REDGUM RGi120ENR integrated amplifier review


Luke Skywalker [on seeing the Millenium Falcon for the first time]: What a piece of junk!

Han Solo: She’ll make point five past lightspeed. She may not look like much, but she’s got it where it counts, kid. I’ve made a lot of special modifications myself.

Many hi-fi buffs agree that changing speakers yields the most dramatic sonic shifts within a system. Yet in my direct experience it is the amplifier that determines their long-term viability. An audiophile’s ability to play the long game might possibly be found in the pairing of a luxury amplifier with budget speakers – conventional wisdom be damned. The amplifier is the anchor that moors the speakers’ boat when habourside. Go on, ask yourself how many speakers have you mistakenly dismissed out of hand due to poor amplification choices? Let’s draw on a culinary analogy: the speakers provide the flavour but it is the amplifier that provides the nourishment.

REDGUM Audio are resolutely Australian.  They’re resolute about their hand-built amplifier design principles:  neutrality from MOSFETs, dual mono volume attenuation and high current delivery.  Each unit is brought to life in their Dandenong-based workshop.  It’s obvious that Ian Robinson (designer) and Lindy Gerber (marketeer) pride themselves on their ongoing difference (quirkiness?) when sat next to the more traditional black-boxers.  The Redgum-panelled front, the key and the dual volume pots are common to the fascias of the integrated range: RGi35 (AU$1190), RGi60 (AU$1990) and RGi120 (AU$2990).

“Ian R”.  Say it out loud.  “ENR”.  Now say that out loud.  Ya get me?  Ian Robinson’s statement REDGUM integrated amplifier sees an ENR appendage as a sign of Signature Series categorisation – cooling fan be gone, come on in SignWave heatsink.  The RGi120ENR (AU$3990) runs top flight in the REDGUM integrated stack.

Let’s talk. The email exchange between reviewer and manufacturer’s marketing manager can often be a slightly staid affair.  REDGUM – again – run with difference in their hearts.  Lindy Gerber is prolific (and in-depth) in her responses.  Gerber rarely falls back on (previously-penned) marketing spiel.  A Q&A to&fro eventually morphed into something more extensive:

JD:  What is the difference between the RGi120 and the RGi120ENR?

LG:  “The short answer is (as Ian puts it) “Well, if you’d really like some grunt …!?” which is in the REDGUM content of never being grunt-free, not even our baby RGi35. The standard RGi120 is now the only unit in the complete range with a fan.  The RGi120ENR adds external SignWave heatsink and removes the fan.  Though some malign any need for a fan in an amplifier, its circuitry has a very smart way of bringing it into play with a soft-start – a response to circumstances rather than an on/off situation. [The fan speed in a RGi120 is adjusted by a sensor which measures the output stage temperature i.e. no heat, no fan. When it starts to run, it gradually increases its speed as the temperature builds up to the level definitely requiring a fan. (This would be the temperature at which other many brands’ products would normally have a fan “kicking in” quite abruptly as it aims at its top speed immediately.) In this way, because of the REDGUM fan circuit, its entry (and exit) is far less intrusive, should it be needed. As so many surprised customers have said when told about this feature, “What fan?” ! In other words, they are unaware that their units actually have a fan until they run their amplifier hard for quite a while, and then a section of loud music stops suddenly revealing that the fan is functioning. The temperature drop over this time period is very rapid and the intrusion should not last more than a second or so.]”

JD:  Tell us about the SignWave heatsink…

LG:  “Once the fan became standard in the RGi120 (mid/late 90’s) it has remained a standard feature and will do so as long as the demand remains for that particular power in an integrated. Bless those REDGUM customers who still love our very first design, the RGi120, for what the concept includes which they deem still valid after all these years. The very, very first one was built in 1993!

Actually for the early years, the fan was used further up the (limited) range in the monoblocks whilst the heat-sinking remained internal. Once the monoblocks delivered even higher power (whilst the model denominations remained the same), they then moved to external heatsinks, so there was, of course, no need for a fan. And so they all have remained for some years now.

For those requiring greater heat dissipation (re those low impedance drivers), the fanless RGi120ENR (with its SignWave heatsink forming the total base) is firmly in the integrated range for that purpose. The same heat sink is used for the Signature Series ENR monoblock models, and rear heatsinking on the base monoblock models.

Dual Mono – manual vs remote.  The Single Volume versions (denoted with the letter ‘s’ after the model) are no longer available.  At the time of purchase, the customer can opt for standard face-plate pots – which means manual volume control of each channel individually – or the world’s only remote control where both channels can be changed separately, OR simultaneously.  For the latter, the remote control iteration overtakes the need for any customer to get their head around dealing with two volume controls to create one sound level, locking in the two channels electronically to within 0.1 dB of each other, which is far better than any ear can do.  However, if preferred, the controls need not be moved at the same time, instead a simple sequential adjustment of the channels to get the required imaging.”

