REDGUM BLACK RGi35ENR Integrated Amplifier Review 
Home Theater Power Amplifiers Integrated Amplifiers
Written by Andre Marc   
Tuesday, 15 December 2015

REDGUM Audio has been producing beautiful looking and high value audiophile amplifiers in the state of Victoria, Australia for the past twenty-one years. REDGUM has never produced cookie cutter products. Their designs, as far as form factor and ergonomics are proudly off the beaten path, and probably because of this, they have loyal customer base.

My awareness of REDGUM comes from reading numerous overseas reviews, and speaking to a few local audiophiles who have been happily running Redgum amps for a number of years in various systems. Although REDGUM has international and North American distributors, I had not come across their products myself. That all changed when Marc Phillips of Colleen Cardas Imports contacted me about reviewing the new Black series of amplifiers. The Black series was designed to drive difficult speaker loads. I immediately agreed, as the timing was just right.

What made the REDGUM review offer so timely was that Marc understood that I was auditioning Magnepan speakers, which are widely known for being best paired with high powered and high current amplifiers. Marc promised the REDGUM Black amps would drive Maggies and any other speaker without breaking a sweat. I was eager to test this claim and a REDGUM Black RGi35ENR was soon dispatched. The Black RGi35ENR retails for $2500.

The Black series consists of three amplifiers. In addition to the RGi35ENR, there is the RGi60ENR, and RGi120ENR. The 60 and 120 offer the same circuit and design, but with more power, with the 120 being rated at 265 watts per channel into 4 Ohms, and an astonishing 500 watts per channel into 2 ohms. Amplifiers that offer ratings into 2 Ohms are rare indeed and that is one of the selling points of the Black series.

REDGUM, as noted, designs amplifiers that have unusual design features and employ the unique vision of designer Ian Robinson. Robinson is a musician and an electrical engineer by trade, with an extensive history in high performance audio. Robinson’s designs are not copycat products, but the result of decades of proven implementation. REDGUM beats to a different drummer with their wood faceplates used on their Amplifolia range, as well as keys required to power on the units! Other rather unique attributes such as dual volume controls as well as heatsinks positioned on the bottom of the amplifiers.

Here is Ian Robinson’s detailed reply to my request for an technical explanation for using heatsinks on the bottom of the amplifier:

“We often get asked as to why not have the fins on the sides or the back. Agreed, fins dissipate heat most efficiently when they are vertically orientated. But when you factor in the sheer size (as in surface area) of this heat sink, it then doesn't need such a lot of air flow to keep it cool. And the openness of the "sine" curve allows a generous clearance for air to convect through and up from the heat sink. In fact, with one of those "through" directions always being forward, this creates a real positive for dissipation when units are positioned in cabinets.


 

So, as the flat "back"/top surface of the heat sink then becomes the base of the amplifier, even driving low impedance loads long and hard means the metal never gets warmer than blood temperature. A case of because the area of the heat sink is "overkill" to the nth degree, the amp doesn't raise a sweat with the more difficult loads. This was the only technical test it needed to deliver on, so we knew after one long, hard session it had passed with flying colours! Along with being rock solid as a heat sink!

As implied, the initial impetus for this design was to meet the changing market urging the use of drivers with ever lower impedances. So that there was plenty of heat sinking to "future proof your system", it seemed only logical to re-design our bigger ENR versions (prior to the Black Series) to use a heat sink as the whole base plate of the amplifier.

REDGUMs are designed so that all circuits are efficient and that must include heat issues!! In fact, the very first REDGUM design had all MOSFETs mounted directly onto a thick metal plate bolted to the internal heat sink. (Within a few years, all MOSFETs were mounted directly onto that internal heat sink.) Then with the advent of the SignWave heat sink, an even more effective connection could be made as the MOSFETs of all Signature Series models were close coupled to the top/"back" of this immense surface. Also for the first time (in the industry?) we could use this heat sink to cool the mains transformer. And as to the rigid mounting of the transformer, it, too, is bolted directly to the casting.

