jroo loop User manual

loop
by jroo
loop is a frippertronics-style stereo digital tape loop, echo and delay module with
adjustable tape speed, play head position, feedback and audio levels. It has a
customizable loop length of up to 2.5 minutes.
Contents
- Overview
- Getting started
- Detailed functionality
- Knobs
- Lights
- Record Switch
- Jacks
- Erasing the loop
- Patch ideas
- Firmware updates & support
Overview

Knobs
in - level of audio input
speed - speed and
direction of tape (for both
recording and playback)
feedback - amount of
playback signal sent back
to incoming audio
dry/wet - mix between
incoming signal and
playback from tape
playhead - distance
between record head and
play head
Lights
green solid - play
indicator
green blink - on loop start
red - record indicator
alternating slowly - ready
for initialization
alternating quickly - erase
warning
Switch
record - used for toggling
recording and erasing the
loop
Jacks (-5V to 5V)
record - gate to toggle
recording
speed - CV to control tape
speed and direction
feedback - CV to control
feedback level
dry/wet - CV to control
dry/wet mix
in 1, in 2 - dual mono
inputs
out 1, out 2 - dual mono
outputs
loop is modeled after tape loop systems where audio is recorded to and played back
from a tape that’s continually looping. Several interesting effects can be accomplished
in a system like this when the position of the play head, tape speed, direction, and
audio and feedback levels are modified. loop gives you manual and CV control over each
of these.
Frippertronics is a practice pioneered by guitarist Robert Frip utilizing a tape loop
strung between two analog tape machines, one to record the signal and the other to
play it back. This module acts as both.
loop’s signal flow mimics that of a traditional tape loop system. As tape passes by the
position of the record head, the existing audio on the tape is erased and an incoming
audio signal is recorded in its place. The audio that is recorded to tape is played back at

the position of the play head. The audio signal from the play head can be mixed with the
incoming signal for output, or fed back and mixed with the incoming audio to be
recorded again.
The following sections will walk you through some of these effects and provide details
on loop’s controls.
Getting started
To follow along with the examples below put your loop in the following configuration.
We’ll call this the “default configuration”.
●set the audio input level to full by turning the in knob fully clockwise
●set the tape speed to 1x by turning the speed knob fully clockwise
●set the feedback level to zero by turning the feedback knob fully
counterclockwise

●set the dry/wet mix to 50% by turning the knob to a 12:00 position , pointing
straight up
●put the play head and the record head in the same position by turning the
playhead knob fully counterclockwise
●set the record switch to off (down)
●patch an audio source into the in 1 jack
●patch your audio out through the out 1 jack.

Set the loop length with the initial recording
When you first power on loop , the green and red lights will be alternating slowly. This
means that the module is ready to record the initial loop. Start by flipping the record
switch on (flipped up) and then, after five or six seconds, switching it off (flipped down)
again.
While you were recording, both lights turned to solid. Solid red means audio is recording
to tape and solid green means the tape is playing. When you flipped the record switch
to off (down), the recording stopped and the red light turned off because it was no
longer recording.
The length of this first recording determines how long your tape loop is. During playback,
when the end of the loop is reached, it will immediately start again at the beginning and
continue looping until you stop playback or erase the loop. The length of this loop will
not change until you erase the loop.
You should now see a solid green light that quickly blinks every five or six seconds (the
length of your loop) and hear the audio that you recorded repeating on a loop. The quick
blink happens every time the loop starts over.
Change the dry/wet mix
Your dry/wet mix is currently set at 50% so you will hear both the incoming audio and
the tape loop being played at equal volumes. To hear just the incoming audio, turn the
dry/wet knob fully counterclockwise for a 100% dry (original, unprocessed) signal. To
hear just what’s recorded to tape, turn it fully clockwise for a 100% wet (processed)
signal. Keep it fully clockwise for now and listen to what’s on the tape as it loops.

Control the tape speed
Now that your loop is playing, change the tape speed with the speed knob. Fully
clockwise is 1x speed. Slowly turn it until it reaches the 12:00 position (pointing
straight up) . The playback will slow down, then stop and the green light will turn off.
You’re now at 0x speed and the tape isn’t playing. Continue turning counterclockwise
and the tape speed will slowly speed up again but in reverse. Fully counterclockwise is
-1x speed, or 1x speed in reverse. Play with different speed settings for a while. Notice
that as the speed changes, the pitch also shifts. When you’re ready, bring the speed
knob back fully clockwise to play at 1x speed.
Change the play head position
In traditional tape loop systems there are two “heads”, one that records audio to a tape
and another that picks audio up off the tape and plays it back. The loop module follows
the same principle. Audio is recorded to one part of the loop at the record head position
and audio is played back from another, the play head position. The playhead knob
determines how far apart record and play heads are. This controls how much delay
exists from when something is recorded and when it is played back.
The default position for the playhead knob is fully counterclockwise. Here, the play head
and the record head are in the exact same spot. This means that as soon as something
records, it immediately plays back. As you turn the knob clockwise, the play head moves
further behind the record head and increases the delay.
Turn the playhead knob fully counterclockwise and flip the record switch up to begin
recording. Because the record head and play head are in the same position, you should
hear the audio that you have patched in with no delay. What you’re actually hearing is
the immediate playback of what’s recorded on the tape. Turn the dry/wet knob to dry so
you’re listening to the dry input. Now set it to wet and notice that the audio is the