Remote decision.  Once into remote control territory, there is no manual switching of inputs – it’s all in the wizard wand.  Should you lose BOTH remote controls that ship with amplifier, the manual describes an (emergency) Lost Remote Mode…so that music can continue to flow.

JD:  The remote control – it’s a bit cheap/plasticky, innit?

LG:  “Whilst offering plenty of smarts (i.e. a menu system of Options to personalise settings), our choice of a simple, small credit card remote was considered to be basically a carrier of codes rather than the World’s Best remote supplied with the World’s Best amplifier! 😉 With customers reporting having up to 12 remotes, REDGUM providing yet another one was clearly superfluous!! And so we did not waste their money/increase the purchase price by providing a classy one when they were likely to have already moved to a Universal “one to rule them all”. Should that not be the case, we do offer a Touch Screen Universal remote control, backlit for night time operation already pre-programmed with REDGUM codes.”

JD:  Dual Mono seems to be something from which you guys just don’t/won’t budge?  I assume a non-remote control version of the RGi120ENR is available?  One where manual volume attenuation and manual switching between inputs is possible?

LG: “From the audio purist standpoint we still prefer to stay in a remote-free zone offering fully analogue amplifiers, just as we have rigidly maintained the Dual Mono stance for 17 years (since 1994)!

From our point of view, if you want 100% sound quality plus that extra musicality [that is special to a live performance], you need the extra information allowed through by our manual Dual Mono volume controls. Why? Because to get the best sound quality, it is necessary to use audiophile-quality conductive plastic potentiometers, as we do for our standard/non-Remote Control versions. No manufacturer offering remote control uses these quality pots! […because it is impossible to do so for a remote-controlled unit needing motorised pots.]

Finally, because our circuit design is very simple (apart from its modular nature), the added advantage of using these plastic potentiometers (in manual/non-remote units) is their long life as a component. They are less likely to fail by a factor of many hundreds [over digital components].

Okay, in reverse, the question must be asked … whilst having Dual Mono control over the channel volumes via the remote, is listening to a remote-controlled REDGUM less of a musical event due to the lack of those plastic pots? We leave those decisions up to customers.  From our experience having the Dual Mono controls as part of a remote grabs the image so much better and to greater satisfaction (for subtle adjustment), that the issue of which pot is used does not enter the discussion.

Perhaps that is just reflecting how the rest of the REDGUM design supports it.  Either way, we are happy in the knowledge that the remote-free purists can know they have added another step towards that famous “last iota”.

Our complete range of amplifiers has a foot in both camps and so our customers can choose whether to have remote control or not.  In this modern world of convenience, why do we consider the remote feature an option? Simply from the point of view that the further you stay away from digital electronics, the lower your chances of misbehaviour of those electronics. In short, a longer life from your investment when it is an analogue build.

Naturally, once added, we have taken care of the sound quality that “digital” can give a bad name to.  As well, the individual digital components have been chosen so as to minimise the effect of those typical characteristics. For example, to minimise digital noise, our remote control uses a slow-op microprocessor. [Design Cross-reference: This parallels our use of a soft-start circuit for the fan in our RGi120’s.]

As a starting point for the practicality of such a remote-free stance … so many of our customers mention that they basically never want/need to use a remote for their amplifier. Regardless, when required in a product, the way the remote control pre-amp is incorporated as a separate module minimises the intrusion of those digital electronics as they remain separate from all the other analogue modules that together make up the complete amplifier circuit.  Come the time for a check-up or upgrade to remote, there can be none of those one-piece rat’s nest circuit board hassles found in mainstream products that the customer ends up paying for! 

So this modular design/build of REDGUM amplifiers also makes for a simple retrofit process (for most earlier units), costing $360, versus $275 when requested at the time of ordering the product. [Cross-reference: the customer having this choice to pay for what they will use parallels our lack of inclusion of Phonostages into our amplifiers (which is apart from the very important technical reasons why it is a disaster to do so from the customer’s ear’s point of view!)”

Total commitment to MOSFETs – that’s REDGUM’s starting point for all of its amplifier designs.  According to Gerber, there were many circuits devised from the original Hitachi MOSFET circuit, but only one remained reliable.

JD:  So why MOSFETs?

LG: “Just being a very clever concept from way back isn’t enough to make MOSFETs a PR plus these days. Being hundreds of times the cost of transistors sounds more like a brag for its own sake.

