Ian Thompson-Bell wrote:
Don Pearce wrote:
On Sat, 03 Nov 2007 14:31:08 +0000, Ian Thompson-Bell
wrote:

As you may know from posts I made a few months back (before I moved
house) I have been doing some work on using 6AU6 tubes in triode mode
for preamps. The set up I have at the moment is pretty crude. I
stripped a chassis from an old battery valve radio, wired in the
components I needed then bolted it to a piece of wood along with the
mains transformer and PSU components. This is OK as far as it goes
but apart from looking tatty it is not very easy to make circuit
changes but, as I am making noise measurements, layout is crucial.

So.... I was wondering if anyone makes something I could use as the
basis of my experiments that would be easier to modify?

Any ideas?

The piece of wood is actually a pretty good idea, as it allows you to
manage your grounds properly, something it is much harder to do when
everything is bolted to a chassis.

Layout doesn't do much for noise, per se, but it will greatly affect
hum. Do all the usual things with extra big caps in the power supply
and battery powered heaters. But mainly be very assiduous in
star-point-grounding every signal component and lead around the valve
you are measuring.

You will probably try half a dozen layouts before you convince
yourself you are measuring what you actually want to measure, and not
some spurious effect.

To make component changes easier, cut a nearly chassis-sized hole
through the wood so you don't need to unbolt everything to make a
change.

d


Thanks for the input Don. I have used wood as a breadboard many times in
the past - it is pretty good for keeping everything together. Hum is not
a problem as I soon discovered a battery heater supply was these easiest
way to eliminate it. Component change is the real issue. The chassis is
basically U shaped so I might try removing one side to make it L shaped
which should ease access.

Cheers

ian

Just treated myself to a pair of tin snips. I removed one side of the
chassis, laid it on its side so the valve bases are facing me and
screwed it to the wood. Much better.

Cheers

ian