ADC XLM/VLM/QLM coil resistance

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audiopile
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ADC XLM/VLM/QLM coil resistance

Post by audiopile » 28 Feb 2019 04:46

The manuals/specs in the library list the coil impedance of the ADC XLM /VLM series as 750-800 or more. The one body from this series I have measures about 350 ohms across both pairs - I'm thinkin of tryin a XLM series 2 improved stylus on this body -but while it may physically fit -will this electrically match ? Has anyone measured the coils on their XLM series cart bodies ?

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Re: ADC XLM/VLM/QLM coil resistance

Post by tep392 » 28 Feb 2019 16:41

I think it depends on the which revision you have. I have been researching this recently, and this is what I have compiled from various internet searches. Don't take it as gospel. This is the internet after all. I have measured a QLM30mkiii and it was close to 350 ohm. I have a QLM34 on order and will check it out. If you have an original XLM, before mkii, then I believe it is 300 mh, so your resistance measurement might not be far off. I have read, also on the internet, that mismatching the stylus series and body inductance can affect high frequency response.

XLM
300 mh ??? ohm

XLM mkii
350 mh 625 ohm

Astrion, ZLM, XLM mkiii, XLM mkii improved
580 mh 820 ohm

QLM 32-36 Mk III
580 mh 820 ohm

QLM 30 Mk III
270 mh 350 ohm

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Re: ADC XLM/VLM/QLM coil resistance

Post by audiopile » 28 Feb 2019 17:47

Thank you -there's a QLM 30 mkIII stylus in this body -so the obvious conclusion is that's what it is and it does measure 350 ohm +/- a few ohms -OK -so time to look for the right body for the XLM mkII improved stylus-my ADC body isn't going to work well with that model needle.

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Re: ADC XLM/VLM/QLM coil resistance

Post by tep392 » 28 Feb 2019 18:11

I actually have an experiment planned. I have a QLM36 stylus that I will test in both the 270mH and 580mH bodies. I will use a test record and my trusty oscilloscope to measure the frequency response from 20Hz-20kHz. This should quantify the impact of bodies inductance values. At least for the QLM36 over this frequency range.

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Re: ADC XLM/VLM/QLM coil resistance

Post by totem » 28 Feb 2019 23:51

The above chart is wrong in at least 1 category.

The QLM 32 is a lower mH figure than the QLM 36 mk III which measures at the stated 580 mH or 820 ohm.
That is of course if the body is an OEM 32 it gets confusing but measuring is the only way to confirm.

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Re: ADC XLM/VLM/QLM coil resistance

Post by tep392 » 02 Mar 2019 02:49

Like I said, I cant guarantee the accuracy of these numbers. I found a lot of conflicting specs. For instance, one table I found said all qlm's from 30 to 36 were 580mH, which is absolutely false. I've even found references saying the qlm33 is eliptical and I know for a fact it was conical. I have one.

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Re: ADC XLM/VLM/QLM coil resistance

Post by audiodk » 03 Mar 2019 01:29

Here is the info I have
ADC-XLM-SPECS1X.jpg
(148.31 KiB) Downloaded 134 times
ADC-QLM-1971-SPECSX.jpg
(158.82 KiB) Downloaded 169 times
ADC-QLM-1975-SPECSX.jpg
(182.03 KiB) Downloaded 134 times
ADC-QLM-SPECS1X.jpg
(159.83 KiB) Downloaded 132 times

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Re: ADC XLM/VLM/QLM coil resistance

Post by audiodk » 03 Mar 2019 01:34

Here's a table with the VLM specs
ADC-VLM-SPECS1X.jpg
(137.68 KiB) Downloaded 132 times

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Re: ADC XLM/VLM/QLM coil resistance

Post by audiopile » 03 Mar 2019 06:51

Thanks -those specs get close enough to my QLM (??) body to make it unlikely a XLM series II improved stylus is going to work on it. This is the most complete list of specs for these nice old ADC's that I've seen -a fine example of the folks who make VE great.

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Re: ADC XLM/VLM/QLM coil resistance

Post by tep392 » 04 Mar 2019 23:15

I just picked up a QLM34 MkIII and coil resistance measures 823/825.

Regarding the QLM30 MkIII, I question the 580mH spec in the above chart. Two of us in this thread have measured these at ~350 ohms. I've read elsewhere that the 30MkIII shipped with the 270mH bodies.

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Re: ADC XLM/VLM/QLM coil resistance

Post by tep392 » 24 May 2019 15:27

audiodk wrote:
03 Mar 2019 01:29
Here is the info I have
ADC-XLM-SPECS1X.jpg
ADC-QLM-1971-SPECSX.jpg
ADC-QLM-1975-SPECSX.jpg
ADC-QLM-SPECS1X.jpg
I downloaded these charts for reference back when they were originally posted. I was looking at them today and noticed that the stylus tip for the QLM30 MKIII in the last chart is shown as 0.3x0.7. Can this be true? Would be good to correct the chart if this is an error.

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Re: ADC XLM/VLM/QLM coil resistance

Post by audiodk » 24 May 2019 18:38

tep392 wrote:
24 May 2019 15:27
audiodk wrote:
03 Mar 2019 01:29
Here is the info I have
ADC-XLM-SPECS1X.jpg
ADC-QLM-1971-SPECSX.jpg
ADC-QLM-1975-SPECSX.jpg
ADC-QLM-SPECS1X.jpg
I downloaded these charts for reference back when they were originally posted. I was looking at them today and noticed that the stylus tip for the QLM30 MKIII in the last chart is shown as 0.3x0.7. Can this be true? Would be good to correct the chart if this is an error.

Here is the corrected chart.
ADC-QLM-SPECSX.jpg
(141.23 KiB) Downloaded 73 times

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