Building a Hypex UcD700-based power amp
As supplied the UcD700 module utilises a separate +/- 12V supply for the front end (to supply the op-amp, I believe). The data sheet describes a simple supply using 7812 & 7912 regulators. A 15V driver supply is also required, again a simple 7815 being suggested. Rather than keep things simple and, based upon the experiences with pre-amp power supplies, I decided to cobble together something slightly more sophisticated. Stealing ideas from many places but mainly the excellent pink fish media forum I ended up with:

- a simple C-L-C raw supply using some special capacitors and inductors from
Avondale Audio
- a VBE circuit along the lines of Teddy Pardo's many excellent postings on
pink fish, and
- a straightforward LM317/337 application circuit

The resulting circuit is shown here:

I also took the opportunity to have a go at building a PCB - my second ever attempt (my first, back in 1982, involved sticky-backed plastic, a scalpel and lots of swearing). This time I tried 'press and peel' which is available from Maplin. Suitably encouraging comments from Andrew Weekes' power supply website persuaded me that I ought to have another go. The result is shown below:

Incidentally, being slightly old-fashioned and set in my ways, all my board layouts (usually on veroboard) and circuit diagrams are drawn 'by hand' on an old Mac running Claris Draw. It's no CAD program but it's a step-up from graph-paper!

The finished article looks like this. I must admit, I'm quite pleased with it, even though I don't know if it works at this stage:

A point some will make is why I've implemented a circuit I haven't tested into its 'final' form without any testing, fiddling, tweaking, etc. This is a good question, especially as tweaking post-build will be difficult. All I can say is that when building something for a friend (a 'customer build', if you like) there tends to be less time for this sort of thing so it's a case of soaking up as many ideas as possible at the design stage and trying to come up something that will a) hopefully work, b) work reasonably well and c) be as reliable as possible. This last point is probably at least as important as b) because I won't necessarily be around if anything needs attention. So I concede that as a design it probably isn't as optimised as it could be, but hopefully, it won't be too shabby, either.
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