Ohmforce — Bohm

Manual PDF

Ohmforce Bohm Cheat Sheet

What it is

Bohm is a stereo dual-voice kick system for Eurorack: - Bohm = main kick voice - Groove expander = secondary kick / rumble / tops voice - Performer expander = stereo input, ducking, performance FX

Quick start

Trigger HIT to fire the main kick.
Pick a model with the FUNCTION encoder.
Shape the kick with:
LENGTH = decay/duration
SUSTAIN = body/level
ATTACK = punch
PITCH = base pitch
CURVE = 808-ish CCW → 909-ish CW pitch sweep
TRS DECAY = click length
TRS TONE = click brightness
COLOR = oscillator/timbre behavior
FX = post-effect amount
If installed, clock Groove from CLOCK for rumble/taps.
If installed, use Performer to duck/process external stereo audio.

Core workflow

1) Select a model

Turn FUNCTION to browse kick models.
Press FUNCTION to enter model variations/menu.
In Studio mode, changes are immediate.

2) Main kick behavior

HIT works as trigger or gate
Trigger = normal kick hit
Gate held high = sustain while gate is high, decay when released
PITCH spans roughly C1 (32.7 Hz) to C2 (65.4 Hz)
CURVE
CCW = faster drop to base pitch, more 808-like
CW = slower sweep, more 909-like

3) Groove expander behavior

CLOCK triggers Groove voice independently of HIT
Best use: feed it a regular clock, often 16th notes
2 / 3 / 4 shape tap/envelope levels after each Bohm hit
LENGTH and PITCH are relative to Bohm
center = same as Bohm
left = lower/shorter
right = higher/longer
COLOR blends sound generators:
repetition
kick reverb
noise
grit + sub
TAPS output can emit Groove envelope, or other selectable envelopes in settings

4) Performer expander behavior

Stereo IN is ducked on every HIT
DUCK controls how much input ducks
VOL balances Bohm/Groove against the external input
ON/OFF toggles or gates the Performer FX section
FX can process:
ALL
KICK
INPUT

Best-use tips

For classic techno kick

Start with FM-2X, HZ-1, VX-T, or WT-4
Set:
medium LENGTH
medium/high ATTACK
low-mid PITCH
CURVE slightly CW for 909-ish snap
short TRS DECAY
brighter TRS TONE

For 808-style long kick / bass

Lower PITCH
Increase LENGTH
CURVE more CCW
Raise SUSTAIN
Try BASS FX variation on supported models

For pitch tracking / basslines

Set:
PITCH knob fully CCW
PITCH attenuverter fully CW
system PITCH CV mode to proper 1V/oct window: 0..1V, 1..2V, or 2..3V
Use a 1V/oct sequencer
Use enough LENGTH, or a gate into HIT

For Groove rumbles

Patch steady clock into CLOCK
Raise Groove VOL
Use COLOR toward repetition/reverb area
Use 2/3/4 to build movement
Groove LENGTH only affects repetition generator, mainly from about 3 o’clock to full CW

For sidechain/performance use

Patch stereo music into Performer IN
Use DUCK for pumping
Set Performer FX to DJ FILTER, BEAT ROLL, or SLIP ROLL
Use synced FX switching if you want clean transitions on next HIT

Models at a glance

FM-2X

2-operator FM kick
Great for punchy synthesized kicks
ATTACK strongly affects FM bite
TRS TONE changes modulator waveform character

HZ-1

Wavetable kick + transient synth
Good all-rounder
COLOR adds transient distortion/motion

OLP4

4-operator FM / OPL-style
Most experimental
COLOR inactive
TRS TONE adds FM feedback/noisiness
Groove supported in newer firmware

PM-K1

Physical-model acoustic bass drum
Very different control mapping
Groove not supported
Good for acoustic/organic kick textures

PX3

Wavetable + layered object-hit samples
Harder / more experimental character

SP-6

Digital-sounding wavetable + synthesized transient layers

VX-T

Wavetable + FM transient synth
Nice for click/toc/hihat-flavored transients

WT-4

Analog-ish wavetable + synthesized transient layers

XT-88

User wavetable + user sample model
Loads from microSD:
wavetables/
samples/

Variations / menu essentials

Bohm common variations

FX type

TUBE
BASS
SOFT
HARD
WAVEFOLD
BITCRUSH (some models)
DECIM (some models)

