ER-ADSR-555-01

Eurorack ADSR Module

Features

• 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

Credits

• 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

Schematic

• ER-ADSR-555-01 REV1 Schematic

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

• 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

Schematics

• ER-ADSR-555-01 Rev 1 Schematic
• ER-ADSR-555-01 Rev 2 Schematic

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)

Issues

Rev 2 Issues

• 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

Layout

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

• Voltage from R2 into Q2 base looks OK

• Voltage at C1/R6 node

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)

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

• After fix

Rev 2 Changes from Rev 1

• 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

Rev 1 Issues

• 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)

Cuts

• 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)

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

Assembly Sheet

Rev 2

• ER-ADSR-555-01 Rev 2 Interactive BOM
• ER-ADSR-555-01 Rev 2 Assembly Sheet

Rev 1

• ER-ADSR-555-01 Rev 1 Interactive BOM
• ER-ADSR-555-01 Rev 1 Assembly Sheet