PSRR and Crosstalk

dgardner · 18th June 2005, 06:22 PM

I have a couple of questions about the interelationship between PSRR and Crosstalk as is relates to small scale discrete class A design.

I've been working with a couple of different class-a headphone amp designs that have been popularized on the head-fi.org. I've started testing them with RightMark Audio Analyzer and the stereo crosstalk figures are not that great (-60 to -75dB range).

The topology is known to have poor PSRR because of the discrete topology. My bench power supply is pretty clean, but not ultra pristine.

Q: Is there a specific relationship between amps with poor PSRR and poor crosstalk figures?

Q: What mitigations are typical to improve crosstalk figures in discrete class-a designs?

Nelson Pass · 18th June 2005, 09:13 PM

This is a complicated subject. There is not a general direct
relation between PSRR and crosstalk, but they are often
found together as a result of poor design or workmanship.

Nothing works as well as mono amplifiers and quiet supplies,
but you can build quieter stereo amplifiers by isolating and/or
filtering the supply rails, and you can improve PSRR by
locating those elements which let rail noise into the gain path
and fixing them up. Often this involves the use of high quality
constant current sources.

mastertech · 20th June 2005, 12:08 PM

to improve crosstalk use separate supplies

dgardner · 20th June 2005, 12:24 PM

I'm building up two individual power supplies that will be very clean. If the measurements improve noticably, I'll post some results...

BobEllis · 20th June 2005, 01:09 PM

just a thought - have you measured the crosstalk of your RMAA system with just a loop through connection? You may be measuring your sound card's limits. It's been a while, but I don't think mine was better than what you measured.

18th June 2005, 06:22 PM	#1
dgardner diyAudio Member Join Date: Nov 2004 Location: Boulder Colorado	PSRR and Crosstalk I have a couple of questions about the interelationship between PSRR and Crosstalk as is relates to small scale discrete class A design. I've been working with a couple of different class-a headphone amp designs that have been popularized on the head-fi.org. I've started testing them with RightMark Audio Analyzer and the stereo crosstalk figures are not that great (-60 to -75dB range). The topology is known to have poor PSRR because of the discrete topology. My bench power supply is pretty clean, but not ultra pristine. Q: Is there a specific relationship between amps with poor PSRR and poor crosstalk figures? Q: What mitigations are typical to improve crosstalk figures in discrete class-a designs?

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18th June 2005, 09:13 PM	#2
Nelson Pass The one and only Join Date: Mar 2001	This is a complicated subject. There is not a general direct relation between PSRR and crosstalk, but they are often found together as a result of poor design or workmanship. Nothing works as well as mono amplifiers and quiet supplies, but you can build quieter stereo amplifiers by isolating and/or filtering the supply rails, and you can improve PSRR by locating those elements which let rail noise into the gain path and fixing them up. Often this involves the use of high quality constant current sources.

20th June 2005, 12:08 PM	#3
mastertech Banned Join Date: Mar 2005 Location: Australia	to improve crosstalk use separate supplies

20th June 2005, 12:24 PM	#4
dgardner diyAudio Member Join Date: Nov 2004 Location: Boulder Colorado	I'm building up two individual power supplies that will be very clean. If the measurements improve noticably, I'll post some results...

20th June 2005, 01:09 PM	#5
BobEllis diyAudio Member Join Date: Sep 2003 Location: Upstate NY	just a thought - have you measured the crosstalk of your RMAA system with just a loop through connection? You may be measuring your sound card's limits. It's been a while, but I don't think mine was better than what you measured.