Description: Single-chassis, remote-controlled, full-function solid-state preamplifier with integral moving-coil phono stage. Inputs: 6 balanced line (XLR), 1 unbalanced line (RCA), 1 balanced phono (XLR). Outputs: 1 balanced (XLR), 1 unbalanced (RCA), 1 headphone (1/4" phone jack). Tape/processor loop: unbalanced (RCA) inputs and outputs. Input sensitivity: 250mV for unity gain. Input impedance, line: 10k ohms, all inputs. Input impedance, phono: 8 user-selectable levels, 10–1k ohms. Output impedance: 66 ohms. Frequency response: 0Hz–>200kHz. Line-stage gain…
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Sidebar 2: Associated Equipment
Analog Source: VPI HR-X turntable & tonearm, Lyra Titan cartridge.
Digital Sources: Burmester 001, Ensemble Dirondo CD players.
Preamplification: VTL TL-7.5 line-stage preamplifier; Sonic Euphoria PLC, Placette Remote Volume Control passive line stages; Ensemble Fonobrio, Sutherland PhD phono preamplifiers.
Power Amplifiers: VTL S-400, Simaudio Moon Rock, Mark Levinson No.20.6 monoblocks.
Loudspeakers: Thiel CS6.
Cables: Nirvana S-X Ltd., Audience Au24, Nordost Valhalla, Silversmith Silver, interconnects & speaker cables. AC:…
Sidebar 3: Measurements
Looking first at the Burmester 011's phono input (assessed at the tape-monitor outputs, and set to RIAA), the input impedance was 886 ohms at 1kHz when set to 1k ohm, and it didn't invert signal polarity (with pin 2 of the XLR jack driven by the hot phase). The RIAA equalization was very accurate, with just 0.1dB of positive error apparent in the upper bass and 0.15dB of rolloff at 20kHz (fig.1). The ultrasonic bandwidth was sensibly curtailed, the –3dB point lying at 90kHz, though the low frequencies rolled off very slightly, the output at 20Hz lying at –0.5dB.…
A thorough exploration in a magazine article of such a pervasive and complex topic as vibration control in audio systems is next to impossible; vibration and sound are so intimately bonded that it would be very easy to extend this discussion to just about any area of interest in audio. My intention here is simply to lay a foundation for understanding the basic mechanical forces affecting our quest for improved sonic fidelity, and in the process provide the tools for anyone to achieve good, practical vibration control in his or her system.
The plethora of vibration-control products on the…
How does all this relate to mechanical vibration? I believe progress in audio design has reached a point that demands serious attention to these and other subtle interactions---along with the more obvious variables---if we are to further reduce the "electronic" signature in reproduced music and move toward a more convincing re-creation of the real thing. This is true whether one is dealing within the electrical, mechanical, or acoustic arenas. From a practical standpoint, the time and frequency domains are alternate frames of reference, and most real progress in sound reproduction is being…
A Road Map
In order to keep things in focus, I will explore the effects of vibration on audio systems by examining how resonances interact with each of the major elements---floor, stands, platforms or shelves, components---and the various means of connecting them. Throughout our discussion I'll be referring to large torsional, or twisting, forces on structures, as well as significant displacements vs small movements. However, these are only relative comparisons. On an absolute scale, all of the vibration interactions in a typical audio system are very small (except for some room and…
In order to keep things in focus, I will explore the effects of vibration on audio systems by examining how resonances interact with each of the major elements---floor, stands, platforms or shelves, components---and the various means of connecting them. Throughout our discussion I'll be referring to large torsional, or twisting, forces on structures, as well as significant displacements vs small movements. However, these are only relative comparisons. On an absolute scale, all of the vibration interactions in a typical audio system are very small (except for some room and…
Removing the many sources of vibration is impractical, so we must next isolate our rigid structure from floor- and stand-borne vibrations. The concept is simple, but practical attempts to address these two separate aspects of vibration control are often mixed together in the mistaken assumption that, since the physics of vibration in rigid bodies and suspensions share several traits, similar criteria should be followed for the design of each.
One example of this misconception, frequently applied in audio, is the use of massive slabs of granite or marble alone. Many audiophiles expect that…
Platform Construction
Very few structural materials deal efficiently with the requirements of both rigidity and damping. Some materials address one aspect while degrading the other. Therefore, better performance is usually obtained by a composite approach to platform or shelf construction. Mass can be a desirable quality in a material used for equipment supports as long as it contributes to dynamic rigidity. But excess mass that does not aid the cause of stiffness may actually be detrimental, as it can cause a reduction in the platform's resonant frequency, requiring extra damping…
Very few structural materials deal efficiently with the requirements of both rigidity and damping. Some materials address one aspect while degrading the other. Therefore, better performance is usually obtained by a composite approach to platform or shelf construction. Mass can be a desirable quality in a material used for equipment supports as long as it contributes to dynamic rigidity. But excess mass that does not aid the cause of stiffness may actually be detrimental, as it can cause a reduction in the platform's resonant frequency, requiring extra damping…
This may be an appealing concept, but it just doesn't work that way. Certain ambitious advertising campaigns for these devices make it sound as if all the bad vibes will be sucked out of your audio gear as if by a hose containing a one-way check valve (often made of exotic materials and special shapes), while simultaneously preventing any floor or rack vibrations from coupling to the component via the cones. This idea is misleading at best, even though rigid coupling can play a critical role as an adjunct to an overall vibration-reduction plan incorporating isolation and damping. But before…
For those fortunate enough to have concrete floors, the modal waves are spread out, and the peaks of the waves are far apart compared to those in the platform or stand. From the point of view of the platform, it would be similar to driving over a broad speed bump. You'll notice it as a gentle rolling, but nothing like hitting a sharp, narrow bump. In other words, most vibrations transmitted to the floor, from whatever source, will couple directly through the cones without much amplification of the modal activity from the floor. In any event, there isn't a whole lot we can do about floor…