Description: Stereo, tubed, push-pull, class-AB amplifier. Tube complement: four KT77, two 12AU7, two 12AX7. Power output: up to 46Wpc into 8 ohms (16.6dBW), up to 51Wpc into 4 ohms (14.1dBW), both at 0.5% THD. Frequency response: 8Hz–50kHz, +0/–0.5dB (8 ohm load). Input impedance: 50k ohms. Output impedance: 1.6 ohms. Sensitivity: 1.2V RMS for 40W output. Voltage gain: 20.8dB.
Dimensions: 9" (230mm) W by 8.5" (220mm) H by 14.5" (370mm) D. Weight: 9.7 lbs (4.4kg).
Finish: Black, silver.
Serial number of unit reviewed: Z40059.
Price: $5800.…
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Sidebar 1: Specifications
Sidebar 2: Associated Equipment
Analog Sources: AMG Giro, Palmer 2.5 turntables; AMG 9W2, Audio Origami PU-7 tonearms; AMG Teatro, EMT TSD 75, Mighty Cala Sound TNT 15 moving-coil cartridges.
Digital Sources: Mytek HiFi Manhattan II DAC, Integra DPS-7.2 DVD player (used as CD transport).
Preamplification: Auditorium 23 (for EMT TSD 75), Bob's Devices CineMag 1131, Dynavector SUP-200, Lounge Audio Copla JFET-MC step-up-transformers; Lounge Audio LCR Mk.III RIAA, Parasound Halo JC 3+, Tavish Design Adagio phono preamplifiers; Linear Tube Audio microZOTL2.0, Pass Labs HPA-1, Woo…
Sidebar 3: Measurements
I performed a full set of measurements on the Linear Tube Audio ZOTL40 Mk.II, using my Audio Precision SYS2722 system (see the January 2008 "As We See It"). The ZOTL40's voltage gain into 8 ohms measured a lower-than-average 21.1dB from both its Direct and Volume Control unbalanced inputs, and both inputs preserved absolute polarity (ie, were non-inverting). The Direct input impedance measured 44.5k ohms at low and middle frequencies, dropping to a still high 39k ohms at 20kHz. Via the Volume Control input, the input impedance was lower, at close to 23k ohms…
Jim Austin auditioned the Huron firmware update in October 2017 (Vol.40 No.10):
PS Audio's DirectStream digital processor is unusual in that, via firmware, it can be upgraded not only functionally but sonically. This is possible because, instead of by hardwired, off-the-shelf chips, its digital processing is done by a field-programmable gate array (FPGA). Within the constraints of the hardware, the designer is thus free to explore new ideas by reprogramming the FPGA, and to implement the effective ideas by disseminating firmware updates. A few other companies offer firmware-upgradable…
To accompany my review of the Dan D'Agostino Master Audio Systems Progression monoblock amplifier elsewhere in this issue, I talked to Dan D'Agostino about the amplifier's design. I started by asking him what were some of the major differences between the Momentum and the Progression monoblocks?
Dan D'Agostino: I took the best parts of the Momentum's more sophisticated and complex circuitry and put them in the Progression, without using the same high parts count. Each stage of the Momentum's gain amplifier is separate, with input stage and driver stages on separate rails. All of the…
For as long as I've known about high-end audio, I've put Dan D'Agostino, co-founder of Krell, on the same pedestal reserved for the likes of Frank McIntosh, Saul Marantz, Avery Fisher, H.H. Scott, and Sidney Harman. The reason is simple: Dan's the man whose achievements at Krell led me from the harsh sound of my first high-end amp into another dimension, one of truly musical sound reproduction.
I still recall the layout of the room where I first met D'Agostino—at an audio show, years before I began writing for Stereophile. I introduced myself in a trembling, fan-boy voice. (I did the same…
Returning to Morlot and Seattle's Rite, I confirmed that while the sound was a touch warmer than neutral higher in the range, timbres were absolutely believable with timpani and bass drum. Further listens to recordings of percussion, cello, and double bass confirmed that, through my Wilson Audio Alexias, the Progressions excelled at conveying low pitches with more tonal accuracy than I was accustomed to.
I also began to realize that while my reference Pass Labs XA 200.8 monoblocks sound gorgeous, and convey a special glow around the edges of each note, the Progressions illuminated each…
Sidebar 1: Specifications
Description: Solid-state monoblock power amplifier using bipolar output devices. Input: 1 balanced (XLR). Power output: 500W into 8 ohms (27dBW), 1000W into 4 ohms (27dBW), 2000W into 2 ohms (27dBW). Frequency response: 1Hz–200kHz, –1dB; 20Hz–20kHz, ±0.1dB. Voltage gain: 30dB. Input impedance: 100k ohms. Output impedance: 0.15 ohm. THD, 1kHz at 500W into 8 ohms: <0.15%. Signal/noise: 105dB, unweighted.
Dimensions: 18" (460mm) W by 7.5" (190mm) H by 20" (510mm) D. Weight: 150 lbs (68kg).
Finishes: Black, Silver.
Serial numbers of units reviewed:…
Sidebar 2: Associated Equipment
Digital Sources: dCS Paganini SACD/CD transport & Rossini DAC & Scarlatti Clock; Oppo Digital BDP-93 NuForce Edition universal BD player; Apple MacBook Pro with Intel i7, SSD, 8GB RAM; external hard drives, USB sticks.
Power Amplifiers: Pass Labs XA200.8 monoblocks.
Loudspeakers: Wilson Audio Specialties Alexia.
Cables: Digital: AudioQuest Diamond (FireWire, Ethernet), Wireworld Platinum Starlight Ethernet, Nordost Odin 1 & 2 & Valhalla 2 (USB). Interconnect, Speaker, AC: Nordost Odin 2.
Accessories: Grand Prix Monaco rack…
Sidebar 3: Measurements
I initially measured one of the Dan D'Agostino Master Audio Systems Progression Mono monoblocks (serial no. PMO26P) with my Audio Precision SYS2722 system (see the January 2008 "As We See It"). Before doing any testing of a power amplifier, I precondition it by running it at one-third its specified power into 8 ohms for 60 minutes. This power level results in the highest thermal stress on the output devices of an amplifier having a class-B or class-AB output stage. After an hour driving 167W into 8 ohms, the temperature of the Progression's top panel and heatsinks…