HiFi Subjectivist ¦ Audio Forum ¦ NVA User Group

Since Christmas, the breadboard in the previous picture has been dismantled, the complexity has been ditched, and we are back to basic engineering principles. The 'proper' build has been pored over, planned out and we are now at the stage, where a 500 x 250 x 70mm chassis frame has been constructed from half inch plywood, then veneered in walnut and finished with 4 coats of satin acrylic varnish.



All the controls, switches, inputs, mains connections are mounted on the frame. L/R volume controls are ex 1957 scrap, Ferguson radiogram and the chicken head knob between selects 4 different sources. Transformers, chokes valve sockets and electronics will be mounted on an aluminium top plate. That has yet to be drilled, punched etc.

Getting there:

Aluminium top plate has been drilled, punched holesawed, filed, then sprayed with an "Antique White" acrylic finish after having been etch primed.
The plate holding the switchgear and mains indicator lamp, has also had the antique white treatment.
The antique white goes nicely with the volume controls, selector switch and the walnut surround.

Won't be long before I get the OTL up and running; maybe by the end of the week.

Just in and did a sex wee when i clapped eyes on this sexy chassis,
very nice Steve, can't believe everything on the breadboard fits in,
can't wait to see it finished.

Looking good
Is the aluminium just a b&q type plate or have you gone thicker as their range is limited

Latteman wrote: ↑Mon Mar 18, 2019 8:55 pm Looking good
Is the aluminium just a b&q type plate or have you gone thicker as their range is limited

It's checkerplate from B&Q, smooth side up. 2mm thick (I think).

@ Wiicrackpot. The big toroid will be on top of the deck, covered by cream sprayed, seven inch round cakepan, so the two small transformers and the two power supply chokes and four 2200uF caps will fit nicely on the underside of the plate.

Can you decorate the top like a cake

That'd be a bit too kitsch; even for me

Loiking interesting steve. Fine job

Just so you know. Spelling mistakes are no longer because i have to use my left hand. It is now my domiant hand. Its because im lazy

We have heaters on the power tubes.


I'm using a smaller 25V transformer for the 13E1 heaters than I did on the breadboard. Heaters are running at 25.7V rather than the 27.2V of the breadboard version. This is far better; only 0.3V low instead of 1.2V too high. Should give the valves an easier time.

That's all for today. The epoxy thermal bonding paste, holding the Constant current sink chips to the underside of the top plate, needs to cure thoroughly before I do anything else with the amp. Providing nothing blows up, the OTL should, I would think, be running by Sunday at the latest.