Fostex FE208EΣ rear loaded horns


Bluebell Audio "Loftin White" 2A3 SET valve amp
TubeCAD Headphone amplifier
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Bluebell Audio "WE91" 300B SE valve amp monoblocks

Garrard 401

Goldring Lenco GL75
Unipivot tonearm - the Stick
Passive preamp
C3g driven 2A3 SE valve amp
Gordon Rankin's Bugle - a super 45 SET amp
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C3g-Aikido Phono Amp
Experimenter's Chassis
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Experimenter's Chassis


Each time I think about building an amp I'm faced with the whole breadboard/valve socket/chassis conundrum. Cutting, drilling, filing aluminium plate, mountings etc. etc. So I thought building an Experimenter's Chassis might be a good idea - short term pain for long term gain. So I procured a sheet of 2mm ally and carefully marked it out. Then I started to drill holes. And more holes. And yet more holes. Then I had a break to let the drill cool down. And then I drilled some more holes. Enough for two each per channel of UX4, UX5, B4/5, octal and noval. Mounting holes for a choice of AE OPTs, speaker terminals and a couple of umbilicals completed the drilling.

With the protective film...

...and without

The plate was screwed to sides made from 120mm x 18mm softwood from a DIY shed.

Inside I mounted miles of tag strip fixed to valve socket fixings. A small plate on the front for phonos and volume pot finished the job. For the PSU I've been a little more pragmatic choosing to go open breadboard to facilitate playing with chokes and big caps. But eventually I think I might just build a Steve Bench-style valve series reg along the lines of the one I played with when breadboarding the C3g/Aikido phono stage to give me easily variable B+.

Back to the breadboard for the PSU, to link it to the audio stage I made a pair of umbilical cords. I wasn't convinced it was a great idea to go with umbilicals but without trying I wouldn't know. I wanted plenty of flexibility so each cord has six lengths of wire, which I first soldered to the male part of the connector. This is a reasonably delicate job and one I would have made a real mess of if I'd tackled it when I first started DIYing...

A little worried about the possibility of shorts considering flexing of the cord I added some shrink wrap which finished the job of nicely.

Finally I wrapped both umbilicals in some expandible black nylon braid. It's not perhaps as good a solution as I would hope for as there is little protection for the cables when plugging in and removing the socket. But it's a start and hopefully I'll find a sturdy metal socket that has a high voltage rating as well as current rating for HT and heater duties.

Here's a photo of the PSU breadboard, from when I was playing around with PSUs for the Bugle amp.

So now when I want to try something I should be able to knock an amp up quite quickly. Or that's my hope at least.

September 2008.



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C3g driven 2A3 single ended valve amp