Sidebar 3: Measurements
I measured Lejonklou's Entity phono preamplifier with my Audio Precision SYS2722 system. The single, moving coil–compatible input preserved absolute polarity and offered 70.2dB of gain. (Though this is slightly lower than the specified 71dB, my measurement was affected by the voltage-divider action between the preamp's input impedance and the Audio Precision's output impedance of 20 ohms.) The input impedance was 90 ohms with it set to "90," 120 ohms with it set to "120," and 180 ohms with it set to "180," all values consistent from 20Hz to 20kHz. The output impedance is specified as 300 ohms; I measured 264 ohms at 20Hz, 295 ohms at 1kHz, and 297 ohms at 20kHz.
The error in the Entity's RIAA equalization (fig.1) was low, though there was a very slight, 0.2dB boost in the midrange. The channel matching was excellent overall. Channel separation (not shown) was >80dB in both directions across the audioband.
The Lejonklou's unweighted, wideband S/N ratio, measured with the input shorted to ground, was a very good 68dB (average of both channels), ref. 1kHz at 500µV. Restricting the measurement bandwidth to 22Hz–22kHz increased the ratio to 68.1dB in the left channel, 71dB in the right, and the A-weighted ratios were 74.9dB, left, and 77.7dB, right. Spectral analysis of the Entity's low-frequency noisefloor revealed that both the random noise components and AC supply–related spuriae were slightly higher in level in the left channel (fig.2, blue trace) than the right (red trace).
The Lejonklou Entity offers accurate RIAA equalization, very low noise and distortion, and a bombproof output stage. The limited overload margin at the top of the audioband means it will be best used with low-output moving coil cartridges. It is fair to note, therefore, that the preamplifier's manual does state that the maximum cartridge output is 0.4mV/400µV at the standard recorded velocity of 3.54cm/s. This would increase my measured overload margins by 2dB, and with a cartridge like Ortofon's Verismo, which has a nominal output of 200µV, the margins would be increased by another 6dB.—John Atkinson
Fig.1 Lejonklou Entity, response with RIAA correction into 100k ohms (left channel blue, right red) (1dB/vertical div.).
Fig.2 Lejonklou Entity, spectrum, DC–1kHz, of output ref. 500µV input (left channel blue, right red, linear frequency scale, 20dB/vertical div.).
The Entity's overload margin (ref. 1kHz at the standard MC level of 500µV) was a very good 14dB at 20Hz and 1kHz, but dropped to 2.2dB at the top of the audioband. The Lejonklou offered very low distortion. Fig.3 shows the spectrum of the preamplifier's output reproducing an input signal of 1kHz at 500µV. The only distortion harmonic that can be seen above the noisefloor is the third, at –96dB (0.0015%). This very low distortion did not increase in level when I reduced the load impedance to the current-demanding 600 ohms. Increasing the input to 2mV, 2dB below the level where the Entity's output clips, actually reduced the level of the third harmonic by 10dB (fig.4), though the second harmonic makes an appearance at a still vanishingly low –103dB (0.0007%). The Entity also offered a low level of intermodulation distortion, even just below clipping into 600 ohms (fig.5). The second-order difference product lay just above –70dB (0.03%).
Fig.3 Lejonklou Entity, spectrum of 1kHz sinewave, DC–10kHz, into 100k ohms for 500µV input (left channel blue, right red, linear frequency scale).
Fig.4 Lejonklou Entity, spectrum of 1kHz sinewave, DC–10kHz, into 100k ohms for 2mV input (left channel blue, right red, linear frequency scale).
Fig.5 Lejonklou Entity, HF intermodulation spectrum, DC–30kHz, 19+20kHz into 100k ohms for 5mV peak input (left channel blue, right red, linear frequency scale).
