Australian Hi-Fi

Laboratory Test Report

- Steve Holding

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-oŸ 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 aŸecting 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 oŸered 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.

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