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Adjust+ Part II
Speed accuracy / Wow & Flutter
Arm Low Frequency resonance
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From Hi-Fi World - October 2008 issue

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Right Angle

drfeickert_test_level

 

Modern technology comes to the aid of the LP with Adjust+, a way of adjusting the vertical alignment of your cartridge for better sound. In the second and final part of his review, Noel Keywood delves deeper into its capabilities...

 

Last month I looked in detail at the primary functions of the Adjust+ software, namely that of setting cartridge verticality (or horizontal tracking angle), as well as vertical tracking angle. Getting them right significantly improves sound quality. If you missed this feature in the September issue, this is available in electronic form on our website, for £1.90. In Part II this month I am looking at other measurements Adjust+ can make. They don't facilitate adjustment, but can tell you how well your record deck is performing.


FREQUENCY RESPONSE

I was intrigued by this option within Adjust+. Measuring cartridge frequency response is difficult and the problems obscure. Few test discs have ever been accurate enough in themselves to give a meaningful result, so I doubted Adjust+ could manage better. One professional test disc, cut at half speed, is accepted as accurate worldwide: JVC TRS-1007. We have two samples, bought from Japan at high cost long ago, that we use for our cartridge tests. TRS-1007 is now out of production and unavailable.


jvctrs1007frtestd


JVC TRS-1007 test disc offers accurate frequency response measurement.


Amazingly, the Adjust+ disc gave similar results to TRS-1007, although that is not to say "the same". Look at the graphs of Ortofon's 2M Black with JVC and Adjust's discs. The Adjust disc shows raised bass, and treble that looks ragged, but reaches 20kHz within one dB or so. JVC TRS-1007 superficially looks a lot different - although to my eye it looks similar. The reason is that below 1kHz cartridge generators are flat, ignoring arm resonance which occurs very low at 12Hz or so. So the Adjust+ plot is wrong (explanation later) and you can safely draw a straight line in your mind from 40Hz up to 1kHz.


It is at high frequencies that test discs have traditionally been inaccurate, and here the Adjust+ disc gave a result similar, if not the same, as TRS-1007 - impressive. So you can measure the real frequency response of your cartridge to a useful degree of accuracy. But why would you want to? The reason is that many cartridge preamps, including the Trichord Diablo we used within this review, possess switchable capacitance that modifies the high frequency response of Moving Magnet cartridges (but not MCs). Adjust+ will show you how things change as you do this and whether the response gets better or worse. It will also show just how flat, or otherwise, your cartridge is.



2mblackiscfr


Frequency response of Ortofon 2M Black with Adjust+ disc.


As LP playing makes a comeback, the emergence of the Adjust+ test LP is good news, but there are problems. For good reason, test discs never use RIAA correction, but custom equalisation that demands a special preamplifier, which means you can't measure frequency response through an ordinary phono preamp at home. RIAA boosts treble during cutting, and cuts bass, and the treble boost increases both velocity and acceleration of the cutter.


2mblackjvctrs1007fr


Frequency response of Ortofon 2M Black with JVC TRS-1007 disc.



To keep both of these high frequency parameters within acceptable limits for the cutter and playback stylus, signal level on the Adjust+ LP has been kept down, resulting in a poor signal-to-noise ratio at low frequencies. As a result of this, warps start to contribute to the test results, explaining the low frequency lift in the response graph. It may be possible for Adjust+ to lessen this with narrower FFT bins, but there is a trade off against measurement times.


At the other end of the scale, our Goldring 1012GX got decidedly shaky at high frequencies tracking the Adjust+ disc, mistracking above about 4kHz, although it stayed in the groove. So it appears that high velocities are reached all the same and some cartridges will object, likely giving ragged treble under measurement. The Ortofon 2M Black also looks uncertain at high frequencies, our response shows, compared to its behaviour on the JVC disc, likely for this reason. Ultimately, then, the Adjust+ disc gives a good result providing you ignore the low frequency part of the graph.




SPEED ACCURACY / W&F

Speed accuracy is a fairly straightforward measurement, where a 3,150Hz tone is read from a track on the test LP. If it reads 3181Hz then the player is running 1% fast and Adjust clearly displays error in large numerals. Turntables usually have an error of less than 0.5%; anything greater indicates there is a problem.


wfplc5901


Wow and flutter of the Pioneer measured 0.11% according to the Adjust analyser and disc.

Speed error was negligible at 0.005%, because this is a quartz-locked Direct Drive.



