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4ms Company WAV Recorder User Manual

Made by: 4ms Company
Type: User Manual
Category: Recording Equipment
Pages: 15
Size: 0.48 MB

 

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WAV Recorder

4ms Company

User Manual 1.0.1 – June 27, 2018 

for f

irmware v1.0  

The 

WAV Recorder

 from 4ms Company is a high fidelity, two-channel stereo audio recorder with basic playback 

features. Accepting a wide range of input signals, from line-level to modular-level, the 

WAV Recorder

 stores 

audio onto a microSD card in lossless .wav format up to 96kHz/24-bit. The trigger jack can be used for capturing 
rhythmic loops or synchronizing multiple 

WAV Recorder

 modules for multi-track recording. In 

Playback

 mode, 

the trigger jack or button plays the most recent recording. A simple file/folder navigation system can be used to 
browse the folders on the card for playing back .wav files. A 

Gain

 knob allows for up to +20dB of boost, and an 

LED Signal Meter indicates clipping and the signal level. 

• Records up to 96kHz/24-bit, creating stereo or mono .wav files on the microSD card 
• Gain knob and LED level meter make it easy to record a wide range of signal levels 
• Plays standard .wav files from the card, without renaming files 
• Browse any folder on the card for playback 
• Card can be hot-swapped without rebooting module 
• Extremely low noise, high-fidelity design 
• Includes 16GB microSD card (Class 10), SD adaptor, 10-to-16 pin power cable and M3 screws 
• Can be used as a stereo pre-amp (line to modular level), providing up to +20dB of gain 

Record

WAV RECORDER

Left

Right

IN

OUT

Clip

Input Gain

Busy

Playback

Record

0dB

-

+20dB

 


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Table of Contents 

Setting up your WAV Recorder 

1. Power your Eurorack modular case off and find 6HP of available space.

2. Connect the free end of the power cable to a 16-pin Eurorack power header on 

your power supply distribution system, with the red stripe towards to the -12V. 

The other end of the power cable is a 10-pin connector which should already be 

connected to the WAV Recorder with the red stripe on the power cable orientated 
towards the bottom of the module. 

Note: The WAV Recorder is reverse-polarity 

protected, but other modules being incorrectly connected could damage 

anything on the power bus. 

3. Using the included Knurlie screws, securely fasten the WAV Recorder to the rails 

of your case. 

4. Power the system on.
5. Begin with 

Tutorial: Basic Recording on page 4 of this manual.


Setting up your WAV Recorder

2

..............................................................................

Controls: Button, Knob, Switch and Jacks

3

............................................................

Tutorial: Basic Recording

4

.......................................................................................

Folders and File Organization

5

................................................................................

Playback

5

................................................................................................................

Browsing Files for Playback

6

...................................................................................

Trigger Jack

7

...........................................................................................................

Pausing Recording

7

.................................................................................................

Example Patch: Multi-track Recording

8

..................................................................

Using the WAV Recorder as a Pre-amp

9

.................................................................

Busy Light

9

..............................................................................................................

Checking for Free Space

9

.......................................................................................

Hot Swapping the microSD Card

10

........................................................................

LED Signal Meter and Clipping

10

............................................................................

Recording For Long Periods

10

................................................................................

System Mode

11

.......................................................................................................

Recording Rates and Selecting microSD Cards

12

..................................................

Checking the Firmware Version

13

...........................................................................

Updating Firmware (Audio Bootloader)

13

...............................................................

microSD Card

14

......................................................................................................

Electrical and Mechanical Specifications

15

............................................................

Jumpers

15

...............................................................................................................

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15

Important! 

Never remove the microSD card when the 
Busy
 light is on. This could corrupt the files on 
the card. 

If you remove the Wav Recorder from your 

case, always store and transport it in the 

included anti-static bag. 

 


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Controls: Button, Knob, Switch and Jacks 

Record/Playback switch 
The 

WAV Recorder

 has two main functions: recording and playing .wav files. This switch 

toggles between these functions. 
Flip the switch up to enter 

Record 

mode. Flip the switch down to enter 

Playback

 mode. 

Button 
In 

Record

 mode, press the button once to start recording a new .wav file onto the card. Press 

it again to stop recording. The button will turn red while recording. 
In 

Play

 mode, press the button once to play the currently selected .wav file from the card. 

