EAR 834P phono preamplifier Measurements
The EAR 834P we received from Bob Reina arrived defective (it had extremely low gain). Since he'd clearly had no problem with it, we can only assume that it was damaged in shipment. EAR sent us a second, more recent sample. It was slightly different from the original unit: The front-panel level control had been deleted, and the front panel itself was far better finished. The interior layout was nearly identical, though the main circuit board (screen-printed with a "1996" copyright date as opposed to BJR's sample's "1995") was somewhat larger (with a larger case to accommodate it). There appear to be some minor changes in parts—particularly regarding the power supply electrolytics—but no radical alterations in the original circuit or its layout. The measurements below were taken on this latest version.
The EAR's voltage gain measured 49.2dB moving-magnet, 68.2dB moving-coil. These are very high values, particularly for the MM; typically, the gain in MM gain stages is 35–40dB, and 55–65dB in MCs. I don't anticipate this high gain to cause any problems, but I'd check to make sure that it won't overload my line preamp. Signal/Noise (ref. 1V output) for the MM setting was 65dB from 22Hz to 22kHz, 61dB from 10Hz to 500kHz (both unweighted), and 74.6dB A-weighted (results are for the right channel, which was noisier). The corresponding results for the MC configuration were 62dB, 60dB, and 72.2dB, respectively (left channel). Set to MM, the 834P's input impedance was 49.7k ohms in the left channel, 51k ohms in the right. The input impedances for the MC setting were 515 ohms and 516 ohms (L&R). The output impedance measured 524 ohms in the left channel, 538 ohms in the right.
Fig.1 shows the frequency response of the 834P, with the MM result displaced up by 1dB. The response in both modes is very similar, and shows a modest downshelving in the high frequencies that may slightly soften, but not dull, the treble. The crosstalk in fig.2 is relatively high on an absolute basis, but certainly lower than that in virtually any phono cartridge.
Fig.1 EAR 834P, RIAA error into 100k ohms (MM top, MC bottom) (0.5dB/vertical div., right channel dashed).
Fig.2 EAR 834P, crosstalk (from top to bottom at 20kHz): R–L, MC: L–R MM; R–L, MC; L–R, MM (10dB/vertical div.).
The variation of THD+noise with frequency (fig.3) is good. For the MC result, I've chosen to show the result for two input levels. As is usually the case with our phono-stage measurements, we make our primary measurement using an input that results in the minimum THD+N at 1kHz. This level was 2.2mV in the case of the EAR MC setting. This clearly minimizes the effect of noise on the reading, but does overdrive the MC stages at very high frequencies. The result with a 1mV input is also shown in fig.3; the 1kHz THD+noise is higher here, though not dramatically so. The 50kHz result is far better. The MM measurement shown was taken at an input level of 7.6mV.
Fig.3 EAR 834P, THD+noise vs frequency into 100k ohms at: (from top bottom) 1mV at 1kHz, MC; 2.2mV at 1kHz, MC; 7.6mV at 1kHz, MM (right channel dashed).
Fig.4 indicates the way the THD+noise varies with output voltage at 1kHz. The minimum level corresponds to the 2.2mV (MC) and 7.6mV (MM) inputs used for the THD+noise vs frequency and crosstalk measurements.
Fig.4 EAR 834P, distortion (%) vs output voltage into 100k ohms at 1kHz; MC (top), MM (bottom).
Finally, the overload points (1% THD+N) for the 834P were 69.2mV at 1kHz, 260mV at 20kHz, and 7.85mV at 20Hz, MM (equivalent to 22.8dB, 14.3dB, and 23.9dB). The MC figures were 7.4mV, 27.5mV, and 0.85mV, respectively (equivalent to 23.4dB, 14.8dB, and 24.4dB). These are reasonable though not exceptional figures.
The measured performance of the EAR 834P while not especially notable, is good; nothing in the results would preclude solid sonic performance with a high-performance analog phono source.—Thomas J. Norton