Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

--
*I never drink anything stronger than gin before breakfast *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Dave Plowman (News) wrote:

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Can other people hear it?

-- Richard

In article ,
Richard Tobin wrote:
In article ,
Dave Plowman (News) wrote:

Approach the speaker and the buzz drops in level and get close enough
and it goes. So you can play it with a hand rather like a Theramin. ;-)

Can other people hear it?

Heh heh. Yes. It's hardly subtle.

--
*Letting a cat out of the bag is easier than putting it back in *

Dave Plowman London SW
To e-mail, change noise into sound.

Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Have you tried turning off your phone, hearing aid, cardiac pacemaker,
(in that order)


--
Graham.

%Profound_observation%

On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Dave, try turning off all the lights and see if it improves.
I once had a job when the lights were modulating some of the
semiconductors particularly glass envelope diodes and putting 100Hz side
bands on the signals passing through (100Hz as this is the rate old
style mains lamps turn on and off when driven with 50Hz).

On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Unlikely but...

I once had to repair a small mixer - a simple noisy pot replacement was
needed - but I noticed a distinct buzz from the headphones. Taking
scope probe in hand I set about trying to find the fault, but it
disappeared whenever I tried to hook a probe on.

Long story short - it was a very old mixer using Germanium transistors,
at least one of which had some paint missing. Every time I bent over it
to hook a probe on I put the now light-sensitive transistor in shadow
from the fluorescent lights. Under normal use, with the covers in
place, this couldn't happen.

Cheers
--
Clive

In article ,
Bob Minchin wrote:
On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a
direct substitute, but digital, so allows a choice of crossover
curves, delays to each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough
and it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the
analogue one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when
you get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour).
With signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Dave, try turning off all the lights and see if it improves.
I once had a job when the lights were modulating some of the
semiconductors particularly glass envelope diodes and putting 100Hz side
bands on the signals passing through (100Hz as this is the rate old
style mains lamps turn on and off when driven with 50Hz).

Both amp and crossover are fully enclosed in ally cases. Putting a hand
near then from any direction gets rid of the buzz. I'm thinking to do with
body capacitance. Somehow.

--
*Geeks shall inherit the earth *

Dave Plowman London SW
To e-mail, change noise into sound.

In message , "Dave Plowman (News)"
writes
Wanting to experiment further, got a Behringer DCX2496 which is a
direct substitute, but digital, so allows a choice of crossover curves,
delays to each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough
and it goes. So you can play it with a hand rather like a Theramin. ;-)

I'm way out of date, so unlikely to offer anything worthwhile, but

1. are you feeding this speaker from a balanced or unbalanced source?
2. Does the hum stop if you disconnect the source?
3. Where, if anywhere are mains and xLR grounds connected together?

I'm a transformer man, so servo balancing sounds like a black art or
hole to me.
--
Bill

On 13/04/2019 14:53, Dave Plowman (News) wrote:
snip

Both amp and crossover are fully enclosed in ally cases. Putting a hand
near then from any direction gets rid of the buzz. I'm thinking to do with
body capacitance. Somehow.

Are these cases grounded?

Cheers
--
Clive

In article , Dave Plowman (News)
scribeth thus
In article ,
Bob Minchin wrote:
On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a
direct substitute, but digital, so allows a choice of crossover
curves, delays to each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough
and it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the
analogue one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when
you get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour).
With signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Dave, try turning off all the lights and see if it improves.
I once had a job when the lights were modulating some of the
semiconductors particularly glass envelope diodes and putting 100Hz side
bands on the signals passing through (100Hz as this is the rate old
style mains lamps turn on and off when driven with 50Hz).



Both amp and crossover are fully enclosed in ally cases. Putting a hand
near then from any direction gets rid of the buzz. I'm thinking to do with
body capacitance. Somehow.


Nah! Water don't flow uphill;!..

What are the pin connections on the 7 way XLR this unit has?..


--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

In article , Clive Arthur
scribeth thus
On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Unlikely but...

I once had to repair a small mixer - a simple noisy pot replacement was
needed - but I noticed a distinct buzz from the headphones. Taking
scope probe in hand I set about trying to find the fault, but it
disappeared whenever I tried to hook a probe on.

Long story short - it was a very old mixer using Germanium transistors,
at least one of which had some paint missing. Every time I bent over it
to hook a probe on I put the now light-sensitive transistor in shadow
from the fluorescent lights. Under normal use, with the covers in
place, this couldn't happen.

