Phono Cartridge Response Measurement Script

[levimax]

This script is the best! It is now easier to test, diagnose, and fix TT performance than ever before ..... and it's free! Thank you! It is probably easier for me because I use an ADC and digital RIAA so sampling and correcting become trivial compared to messing around with scopes and resistor and capacitor "plugs" and the like and you get a clear picture of what exactly is going on. I think once we get a larger sample of test results even more will be revealed.

One question I have is what is better to use for correcting FR errors minimum phase or linear phase and why? I read about these but not sure how cart mechanical and electrical resonances and mechanical non liniarities are best corrected... or maybe it doesn't matter. So far I have found correcting cart FR response to be way easier than room / speaker correction.

 

[JP]

See below for some P-mount carts and Styli I had. TT is a SL-DD22 which is a cheap plastic Technics DD from the 1980's with auto return and p-mount and of course perfect speed stability. The Sure cart was one that came with a TT some where along the line and I believe is how a worn out stylus measures.

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The better OEM stylus for that body series does a little better. I haven't messed with loading on these in years - can't remember what works best.

 

[levimax]

I always worry about a hardend or collapsed suspension on NOS styli... for these carts what experience do you have with the suspension on NOS styli?

One issue with the SAS Neo sapphire I have is that the overhang was not to p- mount specs... it is a couple mm too long which kind of defeats the purpose. I wonder if that has something to do with the HF boost issue.

 

[JP]

I always worry about a hardend or collapsed suspension on NOS styli... for these carts what experience do you have with the suspension on NOS styli?

I've eight or nine of these and they're all fine. The 202ED/22ES are boron pipe but do not use the TTDD elastomer that turns to goo. I wouldn't recommend a TTDD to anyone who doesn't want to burn money as they're all bad or going bad. There is one retipper who claims the elastomer is fine and it's the tie wire that stretches, but everyone else that has had a few of these open, including myself, calls BS on that one.

The 22ES is bonded and far higher mass than the 202ED.

One issue with the SAS Neo sapphire I have is that the overhang was not to p- mount specs... it is a couple mm too long which kind of defeats the purpose. I wonder if that has something to do with the HF boost issue.

That'd move your null points quite far so distortion would be impacted. I don't think it'd affect FR that much.

 

[JP]

I added Mac installation instructions here #2

 

[Thomas_A]

Thanks for all the work @JP.

Will the XG-7001 get its own correction?

 

[Thomas_A]

Regarding scripts, I tried this one as well, but without luck yet. Not sure if it is the latest version.

#52

 

[JP]

Thanks for all the work @JP.

Will the XG-7001 get its own correction?

Yes, just need to sit down and figure out creating the filter.

 

[JP]

Denon XG-7005 Sweep using 150MLX. The test signals on this record are RIAA.

 

[dlaloum]

Denon XG-7005 Sweep using 150MLX. The test signals on this record are RIAA.

View attachment 263980

From the look of that - the cantilever resonance could be as low as 13 or 14 KHz - where the 2H peaks... - which implies disapointingly high effective tip mass....

 

[morillon]

with thin cantilever boron and very small m-l diam??
in my memory the crew to mount in exotic ultra light cantilever was not so obvious to implement, .. but if posed resonances problems n was not necessarily in the classic audio band ...
there was an old ( like beguinning 80's) technical article on the subject.. would be nice to find it...
moreover audiotechnica has returned on their mdg range vm7** at33 to aluminum while berylium boron etc. have long been their pride
(at first seen seemed to me to be among the lightest mobile crew approaches made... )
(capacitance-rated efforts won't help?)
;-)

 

[dlaloum]

with thin cantilever boron and very small m-l diam??
in my memory the crew to mount in exotic ultra light cantilever was not so obvious to implement, .. but if posed resonances problems n was not necessarily in the classic audio band ...
there was an old ( like beguinning 80's) technical article on the subject.. would be nice to find it...
moreover audiotechnica has returned on their mdg range vm7** at33 to aluminum while berylium boron etc. have long been their pride
(at first seen seemed to me to be among the lightest mobile crew approaches made... )
(capacitance-rated efforts won't help?)
;-)

I have an AT20 with the ATN20ss stylus - I've measured its resonance at well over 20kHz

But from the look of those charts, I strongly suspect that the 150MLX is a substantial step down.

There are only a couple of manufacturers of exotic cantilevers globally - which is why they all tend to be alike I think - and right now they are far from being as good as the best of the mid 80's.

 

[morillon]

measuring old cartdrige like the at20 155-160 etc is questionable as "user" has just shown it with his efforts on the rubber with a sonax and the impact is visibly very sensitive..
it is necessary to consider the resonance side of the rubber cantilever assembly in these cases.. not just cantilever...
;-)
just like at-150mlx..A-t now use conical alumium in 740 750 760
mesureament not old atn-150mlx and atn-740ml seen interresting.. boron vs conical aluminium with same cartdrige...

 

[JP]

From the look of that - the cantilever resonance could be as low as 13 or 14 KHz - where the 2H peaks... - which implies disapointingly high effective tip mass....

But from the look of those charts, I strongly suspect that the 150MLX is a substantial step down.

Around -25dB 2H in the top octave is right there with the best of them. V-15VMR and P100CMK4 actually measure a bit worse at 20kHz. This stylus is a bit hotter than the previous one I had on this body.

 

[JP]

Buckle up.

