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Old 17th February 2007, 09:09 PM   #1
gpapag is offline gpapag  Greece
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Default Low frequency content on LP vinyl records

Hi all

I would like to ask you for any information -numerical or spectrum picture- regarding content on low (from 5Hz up to 100 Hz) frequency that a cartridge can pick-up due to record artifacts/imperfections.
I have to check the overload margin of a RIAA preamplifier with a passive equalization that I am revamping.

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George
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Old 17th February 2007, 10:07 PM   #2
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When Poaul Ladegaard did a paper on cartridge resonance in the 70's.He discovered that most distortion begins from around 3-4Hz, due to the inherent "rubbish" in the record groove from normal manufacture.Hope this helps.
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Old 18th February 2007, 12:56 PM   #3
gpapag is offline gpapag  Greece
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Hi Aquarium
Thank you for the info.
I did a search and found an article which I guess is the one to which you are referring to.
This article can be downloaded from here

I went through it and if I interpret the data well, then within the frequency limits for which I am interested, the following may apply:

From Fig.7 it follows that “rubbish” produced from manufacturing process of the record, cause (unfiltered) cartridge output in the 2-5Hz range which can be equal in amplitude to recorded material in the 22-25Hz range, 10dB lower from recorded material in the 50-60Hz range and 16dB lower from recorded material in the 90-110Hz range
Note 1: No cartridge/arm resonance effects are considered.
Note 2: Data refers to maximum modulation velocities. When lower modulation velocities are encountered in recorded material, dB differences will be lower.
Note 3: Fig. 7 Freq. Range is 0.5-100Hz.

From Fig.10 it follows that cartridge (unfiltered) output in the 5-10Hz range due to cartridge/arm resonance effects can be down only 10-20dB from the reference 1KHz recorded signal.
Note 4: Fig. 10 Freq. Range is 2.5-60Hz.

From Fig.12 it follows that cartridge (unfiltered) output in the 10-30Hz range due to rumble can be down only 15-25dB from the reference 1KHz recorded signal.
Note 5: No cartridge/arm resonance effects are considered.
Note 6: Fig. 12 Freq. Range is 1.6-1.25KHz.

From Fig.13 it follows that cartridge (unfiltered) output in the 10-30Hz range due to rumble can be down only 10dB from the reference 1KHz recorded signal when cartridge/arm resonance effects are also considered.
Note 7: Fig. 13 Freq. Range is 1.6-1.25KHz.

Fig.18 shows the Wow & Flutter (unfiltered range 0.5-300Hz ) measurement in the 0.1-500 Hz Freq. Range.
Signal due to Record centering at 0.5-0.6Hz is 23dB
Signal due to Record ellipticity at 1.2-1.4Hz is 11dB
Signal due to cartridge/arm resonance at 3-6Hz is 15dB
Signal due to motordrive/shaft at 20-25Hz is 8dB

Note 8: In all above Figures, records used, were well preserved test records

Fig.19 shows the cartridge (Wow & Flutter weighting responce ) output in the 1.6-1.25KHz using a slightly worn test record and a medium quality turntable (More close to our everyday case!)
1.6-25Hz spectrum is 95-100dB high (Shall I assume that the reference is again 1KHz at 105dB?)!!!

Note 9: I have made reference only to low frequency data.
Note 10: The verdict of the paper is that cartridge/arm resonance aggravated by sub-audible low freq. stimulus, is the main source of trouble not only in the low freq. range , but in the mid freq. band as well.

My reaction to this paper is that I have to increase the low freq. overload margin of my RIAA preamplifier, although it incorporates the (relatively speaking) recently recommended 20Hz HP filter.

Regards
George
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Old 18th February 2007, 03:04 PM   #4
gpapag is offline gpapag  Greece
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Hi all
I just noticed that the link I provided in the post above, should link to the article "Audible effects of mechanical resonances in turntables" by Poul Ladegaard.
But it doesn't.
It works only after logging in to the www.vinylengine.com

So, first log in, then click on the link.

Regards
George
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Old 18th February 2007, 08:37 PM   #5
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I find it interesting that nobody ever seems to have followed up the recommendation for raising tonearm resonance to 15-18Hz.Although some would argue this is too high because subsonic information exists here i.e organ down to about 16Hz.Today everyone is quite happy with 11-12Hz.
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Old 19th February 2007, 12:40 PM   #6
EC8010 is offline EC8010  United Kingdom
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Quote:
Originally posted by Aquarium
I find it interesting that nobody ever seems to have followed up the recommendation for raising tonearm resonance to 15-18Hz.
That's because if you choose a cartridge with sufficiently low compliance, then put it in a light enough arm to achieve fs = 15-18Hz, the cartridge excites the structural resonances unacceptably.
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Old 19th February 2007, 01:00 PM   #7
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Why not lower? I have no trouble with fs = 7-8Hz ...
But then I have a solid TT on a heavy stand, and fairly flat records.

Arne K
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Old 19th February 2007, 01:03 PM   #8
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Not if the cartridge had a mass of say the Denon 103 and a true compliance laterally of about 10cus(about) on arm like a Rega at 11gms effective mass.This would get close already.Actually there are cartridges like the Ikeda OC 9 and the Decca Gold which have no cantilever,being true moving-iron type.It would be quite possible to achieve 15-18Hz resonance.
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Old 19th February 2007, 01:36 PM   #9
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Quote:
Originally posted by Aquarium
... Decca Gold which have no cantilever, being true moving-iron type. It would be quite possible to achieve 15-18Hz resonance.
I just knew someone would mention the Decca Gold...

I used to be a Decca fan (had two Golds). Their low compliance means they put so much vibration back into the arm that anything and everything sings. In 1978 I made an unusually rigid (for that time) arm specifically for the Decca Gold. Even then, the 1/2" tube benefitted from a little external damping.
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Old 19th February 2007, 07:31 PM   #10
sreten is offline sreten  United Kingdom
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Hi,

The information in the article is interesting, the conclusions are not.

Phono preamps overloading in the Bass ? I don't think so, not practically.

Passive EQ ? bass overload is the least of your problems.
By definition overload margins will be much lower at higher frequencies.

Standard 20Hz filter ? Ignore / remove it and add a proper subsonic filter.

/sreten.
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