Bottlehead Kits > S.E.X. Kit
S.E.X. on glass
Bourney:
I've been wanting to try my hand at printed circuit board design for some time. Having populated boards for a variety of audio and non audio projects I really appreciate the work that the designers put into optimising the layout and dimensions. Time to have a go myself.
After watching many YouTube reviews of free PCB design software and searching various forums I opted for KiCad, but there were a couple of others that would probably have been equally as suitable.
I decided to use the Single Ended Experimenter kit as my guinea pig, because:
(1) It's the only current Bottlehead headphone amp I don't own. I built one as a gift for my nephew a couple of years ago and always thought I'd like one for myself.
(2) It has more complexity than Crack but much less than Mainline or Crackatwoa, so I'm hoping it will be a good middle ground for a first attempt.
(3) It says Experimenter on the tin, so OK let's experiment.
S.E.X. is proving to be a good choice so far. There's enough in it to get me learning KiCad and provide a balance between "OK, I get it, this is going well" and "WTF, why isn't this working".
I will be using 2 boards for this project. 1 for the amp and 1 for the power supply. Both will be manufactured on 4oz copper with a 3mm trace width, except for the integrated C4S circuit which has 2mm traces. By my calculation this produces a copper cross sectional area equivalent to 21 gauge wire and should be a good proxy for the wire supplied with the kit, but this is an experiment for me and only time will tell.
I ordered the board for the amp first as I wanted to see how it would turn out. Below are some photos of the board before and after population. I'm happy with the outcome so far and have ordered the power supply board. It should arrive in a week or two.
Any guesses as to how this thing is going to sound?
(a) Same as the original, copper is copper.
(b) Worse than the original, old school is the best school.
(c) Sound? What sound? I clearly have no idea what I'm doing and a puff of the magic smoke is about to take place.
Paul Birkeland:
If your first board revision works properly and isn't noisy, that's a win regardless of how it sounds!
ssssly:
You beat me to it. The boards I designed for my SEX rebuild are in the mail right now as well.
I designed mine with the amp and the power supply on one board and the DC heaters on another.
How it sounds will largely depend on how well you maintained proper power, signal, similars, trace to trace and trace crossover separation. And how well you managed your trace lengths.
If you are new to PCBs you might want to try EasyEDA. If you don't need the circuit simulations its quicker and easier to use than KiCAD. I use Fusion 360 Electronics(Eagle) myself.
Pay attention to the C4S section of that board. Given the standard package size for the 2N, using greater than 50mil traces could be problematic. Both bridging and heat wise. And you don't need anywhere near that. Particularly in 4oz.
And you may run into trace resistance issues with 4oz traces that thick in the signal part of the circuit. Static, buzzing. Just have to test it and see.
If it isn't already and you end up ordering future revisions, you might also want to ensure your ground plane trace is wider than the rest of the circuit. And preferably outside the rest of the circuit. If it isn't it can be noisy. You also probably don't want it running near the -bias trace.
Hope all the magic smoke stays where it belongs and it sounds good.
Bourney:
Thank you very much for the tips. If the first version doesn't work out I'll be revisiting your advice for sure.
I'm looking forward to seeing a post on your build when the mail arrives.
ssssly:
Mee too.
While I'm proficient at PCB design, im proficient at logic circuits and vhf/uhf signals design. Not linear power supplies. Or audio circuits. Although I suppose knowing how to make a good antenna comes in handy when you want to avoid them.
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