Low frequency content on LP vinyl records

[gpapag]

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.

Regards
George

 

[Aquarium]

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.

 

[gpapag]

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

 

[gpapag]

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

 

[Aquarium]

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.

 

[EC8010]

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.

 

[Cobra2]

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

 

[Aquarium]

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.

 

[EC8010]

... 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.

 

[sreten]

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.

 

[gpapag]

Hi Sreten

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

I commended on some Figures, so please, be more specific. I may very well have been wrong.

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

You are right if you are considering the recorded data (musical content) only.
But I am thinking of the low frequency output of the cartridge caused not by the recorded data , but by record imperfections, exactly the subject of the article.

Passive EQ ? bass overload is the least of your problems.

Although not the subject of this thread, which do you think are the rest?

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

The 20Hz filter can be incorporated at the front side of the first amplifier block, thus blocking part of the subsonic signal past this stage.
The proper subsonic filter you are quoting, should be an active filter fitted downstream

Regards

George

 

[Aquarium]

I was hoping someone might report on what it sounds like.The final test of all audio theories is to listen and I suggested this before on Audigon and got shot down as well.I guess there are no innocent dupes out there.

 

[gpapag]

I was hoping someone might report on what it sounds like.

Aquarium, to what exactly are you reffering?
To the sound of an overdriven RIAA preamplifier?

Regards
George

 

[Aquarium]

A tonearm cartridge set-up as Ladegaard recommends.Everyone has a theory about why it won't work,but it would be interesting to try, just to put it to rest.

 

[gpapag]

A tonearm cartridge set-up as Ladegaard recommends.Everyone has a theory about why it won't work,but it would be interesting to try, just to put it to rest.

I see.
There was a NAD turntable that had a tonearm which provided for cartrigde/tonearm resonance frequency and Q adjustment. With this tonearm such an experiment is feasible (same turntable, same cartridge, same preamplifier).
If anyone ownes this turntable, please participate.

Regards
George

 

[roddyama]

Shure used to recommend "tuning" the tone arm assembly so the resonance fell in the 12Hz range. After doing whatever you did to "tune" the system, it could be verified using the Shure test record. It's been quite a while since I played with it but the test record had one Hertz steps from 8Hz to 15 Hz (from memory). At resonance the arm would visibly vibrate up and down and right out of the groove sometimes. According to this method, my arm resonance (after some changes) was 12Hz.

 

[gpapag]

Hi all

There was a NAD turntable that had a tonearm which provided for cartrigde/tonearm resonance frequency and Q adjustment. With this tonearm such an experiment is feasible (same turntable, same cartridge, same preamplifier).

This NAD turntable is the model "NAD-5120". It is no longer in production. But complete documentation with a lot of useful information can be found
here

Again, for the link to work, you have first to register to vinylengine site

Regards
George