It’s traditional to give a key for a 21st birthday, and since this is Redgum’s 21st anniversary year, a key would be particularly appropriate because for all those years Redgum owners have had to use a key to turn their amplifiers on and off.

A key would also be appropriate because Redgum’s founder, co-owner (with Lindy Gerber) and chief designer, Ian Robinson, as well as being an electronics engineer and an audiophile who’s passionately involved in music, is as passionate about cars as he is about audio. The last time I interviewed him, he gave me a lift back to my hotel in his Porsche 911S. During that trip the speedo rarely dropped below 100, yet Robinson thought I was gripping the seat because the ride was so bumpy. ‘Sorry about the suspension,’ he said, ‘but this is the same car I race on weekends, so the suspension’s a bit stiff for street work.’

This time around, when I decided to interview him about the occasion of Redgum’s 21st birthday year, I decided not to risk another terrifyingly fast ride and instead interviewed Ian and Lindy via telephone, a very safe 878 kilometres away from his latest and even faster Porsche Boxter…

Greg Borrowman: Redgum may have just turned 21 but I know that you’ve been in the audio industry for a lot longer than that. What were you doing prior to establishing Redgum?

Ian Robinson: My first business venture was Chelsound Electronics, a company I started in 1963. I mostly fixed car radios and television sets, but I remember that my business card read ‘Repairs, Installation and Service of all electronic equipment.’ While at Chelsound I started building speakers for John Barbuto—who founded JB Hi-Fi—and also for Ben Douglas, of Douglas Trading. I had been working at the Victorian State Electricity Commission with Ralph Bridges, who owned a company called Claybridge PA Systems. He asked me to make his PA cabinets for him, so I went into a partnership in a company called Recab Storage Cabinets with Ted Mather, who was the Australian distributor for Goodmans and also wanted cabinets. I’d met Ted when he introduced me to hi-fi by way of selling me a Truvox reel-to-reel machine. It was at that time I started designing and building loudspeakers that were sold under the Link brand.

GB: Then you made a move into hi-fi retailing, first opening Contemporary Sound Centre at Beaumaris in 1972 but then moving the store to Hawthorn in 1976…

IR: I only got into hi-fi retailing by accident. I had been supplying speakers to a store in Beaumaris that owed me so much money—actually enough to buy a house at the time—that I suggested he might like to hand over the keys to his shop. He did, and that was how I ended up in retail.

 GB: But unlike most hi-fi retailers, you did all the store’s amplifier and speaker repairs yourself, plus you were also acting as a service agent for Zephyr Products, which at the time was importing Perreaux amplifiers from New Zealand. How did that come about?

IR: Perreaux was one of the few amplifier manufacturers using MOSFETS and Zephyr needed someone experienced to work on them. Over the years I had a lot of exposure to MOSFETs. You know that they’re virtually indestructible don’t you? I once did a call-out to a recording studio only to discover a MOSFET amp that had been running into a short-circuit for five years. I removed the short and despite the device casings having turned a dark shade of gray, the amplifier was fine. It was because of my experiences with the sound quality, performance and reliability of MOSFETS back then that when I came to design my own amplifier I elected to use them as output devices.

 GB: So what was it that spurred you to design your own amplifier in the first place?

IR: Again, it was totally by accident. I had four repair technicians working for me at Contemporary Sound Centre by then. When a particularly well-known and very expensive English amplifier came in one day, and I saw the components that were being used in it—and how poorly it had been put together—I first said something fairly rude, then that I could build an amp that was a whole lot better. The techs challenged me to do exactly that, and that was how Redgum got started…

 GB: So we know why you decided to use MOSFETs rather than conventional bipolar transistors, but how did you arrive at the overall circuit topology?

IR: Basically, I Goldilocksed it.

GB: And what, exactly, is ‘Goldilocksing?’

IR: It’s a technique named after Goldilocks in the fairy tale, where she tries one porridge and finds it’s too hot, then tries another that she finds is too cold before she finds one that’s ‘just right.’ I drew up a circuit I thought would work, built it, then went through and fine-tuned it by experimenting with the value of every component to get the best sound. For example I’d take the 0.47Ω drain resistor and first make it higher, then lower, or even zero, until it sounded right. This is why we now use 0.03Ω emitter resistors in the drain. I did this for all the components in the circuit: ran ‘em up and ran ‘em down until I found the value that was ‘just right’.

