What's the buzz?
The Avantgarde Uno's high sensitivity means that any residual noise in the signal is going to be more noticeable; this just comes with the horn territory. Even so, the noise emanating from the speakers when I initially fired up the Geminis was considerably higher then I've been used to, and tweaking the hum pots didn't help. The noise, present in both channels, was the kind of buzz normally associated with ground loops, so I tried the normal variations on grounding (connecting/lifting grounds at various points in the system). Nothing seemed to help. A call to Rankin…
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The sound of 45s
The 45 tube may be an antique, but its sound in the context of the Wavelength Gemini was anything but old-fashioned. Apart from the limitation of output level, the sound with the Sylvania 45s was wide-ranging, with open, extended highs that minimized high-frequency nasties while allowing both detail and the overtones of treble instruments to be presented in a natural manner. Bass was deep and well-controlled, with hardly a trace of the added warmth/midbass emphasis and softness that many people think of as "tube sound." Of course, the subwoofer part of the Avantgarde…
The 45 tube may be an antique, but its sound in the context of the Wavelength Gemini was anything but old-fashioned. Apart from the limitation of output level, the sound with the Sylvania 45s was wide-ranging, with open, extended highs that minimized high-frequency nasties while allowing both detail and the overtones of treble instruments to be presented in a natural manner. Bass was deep and well-controlled, with hardly a trace of the added warmth/midbass emphasis and softness that many people think of as "tube sound." Of course, the subwoofer part of the Avantgarde…
Of the three pairs of 2A3s, the AVVT mesh plates were the most distinctive, visually and sonically. These big, macho tubes are considerably taller than the other 2A3s, and had by far the most dynamic presentation. It was an exciting sound, and the soundstage seemed even deeper than usual. In fact, I began to wonder if the sound of the recordings was being enhanced in some way, almost like one of those analog reverb devices used by studios before digital.
I'd heard rumors about AVVT 2A3 mesh plates being microphonic, so I did a bit of informal testing. Tapping the tube gently, or even…
Sidebar 1: Specifications
Description: Single-ended triode amplifier. Tube complement: one each 6V4/EZ80, 417/5842A, and 2A3 or 45. Power output: 2-5W into 4 or 8 ohms (3-7dBW), depending on tube type. Distortion: not specified. S/N Ratio: not specified. Bandwidth: 25Hz-50kHz for 45 tube, 20Hz-40kHz for 2A3 tube. Input impedance: 47k ohms.
Dimensions: 5.5" W by 12" D by 10" H. Weight: 12 lbs.
Finishes: Black. Add $500 for brushed stainless steel. Cherry, maple, or walnut hardwood top; other top finishes available.
Serial numbers of units reviewed: None found on chassis.
Price…
Sidebar 2: Associated Equipment
Analog source: Linn LP12 turntable (fully updated), Ittok tonearm, AudioQuest AQ-7000nsx cartridge.
Digital source: PS Audio Lambda II CD transport, Perpetual Technologies P-1A/P-3A digital processors.
Preamplifier: Convergent Audio Technology SL-1 Ultimate.
Loudspeaker: Avantgarde Acoustic Uno 2.0.
Cables: Digital: Mystic Reference I2S, Illuminati Orchid AES/EBU. Interconnect: Nordost Quattro Fil, Nirvana S-X. Speaker: Nirvana S-L, Nirvana S-L wiring harness for Avantgarde Uno 2.0. AC: PS Audio Lab Cable, TARA Labs Decade. (Note: Installing…
Sidebar 3: Measurements
Measuring the Wavelength Audio Gemini took rather longer than I had anticipated, given the choice of output-stage tube and the two transformer taps. To keep things simple, I decided to measure the amplifier using just one example of each output tube: a Sylvania 45, which Robert Deutsch had found to be quietest; and a Sovtek 2A3, which RD had preferred to the NOS Raytheon and the microphonic AVVT mesh-plate 2A3.
There was also the issue of the tube-heater hum having to be manually nulled. I did my best, but the orientation of the chassis and the presence of…
Though its minimum midband distortion into a matched load was quite low, at around 0.25% (2A3) or 0.16% (45), the Gemini is not a low-distortion amplifier. This can be seen in figs.6 and 7, which show the small-signal THD+noise percentage from the amplifier's 8 ohm tap plotted against frequency into resistive loads ranging from 16 down to 2 ohms and into our simulated speaker. The distortion rises significantly into all loads in the bass, which suggests RD was wise to use a powered subwoofer. But it also rises into loads both higher and lower than the nominal transformer tap value, with the…
Despite the amplifier's "bent" transfer function, levels of intermodulation distortion were lower than I expected. As can be seen in figs.12 and 13 (45 and 2A3, respectively), while the 1kHz difference component with either tube reached -50dB (0.3%), the higher-order spuriae lay below -60dB (0.1%). The furriness of the FFT-derived traces is due to the presence of hum in the Gemini's output signal.
Fig.12 Wavelength Gemini, 45 tube, 8 ohm tap, HF intermodulation spectrum, DC-24kHz, 19+20kHz at 2V into 8 ohms (linear frequency scale).
Fig.13 Wavelength Gemini, 2A3…
Manufacturer's Comment
Editor: I would like to thank Bob Deutsch and John Atkinson for taking so much of their time with this product [May 2001, p.125]. I designed the Gemini so that it would work with any new or NOS (new old stock) 2A3 and 45 tube. I used over 60 different 45s and 50 different 2A3s in the design process of this amplifier. The possibilities are endless. I am so glad that they were able to get the same results that I have. I would also like to thank Neil Muncy for his help.
Bob received one of the very first Geminis that I had made. I and the other customers were…
Two relevant reader's letters appeared in July 2001 (Vol.24 No.7):
Call him an optimist
Editor: As a longtime reader of Stereophile, I strongly support the present mix of objective testing and subjective reviews. While most readers, including myself, are primarily interested in how a component sounds rather than how it measures, the test data can often provide interesting insights.
That said, I must take exception to the "commentary" by John Atkinson in his test report on the Wavelength Gemini amp (May 2001, p.127). John criticized Gordon Rankin's decision to use an AC…