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Old 29th January 2013, 01:42 AM   #8241
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Actually the avalanche noise in BJTs is very similar to what happens in a zener diode.
Something like 6V Vce is optimal i think.http://www.electronics.dit.ie/staff/...seAnalysis.pdf
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Old 29th January 2013, 01:44 AM   #8242
Salas is offline Salas  Greece
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Lets see about BC337 and 2N4401 then.
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Old 29th January 2013, 01:47 AM   #8243
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When more dynamic range is needed in an MC head i would then go for cascoding.
Anyway, in the Paradise we use more then 6V on the input transistors without cascode and the noise is reported to be very low. Maybe i am a bit neurotic and too careful to avoid noise.
It is a revelation though to listen to an ultra low noise phono stage although the mechanical noise is much higher. This is a bit like listening to a low distortion amp over a higher distortion speaker. Mechanical and electrical noise and distortion do not have the same origin and the ear can differentiate this i think.
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Old 29th January 2013, 01:48 AM   #8244
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I will measure them tomorrow.
Hopefully i am able to show some graphs soon.
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Old 29th January 2013, 01:51 AM   #8245
Salas is offline Salas  Greece
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Quote:
Originally Posted by Joachim Gerhard View Post
It is a revelation though to listen to an ultra low noise phono stage although the mechanical noise is much higher.
Its like when magnifying a dirty object. If the lens is good the object still has dirt but you know what dirt and where.
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Old 29th January 2013, 02:50 AM   #8246
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Somehow my system can put the dirt into other places in the 3 dimensional image where it does not disturb much and the music comes through non the less.
Scratches sound really "short" and occupy only a small space.
A good record cleaning machine helps tremendous.
Some really worn records are hopeless though but choosing the program material is part of the art of vinyl.
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Old 29th January 2013, 09:14 AM   #8247
RCruz is offline RCruz  Switzerland
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Quote:
Originally Posted by Joachim Gerhard View Post
Here you see what we call in German " Kennlinienfeld".
It shows that the Vce curve against idle gets flatter when the idle goes down.
My BC550C and BC560C samples did even better.
http://www.htl-rankweil.at/grass/ftk...latt_BC547.pdf
I noticed the same behaviour in fets... looking at k170 data, http://www.datasheetcatalog.org/data...shiba/1027.pdf , Id - Vds curve shows a flatter line for lower Id, but that means a lower Vgs (-0.4v) and looking at the Id - Vgs curve, we need higher Vgs (near -0.1v) to reach the most linear region.

IMO, in this case the solution is to compromise, use a Vds higher than 8 volts and a higher Vgs (-0.15v)
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Old 29th January 2013, 04:16 PM   #8248
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Here are some screen shots of the curve traces. The last graph shows the BC550C, 560C pair. Up to 2.5mA the curves are congruent.
Attached Images
File Type: jpg DCA751.jpg (1,022.7 KB, 147 views)
File Type: jpg DCA752.jpg (1.02 MB, 138 views)
File Type: jpg DCA753.jpg (426.2 KB, 122 views)
File Type: jpg DCA755.jpg (930.7 KB, 119 views)
File Type: jpg DCA756.jpg (1,013.8 KB, 104 views)
File Type: jpg DCA75 BC550C, 560C.jpg (422.3 KB, 65 views)
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Old 29th January 2013, 04:26 PM   #8249
Salas is offline Salas  Greece
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Few small high Hfe BJTs are going to prove great for symmetric without plenty of noisy degeneration or extensive paralleling with a Cob penalty I am afraid.
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Old 29th January 2013, 04:39 PM   #8250
FdW is offline FdW  Netherlands
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Joachim, your pc comes with a tool called 'snipping tool', I'm sure that this will be easier to use than pictures
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