Words by Martin Colloms, all rights reserved

Renaissance RA-01

Has newcomer IES created the right mix of 300B valve magic and real-world power and drive ability?

words Martin Colloms

photography Tony Petch

Price £5995/pair

supplier Integrated Engineering Solutions

contact 023 8090 5020

Based in Southampton, Integrated Engineering Solutions Ltd (IES) specialises in professional communication and instrumentation systems. But IES is a new entrant into hi-fi - the 'Renaissance Amplification' brand provides the launch platform for the RA-01, a monoblock triode power amplifier. For designer Chris Jennings, this was something he had to do, despite a jump into the unknown. Production engineer Sean Redshaw noted 'here instrumentation could not define sound quality, we now had to learn how to use our ears!'

Handsomely built in real wood and satin gold plate, the RA-01 has turned its back on the fashionable single-ended approach and has opted instead for push-pull, aiming for a good dose of classic 300B power triode character and quality with some real world power and load drive ability.

The specifications are understood to be nominal, with RA quoting a 22W/ch power (6-8 ohms loads), a high 0.5V sensitivity (fine for passive controllers), a kind 100k ohms/100pF input impedance and a wide -3dB bandwidth of 12Hz to 70kHz. For +/-0.25 limits RA quotes 20Hz to 25kHz. While it began life as a zero negative-feedback design, curiosity led RA to experiment with a shade of NFB and finally to settle on a very moderate level of 6dB feedback as delivering the optimum sound and load combination.

Zealous converts to subjectivism, the designers have embraced most of the classic valve/tube design points. All the buzz words are here - 'non-ferromagnetic metalwork', 'single-strand' silver point-to-point wiring, vibration isolated component chassis, full Class A operation, all-triode tubes, copper foil coupling capacitors, Kiwame carbon resistors, metallised film reservoir capacitors, and selected Black Gate decoupling capacitors.

The output tubes are JJ 300B, which may be upgraded (for £1650) to genuine Western Electrics matched quads. JJ E88CCs (or Mullard NOS option) are fitted at the input, while a Sovtek 65N7GT serves for the driver. The rectifier tube is a 5U4G Russian Edicron. Last but by no means least is the complement of wound components; the mains transformer, the power supply block and the output transformer. All these are designed and made by RA. A distinctive and styled protective tube cage is also available where safety considerations are paramount.

Input is via a gold plated single-ended phono socket. There are gold-plated binding posts for speaker connection, a bit cramped for access, with 4mm through connection for plugs.

SOUND QUALITY

Effectively, there are two versions of this product; the standard model with JJ 300Bs, and the alternative with Western Electrics 300Bs and the Mullard input valve. It's worth stating that both were fine-sounding and one does not invalidate the other. Speakers used included Quad ESL-63, Wilson System 6 and Tannoy TD12 (which seemed to suit the amplifier best).

Taking the standard version first, general impressions were of a nicely balanced sound, noticeably sweet in the upper treble, naturally dynamic and expressive, with surprisingly satisfying, articulate and capable bass, a full notch beyond single-ended types. While the midrange wasn't quite as fluid or natural as the best single-ended designs, by normal standards it remained first rate - creamy, easy on the ears and smoothly flowing.

It sounded nice with rock, but if driven towards the power limit it softened, giving a gentle, compressed quality with a loss of resolution and dynamics. Nevertheless the peak sound levels were good, approaching those of the Cary 805. Classical and jazz both fared well, and this amplifier proved to be involving and fatigue-free. Image width, depth and focus were all convincing, placing this amplifier in the upper echelon for outright performance. I was enjoying the combination of a pure triode sound with push-pull power; then I switched to the Mullard input option and finally to the Western Electric 300Bs.

The JJ version had scored a respectable 29 - on my usual scoring - well up in its price class. However the addition of the Mullard EC88C improved dynamics, reduced treble grain slightly, gave purer vocal sibilants as well as better punch and articulation, lifting the score by some 12% to around 32, which was higher than I expected.

I had still more fun with those costly WE tubes. Out of the box the Westerns sounded clearer, more highly resolved, with more natural textures. Rhythm and drive were both significantly advanced; it was as if the entire sound had been given a tune-up. With some further running in there was now a clear gain of 5 points, the final score a most creditable 37. Here was a sound you could leave playing all day long!

CONCLUSION

I enjoyed trying out the Renaissance. Both valve options proved to be valid contenders at their price, so it's up to you. Delivering a creditably musical high-end triode performance, this amplifier design was distinguished by a level of engineering skill which has extracted a powerful, stable and load tolerant performance from Class A push-pull 300B tubes. Power delivery was generous for the genre, and both bandwidth and distortion figures were very good.

While the RA-01 doesn't have quite the single-ended zero feedback sound, it also avoids the flaws. Easy on the ears, this fine sounding, well-built and powerful British triode power amplifier wins a recommendation.

Side-by-side: comparisons were made with Krell FPB300mc, Naim NAP250 and Audio Note Kegon power amps. These were used with Lamm LL-2 and Conrad-Johnson ART pre-amps, and the Audio Synthesis Passion Classic passive unit

LAB REPORT

Test results for the RA-01 inspired confidence and suggested better-than-usual compatibility.

Optimally matched to an 8 ohm load, power fell by just over 4dB into 4 ohms, just meeting the claimed 22W specification. Most single-ended amplifiers fail to meet their spec, but this design (for 3%) reached 29W over a wide bandwidth, and it played sufficiently loud on the Tannoys.

The 0.83 ohm output impedance was high enough to cause small variations in sound balance with a given loudspeaker impedance, but rather better than the 1.5 to 2.0 ohms sometimes encountered. At rated power, distortion and noise were typically at 40dB or 1%. Distortion fell to surprisingly low levels at lower powers and though the spectrum extended at least to the 11th harmonic, odd and even components were reasonably balanced and were generally low, as the 1W distortion spectrum shows. The high-frequency intermodulation distortion test (1W, 19kHz/20kHz, 8 ohm) also gave a fine result.

There was no point in displaying the frequency response since it was excellently flat, 30Hz to 80kHz, -3dB at 8Hz and 108.2kHz. It actually continued with minor ripples to beyond 200kHz: even at full power, the IM result was held below 0.5%. Peak current was fair enough for the power at +/-2.8A, given that the current clipping was as benign-sounding as the voltage clipping. But tough low impedance loads should be avoided.

Noise levels were very satisfactory thanks to the balancing circuit for the output tubes. Input impedance was negligible while sensitivity was high enough at (600mV for full power) for compatibility with passive controls if so desired.