TAS 196: Aesthetix Rhea Signature Phonostage

It has long been an article of faith among audio “objectivists” that passive components—wire, resistors, capacitors, and inductors—have no effect on the sound of the product in which those components are used. That is, two capacitors of the same value will perform identically in the circuit—so why not use the cheapest version possible? This thinking led to some audio products, including professional gear, that were loaded with cheap carbon resistors, internal “hook-up” wire, and electrolytic coupling capacitors. Anything more was deemed a waste of money.

The high-end takes a different view. The designer of a well-regarded D-A converter told me about how, before going into production with his latest product, out of curiosity he replaced a $1 resistor with a $10 resistor (in the current-to-voltage converter’s feedback loop). The difference in sound was so great that he couldn’t imagine shipping the unit with the $1 resistor. The company absorbed the price difference.

So how much difference do exotic parts make in the sound of an audio product?

The Rhea Signature phonostage from Aesthetix provides a fascinating test bed. The Signature version uses the same circuit as the standard unit, but in the Signature that circuit is implemented with the higher-quality parts found in the $15k Aesthetix Io phonostage, making it possible to evaluate the sonic difference between very good and nearly-cost-no-object passive components. The price difference is substantial; the Rhea is $4000 and the Rhea Signature $7000. Rhea owners can upgrade to the Signature for the $3000 difference.

I know the standard Rhea very well; it’s been my phonostage of choice since I reviewed it in Issue 151 (December, 2005). The new unit looks nearly identical on the front and back—only a subtle “Signature” legend is etched on the display’s glass. But one peek under the hood and you can see that this is a different product. For example, the Rhea uses very high-quality Rel-Caps at many points in the circuit, but the Signature replaces these with huge red polypropylene film-and-foil caps from Dynamicap. In addition to such upgrades in parts quality, the Signature employs noise damping inside the chassis, as well as special vibration-absorbing feet under the transformers, choke, and the first gain stage (a point at which keeping noise low is critical). These feet are made by Harmonic Resolution Systems, the company that makes perhaps the most elaborate, best-engineered, and most beautiful equipment racks in the industry. The Signature’s tubes are selected to a higher standard—only 10% of the tested tubes pass muster. Finally, the Signature employs expensive variable capacitors in the RIAA equalization circuit to enable hand-tuning of the network for perfectly flat frequency response.

I had the Rhea and Rhea Signature side-by-side in my rack, driven by the outstanding Basis 2800 Signature turntable (fully loaded with Calibrator Base, Syncho-Wave power supply, vacuum hold-down, and Micro-Thin belt), Basis Vector 4 tonearm, and either a Dynavector XV-1s or Air Tight PC-1 Supreme cartridge. (Incidentally, the PC-1 Supreme was a complete revelation to me; I’d never heard a phono cartridge that was simultaneously so resolving yet so smooth and relaxed. The classic trade-off in cartridges between detail and musicality was rendered moot by the PC-1 Supreme.)

Being so familiar with the Rhea, it didn’t take long to appreciate the difference in the Signature. The biggest surprise was the bass, which exhibited far greater weight, extension in the lowermost octave, and dynamic impact. This wasn’t a subtle difference, but rather a wholesale transformation of the bottom end. Kick drum had more impact and solidity, and bass guitar was fuller in timbre and more fully fleshed out in body. The difference in the low end was fully equal to that of changing cartridges—or even loudspeakers. It was nearly on the level of moving from a stand-mount loudspeaker to a small floorstanding unit.

It wasn’t just that the Signature had more bass; it also had better bass. Small-scale dynamics, pitch articulation, and richness and density of tone colors were all in a different league. The Signature had a sense of tautness, precision, and detail that made the standard Rhea sound a bit soft, muddled, and smeared by comparison. Just listen to Jaco’s fabulous ensemble playing (and solo) on the Wayne Shorter composition “Port of Entry” from Weather Report’s Night Passage—the Signature revealed a new level of intensity and virtuosity in Jaco’s performance. After switching to the Signature, this live track was electrifying and thrilling in a way I hadn’t experienced before. The Signature resolved the blinding speed, the precise articulation of each note (in both pitch and dynamics), and the sheer musical intensity of the performance. The standard Rhea sounded a bit “watered down” by comparison, with less of the vibrant energy that makes this track special.

Without making a conscious effort, I found myself focusing on and appreciating the rhythmic contribution of bass players. I’ve heard the wonderful Bill Evans album Quintessence countless times, but through the Signature discovered another level of artistry in Ray Brown’s nuanced performance. Through his dynamic inflections, Brown creates his own varying rhythmic flow within the relatively stable time established by drummer Philly Jo Jones. Brown makes intriguing excursions that add a playful bounce to the sparse arrangements, notable on “Sweet Dulcinea.” The Signature’s greatly improved bass gave me a deeper involvement in, and appreciation for, this old favorite.

