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Old 7th February 2012, 01:59 AM   #5211
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I get so low self noise in my professional lab because i use 24Bit AD-DA converters with gain ranging, so i drive them in the optimum dynamic range.
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Old 7th February 2012, 03:13 AM   #5212
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http://www.ortofon.com/images/storie...webversion.pdf
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Old 7th February 2012, 03:14 AM   #5213
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Products - Cartridges - MC Anna - Diamond
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Old 7th February 2012, 03:16 AM   #5214
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TPE versatility | Ortofon Microtech
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Old 7th February 2012, 03:49 AM   #5215
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Here is the constant current source debate in detail. As far as i can tell we are taking about a maximum error of 2dB.http://www.linearaudio.net/userfiles..._v1_pub(3).pdf
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Old 7th February 2012, 06:48 AM   #5216
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That noise discussion really bugged me. Phono Stages come and Phono Stages go at Maison Gerhard. Often i have not my best stages at home because they are on a loan. That situation is unbearable so i started to think about a REAL MPP that does not leave the house any more. To solve the noise issue ones and for all i designed a stage that consists of a pre-pre and a separate MM stage. That way i can test new input stages without that they need a RIAA. That pre-pre should be the lowest noise possible. So far the record was a single ended parallel symmetric transimpedance stage with 4 ultra low noise BJTs run quite hot, the same that i would like to use in the Masterpiece. I brought the noise resistance down to ca. 3 Ohm, most of the noise comes from resistors i need to set the gain and keep distortion under control. There are no emitter resistors. The signal goes straight into the emitters. That is a S/N of -82dB to -84dB, depending how it is measured or calculated. To improve on that i wanted a balanced input without the 3dB penalty so i designed a passive device, call it a "special" transformer. After consulting with several audio transformer makers and trying many prototypes i found a very satisfying solution. The noise impedance with the input shorted is only 0,75 Ohm. So without the cartridge the SN is even better by a factor of 4 giving over -90dB signal noise. This is held down to under 200Hz, after that frequency it is unavoidable that some hum is picked up. I even designed a "special" shorting plug because i found that even 20cm shielded-balanced cable shorted at the input picks up more noise then the pre.pre itself is capable of. To measure the noise more faithfully i use a relative method that does not show absolute readings but compares the noise of the phonostage to the cartridge output at 8cm-sec P-P. My Titan puts out a little bit less then 1mV under this conditions so the peak that you see on the black trace at 1kHz is actually at -60dB and not at -50dB. That makes the plots i will show you even more miraculous. Shown are the output of the Titan, the noise of the phonostage with the Titan connected, then with the cable shorted and then with the shorting plug. I will also make a measurement later that compared the "Diamond Dove" how i call it to the SAM, that is my lowest noise Fet design.
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Old 7th February 2012, 09:18 AM   #5217
hesener is offline hesener  Germany
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Originally Posted by Joachim Gerhard View Post
Yes, or he has not measured both inputs in tandem, balanced.
thats (unfortunately) the case.... working on my measurement hardware....
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Old 7th February 2012, 10:08 AM   #5218
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Fine, that is easy to overlook.
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Old 7th February 2012, 10:11 AM   #5219
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I found that the 50Hz tone with overtones comes from my turntable motor. When i switch it off it is gone. It is really funny to crank the system and then hear the motor starting. It goes like mmmmmmmhhhhhhhhhhummmmmm, but softly. I will make a Mumetall shield.
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Old 7th February 2012, 12:35 PM   #5220
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Quote:
Originally Posted by Joachim Gerhard View Post
Often i have not my best stages at home because they are on a loan.
Often the case with designers, has been my experience.
The designer of my Classé Omega phono stage plus line amp mk3 has a surround setup with 4 of your Virgo (*) model plus subwoofer (good deal on them through friend Jochen Räke), last time he drove them with an Audionet ensemble.
Similar to cooks, star grade chefs are quite often fastfood junkies.

(* time when you used an Adyton pre/power set)
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