"Phil Allison" wrote in message
...
Arfa Daily wrote:


Now this amp has a PIC onboard that (as well as controlling the
footswitch
functions, also) senses the inserted jack in the input socket.
But, in addition, it also disables the Bias control circuitry, so as
well
as muting the signal to the Power Amp, it also puts -100v bias onto the
output valves, thus cutting them off completely, unless a plug is in
the
input socket.

But what I didn't know was that the PIC also gets a signal from the
Speaker jack sockets, and will again not take off the -100v bias unless
THIS also has a plug in it.


Whilst it's all very clever sticking a micro in there, realistically,
what
is the point ?


** None so blind as those who will not see.


You said it, Philip ...




When has a shorted input, as is the case with most amps with
a switched input socket, ever caused any kind of problem ?

** It does not mute nor put the amp in standby.


I never said it did put it in standby, did I ? And whilst it doesn't 'mute'
the amp, it keeps it quiet enough for all practical stage-use purposes. And
a standby switch mutes it totally and absolutely.


And if you really want
to shut the output stage off along with the rest of the amp, what was
wrong
with a standby switch ?

** Requires an intelligent human operator.


Oh puleese ... It requires any guitar-playing grunt who can flick a toggle
switch. Cite me one single case you've ever come across in your long and
undistinguished career, where an owner has been too thick to cope with the
concept or operation of a standby switch.


When I see some of this stuff, I can't help but
think that it is design for the sake of the designer's ego.

** Lucky your mad ideas are not anybody's concern.

Lucky I'm not just mad, like you, whose ideas really are of no concern to
any sane person ...



What the uP does in this examples is useful, clever and makes great
selling points too - the number ONE thing a guitar amp has to do is sell
well in an extremely oversupplied market.

The number one thing it has to do is have a well known-name like Fender or
Marshall or Vox, and above all, have a reasonable price tag. Baffling
features - and these are if you think a standby switch is too complicated
for the average user - serve only to attract these amplifiers to musos who
have more money than sense, read all the 'right' reviews, and think
themselves a lot better than they actually are ...



The uP in the Blackstar extends output valve life, biases them precisely
and protects them in case of open circuit operation.

The only other amps I know with even this last features are some Rivera
models - where the output valves cathode connection to ground is open
until a speaker plug is fitted.

My only worry is obtaining replacement uPs in a few years time.


... Phil



Good luck with that.

Arfa