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Old 12th June 2007, 08:14 PM   #151
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Quote:
Originally posted by steenoe


Manu dont despair, you are doing great.
Do you have a picture of the board with the resistor values you used on it? The layout seems correct, but it would be nice to see the values.
Another thing, did you try and measure the actual bias current to see if it is as its supposed to be? If not; then measure the voltage drop across the source resistor and divide the value you get with the source resistor value to get the bias current. I=V/R

Steen
Thx for your kind words. I don't despair realy but I don't want to be unjust to the JFET BOZ.
THe values are the same as in Nelsons posts. I only tried some different PSU volage values 20V 17V and 14V
With 20V and 10R Rs I had about 7mA through Rs. Voltage drop across 2K2 was 15V
With 17V ,15R Source res. -> 13,7 Volt. drop accr. drain Res. and about 6,3 mA through Rs
JFet are BL with about 9mA Idss

Manu
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Old 12th June 2007, 08:18 PM   #152
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Forgot the pic :
Attached Images
File Type: jpg jfet boz pcb.jpg (99.1 KB, 3228 views)
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Old 12th June 2007, 08:26 PM   #153
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Quote:
Originally posted by Manu


Thx for your kind words. I don't despair realy but I don't want to be unjust to the JFET BOZ.
THe values are the same as in Nelsons posts. I only tried some different PSU volage values 20V 17V and 14V
With 20V and 10R Rs I had about 7mA through Rs. Voltage drop across 2K2 was 15V
With 17V ,15R Source res. -> 13,7 Volt. drop accr. drain Res. and about 6,3 mA through Rs
JFet are BL with about 9mA Idss

Manu
in that case try to shoot 5mA as target current
leave at least 5-7 volts across jfet
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Old 12th June 2007, 08:37 PM   #154
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The board seems okay. What are the +/- desigantions at the output? Looks like you have them exchanged.

Steen
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Old 12th June 2007, 08:40 PM   #155
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Quote:
Originally posted by steenoe
The board seems okay. What are the +/- desigantions at the output? Looks like you have them exchanged.

Steen
Is the circuit not inverting?

manu
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Old 12th June 2007, 08:59 PM   #156
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Quote:
Originally posted by Manu


Is the circuit not inverting?

manu

nope ;
but hot end is always hot end ;
you can unhotttttt him only with xformer ;

mebbe hot isn't so important ,as gnd is
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Old 12th June 2007, 09:10 PM   #157
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Quote:
Originally posted by Zen Mod


in that case try to shoot 5mA as target current
leave at least 5-7 volts across jfet
Are you a magician, master?


With 5mA (22R Source Res), The distortions are almost gone (bnot entirely though).But Yipiii.
I will reduce 2K2 to get 5-7V accross Jfet (now its about 4V) as you said captain.
The sound approve a lot...
The live character of this pre is amazing. Even with studiorecording.
Enjoying (My beautiful bosnian girl enjoy too)
Manu
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Old 12th June 2007, 09:17 PM   #158
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It really helps if you have any kind of distortion analyzer
for setting this up. There is a specific bias voltage/current/
gain/load sweet spot, and the figures I gave are approximate
due to part variations.

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Old 12th June 2007, 09:23 PM   #159
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Quote:
Originally posted by Zen Mod



nope ;
but hot end is always hot end ;
you can unhotttttt him only with xformer ;

mebbe hot isn't so important ,as gnd is




And nobody trust me when I say I am stupid.

Reconnected hot to hot and : Oh Lord!!! This sound. Plenty, full, seductive, and cristal clear.

Danke Meister
Danke Steenoe.

It is realy great.

(But I have to crank the volume allthe way up
)
manu
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Old 12th June 2007, 09:27 PM   #160
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Quote:
Originally posted by Manu

.............. (My beautiful bosnian girl enjoy too)
Manu

send my hello to her
what's her name ?
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