EMRFD Message Archive 3892

Message	Date	From	Subject
3892	2009-12-22 08:38:19	ha5rxz	Rail Splitters & Headphone Amplifiers
This is AF rather than RF engineering but I'm hoping that someone can supply an answer. I have built a headphone amplifier to boost the output of my YL's MP3 player. Each channel is an AD8512 dual op-amp chip with one amplifier doing the work and one spare amplifier is working as a rail splitter. The supply is a single 9v battery. 1) Should the ground connection on the input be connected to 0v or the nominal 4.5v of the rail splitter? 2) Should the ground connection on the headphones be connected to 0v or the nominal 4.5v of the rail splitter? My gut feeling tells me that the 4.5v rail splitter connection is the right choice but I have seen so many designs where op-amps are used on a single supply and 0v is the ground that I am not sure. HA5RXZ
3902	2009-12-22 11:56:52	John Levreault	Re: Rail Splitters & Headphone Amplifiers
ha5rxz wrote: > This is AF rather than RF engineering but I'm hoping that someone can supply an answer. > > I have built a headphone amplifier to boost the output of my YL's MP3 player. Each channel is an AD8512 dual op-amp chip with one amplifier doing the work and one spare amplifier is working as a rail splitter. The supply is a single 9v battery. > > 1) Should the ground connection on the input be connected to 0v or the nominal 4.5v of the rail splitter? > Signal ground should be connected to the nominal 4.5V of the rail splitter. > 2) Should the ground connection on the headphones be connected to 0v or the nominal 4.5v of the rail splitter? > Headphone ground should also connect to the nominal 4.5V of the rail splitter. The output of the rail splitter is now your signal and power ground, effectively turning the 9V battery into a +/-4.5V bipolar supply. The "nominal 4.5V of the rail splitter" you refer to is now "ground". You might also want to check out some of the headphone amp schematics at www.amb.org for guidance on this "rail splitter" technique. de John, NB1I
3908	2009-12-23 09:29:26	ha5rxz	Re: Rail Splitters & Headphone Amplifiers
Thank you John, you have confirmed my suspicions. Now to wrap it up in time for Santa to deliver it
3909	2009-12-23 09:45:11	John Levreault	Re: Rail Splitters & Headphone Amplifiers
Good luck! The rail splitter is very effective and removes the 2 large coupling caps that would normally be needed between the amp chip and the headphone outputs. Happy Holidays! Hope Santa's good to you, too! de John NB1I ha5rxz wrote: > Thank you John, you have confirmed my suspicions. > > Now to wrap it up in time for Santa to deliver it