Fostex FE208EΣ rear loaded horns

WAD PHONO II and PSU II

Bluebell Audio "Loftin White" 2A3 SET valve amp
TubeCAD Headphone amplifier
Fostex T90A supertweeters
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
Aikido Headphone Amp
C3g-Aikido Phono Amp
Experimenter's Chassis
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Experimenter's Chassis

Introduction

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