 GB: That seems like a very time-intensive approach to amplifier design…

IR: It sure is! It meant that I had to go back to the shop every night for three years to work on it… usually until well past midnight. It was a long and exhausting process, not least because I made sure that the amplifier sounded good not with one pair of speakers, but with three different models, a pair of Rogers LS3/5As, a pair of John Reilly’s Axis loudspeakers and a pair of Goodmans. Despite the work—and the time—involved, I actually found the entire process very enjoyable.

 GB: And that amplifier became… which Redgum model?

IR: None of them. I named it after the initials of the store: CSC... and the model was the ‘Enduro’—at least that was what I’d etched onto the printed circuit board. The name didn’t become Redgum until 1993 when I built the first one with a front panel made from Redgum. And although that was the first time the name appeared on an amplifier, I didn’t actually incorporate Redgum as a company until 1995, about the same time Lindy signed on as Promotions Manager. We were making enough amplifiers to have a healthy manufacturing business, so we closed down the retail shop in 1996 and leased a factory in Box Hill where Lindy and I and half-a-dozen employees all hand-stuffed circuit boards and bent metal for chassis until we saw the light and realised it was better to subcontract the PCBs and chassis out, leaving us to do only the final assembly. We were doing serious business at that time, exporting to twenty-six countries. Our distributor in Malaysia, which was our biggest market, was ordering around 35 to 40 amplifiers every week.

 GB: So is Malaysia still your biggest export market?

IR: No. In fact, since the Malaysian meltdown we haven’t shipped a single amplifier there. Our biggest export markets are now North America, the United Kingdom and Russia.

 GB: You were one of the first hi-fi manufacturers to get into crowd-funding. What was the reason?

IR: We discovered we could cut the manufacturing cost of our sine-wave heat sinks by switching to real mass-production, but the up-front costs were enormous. Lindy and I had seen crowd-funding work in other situations, so we thought there was no reason it shouldn’t work for audio. We investigated lots of crowd-funding outfits and eventually decided to go with Indiegogo. It was really successful and in the end, by pre-selling the RGi35 on Indiegogo we were able to fund the first production run of heat-sinks as well as pay for the cost of the die itself.

 GB: Since you’ve mentioned your unique sine-wave heat sink, now would be a good time to ask something I’ve always wondered about, which is why it’s underneath the amplifier, rather than on the sides or back, which is where most other amplifier manufacturers tend to put them.

IR: You’re right, it’s not a logical place to put a heatsink because the fins dissipate heat most efficiently when they’re vertically orientated, but ours is so big that it doesn’t need a lot of air-flow to keep it cool, and the back of the sink acts as the base for the amplifier itself, making the chassis absolutely rock-solid. You’ll find that even when you’re driving the amplifier really hard into low impedance loads the metal never gets warmer than blood temperature. Because the area of the sink is overkill to the nth degree, it’s fine. Also, I like the look!

 GB: Although the Amplifolia Series amplifiers are made here in Australia, the ‘Black’ Series amps are all made in China. Why China rather than, say, Taiwan, which buildings amplifiers for many high-end manufacturers?

IR: That’s a very good question, and the answer is that because John Reilly is a friend of mine who lives in China for six months a year and builds his Axis loudspeakers over there, I already had great contact in China. We now own a four-storey office/factory building in Shenzhen where both Axis speakers and the Black Series amplifiers are now made. I regularly fly over to personally test every amplifier before it’s packed for shipping and usually manage to QC around 40 a day while I’m there.

 GB: That would seem to have it covered. Do you have any other quality control procedures in place for the Chinese operation?

IR: Several. The first is that because we have our own factory, we have total direct control over manufacturing. Second is that all the PCBs—which I do have made in Taiwan, by the way—are shipped direct to me here in Australia, so I can install and program the PIC [Programmable Interface Controller] that controls the input selector and also solder in the MOSFETs that I buy direct from Exacon in England… they’re the same ones used by Halcro. After that, I keep aside a number of the PCBs for use in the Amplifolia series amplifiers that Lindy and I assemble by hand here in Australia, and then take the others with me to China for installation in the Black Series amps.

 GB: So the PCBs in the three Chinese-made amps are identical to the PCBs in three of the models you build here in Australia?

IR: Yes, the RGi35ENR Signature is a clone of the Stellulata, the RGi60ENR Signature is a clone of the Aquilina, and the RGi120ENR is a clone of the Articulata.

