Phantasy has the potential to sound very good; spritely, limber, and light. If that’s your schtick, Phantasy may be your fantasy. But it is beset by impedance mismatch issues. Many SET amps exhibit the same issues. For that reason, they usually have one, or perhaps two, headphones to which they are perfectly adapted and marketed. The rest is the luck, or ill-luck, of the draw.
The sweet spot for Phantasy appears to be headphones with impedance swings of over 100Ω. At that level of resistance, Phantasy kicks out flat signals with high dynamic ranges. Stereo separation is middling, with channel bleed attacking frequencies somewhat dependent on the headphone. But you knew that. That’s what SET amps are known for. Feeding the DT880/600 or T1, Phantasy combines stereo images most in the upper most frequencies. I like that bleed, you may, or may not.
Assuming all its ducks are in order, Phantasy is tubey, but not smarmy. Unlike many of its SET colleagues, it isn’t indiscriminately warm. It rides a fine line between ample harmonic distortion and bell-like clarity for a sound I consider truly beautiful. At high volumes, sizzling IMD ramps up fast through the DT880 and other headphones. I've found that the sweet spot is below 50%, at which IMD and other artefacts are nominal for an amp of this sort. But IMD and THD are part and parcel of the SET experience. I listen to the DT880/600Ω at hi-Z volumes of about 20%, so volume headroom isn’t a problem.
Choosing the right Z-setting is important. High Ω headphones really are stabler, and sound fuller when the hi-Z setting is engaged. Conversely, low-Ω headphones are marginally stabler when low-Z is engaged. The most dramatic evidence of this is the DT880 (red lines), which, in the RMAA graphs below, shows no bass and no highs in low-Z, and a tasteful high-pass filter when set to hi-Z.
Interestingly, no matter the Z setting, Phantasy rolls off the lows. Through the DT880, a low-Z setting rolls both the highs and the lows. A hi-Z setting rolls lows off beyond 100Hz at a clip of 4dB at around 50Hz. This helps prop up Phantasy’s bell-like sound.
Which is to say: Phantasy is an amp with a definite sound. I happen to like it very much. But there is ample evidence that its design limits the useful range of headphones to which it is suited. I wish it were as stable with the Grado PS1000 or Ultrasone IQ as it were with the Beyer DT880. But sometimes, flaws endear.
To each his own.
The following Rightmark Audio Analyzer tests were conducted through this equipment.
Source: Phatlab Audio Phantasy
ADC: Lynx Studio HILO LT-TB
Computer: 2012 27" iMac
Cables: 1,5m Hosa Pro 3,5mm stereo to dual 3-pin XLR (around 8$); and/or bespoke y-split 2,5 TRRS to dual 3-pin XLR made by Musashi Sound Technology.
24-bit all loads results @+6dBV - headphone output
PHAntasy is an amp chock full of proviso. No, it isn't able to keep signals stable across a wide selection of headphones. And the ones it stably drives require the right Z-setting. Usually I am hard on amps that don't perform stably across a large range of headphones. But PHAntasy is obviously not designed for earphones, or for portable headphones. It's not a small amp. It handles, looks, and feels like a HiFi component. While I wish it spat stabler signal to Grado-class headphones, the subjective sound is clear and just tubey enough. The sweet spot really is 300 and 600Ω headphones. And with them, PHAntasy spits a bright, clear, and lush sound.
It's an amp that, when in its groove is hard to fault, but an amp that, when not in its groove, is quixotic.
All in all, intriguing and unforgettable.