Fun with vinyl measurements

[JP]

Ya, but too many unknowns comparing CD and LP.

 

[melloncolliecat]

Maybe time consuming, but... you could record both track B1 and B6, compare both vs CD and then compare the differences. @Thomas_A

 

[Thomas_A]

Ya, but too many unknowns comparing CD and LP.

In general I agree. I think though this LP and CD are very well matched. Will do some more tests.

 

[Thomas_A]

Maybe time consuming, but... you could record both track B1 and B6, compare both vs CD and then compare the differences. @Thomas_A

Will do some further tests.

 

[Balle Clorin]

In my experience 4 out of 5 times ripping a CD or YouTube and comparing with vinyl or YouTube vinyl playback actually reflect the cartridge response quite well

 

[aaaakkkk]

What profile? An MR on TRS-1005 shows less than half a dB difference (IIRC) between inner and outer.

It is most logical to conclude that the sound engineer who cut the lacquer disk used a special device or equalizer and raised the treble, as they are aware of the problem of the treble region falling.
I have seen an interview with an engineer who explicitly stated that he raises the treble on the equalizer on the track closest to the center of the disc during the recording of the lacquer disk.
For example, the description of the Technics SFC-TR100 includes information that they used a special technology to ensure that the final tracks were distortion-free.
I also compared the frequency response of many different records and CDs, and yes, some editions have a minimal decrease in high frequencies towards the center of the disc, but most (90%) have a significant decrease in high frequencies.

Recently, while reading an old magazine, I came across information that even before being recorded on a lacquer disc, the soundtrack undergoes frequency correction, as lacquer does not record all frequencies equally.
Therefore, some of the earliest CDs that used such corrected soundtracks had an unacceptable sound quality.

 

[Sal1950]

Recently, while reading an old magazine, I came across information that even before being recorded on a lacquer disc, the soundtrack undergoes frequency correction, as lacquer does not record all frequencies equally.

There are lots of manipulations that have to go into a original flat master before it can be cut on vinyl and be playable on a average turntable.

Mastering for Vinyl | Envato Tuts+

Some people say that a master for vinyl isn't necessary. That a well mastered track will translate equally as well on CD, as it would to vinyl. I say that this simply isn't true. There is no...

music.tutsplus.com

What is Mastering for Vinyl?

Mastering for vinyl is the process of creating a separate master that can be cut into a vinyl record without added unwanted distortion.

www.sageaudio.com

Therefore, some of the earliest CDs that used such corrected soundtracks had an unacceptable sound quality.

Hard to know how much this went on, any engineer doing this should have been made to face a firing squad.
It was his job to understand the differences between a CD and Vinyl master so either he was an ignorant idiot or just so greedy
to get out the new CDs he couldn't-wouldn't take the time to access the flat master.

 

[Balle Clorin]

I was quite surprised to see response change with the new sorbothane mat. I thought first it was RIAA difference but even with the same RIAA I get er a lower amplitude on the high frequency resonance with the new thinner( 3mm vs 5mm) Sorbothane mat form Isolate IT. Plot below without clamp(weight)

Is it the Sorbothane or the 2mm height difference, hard to tell, I cannot go back the sticky mat is stuck. It woul be nice if somebody could repeat and verify the observation

 

[Balle Clorin]

This is a AI generated python script for presenting FFT and IMD-INTERMODULATION DISTORTION- using a test record LB202.
Test track has 315 Hz and 3150hz in 4:1 ration. no RIAA eq. Use at own risk, AI can help you modify it to other test frequecies, like 60Hz and 7000hz
Rename .txt to .py


DO NOT ask me to explain anything, it is all AI genereted on my request. I do not have test files to verify the results..use at own risk

View attachment 480446

This result is in the same order as a simple visual/manual sideband evaluation gives, but lower the REW calculation reports. I guess it can work to se relative changes ,but not absolute correct values

View attachment 480450

View attachment 480447
View attachment 480448
View attachment 480449

The first file is based in amplitude modulation effects , the second is based on spectrum FFT more like REW does

View attachment 480491

but the script dos this-using average funtamentals ,funny. I thought it should be relative to F2 the 3150hz

The IMD‐percentages are always computed from the linear amplitude ratios, not directly from the dBFS values. Here’s the recipe:

1. We measure four linear amplitudes from the FFT:
   • A₁ = amp at f₁ (Hz)
   • A₂ = amp at f₂ (Hz)
   • A_diff = amp at |f₂–f₁| (Hz)
   • A_sum = amp at f₁+f₂
2. We pick a reference A_ref for dBFS (in our script that’s max(A₁,A₂)), and compute dBFS:
   dBFS_x = 20·log₁₀(A_x / A_ref)
3. We form the average fundamental amplitude:
   fund_avg = (A₁ + A₂) / 2
4. The 2nd-order IMD percentages are then
   IMD_diff% = 100·(A_diff / fund_avg)
   IMD_sum% = 100·(A_sum / fund_avg)