Press it again to stop playing. The button will turn green while playing. 
 
Audio IN jacks 
Patch the audio signal you want to record into the 

IN

 jacks. The jacks are normalized so that 

if you patch a mono signal into the 

Left IN

 jack and have nothing plugged into the 

Right IN

 

jack, the signal will be routed to both channels. To record a stereo signal, patch into both 

Left 

IN 

and 

Right IN 

jacks. These jacks accept a wide range of signal levels, from line level up to 

modular level. 

Audio OUT jacks 
The 

Audio OUT

 jacks can be used for monitoring the signal while recording and for listening 

to playback of .wav files. The 

Left OUT

 jack outputs the left channel, and the 

Right OUT

 

jack outputs the right channel. The Signal Meter shows the level of the signal present on 

these jacks. 

Signal Meter 
These eight lights will show the level of the signal being output on the 

OUT

 jacks. If you are 

recording, this is equivalent to the signal being recorded. The left column represents the left 

audio channel, and the right column represents the right audio channel. More lights turned on 

means there’s a louder signal. The top red lights indicate clipping. If the Signal Meter shows 
that your signal is either too loud (clipping) or too quiet, you can use the the 

Gain

 knob to 

adjust the level. 

Gain knob 
The volume (level) of the signal being recorded or played can be adjusted using this knob. 
Turning the 

Gain

 knob up will make the output louder, while turning it down will make the 

signal quieter. When the knob is turned all the way to the left, the signal is muted. When the 

knob is pointed directly up, the signal is neither boosted nor cut. When the knob is turned all 

the way up, +20dB of gain is applied (which is enough to boost a line level signal to a 

modular level signal). 

Record Trigger jack 
This jack accepts a trigger. In 

Record

 mode, a trigger signal will toggle recording. In 

Play 

mode, a trigger will make playback start or re-start. The 

Record Trigger 

jack allows you to 

connect and synchronize your 

WAV Recorder

 with a clock, other 

WAV Recorders

 or other 

modules. It also allows you to remotely control recording and playback. 

SD Card slot and Busy Light 
The 

WAV Recorder

 records and plays back from a microSD card inserted into the card slot. 

Insert the end of the card with the shiny pins facing to the left. 
The 

Busy

 light will turn on whenever the card is being read or written. 

NEVER REMOVE THE SD CARD OR POWER OFF WHEN THE BUSY LIGHT IS ON! 

Always wait until the light is off. The light will turn off after you stop recording or playing. 

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Playback

Record

Left

Right

IN

OUT

Clip

Input Gain

0dB

-

+20dB

Record

Busy

 


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Tutorial: Basic Recording 

Recording on the WAV Recorder is easy! 

1. Find something you want to record. It can be audio from your modular, another synth or musical 

instrument, your phone or computer, or anything that outputs a line-level, headphone-level, or 

modular-level signal.

2. Patch the audio signal into the Left IN jack. If you have a 

stereo signal, you can patch the right channel into the 
Right IN jack.

3. Patch the OUT jacks to something that lets you hear the 

audio (speakers, amp, or a mixer).

4. The lights on the Signal Meter should be responding to the signal you patched in. Turn the Gain 

knob so that some lights turn on, but not so high up that the red lights turn on. You should also 

hear the audio output change volume as you turn the Gain knob.

5. Make sure the switch is flipped to Record and press the button. The button will turn red, and the 

Busy light will start to flash.

6. Record as much as you want and then press the button again. Wait for the Busy light to turn off.

7. Congratulations! You just made a high-quality recording!

The WAV Recorder has now created a .wav file on the microSD card. You can listen to your recording 

by flipping the switch to Playback and then pressing the button. The button will turn green and you’ll 

hear your recording. You can press the button again to stop playback.

You also can listen to the recording on your computer. Wait until the Busy light has turned off and then 
pull out the microSD card. Insert it into your computer or card reader and browse the WAV Recorder 

folders for the folder and file with the highest number. See the Folders and File Organization section for 

more details.

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15

Tip: Use an adaptor cable to convert to 

1/8” (3.5mm) if necessary. You can 
patch  a  stereo  cable  into  the 

IN

 

jacks, but the right channel will be 
ignored.

