From Land Boards Wiki
Jump to navigation Jump to search


ER-ADSR-555-01 FRONT BACK-720px.jpg


  • 3U tall, 6 HP wide Eurorack module
  • Attack-Decay-Sustain-Release ADSR Module
  • Takes in Gate signal, generates CV to VCA
  • Attack, decay, and release pots control speed
    • Attack, decay, and release times can range from 200ms to 16s
  • Sustain pot sets the sustain voltage level
  • LED dims to level
  • 555 Based design


  • Benjie Jiao MiniADSR
    • Original was based on Barry Klein design
    • As built by schmitzbits design - "The Fastest Envelope in the West"
  • Benji's build has a three card stack-up and is 4 HP wide
  • This card is wider but uses 2 cards


Rev 1 Checkout

  • Ordered wrong (earlier) version of the board
    • Missing 1M decay fix resistor
    • Pots are backwards
  • Annotated schematic with Rev 1 reference designators

Adsr3 ann.png

  • Drive IN jack with Erica Synths EDU Sequencer
    • GATE Out output
  • My schematic symbols are Schottky but installed 1N4148 like schmitzbits schemati
    • A, D, R need to be log (Type A) pots
  • All of the pots are backwards (rework below)
    • A, D, S pots should be CCW for no delay
    • S pot should be CW for full output
  • ADR series resistors are 220 Ohms but should be 100 Ohms per schmitzbits note
  • Attack overshoots
  • May need > 100 ohms
  • C3 s/b 1 uF for the pots to have a good range
  • Updated Pl for above
  • Log pot curves


  • Scope capture

ER-ADSR-555 CAP 006.png


Benjie Jiao - DIY Modular Video

Card Test Procedure

  • Drive in GATE in for the following tests
  • Measure output with scope
    • Trigger off Input
  • Set Attack to CCW (min)
  • Set Decay pot to CCW (min)
  • Set Sustain to CW (max)
  • Set Release to CCW (min)
  • Output should be a square wave that matches the input
    • Output level about 0-10V

Test Attack

  • Set Attack to CCW (min)
  • Set Decay pot to CCW (min)
  • Set Sustain to CW (max)
  • Set Release to CCW (min)
  • Adjust Attack
    • Front edge rounds over - scope cap


Test Sustain

  • Set Attack to CCW (min)
  • Set Decay pot to CCW (min)
  • Set Sustain to CW (max)
  • Set Release to CCW (min)
  • Output should be a square wave
  • Adjust Sustain pot
    • Level goes from 0 (CCW) to max (CW)

Test Release

  • Set Attack to CCW (min)
  • Set Decay pot to CCW (min)
  • Set Sustain to CW (max)
  • Set Release to CCW (min)
  • Adjust Release pot
    • Back edge rounds down- scope cap


Test Decay

  • Set Attack to just above CCW (8 0-clock) - just a bit of round over on output
  • Set Decay pot to CCW (min)
  • Set Sustain to just below mid (10-11 o'clock)
  • Set Release to CCW (min)
    • Release pot set to min (CCW)


Rev 3

  • Added R13 resistor (decay noise fix) to card
    • Put 10K on silkscreen - may need to change value if noise is too bad
    • Not installed onto card
  • Changed R4 silkscreen to 1M
  • Built first PCB
  • Works

Rev 2 Issues

  • Silkscreen shows 10K for R4, should be 1M
    • PL updated to 1M
  • Attack works
  • Sustain works
  • Release works
  • Decay has noise issue
    • Adjusting Decay pot near min (CCW) shows noise issue
    • See fix below
    • Decay starts drop but bounces back up


Schematic of front end




Debug Decay Noise

  • Goal - find Decay Noise mitigation strategy
  • Card is sensitive to Eurorack Switching Power Supply noise
    • This issue is also present on Rev 1 cards with noise power supply
      • Issue did not present for prior testing since rack was lightly loaded at the time
  • Tracing noise path (1)-(3) in schematic
    • (1) +12V Vcc noise
    • (2) Q2 is "Off", noise through R5 couples through C5
    • (3) to Q3 to TRIG
  • TRIG (bottom) measured at R7

ER-DELAY-01 R7-Voltage.png

  • Voltage from R2 into Q2 base looks OK

ER-DELAY-01 R2-Q2-Base-Voltage.png

  • Voltage at C1/R6 node

ER-DELAY-01 C1-R6-Base-Voltage.png

Decay Fix

  • Add 3.3K to ground
    • Creates a voltage divider that still lets through the pulse but not enough to turn on Q3
  • Also made C1 a 0.1uF (may not be necessary)

ER-ADSR-555-01 FRONT-END-Decay Fix.png

  • 3.3K Resistor on rear of card
    • Could be installed on top of card into the same holes and vertical

ER-ADSR-555-01 P1090084-720pxV.jpg

  • After fix

ER-DELAY-01 Q3-R6-Base-Voltage-After.png

Rev 2 Changes from Rev 1

ER-ADSR-555-01 Set REV2-720pxV.png

  • Fixed pot ends (swapped ends)
  • Added 1M decay resistor "fix" (dashed lines on Schmitz schematic)
  • Moved up S, R pots to space them up from jacks
    • Updated controls card and front panel
  • Added LEVEL legend to front panel silkscreen
  • Re-sequenced reference designators
  • Change transistor footprints to offset pins/re-oriented
  • Better spacing between parts in upper left of controls card
  • Added power supply bypass caps (1 per power pin)
  • Added URL, Rev 2 marking to rear of card

ER-ADSR-555-01 front-3d Rev1 vs Rev2-720pxV.png

Rev 1 Issues

ER-ADSR-555-01 SET P1080636-720px.jpg

  • Silkscreen has "DELAY" should be "DECAY"
  • A, D, S, R pots ends are all backwards
  • A, D, R pots should be Type A, 1M Ohms (log pots)


  • Perform cuts before installing parts on card
  • Cut at RV1 (pins 2-3) top side


  • Cut at RV2 (pins 2-3) bottom side


  • Cuts at RV3 (pins 1, 3) top side


  • Cuts at RV4 (pins 2-3 and pin 1)

RV4 CUT.PNG top side

Change Pot Series Resistor Values

  • 220 Ohms on A, D, R pots s/b 100 Ohms (PL below is updated already for this)
    • Change R7 to 100 Ohms (A pot)
    • Change R8 to 100 Ohms (D pot)
    • Change R10 to 100 Ohms (R pot)


Add wires

  • Add wires to rear of card
  • Mirrored images below (back side)
  • Add wire RV1-2 to RV1-1 (back side view)


  • Add wire RV2-2 to RV2-1 (back side view)


  • Add wire R9 left side to Sustain pot, RV3-1
  • Add wire U2-7 to Sustain pot, RV3-3


  • Add wire D3-K to RV4-3 (back side view)
  • Add wire RV4-1 to RV4-2 (back side view)


Add Release Resistor

  • Add 1M resistor top side of card


Fix Delay Noise

  • Shows same issues with noisy Eurorack power as the Rev 2 card
  • Add 3.3K resistor

ER-ADSR-555-01 FRONT-END-Rev1 Decay Fix.png


ER-ADSR-555-01 Rev1 P1090101.JPG Delay-Noise-Rework 720pxV.jpg

Assembly Sheet

Rev 3

Rev 2

Rev 1