 pin bipolar LED 100k pot 1MA pot MONO jacks Kobiconn type STEREO jack Kobiconn type Eurocrack power connector single vactrol anything okay, even DIY 10 Pin 2.54mm Single Row Tayda: A-1306 Female Pin Header 40 Pin 2.54mm Single Row at least 4 cut into 10 pin lengths Pin Header Strip...
  • Page 9 Small mod required for R148:...
  • Page 10 Set-Up VCOs: The 100k trimpots on the VCOs are used to set up the panel pots so they have minimal dead zones at the start and ends of their travel. The 20k trimpots are used to dial in 1V/oct tuning; you should be able to get 3 octaves of decent tracking from these VCOs.
  • Page 11 Board close-ups Top right...
  • Page 12 Bottom right...
  • Page 13 Top middle...
  • Page 14 bottom middle...
  • Page 15 Top left...
  • Page 16 Bottom left...
  • Page 17 SCHEMATICS...