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This is only the first of a host of objections that can be raised against incorporating the "Neumann correction" in RIAA replay circuits. A second, already raised in these pages by John Atkinson (footnote 12), is that ultrasonic frequencies from record clicks will be less effectively suppressed. But the most telling criticism of the "Neumann correction," as described, is that its core assumption is wrong. The claim of a 3.18µs pole being added to the record EQ of Neumann cutters is inaccurate. Moreover, a detailed investigation of record cutting and replay shows the entire situation to be…
Sidebar: The Neumann 4th pole (sic)
Using the phrase "4th pole" to describe the addition of a further time constant to curtail the RIAA record EQ at ultrasonic frequencies is a misnomer. Talk of poles takes us into what will be unfamiliar territory for many Stereophile readers, so a brief—and necessarily simplified—explanation is given here.
Filter circuits are described by a mathematical equation called a transfer function, which in general form is a ratio of two polynomials (ie, power series) in a variable denoted s (s=jw, where w is angular frequency (2PIf) and j is the square…
Threshold is one of the longest-surviving high-end audio companies. Founded in the 1970s by Nelson Pass and René Besne, it was acquired by a large, publicly traded corporation in 1988. This had both positive and negative results in that Threshold was then able to expand its activities, adding the cost-effective Forté line of products, but energies were drained away from cutting-edge design. Besne left the company in 1991, while Pass resigned in 1992 to pursue other interests. (These blossomed into the Pass Aleph 0 amplifier reviewed by DO in March '95, Vol.18 No.3.)
Threshold's…
The Tape Output source selector on the remote has an ergonomic problem. Instead of having a button for each output source, you have to cycle through all of them to get to the one you want. For example, if you want Bal.1 and are set on Bal.2, you have to scroll through nine other source choices (one choice is "Tape Out Off") to get back to Bal.1. This is a major drag if you want to use one of your tape outputs as the signal feed to your surround-sound processor. Every time you change main input sources, you have to then cycle through the tape output choices to get that source into your…
Sidebar 1: Specifications
Description: Remote-controlled line-stage preamplifier. Maximum gain: 18dB. Output impedance: 150 ohms balanced, 49 ohms unbalanced. Input impedance: 10k ohms unbalanced, 20k ohms balanced. Frequency response: DC–100kHz ±0.05dB. Distortion: <0.002%. Signal/noise ratio: –118dB. Maximum output: 24V RMS. Sensitivity: 350mV for 3V output at 1kHz.
Dimensions: 17.6" W by 14" D by 3.5" H (preamp); 8.75" W by 12" D by 4" H (power-supply).
Serial numbers of units reviewed: 11389 (preamp), 11379 (power supply).
Prices: $5250 in black, $5350 in "silver pewter" (…
Sidebar 2: System
Analog sources in my large room included the Fanfare FT-1 and Magnum Dynalab Etude tuners; VPI TNT Jr. turntable with Power Line Conditioner, tripod pulley system, and an outboard flywheel on a Bright Star base mounted with the Graham 1.5-T and Clearaudio/Souther TQ-1 tonearms. The VPI HW-19 Mk.IV with Stand-Alone Motor Assembly on a Bright Star J-7 base mounted with a Clearaudio/Souther TQ-1 resides in my small room. Cartridges included the van den Hul MC-1 Super, Dynavector XX-1L low-output MC, Benz L04, Fidelity Research/van den Hul FR-1, Denon 103/van den Hul, and a…
Sidebar 3: Measurements
A full set of measurements was run on the Threshold T2 in its balanced mode, with selected measurements repeated in the unbalanced configuration. Unless otherwise noted, the results below are for the balanced mode.
The output impedance of the T2 at its line outputs measured 314 ohms (70 ohms unbalanced). Its (line) input impedance measured 10.6k ohms (just a little less unbalanced at 10.2k ohms). The above figures are for the left channel at the maximum setting of the gain control; the right-channel results were not significantly different, nor were the…
The Krell KPS-20i (KPS stands for "Krell Playback System") is essentially a CD transport and digital processor in one chassis. What make the KPS-20i different from a CD player are the unit's five digital inputs, which allow the KPS-20i to function as a digital/analog converter for external digital sources.
A CD player offers the potential of giving a similar sound quality for less than the price of a transport and outboard processor combination: with only one chassis, packing carton, power cord, and other items, a CD player costs less to build than a comparable pair of…
The DSP56002 is clocked at a blazing 66MHz, and has more computing horsepower than the DSP56001 used in previous Krell processors. Consequently, a single DSP56002 does the work of two DSP56001s. The digital filter section is located on the main printed circuit board, with the DAC and analog output stages mounted on a board stacked above the main pcb.
The digital-filter output is converted to an analog audio signal by four Burr-Brown PCM63 DAC chips. Four DACs are used for true differential operation: the digital signal is split into positive and negative phases in the digital domain,…
Sidebar 1: RH's System
I put the Krell KPS-20i at the front of my playback system, playing discs on the KPS-20i's integral transport. The KPS-20i also saw time driven by the Mark Levinson No.31 transport via AES/EBU cable, using the KPS-20i as a digital processor. Further, I drove the Mark Levinson No.30.5 (fitted with the HDCD decoder/filter) and the Sonic Frontiers SFD-2 Mk.II from the Krell's digital output to assess the KPS-20i as a transport. Of course, having these superb Class A processors on hand made them natural points of comparison for the KPS-20i.
I found that the KPS…