Phono Cartridge Response Measurement Script

[JP]

(Will you start a new thread regarding "cartridge measurements" only? It would be nice to have a "database", using standardised settings of your script and input data for the measurement. "Cartridge - loading - test record " etc. L-R response with crosstalk, L-R response with distortion")

I was thinking a master thread for script plots with standard metadata in the body of the post so that it's searchable. If I, or someone, wants to get adventurous enough to do IMD, mechanical impedance, tracking, etc. where it's suite of tests, then perhaps a dedicated thread per for those.

 

[JP]

Well not straigt out of the box. We might be able to get it there, though.

We'd need to first build a test setup with very low crosstalk, preferably with active crosstalk cancelling so that we get more than 40dB of separation, as high a value as possible. We could verify that with the QR2010. Then we'd need to sample the other test discs (starting with STR 100) to find the phase relation of the crosstalk inherent in the test disc. Knowing this we might be able to compensate for the inherent crosstalk in the test disc so that we're left with the actual cartridge crosstalk value.

I'd get right on it but all I can offer is a CBS STR 130, the prices they charge for an STR 100 shipped to europe are outrageous. For that kind of money I'd rather buy the Clearaudio TRS 1007.

Where are you located? I'm sure we can get you a copy.

 

[morillon]

AT150MLX_XG-7001.zip

Shared with Dropbox

www.dropbox.com

I say an enormity can be... but why not use the ref signals at 1k of l or r.. and use the sweep??? what i do to be honest

 

[JP]

Because the investigation is crosstalk of sweep tracks and are they useful.

 

[morillon]

maybe...but...
just like the ref tests at 1k ref at 8cm/s of the hugaroton have seems to have been thought only for the measurement of level.. and the test sequence for the crosstalk.. for the crosstalk..

maybe just some brands have not taken care of the sweeps on crosstalk .. designed for the frequency ... and not for this observation of crosstalk etc.
???
etc., etc

(I found the variable explain maly different mesureament !!! not due to the 7001 etc.. it is clear and very interesting..
I'll talk about it sometime ;-)
)

 

[Thomas_A]

AT150MLX_XG-7001.zip

Shared with Dropbox

www.dropbox.com

The left x-talk phase is in-between while the right is out of phase. Means that you probably can equalise x-talk a bit by azimuth, turning counter-clockwise (I think....) seen from the cartridge front. But it is quite tedious work and is only valid for this record.

This is my result (in phase and out-of-phase):

 

[JP]

Not easy on those EPA wands. This does make me think to have the script show the phase correlation, though.

 

[Thomas_A]

Not easy on those EPA wands. This does make me think to have the script show the phase correlation, though.

Would be really nice as an option; separate panel perhaps?

 

[JP]

Could just do it as radians/degrees rather than visual. Thinking of grabbing some samples from around the middle of the file and comparing there.

I'd really like to figure out the once per revolution cyclic anomaly that presents. It shows up very consistently in the distortion plots but less so in the fundamental. Scrubbing?

 

[Thomas_A]

Of the test records I have, there are almost always some issues. The Tacet copy is the only one that are almost completely free from bumps and quirks but then the quality of the tracks are so-so. 1 kHz tracks show -20.5 and -27 dB crosstalk, all out of phase. The Ortofon copy I have shows the best in that regard, but I don't know what they did with the 800-50000 Hz sweep, at least the 800-2000 Hz part.

 

[JP]

The Ortofon was cut by Flo and intended to be a reference, which make it even more of a head scratcher.

I haven’t measured it yet, but this Denon sounds really nice. Never ran a cart at 0.75g before.

 

[JP]

Easy to play with azimuth on this one as the cart is all the way forward to very nearly align right.

 

[Thomas_A]

The Ortofon was cut by Flo and intended to be a reference, which make it even more of a head scratcher.

I haven’t measured it yet, but this Denon sounds really nice. Never ran a cart at 0.75g before.

What is the compliance of that Denon given the 0.75 g VTF?

 

[JP]

First line is dynamic, second is static. I bumped it up to 0.8g.

 

[Thomas_A]

Easy to play with azimuth on this one as the cart is all the way forward to very nearly align right.