Cheers

Bin there seem that even in more recent Varactor controlled and
modulated VHF transmitters...

--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

In article ,
tony sayer wrote:
Both amp and crossover are fully enclosed in ally cases. Putting a hand
near then from any direction gets rid of the buzz. I'm thinking to do with
body capacitance. Somehow.


Nah! Water don't flow uphill;!..

What are the pin connections on the 7 way XLR this unit has?..

Adjacent pins for each pair. Central pin has all the screens connected to
it.

It worked just fine with the analogue unit.

The analogue X/O has an analogue PS. The digital one an SMPS. Clutching at
straws there. ;-)

--
*Support bacteria - they're the only culture some people have *

Dave Plowman London SW
To e-mail, change noise into sound.

Sounds like one of the amps may be a little unstable or on the other hand
its a psu issue of some kind where the hum is being picked up from somewhere
else that generates the frequency.
I think I'd try the old one of attaching a length of wire to bits of the
circuit like a speaker terminal, or the earth or another obvious place if
its affected by proximity, sounds more like a parasitic oscillation of some
sort.
Brian

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"Dave Plowman (News)" wrote in message
...
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

--
*I never drink anything stronger than gin before breakfast *

Dave Plowman London SW
To e-mail, change noise into sound.

When the unit is humming does the current it takes increase?

Brian

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"Dave Plowman (News)" wrote in message
...
In article ,
Richard Tobin wrote:
In article ,
Dave Plowman (News) wrote:

Approach the speaker and the buzz drops in level and get close enough
and it goes. So you can play it with a hand rather like a Theramin. ;-)

Can other people hear it?

Heh heh. Yes. It's hardly subtle.

--
*Letting a cat out of the bag is easier than putting it back in *

Dave Plowman London SW
To e-mail, change noise into sound.

Normally one can tell its the phone. Its a very obvious sound.
Also some electrolytic capacitors need a normal capacitor across them to
act correctly I used to find if driving sensitive electronics.
I had an old Sinclair like power amp that was a wonderful radar pulse
receiver and needed this mod to fix it but it was not hand sensitive it was
just wide open from dc to light kind of thing.
It might be interesting to drive it into power resistive loads and see if
you can measure the hum on any or all of the outputs. You could do that now
but its very fiddly. It might at least localise it, but if it is drawing
extra current when it hums I still think of parasitic oscillations issues.
You can easily blow up tweeters this way if you get a feedback loop going!
Brian

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"Graham." wrote in message
...
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Have you tried turning off your phone, hearing aid, cardiac pacemaker,
(in that order)


--
Graham.

%Profound_observation%

There is an old rule in DIY electronics. Your wonderful device works fine
when its a spiders web of bits joined by wire on a workbench, but as soon as
you put it into a case things start to not work quite right.

At the old TV company I worked at they designed a little rf transformer
wound on a bit of ferrite bead. It did what it was supposed to on paper and
on the breadboard version of the circuit, However when fitted on the pcb and
the case put over it, a pattern came on the screen. Eventually I happened to
put my finger on the transformer when it was open while testing it and up
came the patterning. It soon transpired that a stage was very slightly
unstable and the capacitance of the case or of a finger moved the frequency
to a resonant one and off it went.
Mind you I have a bass bin here which picked up Radio China International
till .1 uf capacitors were fitted to all the psu lines inside the cabinet.
Its totally unscreened inside and hence all sorts of crap gets in, still
some problems from switch clicks.
Brian

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"Dave Plowman (News)" wrote in message
...
In article ,
Bob Minchin wrote:
On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a
direct substitute, but digital, so allows a choice of crossover
curves, delays to each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough
and it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the
analogue one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when
you get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour).
With signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Dave, try turning off all the lights and see if it improves.
I once had a job when the lights were modulating some of the
semiconductors particularly glass envelope diodes and putting 100Hz side
bands on the signals passing through (100Hz as this is the rate old
style mains lamps turn on and off when driven with 50Hz).

Both amp and crossover are fully enclosed in ally cases. Putting a hand
near then from any direction gets rid of the buzz. I'm thinking to do with
body capacitance. Somehow.

--
*Geeks shall inherit the earth *

Dave Plowman London SW
To e-mail, change noise into sound.

