LOOPER STOP

Construction

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In addition to the completed stripboard assembly, the following parts will be needed to complete the project...
• A Hammond 1455 series extruded aluminium enclosure - part no: 1455J1202BK
• 1 (or 2) x 1/4" (6.35mm) switched mono (TS) jack sockets. The type listed - HERE - works well
• 2 x 2.1mm DC 'power plug' chassis socket. ( See - HERE - for a typical example )
• 1 x 1.3mm DC 'power plug' chassis socket. ( See - HERE - for a typical example )
• 1 x 1.3mm DC 'power plug' . ( See - HERE - for a typical example )
• 1 x 30cm length of black equipment wire
(10/0.1mm (for Lekato 9 slot Looper) or 7/0.2mm (for Ditto+ Looper)

• Just click on any photo below to view full size •

Enclosure end plates:
The enclosure plastic end plates need to be drilled, to allow for 1 (or 2) 6.35mm (1/4") jack sockets to be fitted to one end, and 2 x 2.1mm power plug sockets - plus 1 x 1.3mm power plug socket - fitted into the other.
A spacing of 20mm between the 3 x power plug sockets, and a space of c.40mm between the jacks - when 2 are fitted - seems to work well.
The photos on the right show typical examples.

'Power Plug' sockets:
The 2 x 2.1mm power plug sockets are wired in parallel, so that power can be connected to this interface on one socket, and passed through to the Looper pedal on the other. (The centre pins are negative for both sockets)
The 3rd socket is a single 1.3mm power plug type, and the centre pin is used to connect the opto-coupled output from the interface to the internal switch on the Looper pedal. The socket outer connection is not required, as the second switch connection is connected in the Looper to the negative DC power(system 'gnd').
(This photo shows this 'gnd' connection included, but it's not essential).

Jack socket(s):
The jack socket(s) are mounted through the other end plate... The photo shows a wire link made between the 'switched' tip connection and the 'unswitched' sleeve (gnd) connection... This will help to defeat false triggers if the external switch is plugged in whilst the unit is powered.
(A single jack socket is shown in this photo. Typical spacing for a double jack version is c.35 to 40mm).

Looper modification:
It will be necessary to remove the bottom of your Looper pedal to allow access to the underside of the internal PCB.
The 'TC Ditto+' and the 'Lekato M00775' (and I suspect most others) use a single pole, normally open, momentary switch to control the unit.
One terminal of that switch is connected directly to the negative of the 9V DC power supply. This DC negative (centre pole of the power plug) is also connected to the Looper casing, and the 'sleeve' connections of the jack sockets.... It is essentially a system 'ground' reference.
Taking appropriate CMOS anti-static precautions, carefully solder the stripped and tinned end of a single length of around 20cm of equipment wire to the ungrounded terminal of that switch....
The gauge of equipment wire will need to be either 7/0.2mm (Ditto+) or 10/0.1mm (Lekato) - (see routing notes below).
The photo to the right here shows the exact location of the required switch PCB termination on both the Ditto+ and Lekato Looper PCBs.

External connection out:
This single core cable attached to the PCB will need to 'exit' the Looper via an appropriate gap in the unit casing. With both of the pedals tested so far, suitable 'gaps' are very limited!...
• In the case of the Ditto+ it needs to exit adjacent to the input jack socket. (7/0.2mm gauge wire)
• In the case of the Lekato it needs to exit adjacent to the USB socket. (10/0.1mm gauge wire)
The size of equipment wire best suited is ideally 7/0.2mm - and this is used for the Ditto+.
The Lekato uses thinner 10/0.1 mm wire, simply because there is less room adjacent to the USB socket - and no room via the jack sockets!
The other end of this wire is terminated to the centre pole connection of a 1.3mm power plug. This plug size is chosen to avoid confusion with the 2.1mm power plugs used for the power supply sockets.
The photos to the right here show details of the wire connection routing for both units.
(Note that the Lekato photo also shows the industrial strength 'Velcro' used to mount the Looper onto the top of the interface enclosure).

Testing:
The completed Interface stripboard can be tested for correct function before it is connected to the Looper pedal.
The green LED - which you can see in the photo on the right to the left of the 4N32 opto-coupler - is connected in series with the 4N32 LED. This LED will illuminate, duplicating the pulses supplied by the logic output to energise the 4N32.
• In the case of the 'One Switch' version, pressing the connected external footswitch will alternate between one and two 'flashes' from the LED, with each new press of the switch. Each LED flash is very short - only about 50mS - but is quite visible if the logic is working correctly.
• In the case of the 'Two Switch' version, one switch is designed to mimic the switch on the Looper itself, to provide all the functions of the Looper. When this switch is pressed, the LED follows the function of the switch. Hold the switch down and the LED remains on... Release the switch and it goes off.
The second switch is a dedicated 'stop' switch. If the first switch has been pressed to start the Looper, then pressing the second switch automatically generates a 'double pulse' LED flash, to mimic the 'double tap' stop function.
Note that this only happens once. Pressing the stop switch again will do nothing. It is only capable of generating the 'double pulse' necessary to stop the Looper after the main switch has been pressed to set the system running.

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