In this blog post I compare three vintage turntables against a modern turntable in terms of objective test data including harmonic and intermodulation distortion and frequency response. By utilizing a test LP developed by the National Research Council here in Canada, I am able to capture the output from the phono stage directly into the ARTA measurement software.
Physical Test Setup Description
Turntable with test record > Phono Preamp > ADC input Box > Laptop using ARTA measurement software
Test Hardware
Phono Preamp: NAD C160 Preamp
ADC Input Box: E1DA Cosmos
Aurex/Toshiba SR-D350 Direct Drive Turntable (Vintage)
Manufacture Date: ?
Cartridge: Micro-Acoustics MA 2002-e phono cartridge
Specifications
Drive system: direct drive
Motor type: coreless and slotless
Speeds: 33 and 45rpm
Pitch control: +/- 2%
Platter: 310mm aluminium diecast
Tonearm: static balance, straight pipe
Effective length: 215mm
Overhang: 16mm
Cartridge weight range: 4 to 9g
Wow and flutter: 0.025% wrms
Rumble: 73dB
Dimensions: 420 x 125 x 382mm
Weight: 5.2kg
Test Results
Dual Tone Test (1kHz & 1.5kHz)
The test record includes a dual tone test signal which allows for observation of the intermodulation distortion products. These side tones are more offensive to the ear due to their non-harmonic nature. The real time spectrum analyzer displays the result during playback of the LP's test tones.
I've labelled the two test tone signals as well as the side band distortion products which are a mix of Intermodulation and harmonic distortions.
The dynamic range is indicated by difference between the test tones and dominant noise products, which in this case is IMD1 at -30dB, certainly within the audible range.
With a single test tone at 1kHz we are only able to observe harmonic distortion. H2 is -50dB down with H3 and H4 almost into the noise floor. So we see that intermodulation distortion seems to flesh out much higher distortion values than the easier single test tone.
With both graphs (IMD and Harmonic) we can see low frequency noise is at around -45dB, which are not affected by the the test tones themselves.
Lastly I looked at the frequency response using the pink noise track on the test album. I'm not sure why, but the response trends downwards starting at around 200Hz. This could be in the test album iteself, or some other reason. Regardless, it does offer some insight as we compare the results with other turntables.
Rega RP2 with ND3 Cartridge (Modern Turntable)
This turntable is brand new and fully calibrated from the dealer.
Product Links:
We see the Rega perform better than the Aurex with IMD2 at -35dB. The low frequency noise is -50dB down. In both areas of the frequency spectrum we see a 5dB improvement in dynamic range compared to the Aurex.
The single tone test shows H2 at the -45dB. The noise is very low for the high frequency region at -65dB. H3 must be very low since it is buried in the already very low noise floor. We see 60Hz AC mains hum at -28dB below the fundamental.
The frequency response appears linear until 7kHz where we see a gradual rise in the response of about +5dB by 15kHz. This of course ignoring the inexplicable falling response of the result (see above comments).
Thorens TD-145 (Vintage) with Denon DL103 Cartridge (A modern classic!)
We see this Thorens exceeds the Rega by achieving -38dB for IMD2. Low frequency noise is also good at -43dB.
H2 is -48dB which is comparable to the other turntables.
Frequency response is quite linear with excellent high frequency extension.
Luxman PD264 (Vintage) with Audio Technica VM540ML (Modern)
The Luxman exceeds both the Rega and Thorens with IMD2 at -40dB. Low frequency noise is also the best at -48dB below the test tones.
Harmonic distortion is similar to the others at -45dB.
We see steep roll-off in the treble starting at 8kHz. It is unknown if this is related to an issue with the cartridge and more inspection may be required.
Conclusion
What we know
- The test setup revealed differences between the turntables
- The modern turntable (Rega RP2) was not the clear winner
- All four turntables performed relatively close to one another in terms of IMD, only varying about 5dB
- The distribution of IMD products vary, especially as you move away from the test tones
- The IMD products are higher than noise generated by AC mains hum
- The frequency response varied considerably
- Harmonic distortion is predominantly second order, potentially leading to a warmer sound character.
- IMD was much higher than harmonic distortion
What we don't know
- The impact IMD has on subjective sound quality
- The overall contribution of the phono stage on both types of distortion
- The overall contribution of the test album on both types of distortion
- Why the frequency response graphs all trend downwards
Final Remarks
These tests form a good baseline for investigation and future testing.
