On Thu, 9 Apr 2009 15:05:26 +0100, "Keith G"
wrote:


"Don Pearce" wrote in message
news:4a00f601.258178859@localhost...
On Thu, 9 Apr 2009 14:04:07 +0100, "Keith G"
wrote:

There's another issue, as of this morning - looks like I've got a
microphonic *valve socket* on an amp I have just re-activated and it's got
me wondering about cobbling together one of these 'Tripath' amps pro
temps....?? Just curious - David Holgate (past UKRA poster) was very
enthusiastic about them offlist a while back!!

Don't know the tripath, but when it comes to microphonic, it is always
the valve at fault.


Noop. Simple checking with 3 different valves (out of 4 available)
demonstrates the problem to remain with the socket always. I suspect the
soldering or it just needs proper, tricky cleaning - the problem is that its
PCB mounted, so not trivial to just swap it out and move on!! The nuisance
is that it pops and spits quite hard when its warming up and that ain't good
on a Lowther! (Voice coils wired inside and out and one will fall off with
that sort of behaviour, apparently!)

Ah that is a different problem - a poor pin connection rather than
microphonics. As the valve moves the connection makes and breaks. It
could be a dodgy solder joint or - quite likely when you mount
something as heavy as a valve on a PCB - a fractured track close to
the socket. You will need a jeweller's glass to see that.


Anti-microphonic sockets just provide some
suspension to keep the valve steady. Unfortunately a common error is
to carefully fit a nice anti-microphonic socket, then completely wreck
it by stiff, short wiring anchoring the thing firmly to the chassis.


Sure. Apart from the physical coupling, hardwiring anywhere/anything too
tight in a valve amp which is going to get quite hot is not a good idea!



Also, I've read your comments on suspension amd springiness again, but
still
don't know exactly what it is that is directly affected (or improved,
presumably) by 'high flux density'...??


Flux density? More is better.


Yep. That much is obvious - if nothing else, the figure goes up with the
price!! :-)


The force exerted by the wire is
proportional to it (and the current, and the number of turns in the
coil).


OK, I'm getting the idea - my initial thoughts were probably not to far out
then: I suspected it was like shortening a dog's lead - the higher the flux,
the shorter the lead. Which, I guess, is what give Lowthers their 'speed'
and supreme clarity - or, to put it another way, their entire *lack* of
'flubberiness'!


Unfortunately no - the forces and movements just don't work that way.

d