RMAF 2011: German Physiks, Abis, Memory Player
The $15k German Physiks Unlimited Mk II was the center point in this room. Showcasing a carbon-fiber driver, the specs are pretty standard for this price point: 88dB, 40hms, 32Hz-24kHz frequency response. What’s not is that all that is available in 360-degrees.
In general, this works pretty much as advertised. While there is very definitely a sweet spot, regardless of what the marketing literature says, the truth is that the sound field is very expansive. You can get up and walk around and the sound is very similar wherever you sit or stand. That said, the best stereo sound, at least from an imaging point of view, is in the traditional sweet-spot seat.
Stylish, minimalist, and if it wasn’t for that inverted driver sitting on top, the Unlimited Mk II would look vaguely architectural.
Another Memory Player was sending out the audio.
“Shuhgetsu” Model P-1120 (120wpc) amps from Abis with an integrated volume control. I’ve never heard of (or seen) these amps before, but found an interesting reference to something they incorporate, called NRF.
Negative Resistance Free (NRF) circuitry patented by Tetsuo Kawanishi, former associate professor at UEC Tokyo (The University of Electro-Communications), who designed this “Shuhgetsu” series amplifiers for SIBATECH.
Conventional high feedback amplifiers do not feed back perfectly. Such amplifiers eventually contain residual negative resistance where real part of impedance becomes negative in a certain high frequency range. A system containing negative resistance may oscillate or performs unsteadily resulting in producing excessive transient distortion to cause muddy the sound. When RF noise or the like gets mixed with such an amplifier, the system falls in further unstable conditions only to degrade sound quality.
In order to protect the circuit against this problem, ABIS “Shuhgetsu” amplifier is designed with NRF circuit to remove negative resistances generated in input and output impedances. As the result, original music signals are properly amplified. In addition, many high quality parts are used to enhance the quality of the circuit.
“Shuhgetsu” employs NRF regulated power supplies for both C-120 preamp and P-1120 power amp. Especially, the power supply built in the P-1120 mono block operates for both voltage amplifier stage as well as for power amplifier stage done first time in the world, so the power output 120W in actual feeling is equivalent to 240W from on-market products power amplifier stage of that are not operated on regulated power supply. Shuhgetsu therefore does not jeopardize transient response due to variation in output impedance that results in variations in power supply voltage.