Post by videoguy on Oct 19, 2015 16:17:48 GMT
For those members that have the Silicon Chip Magazine Headphone Amplifier kit from either Jaycar Electronics or Altronics, Australia: I have come up with a simple but major improvement It was a very popular kit with improvements on the R.G. forum 5-6 years ago.
Originally a National Semiconductor LM4562 metal can opamp was specified. It is replaced with an LME 49860NA from Texas Instruments. This is the part no. for the 8 pin dip version, that is a direct plug in replacement. This is the exact same integrated circuit as the LM4562, with the exception of the operating voltage. The original was rated
+- 18vdc, the LME49860NA is rated +- 22vdc. The only other change needed is to raise the voltage in the bi polar power supply from +- 15vdc to +- 20vdc.
The original power transformer is rated a nominal+- 15vdc. In order to increase to 20 vdc, the power transformer should be changed to one having a secondary winding of
between 36 to 40 volts ac with a center tap & current capacity of 400milliamps. One user made the mods. & reported it as a blunderbuss improvement in dynamics & presentation
I had come late to the party & built my amp for 20 volt operation with the new opamp & was impressed with the audio quality.
A WORD OF WARNING; TI data sheet for the LME49860NA shows the 8 pin dip package is being replaced with the SOIC direct solder version. If you have any plans to perform this upgrade, order the opamp soon.
If you have any questions feel free to contact me.
Bill Wilson