Agreed there is only so much we can correct, but nevertheless its fun to play with ideas that have been forgotten over the years and see what new light we can shine on them.
GZ actually model the groove on the computer before cutting even starts!
New mastering system GZ Vinyl
GZ actually model the groove on the computer before cutting even starts!
New mastering system GZ Vinyl
Last edited:
Derumbler Front End for Testing
The circuit has 3 buffers to isolate the signals. The circuit uses 2 non-inverting summing circuits.
The first (top) circuit mixes the rumble signal with the LEFT channel.
The second can either mix an inverted rumble with the RIGHT channel or by moving point A to Point B, have the left and right channel rumbles be in phase.
Hi Kissabout, For testing, the Derumbler need a front-end that puts in a "rumble" signal.
The circuit has 3 buffers to isolate the signals. The circuit uses 2 non-inverting summing circuits.
The first (top) circuit mixes the rumble signal with the LEFT channel.
The second can either mix an inverted rumble with the RIGHT channel or by moving point A to Point B, have the left and right channel rumbles be in phase.
Why Bother with a Vertical Derumbler?
Hi Bill,
Thank you for your thoughtful comments.
Record warps are easy to see while the record is playing and produce quite large very low frequency anti-phase signals. The usual way we notice this is with vented box (bass reflex) subwoofers where the cone moves a lot (and its not music!) This is infrasonic. However, if the cone excursion gets near Xmax, harmonics are introduced that could affect the audible bass. In really severe cases you can hear an asthmatic chuffing sound. The simplest remedy is to switch in the the rumble filter such as the 8th order Butterworth tuned just below the bottom octave (18 Hz, for example). That is brute force but it works!
The other solution is to switch to mono. This works at elimination vertical effects but, of course, we don't have stereo. Stereo was a brilliant marketing ploy because what we had became obsolete and we now needed twice as much to enjoy the "phantom middle channel", etc, etc. OK, enough of that righteous rant.
The idea of the Devinyliser (and all the other circuits that mono-ise the lower frequencies) is to preserve the benefits of stereo (such as hearing instruments that play at higher frequencies and voices spread across the sound stage). This recognizes the fact that lower frequencies are much more difficult to localize so you might as well convert them to mono and get rid of some forms of interference.
Crossfeeding in its various guises is quite difficult to implement. Doug Self's "Electronics for Vinyl" has an excellent discussion of the topic AND a circuit suggestion that works quite well (and is recommended by at least one participant in this thread).
About 30 years ago, I experimented with a 2nd order Butterworth that didn't work at all how I expected. In my Active Filter classes in grad school, we discussed sync-tuned filters (easy to design, rather lousy roll-off) and that was about it - I wanted brick wall filters or nothing! That's because I hadn't appreciated a very important property of Linkwitz-Riley filters - namely that you could use them in speaker active crossovers without notches or bumps at the crossover points (there was even a design that put in another speaker to fill in the gap). RANE corp has a a very clear discussion on LR crossovers.
When I read Doug Self's book (I was mostly interested in phono preamps) I read about the Devinyliser and thought I might resurrect my old circuit but with 4th order LR filters (being stuck at home also encourages trying to finish half-completed projects). It was one of those projects that you half expect to remind you about why it was a bad idea in the first place. I was very gratified that the LR filters seemed to work.
To go back to your question, I'm planning to built the derumbler into my new preamp along with the rumble filter and a 22KHz ultrasonic filter. I've already incorporated the infra- and ultra-sonic filters into my "Stan Curtis" phono preamp. I can tell when the rumble filter is in-circuit on some records but I can't hear any difference with the ultrasonic filter (it does however, improve unweighted noise measurements!). As a very low priority, I may repurpose the ultrasonic to lowpass at, say, 6KHz, 8KHz, and 10KHz.
Really, the question is what has been solved and what new problems have been introduced?
Hi Bill,
Thank you for your thoughtful comments.
