Pittsburgh Modular — Synthesizer Box

Manual PDF

Pittsburgh Modular Synthesizer Box — Cheat Sheet

Type: Semi-modular analog monophonic voice
Status: Discontinued
Format: Eurorack, 28hp, 36.5mm deep
Power: +12V 125mA / -12V 95mA / +5V not required

What it is

A complete analog synth voice with these internally patched sections:

1V/O IN → Glide → Waveforms Oscillator → LPG → VCA OUT
Control/mod defaults: - LFO TRI → Oscillator FM CV - LFO TRI → Oscillator MOD CV - ENV OUT → LPG CV - ENV OUT → VCA CV

Patching into the destination input breaks/overrides the internal routing.

Quick Start

Basic monosynth patch

Patch pitch CV to 1V/O IN
Patch gate/trigger to ENV IN
Take audio from VCA OUT
Set:
Oscillator coarse/fine tune to taste
Mixer waveform levels up
LPG mode to LPG or VCA
Envelope attack low, decay/release to taste
VCA CV attenuator up

Fast percussive patch

ENV IN with triggers/gates
Use LPG mode = LPG
Set Mod/Ping = PING
Short envelope, moderate LPG frequency
Audio from VCA OUT or LPG OUT

Drone patch

Use oscillator outputs or MIX OUT
Patch directly to LPG IN or VCA IN
Skip envelope, open VCA manually with its level knob
Add LFO to FM CV IN or MOD CV IN

Signal Flow Overview

Oscillator / Waveforms

Main sound source with: - Triangle - Saw or Blade - Square - Sub oscillator one octave below

The mixer sets the levels of triangle, saw/blade, and square into: - their respective post-mixer outs - MIX OUT

LPG

A 3-mode dynamics/tone section: - VCA - LPG - Lowpass filter

Envelope

ADSR envelope with ENV IN gate/trigger input and ENV OUT

LFO

Triangle and square LFO, with low/high range switch. Can also run fast enough for audio-rate FM.

Glide

Always between 1V/O IN and oscillator pitch path.

VCA

Final linear VCA after LPG by default.

Controls Reference

Waveforms Oscillator Controls

Frequency — coarse tune
Fine Tune — fine pitch adjust
Sub toggle — sub oscillator level:
low volume / off / full volume
FM CV knob — attenuates oscillator FM amount
Expo FM / Linear FM toggle — selects FM response
Saw / Blade toggle — chooses saw type sent to mixer/output
Saw = core saw, not affected by MOD CV
Blade = complex saw, affected by MOD CV and BLADE IN
MOD CV knob — attenuates waveform modulation amount

LPG Controls

MOD CV knob — attenuates LPG frequency modulation amount
Mod / Ping toggle
MOD = CV sweeps LPG/filter
PING = incoming CV is converted to a short strike
Frequency — cutoff / pass level depending on mode
Resonance — active in lowpass mode only
Mode toggle
Up: VCA
Center: LPG
Down: Lowpass

LFO Controls

Rate — LFO speed
Range toggle — low/high range

Envelope Controls

Attack
Decay
Sustain control/switch as labeled on panel/manual
Release

Glide Controls

Time — portamento amount

Mixer Controls

Triangle Wave — level to TRI OUT and MIX OUT
Saw/Blade Wave — level to S/B OUT and MIX OUT
Square Wave — level to SQR OUT and MIX OUT

VCA Controls

CV Input Attenuator / Output Level — VCA level / CV amount

Jack Reference

Important: The manual page provided does not specify numeric voltage ranges for any CV or audio input/output jacks.
Therefore, exact voltage ranges are undocumented in the manual.

Inputs

Jack	Type	Function	Internal Normal
1V/O IN	CV in	1V/oct pitch input to oscillator via glide	—
BLADE IN	CV/audio in	Manipulates Blade waveform	—
FM CV IN	CV in	External oscillator FM input; overrides internal FM routing	LFO TRI
MOD CV IN	CV in	External waveform modulation input; overrides internal modulation routing	LFO TRI
LPG CV IN	CV in	External LPG modulation input; overrides internal LPG CV routing	ENV OUT
LPG IN	Audio in	External signal into LPG; overrides internal audio routing	Oscillator MIX OUT/internal voice path
ENV IN	Gate/trigger in	Triggers envelope generator	—
VCA CV IN	CV in	External VCA CV; overrides internal VCA CV routing	ENV OUT
VCA IN	Audio in	External signal into VCA; overrides internal audio routing	LPG OUT

