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Old 23rd November 2009, 02:16 PM   #211
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hi michael !
i think you got me.
when Syn08 and i are listening to the same soundlevel, noise contribution of the phonostage is the same simply because SYN08 can reduce his volume control by 6dB if his speakers are 6dB more efficient then mine compensating for the gain of the speakers IF both have the same linear frequency response.
the 9dB for doubling is in the ballpark. i learned it is 10dB but we all have different ears and comparing loudness curves over the years (compare the old Fletcher-Munson to newer reviews, fascinatingly ducumented in the new book by Floyt Tool) it seems that our ears are changing too over the ages.
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Old 23rd November 2009, 02:18 PM   #212
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refeshing john, you are really a practical guy
"wir streiten um des kaisers bart" we say here
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Old 23rd November 2009, 02:25 PM   #213
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hi jan !
i breefly studied OTAS too.
One guy has made an MC stage and i saw a I/U coverter from a guy in east europe too.
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Old 23rd November 2009, 03:18 PM   #214
brianco is offline brianco  Ireland
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Location: Scottish Borders - Kelso; on the famous Tweed River!
wir streiten um des kaisers bart!


My family emigrated when Bismark "unified" the German Principalities! They [with many others] left Prussia for Switzerland.......and ended up in Ireland!
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Old 23rd November 2009, 03:51 PM   #215
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Understanding the psychoacoustic is indeed important, agree with you Joachim!
10 dB what I also learned once before.
Did you meant the book "Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms" by Floyd E Toole?
Amazon.com: Sound Reproduction: The Acoustics and Psychoacoustics of Loudspeakers and Rooms (9780240520094): Floyd Toole: Books
Interestingly noticed in the above Amazon link Siegfried Linkwitz had made a customer review and gave it 5 stars of 5.

Cheers Michael
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Old 23rd November 2009, 03:54 PM   #216
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Quote:
Originally Posted by syn08 View Post
You'd be very happy with BF861 cooled down via a Peltier device. My preliminary results are very good, I can tell that. Evacuating the condensation is not trivial, though.
Syn08,
Check the amateur astronomy DIY sites. They have dealt with condensation problems and triple stacked Peltiers. Some of their DIY CCD cameras rival research grade instruments.

BTW JPL used AD745's in one of the space cameras.
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Last edited by scott wurcer; 23rd November 2009 at 04:09 PM.
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Old 23rd November 2009, 04:03 PM   #217
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here is that crazy phonostage jan :
http://digilander.libero.it/paeng/mc_trs.htm
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Old 23rd November 2009, 04:05 PM   #218
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Quote:
Originally Posted by Joachim Gerhard View Post
would it work ? maybe scott can tell me. anyway i have worked only a little on the values so that is not the finished design.
I'll have to check it out, but that looks like the right idea. You want to be sure to not over or under constrain the problem.

It's just Newton's method, you have two pots that change both variables and hopefully there is a solution with both zero. You could be clever and compute partials and solve for the settings, but if the system is well behaved you can usually just "walk" to the right answer.
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Old 23rd November 2009, 04:23 PM   #219
syn08 is offline syn08  Canada
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Quote:
Originally Posted by john curl View Post
Ultima, good for you. The volume control makes all the difference.
Again, the difference between .3nV/rt Hz and .5nV/rt Hz is trivial, for MOST situations. This is because .3nV represents 5 ohms equivalent noise, .4nV 10 ohms, and .5 nV 15 ohms of equivalent noise. Please remember this is in SERIES with the MC cartridge, itself. So, if you have a phono cartridge with a 10 ohm source, then the ACTUAL noise is 15, 20, and 25 ohms in effective noise voltage the difference then between .3 and .5 in this case is effectively 2.2 dB. Not so very much.
There are plenty of 5ohm high end cartridges today. With such a cartridge, it does't make any sense to use a preamp with 10ohm noise equivalent.
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Old 23rd November 2009, 04:26 PM   #220
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yes, i understand, at least in part. i think the current source could "fight" against the current mirrors. i was trained in the 70th and worked in the high tech (plasma sputtering) industry in the 80th so i am not good yet with circuit simulation. i would really love if somebody whould put that circuit though the paces. i am really to lazy to calculate it with hard mathematics. i heard that was also the reason Conrad Zuse invented the computer. ok it was Bagbage but it never worked. or was it the americans ?
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