Record warps are easy to see while the record is playing and produce quite large very low frequency anti-phase signals. The usual way we notice this is with vented box (bass reflex) subwoofers where the cone moves a lot (and its not music!) This is infrasonic. However, if the cone excursion gets near Xmax, harmonics are introduced that could affect the audible bass. In really severe cases you can hear an asthmatic chuffing sound. The simplest remedy is to switch in the the rumble filter such as the 8th order Butterworth tuned just below the bottom octave (18 Hz, for example). That is brute force but it works!
The other solution is to switch to mono. This works at elimination vertical effects but, of course, we don't have stereo. Stereo was a brilliant marketing ploy because what we had became obsolete and we now needed twice as much to enjoy the "phantom middle channel", etc, etc. OK, enough of that righteous rant.
The idea of the Devinyliser (and all the other circuits that mono-ise the lower frequencies) is to preserve the benefits of stereo (such as hearing instruments that play at higher frequencies and voices spread across the sound stage). This recognizes the fact that lower frequencies are much more difficult to localize so you might as well convert them to mono and get rid of some forms of interference.
Crossfeeding in its various guises is quite difficult to implement. Doug Self's "Electronics for Vinyl" has an excellent discussion of the topic AND a circuit suggestion that works quite well (and is recommended by at least one participant in this thread).
About 30 years ago, I experimented with a 2nd order Butterworth that didn't work at all how I expected. In my Active Filter classes in grad school, we discussed sync-tuned filters (easy to design, rather lousy roll-off) and that was about it - I wanted brick wall filters or nothing! That's because I hadn't appreciated a very important property of Linkwitz-Riley filters - namely that you could use them in speaker active crossovers without notches or bumps at the crossover points (there was even a design that put in another speaker to fill in the gap). RANE corp has a a very clear discussion on LR crossovers.
When I read Doug Self's book (I was mostly interested in phono preamps) I read about the Devinyliser and thought I might resurrect my old circuit but with 4th order LR filters (being stuck at home also encourages trying to finish half-completed projects). It was one of those projects that you half expect to remind you about why it was a bad idea in the first place. I was very gratified that the LR filters seemed to work.
To go back to your question, I'm planning to built the derumbler into my new preamp along with the rumble filter and a 22KHz ultrasonic filter. I've already incorporated the infra- and ultra-sonic filters into my "Stan Curtis" phono preamp. I can tell when the rumble filter is in-circuit on some records but I can't hear any difference with the ultrasonic filter (it does however, improve unweighted noise measurements!). As a very low priority, I may repurpose the ultrasonic to lowpass at, say, 6KHz, 8KHz, and 10KHz.
Really, the question is what has been solved and what new problems have been introduced?
Rumble Standards
Vinylengine had a rumble thread back in 2010 called "stupid question..rumble".
A clearly very knowledgeable participant from Japan called Shoji, mention 3 international standards for how to measure rumble:
1) IEC 98 (1984)
2) DIN 45539A for unweighted measurements
3) DIN 45539B for weighted measurements
Have a look at the attached file.
The DIN B curve and the IEC 98 weighted curves are quite similar with the peak in the vicinity of 300Hz. This curve takes into account the variation of hearing with frequency and loudness.
What is odd is the unweighted curves which only start at 10Hz but go up to the weighted curve.
On the AES website there are some old papers (from the 1960's) that show that a lot of the noise produced by a turntable goes up to several hundred Hz. The main reason we aren't driven crazy by it is that the surface noise and the music are much louder!
I'm thinking that we might need to discuss what WE mean by rumble to that we can come up with an appropriate cure!
Perhaps Douglas Self could join these deliberations with his experiences when he designed the Devinyliser?
Vinylengine had a rumble thread back in 2010 called "stupid question..rumble".
A clearly very knowledgeable participant from Japan called Shoji, mention 3 international standards for how to measure rumble:
1) IEC 98 (1984)
2) DIN 45539A for unweighted measurements
3) DIN 45539B for weighted measurements
Have a look at the attached file.
The DIN B curve and the IEC 98 weighted curves are quite similar with the peak in the vicinity of 300Hz. This curve takes into account the variation of hearing with frequency and loudness.