Unsurprisingly, the heat dissipation is very effective on this "BBQ grill" (as it has been called!). As you would be only too aware, some Audio brands have heat sinks visually well placed, but actually with no heat-generating components mounted onto them directly!!!!!! I find that technically weird as naturally it is most ineffective. : (

Indeed, we have tried placing heat sinks where they are "meant to be"! Prior to this, we had interim models using heat sinks at the rear, or completely forming the sides of the amplifier (e.g. earlier models of our 6 channel Home Theatre power amp), but in comparison, that side coverage was only about two-thirds of the surface area the Sign Wave heat sink offers as a base.

Am sure the thought has crossed your mind that for the power of this "baby" Black Series amp you are testing, the amount of heat sinking is excessive. ; ) Indeed, yes, but, on the other hand, it really does come in handy for the rest of the Black Series ramping up to 244W/ch and 500W/ch into 2Ω. So it was decided when presenting a new series it made more sense to have one physical style. (It is always the customer who cops the cost of new model, so that is why the Black Series heat sink is the same design as for the Amplifolia range.)



For the last 10 years, the SignWave heat sink has been the visual hallmark of our larger ENR models in what is now called the Amplifolia range. As the Black Signature Series are clones of the Amplifolia designs, then having the same heat sink seemed to fit the visual logic. As the Black Series were focussing on providing the grunt for those more difficult loads, it made even more sense for the technical logic."


The RGi35NR comes with a remote control, which is full function, and is the only way to switch inputs. But not to worry, REDGUM supplies two remote units!! A few more technical points: The amp uses a passive input stage, and can be used as a power amp controlled by an external preamp if desired.

Out of the box I was very impressed with the build quality and casework. The large REDGUM logo across the top panel is a nice touch. Connectors and binding posts are of excellent quality. The amp is clearly designed to last, and REDGUM offers a seven year warranty, so they have  absolutely no reservations about reliability.

http://www.avrev.com/images/stories/equippoweramps/redgum/rgi35-rear.jpg


Set Up & Listening

I used the RGi35NR in two systems. In the main system, it drove both Magnepan .7 panels (on loan), and Bryston Mini Ts. Both are rated at 4 Ohm nominal and are not the easiest to drive, with the Magnepan being the more difficult load. Sources were a Bryston BDP-2 file player via USB into the iFI Micro iDSD DAC, and a Revox A77 reel to reel deck. Cabling was at first Acoustics Zen, Stager, and Transparent, then all ZenWave Audio (review in progress). The second system consisted of a SOtM server, iFi DAC, ZenWave cabling, and Magnepan MMG speakers. The MMGs are also difficult to drive.

The first thing you see when powering on the REDGUM is the entertaining “show” it puts on when the LED lights flash, and it makes an RD2 type sound. You will also notice the woofers on your speakers will gently pump, which according to REDGUM, is totally normal (they offer a technical explanation on their website). After that, simply select the input you want on the remote, set the volume, and sit back.

I played a huge variety of music of every genre throughout the two and a half months I had the REDGUM. Not once was I disappointed in the presentation. In fact, there was a purity to the sound that I have heard in very, very few integrated amps. The passive input stage makes a big difference in my opinion. The other factor is the absolutely dead quiet operation mechanically and sonically. Not a trace of noise can be heard through the speakers with no music playing and the volume maxed out.

I wanted to see what the REDGUM could put out, as this is one of the selling points. I cued up the Stone Temple Pilots classic No.4, in memory of the recent sad passing of lead singer Scott Weiland. Wholly smokes, these tracks came billowing out of the speakers with a rock solid foundation, gut thumping bass, and tremendously satisfying guitar crunch. Tracks like “Pruno”, and “Down” simply rocked, and the more layered tracks like “Sour Girl”, “I Got You”, and “Atlanta” had wonderful dimension.