Stereo

STEREO = width 0% to 100%

Groove variations

FX type

LP
HP
BP
DIST

Stereo

STEREO = width 0% to 100%

Performer variations

DUCK TIME = duck release time
DUCK SMTH = duck curve smoothing
DUCK BS = band-split frequency for more transparent ducking
FX types:
DJ FILTER
HP
LP
BEAT ROLL
SLIP ROLL
DJ RESO = filter resonance
CHN = ALL, KICK, INPUT

Running modes

Studio mode

Default on power-up
Immediate editing
Best for sound design and browsing models

Live Song mode

Programs act as step sequences of kick snapshots
Trigger FUNCTION to advance to next step
New step becomes active on next HIT

Live Jam mode

Programs act as banks of kick snapshots
Turn FUNCTION to choose next kick
Press FUNCTION to cue it
It becomes active on next HIT

Snapshot basics

Save a snapshot by holding HIT and pressing FUNCTION
Snapshots store:
model variations
knob positions
LOAD
loads variations only
LOAD W/ POTS
loads variations + pot positions

System settings worth knowing

PITCH CV: select 1V/oct mapping window (0..1V, 1..2V, 2..3V)
ATTVERT 2: map SUSTAIN attenuverter to SUSTAIN CV or VELOCITY CV
FUNC RAND: randomize Bohm+Groove or all including Performer
PERF FX: FX switch INSTANT or SYNCED
PERF ON/OFF: TRIG or GATE
GRV ENV: FALL or SUSTAIN
TAPS OUT: GROOVE, I BOHM, PERF, BOHM
PANNING: hard-pan Bohm/Groove/Performer left, center, or right
POST EQ: output EQ for Bohm/Groove
IN VOL: attenuate Performer input
PERF VOL: Performer slider controls B+G or BOHM
PERF MAX: max Performer-controlled output level
LOCK MODEL: prevent accidental model changes in Studio mode
BACKUP / RESTORE via SD card
FACTORY RESET

I/O and control reference

Global technical CV/audio specs

CV input range: ±5V
0..5V compatible: yes
Knob/CV resolution: 16-bit
Audio output: stereo
Sample rate: 48 kHz
Latency: 0.33 ms

Bohm main module

Jacks

Jack	Type	Range	Function
`LENGTH CV`	CV in	±5V	Modulates kick duration
`ATTACK CV`	CV in	±5V	Modulates attack amount
`SUSTAIN CV`	CV in	±5V	Modulates sustain/volume
`HIT`	gate/trigger in	0..5V compatible / CV input spec ±5V	Triggers or sustains the kick
`TRS DECAY CV`	CV in	±5V	Modulates transient decay
`TONE CV`	CV in	±5V	Modulates transient tone
`FUNCTION CV`	CV in	±5V	In Studio: randomize current variations; other contexts depend on mode
`VELOCITY CV`	CV in	±5V	Modulates kick velocity/level
`PITCH CV`	CV in	±5V	Pitch modulation; can be configured for 1V/oct over selected 1V window
`CURVE CV`	CV in	±5V	Modulates pitch curve
`COLOR CV`	CV in	±5V	Modulates timbre/wavetable behavior
`FX CV`	CV in	±5V	Modulates FX amount
`OUT L/R`	stereo audio out	Eurorack audio	Main stereo output

Knobs / controls

Control	Type	Function
`LENGTH`	knob	Kick duration
`SUSTAIN`	knob	Kick body/level
`ATTACK`	knob	Attack/punch
`PITCH`	knob	Base kick pitch
`CURVE`	knob	Pitch drop shape: 808-like CCW → 909-like CW
`TRS DECAY`	knob	Click/transient duration
`COLOR`	knob	Timbre / wavetable behavior
`FX`	knob	Kick post-effect amount
`TRS TONE`	knob	Click brightness
`FUNCTION`	push encoder	Model select, menu navigation, variation editing
`HIT`	button	Manual trigger; can also be held
`microSD slot`	storage	Firmware, models, user wavetables/samples

Attenuverters / trims

Control	Type	Function
`LENGTH` attenuverter	trim	CV depth/polarity for LENGTH CV
`ATTACK` attenuverter	trim	CV depth/polarity for ATTACK CV
`SUSTAIN` attenuverter	trim	CV depth/polarity for SUSTAIN CV or VELOCITY CV depending on setting
`PITCH` attenuverter	trim	CV depth/polarity for PITCH CV
`CURVE` attenuverter	trim	CV depth/polarity for CURVE CV
`COLOR` attenuverter	trim	CV depth/polarity for COLOR CV