 


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Folders and File Organization 

Every time you power on the WAV Recorder, a new session is started. All of the recordings you make 

in each session are saved in the same session folder. Session folders are named like this:
WAV Recorder - 0001
WAV Recorder - 0002

The most recent session folder will always be the highest 

numbered folder. 

Inside each folder are your recordings, named in numerical 

order:
001 - recording.wav
002 - recording.wav

Once it reaches 

999 - recording.wav, it’ll automatically 

create a new session folder and start over at 

001. 

The most recent recording will always be the highest 

numbered file in the highest numbered folder. 

If the system gets powered down unexpectedly while recording 
(and luckily it happens while the Busy light is off), you might find 
your recording in the 

_tmp folder.

Note: This naming system is what the WAV Recorder uses when 

you make a new recording. In Playback mode, any file with any name can be accessed. You do not 

need to rename your files to play them. 

Playback 

Playing .wav files with the WAV Recorder is easy. 

Flip the switch to Playback and press the button. The most recent recording will play. The button will 

turn green while a recording is playing. Turn the Gain knob to adjust the playback volume. You can 

press the button again to stop playback, or it will stop by itself when the .wav file has finished playing.

If you haven’t recorded anything yet this session, but you’ve made previous recordings, the the WAV 
Recorder
 will play the most recent recording it finds (the highest numbered file in the highest 

numbered session folder on the microSD card). See 

Folders and File Organization for an explanation 

of the naming system. If no session folders are found, the WAV Recorder will pick the first .wav file in 

the first folder on the microSD Card, alphabetically.

You’re not stuck with only playing the most recent recording! Use the browsing feature to choose a 

different file in a different folder. See the next section for details.

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Browsing Files for Playback 

When you first flip the switch to Playback, the most recent recording in the most 

recent session folder will be selected as the current playback file. If there are no 

session folders on the card, then the folders will be scanned alphabetically and the 

first file in the first folder will be selected.

Hold down the button while turning the knob to browse the folder of the currently 

selected file. As soon as you start turning the knob with the button down, the lights 

will show you how many files are in the folder. Any light that’s turned on represents 

a file in the folder. For example, if six lights are on, then there are six files in the 

selected folder. The files are in alphabetical/numerical order.

The light corresponding to the currently selected file will be brighter than the others. As you turn the 

knob( while still holding the button down), the bright light will move through all the available files. See 

diagram below.

If you want to hear the new file that you've 

selected, you can play it like you would play any 

other file: just tap the button or fire a trigger into 

the jack. If you’re playing a long file, you can 

continue to browse while the file is playing without 

interrupting it. As long as you are holding the 

button down while turning the knob, the playback 

volume won’t change.

Folders with lots of files 

If there are more than eight files in a folder, then 

the files will be split up into “pages” of eight files 

each. The first and/or last light will flicker a bit to 

indicate there’s another “page” of files before or after it. The 

number of flickers indicates the next or previous “page” 

number (i.e, one flicker means you can access the 1st page 

by turning past that light, two flickers means the 2nd page 

is past that light, etc…) Turn the knob to the first or last 

light, and then keep turning it a little bit more to jump to the 

next or previous page. The light will jump from the first to 

last position, or vice-versa, when you change pages.

Browsing to a new folder

If you want to select a file in a different folder, 

press and hold the button while turning the knob 

just like you do for file selection. Turn the knob all 

the way up (to access the next folder) or all the 

way down (to access the previous folder), and 

leave it there for about two seconds (while still 

holding the button down). The four lights on the 

left or right column will flash rapidly to tell you that 

you’re about to go to the previous or next folder, 

respectively. Release the button when you see the 

flashing, and you will jump to the next or previous 

folder. The folders are browsed alphabetically/

numerically.

If you see the column lights flashing, but don’t 

want to change folders, turn the knob up or down to cancel the action.

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15

…and turn

Playback

Record

Hold…

Clip

Current 

File 

Other 

Browsing a folder containing 6 files:

Tip: If  you  can’t  quite  reach  the  top  or 

bottom file, just let go of the button, 
turn  the  knob  to  a  new  position, 
and  then  resume  the  button+knob 
motion.  This  will  also  change  the 
playback  volume,  so  another 
technique  is  to  turn  the  knob 
rapidly to advance by more files.

Clip

Hold 2 sec., then release

+

Go to Previous Folder

Clip

Hold 2 sec., then release

+

Go to Next Folder

 


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Trigger Jack 

In Record mode, the Record Trigger jack can be used to synchronize the starting and/or 

stopping points of a recording: simply patch a trigger or gate into this jack. When a trigger or 

rising edge of a gate is received, recording will start (if it’s not already started) or stop (if it’s 

not already stopped). There are several uses for this:

Multi-track recording 
Using two or more WAV Recorder modules, you can patch the same trigger into all of the trigger 

jacks. Firing a trigger will start recording on all units simultaneously. Since each module is a two-track 
recorder, the number of tracks you can record will be twice the number of modules: two WAV 

Recorders can function as a four-track recorder, three WAV Recorders can function as a six-track 

recorder, and so on… 

Combining the .wav files from the microSD cards on all of your units is easy to do with most audio-

editing software packages. For example, the freely-available program Audacity can combine stereo 

recordings by copy/pasting the individual stereo tracks into one multi-track file.
See the 

Example Patch: Multi-track Recording.

You could even combine tracks in a computer-free environment by using a mixer to combine the 
playback outputs of all the WAV Recorders which were used to make the recording. Feed the stereo 
output of the mixer to an additional WAV Recorder and record the mix-down “live”.

Recording timed loops 

If you have a rhythmic patch, you can feed a slow clock into the trigger jack to record a “bar” or 

“measure” of the patch. If you just want to capture just one measure, plug in the trigger while the clock 

gate is low. When the clock goes high, recording will begin on the start of the measure (assuming your 

clock is synced to the start of the measure). When the next measure starts, the clock will go high again 

and cause the recording to stop, create a recording that’s exactly one measure long. If you’re making 

variations to the patch as it plays, you can keep recording more measures to capture a variety of 

loops.

Once the recording is stopped (the button is not lit up), flip the switch down to Playback. When the 

next trigger fires on the next measure, your loop will play in time. This technique allows you to create a 

new loop while the old one is playing (you’ll need to route/split/mix your signals in way that you can 
independently adjust the level of the WAV Recorder’s output and your source audio). You can even 

use the file browsing techniques to go between different variations of the loop you captured (see 

Browsing Files for Playback section).

Pausing Recording

If you start recording and then flip the switch to Playback, the recording will be paused. The button 

flashes red to indicate recording is paused. You’ll continue to hear the audio pass through, but it won’t 
be recording. To continue recording, flip the switch up to Record and then press the button again. It’ll 

turn solid red to show that you’ve resumed recording.

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Record

 


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Example Patch: Multi-track Recording 

Six-track recording 
The diagram above shows how you can use multiple WAV Recorder modules to record more than two 

tracks at a time. A common trigger can start and stop all the recordings at the same time. The trigger 

can be from a touch pad or any module that generates a manual gate or trigger. Using a passive mult, 
active mult, or stacking cables, split this trigger signal and run it to all the Record Trigger jacks.

Patch your audio signals into the IN jacks on the WAV Recorders. Check that the switch is set to 

Record on all the modules, and remember to refresh any cards that you’ve recently inserted. You also 

may wish to verify the recording rate settings and set all the modules to the same values. 
Turn all the Gain knobs to the same position unless you have a reason to record some channels louder 

than others. When you’re ready to record, fire the trigger to start recording. When you’re done, fire 

another trigger to stop. Copy the .wav file from each of the microSD cards onto a computer and 

combine the files into a multi-track file using any audio-editing software.

High precision phase alignment 
For most purposes, the files can be combined simply by snapping the beginnings to the same point. 

However, if you are doing some specific work that requires the phase differences between tracks to be 

exact, then you may need to line up the tracks manually. In our tests, a typical difference was between 

340uS and 1.7ms (15 to 75 samples at 44.1kHz). This is well under the perceivable latency threshold 

of human hearing. If your project requires a tighter tolerance than this, we recommend beginning the 

recording with a “clap” or some signal common to all tracks: this will make it easy to see how far to 

adjust each track along the time axis.


