Linn Linto phono preamplifier Measurements
As Wes Phillips found, the Linn Linto was astonishingly quiet, with an A-weighted S/N ratio (ref. 500uV input at 1kHz) of 85.3dB. Unweighted, with a broad measurement bandwidth of 10Hz to 500kHz, the S/N ratio dropped to 66.5dB, which is still excellent. Its voltage gain in the high setting (the only one I measured) was 62dB rather than the specified 64dB, probably due to the 25 ohm source impedance of the Audio Precision System One. The difference is negligible.
The input impedance measured 165 ohms at 1kHz, slightly higher than spec, while the output impedance was a low 113.5-114 ohms across the band other than at very low frequencies, where it rose to 228.5 ohms. This will not cause any audible problems with normal preamps possessing input impedances above 2k ohms or so.
The Linto's RIAA error, measured at an input level of 1mV (1kHz) is shown in fig.1. The very slight (0.25dB) downtilt from 100Hz to 20kHz might just be audible, but the Linn preamp is otherwise flat. The channels match to within 0.07dB across the audio band, except in the low bass where the right channel peaks up slightly, to +0.25dB at 25Hz. As is usual with an RIAA de-emphasized design, the channel separation (not shown) increased with increasing frequency, reaching 90dB or so in the top audio octave. It was still better than 60dB in the bass, which is more than sufficient.
Only when it came to input overload did the Linto offer sufficient rather than stellar performance. Its overload margin at 20Hz (ref. 50uV) was 20.3dB, which is fine, but it dropped at higher frequencies to 16.8dB (1kHz) and 16.3dB (20kHz), which is only adequate. The red overload LED didn't illuminate until a 20dB overload at 1kHz had been reached. However, as the manual points out, if anyone is using a highish-output MC cartridge with the Linto, an internal link can be cut, which reduces the gain by 10dB and, all things being equal, will increase the overload margin by the same 10dB. When I tried the Linto in my own rig, which features a well-used Arkiv cartridge, the telltale LED stayed green.
Both of these phono preamps offer generally excellent measured performance. I could recommend either.
Fig.1 Linn Linto, RIAA error into 100k ohms at 1mV/1kHz input (bottom) and 100mV (top) (right channel dashed, 0.5dB/vertical div.).