Sassy and Phantasy share a clutch of design and utility principles. They share very little, however, in sound. Sassy wakes up almost instantly, ringing like Phantasy, for a dozen seconds to a minute, but from the ON, spits a strong signal that needn’t a warm up. Phantasy clinks and clunks like an old car for a bit; Sassy purrs from the get-go, lickety split.
Phantasy cools signals, clarifies, rings; it plays music like you may not have heard before, or may not have heard in a long time. Sassy warms up music as you expect a hybrid design to do; and it does so at almost no expense when under load.
Which means that, unlike Phantasy, it doesn’t really have a sweet-spot headphone or earphone. I note mostly stable loaded signals at volumes of up to 50%, with minor frequency aberrations from 20Hz – 20.000Hz. And I note a ~50% rise in harmonic distortion going from unloaded to high-current loads like the Earsonics SM2 and Audio Technica ES7. 50% is practically nothing. Astell & Kern’s AK380 THD base rises by ~22.000x. Of course, it starts much lower than Sassy’s, but still. Sassy’s unloaded base THD numbers are high, reaching 10x that of ALO Audio’s CDM – loaded!
I measure unloaded base THD levels at 3,08% at 50% volume, rising to 3,3% when driving the 600Ω DT880, 4,93% when driving the Earsonics SM2, and 5,18% when driving the Audio Technica ES7. IMD is both similarly high, and similarly load agnostic. Base levels of aberration are high, but they don’t ratchet up quite like they do through most amplifiers. And, assuming you keep the volume pot below 50%, they commit few to no audible boners.
Hardcore valve fans will probably call Sassy’s warmth mature. Sassy doesn’t bloom. It doesn’t peal when hitting high frequencies. It’s tubey, but tempered. Anything but sassy.
Sassy isn’t as warm or goofy as, say, the Woo Audio WA3. It doesn’t bloom in any frequency. Forward-edge ring is pretty high, but this is valves we’re talking about. Stereo signals congeal somewhat in the bass and lower mids. Consequently, highs are clearer than they have any right to be considering Sassy’s proclivity for warm harmonic distortion. In that respect, they resemble, though not slavishly, the clarity and character of Jaben’s wonderful GoVibe Porta Tube.
Warm lows are centrally grounded, and extrude the least stereo detail in the entire frequency range. But their warmth, smoothness, and deep anchor pull everything together.
Sassy’s volume pot controls a wide volume range in a pretty short turn. I listen most often to volumes of around 25% (DT880), 15% (Ultrasone IQ, Grado PS1000, Audio Technica ES7), 20% ZMF headphones. Like Phantasy, low volumes experience noticeable balance lean, in my case, to the left channel. For that reason, sensitive headphones and ears may find it hard to achieve absolute channel balance at comfortable listening levels. A good bed-time rig Sassy and the Shure SE846 or Ultrasone IQ do not make. I’m good with older recordings at that volume through the PS1000 and IQ, but only just.
So maybe the DT880/600 is Sassy’s sweet spot? Sensitivity wise, perhaps. It is my opinion that the PS1000, whose strangely sucked out (or up?) high midrange, needs a good grounding. Sassy provides the warmth necessary whilst avoiding splash, bloom, and other rowdiness you sometimes find in high-distortion valve amps.
And I should explain a bit more about that warmth. It’s not a top-down veil. Dear God, no. Tones are clear, just not bell-like. It’s a chamfered edge, smoothing out the join between noise and stereo detail. It’s a natural warmth, something you recognise at a quiet jazz lounge. But it’s warmth. For that reason, I reckon Sassy is less well adapted to the fast, the violent; it suits complicated, but moderately paced compositions from classical to jazz and vocal, and folk instrumental and rock. But stereo-detail started trance and EDM heads may be better suited by a number of other amplifiers.
If you’re willing to sacrifice clarity and accept IDM and THD levels of up to 5%, Sassy can put out 100dB of signal to noise, and 99dB of dynamic range. Impressive for a valve amp of any flavour. Sassy gets loud, and it stays pretty stable. It’s warm, but not too warm. In its own way, it is both less and more tubey than Phantasy. Less: Phantasy is brighter and subjectively clearer. More: Sassy is warmer. But because it holds a stabler signal to all loads, it is more suitable to a wide variety of headphones.
Which is the safer Phatlab amp? Gosh, Sassy gets the job done with minimal fuss. It is warm, and stable, but for me, less engaging. I love bright. And while Sassy doesn’t fall off with low pass filters or anything, its aberrations stack up for a truly nice listening experience. Nice when you’re looking for a bit of warmth is one thing. Nice when you’re looking for accent is another. It’s a good experience. Sassy is made as well as any battery powered amp out there – that is, as long as you strike Phantasy off the list. It’s got nice lights and Cylon detailing. It’s the tubey sound you probably expect from a hybrid tube amp. Getting used to it is like pouring milk on your Wheaties.
Well done. But definitely not sassy.