Bully Sound BSC-60s Stereo Amplifier And 100m Monoblock Update
The £6500 BSC-60s is a slightly lower power (60W/ch) stereo version of the BSC-100m monoblock amps (reviewed HIFICRITIC Vol. 6 No. 4). It has the same variable bias arrangement, and gets very hot indeed on the full 'Class A' setting. Not exactly self-effacing, it looks identical to the 100m, with a large and chunky case in black aluminium, plus an anodised front panel. Plenty of ventilation is provided around the heatsinks. Black and grey sections sit either side of a black centre that has the on/off pushbutton; a function light glows red in standby and green in operation. A bias selector switches between eco-mode (low bias), 50% bias, and 'Class A'. On the rear, four gold-plated loudspeaker binding posts (no specific bi-wiring provision here), and the inputs consist of either balanced XLR or single-ended/unbalanced RCA/phono inputs. A toggle switch can optimise grounding for single-ended/unbalanced use (as seen below).
Inside, one heatsink tower for each channel disperses all the heat generated. A single multi-tapped toroidal transformer has separate supply capacitors for each channel (50,000uF each). Six output devices per channel are used, which should be more than sufficient considering the relatively modest power output. It's configured to deliver the rated 60W 'Class A' output into an 8 Ohm load, although these 'Class A' credentials are not sustained into difficult loads. It will continue doubling its output power as the load is halved: 60W into 8 Ohms, 120W into 4 Ohms, 240W into 2 Ohms and 480W into 1 Ohm loads, but as it comes out of 'Class A' to drive more difficult loads, the sound quality is likely to alter subtly. This will probably affect the character of the amplifier depending on the characteristics of the specific loudspeaker. This power amplifier might not quite have the overkill construction of some other high end offerings, but it's nevertheless a substantial piece of engineering.
However, the 100m is simply better, with more driving torque, resulting in seemingly effortless power delivery within design constraints, and it consequently sounds more natural, dynamic, and musically interesting. The 60s sounds slightly more strained, just a little uptight, very slightly hard and not quite as focused or able to create as solid a soundstage, but the difference is really only really noticeable on direct comparison. Whereas the 100m can sound quite sublime, the 60s is merely exceedingly good.
That said, I'm not particularly happy with the noise performance. Although within the manufacturer's specifications, I feel this problem really does need addressing. I don't notice it at normal listening levels, but, depending on system and set-up, hum might become audible during quiet passages.
What really surprised me is the way it slotted into my system and continued to provide the same familiar sound I have spent decades carefully building my system to reproduce, while also adding a little extra interest to well-known discs. At its first attempt, Bully Sound has got straight to the crux of performance essentials, and provide a very musically cultured result.
This amplifier manages to sound light and nimble, yet still has the ability to provide thunderous power and drive difficult loads – a very neat trick. Twenty five years ago I might not have recognised its virtues in quite the way I do now, but those years have given me enough experience to learn exactly what's needed from a really good amplifier, and the Bully Sound delivers. This amplifier is one of the most musically satisfying on the planet, which makes it very competitively priced. But it's still a shame about the mild hum residual.
Bully Sound 100m Monoblock Update
Priced at £13,000 per pair, the Bully Sound BSC-100m is an impressive sounding 100W monoblock amplifier that we reviewed in Vol6 No4. However, it didn't quite measure up to the specifications: apparently a small grounding fault had created an unwanted feedback path. The units are now returned for reassessment.
The sound is now stronger, more natural, with better timing, transparency, stage width and even better grip and control. The soundstage has better focused images than before, and is now rich and graceful with great depth perspectives. The treble sounds airy and elegant with loads of detail, and the ability to create space around instruments can be unnervingly realistic.
These monoblocks also easily reveal different rhythmic patterns within the music, while holding the whole performance tightly together. Their ability to hold the attention by revealing new and previously unheard information continues to keep one listening, and the improvement demands that old recordings are revisited for rediscovery.
The BSC-100m shows very good control throughout the audio band. In the last review I reported that I preferred the sound on the medium bias setting, but since the grounding change it now reaches its greatest potential using full bias. The medium bias setting definitely sounds grainier in the treble, has a harder midrange and is no more transparent; in fact it's definitely a little rougher all round. I didn't have a chance to compare with the D'Agostino Momentum Stereo this time, but the improvement is definitely closing the gap.
Unfortunately the hum still hasn't been banished, and spectrum analysis showed it was unchanged. While it does comply with the manufacturer's specification, it's still too much in my opinion, and greater than its peers. Coupled to my 90dB/W loudspeakers there is little apparent hum in my preferred listening position, but it can be more obvious elsewhere in the room, and could be a problem with more sensitive loudspeakers. Designer Bret D'Agostino is working on this, and promises that new production will be fixed.