How do you go about calculating Zout for a phono stage?

andyr · 04:29 AM

EDIT: actually, I should have said "calculating or measuring the Zout".

Can anybody tell me how I go about finding out what the output impedance of my JFET-based phono stage is? It has a BC547 as the output buffer, if that is relevant.

Thanks,

Andy

Mark Kelly · 28th September 2012, 04:46 AM

Measuring is easy: put a largish known resistor in series between the output of the stage and the output of a signal generator. Short the input of the stage, turn the signal generator up enough to get say 1 mA across your known resistor and measure the voltage to ground at the output (of the stage, not the generator). The output Z is the residual voltage at the stage output divided by the resistor current.

Calculating is easy if you post the schematic.

andyr · 28th September 2012, 04:54 AM

Thanks, Mark, I'll email you the schematic this evening.

Regards,

Andy

28th September 2012, 12:32 AM	#1
andyr diyAudio Member Join Date: Nov 2003 Location: Melbourne (Oz, not Florida!)	How do you go about calculating Zout for a phono stage? EDIT: actually, I should have said "calculating or measuring the Zout". Can anybody tell me how I go about finding out what the output impedance of my JFET-based phono stage is? It has a BC547 as the output buffer, if that is relevant. Thanks, Andy Last edited by andyr; 28th September 2012 at 04:29 AM.

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28th September 2012, 04:46 AM	#2
Mark Kelly diyAudio Member Join Date: Feb 2006 Location: Geelong	Measuring is easy: put a largish known resistor in series between the output of the stage and the output of a signal generator. Short the input of the stage, turn the signal generator up enough to get say 1 mA across your known resistor and measure the voltage to ground at the output (of the stage, not the generator). The output Z is the residual voltage at the stage output divided by the resistor current. Calculating is easy if you post the schematic.

28th September 2012, 04:54 AM	#3
andyr diyAudio Member Join Date: Nov 2003 Location: Melbourne (Oz, not Florida!)	Thanks, Mark, I'll email you the schematic this evening. Regards, Andy