Description: Tube stereo power amplifier. Tube complement: four EL34, four 12AT7. Inputs: One gold-plated RCA jack per channel. Outputs: 1 pair solid-metal gold-plated four-way speaker terminals per channel. Maximum power output: 85Wpc into 4 ohms, 20Hz-20kHz (13.3dBW). THD at rated output: 3%, 20Hz-20kHz. S/N ratio: 95dB at 120Hz. Input sensitivity: 1.1V for full output. Input impedance: 100k ohms. Output impedance: 0.9 ohms. Recommended load impedance: 3-8 ohms. Power consumption: idle, 175W; full power, 550W.
Dimensions: 15.75" W by 6.75" H by 12" D.…
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Sidebar 1: Specifications
Sidebar 2: Associated Components
LP playback: Linn Axis turntable, Linn Basik Plus tonearm (with stock Linn wiring), Benz Micro Glider phono cartridge.
CD playback: Enlightened Audio Design CD-1000 CD/LD combi player.
Preamplification: VTL 2.5, Anthem PRE 1L line preamp, Anthem PRE 1P phono stage.
Power amplifiers: JoLida SJ 502A integrated, Audio Alchemy OM-150.
Loudspeakers: NHT 2.5i, Joseph Audio RM-7si Signature on Lovan stands.
Cables: Interconnects: Synergistic Research Alpha and Looking Glass, XLO Pro Type 100. Speaker cables: Cardas Crosslink 1.
Accessories:…
Sidebar 3: Measurements
The VTL's protective cage was hot following its 60-minute, 1Ú3-power preconditioning test, if not unusually so for a tube amplifier. The bias of the right channel was found to be misadjusted during the distortion measurements. It was recalibrated, and all measurements made prior to the recalibration were rechecked and corrected, as necessary.
The ST-85's input impedance measured a high 114.8k ohms. Its output impedance ranged from 1 ohm to 1.08 ohms, depending on frequency and load impedance. This is not particularly high for a tube amplifier, but still…
The percentage of THD+noise vs frequency results (at 1kHz) plotted in fig.4 indicate reasonably low readings (by tube amplifier standards) across the audio band. The 1kHz THD+noise waveform is shown in fig.5 (at 2W into a 4 ohm load). The result is heavily second-harmonic. At 4W into 2 ohms (not shown) there is clear evidence of higher-order harmonics, but the second harmonic is still dominant.
Fig.4 VTL ST-85, THD+noise vs frequency at (from top to bottom at 1kHz): 4W into 2 ohms, 2W into 4 ohms, 1W into 8 ohms, and 2.83V into simulated loudspeaker load.
Fig…
The THD+noise percentage vs output power results at 1kHz are shown in fig.8, with one channel driven. The discrete clipping measurements are shown in Table 1. The results are shown for 3% THD+noise, since that is the distortion level at which VTL rates the ST-85's power. The output is just a little short of its rating with both channels driven into 4 ohms, but exceeds the spec with one channel driven.
VTL ST-85 Clipping
(3% THD+…
Fig.8 VTL ST-85, distortion (%) vs continuous output power into (from bottom to top): 8 ohms, 4 ohms, 2 ohms.
Table 1
VTL ST-85 Clipping
(3% THD+…
Most of us have at least some taste for gear that jumps out—for audio components whose sonic and musical distinctions are easy to hear from the start. In audio, unlike in the art of music itself, there's nothing wrong with being obvious.
Then there are such products as the grand-looking 890 amplifier ($4995) from Esoteric Audio Research, which had nothing of the obvious about it during its stay in my home. Voices didn't pop out. Groove noise didn't vanish. Textures were neither smoothed-over nor scuffed-up. Whites weren't whiter and colors weren't brighter, and I had to listen to…
Considering the Purcell music associated with the funeral of Queen Mary (I balk at a more specific title than that if only to avoid the ire of those who rightly observe that we don't know for sure what was performed on that miserable day in 1695), the recording I most enjoy is the one made by John Eliot Gardiner in the late 1970s (LP, Erato STU 70911). At the end of this recording of the March, the percussionist plays a roll on a kettledrum tuned to C, the sound of which is then left to fade naturally (ie, it isn't damped by the player). Bad amps—even enjoyable bad amps—èt this all…
Sidebar 1: Specifications
Description: Stereo tubed power amplifier with inout level controls. Tube complement: two 6AQ8, two 12AX7, eight KT90. Output power: 70Wpc into 8 (18.45dBW) or 16 ohms (21.45dBW). Power bandwidth: 15Hz-40kHz at <3.0% THD. Input impedance (measured at 1kHz): 55k ohms, unbalanced or balanced. Input sensitivity: 1.0V. Signal/Noise Ratio: 92dB (no ref. level specified).
Dimensions: 16" W by 7" H by 16" D. Weight: 60 lbs.
Serial number of unit reviewed: 013903.
Price: $4995. Approximate number of dealers: 24.
Manufacturer: Esoteric Audio Research/…
Sidebar 2: Associated Equipment
Analog sources: Linn LP12 turntable, Naim Armageddon power supply, Naim Aro tonearm; Rega Planar 3 turntable, Rega RB-300 tonearm; ZYX Airy S, Lyra Helikon Mono, Rega Elys cartridges.
Digital source: Sony SCD-777ES SACD/CD player.
Preamplifiers: Fi, Audio Note M2 Balanced; Audio Note AN-S2, Tamura L2-D step-up transformers.
Power amplifier: Fi 2A3 Stereo.
Loudspeakers: Quad ESL-989, Lowther PM6As in modified Medallion horns.
Cables: Interconnect: Audio Note AN-Vx, DNM solid-core (balanced), homemades. Speaker: Nordost Valhalla, Audio Note AN…
Sidebar 3: Measurements
I tested the EAR 890 using both its balanced and unbalanced inputs and its 8 and 16 ohm output transformer taps. The unbalanced voltage gain at 1kHz into 8 ohms ranged from a high 29.8dB (16 ohm tap) to 27.1dB (8 ohm tap), the balanced input offering 0.7dB lower gain than the unbalanced. Both inputs preserved absolute polarity; ie, they were noninverting. (The balanced input appears to be wired with pin 2 "hot.") The input impedance at 1kHz was a usefully high 55k ohms for both balanced and unbalanced inputs, and didn't vary with the position of the volume-control…