same. That’s because what’s being recorded to tape is immediately being played back
so it just sounds like live audio.
Now let’s play with the play head. Go ahead and stop recording for now (flip the switch
down ), make the dry/wet mix 50% (dry/wet knob at 12:00, pointing up ) and set the
playhead knob to 12:00, pointing up . Start recording again. You’ll now hear your input
playing back again but this time with a delay. Setting the knob to 12:00 makes the
playback distance equal to half your loop length so the delay is half the time of your
total loop. If your loop is six seconds the delay will be three seconds.
Play with playhead positions to set different delay times. When you find a delay interval
that you’re happy with, set the dry/wet knob to various positions to change the volume
of the live audio vs. the delayed audio.
Add feedback
It’s possible to take the audio that’s being played from the tape and send it back to the
record head so it’s recorded again, creating a feedback loop. Turning the feedback knob
clockwise increases the level of the audio that’s sent back to the record head. While
you’re still playing back the delay that you previously set, slowly increase the feedback
level and notice that the delay now repeats multiple times instead of just once and it
fades out over time. The more you increase the feedback level, the more times you hear
the repeated signal and the longer it takes to fade out. Turning the feedback knob fully
clockwise will result in the repeated signal never fading out and accumulating more and
more audio every loop. This can get crazy quickly! Especially if the playhead and record
head positions are close to each other. To tame the feedback, turn the feedback knob
back down ( counterclockwise ).
Erase the loop

To erase and reinitialize the tape, stop recording (record switch flipped down ), set the
tape speed to zero (speed at 12:00 ) then flip the recording switch on, then off, three
times. While flipping, the record and play lights will flash quickly to let you know that
you’re about to initialize the loop. To abort the initialization before flipping on and off
three times, stop flipping and wait two seconds. Once the loop is initialized, the tape is
erased and you can record another loop and set a new length.
Bring it all together
Now that you have a handle on recording, the dry/wet mix, tape speed, play head
position and feedback, play around with different combinations of each and see what
you can come up with. Once you feel like you have a handle on the manual controls,
bring CV in to toggle the record, speed, feedback and dry/wet settings. More patch
ideas can be found later in this document.
Detailed functionality
Knobs
In
The in knob determines how much of the incoming (dry) audio signal is passed to loop.
Fully clockwise is 100%, full volume. Fully counterclockwise is 0% and no audio is
passed in.

Speed
The speed knob sets the speed of the tape. The speed of the tape determines the speed
at which the tape moves relative to the record and playheads. If speed is set to 1x
when recording then set to 0.5x on playback, what’s played back will sound twice as
slow and at a lower pitch. Alternatively, speed is set to 0.5x when recording and then
set to 1x at playback, it will move twice as fast and play at a higher pitch.
Feedback
The feedback knob determines how much of the signal that’s played back from tape is
sent back to be mixed with input to be recorded again.

Dry/wet
The dry/wet knob sets the mix between the incoming audio (dry) signal and what’s
played from tape. Fully counterclockwise is fully dry and only the incoming audio signal
is output. Fully clockwise is fully wet and only what’s played from tape is output. A
12:00 position (straight up) sets an equal mix of dry and wet, meaning the incoming
audio and tape playback are output at equal levels.
Playhead
The playhead knob sets the position of the play head relative to the position of the
record head (or the distance between the record head and the playhead). This
determines how much time there is between when a signal is recorded to tape and
when it is played back. The knob sets the value relative to the length of the loop. If the
tape is moving forward (the tape speed is positive), fully counterclockwise will set the
playhead in the same position as the record head meaning audio will be played back as
soon as it is recorded. At a 12:00 position (straight up) , the play head is half a loop
behind the record head. For example, if a loop length is six seconds and the tape is
being played at 1x speed, the playhead will play back an incoming signal 3 seconds
after it is recorded. Fully clockwise is a full loop length behind. Note: playback time will
be different depending on which direction the tape is moving.To understand this, look at
the “traditional tape loop system” graphic near the beginning of this documentation. In
this case, if the tape is moving forward, it will play back relatively soon then loop all the

way around to the record head again. If the tape is moving in the opposite direction, it
will loop all the way around first, before playing back, resulting in a longer delay.
Lights
loop has two lights to indicate the status of the module: green and red.
Alternating slowly - loop is in the initialization state and is ready for its first recording
Alternating quickly - erase warning: a loop erase/initialization is being initiated
Solid red - incoming audio (and feedback) are being recorded to tape at the record head
position
Solid green - audio is being played back from the play head position
Green blink - when playing, the green light will quickly blink off then on again each time
the tape loops. If a loop length is six seconds, it will blink once every six seconds.
Record Switch