 GB: But the amplifiers themselves look so different. How can they be clones?

IR: Externally they are different. The controls are mirror-imaged, the front panel displays are different and the heatsinks are different. But internally we use exactly the same components—the same resistors, the same capacitors, the same PCBs… in other words, electronically-speaking, they’re identical.

 GB: You’re one of the few manufacturers that can claim to make every component required to turn a compact disc into sound: the CD player, the DAC, the amplifiers and the speakers, as well as interconnects and speaker cables. Is this likely to change?

IR: Yep. We still have CD players available but we hardly ever sell one—it’s an old format now. So when stock runs out, that will be it. The DAC is a different problem. Cirrus Logic discontinued the IC I was using and I don’t think the replacement sounds as good as the original, even though it’s supposedly functionally identical.

 GB: But you’ll continue with the speaker cables?

IR: Yes, as loudspeaker impedances become ever-lower, using high quality, low-resistance speaker cable becomes ever-more important. If you have a speaker whose impedance drops to 2Ω and your speaker cable has a resistance of 1Ω—which is a typical figure for a 10-foot length of speaker cable—the cable will be absorbing a third of the power of the amplifier and the damping factor will only be 2, even if the amplifier’s impedance is infinitely low. Our Expressive Line speaker cable costs only $30 a metre, yet it has ten square mils of copper and a resistance of less than 0.0039Ω per metre!

 GB: You recently renamed all your Signature Series (ENR) models using words I find hard to pronounce, hard to remember, and even harder to spell, so I just have to ask that elephant-in-the-room question: Why?

Lindy Gerber: We decided to streamline our ENR range to consist of only three integrated amps and two monoblocs, instead of ten. Because all of them have front panels that are made of Australian Red Gum—which is a species of Eucalyptus—we chose to name the models after the botanical names for other species of Eucalyptus: Stellulata, Aquilina, Articulata, Splendens, Magnificata and so on. Even the name of the series itself—Amplifolia—is a Eucalypt species. Given the first three letters of that word we thought it was a particularly clever choice of name for the series!

 GB: I was told that your newest and most powerful amplifier, the Magnificata, impressed the hell out of the members of the Melbourne Audio Club when you demonstrated it to them.

IR: I really went all-out on the design of the Magnificata. I wanted to make a top-end flagship model that would cut the mustard no matter how large the room, or how difficult the speaker load, so I built it so that it will drive any load down to as low as a single ohm and deliver 900 watt per channel at the same time. It’s totally dual-mono, using twelve double-die 250-watt MOSFETs and has 100,000 microfarads of capacitance each side, along with dual 1kVA toroidal transformers. The energy storage is massive… close to 70 volts… in fact it’s so massive that I’ve had to put a relay in the speaker line… something I was initially loathe to do. And of course it has multiple sine-wave heatsinks.

 GB: Yet it still comes with that little card-like remote control you’ve supplied with all your products for many years now…

IR: Actually, I’ve just spent a sh… well… a lot of money on a new remote control app that works on almost all Android phones and will control all our products, including the Magnificata. The app went live in August and is a free download.

 GB: So the Magnificata still comes with the old remote then?

IR: Look, when we first decided to implement remote control on our amps, desktop-sized learning remotes were all the rage, so I thought there would be no point in us providing a really nice remote, because everyone would just code up their learning remote after which they’d put ours away in a drawer and never use it again. So I decided that since I was essentially only providing a code-carrier, I’d use a really simple remote and I have, quite literally, thousands of them in stock. So even though the Magnificata comes with that remote, I’d recommend you instead use the app to control it, not least because it’s a really fabulous app… you should really try it out!

 GB: I’m really pleased to see that despite all the changes, you’re continuing with that key in the front panel on the Amplifolia range, even though it no longer turns the amplifiers on and off. What was the original reason for that key anyway?

IR: I chose it for several reasons, but the one I liked the most was that using a keyed power switch gave me the opportunity to thumb my nose at the Australian Tax Office. At the time, Australia was one of the most difficult places in the world for local manufacturers to be competitive, because the government imposed a 32 per cent sales tax on almost everything, including 240V power switches. I discovered that because this particular keyed switch was intended for security applications, using it meant that I didn’t have to pay sales tax. So I did! # Interview by Greg Borrowman

This article original appeared in Australian Hi-Fi Magazine, Nov/Dec 2015 (Volume 46 No 6) and is reprinted here with permission.