Optogate PB-05 & PB-07

Someone famous once said that technology only advances when there’s a problem to be solved, and one very common issue with live sound is the ‘open mic’. I’m not talking about the ‘bring-your-own-guitar-and-beard’ type of open mic, but the one on a live stage that is necessary but doesn’t need to be used for the whole show, or where the user — be it singer or instrumentalist — tends to step away from the mic during their performance.

The Optogate uses a different approach, in that it is triggered by the physical presence or absence of the mic user. The PB-05 has a miniature infrared transmitter and receiver, which detects reflected IR from a person or instrument directly in front and noiselessly switches the signal from the mic on and off accordingly. The PB-05 is built into a small metal case, slightly smaller than a common-or-garden matchbox, and it incorporates a female XLR on one end and a male on the other. Another way of describing it would be as an XLR ‘through’ adaptor with a little square extension on the side. It mounts directly to the end of the microphone, and the mic lead plugs into the output connector. The end of the device facing the performer — the female (input) XLR end — houses the infrared transmitter and receiver LEDs, and a discreet red LED indicates that the PB-05 is switched on (ie. allowing the signal to pass through).

A small multi-turn potentiometer inside the Optogate — accessed via a tiny hole in the casing, so a very small screwdriver is required — is used to set the range at which it will react to an object. Turning it all the way anti-clockwise will set it to the shortest range, which is a few centimetres, and the longest range it will reliably work at is 120cm. The range also depends on the reflective properties of the ‘target’ — the Milk Tray guy would probably have to be a bit closer, whereas someone dressed in a silver suit and boots should do more reflecting.

An obvious application for the PB-05 on a live sound stage is the horn section, who don’t play all the time (at least the ones in my band don’t), and they tend to move away from their mics when they have nothing much to do. I was road testing some speakers with a function band who just happened to have a sax player, who also happened to spend some numbers on keyboards or hitting a tambourine — a perfect test! As the PB-05 is so small and light, it doesn’t really affect the mic position or balance at all and it’s hardly noticeable from a few feet away. I set it up by playing a few bars of air sax, and I was impressed by the fast and consistent response as indicated by the little red LED. Having got over the ‘Look at this — isn’t it clever how it does that?’ phase, the band got on with their soundcheck and the proper sax player, Laura, got on the mic for real.

As with any brilliant idea, though, there are a couple of limitations. The aforementioned remark about what the performer is wearing is a real issue, but easily overcome, and I didn’t find this a problem at all on short-range settings, even in my boring black shirt. It’s always going to be difficult if the player/singer moves around a lot when they are actually using the mic, but singing or playing at a stage mic from more than a metre away is pretty unlikely anyway. More of a problem might arise from ambient lighting — either stage lights or direct sunlight — and the user guide does warn about this (it even invites you to try an experiment with your home hi-fi remote!). But again it should be relatively easy to position mics away from direct bright lights or infrared sources.

If mounting the Optogate directly on the back of the microphone isn’t practical, there’s another model called PB-07, which comes with a plastic clip for attaching directly to a mic stand so that the Optogate sits vertically. On this model, the infrared TX and RX lenses are on the flat panel, so the unit is positioned facing the performer and can be completely hidden from the audience — just another option, which may be useful in TV or video applications, or when miking up orchestras where space is at a premium. On the version sent to me, the PB-07 wasn’t equipped with the manual on/gate switch and I was quite happy to use the PB-05 model.

After using the Optogate on just one gig, I reckon it is an extremely useful device, and it is now in my ‘almost essential’ category of live sound accessories. It’s clever, it’s neat, it’s a real problem solver, and it actually works. The Optogate is most definitely on my Christmas and birthday lists, and I think the dog wants one too...  0