No valves + no transistors = ? So what is left to use when the most frequently used components are considered not reliable enough? Is there a device that has the advantages of both, but none of these disadvantages? Mix the concepts and you have a solid-state valve that is a special form of transistor – a MOSFET (Metal-Oxide doped Silicon Field Effect Transistor). MOSFETs have a positive temperature coefficient which protects the circuit from damage – they are self-limiting because thermal runaway cannot occur. 

When the original output MOSFETs were developed in 1975, one MOSFET was roughly equivalent to sixteen 2A3 valves in parallel push-pull class AB1. Substantial improvements have been made since then. Today’s MOSFETs have the advantage of the low internal impedance of a transistor without its thermal instability and the advantage of being voltage-driven like a valve without a high internal impedance. This combination gives a stable platform on which to build better quality sound. How to enjoy listening to Wagner without fear of your amplifier’s self-immolation.

Speaking of which, a customer returned a RGi120 saying it was working but didn’t sound right … “A bit rough in the right channel!”.  The cover of the unit was lifted to an extraordinary sight. Three metal MOSFETs had been heated to such a degree that though their zinc coatings had all oxidised, they were still working. The fourth ‘FET was heated to the point where the coating had actually melted and (sitting on a sloping shelf) had run down to one end. This ‘FET was still working but in open circuit, hence the rough sound. In other words, the REDGUM, though officially dead,  was still very alive and kicking. Ian estimated those MOSFETs must have been running up to 500 degrees C and so would have been glowing red! No wonder the REDGUM sounded a bit rough. In short, what seemed like an amp with a problem was actually validation of how tough these MOSFETs are. Robust – always the word for me that comes to mind for MOSFETs.

What is it about the sound (or lack thereof) of a MOSFET in REDGUM’s designs? Amplifier designers do seem capable of imbuing a certain characteristic sound … like many English amps famous for their smoothness and politeness.

There is only one design criteria that holds any value at REDGUM: how accurate is the reproduction when compared to the original performance? To assess this, one needs to have the live experience of the sound of instruments/voices/performances (all part of the testing process at REDGUM) and how they are affected by venues/etc. Our ears are important! They pick up/hear what would not be discernible from studying signals on a CRO. In this business, hearing is believing.  What should come through is the excitement of the performance. It must be palpable, and, an even bigger ask, the excitement must be there every time you listen to the recording.

An effective amplifier design should not leave its mark on the sound. So, if a REDGUM adds anything to the pleasure of listening it is because we aim to add nothing. The neutrality of the REDGUM sound remains a point of distinction for us.”

Blast-off. Firing her up via the rear-switch, a downward-firing blue light let’s us know we have action.  An R2-D2 P.O.S.T. kicks things into gear.

JD:  The beep-burp start up process – what on earth is going on in there?

LG: “1.  Single beep – indicates power-on at processor. 2.  Rising tone – processor firmware checks out OK. 3.  Series of single beeps (currently 7) indicating the firmware version. 4.  Processor then checks current position of volume controls – if more than 1/2 way up, it brings them down individually, left channel first. 5.  Processor checks operation of all relays and with a series of audible clicks, cycles them to prevent ‘contact ageing’. 6.  Low tone – high tone (ta da!) – all checks completed, ready for power-up.  This processor intercepts the InfraRed control commands, controls the input selector, volume control positions, muting (which is partial), etc.

At the same time all this is is going on, the power supply/protection board is also booting up.  This makes no noise, but the firmware version is indicated by the number of blinks of the blue LED (currently 3).  This processor monitors the heat sink temperatures, and controls the mains power relay.  As the heat sink approaches high temperatures, this processor initiates the fan (RGi120 model ONLY) and slowly ramps up the fan speed to match the heat input.  If the heat sink temperature continues to rise, the blue LED will begin blinking (as a warning).

If the temperature passes a critical limit, the processor shuts off the power to the main amplifier to protect it from damage.  Both of these processors are very simple, low speed devices, with their own dedicated power supplies, heavily damped and bypassed to minimise any digital noise transfer into the audio paths. (This noise is currently unmeasurable, and sonically below the extremely low ‘noise floor’ of the amplifier.)”

