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Product Review
 

Red Planet Labs STR102 Two-Channel Power Amplifier

October, 2004

Jason Victor Serinus

 

Specifications:

 

● Output: 225 Watts RMS per Channel
    into 8 Ohms
● THD: < 0.05 % 20Hz-20KHz
● Power Bandwidth: > 130 kHz
● Slew Rate: > 30 V/usec
● Damping Factor: > 100 1 kHz to 20 kHz
● Input Impedance: 100 kOhms
● Dimensions: 7.5" H x 17" W x 15.5" D
● Weight: 45 Pounds
● MSRP: $2,995 USA


Red Planet Labs

www.rplonline.com

Introduction

If I knew nothing about Red Planet’s flagship two-channel amplifier before John Johnson invited me to review it, I am richer for the experience. This is one impressive amplifier.

Red Planet Labs is the offspring of Daniel Marz. An Argentinean émigré residing with his wife Graciela in San Diego, Daniel’s product line consists of two 2-channel amps and two 5-channel amps.

The STR102 arrived fully broken-in but without documentation. Unable to find a downloadable manual on the web, I did what comes naturally. I hooked up single-ended Nordost Valhalla interconnects from the Theta Gen. VIII to the amp’s input, connected the Talon Khorus X Mk. II speakers via Nordost Valhalla cabling, and ran a Nordost Valhalla power cable from the PS Audio P600 Power Plant. (There are two sets of speaker outputs should you wish to run a second set of speakers, as the amp is stable into 1 ohm.)

There is also a Trigger On/Off to use when you want to have the preamp turn the power amp on. Flipping the on-off switch on the front panel set two innocuous red lights aglow. An hour later, I was ready to listen.

Initial Impressions

Whenever solid state amplification arrives for review at Casa Bellecci-Serinus, my first concern is that it may sound overly harsh, bright, or lacking in air. This is why I generally use tube products. However, I immediately realized that the STR201 is an amp I could listen to for hours without fatigue.

Noting that the amp also has balanced inputs, I disconnected the single-ended inputs (there is no switch to flip between inputs) and plugged in Valhalla balanced interconnects. The volume level was different, requiring immediate adjustment (see discussion below). Once that was accomplished, I was even more impressed with the sound. There was a noticeable lowering of the noise floor with balanced connections, resulting in a greater sense of clarity and musicality. Though I know in part this is due to the Theta, which excels in balanced mode, it is also due to the STR201’s design.

Not far into my listening sessions, Daniel Marz surprised me with a phone call. He and his wife were 45-minutes away, visiting their son who attends Stanford University. Could they come by and hear my system? Since I had a host of questions on my mind, I responded, “By all means.”

When the Marzs sat down to take a listen, Daniel commented that the system sounded a little dark. Removing two recently arrived Nordost Valhalla power cables from the high power Parasound Halo JC-1 monoblock on which they had been breaking in, I used them to replace the Elrod EPS Signature power cables on the Theta DAC and Power Plant. All my components were now powered via Nordost Valhalla power cables. Daniel’s face immediately relaxed as he sat down to enjoy listening to some of the same tracks he uses to demonstrate his products at shows.

Interview with Daniel Marz

After listening for awhile, I invited Daniel upstairs to the office to discuss the amp’s technical aspects. In doing so, I made clear that, besides mentioning that I thought the amp outstanding for the price, I was not going to discuss my observations with him as a matter of principle. Daniel fully understood my position, and never tried to press me for my opinions.

With the Ms. comfortably ensconced in the living room, blissfully listening to Piotr Andreweski playing Bach and Beethoven, Daniel Marz shared the following:

“The STR201 amplifier is balanced internally. If the source is correctly implemented, it should output the same voltage in balanced and single-ended modes. Normally designers don’t do it that way, so the volume will be 6 dB higher when the amp is driven balanced.”

[While I am in no position to declare whether Theta has correctly implemented its fully-balanced technology, I did note that a 6 dB volume adjustment was necessary when switching to balanced interconnects].

“The advantage of balanced topology is rejection of noise that the cables pick up. In terms of the sound, itself there should not be a great deal of difference.

“I recommend using balanced when you have a long run. It shouldn’t make that much of a difference with 3 or 4 feet; keep cables short. I personally use balanced interconnects because I make the cables myself and don’t have a problem with cost. In my house the AC is horrendous so balanced interconnects are better.

