I'm temporarily going back to my Thorens TD160 turntable, in order to capture all my LPs in high resolution, cleaning the records from surface noise, clicks and pops at the same time. I have already done that with a friend's Luxman high resolution system, with V15 cartridge, and the results were fantastic.
The I proceeded, using Audacity, to clean the LP from all surface noise and eliminated all the clicks and pops I could find. Capturing at higher resolution, like 96KHz, would allow higher accuracy in the noise elimination. In any case, the files sound excellent. We still have to make a comparison between the original LP and the CD with the processed files and see how they sound.
Now I'm the process of building the RIAA preamp. This has been commented elsewhere, which generated a very constructive discussion, where I learned a lot, using LTSpice simulations to compare results from several highly regarded commercial designs.
The choice for the first preamp will be one using two FET ICs with a passive RIAA network between them. My idea is to use an existing RIAA kit sold by AliExpress, which will provide the pcb and some of the parts, then buying the ICs and some specific passive parts to substitute key ones in the RIAA filter.
My question is what to do with the very low frequency vibration, probably around 3Hz, that seems to occur apparently on all belt turntables. That's what I have been told it happens. My friend's turntable, where I made my first capture, also had them. Of course they didn't show on the captured digital tracks.
In my past turntable arrangement, I used a discrete two stage passive preamp, and the vibration was there alright. This preamp used a 470n polystyrene input series capacitor as high pass. To visually cure the vibration I had to lower the capacitance to 100n, which didn't seem to affect the audio quality.
Now I ask: should I worry about that? Can that low frequency intermodulate with higher octaves response?
The circuit I'm using now does not use an input series capacitor.
The I proceeded, using Audacity, to clean the LP from all surface noise and eliminated all the clicks and pops I could find. Capturing at higher resolution, like 96KHz, would allow higher accuracy in the noise elimination. In any case, the files sound excellent. We still have to make a comparison between the original LP and the CD with the processed files and see how they sound.
Now I'm the process of building the RIAA preamp. This has been commented elsewhere, which generated a very constructive discussion, where I learned a lot, using LTSpice simulations to compare results from several highly regarded commercial designs.
The choice for the first preamp will be one using two FET ICs with a passive RIAA network between them. My idea is to use an existing RIAA kit sold by AliExpress, which will provide the pcb and some of the parts, then buying the ICs and some specific passive parts to substitute key ones in the RIAA filter.
My question is what to do with the very low frequency vibration, probably around 3Hz, that seems to occur apparently on all belt turntables. That's what I have been told it happens. My friend's turntable, where I made my first capture, also had them. Of course they didn't show on the captured digital tracks.
In my past turntable arrangement, I used a discrete two stage passive preamp, and the vibration was there alright. This preamp used a 470n polystyrene input series capacitor as high pass. To visually cure the vibration I had to lower the capacitance to 100n, which didn't seem to affect the audio quality.
Now I ask: should I worry about that? Can that low frequency intermodulate with higher octaves response?
The circuit I'm using now does not use an input series capacitor.
Audacity has very nice editing features. Just paint a piece (waveform), select Effects -> Classic filters anf set parameters (toolboxes are different in different versions of Audacity)
Wow and flutter and cartridge resonances are typically below 20Hz, you can use high order filters safely. Everything is reversible of course.
Wow and flutter and cartridge resonances are typically below 20Hz, you can use high order filters safely. Everything is reversible of course.
ive seen several circuits here on DIYAudio. Pete Millet includes one in his LR phono preamp for which you can find the schematic on his website pmillett.com. Also I think Kevin Barrett sells one KABUSA.com
Found Pete Millet's RIAA schematic.
http://www.pmillett.com/LR_phono.html
Two arguable things in it: using AD797s (a problematic chip) and using cored inductors for the filter. That's definitely not the way I'm interested to go through.
More than 90% of the RIAA circuits I have seen do not use inductors for the RIAA filters, just Rs and Cs. This the first version I intend to use.
I can show the simulation curves for response, distortion and noise, using a cartridge load model for this and other options.
But as you can see on the title, I queried about the very low frequency vibration you find in all or most belt turntables, and if it is something I should care about.