The record switch is used to toggle recording audio to tape on and off. Up is on and
down is off. The record switch is also used when erasing and initializing the loop (see
“Erasing the loop” below). Note: the minimum length for an initial recording is 0.2
seconds, even if the initial recording is disabled before 0.2 seconds has passed. There
is no minimum for other recordings, just an initial recording.
Jacks
Record
Type: Gate
Range: 0V low, > 0.7V high
The record jack is a gate in that toggles recording. The gate is off at 0V and it is on at
anything above 0.7V. The record jack and record switch have an OR relationship,
meaning that if either is on, a record command will be sent to the loop.
Record Switch
Record Gate
Recording
Off
Off
No
Off
On
Yes
On
Off
Yes
On
On
Yes
Speed
Type: CV
Range: -5V to 5V
The control voltage input at the speed jack is combined with the speed knob to control
the tape's speed. A control voltage of 5V adds 1x to the speed set by the speed knob, a

voltage of -5V subtracts 1x (or adds -1x) to the speed and 0V does not influence the
speed set by the knob.
Speed Knob
Speed CV
Tape Speed
1x
0V
1x
1x
5V
2x
1x
-5V
0x
0x
0V
0x
0x
5V
1x
0x
-5V
-1x
-1x
0V
-1x
-1x
5V
0x
-1x
-5V
-2x
Feedback
Type: CV
Range: -5V to 5V
Control voltage sent through the feedback jack is combined with the feedback knob to
control the feedback level. 5V adds 100% to the feedback value set by the knob, -5V
subtracts 100% and 0V keeps the value unchanged. The feedback level is bound to a
range of 0% to 100% even if the combination of feedback CV and the knob value go
outside of this range.
Dry/wet
Type: CV
Range: -5V to 5V

Control voltage sent through the dry/wet jack is combined with the dry/wet knob to
control the dry/wet mix. Positive voltage makes the mix more wet and negative voltage
makes the mix more dry. +5V is the equivalent of a half knob turn clockwise and -5V is
the equivalent of a half knob turn counterclockwise.
In 1 and In 2
Type: Audio
Dual-mono audio inputs. AC-coupled.
Out 1 and Out 2
Type: Audio
Dual-mono audio outputs. DC-coupled. 48kHz / 24-bit.
Erasing the loop
The tape loop can be erased and put in the initial state it was in when the loop module
initially started. This can be useful if you want to erase the audio on the tape and/or
create a new loop length. To erase and initialize, the speed of the tape must be set to
zero. With the tape speed at zero, flip the record switch up and down three times. While
flipping up and down the green and red lights will alternate quickly , indicating that an
initialization is being initiated. After the switch is flipped up and down three times, the
loop will be erased and initialized and the green and red lights will alternate slowly ,
indicating that the module is once again ready for an initial recording.
Aborting an initialization
If an initialization has been initiated but isn’t complete yet, it can be aborted by no
longer flipping up and down and waiting two seconds. When the green and red lights
stop alternating quickly , the initialization has been aborted.

Patch ideas

- Quantized loop: to keep your loop in sync with the clock, use a gate with the
length of a bar or two to create your initial recording.
- Bring your own wow and flutter with speed CV.
- Quantized playback - Tape speed also determines pitch. As playback slows down,
the pitch lowers and as it speeds up, the pitch rises. The following control
voltages set the speed to pitches in semitones relative to your incoming signal,
allowing for harmonization between the incoming audio and what’s played off of

tape. The voltage changes that you send depend on whether the tape is playing
forward (1x) or reverse (-1x).
Record a loop to tape and mix it with incoming audio. Set the speed to 1x and
use the following table to change the tape speed with control voltage. Drop
what’s being played an octave by sending -2.5V to the speed CV. Now move it up
an octave by sending +5V to the speed CV. Keep it in harmony by pitching it up a
perfect fifth (7 semitones).
Change
(semitones)
Voltage
change if
forward (1x)
Voltage
change if
reverse (-1x)
-12
-2.500
2.500
-11
-2.351
2.351
-10
-2.194
2.194
-9
-2.027
2.027
-8
-1.850
1.850
-7
-1.663
1.663
-6
-1.464
1.464
-5
-1.254
1.254
-4
-1.031
1.031
-3
-0.796
0.796
-2
-0.546
0.546
-1
-0.281
0.281
0
0.000
0.000
1
0.297
-0.297
2
0.612
-0.612

3
0.946
-0.946
4
1.300
-1.300
5
1.674
-1.674
6
2.071
-2.071
7
2.492
-2.492
8
2.937
-2.937
9
3.409
-3.409
10
3.909
-3.909
11
4.439
-4.439
12
5.000
-5.000
Firmware updates & support
[email protected]
https://jroo.co/products/loop/firmware
Acknowledgements
Special thanks to Sarah, Nick Brethauer, M.Christian, Christopher H. M. Jacques, Mike
Jett, Mike Gintz (Mute City), Fayek Helmi (256k), Ben Rosenbach (benirose), Alex
(3hands4milo), Dom at Cicada Sound, Gabriel, Manu and Ottawa Experimental Music
Discord, Earth Modular Society, EZBOT, lines, Teletype Study Group, Europi and
Winterbloom communities for your support, encouragement and inspiration. No way this
happens without all of you.
Designed and assembled in Canada
©2022