Even if they are, try a capacitor from xlr ground to case.
Brian

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"Clive Arthur" wrote in message
...
On 13/04/2019 14:53, Dave Plowman (News) wrote:
snip

Both amp and crossover are fully enclosed in ally cases. Putting a hand
near then from any direction gets rid of the buzz. I'm thinking to do
with
body capacitance. Somehow.

Are these cases grounded?

Cheers
--
Clive

That was why later transistors used opaque plastic or tin cans.
Brian

--
----- --
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The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Clive Arthur" wrote in message
...
On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays
to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when
you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Unlikely but...

I once had to repair a small mixer - a simple noisy pot replacement was
needed - but I noticed a distinct buzz from the headphones. Taking scope
probe in hand I set about trying to find the fault, but it disappeared
whenever I tried to hook a probe on.

Long story short - it was a very old mixer using Germanium transistors, at
least one of which had some paint missing. Every time I bent over it to
hook a probe on I put the now light-sensitive transistor in shadow from
the fluorescent lights. Under normal use, with the covers in place, this
couldn't happen.

Cheers
--
Clive

Just wondering if all the electronics and PSU is effectively floating inside
the case, on the assumption that this will be earthed by the external
connections. If there isnt a hard connection already, might be worth trying
a 100 ohm resistor between PSU earth and mains earth?:

Charles F

"Dave Plowman (News)" wrote in message
...
In article ,
tony sayer wrote:
Both amp and crossover are fully enclosed in ally cases. Putting a hand
near then from any direction gets rid of the buzz. I'm thinking to do
with
body capacitance. Somehow.


Nah! Water don't flow uphill;!..

What are the pin connections on the 7 way XLR this unit has?..

Adjacent pins for each pair. Central pin has all the screens connected to
it.

It worked just fine with the analogue unit.

The analogue X/O has an analogue PS. The digital one an SMPS. Clutching at
straws there. ;-)

--
*Support bacteria - they're the only culture some people have *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Charles F wrote:
Just wondering if all the electronics and PSU is effectively floating
inside the case, on the assumption that this will be earthed by the
external connections. If there isnt a hard connection already, might be
worth trying a 100 ohm resistor between PSU earth and mains earth?:

By the way the buzz gradually fades up to a peak then stays there, I'm
guessing a cap is charging up somewhere.

Don't want to mess with the Behringer since it's new, but am going to try
all the options for screen grounding within the amp. At the moment, the
screens go to amp ground on each card. Not connected to ground at the XLR.
I'll try running a ground from the star ground point to the screen ground
at the XLR. The XLR body is already grounded via the chassis.

--
*42.7% of statistics are made up. Sorry, that should read 47.2% *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Brian Gaff wrote:
There is an old rule in DIY electronics. Your wonderful device works fine
when its a spiders web of bits joined by wire on a workbench, but as
soon as you put it into a case things start to not work quite right.

a rule of professional electronics is "First - check the power supply"

You might need a 'scope to do this properly - correct volts is necessarily
the answer.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

Progress.

Ran a ground inside the amp from the star ground point to the screen pin
on the XLR7. Buzz now constant - and makes no difference if you get close
or touch anything.

X/0 was bolted to the speaker stand. Stand made of ally Speedframe, and
the joints (corners etc) are plastic covered so may well not make a good
electrical connection. Amp is just sitting on crossbars and has rubber
feet, so insulated.

Unbolting the X/O and just leaving it lying on top of the amp, clean.

Insulating the mounting between X/O and stand is going to need thought,
though. At the moment it's just a basic rack mount.

--
*The early bird gets the worm, but the second mouse gets the cheese *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

Stand made of ally Speedframe

If anodized, or even just the oxide layer may make for poor electrical
contact

On 13/04/2019 13:00, Dave Plowman (News) wrote:
Three way speaker driven by three power amplifiers all balanced input.
Crossover Behringer CX3400 analogue type which sounded not bad at all.

Wanting to experiment further, got a Behringer DCX2496 which is a direct
substitute, but digital, so allows a choice of crossover curves, delays to
each unit, and EQ too.

First impression, setting it to the same as the analogue one, was no
audible difference, which is good.

But slowly, when left on, it developed a buzz from the speaker(s) Loud
enough to be annoying.

Approach the speaker and the buzz drops in level and get close enough and
it goes. So you can play it with a hand rather like a Theramin. ;-)

Thinking it faulty, got another. Same thing. Swapped back to the analogue
one - fine.

Mains grounds and XLR grounds all check out OK.