[My sense is that even with cables under two feet long, the amp’s balanced mode sounds superior. However, because the Theta Gen. VIII I paired with it definitely sounds better in balanced mode, I won’t swear to it].

“I designed the STR201, and released it close to two years ago. We have a patent on the amplifier’s architecture, issued six months ago. I secured 15 patents while working for other companies, but this is the first I’ve gotten in my own name.

“When you register the patent, you describe the invention verses the present art and then make claims on the Intellectual Property (IP). We made 26 claims for having a unique design. The Patent Office did not challenge a single one, which is very unusual. This is the first time in my life that I didn’t have a single challenge on one of my claims.”

I asked Daniel what was unique about the design that he wanted to share.

“When schools teach engineering, they teach people how to solve problems. That’s only 20% of the battle. The most important thing is how to define the problem. In this case, is the problem reproduction of a signal or is it to produce a memorable experience?

“When people say they are reproducing the experience of a live concert via a high-end sound system, that is impossible for two main reasons:

1. There is a synergy between a performer and an audience that doesn’t exist in audio.

2. An instrument or voice is a single source. Stereo offers two sources, surround even more. So technically it’s a completely different experience. You rely on psychoacoustic phenomenon to recreate what was recorded.

So for me, the important thing is to get the listener involved emotionally.”

I asked Daniel why his design was solid state rather than tubes.

“I have studied both psychoacoustics and live acoustics. For ears, in addition to my own, I rely on my wife who is a guitarist, my kids, and people who are not necessarily audiophiles. My understanding of psychoacoustics, combined with a great deal of experimentation – I’ve been designing gear for 30 years – led to the development of our proprietary sets of specifications for amplifier design. We are pretty certain that our specs have led us to a design that will involve the audience emotionally in the sound.

“I don’t think tubes are necessary. If I can achieve our goals using solid state, then there is no need to rely on tubes. I switched to solid state after using tubes when I was 15 or 16 and never went back. Solid state’s advantage is reliability. If you can define the problem – in this case arriving at our proprietary specifications – then the solution is obvious.

“My approach is considered heretical in the audiophile community because I use solid state and judicious feedback when necessary, both of which depart from the norm. The results I think speak for themselves. We did lots of A/B tests against tube, solid state, and hybrid amps. For the most part, people prefer our amps. For the money, it’s very tough to beat.

“I use my own cables because I have control over what I’m doing. For the signal I use solid core silver with Teflon coating, and for power cords I use my own silver-plated copper with Teflon shielding, with the shield terminated at one end.”

Because the Secrets Forum hosted a short but hot debate about the necessity of breaking-in solid-state components, I asked Daniel his opinion about the need for break-in.

“My equipment needs some breaking-in, perhaps 10 –15 hours. Break-in opens up the sound a little bit and makes it warmer. In the power supply the electrolytics need to reach a level at which they’re stable. Part of our design is to try to remain as independent as possible of electronic components, i.e., resistors, capacitors, transistors, etc. within the amp. One of the reasons we can do this is that the design is quite insensitive to components.”

I note that Daniel also left me one of his personal power cables to try out. He recommended a minimum of 50 hours of break-in time before listening.

For further information on Red Planet Labs’ design philosophy and implementation, see http://www.rplonline.com/about.htm

Listening

Allow me to dispense with the formality of listing each selection auditioned followed by comments. Whether I played female jazz vocals with simple accompaniment, Canteloube’s Songs of the Auvergne with chamber accompaniment, Terry Evans singing the blues, the Minnesota Orchestra going full force in Rachmaninoff, solo guitar, a flute/harp duo, or a New Age synthesizer disc here for review, my impressions remained uniform. This is one excellent, highly musical amp.

Everything about the STR201 strikes me as neutral and pleasing. Timbre is true rather than either metallic, overly bright, or dulled. The bass is solid and lacking in the bloat that afflicts so much mass market gear. Detailing is quite good and thankfully not overly etched, and placement of images is excellent. And in balanced mode, transparency is excellent.