I wanted to compare the 24/192 and DSD downloads of Shelby Lynne’s Just A Little Lovin’ for a while now, and when I did, the results were interesting. The REDGUM allowed me to hear precisely the difference in the two formats. The 24/192 version was “wetter”, with more recorded detail. It was easier to hear the reverb around her vocal, and the specifics of her distance from the microphone. The DSD was smooth, more tape like, sacrificing a bit it detail for a warmer, inviting sound. Having been a Shelby Lynne fan since 2000, I also highly recommend the new deluxe remastering of her “breakthrough” album I Am Shelby Lynne.

Switching gears completely, I pulled up some Dave Brubeck. The wonderful Concord On A Summer Night, 24/88 FLAC, is beautifully recorded and the playing is sublime. I did not expect such delicacy and finesse from the REDGUM. Silly me. Brubeck’s miraculous touch on the piano was intact, and I ended playing this album through multiple times.

Determined to see if the REDGUM amp had its limits in sophistication, I played Tinariwen’s new Live In Paris, 24/48 FLAC. The exotic stew of desert rhythms, modal blues, and syncopated percussion made it impossible to sit still. This album also showcased the amp’s way with bass, as notes stopped and started on a dime. Staying on a world music path, I pulled up several Dhafer Youseff albums. The sheer depth of beauty in his music is hard to describe. His blending of North African soul and modern flourishes are ravishing and the REDGUM presented a clean window into this artist and his vision.

One last listening note I can add is the harder I pushed the amp, the more it gripped the speakers. There was no loss of coherence at room overloading volumes. And at lower volumes, nothing was lost either. There was lots of usable volume range, something I don’t always see with integrated amps. No worries here.

Ergonomically, the RGi35NR was an absolute dream. II had it running for ten weeks, on 24/7, and not only did it not generate heat, it was cool to the touch, even on some warmer Southern California late fall days. This is proof that Ian Robinson’s design choices, although off the beaten path, are spot on. If I had one complaint, it is a rather petty one. I wish the remote was a bit bigger, for those with clumsy hands.

Conclusion


If you are shopping for an amplifier to drive just about any speaker, that offers world class sonics, stylish design, and superb build, the REDGUM Black series is a must audition. To be quite, frank, there is no integrated ump in the price range of the RGi35NR that I can recommend over it.

If you need even more power, there are two other models to choose from. If you are running Magnepan speakers, or similar, and have been dissatisfied with your current amplifier, REDGUM may have your solution.  An audition is highly recommended, without reservation.






Specifications



REDGUM Audio Black RGi35NR: $2500

www.redgumaudio.com

US Importer:

www.colleencardasimports.com

65+65 WRMS into 8Ω      
80+80 WRMS into 4Ω      
95+95 WRMS into 2Ω      
H 15 x W 41 x D 37 cm / H 6 x W 16 x D 14.5 in
16.5 kg / 36.4 lb shipped
7 Year Warranty

Review System 1


Server: Bryston BDP-2
DAC: iFI Micro iDSD w/ iFi Micro USB 3.0
Tape Deck: Revox A77
Server: Bryston BDP-2
Preamp: CIAudio PLC-1 MKII, Rogue RP-5
Amplifier: Audio Research VS55, Simaudio 760A
Speaker:  Bryston Mini T
Cables: Stager Sound, Acoustic Zen, Element Cable, DH Labs, iFi
Accessories: Symposium Rollerblocks and Svelte Shelves, Shakti Stone, Bryston BIT-15, Salamander rack

Review System 2


Music Server: SOtM sMS-100 w/ Battery XPS
Preamp: MicroZOTL 2.0
DAC: iFi Micro iDSD w/i iFi Micro iUSB 3.0
Power Amplifier: CLONES Audio 25p, Onkyo M5000R
Tape Deck: Sony TC-350
Speaker: Harbeth Compact 7ES3, Magnepan MMG
Cables: Stager Sound, Transparent,  DH Labs
Accessories: Cable Pro Noisetrapper, Sound Anchors Stands, Audience aR6

 






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