Laboratory Test Report
Readers interested in a full technical appraisal of the performance of the Transrotor Phono MC 8.2 Sym phono preamplifier should continue on and read the LABORATORY REPORT published on the following pages. Readers should note that the results mentioned in the report, tabulated in performance charts and/or displayed using graphs and/or photographs should be construed as applying only to the specific sample tested.
Graph 1 shows the frequency response of the Transrotor Phono MC 8.2 Sym phono preamplifier. Newport Test Labs had to use an inverse RIAA equaliser to produce this graph, and although it is a precision device, it does introduce some errors, so the errors in the response are both of it and the Transrotor Phono MC 8.2 itself. Also, because of the extremely low-level signals involved and the necessity to connect the Phono MC 8.2 to multiple items of test equipment, some mains hum inevitably creeps into the measurement. You should, therefore, ignore the ‘spikes’ in the response at 50Hz, 150Hz, 250Hz and 450Hz.
Despite the technical constraints of the measurement, you can see that the Transrotor Phono MC 8.2’s frequency response is very linear. Note that the vertical scaling is extreme, so the top of the entire graph represents a signal level of +2dB, and the bottom of the graph –2dB. So if we ignore those mains hum components, the frequency response of the Transrotor is from 10Hz to 40kHz ±0.3dB. Across the 20Hz to 20kHz audio bandwidth, it’s ±0.15dB. This is a superb result and means that the Transrotor’s response is not only audibly flat, but also superbly flat from a technical perspective. Had the lab used a more typical vertical graph scale, it would literally be ‘ruler-flat.’
Graph 2 shows the equalisation curve the Transrotor Phono MC 8.2 applies to incoming signals to correct for the RIAA equalisation applied when mastering vinyl records. This graph shows that Transrotor is not using the original 1954 equalisation specified by the
Record Industry Association of America (so you can see where RIAA comes from!) but the modified version of it that was introduced by the International Electrotechnical Committee in 1976.
This modified version (detailed in the IEC 60098 Technical Standard) added a fourth time constant to the original three that introduced a 6dB/octave roll-o in the frequency response below 20Hz, the idea being to reduce the levels of infrasonic frequencies generated by record warps and ripples and to prevent tonearm/ cartridge resonances from aecting both the amplifier and the loudspeakers. Although it’s good to see that Transrotor is using the newest version of the RIAA ‘standard’, it might have been nice if the company had oered the original RIAA standard as well, in the manner of some other manufacturers of phono preamplifiers.
Graph 3 shows the THD of the Transrotor when reproducing a 1kHz sinusoidal test signal. You can see the test signal at the extreme left of the graph, referenced to 0dB. There are only two harmonics visible above the noise floor.
The second harmonic, at 2kHz, is 100dB below reference (0.001%) while the third harmonic is a little lower down again, at around 103dB down (0.0007%). These harmonics are so low in level that they would not be audible, but even if they were, they’d make the sound of the 1kHz signal appear richer, fuller-sounding and more musical
because the second harmonic is the octave of the fundamental, and the third harmonic is the fifth above. Because of the musical relationships between the three signals, they would not be perceived as distortion per se — just good sound.
You can see on Graph 2 that the noise floor is spectacularly low. There is some mainsrelated noise (50Hz hum and harmonics) visible at the left edge of the graph, but the noise floor drops quickly to –110dB at around 400Hz, then to around –120dB at 6kHz, then down to around –130dB above 10kHz. This is the kind of noise performance we’d expect to see from an integrated amplifier. Note that this noise floor is calculated for each individual frequency — it is not the overall noise across the entire bandwidth. This noise level is reported as the signal-tonoise ratio in the tabulated results, and you can see that Newport Test Labs measured it as 74dB unweighted and 80dB A-weighted, with this last measurement matching Transrotor’s specification exactly — at least for the 40dB gain setting. It would be somewhat lower using the 65dB gain setting.
Newport Test Labs measured THD+N as being 0.01%, a result that is considerably better than Transrotor’s own specification of 0.03%, and it measured channel separation as 70dB, which is again far better than Transrotor’s specification of 62dB (though note that Transrotor refers to this specification as ‘crosstalk’, which is an oldfashioned word for the same thing).
The tabulated results show that Newport
Test Labs reported the input sensitivity of the Transrotor as being 485µV for a one volt output or, if you’d prefer to work solely with millivolts, 0.965mV for 2000mV (2V) out. Either way, there’s more than su¦cient gain for the Phono MC 8.2 Sym to accommodate even the lowest of low-output moving-coil phono cartridges, while at the same time also accommodating highoutput moving-coil cartridges.
It’s rare that we see a phono preamplifier that delivers better performance on our tests than the specifications for it claim. Indeed this could be the very first time, and that tells you a lot about the quality of the Transrotor Phono MC 8.2 Sym.