Hi,
I've been doing up a '62 Kriesler Stereophonic for use as a shelf/computer system.
The objective is to isolate the amplifier from digital sources by connecting with
digital optical cable,
which is achieved with an inbuilt digital to analogue converter.

I am quite proud, and it sounds great


These are star lugs (not washers), but they have two wire holes each,
and one continuous wire is fed through both holes in each lug.

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I did mean real heat shrink, and there are also some mica spacers in there:
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If you look close you'll see the wire though holes have grommets,
and that is vintage brass there, measured to mate existing chassis holes

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The holes are big enough to straighten it up, and tighten (just finger tight for now).

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1962 Kriesler Stereophonic:
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Bench test:
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I'm already planning a replacement PSU.
I should be able to do it smaller, and fit a flip-flop and relay to turn the amp on and off
with a soft button if the 6 Volt supply is always running the flip-flop for standby.
Also, I'd like to see how the new green neons look (at least take a look since I already have them).


An off the shelf DAC stripped of it's coaxial input socket and input select switch.
Input select switch is permanently jumped on the DAC PCB for optical input only.
The DAC is based on a popular Cirrus chip which is great for experimentation.
The chip has outputs and functions not employed by this generic DAC unit.

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Mounted DAC and PSU (front).

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Mounted DAC and PSU (rear).

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Cheers, Art.

Nice project. What are you doing, or planning, about a cabinet?

Maven

Hopefully there's a big enough aluminium extrusion
for a U channel around the thing.

I really like electronics more than the engineering with cases, etc.
That's why I was happy to trash the radio components,
and reduce it down to only the tone and volume control.
Not much has to feed through to outside a cabinet.

I did an S/PDIF compatible laser connection a while back,
so applying it to this was easy.
Now only the power cable has to be plugged in for the
valve amp to be connected to some digital audio equipment.

The mute switch is placing a cup of coffee on the white
square which blocks the laser beam carrying the signal.
Nothing new here, you take an off the shelf optical to coaxial converter,
and use the chip to buffer for a laser pointer guts.

I also removed the radio properly, making room for a microcontroller playpen.

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I'm aiming for digital potentiomenters from Maxim (for pushbutton volume), relay controlled power to the valve amp,
and a signal lock indicator.
The cirrus DAC chip graciously provides a logical "locked" output.
That would be the magic eye input, but it's only an on/off state.

If you chose to use an infra-red IRDA connection rather than laser, you could give yourself much more flexibility for remote control interface and signal interruption (and more options for coffee cup placement!). You'd still have ample audio bandwidth for the capabilities of the amplifier. S/PDIF is fixed network, IRDA is untethered but line-of-sight.

Maven

That is an idea! It was really just some fooling around back when I modified the S.PDIF converter.

This has 6M5 pair, so it can't be my every day amp,
until I either substitute them, or find some spares.
I think a project that is going to require a lot of power ups,
I should even find a bad pair to start with.

What is wrong with the 6M5 pair?

If you wish to substitute them, you can use 6BQ5/EL84's with some changes to the wiring. 6BQ5/EL84's are still in current production too.

See post below.

http://vintage-radio.com.au/default.asp?f=3&th=446.

There's nothing wrong with them, they're awesome, but I would like at least one spare set so as not to be left cold, considering the first couple of months use of the thing could be considered abusive.

So we'll see if this PWM neon driver makes any interference!

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https://www.youtube.com/watch?v=1F8kiKHg0xo.

It's hard to see in the video, but there are two PWM channels.

It would be possible to emulate magic eye in a non frosted glass neon.
It can be controlled which side lights, and how far up the electrode.

My first custom PCB.. which is two channel neon driver,
and software relay power switch:

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and test demo:
https://www.youtube.com/watch?v=UfkuBugvrAk.

Nice work. I did one of those custom pcb's back in systems tech while at secondary school! Think it involved tracing out the circuit and then dipping in some chemical solution?

Riston was the trade name for the developer used when making negatives which were then in turn used to 'print' a circuit board that was coated with the red resist film and then once exposure of the board was complete it would be dunked in developer to remove the excess resist, then dunked in ferric chloride for a few minutes to burn away the unwanted copper, hopefully leaving the tracks in place to then be drilled and soldered to.

They were the days - when making something was a pleasure.

Sorry I don't know when you guys posted, but I missed it.

Well surprise! I did it with copper board and ferric chloride!
I say it was my fist PCB, but technically my second,
as my first was just a tagstrip, and I didn't have to think about it at all.

I had an old Dick Smith PCB starter kit stashed for a number of years,
and unfortunately this will be my last that is done the old fashioned way.

I have since tried the newer chemical with resist pen, and it was a dismal failure.
I'll have to go straight to modern transfer now.
I'm happy to do most stuff on protoboard though.

Resist pens and stick on dots and tracks are a slow but equally sure way of going about it. You have to make sure the ink from the pen is applied so the copper cannot be seen through it or the ferric chloride will go through. Even if it was to just thin out the track slightly it could cause problems if the current flow is too high for it to handle.

Well the problem is that was my only bottle of ferric chloride,
and I don't know if you can buy it anymore.

When I used whatever modern substitute they sold me at Jaycar,
it seemed to eat through the resist pen as well.. maybe it has it's own pen with different ink.

The new stuff they sold me is a white powder.