Cartridge curve compensation in phono MC preamps

the thin end of the wedge
Arno P
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Cartridge curve compensation in phono MC preamps

Post by Arno P » 15 May 2019 21:23

Eventhough MC preamps can be excellent in RIAA accuracy, most MC cartridges spoil the fun wrt to their dB accuracy (0.2-0.5dB RIAA versus a sloped MC curve often starting at 3...6dB at 20Hz and making a dive after that to 0dB or worse and followed by a peak again)

Not as bad as it seems but still enough to wonder if there are MC preamps that have extra selections to compensate for the cartridge curve (besides the loading of course)

I don't mean the different RIAA curves but real options to compensate for the MC cartridge "flaws"

billshurv
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Re: Cartridge curve compensation in phono MC preamps

Post by billshurv » 15 May 2019 23:01

whilst many have an engineered upshelf at HF of up to 2dB I don't recognise the slope you are desribing. Can you point at some examples to help understand?

QUAD preamps used to have exactly what you are looking for with their tilt control but very few modern preamps have that. However easy to DIY once we know what you are trying to adjust.

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Re: Cartridge curve compensation in phono MC preamps

Post by Arno P » 22 May 2019 07:20

It seems one of the few is Graham Slee giving it a thought to separately compensate for the cartridge deviations. Also saw a bit of that in the Luxman EQ-500

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Re: Cartridge curve compensation in phono MC preamps

Post by Arno P » 22 May 2019 07:25

Benz Curve.png
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As an illustration I add the Benz Micro Curve that also sounds as it looks....so no myth here. Regardless of any setting/adjustment/phono-pre, the curve stays like this. With my new LCR tube phono having a couple of dB reduction at 10-20Hz, the low part of the curve gets flatter. I added a switchable "shelving" from 1kHz to 20kHz that lifts approx 4dB at 20 kHz. Not a perfect curve but sounding good again.

Arno P
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Re: Cartridge curve compensation in phono MC preamps

Post by Arno P » 22 May 2019 07:37


billshurv
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Re: Cartridge curve compensation in phono MC preamps

Post by billshurv » 22 May 2019 09:41

Nope never seen that in any cartridge other than yours. I can ask a friend for a FR curve from his LPS for comparison?

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Re: Cartridge curve compensation in phono MC preamps

Post by Arno P » 22 May 2019 10:27

That would be a good one!

billshurv
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Re: Cartridge curve compensation in phono MC preamps

Post by billshurv » 22 May 2019 11:44

Attached is a plot of a Benz LPS on a linear tracking arm using a known good pink noise track which gives exactly the output expected to 30kHz.
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Hans_LPS_45 rpm.jpg
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Arno P
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Re: Cartridge curve compensation in phono MC preamps

Post by Arno P » 22 May 2019 11:54

Expected a horizontal line...but I think I had this before measuring in the FFT mode. RTA with max hold gave the horizontal line.
So, this curve seems to be perfect if it is not a real slope-down....right?

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Re: Cartridge curve compensation in phono MC preamps

Post by billshurv » 22 May 2019 14:13

Pink noise is 3dB/octave slope, so this indicates that its as expected.

Test records get confusing very quickly in this aspect and a number are not as accurate as we might like! And some are RIAA, some are constant velocity and some are a mix. This is about the best pink noise record I have seen.

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Re: Cartridge curve compensation in phono MC preamps

Post by Arno P » 22 May 2019 15:40

Indeed. What did you use for that measurement?

billshurv
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Re: Cartridge curve compensation in phono MC preamps

Post by billshurv » 22 May 2019 16:10

The CHprecision test record. You get it free with their $30k preamp!. I have a copy. What test record do you use?

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Re: Cartridge curve compensation in phono MC preamps

Post by Arno P » 22 May 2019 16:13

I use the Dr Feickert record combined with either the adjust+ software of CLIO in FFT/RTA

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Re: Cartridge curve compensation in phono MC preamps

Post by billshurv » 22 May 2019 16:46

OK I am pretty sure Hans has the adjust+, will get back to you.

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Re: Cartridge curve compensation in phono MC preamps

Post by billshurv » 23 May 2019 10:38

Hi Arno,

Do you have the raw file from adjust+ you can supply me. Then we can get that compared with the same file done on the LPS I showed the FR for above. Hopefully we can cal out the record and get to your actual FR plot.

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