Enough talk, let’s listen. Starting with Zu Omen and switching out the more polite Peachtree iNova for the beastly Aussie facilitated an immediate upwards gear shift with momentum and propulsion.  The scale of reproduction also moves up several notches (think am-dram to Shakespeare Theatre Company) and imaging tightens.  The musical carving is sunk into the wood with deeper etched lines, greater inward-outward pressure and – crucially for those that are solid state all the way – higher resolution. At the heart of its modus operandi as an emotional communicator is the REDGUM’s ability with low frequency data mining.  We witness heft and physicality without body-builder muscularity.  It’s amplification that plays straight down the line with neutrality and power.   This is the not the same as the accuracy-as-a-feeling communicated by Audio-gd’s pre-power slabs;  it’s a neutrality with equal transparency but softer edges.  Audio-gd remains hospital-grade clean, the REDGUM old-fashioned house-proud.

In going so deep, The REDGUM is able to anchor the listener deeper into song.  Rock solid instrumental placement and lockdown comes as an (expected) side plate.  The Black Dog’s dysoptian techno emerges from the shadows.  Strike that – ALL music emerges from the shadows, most notably at lower volume levels when in Zu country.  My listening notes – word association by any other name – of an afternoon with the most recent Wish You Were Here remaster read: “weight, presence, body, DENSITY”.  The REDGUM ‘does’ (because there is no try).

vs. Leben EL84s.  Few artists unleash the potential of slow-burn on their recordings as well as Peter Gabriel. I pulled his 1983 album Security (PG4 for those readers outside of the USA) from the imaginary digital shelf.  Opener “The Rhythm Of The Heat”‘s initial tribal pulse builds toward something far more ominous until a cacophony of percussion brings the song to a tight-clipped full-stop. I compared the RGi120ENR’s version of Peter Gabriel’s events with that of a Leben CS300XS.  Hardly like for like in topology or ideology, but close enough in asking price. (This limited edition version of the Leben integrated will run you AU$3495).

The Leben converses with more impressionistic terminology – more finesse, flair and vapour trail.  The REDGUM, more the straight talker, better drives home the endgame percussive drama to unravel the Escher-ian nightmare within.  It offers more weight and overall drama.  There’s that bass depth again. The tubular integrated is too delicate to withstand the pressures of deeper hertz.  Given the Leben is packing far fewer watts per channel – and likely has a lower damping factor –  this is hardly an outrageous or controversial conclusion. The Leben is small-town charm compared to REDGUM’s big city lights.  The Leben paints, the REDGUM sculpts.

Said small town vs big city differences become more noticeable when subbing loudspeakers: out go the Zu Omen and in come the more power-hungry ProAc TR8, with which the REDGUM is so downright effusive that I find myself compelled to defend the Leben amplifier at this juncture: it has a way with seduction (that doesn’t descend into a come hither lap dance) and when partnered with more efficient loads it can offer up magical moments that are tough to replicate in the solid state ‘hood.  At everyday listening volumes, one would find it tough to point out the Japanese fella’s diminished power rating – bass ain’t loose or hung over.  It is only when SPLs are pushed higher and higher that the REDGUM keeps giving and giving and giving (long after the EL84 quad show hints of vocal chord strain).

For larger listening rooms, I’d run with the Australian every time.  Its stability with clarity AT VOLUME can creep up on you – how did it get so loud without anyone complaining?  The power quotient of 155 big ones endlessly furnishes us with detail AND delicacy, particularly from standmount loudspeakers loads that burn wpc fuel.  I rarely took the volume pots past halfway for a sound that – according to the Decibel iPhone app – went into the upper nineties without ever needing to shout out loud.

vs. Rega Brior-R.  Next to bulkier Australian, the Rega is contrasted as leaner, silvery and more ‘spirited’.  Sure, the Rega is a near-definitive performer in its own price-weight class but the REDGUM sounds more accomplished:  playing back-to-back Editors, the Rega’s take is lighter on impact/slam and not as deep in staging.

Back again to the remastered PG4 – Peter Gabriel’s early work is never short on its sinister and paranoid moments.  The REDGUM delivers us through open windows into the song’s claustrophobic drama, offering insight into the individual machinations that hold the song together.  More power brings more muscle and instrumental body; no need for the lard of tubes.  Hooking back in the the Brior-R, the listener’s face is pushed up against the glass: we can see into the netherworld but we don’t get to walk/swim IN it.  Think of the Rega as the bathysphere and the REDGUM as the full scuba-diving monty.

Whilst we’re in the water, the Rega comes at us as speed boat.  The snappy twists and turns of Foals’ indie-rock-tastic “Blue Blood” turns guitar-hook-left – then drum-snap-right – on a dime.  Both possess the requisite speed but the the Rega has to shout louder to be heard. The REDGUM is more ocean liner; where speed appears more effortless/graceful; a larger propellor carves deeper waters.  Crucially, it has the power to go LOUDER without shouting.  Two words to nail it down?  Smooth, majestic.