View attachment 273284

The TRS1007 - does it favor the right channel as opposed to the Denon?

I have made a cartoon but I am not sure I get this correct.

 

[ariendj]

Where are you located? I'm sure we can get you a copy.

Thanks for the offer! @USER alerted me to the fact that the STR 100 seller on ebay was increasing the price. But on a positive note, he also started to offer international shipping, so I bought one. Should be on its way right now.

About crosstalk: I own two Denon PCC 1000 stand-alone crosstalk cancellers from the 70s. They work really well and come with a special Denon setup disc. Its sole purpose is to enable accurate measurement of crosstalk. They should be quite accurate. I used one of my copies to calculate the crosstalk correction signal for my AT132/ATN152 combo and I could verify that with the B&K QR2010. I got over 9dB improvement on an already pretty good cart. I think I ended up at about 42dB down on the B&K, at 1kHz.

The thing about the ATN132 is that there is no offset between the crosstalk and the test signal, apart from phase inversion. That made correcting it a breeze. I tried to replicate my success with my Technics P33 / Jico Boron SAS combo but it needed an offset between the correction and the signal of interest. Theoretically, a few samples offset should do it, but real life got in the way and I didn't pursue the matter any further.

Anyway, I hope that if I can set up the AT132/ATN152 combo with crosstalk correction and more than 40dB separation once again and verify that with both the Denon and the B&K, I'd be able to characterize the cutting head crosstalk and figure out how to correct for the CBS disk. We'll find out soon-ish, I hope.

 

[JP]

The TRS1007 - does it favor the right channel as opposed to the Denon?

Same record and track with the same 150MLX setup from the XG-7001 plot:

 

[morillon]

there is a fundamental error that runs through all of your practice for crosstalk (and will be finely checked for distortion)..
c is to use these sweeps to measure f-r ... for something other than what they are made for .. clearly they are generally not treated for the rest ..
explains the evidence that its all these aberrant measurements of crosstalk.....

we encounter the same kind of thing with 1k ref level signals.. which are also essentially dedicated to.. the "level"
normal.

i gives you two "school cases" that I have just rechecked..

xg7001
if on sweep for "response in frequencies"... the results are catastrophic in crosstalk, you noticed it constantly..

if we use the two 1k refs that denon presents as "clean".. the results become very correct and coherent LvsR..

same tonearm cartrige
hungaroton:
1k ref 8cm "for level"... a huge imbalance like you come across so often...
but
offers an astonishing battery of tests dedicated to measuring crosstalk.. in the end, it's not common..

I have a 40db..and balanced! L>R R>L..


I fear that it is necessary to pass in general by dedicated tests and often on spot frequencies etc..(even the few disk sweeps that seem less inconsistent should be controlled via spot frequency etc.)
we are not in digital sweep practices etc.
Sorry

 

[ariendj]

I fear that it is necessary to pass in general by dedicated tests and often on spot frequencies etc..(even the few disk sweeps that seem less inconsistent should be controlled via spot frequency etc.)
we are not in digital sweep practices etc.

My findings have been similar. Only two discs have been usable for crosstalk measurements. The Denon, which was produced exclusively for crosstalk measurement and only has a 1kHz test tone, and the B&K frequency sweep that I used to confirm my findings. Every other frequency sweep test disc delivered wildly inconsistant data on the channel opposing the one with the sweep.

What I have found though is that the results from crosstalk at 1kHz can be used to correct the entire frequency band. There is hardly anything to be gained by splitting the signal up into bands and correcting them individually.

My hope is that we can quantify the error in the pressings of JVC/Clearaudio/Elipson/CBS. These discs might all be wrong, but they should be consistantly wrong on every disc of the same type. If we know how to correct the 'wrongness' of the pressing, we might end up with something useful.

I agree that we should also take the distortion levels with the same grains of salt. But right now I do not have any idea how we could deal with the question of "is it the cart or the disc that is distorting?".

 

[Thomas_A]

I just measured the 1 kHz signal of the Denon record. It looks fine.

L->R: -33.2 dB
R->L: -36.2 dB

Both signals are out-of-phase which makes me think there is very little to do to improve it. It is also close the the Ortofon record of around -35 dB for each channel. So the result is different from the sweep.