Then please send me your .wav file or be so kind to analyse my .wav file, thereby making it possible to comparing results.
One of both must be wrong because having different velocity errors is conflicting with identical PN curves.
I have shown below what I did.
In LT Spice I made 7 bandpass filters that are fed with the recorded .wav file.
They show me at what moment in time the relevant frequency occurs.
Armed with this time info, I look in the Original .Wav file and measure it's corresponding rms value with LT Spice.
Measuring in the original file at the right spot is probably the most direct way that's possible, no transforms, no calculations, no nothing that can corrupt the results.
Hans
Attachments
Sure, it's very "work in progress" maybe you have some suggestions. Let me put a few notes in it to at least explain my reasoning and I'll try some time later today. If it can be made foolproof it might be a useful addition.
While I'm at it does anyone know (george?) if Dick Heyser's complete articles on using the analytic signal for audio are available outside the AES paywall. It's not like what we are doing here is for profit. 🙂
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LD,
Forgive me to rock the boat every now and then, but that can hopefully lead to seeing things from different perspectives and to new insights.
Higher speeds will extend the f range, but it seems not to be that simple to my opinion.
A few postings before in a posting to Bill I referred to a Philips research article, concluding that from a certain frequency and upwards, interaction starts between tip mass and record material.
This makes that while playing an ideal recorded LP, deviations will occur from the expected frequency transfer.
Only a Cart without tip mass and infinite compliance will be able to mechanically follow the track perfectly without such interaction.
To my opinion, that's what could be seen in the measurements I recently made, showing the deviation from the FR at the intended speed versus the altered speed.
In all cases, for PN as well as Sweep and on different records, the deviation curves are showing a signal getting weaker when speeding up from somewhere above 15kHz with a slope of ca 3dB/oct.
When slowing down the exact opposite happens, with the same slope but now in the upwards direction.
Since this is not random but very systematically, and all with roughly the same slope, there must be some physical reason for this, and this could be very well be said interaction between tip mass and record material.
So I'm afraid that when speeding up LP's in general, reference LP's or not, their transfer curve will undergo the same transition.
What's your vision ?
Hans
Attachments
I hope the first link there will satisfy you (I am intrigued for a long time now to start using 3axis diagrams).
John Curl's Blowtorch preamplifier part III
George
Thanks those are unpublished these were, some good stuff here but it's in hand written script. I have one but there were one or two other parts, if I can locate it it will point to the ones I'm missing (IIRC it was from around 1971).
Well, at CV acceleration increases with f. So at some limit, either stylus will lose contact with one of the groove walls (mistracing) or something will flex. Whether what flexes is the cantilever or the vinyl surface is very debatable, but IMO it's prob the cantilever.
At increased rpm, CV increases (level) and so does acceleration and this changes f at which the onset of this phenomenum occurs. But it is simply a function of level, there's nothing exotic about the vinyl surface-stylus interaction.
'Tip mass' is a fairly horrible way of expressing mechanical impedance, based on the half-true premise that above a certain f impedance is mostly due to mass. But its derivation doesn't stand scrutiny - usually based on observation of the top mech resonance (which is notably absent from our recent observations), and assumption of a vinyl spring constant.
I would say that tracking high acceleration has little to do with the stylus-vinyl interface, beyond the friction coefficient. This in turn has little do with rpm, as I have demonstrated to my own satisfaction, is supported by the Pardee paper, and classical physics supports.
So whatever deviation you have found probably has no basis in the stylus-groove interface and is more likely to be a simple artefact of altered level at different rpm.
LD
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LXT 5346 level is 0dB @1Khz = 1.2cm/s rms This is -12.3dB below conventional reference 0dB=5cm/s @1kHz rms. Also there is a -6dB attenuation for f above 10kHz.
So 18kHz recorded level is about 5.2cm/s rms and about 800G peak. It's hot, but this is a test record and obviously the Decca boys considered it trackable on respectable rigs from 1958 (!). Such is the nature of 60 years of backward progress 🙄
As to SXL 2057, that is a stereo test record with one side each dedicated to left and right channel sweeps respectively. Decca prob realised there's no point in test tones above 12kHz because channel separation collapses above that at such levels I suppose.
The two records are best used in tandem.
One has to get into a 1958 mindset to get where this is coming from.
LD
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For the purpose of this thread, 18khz is much too low in frequency.
When deviation starting near 20kHz is to be accredited to an altered level at higher rpm, this hot Decca record thereby even going to boiling hot, will then most likely also deviate from the current 10dB/dec at higher rpm.
I'm with you that a FR doesn't have to be a straight line, but when it's not at higher rpm, this curve has to be validated and documented. Who is beyond suspicion to do that ?
So my question again, do you see any possible way how to validate the Denon record, other than playing it with different high bandwidth carts and comparing results.
That record would make life quit a bit easier so it seems.
Hans
I accept that, and also that playing this record back at 45 rpm needs an exceptional rig to track. No doubt it wasn't the intention to play back at 45rpm, and neither was the purpose to explore cartridge non-ideals in the ultrasound region. Nevertheless, I've not encountered problems tracking at 45rpm and that extends the range to 24kHz just to upset the dog and let the smoke out of the tweeters 😉
1958 was near the start of the commercial stereo era, and Decca was probably the leading recording and playback country in the world at that time, in engineering terms. And that is when the issue of a published reference would have been first tackled, as far as I can tell.
As I say, one needs a 1958 mindset to get it. This predates practical means to perform FFTs, for example...…(!) If one must choose a reference without knowing what is absolute, lining up with Decca SXL doesn't seem too bad a place to be I reckon.
Well no, as discussed, level alters too, and more likely to simply be that.
Well there is: (a) Scott's varispeed playback of a sine monotone, simultaneously measuring 'instantaneous' level and frequency using the detector software we conveniently now have. This seems a very good prospect. (b) If the record is based on monotones it can be validated optically, and AFAIK this was the method professionally used back in the day.
Both are better than statistically combining results from various cartridges and assuming that to be 'absolute', IMO.
On the topic of expressing mechanical impedance in units of 'tip mass', that is like expressing electrical impedance of a coil at self-resonance in Henries. Much as I hate analogies...……..
LD
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We could also get this Ortofon Test Record and send it on tour. If Hans, LD, Scott, JP (and me if I ever get the final bits in place) measure this on a variety of setups we may be able to tease something out the data? I'm willing to get one as part of the discovery on this.
Fantastic record so it seems.
I'm more than willing to buy one, if we can agree on this record.
Hans
Just one thing though. I find the Ortofon quite noisy and it does have quality issues.
OK, but the noise is tough on some of the detection techniques. The manual for the Ortophon LP still makes no sense (to me) for an average user, there is no mention of CV tracks not being flat with an RIAA pre-amp. The also spec +-1.5 dB, as I mentioned a couple of days ago a constant amplitude drive on the cutter should give a CV to within the rotational speed variation. I would think this would be easy to do.
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Looks good to me! Most of my historic testing is with Ortofon carts, including cross references to other test records. A single physical record should remove another layer of variables too. Well done.
LD
Hi,
This was posted in a danish forum. Perhaps Google translate can help or otherwise let me know and I will try.
Maerkelig frekvensgang - HiFi2You
He says that Ortofon told him he should measure without RIAA correction.
Mogens
This was posted in a danish forum. Perhaps Google translate can help or otherwise let me know and I will try.
Maerkelig frekvensgang - HiFi2You
He says that Ortofon told him he should measure without RIAA correction.
Mogens
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