Description: MOSFET stereo amplifier. Power output: 120Wpc into 8 ohms (20.8dBW), both channels driven, from 20Hz–20kHz with less than 0.05% THD; 200Wpc into 4 ohms (20dBW), both channels driven, from 20Hz–20kHz with less than 0.1% THD. SMPTE IM distortion: less than 0.05% (0.25W–120W, 8 ohms). TIM: unmeasurable. Hum and noise: 105dB below rated output, 90dB below 1W. Frequency response: –0.1dB from 20Hz–20kHz, –3dB from 1Hz–200kHz. Input sensitivity for rated output: 1.3V; for 1W: 130mV. Input impedance: 47k ohms. Damping factor: greater than 500. Risetime:…
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The $1200 Counterpoint SA-100 amplifier came up to bat fourth in my listening sessions, behind (in order of appearance) the Adcom GFA-555 II (not reviewed here, but sent along by JA for comparison purposes), the VTL Tiny Triode monoblocks, and the Muse Model One Hundred. Thus, my progression went from bipolar solid-state to tube to MOSFET, with a wide spread of sonic characteristics between them: stygian bass from the Adcom; uncanny spatial presentation and vocal reproduction from the VTLs; and an overall superior sound from the Muse. I was therefore eager to see where the tube/MOSFET hybrid…
Postscript: A New Sample
Shortly after my review hit Santa Fe, Tom Norton called to say that he'd arranged for Counterpoint to send along another SA-100; evidently, the amp I heard was one of the first hundred off the line, and Counterpoint's John Fermin felt that it might not represent a typical SA-100 as well as a current unit. The new amp arrived a few days later, but just as I was about to listen to it after a few days' burn-in, TJN called back, telling me that Counterpoint had sent it with the wrong input 6DJ8s, and that the new tubes were en route. But didn't Counterpoint subject…
Sidebar 1: CG's System
The listening setup consisted of my self-modified Philips CD-50 fed my buffered passive preamp, this connected to the amplifiers under review. Interconnects and speaker cables were Straight Wire Maestro. Speakers were either Spica Angeluses or Thiel CS1.2s; all line-level gear was plugged into the Audio Express NoiseTrapper Plus.—Corey Greenberg
Sidebar 2: Measurements
All the measurements were made after each amplifier had been preconditioned by running it at one-third full power into 8 ohms for an hour, which thermally stresses the amp to the maximum. Though the Counterpoint didn't overheat, its heatsinks did get too hot to touch. The review logistics meant that all the measurements were performed on the first sample. I was a little surprised by the Counterpoint's small-signal frequency response; it showed a rising trend in the top audio octave (fig.1), which results in a degree of overshoot on the 10kHz squarewave shape (fig.…
Sidebar 3: Specifications
Description: Hybrid stereo power amplifier. Power output: 100Wpc into 8 ohms (20dBW), 170Wpc into 4 ohms (19.3dBW). Gain: 30dB. Frequency response: 5Hz–100kHz. S/N ratio (20Hz–80kHz, ref 85W): 92dB. Distortion (1kHz, 8 ohm load): 1% at 100W, 0.7% at 10W, 0.3% at 1W. Output impedance: 0.9 ohms. Maximum current available: 25A rms, measured 1kHz gated On for 20ms, Off for 480ms, into 0.1 ohms. Damping factor: 8.9, referenced to 8 ohms at 1kHz. Input impedance: 100k ohms, 100pF. Signal polarity: non-inverting.
Dimensions: 19" W by 4.46" H by 12.68" D. Weight: 28…
On January 1, 1990, Canadian electronics manufacturer Bryston instituted a remarkable warranty program that covered each of their products for a full 20 years. This warranty includes all audio products ever manufactured and sold under the Bryston name. Besides covering parts and labor costs, the company will also pay shipping costs one way. This is all the more significant for their 4B NRB amplifier, which has been in production since 1976. The amp's $2k price, while not cheap, is at the lower end of what well-heeled audiophiles typically pay for amplifiers.
The Bryston 4B NRB available…
I noted improvements in many small touches that confirmed the company's design philosophy of fine-tuning a good product rather than trying to produce a "new sonic breakthrough" each year. For example, input jacks are now soldered to their respective printed circuit boards, emerging through 14mm chassis holes which allow the push-on RCA connector sleeves to be inserted into the chassis, providing superior strain relief. Each pcb has heavier copper traces than before. A slow-start circuit has been added to avoid line surges when the amp is turned on. Compensation has been provided with the use…
Sidebar 1: 1992 Review System
The 4B drove a wide variety of loudspeakers, including dynamics (Snell A/IIIs, Bs, and Es), electrostatics (Quad ESL-63/USA Monitors), minimonitors (Sonus Faber Minima), and subwoofers (Quad/Gradient SW-63s). At different times, it was run single-ended and balanced, and used both as the upper-range and subwoofer amplifier in bi-amplified systems.
Reference amplifiers included a Mark Levinson No.27 and a Krell KSA-250. The Quad full-range loudspeaker system was used with its own Gradient crossover unit with balanced interconnects; the Type A/III…
Sidebar 2: Measurements
The input impedance of the Bryston measured just over 33k ohms at the balanced inputs, just over 47k ohms at the unbalanced. Measured voltage gain into an 8 ohm load was 30.2dB in either configuration. (Normally, there is 6dB greater gain in a balanced configuration.) The measured output impedance of the Bryston was under 0.06 ohms at or below 1kHz, increasing to a maximum of 0.13 ohms at 20kHz, which is still very low. DC offset measured 16.3mV in the left channel, 16.7mV in the right. Signal/noise (wide-band, unweighted at 1W into 8 ohms) measured 67.7dB balanced…