On 4/7/2012 6:17 AM, Stephen Roberts wrote: > 525 1/4" to new Sennheiser headphones. Do I need to do anything special? Nope. Audio is NOT impedance-matched. Most headphones work with most equipment. For more discussion of this, see the Appendix on audio that is part of my RFI tutorial. http://audiosystemsgroup.com/RFI-Ham.pdf 73, Jim K9YC