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diyAudio Member

Join Date: Feb 2009
Quote:
 Originally Posted by CeeVee Thanks Nic, But...Rdegen trick comes at a price....slightly higher distortion, read this somewhere !, and according to Patrick ( EUVL ) deviating from 5R1 is to be avoided. I fail to understand this but then that will be because i don't know enough of the subject. My reasoning was in line with what you just laid out, the lower the Rdegen needed the better i thought. 5R1 being an average value. I'd love to get the facts on this.
I think the idea of the trick is to lower distortion at the cost of higher local feedback (degeneration).
I am quite sure Patrick picked 5R1 because this is a value that "in average" will yield most NP-matches.
Maybe lower is better, but remember that there is already 11R is series in the F5X.
I think having different Rdeg for each J74 is a DIY'er luxury which can only be recommended
Anyway - wrong thread.

 10th January 2013, 10:27 PM #322 diyAudio Member     Join Date: Dec 2006 Yep...wrong thread but nice discussion ...see you on the proper one
 10th January 2013, 10:30 PM #323 diyAudio Member     Join Date: Oct 2010 Location: Burlington, NC P3 accomplishes similar, correct. __________________ ...Shape the sound , Man!
diyAudio Member

Join Date: Jun 2004
Location: XH
System the principle of measuring voltage as shown below.Example measure the Vbe,

The BE two points of the voltage applied to the ADC input after 91K/12K resistor divider.
If R1/R2 and R3/R4 do not match. R1/R2=91K/12K R3/R4=91.09K/12K
When close sw1, Real Vbe is 0V. But because the resistor no match,The voltage difference between the AD1 and AD2 is

36* (12/(91+12) - 12/(91.09+12))=3.66mV

The system according to the measured, and then multiplied by the coefficient of the resistor divider, and it consider the Vbe voltage is:

3.66mV * (91+12)/12=31.4mV.

So if you measure the JFET Vgs-Id curve, system consider Vgs=0, But in fact the voltage of G/S is not zero.

This error voltage will change with the ground voltage (V) varies.
And when you measure N type ,the Ve is set to 2.5V,and measure the P type,the Ve will set to 36V. So At difference Ve,the error voltage is no same.

So I used some correction algorithm, possible error voltage Ve = 2.5 to 36V range to minimize.
The following diagram is shorted BE and shorted CE,and show Vbe / Vce voltage curve under different Ve.
Attached Images
 1.PNG (7.3 KB, 327 views) 20090604_52d3d53c250e4ab4d649KUHWZpYR9nz0.png (34.3 KB, 328 views)

diyAudio Member

Join Date: Feb 2010
Quote:
 Originally Posted by locky_z The 2sa970 component foot is right? Send the save data(.cuv) to me. When start the measurement, the system control 3 channel output only moment of voltage. When measure finish, 3 channel output to 0. If you want to measure 3 channel output voltage by DMM, you can select menu 'option->diagnoosis' and 'Device Test' page -> 'Voltage Test' box, Set the 3 channel output voltage and click the 'Output' button, Then you can get the static voltage.

diyAudio Member

Join Date: Feb 2010
I locky-z, thanks for the reply. This is the screen shot for the 2sa970: I alyways get very low hfe I do not not know to send the .cuv file.

Quote:
 Originally Posted by locky_z The 2sa970 component foot is right? Send the save data(.cuv) to me. When start the measurement, the system control 3 channel output only moment of voltage. When measure finish, 3 channel output to 0. If you want to measure 3 channel output voltage by DMM, you can select menu 'option->diagnoosis' and 'Device Test' page -> 'Voltage Test' box, Set the 3 channel output voltage and click the 'Output' button, Then you can get the static voltage.
Attached Images
 Capture01.PNG (52.3 KB, 536 views)

diyAudio Member

Join Date: Feb 2010
Quote:
 Originally Posted by jeepy I locky-z, thanks for the reply. This is the screen shot for the 2sa970: I alyways get very low hfe I do not not know to send the .cuv file.
The NPN (2sc2240) test seems to be ok!
Attached Images
 Capture02.PNG (64.6 KB, 61 views)

 11th January 2013, 12:41 PM #328 diyAudio Member   Join Date: Jun 2004 Location: XH 2SA970 you need to load the 'PNP Ic-Hfe' condition. PNP's voltage is negative. __________________ http://www.ebay.com/itm/111587792253
diyAudio Member

Join Date: Feb 2010
Quote:
 Originally Posted by locky_z 2SA970 you need to load the 'PNP Ic-Hfe' condition. PNP's voltage is negative.
It is what I did. I tried 3 different types of PNP transistors with always the same problem: hfe = 2 to 3. Again, The NPN test is OK as you can see on the picture! Could something be wrong with the board? Unfortunately I cannot aford to spend days to fix. Any suggestion will help, thanks

diyAudio Member

Join Date: Jun 2004
Location: XH
The PNP measure condition is:

But from your picture,I think your condition is NPN type.
Normaly in PNP's result data,The Vce is negative, Ve is +35~36V.
Attached Images
 jj.PNG (9.6 KB, 510 views)

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