I've been playing around with my turntable and preamp lately and tried to somehow match reality with simulation. Well, what shall I say, it totally didn't work 😀! Seems like it is anything but trivial to model a MM cartridge in LTspice - a simple one-coil-one-resistor model is certainly not the way to do it.
Anyhow, apart from judging the results solely by ear, I also tried to figure out a way to measure the actual frequency response. Of course this is not possible without a test disk with known content, but then again... What if I recorded a single track with my soundcard and then compared it to the 'known' digital copy of that same track?
Since I just started into the vinyl hobby, my collection is not that big really, but I happen to have three fairly recent recordings at hand (of three different genres), for which I could easily acquire the corresponding digital downloads.
Of course there's still a certain uncertainty concerning the mastering of those different media. The vinyl version might have been mixed differently than the CD version, and the digital download might have been run through the compressor a final time for today's iPod generation. There's probably no way to be certain here. Then the ultimate way to go would be to have your vinyls recorded to the PC on a known good record player as a reference, but I for one don't have one around here... 🙄
So I recorded my test tracks, downloaded the according digital versions, ran them through Cool Edit for some nice FFT plots and then matched them up in PhotoPaint to account for the differences in level.
The red graphs are for the digital version and the cyan graphs are the vinyl recordings.
Here are the results of my testings:
The first track is probably best categorized as Electronic Music, since it's mostly noise out of a computer I'd say. I don't even like that track, but I got a brand new vinyl for free, so it's the perfect test disk 😉.
As you can see the graphs match up pretty well up to around 3kHz, then the vinyl drops down some 7dB, just to match up exactly again at 20kHz. That dip is certainly audible 🙁. I'm not sure what causes this, since the record sounds clearly worse than the digital version. Might this be due to that record being made for club use rather than for domestic HiFi? I dunno...
The second track is Hip-Hop - certainly not my genre, but this one track is awesome (as is the green vinyl 😎). Here the recording starts do drop out a little earlier, but only for a mere 3dB, and matches up again around 14kHz. In a direct comparison the difference is noticeable, but certainly not that bothersome like the first record. I like the vinyl version better in this case, actually.
And finally the last track from one of my favourite albums, Rock'n'Roll at its finest 😛. Et voila, not much to say here - the graphs match up perfectly well! This is confirmed through a direct A-B test with normalized levels. Of course the recording has some pops and clicks to it, so they're not indiscernible, but neither version sounds bright or harsh or dull compared to the other.
Any conclusions to draw from this?
In a way I'd say this procedure has its merits. On the other hand I'm puzzled as to why different records produce such different results here. What I noticed was that the first two recordings have a somewhat higher overall level than the third. In my mind this is due to the first two having only one track on each side, while the third disk is actually crowded with seven tracks on Side A. But then again I don't know whether a cartridge can produce different frequency responses for different groove velocities (or whatever may be the difference here).
Not sure if it is of any interest, but the used cartridge is supposedly an AudioTechnica AT91 with a brand new replacement stylus. Only the left channel was used throughout. Preamp is based on the Elektor Supra, which I wrote about in another thread. Cartridge loading was 22k together with a measured cable capacitance of ~130pF (excluding tone arm wiring). The rest of the turntable is a rebranded DUAL design, tracking force was set to 1.5 with anti-skating set accordingly. The player runs a little bit faster than 33 1/3 which can be seen by closely looking at the peaks in the graphs above.
Anyhow, apart from judging the results solely by ear, I also tried to figure out a way to measure the actual frequency response. Of course this is not possible without a test disk with known content, but then again... What if I recorded a single track with my soundcard and then compared it to the 'known' digital copy of that same track?
Since I just started into the vinyl hobby, my collection is not that big really, but I happen to have three fairly recent recordings at hand (of three different genres), for which I could easily acquire the corresponding digital downloads.
Of course there's still a certain uncertainty concerning the mastering of those different media. The vinyl version might have been mixed differently than the CD version, and the digital download might have been run through the compressor a final time for today's iPod generation. There's probably no way to be certain here. Then the ultimate way to go would be to have your vinyls recorded to the PC on a known good record player as a reference, but I for one don't have one around here... 🙄
So I recorded my test tracks, downloaded the according digital versions, ran them through Cool Edit for some nice FFT plots and then matched them up in PhotoPaint to account for the differences in level.
The red graphs are for the digital version and the cyan graphs are the vinyl recordings.
Here are the results of my testings:
The first track is probably best categorized as Electronic Music, since it's mostly noise out of a computer I'd say. I don't even like that track, but I got a brand new vinyl for free, so it's the perfect test disk 😉.
As you can see the graphs match up pretty well up to around 3kHz, then the vinyl drops down some 7dB, just to match up exactly again at 20kHz. That dip is certainly audible 🙁. I'm not sure what causes this, since the record sounds clearly worse than the digital version. Might this be due to that record being made for club use rather than for domestic HiFi? I dunno...
The second track is Hip-Hop - certainly not my genre, but this one track is awesome (as is the green vinyl 😎). Here the recording starts do drop out a little earlier, but only for a mere 3dB, and matches up again around 14kHz. In a direct comparison the difference is noticeable, but certainly not that bothersome like the first record. I like the vinyl version better in this case, actually.
And finally the last track from one of my favourite albums, Rock'n'Roll at its finest 😛. Et voila, not much to say here - the graphs match up perfectly well! This is confirmed through a direct A-B test with normalized levels. Of course the recording has some pops and clicks to it, so they're not indiscernible, but neither version sounds bright or harsh or dull compared to the other.
Any conclusions to draw from this?
In a way I'd say this procedure has its merits. On the other hand I'm puzzled as to why different records produce such different results here. What I noticed was that the first two recordings have a somewhat higher overall level than the third. In my mind this is due to the first two having only one track on each side, while the third disk is actually crowded with seven tracks on Side A. But then again I don't know whether a cartridge can produce different frequency responses for different groove velocities (or whatever may be the difference here).
Not sure if it is of any interest, but the used cartridge is supposedly an AudioTechnica AT91 with a brand new replacement stylus. Only the left channel was used throughout. Preamp is based on the Elektor Supra, which I wrote about in another thread. Cartridge loading was 22k together with a measured cable capacitance of ~130pF (excluding tone arm wiring). The rest of the turntable is a rebranded DUAL design, tracking force was set to 1.5 with anti-skating set accordingly. The player runs a little bit faster than 33 1/3 which can be seen by closely looking at the peaks in the graphs above.
Attachments
- Status
- Not open for further replies.