Blimey, this had me stumped for a while.

Blackstar valve amp.
Unless you insert a plug into the input jack, the Power Amp section is on
mute, but I already knew that.
So you can't check the Power Amp section by injecting a signal into the FX
return or Power Amp In socket, thereby bypassing the pre-amp section, as I
normally do, unless you insert a dummy jack.

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.


So after repairing the faults, I follow my normal procedure of checking HT
and bias voltages with no output valves or speaker jacks in place, but I
remember to put a dummy jack in the input socket to unmute the amp.
But having no plug in any speaker socket means the amp will not come out of
the -100v bias position and I think for a long long time there is another
problem to fix.




Hope that makes sense.




Gareth.

Kinda makes sense. I really don't like all this automatic bull****, but it does make saense.

Like a pedal, if there is no inpput, turn off and save the battery.

with an amp, if nothing is plugged into the output, wwhy have output ?

I reember a car amp a long time ago, simple, transforer based, push pull with a driver transformer. It put out some, and they said to run the main power to oit off an always hot line in the car so you wouldn't overload the ignition switch. The other wire could come from hot in acc or run, ar even the new thing coming out on aftermarket radios, the pink wire that became hot when you tuen on the radio. It also ran some power antennas. The "ON" line for this amp simply supplied the bias circuit. With the bias off, it is pretty much off and that asa that. No relay, no pulling 20 amps though youi ignition switch, none of that. (it went in the trunk (under the boot))

"Gareth Magennis" wrote in message
...
Blimey, this had me stumped for a while.

Blackstar valve amp.
Unless you insert a plug into the input jack, the Power Amp section is on
mute, but I already knew that.
So you can't check the Power Amp section by injecting a signal into the FX
return or Power Amp In socket, thereby bypassing the pre-amp section, as I
normally do, unless you insert a dummy jack.

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.


So after repairing the faults, I follow my normal procedure of checking HT
and bias voltages with no output valves or speaker jacks in place, but I
remember to put a dummy jack in the input socket to unmute the amp.
But having no plug in any speaker socket means the amp will not come out
of the -100v bias position and I think for a long long time there is
another problem to fix.




Hope that makes sense.




Gareth.


Whilst it's all very clever sticking a micro in there, realistically, what
is the point ? When has a shorted input, as is the case with most amps with
a switched input socket, ever caused any kind of problem ? It serves to keep
the amp pretty silent, and is simple, and reliable. 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 ? 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.

I have a friend that is an ex commercial designer, and his answer is to put
a PIC in everything from a toilet seat to a kitchen blender. If ever I
happen to mention that I've knocked up some little service aid out of bits
in the junk box, his first comment is ALWAYS "If I was designing that, I'd
have done it with a PIC ... "

Yes, sometimes what he says is valid, but often, when I've achieved the
desired result with a couple of transistors and a few other bits, without
having to sit down and write and debug code to make it work, I really can't
see what the point of the needless complexity would be ...

Arfa

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.


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.


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.

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.

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 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

"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

Arfa Daily wrote:

"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.


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 ?

** You are making a false comparison by inventing straw man.


And whilst it doesn't 'mute'
the amp, it keeps it quiet enough for all practical stage-use purposes.

** Bull****.

FX loops are not muted, reverb is not muted and any noise/hum from the input st valve onwards is not stopped.


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 ...


** My god you are a ****ing tedious ****wit.


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,

** Right, you are an arsehole and a pommy pig too.


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 ..


** Sell well - you ****wit pommy knob.



..... Phil

On 15/03/2015 3:23 AM, Arfa Daily wrote:


"Gareth Magennis" wrote in message
...
Blimey, this had me stumped for a while.

Blackstar valve amp.
Unless you insert a plug into the input jack, the Power Amp section is
on mute, but I already knew that.
So you can't check the Power Amp section by injecting a signal into
the FX return or Power Amp In socket, thereby bypassing the pre-amp
section, as I normally do, unless you insert a dummy jack.

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.


So after repairing the faults, I follow my normal procedure of
checking HT and bias voltages with no output valves or speaker jacks
in place, but I remember to put a dummy jack in the input socket to
unmute the amp.
But having no plug in any speaker socket means the amp will not come
out of the -100v bias position and I think for a long long time there
is another problem to fix.




Hope that makes sense.




Gareth.


Whilst it's all very clever sticking a micro in there, realistically,
what is the point ? When has a shorted input, as is the case with most
amps with a switched input socket, ever caused any kind of problem ? It
serves to keep the amp pretty silent, and is simple, and reliable. 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 ? 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.

I have a friend that is an ex commercial designer, and his answer is to
put a PIC in everything from a toilet seat to a kitchen blender. If ever
I happen to mention that I've knocked up some little service aid out of
bits in the junk box, his first comment is ALWAYS "If I was designing
that, I'd have done it with a PIC ... "

Yes, sometimes what he says is valid, but often, when I've achieved the
desired result with a couple of transistors and a few other bits,
without having to sit down and write and debug code to make it work, I
really can't see what the point of the needless complexity would be ...

Arfa

**So true. I serviced a (brand and model deleted) power amp awhile back.
Simple design, but with high(er) bias switching. It, too, used a micro
for muting and switching the bias switching. Needlessly complicated.
Particularly in light of the fact that when the amp landing on my bench,
it was the micro that had crapped itself. It was one of those mask
programmable things, which I had to order from the manufacturer
(overseas - New Zealand). Silly buggers sent me the wrong micro, which
meant my client had wait even longer for his amp.

The amp has three switches. Power (just a big honkin' switch for the
mains), a muting toggle and a bias toggle. It could have been far
simpler and more reliable to just use simple stuff. If they had wanted
to get fancy, then a few gates is all they had to do.

For ****'s sake the damned thing was complementary symmetry to boot!

--
Trevor Wilson
www.rageaudio.com.au

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On 15/03/2015 3:43 PM, Trevor Wilson wrote:


For ****'s sake the damned thing was complementary symmetry to boot!


**Oops. "That would be QUASI-complementary symmetry..."


--
Trevor Wilson
www.rageaudio.com.au

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http://www.avast.com

** My god you are a ****ing tedious ****wit.


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,

** Right, you are an arsehole and a pommy pig too.



And you, as ever Philip, are a dopey **** who just can't stop that mealy gob
of his flapping. You are just a controversial **** who has to go against
anything that anyone says just for the sake of it. Now **** off back under
your stone you antipodean arsewipe ...

Arfa

On Sun, 15 Mar 2015 12:16:47 -0000, "Arfa Daily"
wrote:




** My god you are a ****ing tedious ****wit.


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,

** Right, you are an arsehole and a pommy pig too.



And you, as ever Philip, are a dopey **** who just can't stop that mealy gob
of his flapping. You are just a controversial **** who has to go against
anything that anyone says just for the sake of it. Now **** off back under
your stone you antipodean arsewipe ...

Arfa
Stop beating around the bush Arfa, tell us how you really feel.
Eric

wrote in message
...
On Sun, 15 Mar 2015 12:16:47 -0000, "Arfa Daily"
wrote:




** My god you are a ****ing tedious ****wit.


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,

** Right, you are an arsehole and a pommy pig too.



And you, as ever Philip, are a dopey **** who just can't stop that mealy
gob
of his flapping. You are just a controversial **** who has to go against
anything that anyone says just for the sake of it. Now **** off back under
your stone you antipodean arsewipe ...

Arfa
Stop beating around the bush Arfa, tell us how you really feel.
Eric


d:-)

Arfa