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I queried about the very low frequency vibration you find in all or most belt turntables, and if it is something I should care about.
Try with Audacity and listen! Easy to hear actually. At first glance the waveform magically becomes much "cleaner" because low rumbles have surprisingly high amplitude. Modulation disappears! too low freq noise stresses your woofers, specially if they are bass reflex type. This was one big reason for the popularity of closed box speakers way back then.
Phono preamps may have subsonic filters, and one can make those easily. The problem is differences between tts and cartridges, you should know what are problematic freqs and their amplitude.
When I digitized my favourite records I tested my 3 tts and 4 cartridges and 3 preamps. Turntables and cartridges/tonearms have big differences, some make better match. Easy to see them by zooming a clip in Audacity, anaysis tool is also informative. Clips are saved on another computer now, so I can't give examples.
Try with Audacity and listen! Easy to hear actually. At first glance the waveform magically becomes much "cleaner" because low rumbles have surprisingly high amplitude. Modulation disappears! too low freq noise stresses your woofers, specially if they are bass reflex type. This was one big reason for the popularity of closed box speakers way back then.
Phono preamps may have subsonic filters, and one can make those easily. The problem is differences between tts and cartridges, you should know what are problematic freqs and their amplitude.
When I digitized my favourite records I tested my 3 tts and 4 cartridges and 3 preamps. Turntables and cartridges/tonearms have big differences, some make better match. Easy to see them by zooming a clip in Audacity, anaysis tool is also informative. Clips are saved on another computer now, so I can't give examples.
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I never cared for those Thorens with the "springy" suspensions, or those spring-suspended Philips either.
Much too bouncy-bouncy for my liking. - makes them prone to airborne feedback, or bounce just walking past them. (unless you live in a concrete shack)
Plus, being a belt drive, any imperfections in the belt such as kinks, from sitting idle for long periods, and crusty buildup on the platter and motor pulley, can cause issues.
That is why I went to Direct Drive, and Linear Tracking - much more accurate in tracing the grooves the way they were originally cut.
As for any issues with airborne feedback, and taming any rumble noise, these are in the sub 20Hz region.
So in an effective way to eliminate them Rod Elliot's Project 99 https://sound-au.com/project99.htm is a wonderful addition to add right after the RIAA preamp.
It cancels out any of those nasty subsonic frequencies, leaving the intended, hearable music intact.
It also eliminates the natural subsonic noise due to the stylus tracing through vinyl's own floor noise.
By removing these real issues, the amp and speakers are now able to concentrate more power to music, instead of woofer-pumping, wattage robbing subsonics.
No need to play around with tedious settings in some App.
Much too bouncy-bouncy for my liking. - makes them prone to airborne feedback, or bounce just walking past them. (unless you live in a concrete shack)
Plus, being a belt drive, any imperfections in the belt such as kinks, from sitting idle for long periods, and crusty buildup on the platter and motor pulley, can cause issues.
That is why I went to Direct Drive, and Linear Tracking - much more accurate in tracing the grooves the way they were originally cut.
As for any issues with airborne feedback, and taming any rumble noise, these are in the sub 20Hz region.
So in an effective way to eliminate them Rod Elliot's Project 99 https://sound-au.com/project99.htm is a wonderful addition to add right after the RIAA preamp.
It cancels out any of those nasty subsonic frequencies, leaving the intended, hearable music intact.
It also eliminates the natural subsonic noise due to the stylus tracing through vinyl's own floor noise.
By removing these real issues, the amp and speakers are now able to concentrate more power to music, instead of woofer-pumping, wattage robbing subsonics.
No need to play around with tedious settings in some App.
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If you want to achieve the highest possible recording quality - don't do a high order filter at 20Hz. Be sure that your low frequency disturbance is low enough to not interfere with the audio. And then use a linear phase EQ/filter in your DAW to remove it for the finished recording.
But when the rumble is to high - I would prefere some group delay at low frequencies over distorted audio for sure.
But when the rumble is to high - I would prefere some group delay at low frequencies over distorted audio for sure.