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Record

WAV RECORDER

Left

Right

IN

OUT

Clip

Input Gain

Busy

Playback

Record

0dB

-

+20dB

Record

WAV RECORDER

Left

Right

IN

OUT

Clip

Input Gain

Busy

Playback

Record

0dB

-

+20dB

Record

WAV RECORDER

Left

Right

IN

OUT

Clip

Input Gain

Busy

Playback

Record

0dB

-

+20dB

Trigger (start/stop 

Audio channel 1
Audio channel 2
Audio channel 3
Audio channel 4
Audio channel 5
Audio channel 6

OUT jacks can be used 
for monitoring (optional)

 


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Using the WAV Recorder as a Pre-amp 

Since the WAV Recorder can provide a wide range of gain or attenuation to stereo signals, it can also 

be used as pre-amp to interface external equipment with Eurorack modules. 
Patch any line-level, headphone-level, or modular-level signal into the IN jacks and turn the Gain knob 
until you see some signal but no clipping. The signal on the OUT jacks will now be at standard 

Eurorack audio signal levels and can be patched to any other Eurorack module.

For example, if you wanted to use your Eurorack modular system to process an online live stream from 
your smart phone, you could patch the phone directly into the Left IN jack using a mono or stereo 

cable. (If you want to get a stereo signal from the smart phone, use a stereo-to-mono adaptor and 
patch into the Right IN jack as well.) Turn the volume up on the smart phone, and turn the Gain knob 

so that you see some blue lights. You can now patch the OUT jacks to any other module that works 

with normal Eurorack audio signals.
Note: The WAV Recorder does not work with microphones that require voltage from the pre-amp. 

Busy Light 

The microSD card is safe to remove if you stop recording and wait until the Busy light turns off. If 

you’re in 

Playback mode and not currently playing anything, it’s also safe to remove the card. It’s not 

safe to remove it while 

Paused (you’ll lose the file you recorded).

You can corrupt the files on your microSD card if you pull it out while the Busy light is on. This is similar 

to unplugging a USB thumb drive or external hard drive from your computer while copying files. You 

might get lucky and keep your files; but, if the card starts to act weird, do a disk repair or “first aid” 

using Disk Utility on MacOS or fsck (or something similar) on Linux. After repairing the disk, copy all 

your files off, format it in ExFAT, and copy your files back on. Always keep backups of important files! 

Checking for Free Space

You can check the amount of free space on the card by holding the button down 

for 2 seconds while in Record mode. An animation of the lights will display while 

the card is being scanned. Once the lights stop animating, the number of lights 
that are off will show how many hours of free space you have available.

 If there 

are 8 or more hours of recording time available, all the lights will turn off when the 

animation stops.

For example, let’s say you hold down the button and the animation stops with five lights on and three 

off (see diagram below):

The fact that there are three lights off means that there are three to four hours of 

recording time available on the card.

Changing recording settings will change the amount of time available. If you went 

into System Mode and changed to mono recording, the next time you check for 

free space it will show six lights off (six hours mono = three hours stereo).

Checking for free space serves a dual purpose: if you insert a microSD card into the module while it’s 

powered on, the card will need to be mounted before it can be used for recording or playback. 
Checking for free space will mount the card safely and report the free space available. See 

Hot 

Swapping (next section).

If the card is ever detected as being full (or having less than 50MB in available storage), all 8 lights will 

flash brightly twice when you press record. The lights will keep flashing every 5-10 seconds until you 
flip to Playback mode or insert a new card and refresh it.

Note: The WAV Recorder will always leave about 50MB available for swap space.

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Clip

Hold 2 sec

Playback

Record

 


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Hot Swapping the microSD Card

As long as the 

Busy light is off, it is acceptable  to remove the microSD card (and put it into a 

computer to check the files, etc) without powering down the WAV Recorder. You can even re-insert a 

different card.
When you reinsert the microSD card into the WAV Recorder while the module is powered on, you 
must re-mount it (refresh it) by holding the button down for 2 seconds while in Record mode. This will 

display an animation which shows how much available space is on the card (see 

Checking for Free 

Space section). After the animation is complete, the card is ready for recording and playback.

If you forget to refresh a newly inserted card and try to start recording or playing immediately, the WAV 

Recorder will attempt to re-mount the card before recording or playing. This can cause a delay and 

sometimes a “hiccup” in playback or recording.