Because Aₓ/fund_avg is a pure linear ratio, the printed “0.995%” comes from:

• f₂ @ –17.7 dBFS ⇒ A₂ = 10^(–17.7/20) ≃ 0.1337
• f₁ is at 0 dBFS ⇒ A₁ = 1.0
• • ⇒ fund_avg = (1.0 + 0.1337)/2 = 0.56685
  • diff @ –45.0 dBFS ⇒ A_diff = 10^(–45.0/20) ≃ 0.00562
    ⇒ IMD_diff% = 100·(0.00562 / 0.56685) ≃ 0.992% → ≈ 0.995%
    Likewise for the sum sideband:
  • sum @ –36.4 dBFS ⇒ A_sum = 10^(–36.4/20) ≃ 0.0151
    ⇒ IMD_sum% = 100·(0.0151 / 0.56685) ≃ 2.66% → ≈ 2.684%
    In short, dBFS just tells you how big each Aₓ is relative to the loudest fundamental. The IMD% is then the linear ratio of the sideband amplitude to the average fundamental amplitude, times 100%.

doing it relative to F2 increases % of course
── Left Channel ────relative to f2 3150hz─────────────────────────────────────
f1 @ 316.57 Hz : 0.0 dBFS
f2 @ 3140.34 Hz : -17.7 dBFS
diff @ 2827.59 Hz : -45.0 dBFS IMD_diff% = 4.299%
sum @ 3456.74 Hz : -36.4 dBFS IMD_sum% = 11.593%
Avg IMD% = 7.946%

── Right Channel ────relative to f2 3150hz─────────────────────────────────────
f1 @ 316.57 Hz : 0.0 dBFS
f2 @ 3140.34 Hz : -17.8 dBFS
diff @ 2827.83 Hz : -37.6 dBFS IMD_diff% = 10.200%
sum @ 3456.84 Hz : -31.8 dBFS IMD_sum% = 19.782%
Avg IMD% = 14.991%


f1 @ 316.57 Hz : 0.0 dBFS
f2 @ 3140.34 Hz : -17.7 dBFS
diff @ 2827.59 Hz : -45.0 dBFS IMD_diff% = 0.995%
sum @ 3456.74 Hz : -36.4 dBFS IMD_sum% = 2.684%
Avg IMD% = 1.840%

── Right Channel ────relative to average level of F1 and F2─────────
f1 @ 316.57 Hz : 0.0 dBFS
f2 @ 3140.34 Hz : -17.8 dBFS
diff @ 2827.83 Hz : -37.6 dBFS IMD_diff% = 2.338%
sum @ 3456.84 Hz : -31.8 dBFS IMD_sum% = 4.534%
Avg IMD% = 3.436%

Made a new version REV7 that check out perfectly with test file with Sidebands 20db below F2 upper tone. This represent 10% distortion on each side band and this is exactly what the script returns! Not quire sure how iMD should be presented as the sum of sidebands or RMS or what. This is work in progress... For now it is shown like this for 2 sidebands at -20db each..
Using the IMD RMS would give (10^2+10^2)^0.5=14%
NOTE:So far the script only consders 2 order IMD, 3rd order is not included

 

[Thomas_A]

Will do some further tests.

I have compared tracks LP vs CD of the REM LP. Although there are fluctuations there is a small trend, loosing perhaps 1 dB at the end. Setting is 240 pF/47 kOhm.

 

[Thomas_A]

View attachment 480695


I was quite surprised to see response change with the new sorbothane mat. I thought first it was RIAA difference but even with the same RIAA I get er a lower amplitude on the high frequency resonance with the new thinner( 3mm vs 5mm) Sorbothane mat form Isolate IT. Plot below without clamp(weight)

Is it the Sorbothane or the 2mm height difference, hard to tell, I cannot go back the sticky mat is stuck. It woul be nice if somebody could repeat and verify the observation

View attachment 480698

So the sorbothane mat is not possible to remove?

 

[Balle Clorin]

Can be done,, but a mess , need 3 -4 hands , strains the bearing, may rip.

Easier to leave it on . Hardly any effect on cogging noise. Cogging is inherent platter speed variation .mat may have better effect on feedback ringing

 

[JP]

It is most logical to conclude that the sound engineer who cut the lacquer disk used a special device or equalizer and raised the treble, as they are aware of the problem of the treble region falling.
I have seen an interview with an engineer who explicitly stated that he raises the treble on the equalizer on the track closest to the center of the disc during the recording of the lacquer disk.
For example, the description of the Technics SFC-TR100 includes information that they used a special technology to ensure that the final tracks were distortion-free.
I also compared the frequency response of many different records and CDs, and yes, some editions have a minimal decrease in high frequencies towards the center of the disc, but most (90%) have a significant decrease in high frequencies.

