update:new pics below : more to write up
Iphone/ipods/insertbrandhere they are decent enough players I even read that they (apple) had a decent onboard amp on newer generations ( of the wolfson variety which apparantly is rather good ) but for me it was still sounding flat and laclustre( although pretty noiseless considering its got phone radios and wifi and bluetooth in there and for that you cant complain to much about the pods these days ); my old technics amp was great at driving headphones ,warm smooth bass made tracks have a scale like a large soundstage in your ears – even with relatively cheap pair of $50 cans. (although now its a bit fluffy and hissy as its old and disused )
What I wanted was a big amp sound but in a tiny portable package to have at my desk or when I travel, and more importantly to have the power to drive big cans to tiny high quality shure 530’s type of headphones and not have my mp3 player struggle to power them at high volumes/bass boost moments ..enter Texas Instruments OPA2227PA op-amp.
Now theres many ways to skin a cat with this type of circuit . I choose my pcb based on professional quality and features. I prefered the option to fit the amp into a mint tin (tis all the rage these days lol) sized case and also to have a natural sounding bass with its own volume control which others havent included in their design ; using the bass feature on an ipod and most other mp3 players is not great in my experience (cowon/ iriver fairly excused as they have great bass EQ ). So I built the amp using cmoy bass circuit pcb from http://www.jseaber.com/cMoy/
I wont go on about its specs whys and what fors (pcb) – go to the site of its creator and see Johns explainations about the design decisions – all you really need to know is that its of a high quality build and very easy to put together.
I choose an alternative part which had diff pinouts, this pic shows the alternative potentiometer on Johns list.
An email to John came with a lightning quick reply and he sent me this wiring diagram for the panasonic branded volume control. Which was very convenient as I could get stuck in and finish the main soldering tasks in no time.
probably the hardest part now .. the tin choice and fitting !…. :) .. tbu