Groove expander

Jacks

Jack	Type	Range	Function
`FX CV`	CV in	±5V	Modulates Groove FX
`CLOCK`	trigger in	0..5V compatible / CV input spec ±5V	Triggers Groove voice/taps
`COLOR CV`	CV in	±5V	Modulates sound source blend
`VOL CV`	CV in	±5V	Modulates Groove volume
`LENGTH CV`	CV in	±5V	Modulates Groove duration (repetition source only where applicable)
`PITCH CV`	CV in	±5V	Modulates Groove pitch relative to Bohm
`TAPS CV`	CV in	±5V	Shapes tap envelope
`TAPS CV OUT`	CV out	not explicitly stated; Eurorack CV	Outputs selected envelope (`GROOVE`, `I BOHM`, `PERF`, or `BOHM`)

Knobs / sliders

Control	Type	Function
`2`	knob	2nd tap/envelope level
`3`	knob	3rd tap/envelope level
`4`	knob	4th tap/envelope level
`LENGTH`	knob	Groove length relative to Bohm
`PITCH`	knob	Groove pitch relative to Bohm
`FX`	knob	Groove post-effect amount
`COLOR`	knob	Selects/blends sound generators
`VOL`	slider	Groove output level

Attenuverters / trims

Control	Type	Function
`FX` attenuverter	trim	CV depth/polarity for FX CV
`COLOR` attenuverter	trim	CV depth/polarity for COLOR CV

Performer expander

Jacks

Jack	Type	Range	Function
`DUCK CV`	CV in	±5V	Modulates ducking amount
`FX CV`	CV in	±5V	Modulates Performer FX parameter
`ON/OFF CV`	gate/trigger in	0..5V compatible / CV input spec ±5V	Toggles or gates FX depending on system setting
`IN L/R`	stereo audio in	Eurorack audio	External stereo input
`VOL CV`	CV in	±5V	Controls Bohm/Groove or Bohm-only level depending on setting

Knobs / buttons / sliders

Control	Type	Function
`DUCK`	knob	Amount of ducking on external input
`FX`	knob	Performance FX parameter
`ON/OFF`	button	Activate/deactivate or gate the FX section
`VOL`	slider	Level of Bohm/Groove before mix/effect, depending on settings

Installation / power / size

Width

Bohm: 18HP
Groove: 10HP
Performer: 8HP
Full set: 36HP

Depth

Bohm: 28 mm
Groove: 26 mm
Performer: 26 mm

Power

Bohm: +12V 130 mA / -12V 10 mA
Groove: +12V 20 mA / -12V 10 mA
Performer: +12V 10 mA / -12V 5 mA
+5V: unused

microSD / firmware / user files

microSD / SDHC Class 10+
Up to 32 GB
FAT32 with MBR only
Used for:
firmware updates
model files
XT-88 user wavetables and samples
backup/restore

XT-88 user file formats

Wavetables

.wav
Serum/Serum 2 compatible, assumed 2048-cycle
or mono 32-bit float, assumed 1024-cycle
max 16 wavetables or until 1.4 MB memory full

Samples

.wav
mono or stereo
16-bit / 24-bit integer or 32-bit float
48 kHz
max 256 samples or until 14 MB memory full

Practical patch recipes

Simple standalone kick

Trigger sequencer → HIT
Bohm OUT → mixer
Start with FM-2X
Tune with PITCH, CURVE, LENGTH, ATTACK

Techno rumble

Main trigger → HIT
16th clock → Groove CLOCK
Groove VOL up
Groove COLOR toward repetitions/reverb
Adjust 2/3/4 and Groove FX

Sidechain external synths

External stereo synth → Performer IN
Kick trigger → HIT
Increase Performer DUCK
Output from Bohm OUT

Envelope utility patch

Use Groove TAPS OUT to modulate another VCA/filter
In settings, choose source:
Groove envelope
inverted Bohm envelope
Bohm envelope
Performer duck envelope

Gotchas

Groove does nothing without CLOCK
Groove LENGTH only affects repetition source
PM-K1 does not support Groove
For pitch tracking, ensure sequencer is 1V/oct
The module can preload next live snapshot, so ultra-fast step changes may be limited by model load time
If you add Groove/Performer after purchase, calibration is recommended

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