I'd mentioned here that the script can be used on 'contrived' sweeps. The script slices the audio and runs FFTs on the slices, grabbing the largest bin for each slice. Slices at the same frequency are averaged. This gives us a lot of leeway on test signals.

The big question has always been, how accurate are the test records?

If we playback a spot frequency and slow down the 'table, the amplitude of the signal will decrease 6dB/octave. Likewise, if we speed it up the amplitude will increase 6dB/octave. Thus, if we playback a 20kHz spot frequency at half-speed, we'd end up at 10kHz at -6dB. I've modified one of my SP-10MK3 to do +20/-50%.

By taking 20, 10, 5, 3, and 2kHz spots we can record each one while sweeping the turntable speed from -0% to -50% and stitch together a "sweep" from 1-20kHz. The exact frequency and amplitude of each spot doesn't matter as long as they're both consistent throughout the track. If they are, a 10-20kHz "sweep" made from a single spot frequency track, for instance, will be the true response of the cartridge.

We could then use a variation of the script to create a spot track "calibration" to correct any amplitude errors in the track within the dynamic consistency of the cartridge. This calibration could then be applied to the spot "sweep" to give a corrected frequency response sweep for the cartridge. In turn, this data could then be used to validate sweep tracks on test records, and in the creation of transfer functions to correct them.

EDIT - to be clear, the below is just a comparison of the rundown method vs. the TRS-1007 record - no corrections have been applied to the TRS-1007 plot.

 

[USER]

Lots of questions:
Are you saying that the TRS-1007 is, more or less, accurate after your new adjustment?
What record are you using for the spot frequencies? Is it the TRS-1007 as well?
Could the test record used for that make a difference?

Can't say that I love that slope as it could mean that a lot of cartridges are much worse than I previously thought, lol!

 

[JP]

No adjustment to TRS-1007. Using a CBS record for spots but it doesn’t matter - most important thing with that method is that each slot tracks is consistent in amplitude for the duration.

 

[dlaloum]

measuring old cartdrige like the at20 155-160 etc is questionable as "user" has just shown it with his efforts on the rubber with a sonax and the impact is visibly very sensitive..
it is necessary to consider the resonance side of the rubber cantilever assembly in these cases.. not just cantilever...
;-)
just like at-150mlx..A-t now use conical alumium in 740 750 760
mesureament not old atn-150mlx and atn-740ml seen interresting.. boron vs conical aluminium with same cartdrige...

Hmmm the compounds used for the suspension vary widely - sometimes even within the same manufacturer...

ADC had compounds in their top end ultra high compliance cartridges that degraded very quickly... later production of the same models changed the compound.

The AT's for the most part seem to survive for the long haul very well - the NOS ATN15SS I have seems fine, and measurements look good.

It isn't a case of the one rule fitting all cases.

The Technics TOTL high compliance boron tube styli, are one of the worst examples - their suspensions totally degrade... don't try one of those without a suspension replacement first!

So yes - approach NOS vintage styli (and for MC's - whole cartridges) with caution - the compounds used for that critical suspension, which define the mechanical suspension, it's compliance, the damping etc... - were tightly held secrets.... varied widely between manufacturers, and their state today, varies just as widely...

I have perfectly working vintage Ortofon, AT's, and ADC's... (yeah even though many ADC's had issues!)

I also have an AT440MLa - with the tapered aluminium cantilever.... again not a patch on the old AT20SS

If people are interested I can post measurements I made of that one too.

 

[dlaloum]

Around -25dB 2H in the top octave is right there with the best of them. V-15VMR and P100CMK4 actually measure a bit worse at 20kHz. This stylus is a bit hotter than the previous one I had on this body.

Not looking at its peak - more at the curve profile and where it rises to its peak - the needle will reach it's minimum tracking ability at the resonance frequency of the cantilever, where the resonance itself will interfere with consistent mechanical contact with the groove, resulting in rising distortion - and after the resonance the distortion level drops off....

the cantilever resonance of course has its own multiple harmonics, so if you have the ability to measure high enough in frequency, and the needle profile is fine enough to track at very high frequencies, you should see the harmonics of the resonance both in the F/R and in the distortion.

 

[dlaloum]

Buckle up.

I'd mentioned here that the script can be used on 'contrived' sweeps. The script slices the audio and runs FFTs on the slices, grabbing the largest bin for each slice. Slices at the same frequency are averaged. This gives us a lot of leeway on test signals.

The big question has always been, how accurate are the test records?

If we playback a spot frequency and slow down the 'table, the amplitude of the signal amplitude will decrease 6dB/octave. Likewise, if we speed it up the amplitude will increase 6dB/octave. Thus, if we playback a 20kHz spot frequency at half-speed, we'd end up at 10kHz at -6dB. I've modified one of my SP-10MK3 to do +20/-50%.

By taking 20, 10, 5, 3, and 2kHz spots we can record each one while sweeping the turntable speed from -0% to -50% and stitch together a "sweep" from 1-20kHz. The exact frequency and amplitude of each spot doesn't matter as long as they're both consistent throughout the track. If they are, a 10-20kHz "sweep" made from a single spot frequency track, for instance, will be the true response of the cartridge.

We could then use a variation of the script to create a spot track "calibration" to correct any amplitude errors in the track within the dynamic consistency of the cartridge. This calibration could then be applied to the spot "sweep" to give a corrected frequency response sweep for the cartridge. In turn, this data could then be used to validate sweep tracks on test records, and in the creation of transfer functions to correct them.



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Painful painstaking work... but excellent!!