Mark Levinson No.331 power amplifier System
I auditioned the Mark Levinson No.331 amplifier in my 13' by 26' by 12' listening room. A doorway at the back of the room opens into our kitchen, adding a 25' by 15' area. CDs were played on a Krell MD-1 turntable, which drove an Audio Alchemy DTI jitter attenuator using a 75 ohm Silver Starlight digital coaxial cable. This unit fed either an Audio Alchemy DDE v3.0 HDCD$r-based D/A converter over its I2S bus or an Adcom GDA-700 D/A converter. Other sources included Day Sequerra FM Reference and Rotel RHT-10 FM tuners, and a Linn Sondek LP12/Lingo turntable with an Ittok arm and a Spectral moving-coil cartridge. The preamplifier was a remote-control Bryston BP-25MC.
I used two different bi-amplified loudspeaker systems to audition the Levinson. In both cases, the '331 was used to drive the system's main midrange-tweeter speakers. For comparisons of bass response, the '331 drove the system's subwoofer. In addition, Totem Model One minimonitors sitting on sand-filled Target R-1 stands, were used to audition the amplifier working with a full-range signal. The three systems were each placed at the same location: 4' from each side wall and 3' from the back.
The first loudspeaker system was based on a pair of Quad ESL-63s on Arcici stands serving as satellites, with the bass handled by a pair of 18" Bag End S-18 subwoofers. For this system, the BP-25's balanced outputs drove a Bag End ELF-1 Integrator electronic crossover set at a 90Hz high-pass frequency. Cogelco Yellow interconnects were run from the BP-25 to the ELF-1, with extra Cogelco pairs run to the power amplifiers. The Quads were driven by the No.331 via bi-wired Sumiko OCOS speaker cables. (The '331's second set of binding posts made biwiring easy.) A Krell KSA-250 was used to drive the subwoofers via Monster Cable. The ELF subs were placed in the corners of the room.
The second loudspeaker system was the Snell Type A Reference. AudioQuest Topaz single-ended interconnects connected the Bryston preamplifier to the Snell EC-200 line-level crossover, with Monster Cable interconnects used between the crossover and the power amplifiers. The EC-200's high-pass output fed the Mark Levinson No.331, which drove the Snell Reference Towers. The EC-200's bass outputs were connected to a Krell KSA-250, which drove the two Snell SUB 1800 subwoofers using Monster Cable.
Prior to any serious auditioning or specific comparisons, I broke in the No.331 amplifier with several listening sessions a week for three months, leaving the amplifier in Standby mode for the remainder of the time. This resulted in a 50-hour break-in, much less than the 300 hours Madrigal recommends. Even after several hours of driving the Snell Reference System to lease-breaking levels (fortunately, I own my own house), the No.331's adaptive biasing allowed it to run with barely warm heatsinks, much cooler than the KSA-250, which uses a steady high biasing of the output stage.Larry Greenhill