In the bass octaves audio components often make a trade-off between weight and precision. The leaner-sounding products tend to better reveal detail and dynamics; the warmer-sounding components are often a little smeared and slow. The Signature’s central triumph is its combination of raw bass power and heft coupled with speed, precision, and articulation. It was a combination I found addictive—particularly with the spectacular bass qualities of the Air Tight PC-1 Supreme cartridge.

Another dramatic improvement of the Signature was its cleaner, sweeter, and more refined treble. The top end had much more detail and nuance. For example, the Signature resolved the fine inner detail of cymbals in a way that the standard Rhea couldn’t match. The stick hitting the metal, the fine complex shimmer, and the way the decay of the instrument hung in the air were significantly better resolved by the Signature. Moreover, treble textures were smoother, purer, and less grainy through the Signature. Solo violin, the string sections of chamber ensembles, and massed orchestral strings all sounded more “organic” through the Signature thanks to its greater refinement, resolution, and reduction in grain. Although the standard Rhea is a great phonostage, the Signature makes it sound a bit coarse and grainy.

This combination of greater resolution and a more natural rendering of timbre extended to the midrange, but not to the same degree I heard in the treble. In the mids, instrumental texture was richer, denser in tone color, and more immediate. Despite the greater sense of palpability in the midrange, the overall perspective through the Signature was slightly more distant than through the standard Rhea. The Signature moved the soundstage back just a bit, and better resolved layers of depth. Having said this, however, I thought that the Signature made certain instruments seem to jump out of the soundstage with greater immediacy. Percussion and other instruments with steep transients seemed to suddenly appear right up front in the soundstage—the timbales on the terrific Mobile Fidelity reissue of Santana’s Abraxas, for example. Not only were depth and presence markedly improved, so was the resolution of instrumental decay.

You should know that if you value a dead-silent background, the Rhea and Rhea Signature might not be for you. This phonostage has up to a whopping 75dB of all-tube gain, which makes for some background noise in some systems. Many tubed phonostages employ a low-noise solid-state gain stage at the input (usually an FET) to amplify the cartridge’s output to a level that requires far less gain from the tubes. Others rely on a step-up transformer for the same reason. The Rhea is pure tube from input to output, with all the advantages and drawbacks of that topology. In addition, the noise level is highly dependent on tube quality.

Conclusion

I was really quite shocked by how much better the Rhea Signature sounded than the standard Rhea. In fact, I had planned on many long sessions of going back and forth between the two products to discern and describe the differences, but quickly realized that was unnecessary. Moreover, I enjoyed music so much through the Signature that it was hard to go back to the standard Rhea.

As great a phonostage as the Rhea is, the Signature version is on another level of performance. Yes, it’s nearly twice the price ($4000 vs. $7000), but the Signature is that much better. If you already own the Rhea, upgrading to the Signature will give you a new perspective on your record collection and favorite music. It did for me.

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Inside the Rhea

The standard and Signature versions of the Rhea share the same features and circuit topology. Both are slightly simplified versions of Aesthetix’s acclaimed Io phonostage. The unit features unbalanced inputs, with balanced inputs available for a small additional charge. The gain is adjustable in eight steps, with up to 75dB of gain at the maximum setting. Nine different cartridge loadings are provided. The gain and loading can be set independently for each channel. The way in which you adjust the gain and loading is very cool: Press the “Gain” button, for example, and the amount of gain in dB appears on the front-panel display. Simply push the right side of the display to increase the gain, or the left side to decrease it. The arrangement is the same for changing cartridge loading. In addition, you can adjust gain and loading from your listening seat via the supplied remote control.

The circuit is based on five tubes per channel, with two 12AX7LP tubes at the input operated in single-ended mode followed by a single 12AX7WB that functions as a phase splitter to create a balanced signal. The output of the 12AX7WB is filtered by a passive RIAA network, and then amplified by another 12AX7WB. The output buffer is a 6DJ8. Unique to the Signature version are variable capacitors in the passive RIAA network that allow each unit to be hand-calibrated for flat RIAA response. The variable gain and loading are realized with two separate switched-resistor networks.

The power supply is huge, and features all-discrete regulation (except for the supplies of the control and display circuits). The power transformers are mounted on an isolated substrate and encased in shielding.

The metalwork, industrial design, interior layout, and build-quality are exemplary. Moreover, the feature set—three inputs, adjustable gain and loading via remote control, built-in cartridge demagnetizer, balanced outputs—makes the Rhea compatible with a wide range of systems. RH

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SPECS&PRICING

Aesthetix Rhea Signature phonostage

Tube complement: Two AX127LP, two AX7WB, one 6DJ8 (per channel)
Inputs: Three RCA
Outputs: Three RCA, two XLR
Features: Front-panel-variable gain and loading (independent for each input); remote-control gain, loading, and cartridge demagnetizing
Dimensions: 18″ x 4.4” x 17.6″
Weight: 40 lbs. (shipping)
Price: $7000