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Old 29th September 2010, 07:10 PM   #141
Cobra2 is offline Cobra2  Norway
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Default MC-Carts...

WOW! That is impressive work!
Do you have any conclusion on what makes a "low-noise" cart?
(intenal DC-resistance/inductance/?)
Will love to see similar measurements on MM's too

Arne K
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Old 30th September 2010, 06:27 PM   #142
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Very straightforward, after Joachim triggered the idea.

The conclusion is: Signal/noise = output/(Johnson noise from series R)
so you want the most output with the least resistance. Inductance probaby too small to make a difference, but I have not checked that. Bear in mind that this simple calculation is for a flat frequency response, and does not take into account RIAA equalisation. Applying that would alter the numbers, but not the quietness ranking of the various cartridges.

Applying the same notion to moving-magnet cartridges is trickier because the high inductance means that not all the Johnson noise from the series resistance reaches the preamp input, due to the 47K load resistance. I also don't have a large database of MM cartridge characteristics.

However, here are a few back-of-envelope calculations for maximal S/N ratio. The RIAA is taken into account, so is the Johnson noise from the 47K load resistance, but the amplifier is presumed to be noiseless:

Shure ME75ED 2 (R=640 Ohm, L=470mH) S/N= -81.8 dB

Goldring Eroica H (R=77 Ohm, L=200mH) S/N= -82.8 dB

Interesting because the very different cartridge parameters seem to indicate different design philososphies but the maximal S/N is much the same.
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Old 7th October 2010, 07:54 AM   #143
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Ping Douglas!

I checked my link collection and your website bounced, nobody there. Try to Google with no results. Is your website down for good or....
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Old 7th October 2010, 09:25 AM   #144
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Hello Douglas !
I tryed the Low Z input with the Lyra Titan i ( 5.5 Ohm impedance ) and it worked well aurally but i did not do a measurement. Somewhere hidden in the text is the information that for the Low Z case the feedback resistors appear in PARALLEL to the cartridge so the value of the feedback resistors can be raised without worsening the SN much when the cart is a low Z type. Raising the resistor values whould also lessen the burden on the current delivering Opamps. I build a lot of transimpedance stage with theoretical zro input impedance and also in this cases i could not percept a treble loss with my asortment of Low Z carts.
I found another cartridge that is a contender for high SN. It is the Air Tight P1 with 2.5Ohm and 0.5mV. There is a Signature model above that has even a higher ratio of impedance to output voltgae but i did not find te data sheet so far.
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Old 7th October 2010, 09:29 AM   #145
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It is of cause not posible to raise the feedback resistors ad infinitum so a compromise has to be found. As soon as i have the finished product in my house i will do some measurements and experimentation.
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Old 7th October 2010, 09:40 AM   #146
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I found the specs of the Air Tight Supreme. Impedance 1 Ohm, output voltage 0.4mV.
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Old 7th October 2010, 09:55 AM   #147
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Quote:
Originally Posted by Joachim Gerhard View Post
I found the specs of the Air Tight Supreme. Impedance 1 Ohm, output voltage 0.4mV.
9000$?........
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Old 7th October 2010, 10:13 AM   #148
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Yes, this price is insane. I was able to hear the Air Tight Supreme on the weekend with one of my phonostages and it sounded nice. Noise was nearly non existing. There are some less expensive contenders in the new Lyra range and i will post the specs later.
Like it or not, there is a suprisingly robust market for expensive cartridges and i know a lot of people that own them and are perfectly happy with their choice.
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Old 7th October 2010, 11:52 AM   #149
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Mm, what was that fancy Japanese cartridge's name again, for the price of half a condo.
IO-Jou ?

Next, buy a cartridge and get the turntable for free.
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Old 7th October 2010, 12:31 PM   #150
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Getting back to LinearAudio -- I have a suggestion -- you might want to put the illustrations and charts on a "members" website -- and you might want to request GIF's rather than JPEG's from your authors.
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