Difficult to tell if the buzz is from all three speaker units, as when you
get your ear close enough to each one, it stops.

If you power up with no signal, no buzz (at least for over an hour). With
signal, it starts after a few minutes.

Any educated guesses? I've never come across anything like this before.

Have you considered getting some clamp-on ferrites to remove common mode
signals? If there are earth currents flowing it can only help.

They are best for high frequencies, but the fact you hear a buzz rather
than hum I'm wondering if suppression within the switch mode power
supply is placing hf currents into the earth path.

In article , Dave Plowman (News)
scribeth thus
Progress.

Ran a ground inside the amp from the star ground point to the screen pin
on the XLR7. Buzz now constant - and makes no difference if you get close
or touch anything.

X/0 was bolted to the speaker stand. Stand made of ally Speedframe, and
the joints (corners etc) are plastic covered so may well not make a good
electrical connection. Amp is just sitting on crossbars and has rubber
feet, so insulated.

Unbolting the X/O and just leaving it lying on top of the amp, clean.

Insulating the mounting between X/O and stand is going to need thought,
though. At the moment it's just a basic rack mount.


What happens when you just switch the unit on and have Nothing connected
to the XLR input?

What happens if you put either a short or a low value resistor say 100
ohms across each balanced input separate ones on each input mind.


--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

"charles" wrote in message
...
In article ,
Brian Gaff wrote:
There is an old rule in DIY electronics. Your wonderful device works fine
when its a spiders web of bits joined by wire on a workbench, but as
soon as you put it into a case things start to not work quite right.

a rule of professional electronics is "First - check the power supply"

Not with a brand new device which behaves the same
way with a second copy. That wont be the power supply.

You might need a 'scope to do this properly
- correct volts is necessarily the answer.

On Mon, 15 Apr 2019 03:36:02 +1000, cantankerous trolling geezer Rot Speed,
the auto-contradicting senile sociopath, blabbered, again:


There is an old rule in DIY electronics. Your wonderful device works fine
when its a spiders web of bits joined by wire on a workbench, but as
soon as you put it into a case things start to not work quite right.

a rule of professional electronics is "First - check the power supply"

Not

Happy to be able to auto-contradict again, senile asshole? G

--
Kerr-Mudd,John addressing senile Rot:
"Auto-contradictor Rod is back! (in the KF)"
MID:

In article , Rod Speed
wrote:


"charles" wrote in message
...
In article , Brian Gaff
wrote:
There is an old rule in DIY electronics. Your wonderful device works
fine when its a spiders web of bits joined by wire on a workbench, but
as soon as you put it into a case things start to not work quite right.

a rule of professional electronics is "First - check the power supply"

Not with a brand new device which behaves the same way with a second
copy. That wont be the power supply.

could still be - a design fault, for instance

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

In article ,
Andy Burns wrote:
Dave Plowman (News) wrote:

Stand made of ally Speedframe

If anodized, or even just the oxide layer may make for poor electrical
contact

Could be. I've used rivnuts into the speedframe. But still not sure why it
would need a good ground connection to the stand?

--
*Ah, I see the f**k-up fairy has visited us again

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
Progress.

Ran a ground inside the amp from the star ground point to the screen pin
on the XLR7. Buzz now constant - and makes no difference if you get close
or touch anything.

X/0 was bolted to the speaker stand. Stand made of ally Speedframe, and
the joints (corners etc) are plastic covered so may well not make a good
electrical connection. Amp is just sitting on crossbars and has rubber
feet, so insulated.

Unbolting the X/O and just leaving it lying on top of the amp, clean.

Insulating the mounting between X/O and stand is going to need thought,
though. At the moment it's just a basic rack mount.

Wonder why walking up close to it makes the buzz go away. Presumably
that is entirely mechanical, for some reason your ears don’t hear the
buzz when they are in that location relative to the speakers.

"charles" wrote in message
...
In article , Rod Speed
wrote:


"charles" wrote in message
...
In article , Brian Gaff
wrote:
There is an old rule in DIY electronics. Your wonderful device works
fine when its a spiders web of bits joined by wire on a workbench, but
as soon as you put it into a case things start to not work quite
right.

a rule of professional electronics is "First - check the power supply"

Not with a brand new device which behaves the same way with a second
copy. That wont be the power supply.

could still be - a design fault, for instance

Very bloody unlikely with the power supply with a brand like that.

