Bottlehead Forum

Other Gear => Phono => Topic started by: rockpassion on May 29, 2017, 07:57:25 PM

Title: Loading a Shelter MK II Cartridge
Post by: rockpassion on May 29, 2017, 07:57:25 PM

I currently have a Shelter 501 MK II cartridge going into a Cinemag CMQEE-3440A stepup transformer then going into my EROS,   The Cinemag has two impedence inputs, 37 and 300 ohm.  I currently use the 37 ohm connection.  What I am wondering is do I have this cartridge loaded correctly.  If not what should be the load and what resistor value would I require? 


Thanks in advance.

Richard

Title: Re: Loading a Shelter MK II Cartridge
Post by: fullheadofnothing on May 30, 2017, 07:55:42 AM

Let's start with some facts. According to the datasheet (http://cinemag.biz/mic_input/CMQEE-3440A.php), your transformers can be wired for 37.5Ω, 150Ω, or 600Ω into a 50KΩ load.

Since I'm a lazy sort who sucks at math, I use the VinylEngine calculator (https://www.vinylengine.com/cartridge_database_tools.php#StepUpLoading) to figure out the turns ratios. 1:36, 1:18, 1:9. That works out to 31dB, 25dB and 19dB of gain.

Looking up your cartridge in cartridge database (https://www.vinylengine.com/cartridge_database.php?m=Shelter&t=any&mod=501&sort=2&Search=Search&sty=&ovlo=&ovhi=&can=&dclo=&dchi=&stid=&masslo=&masshi=&notes=&prlo=&prhi=), we can see that the recommended load is >100Ω, and the output is .5mV

One of the fun things on the database page is if you click on the output level, it will calculate the output of a gain stage. Since your cartridge is relatively hot at 0.5mV, with 31dB of gain, you are feeding your Eros 18mV! 25dB would be 9mV; still pretty hot but far more reasonable. The 600Ω wiring would give a near perfect 4mV.

Furthermore you are loading the cartridge way heavier than recommended by the manufacturer. You can lower the impedance with resistor tuning, but not raise it.

From both a gain standpoint and a loading standpoint, you are using the wrong tap.

This (https://www.vinylengine.com/step-ups-and-mc-cartridges.shtml) is the most useful guide to all of this stuff I have come across. Read through it multiple times.

tl;dr: you should be using the 150Ω tap, and maybe try the 600Ω.

Title: Re: Loading a Shelter MK II Cartridge
Post by: rockpassion on May 30, 2017, 05:11:57 PM

Joshua,

Thanks for the links and recommendation.  I switched to the 150 ohm tap and found it to be much better than the 37.5 ohm tap.  The music is more detailed, quicker and the bass is much better and tighter. 

I did not setup the 600 ohm tap.  Given the little I read maybe I should use that tap instead of the 37.5.  If I did that could I pull that down to 300 to 350 ohms.  I have read a couple of comments on different forums this seems to be a good value to use. 

I really enjoy this cartrigde but my highs are a little shrill at times.  I have played around quite a bit with VTA and VTF and have been able to get this somewhat under control but being into DIY stuff I thought this might help alleviate some glare in the highs. 

Regards

Richard