AudioCircle

Industry Circles => Vista Audio => Topic started by: neobop on 21 Mar 2013, 09:20 pm

Title: Load the Magnets
Post by: neobop on 21 Mar 2013, 09:20 pm

Great article from 2008.
http://www.tnt-audio.com/sorgenti/load_the_magnets_e.html

Preferred load for M-97 is 62K, 250pF

AT-440MLa - 32K, 150pF

AT-95E - 47K, 150pF

Clearaudio MM - 47K, 100pF

Denon DL-160 - 1K to 47K

Stanton 981LZX - 250 ohm
Pickering 7500 - 250 ohm

Ortofon M20FL Super - 53K, 300pF

Ortofon M30, 40 - 39 to 47K, 200pF?

All subjective  What's your load?
neo

Title: Re: Load the Magnets
Post by: Audiovista on 22 Mar 2013, 01:15 am

Very useful link - thanks for posting!

Title: Re: Load the Magnets
Post by: *Scotty* on 22 Mar 2013, 03:20 am

Here is an RTA plot taken at the listening position using Hifi News & Record Review Test Record pink noise track.
The cartridge is an AT 440 ML with the inductance of the coils canceled out. I used REW and the Dayton Audio UMM-6.
(http://www.audiocircle.com/image.php?id=77501&size=large)
The pink noise on the record appears to start at 15Hz on the low end
(http://www.audiocircle.com/image.php?id=77502&size=large)
Obviously we would know more if I could measure the response electrically from the output of the phono stage rather than acoustically at the tail end of the chain at the listening position.
At this point I couldn't tell you if the record is flat out to 20kHz or not.
Scotty

Title: Re: Load the Magnets
Post by: neobop on 22 Mar 2013, 01:12 pm

Quote from: Audiovista on 22 Mar 2013, 01:15 am

Very useful link - thanks for posting!

Hi Boris,
The fellow who wrote that article is an EE.  He occasionally posts on VE and Asylum.  He also contributed to a thread on VE called Cartridge Loading Explained.  It was started by CarlosFM (another EE) a few years back. Here's the latest, page 21.  Check this out:
http://www.vinylengine.com/turntable_forum/viewtopic.php?f=19&t=6674&sid=95d671cacdd2cce7eb87766ae61f56e0&start=300

neo

Title: Re: Load the Magnets
Post by: neobop on 22 Mar 2013, 01:25 pm

Quote from: *Scotty* on 22 Mar 2013, 03:20 am

Here is an RTA plot taken at the listening position using Hifi News & Record Review Test Record pink noise track.
The cartridge is an AT 440 ML with the inductance of the coils canceled out. I used REW and the Dayton Audio UMM-6.
Scotty

Hi Scotty,
Do you remember which thread on vinyl circle where you first posted this?

This involves the use of a second, "identical" cart. 
neo

Title: Re: Load the Magnets
Post by: *Scotty* on 22 Mar 2013, 04:42 pm

That's the thread you started on moving magnet phase shift,
http://www.audiocircle.com/index.php?topic=92138.0
Scotty

Title: Re: Load the Magnets
Post by: Audiovista on 23 Mar 2013, 11:54 pm

You guys got me thinking... Perhaps it would make sense to have a simple circuit that would make it possible to use regular DMM to measure linearity of the cartridge/preamp output, using test records. Nothing unheard of, precision rectifier followed by a low pass filter would probably do the trick - get accurate DC output proportional with the amplitude of the test signal. Of course, devil is in the details - there is a good reason why wide bandwidth accurate voltmeters cost enough not to be part of a typical audiophile's toolbox of tricks. But I'll think some more tomorrow, it's been a long day for me....