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Controlling A Neo Instruments Ventilator II From A Stage Organ

DIY Cable Solution By Hugh Robjohns
Published April 2023

Rotary Club

This DIY adaptor cable will fool your organ into thinking a real Leslie is attached.

The Neo Instruments Ventilator II Leslie emulator pedal (reviewed in SOS November 2014) is widely regarded as a one of the very best hardware Leslie cabinet simulators currently available, with many experienced organ players preferring it to the simulators built into their stage organs. There are several versions of the Ventilator of different sizes and capabilities, and many users are quite happy to tread on the pedal’s own stomp buttons to change Leslie speeds. However, the large Ventilator II model includes a remote‑control connection which allows speed switching via a separate foot pedal, a classic ‘half‑moon’ (Hammond CU‑1) switch mounted on the organ itself, or even an expression pedal for fully variable speed control.

Socket To Me

Despite all this versatility, some players prefer to use the dedicated fast/slow speed buttons on the organ console itself, which normally control the internal Leslie emulator. Fortunately, most stage organs have a special socket for connecting a real Leslie speaker and, when plugged in, the onboard emulator is automatically disabled and the fast/slow controls routed to the external Leslie instead. But wouldn’t it be great if there were a way of fooling the organ into believing the Ventilator II pedal is a real Leslie, thereby disabling the internal emulator and routing the fast/slow controls directly to the pedal? Well, there is! And it just requires a custom adaptor cable to plug into the organ’s Leslie socket.

There have been a lot of different Leslie speaker models over the years, and they’ve used a variety of similar‑looking but incompatible connection formats. But thankfully, modern stage organs and Leslies really only use two connection formats: an 8‑pin DIN socket or an 11‑pin Amphenol socket; the latter is far and away the most common.

Since neither connector carries mains power (unlike most of the vintage Leslie interfaces) it’s relatively straightforward and safe to construct an adaptor cable. Only modest soldering experience and DIY skills are required and all the parts are available from specialist retailers or online marketplaces. Please note, though, that this is not intended as a step‑by‑step constructional guide, and while the information in this article has been carefully researched it is used entirely at your own risk — neither SOS Publications Ltd nor the author can accept any responsibility whatsoever for misprints, void warranties, or any harm to equipment or persons!

Although it’s virtually the modern standard Leslie interface, I’ve been unable to find a ready‑made adaptor cable for the 11‑pin format used on models such as Suzuki‑Hammond’s old XK3, the new XK5, the SKX and the SK‑Pro models, as well as almost all of the popular clone organs including Viscount’s Legend organ range, Nord’s C‑series organs, Crumar’s Mojos, and many more. So this article will concentrate on the requirements for this adaptor. Hammond already offer a ready‑made adaptor cable to connect a Ventilator II pedal to the 8‑pin DIN Leslie connector found on the popular (but no longer available) Suzuki‑Hammond SK1, SK2 and XK1‑c stage organs, but if you’d like to make your own I’ve included the wiring details in the ‘8‑Pin DIN Leslie Interface’ box.

Leslie Connection Overview

As I said earlier, an organ with a built‑in Leslie emulation needs to know if an external Leslie speaker system has been connected so that it can: (a) disable and bypass its internal Leslie simulator; (b) route the organ’s Leslie speed switching to control the external Leslie; and (c) in most cases also route the organ sounds via the Leslie connector instead of the normal line‑out connectors. This ‘Leslie present’ information is conveyed in different ways for the 8‑pin DIN and 11‑pin Amphenol connections, but it’s obviously critical that we replicate this feature for correct operation with the Ventilator II pedal.

While all Leslies accept a mono organ input signal to the Rotary speaker channel, many models also accept one or two extra line inputs to feed Stationary channels — fixed speakers typically used to reproduce non‑organ sounds. For example, many stage Hammond organs include extra voices like electric pianos, choirs, strings and so on, and those aren’t normally routed through the rotary speakers. So most stage organs provide two options for these extra voices: (a)...

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