Outputs

Jack	Type	Function	Voltage Range
TRI OUT	Audio out	Post-mixer triangle output	Not specified in manual
S/B OUT	Audio out	Post-mixer saw or blade output	Not specified in manual
SQR OUT	Audio out	Post-mixer square output	Not specified in manual
MIX OUT	Audio out	Mixed oscillator output incl. triangle, saw/blade, square, sub	Not specified in manual
LFO TRI OUT	CV out	Triangle LFO output	Not specified in manual
LFO SQR OUT	CV out	Square LFO output	Not specified in manual
ENV OUT	CV out	ADSR envelope output	Not specified in manual
LPG OUT	Audio out	LPG output	Not specified in manual
VCA OUT	Audio out	Final VCA output	Not specified in manual

Section-by-Section Usage Notes

1) Waveforms Oscillator

The oscillator is the core voice.
Saw gives a stable classic waveform.
Blade gives a more animated/complex wave; best for timbral motion.
MOD CV affects:
Square via pulse-width modulation
Blade via waveshape morphing
BLADE IN adds further Blade-specific shaping.
The sub oscillator thickens bass and adds weight.

Good uses

Classic lead/bass: Saw + sub
Hollow/animated: Square with MOD CV
Aggressive/modern: Blade with LFO or envelope to MOD CV

2) LPG

Three different personalities:

VCA mode

Pure amplitude control
Best when you want clean level shaping

LPG mode

Characterful combo of filtering + amplitude behavior
Louder sounds get brighter, quieter sounds mellow naturally
Great for plucks, bongs, wood-like hits, organic decays

Lowpass mode

Traditional lowpass filtering
Resonance active here only

Ping mode

Use Mod/Ping = PING and send triggers/CV to LPG CV IN for struck/percussive sounds.

3) LFO

Low range: slow sweeps
High range: fast modulation and audio-rate FM territory
Triangle is useful for smooth pitch/timbre motion
Square is useful for stepped/trill/gate-like modulation

Typical destinations: - FM CV IN for vibrato to harsh FM - MOD CV IN for PWM / Blade movement - LPG CV IN for rhythmic tone shaping - VCA CV IN for tremolo

4) Envelope

Use ENV IN from gate or trigger source.

Typical uses: - Default: - controls LPG - controls VCA - Patch ENV OUT to MOD CV IN for timbral attack - Patch ENV OUT to FM CV IN for pitch envelopes

Envelope behavior notes

The manual describes standard ADSR behavior, though the Decay description appears unusual in wording. In practical use, treat it as the voice contour source for amplitude, LPG strike, or modulation.

5) Glide

Adds portamento to incoming 1V/oct pitch CV
Always sits between 1V/O IN and oscillator
Best for legato leads, acid slides, and smooth interval transitions

6) Mixer

The waveform mixer controls how much of each waveform hits: - its own dedicated output - the MIX OUT

The sub oscillator is included in MIX OUT per the manual.

Good starting mixes

Bass: Saw/Blade + sub, a little square
Lead: Saw/Blade + triangle
Rounded tone: Triangle dominant
Richer PWM lead: Square + moderate MOD CV

7) VCA

Linear VCA
Normally receives:
audio from LPG OUT
CV from ENV OUT
Final output is VCA OUT

Use it as: - the normal end of the voice - a standalone VCA for external audio/CV by patching VCA IN

Internal Normalizations Summary

Destination	Normal Source
Oscillator FM	LFO TRI OUT
Oscillator MOD CV	LFO TRI OUT
LPG CV	ENV OUT
VCA CV	ENV OUT
VCA audio in	LPG OUT
Oscillator pitch	1V/O IN through Glide

Practical Patch Ideas

Simple bass

1V/O IN from sequencer
ENV IN from gate
Mixer: Saw + Sub
LPG mode: LPG
Short attack, medium decay, low sustain, medium release
Audio: VCA OUT

West-coast style pluck

Mixer: Triangle + Blade
LPG mode: LPG
Mod/Ping = PING
Trigger LPG CV IN
Optional slow LFO to BLADE IN
Audio from LPG OUT or VCA OUT

PWM lead

Square wave up in mixer
LFO TRI to MOD CV IN
Light glide
Envelope to VCA as normal
Output from VCA OUT

Audio-rate FM texture

Set LFO to high range
LFO TRI to FM CV IN
Choose Linear FM for cleaner FM behavior
Start with low FM amount

Filtered external audio

Patch external audio to LPG IN
Use LPG in LOPASS mode
Envelope or LFO to LPG CV IN
Take output from LPG OUT or route onward to VCA IN

Tips

If a section seems unresponsive, check whether inserting a cable has broken its normalled source.
Use LPG mode when you want the module’s most characteristic sound.
Use VCA mode when you want predictable amplitude shaping.
Blade + MOD CV is the fastest route to unusual animated timbres.
High-range LFO can act as an extra audio-rate modulation source.

Known Documentation Gaps

The supplied manual text does not provide explicit voltage ranges for: - CV inputs - audio inputs - CV outputs - audio outputs - gate/trigger thresholds

So all jack voltage ranges remain undocumented in the manual.

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