I take the basic design from Tangent. it's basically a PIMETA with OPA627 and two 634 buffers per channel.
Power is two 9V batteries in series (18V)
almost finished
amp&buffer 'section'
Reversed view - i'm not very good soldering - Thanks to tyre's photos i used wires to connect a lot of pins.
Into the cards box (I like this box. Look at the picture, they must be the girl's parents and look at the way he look at she.
)
Front view
Testing with Richter
Firsts impressions:
If I noticed an improvement coming from my previous cmoy (OPA134) when compared to the standard headphone jack of the Marantz Amp, now the improvement is more noticeable. Bass are extended and controled, mids are liquid and warm and treble is cristaline. But the most important improvement comes from the separation of instruments. A lot of air between instruments, a lot of space.
And the improvement it's very, very important with HD600s. The grado 225s are good headphones but now i know why HD6X0s are so praised. The bloated bass they exhibit with the standard headphone jack is lost now.
In near future I plan to bias the opamps in class A. But for now I'm going to enjoy with the music.