You do not need to refresh a card if it’s already inserted when you power up the WAV Recorder. The 

module always mounts the current card as part of its normal boot-up sequence.

LED Signal Meter and Clipping

The LED Signal Meter shows the output signal level:

-0.4dBFS (20Vpp): The red LEDs turn bright solid (clipping)
-2.6dBFS  (16Vpp): The red LEDs turn on dimly
-8dBFS  (8.5Vpp): The white LEDs turn on
-12dBFS  (5Vpp): The upper blue LEDs turn on
-21dBFS  (1.75Vpp): The lower blue LEDs turn on

The Signal Meter shows the actual signal present on the output jacks-whether you are recording or 
playing. By adjusting the Gain knob while watching the Signal Meter, you can set your level 

appropriately and avoid clipping.

Recording For Long Periods 

The maximum size of any .wav file is about 4GB. Depending on the recording rate, this could mean 
anywhere from 2 to 13 hours. The WAV Recorder can continue recording beyond this limit by splitting 

ultra-long recording sessions into a series of files. Once a file becomes about 4GB large, the WAV 
Recorder
 will close the file and keep recording into a new file. In this way, you can fill your entire card 

with recordings if you leave the module recording without interruption. The Wav Recorder can even 

record for days or weeks (depending on the size of you card and the sample rate you select in System 

Mode). The included card is 16GB and will record for about 27 hours before stopping at the default 

recording rate (44.1kHz, 16-bit, stereo).

We highly recommend using a faster card for any long recording (see Recording Rates section). 

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System Mode 

You can change the recording sample rate, bit depth, and number of channels in 

System Mode.

To enter System Mode, first make sure that the switch is flipped up to Record, and 

that the WAV Recorder isn’t recording or paused. Then, hold the button down for 

5 seconds. As you wait, the lights will show you the free space available (see 

Checking for Free Space); keep holding the button down. After about 5 seconds, the button will turn 

blue and you can release it. You are now in System Mode.

The left column of lights indicates which parameter you are editing, and the right column indicates the 

value of that parameter.

To select the parameter you wish to edit, tap the button. The light on the left column will cycle through 

the three options. 

To change the value of the parameter you’ve selected on the left side, turn the Gain knob. The LEDs in 

the right column will change when you turn fully to the left (0%), fully to the right (100%) and/or to the 

center (50%). The lights on the right column will tell you the value of the parameter you selected as 

follows:

A red light in the left column indicates the Sample Frequency menu; its options, listed in the right 

column, are 96kHz (red), 48kHz (white), or 44.1kHz (blue).

A white light in the right column indicates the Bits menu; its options, listed in the right column, are 

24 bits (white) or 16 bits (blue).

A blue light in the left column indicates the Channels menu; its options, listed in the right column are: 

stereo (red and blue), mono (white).

Note: The System Mode feature only changes what happens when you record, not when you play. 
Playback always happens at the file’s native sample rate and bit depth. 

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Sample Freq.

96kHz

48kHz

44.1kHz

Clip

24 bits

16 bits

Bits

Hold 5 sec

Playback

Record

Tap to select 

parameter

Turn to set value

Clip

Channels

Mono

Stereo

 


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Recording Rates and Selecting microSD Cards 

The microSD card included with the WAV Recorder is a Class 10 card and is sufficient for recording at 

many high-fidelity rates. With the included Class 10 card, we recommend 44.1kHz/16-bit/stereo, 

48kHz/24-bit/mono, or 96kHz/16-bit/mono. The default factory setting is 44.1kHz/16-bit/stereo.

To achieve faster rates such as 96kHz/24bit, or 48kHz/24bit/stereo, a high-speed UHS Speed Class 3 

(U3) card is required. Specifically, our tests found one card to be of sufficient speed to record at the 

fastest rates of the WAV Recorder:

• Samsung MicroSDXC EVO Plus (64GB) MB-MC64GA

We found another card which performed well, but had a very occasional glitch at 96kHz/24bit/stereo:

• SanDisk Extreme PLUS microSDHC (32GB) SDSQXBG-032G-GN6MA

At time of printing, the cost of either of these cards is typically around $20-$30, and they’re available 

on Amazon or any number of electronics retailers. Beware of cheap look-alikes, and only purchase 

from a reputable seller. Avoid cards with a price under USD 20, they are likely to be fakes. 

