Authorized Reprint from

Guide to Home Theater
Vol. 4, No. 5
June 1998

I like monoblocks. They're usually lightweight compact, and easy to schlep around, and Bryston's latest entry in the monaural amp sweepstakes is especially enticing. Not only is it bantam-size, it's also designed to bolt directly onto the back of your speakers. Still, beautiful as small might be, power amplifiers are about delivering current. Can Bryston's diminutive contraption put out? Let's buy them dinner take 'em out to a movie and find out.

Tiny Town Tour

Most amps are big, rectangular boxes, but the Powerpack 120 is a small rectangular box. Over half of it's top surface is heatsink. Below these fins are a ground-lift switch, green power LED, input-level adjusdtment screw, balanced/unbalanced input selector, RCA single-ended inpu, XLR balanced input, IEC power-cord receptacle, power switch, and a pair of five-way speaker terminals. The speaker terminals are gold-plated circular dealies very similar to the ones on the Cinepro 3k6 I reviewed in the January 1998 issue. Luckily, I always keep a quarter in my pocket for tightening down variations on the five-way bindng-post theme.

The Powerpack 120's audio circuitry and power supply are very similar to the Bryston 8B's. There are four gain stages: three for current, one for voltage. The circuit topolgy is fully balanced and complementary throughout. Especially interesting is Bryston's use of PNP and NPN bipolar transistors in pairs for each half of the last current gain-stage. Apparently this arrangement produces a better transfer function and a more linear response. The first current gain-stage also has some voltage gain capacity, so the voltage stage doesn't have to supply as much output swing.

Input-impedance worrywarts will be pleased to know that the variable resistor that controls theinput sensitivity is placed after an input buffer, so the impedance doesn't change with input level. Finally, the company directed special attention to reducing high frequency distrtion. Unlike many amplifiers in which distortion at 20 kHz is is 20 times the level at 1kHz, the Powerpack 120's distortion level at 20 kHz is only three times what it is at 1kHz.

Installation was effortless. (I feel very formidable lifting three amplifiers without so much as a grunt.) In my home-theater setup, I used the single-ended RCA inputs; in my stereo room, I tried the balanced XLR connections. The ground-lift switch was useful in the home theater installation. Even with all the amps powered from the same dedicated outlet, I heard hum if the grounds weren't lifted.

There were no unruly turn-on noises, but the Powerepack 120s did sort of "burp" about 15 seconds after turnoff. Chris Russell of Bryston attributed this to a power supply artifact during shutdown. According to Bryston, the current production models have a relay to eliminate this phenomenon.

Lillipution lollapalooza

The Bryston Powerpack 120 night be physically exiguous, but it delivers Brobdingnagian sound. (Gotcha lookin' for the Webster's yet?) The sound is big - very big. This amp excels at preserving low-level details and subtle musical cues. Whether it's the whisper of a diva's skirt sliding across an operahouse floor or the walla walla of a discrete surround-sound crowd, the Powerpack lets you hear into the mix in a way that's usually the exclusive province of megabuck amps. In this regard, the Powerpack nearly equals my class AAA reference, the Pass Aleph 1.2. The Bryston's low-level finesse translates into involving sound. It draws you into music and soundtracks; subtle cues that many amps blur into oblivion are prserved for your enjoyment.

While it isn't as lush or romantic as a tube amp, the Bryston is still quite musical. Acoustic guitars and saxophones have just the right amount of warmth, sparkle, and sheen. Voices have a natural quality, especially on DTS soundtracks. Only when I compared it directly to the Pass Alepha 1.2 did it sound a bit matter-of-fact. Massed strings have slightly more edge through the Bryston. If you speakers err on the bright side of the musical spectrum, the 120s won't help push the back toward neutrality.

While the Bryston has less mid and low-bass "slam" than the massive, multi-channel Cinepro 3k6 I reviewed in the January issue, it still has reasonablygood low-bass extension and weight.It can still rock your world with boombastic sources. Though it doesn't exhibit the dynamic ease of a high-end amp, the Powerpack does pretty well for 120 watts into 8ohms, preserving the leading edges of transients nicely on such explosive sountracks as The Long Kiss Goodnight.

Only dynamic peaks are wanting compared with the high-power Cinepro. The 3k6 handles bombast with no sense of strain, while the Bryston becomes a wee bit hard and never gets quite as loud. In addition, midrange dynamics are not as effortless or as seemingly unlimited as the Cinepros when it comes to dynamics, nothing succeeds like more power.

The Powerpack 120s upper-frequency presentation is mighty fine. Piccolos, triangles, and those all-important birds twittering in the rear channels have a realistic, airy quality. The Bryston's high end extension clearly outclasses that of the Marantz MA-500 monoblocks, which sound much softer with less extension. The Bryston is nearly the equal of the Boulder 500AE in top-end extension. Only the Pass' extra sweetness and sauvity on top clearly best the Bryston.

Depth rendition is acceptable, especially for a modestly priced solid-state amplifier. Within my current amp hierarchy, the Bryston betters both the Marantz MA-500 and the Cinepro 3k6 in dimesionality, but the (vastly more expensive) Pass Alepha and Boulder 500AE are both superior in this regard, especially on sounds eminating from way back in the mix. The Bryston sound-stage width is not as extended as those of the Pass, Boulder, or Cinepro, but it's the equal of the (less expensive) Marantz monoblocks.

The Bryston's electronic texture and grainare quite similar to the Cinpro 3k6, but the Pass Alepha is substantially more liquid. The Boulder 500AE also has less grain than the Powerpacks. Trailing the group is the Marantz MA-500, which sounds ever so slightly electronic in comparison to the rest .

The Cinepro 3k6s and Bryston 120s similar prices ($3499 for the 6-channel Cinepro, $3750 for five Powerpacks) invite direct comparison. If acurate dynamic presentation is your bailiwick, the Cinepro is a clear winner. It has enough power to deliver all the goods (in fact, just about any goods). But if inner detail and low-level information float your boat, the Bryston is the obvious choice. The Powerpacks deliver an amazing ammount of information, enough to beguile almost anyone. They also have greater dimensional capabilities, additional top-end extension, and a slightly more natural harmonic timbre. For folks like me, with long ingrained audiophile sensibilties, the Brystons have great appeal.

End of the Road

The Powerpack 120s are really nifty little amps. They are easy to set up and can be shoe-horned into tight spaces. In addition, they include an amazing 20-year warranty to the owner including one-way shipping. each amp even comes with its own test sheet. On top of these perks, the 120s are fine performers they excel at dredging up oodles of low-level information, their high-frequency extension is excellent, and they're delightfully harmonically neutral. In some situations you might wish for additional power, but for any speaker with THX-standard sensitivity, the Powerpacks have adequate drive for everything but multiple nuclear-warhead detonations.

Verdict: Solid Class AA performance at a reasonable Class AA price. I Like 'em; as a matter of fact, I like 'em so much, I think I'll go carry a couple around the room right now.

We invite you to experience the Bryston SST² Series amplifiers

20 Year Warranty - A Generation of Music