Bucking conventional wisdom that the majority of system dollars should land on the loudspeaker purchase, one could easily make a case for partnering this integrated with a $500-1000 standmount (Usher S-520 being a prime candidate) over and above spending $2-3k on a more luxurious speaker and then (possibly) finding it lacking long-term engagement when mated with a similarly-stickered amplifier.  That lack of nourishment is what keeps people churning through gear.  Consider yourself alerted, but not alarmed.

Let’s exemplify.  During 2010, I was twice extended a home demo of Spendor SA1.  The SA1 are very strong performers in mid-range clarity, but not quite as dynamic or as crisp-fried up-top as my ProAc Tablette Reference 8s.  The latter bring the zing.  The SA1 run with refinement and greater politeness.  Yet, twice I failed to solicit the requisite joy that a (close to) AU$3K promised.  They got close, but no cigar.  Twice I returned them with embarrassment and thanks to the local distributor, the very accommodating Andrew Hutchinson at Audiofix in Queensland.  It wasn’t the loudspeakers at fault but my amplifier choices – a Naim Nait 5i and an Aaron XX – that had come up just shy of the mark to justify this more exotic standmount (spend).

Christmas 2011.  An audiophile friend lent me his own pair of Spendor SA1.  Third time’s a charm then…but only via the REDGUM RGi120ENR.  The Rega Brio-R replicated only what I’d witnessed a year earlier: a great loudspeaker that niggled with its something-missing-this-way-comes train ride.  Great loudspeakers demand even better amplifiers.  In consumer parlance, that means spilling more than a grand on amplification for three grand standmounts.  (This half-box Rega best maximises your Epos or your Ushers or your Wharfedales).  REDGUM/Spendor is pure luxury indulgence, the former properly nourishing the latter.  REDGUM extends the bass, ups the midrange transparency, deepens the soundstage and drags more breathing room (air) from the upper frequency floors.  Wonderful.

[Cable trainspotters should note that I eventually switched out my budget Grave Science speaker cable for something more RRP-appropriate from Norway; with which these speakers and this amplifier are dealt a further dose of pebble smoothing and water purification from the purple-tipped Skogrand SC. I don’t review cables but Knut’s Skogrand SC are deserving of a plug here.  They are the epitome of silk-sheet luxury].

High current, high damping factor, unique styling, stoic adherence to the dual mono model – all principles that form the backbone of REDGUM design philosophy.  At AU$4K, we’re nudging high-end territory.  With sheer drive and intergalactic propulsion speaker matching is a cinch.  There’s nothing I could find whose intrinsic characteristics weren’t maximised by the RGi120ENR’s guile:  ProAc, Zu, Spendor, Epos, TBI, Usher.  This warhorse upped inner illumination and added weight and impact to each and every pair.  Good news then for those set on standmounts wanting to the juice the very last from their transducer fruit. That’s nourishment at work in one’s system.  Sonically such vitamins and minerals translate to an organic elegance and immersive tonal colour.  The RGi120ENR might appear somewhat leftfield on the aesthetics front, but she’s got it where it counts – you really do get the power and refinement you pay for.  She’s the Millennium Falcon of integrated amplifiers: as Han Solo famously once said: “She’s the ship that made the Kessel Run in less than twelve parsecs. It’ll outrun Imperial starships…she’s fast enough for you old man.”

Remarking that REDGUM amplifiers look unusual is akin to describing the Mona Lisa’s smile as enigmatic – it lacks imagination. Instead, let’s run conclude with one last Star Wars analogy: REDGUM’s top integrated amplifier possesses extensive Midi-chlorian punch; The Force is strong within this one.


Associated Equipment

  • MacMini 2010
  • Audiophilleo2
  • PSAudio PerfectWave DAC
  • Rega Brio-R
  • Leben CS300XS
  • Peachtree iNova
  • Spendor SA1
  • ProAc Tablette Reference 8
  • Epos ELS8
  • Usher S-520
  • Zu Omen

Audition Music

  • Peter Gabriel – PG4/Security (1983)
  • Foals – Total Life Forever (2010)
  • Nicholas Jaar – Don’t Break My Love (2011)
  • Editors – The Back Room (2005)
  • The Black Dog – Liber Chaos (2011)
  • Pink Floyd – Wish You Were Here (2011 Remaster)
  • The Chap – Well Done Europe (2010)
  • Deepchord presents Echospace – Spatialdimension (2011)

Further Information

Written by John H. Darko

John lives in the NOW + HERE = NOWHERE. He derives an income from the ad revenues of DAR. John is also an occasional staff writer for Stereophile, 6moons and TONEAudio.

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