HX3 Leslie Interface

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Connecting LDR/Leslie Interface Board (obsolete)

Leslie/LDR Interface board

Only for older HX3 mk2 mainboards. Obsolete - for reference only!

The LDR/Leslie Interface (see also german page LDR/Leslie-Interface-Platine and documents in Github repo folder ADAPTER) is required for direct connection of Leslie families 715, 760 and 147 without need of Combo Preamp. It contains a two-channel preamp for organ main (manuals) and pedals, a mixing stage and relais switches for Leslie control, also a power supply capable of 5V/500mA. This board is intended for skilled technicians, as it might require adjustments and re-wiring to fit your needs.

Main channel is routed either from HX3 main organ output or Leslie tube amp simulation output (recommended for use with transistor Leslies) to LDR/Leslie Interface Board's preamp. A volume pot might be inserted between preamp and mixing stage. To control Leslie speed relais, 10-pin header connect to HX3 PL12 (also additionally in parallel to other switches). Connection to HX3 PL7 on second 10-pin header is required only when a Leslie button switch is to be used (momentary "button" contact, often found on organ's swell pedal).

Green power connector carries 5V DC to supply HX3 board. Note wire jumpers for 117V or 230V mains and set operating voltage trimpot to 5.0V on green power connector.

We recommend Yamaha FC-7 type expression pedal plugged into HX3 SWELL jack, but for OEM installations in older organ consoles the LDR-to-voltage converter on Leslie I/F board may also be used. It translates swell pedal's LDR resistance to swell control voltage of HX3. SWELL jack has to be removed for this purpose. LDR stage requires proper calibration of GAIN and OFS trimpots to obtain a control voltage range of approx. 0 (soft) to 3.3V (full swell) on HX3 swell input.

Other two trimpots set preamp gain. Adjust gain for full Leslie volume. We can supply a set of 3-wire cables with plugs to connect to HX3 audio and swell. Inportant: Plug polarity reqires 3-pin headers to be installed from HX3 component side instead of 1/4" jacks. If installed from solder side, reverse pinout accordingly. Leslie connection is described in schematics of LDR/Leslie Interface Board.

Connection of Leslie interface board to 11 pin Leslie

PL12-1 PL12-2 PL12-3 PL12-4 PL10-1 PL10-2 PL10-3 Remark
Leslie pin 8 (slow) Leslie pin 7 (fast) Leslie pin 6 (power) Leslie pin 5 (common) Leslie pin 1 (rotary) Leslie pin 4 (Gnd) Leslie pin 2 (stationary) Set HOAX JP6 to STEREO


Connection of Leslie interface board to 9 pin Leslie

PL12-1 PL12-2 PL12-3 PL12-4 PL10-1 PL10-2 PL10-3 Remark
Leslie pin 7 (slow) Leslie pin 6 (fast) not connected Leslie pin 1 (Gnd) Leslie pin 2 (audio) Leslie pin 1 (Gnd) not connected Set HOAX JP6 to MONO


Connection of Leslie interface board to 147 Leslie 6-pin

PL6-1+2 PL6-4+5 PL10-1 PL10-2 Remark
Leslie pin 4 Leslie pin 5 Leslie pin 6 (audio) Leslie pin 1 (Gnd) Set HOAX JP6 to MONO

Note: Additional power relay recommended for 230V HV on 147 Leslie pin 4 and 5. Bridge pin 2 to pin 3 of Leslie 6-pin connector.