Product Review - Bryston 3B-ST and 5B-THX
Power Amplifiers - July, 1997
John E. Johnson, Jr.
Click here for larger image
Bryston Power Amplifiers; Bryston 3B-ST; Two channel
power amplifier; THX-Certified; 120 watts rms/ch into 8 Ohms, both channels driven, 20 Hz
- 20 kHz; 200 watts rms/ch into 4 Ohms; Bridgeable mono power 400 watts into 8 Ohms;
Frequency response 20 Hz - 20 kHz ± 0.01 dB; Input impedance 50 kOhms; Damping factor
500; Sensitivity 0.75V rms for full output into 8 Ohms; THD 0.02%; S/N 108 dB; Size 5
1/2"H x 19"W x 10"D; Weight 22 pounds; Black sheet metal; $1,565; Bryston
5B-THX; Three channel power amplifier; THX- Certified; 120 watts rms/ch into 8 Ohms,
all channels driven, 20 Hz - 20 kHz; 200 watts rms/ch into 4 Ohms; Frequency response 20
Hz - 20 kHz ± 0.01 dB; Input impedance 50 kOhms; Damping factor 500; Sensitivity 0.75V
rms for full output into 8 Ohms; THD 0.02%; S/N 112 dB; Size 5 1/2"H x 19"W x
17"D; Weight 37 pounds; Black sheet metal; $2,465; Bryston, Ltd., 677 Neal Drive,
Peterborough, Ontario, CANADA K9J 7Y4; Phone 705-742-5325; Fax 705-742-0882; Web:
Bryston is one of a few companies you can count on one hand that has a 20 year parts and labor warranty, which is transferable (if your kids inherit the component, or you sell it, trade it, whatever). That in itself is a rarity that makes the company worth taking notice of and listening to their products. It means they are built like the proverbial Sherman Tank. When I lifted the 3B and 5B, I realized this, and quickly assigned the task of moving them into place to one of our younger and more-in-shape staff. Wow, is she strong :-)
The 3B is a two channel power amplifier, while the 5B has three channels. Both are rated at 120 watts/ch rms into 8 Ohms and are THX-Certified. Both models clip at around 150 watts/ch (8 Ohms). The 3B is dual-mono, and the 5B is triple-mono, meaning that all channels are in one chassis, and all channels have their own toroidal power transformer (82 VCT @ 2.75A, or 225 watts) and power supply capacitors. They share the same power cord, though. The power caps for each channel in both the 3B and 5B consist of two 10,000 µ, 63V. The rail is ± 55 V. Each amplifier channel, then, has 30.5 Joules of power supply energy storage. Both amplifiers have very hefty handles on the front, along with a power on/off push-button, and LEDs for each channel that glow green when the power is on, and red at clipping. The back panel [click here to see photo] has a detachable grounded (three-prong) power cord, ground-lift slider switch, bridging slider switch (3B), balanced (XLR) and unbalanced (RCA) input jacks, and balanced/unbalanced input slider switch. There is one set of 5-way speaker binding posts for each channel. The amplifiers use four bipolar output devices per channel.
Several other magazines have reported Bryston to sound bright. Actually this is one of the reasons I have been looking forward to getting some Bryston products, as I wanted to hear this purported brightness for myself. First, I connected the Brystons with all solid state equipment, including CD player, DAC, and preamplifier. The speakers were our venerable Carver Mark IV Platinum ribbons. Cables were Nordost Flatline and AudioQuest. The test CD was an assortment of Bernard Hermann film scores. Son of a gun, the sound was indeed somewhat bright and harsh. So, I set the volume at a level where the brightness was not apparent (turned it down until I could not detect it) and measured the voltage and current at the speaker terminals. Maximum voltage was 12.6 V with 2.41 Amperes of current. This is far below clipping, and includes the cancelling effects of the back EMF. Notwithstanding the brightness, I was extremely impressed with the bass response. It was deep and powerful, suggestive of a good power supply. Maximum SPL with these settings was 97.1 dB.
