Reprint from
HiFi Test TV-VIDEO 2/03

BRYSTON BPS-25 Preamp and
4B-SST Power Amplifier

S Stands for Sensational!

"They are the new reference and become the benchmark for other stereo amplifiers"

Olaf Sturm

As Time Goes By

For over 40 years amplifiers of excellent quality have been built in the Canadian City of Peterborough. Today the name Bryston stands for tradition, tonal culture, and longevity. Therefore the update of the BPS-25 preamp/4B-SST power amplifier combination is an exciting event for HIFI TEST (Magazine).

Thomas Bernhard, a member of the German Bryston distributor, had certainly imagined the first reaction to the announcement that Bryston has updated preamps and power amplifiers quite differently. Instead of challenging inquiries on the part of the editorial staff he only garnered frowns at first. The logical explanation comes readily to mind, because for about five years the team consisting of the BP-25 preamp and the 4B-ST power amplifier have provided flawless service as working tools for the editorial staff. Until today there was no reason to doubt the excellence of the reproduction. Until today, because now the competition, from the same Bryston company, is ready to become its replacement. No question, it will be an exciting contest. At first glance nothing seems to have changed optically, but when one looks more carefully the first justified practical changes appear. The jacks of the preamplifier are no longer recessed into the cabinet, but now stick out. Great, because now every signal cable really fits. In the power amplifier the power switch gave way to a membrane switch, which acts as an automatic circuit breaker. So only an "on-the-surface" cure? Not at all as a closer examination will reveal.

BPS-25 Preamp

The 25 volt requirements of the shallow BPS-25 preamp are provided by an external power supply, which has become considerably larger in comparison to its predecessor. Likewise more active line filtering is now taken care of, and negative impairments through high frequency interferences are thereby effectively suppressed. The filter capacity of about 27,000 microfarad is now twice as large as before. Using the trigger output voltage the power amplifier can now be turned on simultaneously (with the preamp). The front panel has not been changed optically, and also on the inside the developers retained what has been tried and proven. The two stage active equalization for the phono input, which maintains a maximum deviation of .25 dB from the ideal RIAA curve, remained. In order to keep the signal paths short, the signals are switched directly at the inputs.

Besides six RCA unbalanced inputs, two XLR balanced inputs are provided. A motorized Alps potentiometer, which exhibits only minimal channel deviation, is used for controlling volume. For "muting" of the inputs, and for phase reversal, momentary toggle switches were chosen because these are remote controllable. The infra-red remote control consists of a neatly machined aluminum block and features four functions which we consider practical and useful. If operational difficulties arise because the remote control of another component interferes, then the coding in the Bryston preamp can be changed using the built-in "mouse piano" (dip switch). This is application (user) friendliness for which Bryston provides a twenty year warranty. Apparently the other electronic manufacturers cannot allow themselves this much confidence in their own products.

4B-SST Power Amplifier

When in the middle of the nineteen seventies a power amplifier with the designation "4B" came into use, everyone agreed that this amplifier would represent a milestone in amplifier construction. They were proven correct, because until today 30,000 of these power amplifiers have been sold. Exactly for this reason there arose the earlier described skepticism of the editors. However the same criterion applies to the new 4B-SST power amplifier, weighing a good 25 kilograms, as for the BPS-25 preamp: Maintain the basic fundamentals and update details. Would you like an example? Once again in the new model the ingenious Quad-Complementary output stage has been maintained. In contrast to a simple arrangement, where a transistor transmits only half a wave of the signal, in this mixed NPN/PNP constellation the entire wave is transmitted by one pair, and therefore positive and negative half waves are identically processed resulting in a perfectly symmetrical signal.

For the current supply two 600 VA transformers are utilized, whose output energy is now filtered with almost 90,000 microfarads, which also represents a technical doubling of the previous model. No wonder that the calibration resistors became boiling hot during testing in the laboratory. With stable output of about 350 watts into eight ohms, all loudspeakers, no matter how adventurous the construction, should be readily driveable.

Quality of Reproduction

In our HIFI-TEST listening room several components were allowed to warm up for the competition - besides the Bryston BPS-25 preamp and the Bryston 4B-SST power amplifier, their predecessors the Bryston BP-25 preamp and the Bryston 4B-ST power amplifier, the No. 390 S Mark Levinson CD Player, and the outstanding Master Reference Clearaudio CD transport. For loudspeakers the Audiodata Elance II, connected with HMS Fortissimo cables, stands in first place when it comes to uncovering even the slightest differences. Of course all components were connected via the "Einpunkt" Sun Powerstrip (see accessory tip). Especially the preamp benefits from extended warm-up, a fact which applies to almost all high quality components. The first round was assigned to the predecessors which proved themselves, now as then, by their utmost measure of musicality. Whether Rapper Eminem or Mozart's "Abduction from the Seraglio" didn't matter at all because it was simply enjoyable to listen. Therefore what could be lacking? The answer was immediately provided by the brand-new duo, and the differences were not trivial. The bass attacks came into play with clearly more bite, and in the upper ranges the addition of silkiness and clarity likewise entered into the mix. The voice of the soprano Kiri te Kanawa won enormously in strength of expression. High point was the new Moby-Album 18, where the electronically produced sound expanses became larger, more brilliant, and depicted with clearer acoustical configuration. The pulsating bass was overwhelming. Additionally many details were audible which the predecessors, even during the most exacting test, simply suppressed. Within hours initial skepticism was replaced with the confidence that the performance of the Bryston BPS-25 preamp and the Bryston 4B-SST power amplifier clearly push their predecessors aside. They are the new reference and become the benchmark for other stereo amplifiers.

Summation

HiFi TEST has solved the riddle of the addition of the letter "S" to the Bryston type designations, it simply stands for "Sensational." The Bryston Company has programmed the success of the BPS-25 preamp and the 4B-SST power amplifier for years to come. What this stereo duo offers tonally has seldom been realized until now, and when, only at considerably higher prices. Bryston follows the course of time and adds a triumphant chapter to the manufacture of amplifiers - with a 20 year warranty.

Olaf Sturm

Translated from the German by Peter Ullman