What is odd is the unweighted curves which only start at 10Hz but go up to the weighted curve.
On the AES website there are some old papers (from the 1960's) that show that a lot of the noise produced by a turntable goes up to several hundred Hz. The main reason we aren't driven crazy by it is that the surface noise and the music are much louder!
I'm thinking that we might need to discuss what WE mean by rumble to that we can come up with an appropriate cure!
Perhaps Douglas Self could join these deliberations with his experiences when he designed the Devinyliser?
A key question and one I will need a couple of attempts to answer. To me rumble as in terms of the normal expectation of bearing noise was a solved problem 50 years ago when Idlers started to go out fashion. Bearings in good condition are effectively silent these days. So what we are left with are unwanted signals with sources
1. the turntable (motor noise, vibration etc)
2. resonances in the arm/cart system
3. Issues with the record itself.
Some of these are audible by themselves and some of them cause an audible effect by FM the wanted signal. It's arguable that anything below 30Hz is in the FM category so needs to be fixed at source rather than filtered out later.
From 50Hz to 300Hz we are in the zone where blend to mono solutions would help. Is it rumble or it is another issue that needs discussing seperately.
More to follow...
All the picking around about rumble and low sub frequency and what angle it comes from is unnecessary fiddling around.
It's just too much overthinking of a simple problem.
Simply put, rumble, and/or low frequency feedback issues are easily corrected with things like the 38dB Sallen-Key filters that I previously mentioned.
Because no matter what "angle" that LF "noise" comes from, it's reduced/eliminated, period.
Then, the enjoyment is increased dramatically, and life can go on.
It's just too much overthinking of a simple problem.
Simply put, rumble, and/or low frequency feedback issues are easily corrected with things like the 38dB Sallen-Key filters that I previously mentioned.
Because no matter what "angle" that LF "noise" comes from, it's reduced/eliminated, period.
Then, the enjoyment is increased dramatically, and life can go on.
If you disapprove of anything that is slightly more original than a plain old high-pass, why did you join this thread in the first place?
Please have a look at the website below that has some good info on rumble, and wow+flutter. There is mention of acoustic&mechanical feedback, and tonearm&cartridge resonance.
Measures
Last night I was listening on headphones to "Gloria" by Them (fronted by Van Morrison). This has a LOT of stereo bass on it that would clearly be lost by any mono-izing circuit. Another case that comes to mind is Captain Beefheart's album Safe as Milk. Although the impact of the Devinyliser or derumbler might not be too noticeable playing through speakers, I think headphone listeners used to extreme separation might object.
Measures
Last night I was listening on headphones to "Gloria" by Them (fronted by Van Morrison). This has a LOT of stereo bass on it that would clearly be lost by any mono-izing circuit. Another case that comes to mind is Captain Beefheart's album Safe as Milk. Although the impact of the Devinyliser or derumbler might not be too noticeable playing through speakers, I think headphone listeners used to extreme separation might object.
Some of that is great engineering, but we are in the 21st century now and have amazing processing power at our fingertips.
Turntable speed stabilty worked on looking at new ways to measure what is going on. Example attached to show the scale of the problem. You record 8-10 seconds of a fixed frequency on a test record and feed it into a short python script Scott Wurcer wrote and bingo.
So what does it show? Well the biggest perturbation is the 0.55Hz from the record not being properly centered and you can see a couple of peaks from the arm cart resonances. Might be a bit of bearing wear as well. Certainly needs a tune up! But all of that will modulate the wanted signal, audibly or not and no amount of filtering the LF will get rid of the modulation. You have to address as much as you can in the mechanical domain.
Attachments
No such thing as extreme separation with Vinyl!
The cutting heads were just not that good, and if it comes to that there was generally a fairly crude elliptical equaliser in the cutting chain (So called on account of how it made the goinometer display look).
IIRC the SAL74B (Probably the most popular cutting chain in the world) was good for maybe -35dB @1kHz if you were playing a lacquer.
Not a lot of point in expecting more on the playback then the lathe can scratch.