Next, I measured the square wave response at 10 kHz using ± 10 V. [Click here to see photo.] Notice that the response is very straight, with a slight amount of overshoot, rather than having a rounded corner. What this means is that Bryston amplifiers (at least the models we have for testing) reproduce complex waveforms in a precise and accurate way. My conclusion on this is that the harshness is not the fault of Bryston, but rather the source (CDs). For some time, many audio pundits claimed that 44.1 kHz sampling rate was adequate for reproducing the audio spectrum of 20 Hz - 20 kHz. This is based on an old principle that states you need only 2 samples to reproduce a waveform, and therefore, the sampling rate should be twice the highest frequency that is to be reproduced. Thus, 44.1 kHz is adequate for reproducing the upper limit of hearing at 20 kHz. In practice, it is just not working out that way, since the filters used to remove the harmonics in order to end up with just the sine wave contribute to a deterioration of the sound (rather than producing artifacts and removing them, it is much better not to produce them in the first place). This is one of the reasons CDs sound a little "bright". The funny thing is, now that the experts are saying 96 kHz sampling rate and 24 bit samples in upcoming CD technology will increase the frequency response to 40 kHz, they appear to be missing the point entirely. The main improvement is more likely to be encountered in the audible band, primarily 10 kHz - 20 kHz, because there will be more samples in this region. In fact, if the sampling rate were to be increased to 500 kHz (the frequency that Marantz has found to be the upper limit where audible improvements are noted, beyond which no further audible improvements can be detected), no filters would even be necessary, and the sound would be extremely clean. Even 20 kHz music signals would have 25 samples, more than enough to reconstruct accurate waveforms without having to filter out harmonic artifacts. So, what to do with the Bryston? Use a preamp and speakers that smooth things out.
I moved the Bryston to another lab, where we have an AE-1 Class A triode tube preamplifier, and a set of Celestion A-1 bookshelf speakers. Tubes tend to smooth rough edges, and the Celestions are laid back in the high frequencies. Lo and behold, the sound was marvelous. I could crank the sound up to room filling volume, with not the slightest hint of harshness. This was perfect synergism. On the latest Reference Recordings release of "Vivaldi for Diverse Instruments", RR-77CD, the trumpets, french horns, oboes, and harpsichord, came through with an added richness that made the whole system glow. In fact, the 3B was an ideal match for the Celestions. The music was now totally non-fatiguing, and so listenable, I found myself standing in front of the speakers, "conducting" the chamber orchestra. What a difference! Something in between could be achieved using a solid state preamplifier and ribbons such as the Eminent Technology LFT-8s, which are also somewhat laid back in the high frequencies. Using laid back speakers with Brystons would be all the more important in home theater, where we set up the 5B for the front left/center/right, and the 3B for the rear, in that movie sound tracks tend often to be gritty and overly bright.
So, there are several lessons to be learned here. One is that a fine amplifier like the Bryston could be made to sound harsh, if the rest of the system was not matched to it. All components in a hi-fi system alter the signal . . . ALL of them. Careful matching of the components is necessary in order to obtain a pleasing sound. The goal is to have an enjoyable experience listening to the music, not to fool yourself into believing that the orchestra is in the room. No audio system can do that. However, by combining the right components, you can have the pleasant experience. A second, and more fundamental lesson, is that you can't go to one store and say, "I like the sound of that amplifier, and I'll take it," then go to another store that has completely different components in the audition room, and say, "Gee, those speakers sound great . . . I'll take a pair," and go home with your purchases, and assume it will all sound terrific together. The amplifiers with slightly rounded leading edge corners on their square wave response will be more likely to sound great with a wide variety of other components, and the products with straight up and down square wave responses like the Bryston, will be more difficult to match. But when the match is made . . . wow!
John E. Johnson, Jr.
© Copyright 1997 Secrets of Home Theater & High Fidelity
Return to Table of Contents for this Issue