The following table reports our findings:

*At 44.1kHz/24bit/Stereo on the included Class 10 card, a 1 hour recording has a 4% chance of 
dropping samples. Using a faster card is recommended.
**At 48kHz/24bit/Stereo or 96kHz/24bit/Mono on the included Class 10 card, a 1 hour recording 
has a 25% chance of dropping samples. Using a faster card is recommended.

While dropping samples is typically not acceptable, we allow the WAV Recorder to attempt to record 

beyond the limits of the card you choose for several reasons:
• Short samples have almost no chance of containing glitches. Thus, capturing percussive or brief 

samples at high rates is OK, even with slower cards.

Freq.

Bits

Stereo/Mono  Included card 

(Class 10)

Recommended card 
(Samsung EVO Plus)

44.1kHz

16 bit

Mono

Stereo

24 bit

Mono

Stereo

√*

48kHz

16 bit

Mono

Stereo

24 bit

Mono

Stereo

/X**

96kHz

16 bit

Mono

Stereo

X

24 bit

Mono

/X**

Stereo

X

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• For some field recordings and other purposes where the recording will be heavily edited, dropped 

samples may be acceptable.

• When recording repetitive sounds where it’s easy to record a sound multiple times in one take, 

having one bad section may not be a problem.

If none of these circumstances apply, use a faster card, record at a slower rate, or record in mono.

For most audio recording purposes, 44.1kHz or 48kHz is excellent quality. If the recording level is 

sufficiently high, a bit depth of 16-bits will be of high fidelity. If you only require mono samples, we 

recommend changing to mono recording mode, and you will be able to record at a higher rate if you 

wish.

Dropped Sample Log
The WAV Recorder will allow you to record at any sample rate using any card, but if you surpass the 

limits of your card, there is a chance the recording will have some dropped samples. The longer the 

recording time, the greater the chance this will happen. You may find that making short recordings 

(under a few minutes) works perfectly for you at any rate. However, you run the risk of dropping 

samples in the recording or creating an artifact in the playback of the .wav file. Depending on your 

purposes, this might be unacceptable. The solution is to use a faster card (see list of recommended 

cards above).

If any samples are dropped during recording, the WAV Recorder will create a text file and log the exact 

time position of the dropped samples. The name of the log file will be the same as the name of the 

recording, with “.txt” on the end. If you find such a file on your microSD card, open it up and read the 

time position of the glitches. Play the .wav file at those times to determine if the glitch needs to be 

cleaned up, or if it isn’t a problem. This is just a band-aid (in case you accidentally record at a higher 

rate than your card can allow, and there’s no chance of a re-take). To avoid the possibility of dropped 

samples when recording at any rate, either use a fast microSD card or keep your settings at a lower 

rate.

Checking the Firmware Version 

When you power on the module, the LED Signal Meter will briefly show the firmware version number. 

The button will be magenta (pink) while the version is being shown.

The left column of lights indicates the major version number (e.g 1.x, 2.x, etc..). The right column 

indicates the minor version number (e.g. 1.0, 1.1, 1.2, etc..). The bottom light represents “1”, and the 

top light represents “4”. A “0” is represented by no lights on that side.

For version 1.0 (this version), the bottom left blue light will be on, and the other seven lights will be off.

Updating Firmware (Audio Bootloader) 

You can update the firmware by playing an special audio file into the Record jack. When new firmware 

versions are released, the firmware audio files can be downloaded at http://4mscompany.com/

wavrec.php. Check/Follow/Like the 4ms Twitter, Facebook, or Instagram social media feeds to be 

notified of firmware upgrade availability, or email us via our website.


1. Unplug all cables and power off the module.
2. Connect a computer or smart phone audio output to the Left IN jack. Remove your phone case, it 

may be preventing the cable from fully plugging in.

3. Connect the Left OUT jack to an amp/speakers so you can listen. Turn the amp/speaker volume 

down — this is going to be LOUD!

4.

Set the computer/phone's volume to 100% and the audio player software to 100% volume. Turn 
off all audio and vibrate notifications. Close any applications that make notification sounds.

5. Hold down the button while powering up the WAV Recorder. The button should start flashing 

green. Release the button.

