The Bryston 4B NRB available…
search
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.
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…
LG wrote about the 4B-ST in October 1999 (Vol.22 No.10):
When audio products sound great and have staying power on the market, they become classics. Two of the components used in my review of the B&W Nautilus 805 (elsewhere in this issue) have the legs to qualify as classics, but because they've been revised and we haven't heard the new versions, they've fallen off of Stereophile's "Recommended Components" listing. While the Bryston 4B-ST power amplifier and Velodyne HGS-18 powered subwoofer performed admirably when teamed up with the B&W Nautilus 805, are they good enough to…
When audio products sound great and have staying power on the market, they become classics. Two of the components used in my review of the B&W Nautilus 805 (elsewhere in this issue) have the legs to qualify as classics, but because they've been revised and we haven't heard the new versions, they've fallen off of Stereophile's "Recommended Components" listing. While the Bryston 4B-ST power amplifier and Velodyne HGS-18 powered subwoofer performed admirably when teamed up with the B&W Nautilus 805, are they good enough to…
Sidebar 3: Specifications
Description: Solid-state stereo power amplifier. Output power: 250W continuous into 8 ohms (24dBW), 400Wpc rms continuous into 4 ohms (23dBW); 800W continuous into 8 ohms in bridged mode (29dBW). Current delivery: 16A continuous, 48A peak, per channel. Frequency response: 1Hz–100kHz, ±3dB for 1W output. S/N Ratio: hum and noise, 108dB below rated output, 90dB IHF. Input sensitivity: 1.4V for 250Wpc into 8 ohms. Voltage gain: 30dB. THD+noise: 20Hz–20kHz, 0.01%. IM distortion (60Hz+7kHz, 4:1, SMPTE method): less than 0.01% at rated power. Damping factor: greater…
John Atkinson Opens
I've said it before and I'll say it again: a would-be loudspeaker designer shouldn't even start to think about the possibility of maybe designing a full-range, multi-way loudspeaker until he (and they do all appear to be men) has cut his teeth on a small two-way design. There is still as much art as science in designing a successful loudspeaker, even with all the computer-aided this and Thiele-and-Small that, that even a two-way design requires a designer either to be possessed of a monster talent or of the willingness to undergo months, even years, of tedious and…
I've said it before and I'll say it again: a would-be loudspeaker designer shouldn't even start to think about the possibility of maybe designing a full-range, multi-way loudspeaker until he (and they do all appear to be men) has cut his teeth on a small two-way design. There is still as much art as science in designing a successful loudspeaker, even with all the computer-aided this and Thiele-and-Small that, that even a two-way design requires a designer either to be possessed of a monster talent or of the willingness to undergo months, even years, of tedious and…
This palpability, solidity, of imaging applied to every record I could throw at the speakers. The only speakers I have found to even come near the CS5s' accuracy in image placement are the Quad ESL-63s. The Steinway on my own recording of Chopin's Op.31 Scherzo on the Stereophile Test CD was, well, just there, hanging between and behind the CS5s with a feeling of vivid reality that I have not experienced since I listened to the mike feeds over LS3/5as at the sessions. I say the speaker "positions" carefully, for there was nothing within that soundstage that would indicate the presence of…
The other exception I noted to the general euphoria concerns a tendency for upper-range notes in the range of female voice to "pop out," particularly when sung loud. The same characteristic can be heard on orchestral crescendi, particularly if the recording is a bit bright. I'm not complaining, I think, about hearing what's actually on the recording—the CS5s are capable of presenting other recorded aggravations with better evenhandedness. You hear the problem, you note that it's a problem, but this doesn't distract your attention from the music. This upper-midrange, volume-related problem…
Resolution: Jim Thiel's "White Paper" on the CS5 makes much of the importance of phase coherency, and JA's measurements verify that Jim has been unusually successful in satisfying his design criteria in this respect. How important is phase coherency? No one's produced the same speaker in both a coherent package and a non-coherent one—in fact, it would probably turn out to be impossible to produce even the same tonal balance in both coherent and non-coherent forms—and the tonal differences between speakers make it impossible to compare simply the presence or absence of phase coherency between…