In absolute terms, the STR201 lacks the all-encompassing sense of air, midrange warmth, and captivating bloom heard from the best tube gear. It also doesn’t produce the widest of soundstages, or supply all the three-dimensionality I’m used to hearing. Nor does its power supply deliver the staggering bass slam (and I do mean slam) of the twice-the-cost 400W current-sucking room-heating Parasound monoblocks. (Nor would one expect it to). Finally, while the fundamentals of a tone are there in spades, the ultimate complexity and harmonics - the overtones and undertones – are less present than from far more expensive gear.

[I have taken a brief listen to the not-for-sale proprietary power cable Daniel uses on his equipment. I put it on my transport, which along with my amp registers the most change in sound when I switch power cables. The cable produces a nice, neutral sound, but the extra detail, shine, presence, and bass impact - the ultimate extension, detail and depth heard heard with the Nordost Valhalla cords - are absent. As just one example, the sounds of the hall heard at the start of Reference Recordings’ Symphonic Dances are mostly lost. I wonder how Daniel’s design might have evolved had he had access to more revealing cabling].

Regardless, the STR201 is tight, fast, and smooth throughout its range. Highs are well extended, and the bass is thankfully solid and full. But most of all, its sound is MUSICAL. And for $3000, musicality is something infrequently heard from a solid state stereo amp, in my opinion.

Musicality is something you cannot derive from specifications. You can put the finest components in the world together and produce something that looks and tests great on paper but leaves you cold. (It’s no different than putting a Guarneri del Gesu or Stradivarius violin in the hands of a mediocre performer.) It takes a musical ear to produce a musical component.

In my most recent period of reviewing, when the combination of revised speakers and state-of-the-art DAC/preamp and cabling has rendered my system ultra-revealing, I have auditioned three other solid state two-channel amps: the Soaring Audio SLC-300, the Edge G-8, and the Parasound monoblocks. The Parasounds are in a class by themselves, with a host of awards attesting to their breakthrough-for-the-price design. (The forthcoming Soaring Audio monoblocks, auditioned one afternoon at a Bay Area Audiophile Society beta test session held at my home, promise another breakthrough-for-a-considerably-lower-price design.) But for a one-piece stereo amp, the Red Planet Labs STR201 takes the prize.

Conclusions

The STR201 satisfies in ways relatively few other amps in its price range do. Its sins, to the extent one can even call them such, are sins of omission rather than of commission. When you listen to the STR201, you tend to focus not on specifics but rather on an all-satisfying level of enjoyment. So much transparent, neutral, and all-enveloping musicality for $3,000 qualifies the Red Planet Labs STR201 as a breakthrough product.


- Jason Victor Serinus -

Associated Equipment:

Digital Front End
Sony 707ES transport modified by Alexander Peychev of APL Hi-Fi
Theta Gen VIII DAC/Preamp

Amplification
Jadis Defy 7 Mk III or IV modified with a Siltech silver harness

Loudspeakers
Talon Khorus X speakers MK. II (with latest modifications and Bybee filters)

Cabling
Nordost Valhalla single-ended and balanced interconnects and balanced digital interconnects
Nordost Valhalla bi-wired speaker cable
Acoustic Zen Silver Reference II balanced interconnects
Either Harmonic Tech Magic One, Nordost Silver Shadow, or Nirvana digital interconnect for DVD-V
Power cables: Nordost Valhalla and Nordost Vishnu; Elrod EPS Signature 2 and 3 plus EPS 1, 2, and 3; WireWorld Silver Electra 5, PS Audio X-treme Statement, Harmonic Tech, and AudioPrism SuperNatural S2.

Accessories
PS Audio P600 Power Plant power synthesizer with MultiWave II
PS Audio Ultimate Outlet; PS Audio Power Ports
Michael Green Deluxe Ultrarack, Basic Racks and room treatment
Ganymede supports in main digital chain and under speakers
Michael Green Audiopoints, and Black Diamond Racing Cones elsewhere
Shakti stones for Amp and Theta
Stillpoints ERS EMI/RFI sheets on some components
Bedini Dual Beam Ultraclarifier
Audioprism CD Stoplight
Marigo as yet unreleased Signature Mat for use atop CDs
Ayre demagnetising CD and the original Sheffield/XLO degmagnetising and break-in CD.

 

© Copyright 2004 Secrets of Home Theater & High Fidelity

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