Please let me be clear that it was not rumble what I had, and as I said I saw it happened also on another Thorens, with a different arm and a different preamp. Frequency is very low, because you can actually see the woofer moving slowly. But I was expecting to find someone here that did have a belt drive tt.
IMHO all rumble filters are bad for high quality audio, and for such a thing only a first order filter, that is a series cap, would not interfere with the audio quality.
As right now I don't have a RIAA preamp, I can't do the test with audacity. I have professional mics and preamps, so I might pinpoint the frequency. Of course it just happens when you put the record and lower the cartridge onto the surface.
IMHO all rumble filters are bad for high quality audio, and for such a thing only a first order filter, that is a series cap, would not interfere with the audio quality.
As right now I don't have a RIAA preamp, I can't do the test with audacity. I have professional mics and preamps, so I might pinpoint the frequency. Of course it just happens when you put the record and lower the cartridge onto the surface.
Another thing that might be interested to try is a DC Servo, adjusting the frequency on the Servo until the vibration stops. I believe that should be implemented in the first stage. As the servo reinjects the "bad frequencies" in counterphase, it might work better than a cap.
And as I previously suggested, that's a result of SUBSONIC disturbences.
You cannot hear it, but it robs power from the amplifier, and can affect what you CAN hear.
Needless complications with servos and the like that you mention are band-aid fixes - tackle the problem at it's SOURCE - the turntable's output.
Leave the opinions out about rumble filters, the circuit I suggested does NOT disturb or affect anything above the intended sound that you want to hear.
It's a steep 38dB slope that you can design to START at anything BELOW 20Hz - even 10Hz.
I have built and used several of the ESP's P99 systems without ever hearing an issue - just perfect music.
And get yourself a good and decent RIAA preamp to make thing MUCH more simpler.
The arm mass and cartridge compliance can form a mechanically resonant circuit. Some arms and cartridges are a bad combination because the resonance is either up in the audible region or down near the rumble frequencies.
Well the point surely is that a rumble filter is a lot better than the rumble. Perfect does not exist, you need to be pragmatic to achieve improvements, pragmatically a rumble filter is the way to deal with subsonic spurious signals from vinyl, thus improving the quality of the signal in front of you.
A problem with limiting to first order is it cannot do the job of a good rumble filter, you need to drop 20dB or so in about an octave to be effective at knocking out resonances at and below 10Hz.
Exactly.
The ESP filter I mentioned can be 'set' to various -3dB points from 150Hz down to 12Hz, depending on the capacitor values listed on the ESP site.
They result in a relatively sharp 38Db/octave slope, and work pretty damn well.
I chose the 100nF/0.1uF value which give me a slope starting at 27Hz, and I honestly can't tell that it's working or interfering with my music.... but I get absolutely no feedback or rumble issues at high volumes, I love it.
And any 'swaying' of the stylus cantilever from off-center records is also eliminated, which, with warped records, causes that slow 'pumping' of the woofers.
This is part of the electrical output of an active crossover in which ESP P99 is installed. Measured with REW and a Focusrite 2i2. It is set to corner at 15Hz (36dB/octave). Although designed to remove the 0.55Hz rotation artefact of LP, it is also generally useful for protecting woofers and amplifiers from unwanted content in digital material. I wouldn't touch LP with a barge pole, but this is still a most useful ensurance policy of a circuit.
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Don't want to use any DSPs at all. DSPs involve ADC and DAC, and only very expensive have good quality, particularly on the analog stages.
Milsdrewbulch's comment is about the ESP P99 project subsonic filter, as is my previous discussion about it.
There is nothing about it that is 'digital', so why would you even mention that?
We're talking about a simple Analog Circuit design that is very effective at removing unwanted noise from audio.
Perhaps you are confusing ESP with DSP?
We are still takling about RECORDING the LP's?
Don't do the filtering analog - you have way more possibilities and get better quality in digital! The rumble doesn't (seriously) harm A/D conversion but will influence a speaker. But as you remove it before playing -> no problem.
Don't do the filtering analog - you have way more possibilities and get better quality in digital! The rumble doesn't (seriously) harm A/D conversion but will influence a speaker. But as you remove it before playing -> no problem.
