Phono Cartridge Response Measurement Script

[VinyLuke]

View attachment 448941

I don't understand.

 

[JP]

I don't understand.

Then my guess is incorrect.

 

[Geogeo]

Measurement, both potentiometers in the sound card set to "5", before recording test signals from the disc.
Is this imbalance ok?
How does it look for you?

 

[MaxwellsEq]

Never did that.

Sorry.

 

[wpbilderback]

Comparison between CBS STR-130 and CBS STR-100 test records

Here is an apples-to-apples comparison of the CBS STR-130 and CBS STR-100 test records. The same cartridge and setup were used for both measurements. The only difference was the test record used.

The STR-130 appears to have a 3-4dB lift between 5 and 20 kHz relative to the STR-100.
Notes: The phono preamp was set to 0pF; the cabling on the tonearm adds around 120pF. This measurement was taken with the V15 VMR/Jico brush in the up position.

 

[JP]

It'd be great if someone knows what the actual capacitance of that phono stage is when set to "0". For the plots, we put the total capacitance the cartridge sees in the title.

 

[JeffS7444]

Ortofon 2M Red, Parks Audio Waxwing, no Derumble

Same, with Derumble feature activated.

 

[dlaloum]

It's helpful to understand the history. The exercise was kicked off to create a script which normalised measurements from different test LPs and presented the Frequency Response, AND distortion etc. on a single graph coupled with manually entered data about the cartridge, preamplifier, ADC, setup etc. In terms of repeatability, it's quite interesting to look at the multiple different graphs of the same cartridge (e.g. VM540) by different people.

Due to the hand built nature of cartridges (particularly the cantilever/suspension/needle) - and variation in inductance within production runs and between L/R - there can be quite substantive and definitely measurable differences between multiple samples even from the same production batch.

Hence (if you are a perfectionist) the need for individual loading adjustment for each cartridge sample to achieve an optimal frequency response.

It can also be worthwhile trying to get hold of multiple examples of the body type, to try to find one that has the inductance matched between the two channels. Typically the larger manufacturers will have multiple models using the same generator, so one can on occasion pick up several of the 'lower end' bodies - without stylus.... the variance in inductance between them can be used as a tuning factor as well... also some models may have metal mountings vs others having plastic mountings - typically the flagship versions have metal, but if you are looking at a high compliance stylus, then opting for the lower weight plastic mount, will often save a g or 2, and provide better results/arm matching.... the AT VM family are rife with opportunities for stylus exchanges!

 

[Balle Clorin]

Ortofon 2M Red, Parks Audio Waxwing, no Derumble
View attachment 453228
Same, with Derumble feature activated.
View attachment 453229

The actual bass is not removed on a normal track, but it sums the channels , so in effect you see the shape of the elliptical derumble filter when only one channel has a signal

 

[JeffS7444]

The actual bass is not removed on a normal track, but it sums the channels , so in effect you see the shape of the elliptical derumble filter when only one channel has a signal

Yes, I assumed that it operated similarly to Douglas Self's Devinyliser and tonality is subjectively unchanged.

 

[watchnerd]

“Subjective reasons” could mean anything. Do you mean “the sound”?

Curious about your choice of XA variant of ART9, given that AT use a Shibata not MR profile on it, whereas the XI variant uses MR. It seems a big compromise to make on a principle of ‘air over iron’.

[Note: the ART9XI does not use MR. It uses a special line contact stylus.]

I chose the ART9XA because I wanted the ultra low inductance of the core-less design (2.5uH vs 25uH of the ART9XI).

In theory, this should make the ART9XA especially immune to frequency response changes in loading, even if used with something like a 1:30 SUT (reflected load of 52 ohms when input into a 47k ohm MM stage).

Granted, there will be greater divider loss at this higher step up ratio, but this is more than made up for in output levels via the higher gain. Comparing low vs high gain of my Hashimoto HM-7 SUT, I get:

Mode	Step-up Ratio	Reflected Load (47k/ratio²)	Divider Ratio	Output Voltage (Effective)	Gain (dB) incl. Divider Loss
15:1	15×	47k / 15² = 209 Ω	209 / (209 + 12) = 0.946	0.2 mV × 15 × 0.946 = 2.84 mV	20 × log(2.84 / 0.2) = 23 dB
30:1	30×	47k / 30² = 52 Ω	52 / (52 + 12) = 0.813	0.2 mV × 30 × 0.813 = 4.88 mV	20 × log(4.88 / 0.2) = 28 dB

Plus, I didn't have any core-less MC carts and wanted to try it out.

 

[Stereo20]

I tried searching for the answer, but apologies in advance if this has already been discussed and I missed it.
When you list the capacitance in pF in graphs, are you referring to the total effective capacitance (preamp + tonearm cables), or just the preamp’s own input capacitance?
Many thanks to anyone who can help clarify this!

 

[JP]

The total the cartridge sees is what’s important.

 

[Stereo20]

Thank you @JP
So the pF on the graphs are the total capacitance

 

[JP]

It’s whatever the person puts. We ask that it be total capacitance. We prefer it to be appropriately measured.

 

[Stereo20]

It’s whatever the person puts. We ask that it be total capacitance. We prefer it to be appropriately measured.

Thanks !
Yes, if it weren’t the total, properly measured capacitance, the whole measurement would be pretty much useless

 

[acd]

Hi, I am trying to extract sweeps using cmdline as shown below. The traceback is added.

The file is the left channel and has been used before, so I assume it's OK.

So - I am not able to figure out what is wrong in my sjplot cmdline?

 

[JP]

It looks like it can't find the pilot tone for the right channel sweep. The most likely cause is that the file has been edited such that the duration between the end of the left sweep and start of the pilot tone for the right sweep isn't as expected.

 

[Digital1955]

@JP Any chance you have a AT-VM760xSL yet? My AT33PTG/II suspension failed (side note, I know a few others that had the same issue on this cartridge within the last few years). I'd like to see what the AT-VM760xSL ends up looking like performance wise.

 

[JP]

Nope - I don’t intend to acquire any more carts.