The layout of the PCB is well-spaced, with the important components
as near to the 3 TDA7293 ICs as possible. Having a professional-done
PCB means that we can use double-sided PCB, thus allowing us to
use almost no jumpers yet have a short path for the signal. The
input signal have a very short path to the master TDA7293 IC.
Even though it looks spacious, the size of the board is only 16.5x7.3cm.
The design highlight of the layout is in the very careful layout
of the ground returns. Note in particular the very explicit "star"
ground you see in the lower half of the board.
The construction of the amp is very straightforward; it can take
less than 10 minutes to populate a board.
The PCB is available here.
We use individual diodes as bridges, having 2 bridges for each
channel. Any series of the MUR can be used, as long as the diode
reverse voltage is above the voltage of the transformer output.
We chooses MURs from onsemi
due to their fast recovery time, and low voltage dropout. However
you can use any other diode you like. Heatsinking the diodes is
optional, as they do not get warm at all.
The PCB of the power supply allows us to use any size of caps after
the bridges, up to 4 20000uF as long as they fit well on PCB. We
can add another 2 smaller caps when needed.
This power supply board can also be use for other purpose if needed,
e.g. other DIY amps or other preamps that I might build in the furture.
I etched the PCB at home using photosensitive boards. The size
of the board is 15x10cm.
As I am still constructing my DI-Pre,
another friend of ours, CGH, have completed the amp before I could
even start with mine, the pictures of his completed amp can be seen
here. After hearing
it, I like it a lot that I will be building mine soon (as soon as
I find time)
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