I think I'll stick with my own software. At least I will get the right sort of filter.
That article says that less than 20 msec of group delay is inaudible. I don't think phase is an issue.
Hi, does that resonance with Q~10 not saturate the pick-up, so thou get clang and intermodulation in some situations? An electrical notch filter cannot repair a signal, which has become spoiled already before. So i thot, that pick-up resonance frequency should be higher, say 25 Hz, and of much lower Q, say 0.6, the straight Bessel, in order to cut out rumble mechanically.
Hi
I didn't notice any intermodulation and I don't have concerns with woofer because I am listening with headphones.
For me and my system the best would be to reduce the mecanical resonance of the tonearm-cart instead of employing a sophisticated filter that will add a lot of components on the path of the signal.
Ideally to try to kill the cause and not try to repair the signal after.
I have some ideas to damp the tonearm-cart. I have to take time to implement and try.
Jacques
For an Fres of 25 Hz, you would need a superlight element, having an extremely low compliance and a very light arm with a low effective mass, like resp. 4gram, 5um/mN and 4 gram.
I do not think you will be able to find that combination.
About lowering the Q with whatever sort of damping, there are several schools.
Some say a Pick Arm should not be damped, while others are in favor.
Anyhow, a very high Q can and should be avoided with the proper choice of element/arm combination, to restrict rumble (and IM distortion) mechanically like you mentioned.
Hans
See Allmaier's excellent article, which shows that the subsonic signals themselves may the least of your worries. Other problems coming from cart/arm wobbles:
1 Intermodulation distortion due cartridge non-linearity
2 Wow and flutter introduced by the stylus scrubbing back and forth in the groove.
Obviously no filter can help with either. Modifying the cart/arm resonance, with damping or otherwise, seems to be all you can do.
Just two reasons why I have a poor opinion of vinyl. It does, however, provide some interesting problems in electronic design...
H Allmaier “The Ins and Outs of Turntable Dynamics” Linear Audio Vol 10, (Sept 2015) pp 9-24. Really good, a must-read for those with turntables.
I have the feeling that the discussions are converging.
Diminishing rumble mechanically, by choosing the right arm/element combination with a low Q and the right Fres, instead of just fighting the rumble with a rumble filter, should be the first and most important step when selecting a record player.
All the extra harm done to the signal (Wow and IM) by having the wrong arm/element combination, can never be cured by a filter.
Doesn't that automatically lead to the conclusion that the "ideal rumble filter" is the filter that keeps the woofers in control by preventing large uncontroled movements?
And since all woofers are different, my feeling is that the "ideal rumble filter" should have different settings for individual needs, like a bass control in a tone control having a selectable corner frequency and slope.
Since filtering means killing information, this type of setting could be adjusted just to the point where it exactly meets the needs and no further.
Hans
Diminishing rumble mechanically, by choosing the right arm/element combination with a low Q and the right Fres, instead of just fighting the rumble with a rumble filter, should be the first and most important step when selecting a record player.
All the extra harm done to the signal (Wow and IM) by having the wrong arm/element combination, can never be cured by a filter.
Doesn't that automatically lead to the conclusion that the "ideal rumble filter" is the filter that keeps the woofers in control by preventing large uncontroled movements?
And since all woofers are different, my feeling is that the "ideal rumble filter" should have different settings for individual needs, like a bass control in a tone control having a selectable corner frequency and slope.
Since filtering means killing information, this type of setting could be adjusted just to the point where it exactly meets the needs and no further.
Hans
I share your point of view.
And I would add that rumble from the motor of the turntable is nearly always above 20 Hz and the only way to fight is mecanical actions.
Jacques
I came across these nice little damping devices from the seventies.
https://www.youtube.com/watch?v=8Lgz_feHvJM
http://www.theanalogdept.com/images/spp6_pics/SME/FD200SME/SME%20FD%20200.pdf
Hans
https://www.youtube.com/watch?v=8Lgz_feHvJM
http://www.theanalogdept.com/images/spp6_pics/SME/FD200SME/SME%20FD%20200.pdf
Hans
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These stabilse the cartridge relative to the platter and do nothing for warps, in fact they can cause the cartridge to bottom on bad warps. The Townshend trough at the end of the arm was the most extreme example
But is that possible? So far as I can see the scope for this, presumably by choosing cart and arm, is very limited.
As indeed I just said. I suppose it might be possible to undo the wow & flutter in the digital domain if you could correlate it with the subsonic signals, but it won't be easy and will have to be re-tuned for every cart/arm combination.
Probably do-able, but it won't be easy. I don't think we need to get that complicated. See next answer.
But does it? We have been talking about filters that are -3dB at 20 Hz; is there really any musical information below that? If 20Hz is too close-in to the passband, woud 15 Hz be acceptable? This is the sort of thing I'm trying to determine.
That's a most interesting pdf- many thanks. I recall these things were rather messy; the silicone oil used to get everywhere.
I think this is a most important point. Damping with respect to the platter could easily makes things worse.
Did not Shure have a little brush which damped the cart/arm with respect to the record surface?
In a second order system, a cartridge can only "bottom" on a warped disc when having an overshoot in it's response , meaning that Q is (much) larger than 1, and that its Fres is too close to the warping frequency.
See the previous You Tube video where a hugely warped record is used as a demonstration, nicely following the groove.
Compare it to the wheel of a car, if underdamped because the shock absorber is worn, it starts to lose control with the road because the wheel is "oscillating" at Fres.
This is exactly what a stylus does in a groove.
And like the wheel of a car, overdamping should be avoided, but even more important, Fres should be kept well above the warping frequencies.
Fres = 11Hz seems to be some optimum.
The effect of the damping brush on the Shure V15 is described here
Shure V15-IV phono cartridge | Stereophile.com
Hans
I think was this thread shows is a lack of understanding of things which were already an advanced science in the 1950's. I have the AES books Volume 1 and 2 for this including Percy Wilsons Record Doctor I make as Loricraft PRC6. We truely do stand on the shoulders of gaints when Percy and edgar Gernam Who suspect was the inventor. He won a Gramophone prise in 1928 for alignement using 63.5 and 119 mm. Percy was a mathamatician. I never met him, but am a friend of his friend John Borwick who is still alive in his 90's. John and Percy worked for Comptom Macenzie of Whiskey Garlour fame.
Here we seem to be correcting as if the hubble space telescope. This is not required unless for the unfortunate few recordings.
There are true professionals in this industry. I know many. Mr Stalllinger of Ortofon was one. Work in Germany 1939 to 1944 as Ortofon's man. He was still acive in 2000. They pull their out at what is written. A few opamps isn't worth much converstion although a gift to a person who needs this.
Here we seem to be correcting as if the hubble space telescope. This is not required unless for the unfortunate few recordings.
There are true professionals in this industry. I know many. Mr Stalllinger of Ortofon was one. Work in Germany 1939 to 1944 as Ortofon's man. He was still acive in 2000. They pull their out at what is written. A few opamps isn't worth much converstion although a gift to a person who needs this.
Yes, but like weight-loss advertisements in magazines, they may not tell the truth!
Anyone can draw a line perfectly following over a bump and say "us!" and a wiggly line going everywhere and say "them!". Nice advertising. Of the engineering, I am skeptical.
Thanks.
And to think all these years I thought the brush was there to sweep up dust off the record!
And to think all these years I thought the brush was there to sweep up dust off the record!
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