Wow and Flutter refer to variations of speed, Wow being slow variations below 10Hz and Flutter fast ones above 10Hz. Interestingly, Flutter is analogous to digital Jitter, both being variations of frequency, or frequency modulation. Adjust+ gave a reading of 0.11% with our Pioneer PLC-590, a little higher than our Rohde & Schwarz UPL audio analyser with DIN weighting selected, playing test LP DIN 45 545 Gleichlauf-Mess-Shallplatte ('synchronisation measuring record', Babelfish says) that recorded 0.07%. So the Adjust+ result is close to professional test equipment. Adjust+ say the result is weighted and the disc has a residual wow and flutter value of 0.03%.


adjustwfofplc590

Wow and flutter of our Pioneer PLC-590 test turntable measured 0.108% according to our Rohde & Schwarz UPL analyser, using the Adjust disc.



To get a meaningful reading, the LP must be centred so the arm isn't swinging in and out and professional test discs usually have an outer locked groove for this purpose. The Adjust+ disc lacks this so it has to be centred visually in an ad-hoc manner. When I placed the disc off-centre deliberately, the 0.11% result rose to 0.2%, illustrating how a large wow component at 0.55Hz due to disc eccentricity will affect the result. Even without a locked groove, the Adjust system has sufficient resolution and accuracy to give a meaningful result, showing just how well a turntable is holding speed and whether maintenance is needed. Again, this is an impressive result, because cutting lathes in themselves can suffer speed variations that will affect any disc that is cut, but the Adjust+ disc avoids this problem.



LOW FREQUENCY  RESONANCE

Pickup arms have a lower subsonic limit (i.e. below 20Hz) imposed by the resonance of arm mass against cartridge compliance. Ideally, it should be around 12Hz. Much lower and the arm will read warps rather than ride over them; much higher and low audio frequencies will receive noticeable boost. Frequency will be low if the arm is heavy (high effective mass) or the cartridge very compliant. Another factor here is cartridge weight, which at 8gms or more approaches the effective mass of a modern arm at 12gms or so.


Adjust+ measures low frequency response using a frequency sweep from 8Hz up to 40Hz. Usually, there will be a resonant peak of 4dB or more and you can see this in our graph showing behaviour of a Goldring 1012GX cartridge in an SME M2-10 arm. Adjust+ neatly identifies the peak and measures both its frequency and amplitude,


goldring1012gx


Low frequency arm resonance. Adjust+ graphs it and identifies frequency and amplitude, in

this case the 7Hz and +8dB result of a Goldring 1012GX cartridge in an SME M2-10


There's not so much you can do about the LF resonance, because, if it is low, using lighter headshell screws or abandoning the finger lift will make little difference. If it is high, when an incompliant Moving Coil cartridge is used in a lightweight arm say, mass can be added to the headshell. However, these days lightweight arms don't exist; most are medium mass. So measuring LF resonance is interesting, but it doesn't facilitate system tuning.


CONCLUSION

All in all then, the Adjust+ test LP is accurate and gives a reliable set of measurements, in conjunction with a computer and soundcard, plus Adjust+ software. The system is superb value at 249 Euros, allowing a cartridge to be aligned with great accuracy, and a wide range of test data to be gleaned about turntable behaviour. It is perhaps a bit complicated, as such an ambitious system inevitably will be, but it works well and is mightily impressive. Nothing like it has ever appeared before, to my knowledge, so it moves the art of LP playing forward by a significant step.




ADJUST+   LP TRACK LIST

 

TRACK CONTENT PURPOSE

SIDE A

1 Sinewave 3150Hz                                        wow and flutter

2 Sinewave 1kHz,                                           lateral/left/right headshell tilt

3 Pink Noise                                                    lateral/left/right frequency response

4 Sinewave 1kHz,                                           lateral/left/right headshell tilt

5 Sine Sweep 3Hz-40Hz                                 lateral arm resonance

6 Sine Sweep 3Hz-40Hz                                 vertical arm resonance

SIDE B

1 Sweep 20Hz-20kHz                                      lateral/left/right frequency response

2 Sweep 20Hz-20kHz                                      lateral slow frequency response

3 Sinewave 3150Hz wow and flutter

4 Sinewave 1kHz,                                           vertical VTA distortion

4 Sine bursts 315Hz                                        left/right/lateral tracking

5 Sine bursts 1kHz                                          left/right/lateral tracking

6 Sine bursts 3.15kHz                                     left/right/lateral tracking

7 Sine bursts 10kHz                                        left/right/lateral tracking

8 Twin tone 3150Hz + 1850Hz                       1:1 intermodulation

9 Twin tone 315Hz + 3150Hz                         4:1 intermodulation

10 Sweep 30Hz-500Hz ..................................arm tube resonance

11 Silent groove ............................................rumble

 

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