Recently, while reading an old magazine, I came across information that even before being recorded on a lacquer disc, the soundtrack undergoes frequency correction, as lacquer does not record all frequencies equally.
Therefore, some of the earliest CDs that used such corrected soundtracks had an unacceptable sound quality.

Sure, there are real and imagined challenges and solutions. Bit ironic that one you cite is likely to cause more problems than it solves. Regardless, on a test record the objective is to cut the signals the same and not compensate for playback capability, as that's what is being tested.

 

[aaaakkkk]

Sure, there are real and imagined challenges and solutions. Bit ironic that one you cite is likely to cause more problems than it solves. Regardless, on a test record the objective is to cut the signals the same and not compensate for playback capability, as that's what is being tested.

So how do you explain the ~4dB drop at 15,000Hz at ~18 minutes into each side? On so many releases? Or do you think it doesn't exist?

 

[JP]

So how do you explain the ~4dB drop at 15,000Hz at ~18 minutes into each side? On so many releases? Or do you think it doesn't exist?

On a test record? With what profile stylus?

 

[Thomas_A]

Been listening a while with the 240 pF 47k load of the Shure V15V SAS/B and it sounds really fine across both outer and inner grooves. I am really hoping for a new high quality test record from @vinylflo . It would be most velcome.

My wish is:
1 Left sweep 20-20000 Hz
2 Right sweep 20-20000 Hz
3 Left sweep 1000-45000 Hz
4 Right sweep 1000-45000 Hz
5 1 k left ref level
6 1 k right ref level
7-12 50-100 um at 315 Hz
13-16 repeat of track 1-4

Side two
1 3150 Hz mono
2 1 kHz mono ref level rest of side (or choice of other useful mono tracks)

 

[morillon]

Been listening a while with the 240 pF 47k load of the Shure V15V SAS/B and it sounds really fine across both outer and inner grooves. I am really hoping for a new high quality test record from @vinylflo . It would be most velcome.

My wish is:
1 Left sweep 20-20000 Hz
2 Right sweep 20-20000 Hz
3 Left sweep 1000-45000 Hz
4 Right sweep 1000-45000 Hz
5 1 k left ref level
6 1 k right ref level
7-12 50-100 um at 315 Hz
13-16 repeat of track 1-4

Side two
1 3150 Hz mono
2 1 kHz mono ref level rest of side (or choice of other useful mono tracks)

Silence...rumble.
Tonearm frequency...
IMD (s) as an aid to tonearm/ cartdrige adjustments...
Frequencies (historically 315hz) for anti-skating adjustments at not too high a velocity. Or track smooth.


(A thought after observing the games taken from the 70s, etc., regarding adjustment aids with or without measurements (which Analog Majik did, taking advantage of the oblivion, when nothing revolutionary was already there in the 70s/80s),
and here we talk a lot about advanced characterization of cartridges (,if it is not the charge of the mm easy to observe modify and wf ) etc., less adjustment assistance, I find ;-) )

 

[Balle Clorin]

Been listening a while with the 240 pF 47k load of the Shure V15V SAS/B and it sounds really fine across both outer and inner grooves. I am really hoping for a new high quality test record from @vinylflo . It would be most velcome.

My wish is:
1 Left sweep 20-20000 Hz
2 Right sweep 20-20000 Hz
3 Left sweep 1000-45000 Hz
4 Right sweep 1000-45000 Hz
5 1 k left ref level
6 1 k right ref level
7-12 50-100 um at 315 Hz
13-16 repeat of track 1-4

Side two
1 3150 Hz mono
2 1 kHz mono ref level rest of side (or choice of other useful mono tracks)

I want a zenith/ HTA track mono with Intermoduation tones ,placed at outer null 120,9mm or so,
And the same for VTA, but for VTA the track must be vertical modulated only.

 

[Thomas_A]

I want a zenith/ HTA track mono with Intermoduation tones ,placed at outer null 120,9mm or so,
And the same for VTA, but for VTA the track must be vertical modulated only.

Yes. Some or those tracks would be nice. Flo mentioned one side with a mono head only, but I am not sure what kind of tracks he has in mind. One is for sure the 1 kHz ref level with very high quality, used for calibration of level. More for the tech side during cutting I guess.

 

[morillon]

Yes. Some or those tracks would be nice. Flo mentioned one side with a mono head only, but I am not sure what kind of tracks he has in mind. One is for sure the 1 kHz ref level with very high quality, used for calibration of level. More for the tech side during cutting I guess.

1khz ( 5cm or 8cm?)
for azimut....? or... crosstalk?
;-)