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Old 17th October 2006, 08:15 PM   #151
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Quote:
Originally posted by Ryssen

I think thatīs the case,already tried with 1,2v bias the trafo canīt keep up the voltage..Gonna try this bigger trafo I ordered.
But don't expect significant quality improvement.

To charge a capacitance of 1 Farad during 1 Second to 1 volt we need 1 Ampere (I love the Metric system!).

Suppose, your FET has 3000 pF input capacitance. Suppose, you have about 0.5 voltage swing s-g to fight against the capacitance (actually much less).
Minimal current is 2*(10^4)*2*3(10^-9)0.5=6*(10^-5) Amperes, i.e. 0.01 mA. If you have 10 Ma, it means you have 1000 times more, or you have already enough current for a swing 500V s-g.

It means, neither CD, nor MP3 can give you such a quality signal so you can measure differences on the high end of your band.
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Old 17th October 2006, 08:36 PM   #152
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Oops...
Sorry for the mistake, I've lost "6", anyway you have almost nothing to gain by a bigger current. It is better to play with the current for less triode distortions and forget about partially capacitive input of your FET follower.

Use your new tranny for your new project.
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Old 17th October 2006, 09:13 PM   #153
Ryssen is offline Ryssen  Sweden
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Well,Iīve heard some say the 6C45 "needs" at least 30mA to sound itīs best,so who knows.
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Old 17th October 2006, 10:39 PM   #154
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Try your bigger transformer.
Did you say you were using the transformer back to back with your main power transformer. If so then this setup has particularly poor regulation.

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Old 17th October 2006, 11:00 PM   #155
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Quote:
Originally posted by Ryssen
Well,Iīve heard some say the 6C45 "needs" at least 30mA to sound itīs best,so who knows.
They were right. Better use another tube.


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Old 18th October 2006, 02:03 PM   #156
Ryssen is offline Ryssen  Sweden
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Quote:
hey were right. Better use another tube.
No,no not another tube I will fix this..
Sounded pretty good at 15mA to.
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Old 19th October 2006, 12:26 AM   #157
MIKET is offline MIKET  United States
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Default CCS with 6C45

I think you need to raise b+ to about 220V and lower the resistance on the CCS (10E in Series w/470E) and you should be on your way. As far as an LED goes, I can't help you much there. I think you got it right that you are too low a voltage on the CCS that feeds the tube, THe 6C45 sounds fine to me at 18-20mA, but it will handle more current if that is your wish.
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Old 19th October 2006, 03:27 PM   #158
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I'd use 175V/30 MA with 250V B+
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Old 19th October 2006, 03:41 PM   #159
Ryssen is offline Ryssen  Sweden
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The new bigger one,lets hope it can keep up the power..
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Old 28th October 2006, 08:50 AM   #160
Tyimo is offline Tyimo  Hungary
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Default BOZ PSU for tubepreamp

Hi!

Is it possible to modificate the BOZ PSU (Mads version) to 120-150V??
I know I need to change the zeners, but what about the rest of the parts??
I would like to use it for my tube pream.

Greets:

Tyimo
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