On Mon, 26 Feb 2007 23:04:51 +1100, "Phil Allison"
wrote:


"Don Pearce"

I have this little battery powered guitar practice amp, made by
Pignose. It sounds amazing - a bit like a Marshall 100 valve amp in
fact, and I could never work out why. These things are used by plenty
of big names on-stage, as well as plenty more who won't own up to it.

Anyway, today I had to take the cover off to fix something and I found
the reason for the meaty sound. It is a mini solid state valve amp

http://81.174.169.10/odds/pignose.jpg

Who'd a thought it?



** Dunno just what this Don Dude's angle is here - but that amp module
uses modern Silicon transistors.

So, it must be a fairly recent of " Pignose Technology" ( I use that term
very loosely) .

The earlier, almost famous and better sounding examples used Germanium
devices.

AC127 /128 IIRC.


What I mean is that although the amp is solid state, it uses a
topology more normally associated with valve amps. As such it has many
of a valve amp's characteristics - particularly the curved transfer
function, soft limiting and core saturation. Those are the things that
are heavily exploited in guitar amps to give thickness and weight to
the sound.

I'd never had the cover off this before and I was surprised not to
find a conventional tranny amp (even an IC amp) with some diodes
across the input to give it a bent transfer curve. This is a much more
expensive and better way to achieve the desired effect.

Of course I recognise that this was a conventional way to implement a
"Hi Fi" SS amp back in the sixties - indeed I built a few myself. But
when PNP/NPN matched pairs were a serious proposition and the op-amp
circuit was better understood and accepted, this method died a rapid
and largely unmourned death.



Pearce Consulting


** Consult your Doctor before swallowing what this man says ......





...... Phil



Whatever.

d

--
Pearce Consulting
http://www.pearce.uk.com