The Equalizer in Audacity has linear phase.
For vinyl, this is largely irrelevant as you have no idea what the inverse RIAA filters were doing to the phase during mastering.
Kris2,
You’re trying way too hard to get perfection out of an imperfect medium. 
Usually the biggest problem with vinyl is “snap”, “crackle”, and “pop”. …But, hum & hiss can be issues too. …Welcome to analog!
A complete “cleaning” with a strong subsonic filter will lower a lot of bass too, so I want to be careful there
Most records don’t have a lot of super-low bass. The deep bass is rolled-off in most recordings (to put the energy and loudness where it counts) and especially with vinyl because of physical limits.
Just for reference, the lowest note on a standard bass guitar is about 40Hz and those big subwoofers used in live performances and dance clubs are usually “tuned” to go down to around 40Hz, again to put the energy “where it counts”. Of course, you can have lower bass. A 5-string bass goes lower and a kick drum can have lower-frequency energy. A piano goes lower but you’re mostly hearing harmonics. i.e. You can’t feel the bass from a piano in your body the way you feel bass from a bass guitar or drum. And, many home-theater subs go down to 20Hz or lower.
No filter is perfect but digital filters can be pretty-darn good! i.e. You can get a sharp cut-off without excessive ringing. A subsonic filter shouldn’t hurt the sound and it may help (allowing your amplifier & speakers to work “where it counts”).
Listen with your ears, not by looking at graphs! If you’re hearing hum or rumble you can filter it. And yes, “the cure can be worse than the disease”, so listen with your ears to make sure you’re making an improvement.
I am not satisfied with the sound of the VM 540 ML at the moment.
That’s NOT a cheap cartridge. When you get over about $100 USD the differences are subtle and in a blind listening test you might not choose the more expensive one. (And, maybe you wouldn’t choose the one you have. 
) But, the biggest difference is frequency response (assuming no audible tracking distortion on hard-to-track records). And, the frequency response (frequency balance) on the recordings themselves with vary more than any decent cartridge and it’s easy to tweak frequency response (by ear) with equalization. I find a lot of records from the “vinyl days” to be a little dull sounding, so I’ll often boost the highs a few dB. (I assume modern records are better and more consistent, but I haven’t bought a record since I got my 1st CD player.)
Now I want to try RIAA filtering by audacity and just visited > Equalization - Audacity Manual> , but could not find an Equalizer Preset for that purpose.
The problem with that is the preamp. Your phono preamp already has RIAA equalization and the input impedance of a microphone preamp is way too low, and that impedance “mismatch” will knock down the signal level and mess-up the frequency response.
Do I need a complex filter like ‘linear phase’ or FIR? Just a simple low pass 6 dB from 10 Hz would not fit good enough - it should be two functions around 1000 Hz like 6 dB filters with 3 dB at 500 and 2122 Hz?
Ideally, you’d want a playback filter that’s the exact complement of the recording equalization, but of course the phase response of the RIAA recording EQ is unknown. I believe the cutting head and playback cartridge also introduce (unknown) phase shifts. If it’s an older analog recording, the NAB tape equalization also introduces phase shifts. If you have 2-way or 3-way speakers, the crossovers introduce phase shifts.
Thanks for all suggestions.
Very interesting. I now used some notches of very low frequencies: 2, 4, 7, 8 Hz, each with a Q of 1.
Where may ringing appear, is it near the filters frequency, or over the whole spectrum?
That mixing is a good idea. I have to duplicate the stereo tracks first and mix the duplicates back after filtering?
The turntable has a preamp vs. line switch. The capacity of the built in pre amp is more than 150 pF and the capacity remains whether switched to line or not. The cable to the interface adds 50 pF or more. The interface Focusrite scarlett 2i2 3rd should have about 65 k Ohm as far as I know.
Close to the Filter’s frequency.
If you’re using a Nyquist filter (as used in Audacity’s “Low Pass”, “High Pass” and “Notch” filters), you can do it in one step via the Nyquist Prompt.
In this example:
The first line tells Audacity to use “version 4” syntax (the latest, and default version)
track is the selected audio.
notch2 is the notch filter function, with a centre frequency of 50 Hz ad a Q of “2”
The filtered, and unfiltered audio are added together, and the result is multiplied by 0.5
;version 4
(mult 0.5
(sum *track*
(notch2 *track* 50 2)))
A better idea, though rather more complicated to code, is to apply the notch filter only when the audio is relatively quiet. As you noted earlier on in this thread, this is what the “Hum Remover” effect does.
When the sound is loud, the hum will be totally drowned out by the proper audio.
Ringing is only really a problem when there are sudden changes in relatively loud sounds. Any ringing will be considerably quieter than the original sound, so when the original sound is quiet enough, the ringing will be inaudible. In other words, no need to worry about ringing from very quiet sounds.
The frequency response doesn’t seem to be quite right yet. Too much at 10 kHz and too little at higher frequencies.
Now I want to have or write an EQ curve that fits the pickup and its environment.
Some parts of the Audacity-menu for the EQ seem unusable to import own data. So I tried to get my own RIAA-curve bei editing EQCurves.xml or EQDefaultCurves.xml, but the new versions have no effect or are not shown at the selection. Do you have any Information or a ‘how-to’?
The old “Equalization” effect had gathered rather a lot of bugs, so it was rewritten as two separate effects: “Graphic Eq” and “Filter Curve”.
The good news is that the new effects are stable and most of the old bugs are now fixed.
The bad news is that the new effects are not yet very “feature rich”. Additional features will be added in the future.
Importing / Exporting curves are not currently supported. This is on the developer’s “to do” list.
If it’s now sounding “close”, then I’d suggest that you tweak the result by ear using the Graphic Eq.
Both the Graphic and Filter Curve effects can save user presets, but you need to create them manually.
(It’s “possible” to hack the “pluginsettings.cfg” file, but I wouldn’t recommend it).
You can create your own personla curves in Filkter Curve and the use Manage > Save Preset
These can then be retrieved later with Manage > User Presets
WC
You can create your own personal curves in Filter Curve and the use Manage > Save Preset
These can then be retrieved later with Manage > User Presets
WC
Thanks, that helps! I should have found it right away, but the German menu names irritated me a little here.
Some other questions might be more of a topic for an analog forum. Still, it’s nice that this digitization and RIAA equalization seem to be working with Audacity.
Great.
We’re hoping to find some time to add the Import & Export of curves for the next release 2.4.0 (late March hopefully)
Peter.