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6. Begin playing the file. Immediately you should see the button flash white, and the other lights flash 

a lot. You should be hearing the sounds very loudly out the Left OUT jack.

7. If the sound stops before the file is done playing, there was an error. The button will flash red.

a. Stop the file and rewind to the beginning.
b. Check all cables are plugged in tightly.
c. Tap the button. It should turn green again.
d. Play the file again from the beginning.

8. If the file loads successfully, the WAV Recorder will display a chase sequence on the LEDs and the 

button will alternate green and blue. Press the button to start using the new firmware.

Tip: some audio interfaces play a pop when they first start playing a file. If this happens, the button 

light will turn red as soon as you start playing. One way to overcome this is to hit the button light 

immediately after pressing play on the computer, but before the noise starts playing (there’s a 2 

second lead time of silence). Or, an easier way to get around this is to use a different device (smart 

phones seem to work better than computers for the purpose of updating our firmware).
Tip: Do not play from software like Ableton. We have seen that some software will alter the playback, 

which is not desirable here. Play from simple, basic software such as VLC, QuickTime, Windows 

Media Player, or Chrome. Turn off any EQ or “Bass Boost” settings.
The open-source licensed source files (in C, for compiling with gcc-arm) can be found at https://

github.com/4ms/ (note: as of printing of this manual, this is not yet posted).

microSD Card 

We include a Class 10 card with the WAV Recorder, which is sufficient for recording at 44.1kHz. If you 

need to record at a higher rate, use a faster card. See 

Recording Rates section for recommended 

cards.

Never remove the microSD card while the Busy light is on! 

It’s OK to remove it if the Busy light is off. After inserting a card while the module is powered up, flip to 
Record mode and hold the button down for 2 seconds 

to refresh the card. This will mount the card and 

display the available free space on the card.

How to format a new microSD Card 

Format new cards as ExFAT (preferred) or FAT32 

(acceptable). See screenshot (right) for how to set 

MacOS standard “Disk Utility” program.

We recommend formatting a cards from time to time 

to defragment. A freshly formatted card will perform 

better than a card that had its files deleted. 

Formatting de-fragments a card, while dragging files 

to the trash can does not.

Future Integration with 4ms Listen modules 

There’s a header on the back to connect to the 

4ms Listen headphone/line mixer modules. This will 

allow you to record directly off the output mixer without any patch cables. See the 

Listen user 

manuals.

*Note: at time of printing, the Listen modules are not yet released. See the Listen manuals for 
connection details when those modules are released. 

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Electrical and Mechanical Specifications 

• 6HP Eurorack format module 
• 0.98” (25mm) maximum depth 
• 10-pin Eurorack power header 
• Power consumption (maximums):  

• +12V @ 112mA 
• -12V @ 12mA 
• +5V rail not used 

• Audio 

OUT

 jacks 

Frequency Response: 

File:Out = +/-0.1dB max deviation at 20Hz - 20kHz 

21V peak-to-peak = full scale 

Up to +20dB digital gain can be applied while playing using Gain knob 

• Audio 

IN

 jacks 

Signal-to-Noise Ratio (SNR) 

Measurements taken from recordings made in a typical Eurorack case, powered by a 4ms Row 

Power 40 module: 

-91.7dB @ 16-bit, 44.1kHz 

-88.9dB @ 24-bit, 96kHz 

Frequency Response: 

Out:In = max +/-0.1dB from 20Hz to 15kHz. -0.5dB at 20kHz  

20V peak-to-peak maximum before clipping 

Up to +20dB digital gain can be applied while recording or monitoring using 

Gain

 knob 

Record  

 jack 

Incoming trigger starts/stops recording, or starts/re-starts playback 

Trigger voltage must be > 1.6V, rising edge is detected 

• microSD card slot accessible from front panel 

Class 10 card included (16GB) 

 

Jumpers 

The PCB has one jumper labeled “JUMP”, which fits on a 2-pin header 

located at the bottom right of the PCB. 

The jumper must be installed to enable the normalization of the Left IN jack to 
the Right IN jack. If this jumper is missing, patching a signal into the Left IN 

with nothing plugged into the Right IN jack will record silence on the right 

channel. 

The jumper should only be removed if you are connecting the WAV Recorder 

to a 4ms Company Listen module. See the Listen manual for connection 

details.

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