On Mon, 15 Apr 2019 04:47:54 +1000, cantankerous trolling geezer Rot Speed,
the auto-contradicting senile sociopath, blabbered, again:


a rule of professional electronics is "First - check the power supply"

Not with a brand new device which behaves the same way with a second
copy. That wont be the power supply.

could still be - a design fault, for instance

Very bloody unlikely with the power supply with a brand like that.

VERY likely that you ARE nothing but a psychopathic auto-contradicting
senile asshole, senile Rot!

--
Kerr-Mudd,John addressing senile Rot:
"Auto-contradictor Rod is back! (in the KF)"
MID:

On Mon, 15 Apr 2019 04:22:05 +1000, Jac Brown, better known as cantankerous
trolling senile geezer Rot Speed, wrote:

Unbolting the X/O and just leaving it lying on top of the amp, clean.

Insulating the mounting between X/O and stand is going to need thought,
though. At the moment it's just a basic rack mount.

Wonder why walking up close to it makes the buzz go away. Presumably
that is entirely mechanical, for some reason your ears don¢t hear the
buzz when they are in that location relative to the speakers.

You don't know ANYTHING about the set-up: but you HAVE to open your gob and
start bull****ting again, senile Rot!

--
pamela about Rot Speed:
"His off the cuff expertise demonstrates how little he knows..."
MID:

On Sun, 14 Apr 2019 08:00:12 +0100, Brian Gaff wrote:

its affected by proximity, sounds more like a parasitic oscillation of
some sort.

That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running out
of steam, do the driver chips/transistors get warm/hot?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

--
Cheers
Dave.

In article l.net,
Dave Liquorice wrote:
On Sun, 14 Apr 2019 08:00:12 +0100, Brian Gaff wrote:

its affected by proximity, sounds more like a parasitic oscillation of
some sort.

That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running out
of steam, do the driver chips/transistors get warm/hot?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

as I said - check the power supply.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

"Dave Liquorice" wrote in message
idual.net...
On Sun, 14 Apr 2019 08:00:12 +0100, Brian Gaff wrote:

its affected by proximity, sounds more like a parasitic oscillation of
some sort.

That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running out
of steam, do the driver chips/transistors get warm/hot?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

More likely to just be some mechanical quirk which sees the
buzz more audible when the ears are further from the speakers.

"charles" wrote in message
...
In article l.net,
Dave Liquorice wrote:
On Sun, 14 Apr 2019 08:00:12 +0100, Brian Gaff wrote:

its affected by proximity, sounds more like a parasitic oscillation of
some sort.

That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running out
of steam, do the driver chips/transistors get warm/hot?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

as I said - check the power supply.

Pointless with two new devices with a decent brand like that.

On Mon, 15 Apr 2019 19:37:54 +1000, cantankerous trolling geezer Rot Speed,
the auto-contradicting senile sociopath, blabbered, again:


as I said - check the power supply.

Pointless with two new devices with a decent brand like that.

What could be more pointless than your remaining days of senile trolling,
you abnormal 85-year-old senile pest?

--
The Natural Philosopher about senile Rot:
"Rod speed is not a Brexiteer. He is an Australian troll and arsehole."
Message-ID:

On Mon, 15 Apr 2019 19:36:30 +1000, Jac Brown, better known as cantankerous
trolling senile geezer Rot Speed, wrote:


That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running out
of steam, do the driver chips/transistors get warm/hot?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

More likely to just be

You disagree again, senile Rot? LMAO

--
Kerr-Mudd,John addressing senile Rot:
"Auto-contradictor Rod is back! (in the KF)"
MID:

In article , Rod Speed
wrote:


"charles" wrote in message
...
In article l.net,
Dave Liquorice wrote:
On Sun, 14 Apr 2019 08:00:12 +0100, Brian Gaff wrote:

its affected by proximity, sounds more like a parasitic oscillation
of some sort.

That's what I'd be looking for. Monitor the cuurent draw, does it
follow the buzz level? The buzz is a symptom of the PSU running out of
steam, do the driver chips/transistors get warm/hot?

As it takes a while to appear and does so slowly I'd guess that it's
only just unstable and requires a signal to kick it off.

as I said - check the power supply.

Pointless with two new devices with a decent brand like that.

somebody in purchasing thought they could shave €0.1 off the cost by buying
cheaper compoents? The BBC once sent back a whole batch of AVO8s because
they were inaccurate. It does happen.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle