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Old 12th December 2011, 06:24 AM   #1
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Default The best preamplifier

Hi All
This is a design I did in 5 years!
It has been many favorite friend. Especially in 2011 I have improved dramatically! To me this is my best pre tube using 6H30Pi or 6Dj8 ...
I opened the topic here, because this is the place to discuss all matters of Audio uses tube!

Sounds very realistic detail, balance!
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Old 12th December 2011, 09:25 AM   #2
Luke is offline Luke  New Zealand
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Hello Quanghao,

whats the bias and why is the gain so high for a linestage? I thought you said somewhere it was less than unity gain?
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Old 12th December 2011, 10:17 AM   #3
DF96 is offline DF96  England
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Miller effect? It would need to be driven from a low impedance source, otherwise some HF cut is likely - it could sound smooth (i.e. inaccurate).
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Old 12th December 2011, 10:24 AM   #4
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Quote:
Originally Posted by DF96 View Post
Miller effect? It would need to be driven from a low impedance source, otherwise some HF cut is likely - it could sound smooth (i.e. inaccurate).
Presumably, it will have a level control, which will allow the sound to change spectral balance at different volume settings.
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Old 12th December 2011, 10:38 AM   #5
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Actually tubes input capacitance is less than most semi-insulators especially if talking about something like FE86 or KT88.

However personally I would prefer mu-followers for triodes like 6N6P -30P, 6DJ8
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Old 12th December 2011, 11:27 AM   #6
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Quote:
Originally Posted by DF96 View Post
Miller effect? It would need to be driven from a low impedance source, otherwise some HF cut is likely - it could sound smooth (i.e. inaccurate).
Yes!
This cap Miller = 10pF!
Output impedance about 500R
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Old 12th December 2011, 11:37 AM   #7
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Quote:
Originally Posted by Luke View Post
Hello Quanghao,

whats the bias and why is the gain so high for a linestage? I thought you said somewhere it was less than unity gain?
+ B= 160V
One Tube = 17.5 mA
One channel need ~35mA
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Old 12th December 2011, 11:40 AM   #8
SY is offline SY  United States
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Yes!
This cap Miller = 10pF!
How do you arrive at that number? From the datasheet values, one would expect about 12-15 times higher.
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Old 12th December 2011, 11:42 AM   #9
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How do you arrive at that number? From the datasheet values, one would expect about 12-15 times higher.
Hi!
By practical experience!
I practice many times and found that the best results!
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Old 12th December 2011, 11:52 AM   #10
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OK, so no measurement or calculation, just assertion from the seller.

Using a more conventional engineering approach, one should expect 120-150pF, maybe somewhat more, depending on strays from wiring (which can be considerable with four paralleled sections) and how optimistic the datasheets are.
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