Hi Dan, From your comments it sounds as if you might be a lathe troll? I've only ever seen pictures, and maybe the odd Youtube, of the cutting process.
OK, I agree that "extreme separation" is quite an exaggeration when applied to vinyl!
I have lots of time with this covid-19 forced to stay home, so I try with components that I have and I build the Rod Elliot Project 99 subsonic filter, this was show by Wiseoldtech on post #95.
The only caps available are 100nF and TL072, finished two days ago first tested with generator and scope and the response was exactly how expected, last night connected between my all tube RIAA preamp and RCA 30+30 tube amp., result? Fantastic !!!!!
Finally I do not have anymore my Foster Fe-206en pumping like crazy for don’t talking about the wasting of power. I pushed to the limit my amp in volume and bass freq. and I could not see any pumping at all just pure music.
I can finally listen my vinyls to the full and no anymore be careful about bass frequencies, for partly avoid the pumping I used an EQ with low cut set to 60Hz and all bass freq. attenuated, in this way the pumping was no so noticeable but still there and the listening experience was of course not the best, now all fixed, thanks guy for sharing all this informations…..all the best
The only caps available are 100nF and TL072, finished two days ago first tested with generator and scope and the response was exactly how expected, last night connected between my all tube RIAA preamp and RCA 30+30 tube amp., result? Fantastic !!!!!
Finally I do not have anymore my Foster Fe-206en pumping like crazy for don’t talking about the wasting of power. I pushed to the limit my amp in volume and bass freq. and I could not see any pumping at all just pure music.
I can finally listen my vinyls to the full and no anymore be careful about bass frequencies, for partly avoid the pumping I used an EQ with low cut set to 60Hz and all bass freq. attenuated, in this way the pumping was no so noticeable but still there and the listening experience was of course not the best, now all fixed, thanks guy for sharing all this informations…..all the best
And going by that diagram that you posted, actually anything below 18 hertz is just "noise", and must be removed/damped/eliminated.
For all reasonable intents, particularly with records, anything below 20-25 Hz is noise, robbing power from the amplifier, pumping speakers, etc.
There certainly isn't anything "that low" to listen to, nor would anyone with a sane reasonable mind notice the lack of those sub frequencies.
The several P99 subsonic filters that I've added to some of my equipment certainly improve the resulting performance, and I've got them configured to a -3dB @ 27Hz. (using 0.1uF caps)
The "real" bass (>30Hz) that I now hear is cleaner and more defined, without power losses from "sub" robbing.
And my turntables now sit still, instead of shaking from feedback at high volume levels.
It's lovely.
I'm glad that you found a proper solution, but I'm also not surprised, because that circuit really works.
And excellently of course.
Hi Bill, My only experience of the speed stability came from Michael Fremer's columns is Stereophile. I never realized how much richer the subject was.
That polar plot display is amazing! I especially like Luckythedog's plot with 2 revolutions.
Got me bang to rights!
A lot of the vinyl fetish thing is just weird when you understand the limits inherent in actually cutting the scratch.
I mean, yea a good record sounds nice and they are generally big enough for decent cover art, but any claims for accuracy.... Ah, not so much!
As for that whole extended frequency response thing, somebody needs to actually look at the schematics for the cutting chain before coming out with that tosh, or at least grab the AES disk recording anthologies!
BTW, there is NO SUCH THING as the Neumann pole, it never existed as such in any cutting chain.
What there is is a two pole Sallen and Key LPF at the input to the program equaliser card, slightly peaky by my spice and going over at about 50kHz, an extra zero in the 75us eq section, and the opamp running out of gain bandwidth at ~100khz. Note however that there is a two band tone control in the program EQ (AFTER the IRIAA stage) used to adjust for spring back at low frequencies and less then ideal cutter head behaviour at HF).
Then before all of that is the BSB74 card that provides high frequency limiting to avoid issues with the geometry limited acceleration of the replay stylus (Also, high frequency velocity limiting so the back edge of the cutting stylus does not chew up the cut made by the front edge), basically a de-esser.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.