Maker Pro
Maker Pro

Triac hash noise and stage amps/mixers.

N

N Cook

Jan 1, 1970
0
Eventually me and owner have discovered what the intermittant noise problem
is with his large mixer. I could never find the reported noise problem on
the bench. Eventually the owner twigged that the problem only occured at 2
venues and not the others. Both have full dimmable stage lighting, but not
audio modulated or sequenced , and what he was reporting as excessive
background hiss static was mains-bourne spike noise from the triacs.
What sort of retro-fit mains filtering for his mixer.?
Internal or external in-line Y/delta + small choke unit, plug-in pulse/surge
protector, or one of the large choke/transformer? types that hi-fi bods use
in the mains feed..
 
R

Ron(UK)

Jan 1, 1970
0
N said:
Eventually me and owner have discovered what the intermittant noise problem
is with his large mixer. I could never find the reported noise problem on
the bench. Eventually the owner twigged that the problem only occured at 2
venues and not the others. Both have full dimmable stage lighting, but not
audio modulated or sequenced , and what he was reporting as excessive
background hiss static was mains-bourne spike noise from the triacs.
What sort of retro-fit mains filtering for his mixer.?
Internal or external in-line Y/delta + small choke unit, plug-in pulse/surge
protector, or one of the large choke/transformer? types that hi-fi bods use
in the mains feed..

Does he get the noise with all inputs turned down and with no cables
plugged into any inputs? Is it all balanced lines on input and output?


Chances are it's a cabling problem, or an earth missing. Does it have a
built in effects unit? ( a prime colector of interferance)

What make and model of mixer is it?

Ron(UK)
 
E

Eeyore

Jan 1, 1970
0
N said:
Eventually me and owner have discovered what the intermittant noise problem
is with his large mixer. I could never find the reported noise problem on
the bench. Eventually the owner twigged that the problem only occured at 2
venues and not the others.

A smart chappy eh ?

Both have full dimmable stage lighting, but not
audio modulated or sequenced , and what he was reporting as excessive
background hiss static was mains-bourne spike noise from the triacs.

Duh !

What sort of retro-fit mains filtering for his mixer.?
Internal or external in-line Y/delta + small choke unit, plug-in pulse/surge
protector, or one of the large choke/transformer? types that hi-fi bods use
in the mains feed..

More to the point. How on earth is mains noise getting in to the mixer
electronics in the first place ?

Graham
 
N

N Cook

Jan 1, 1970
0
Ron(UK) said:
Does he get the noise with all inputs turned down and with no cables
plugged into any inputs? Is it all balanced lines on input and output?


Chances are it's a cabling problem, or an earth missing. Does it have a
built in effects unit? ( a prime colector of interferance)

What make and model of mixer is it?

Ron(UK)

Phonic 12 Impact ,12 channel mixer, 25 x 16 inch , all steel cased and no
earth bond problem. No internal effects , no known inputs problems and he
has swapped inputs and leads and instruments and would suggest a problem
with the mixer.
 
M

Meat Plow

Jan 1, 1970
0
Phonic 12 Impact ,12 channel mixer, 25 x 16 inch , all steel cased and no
earth bond problem. No internal effects , no known inputs problems and he
has swapped inputs and leads and instruments and would suggest a problem
with the mixer.

I would start with the source of the noise and not so much as trying to
filter it out. I don't think there is a problem with the mixer. I've
gigged on and off for 20 years and noise from dimmers and dimmer/lighting
packs is a fact of life.
 
R

Ron(UK)

Jan 1, 1970
0
N said:
Phonic 12 Impact ,12 channel mixer, 25 x 16 inch , all steel cased and no
earth bond problem. No internal effects , no known inputs problems and he
has swapped inputs and leads and instruments and would suggest a problem
with the mixer.

But does it buzz with no input cables in? If not, it`s a cable problem,
probably using an unbalanced line in for guitar (or some other
instrument) instead of a balanced line into a microphone input and a di box.

The correct fault finding method is to strip it back to basics to see
where the hum gets in, if it`s coming up the mains cable, you probably
have a struggle on your hands, it IS a budget mixer.

Ron(UK)
 
E

Eeyore

Jan 1, 1970
0
N said:
Ron(UK) wrote


Phonic 12 Impact ,12 channel mixer, 25 x 16 inch , all steel cased and no
earth bond problem. No internal effects , no known inputs problems and he
has swapped inputs and leads and instruments and would suggest a problem
with the mixer.

Not really.

Have you checked he's got his mics wired balanced and that they're on XLRs?

Musos have been known to plug mics with 'mono' jack plugs into the line inputs
and crank the gain to max to compensate.

Graham
 
E

Eeyore

Jan 1, 1970
0
Meat said:
I would start with the source of the noise and not so much as trying to
filter it out. I don't think there is a problem with the mixer. I've
gigged on and off for 20 years and noise from dimmers and dimmer/lighting
packs is a fact of life.

Yup, it's far more likely to be a cabling or earth loop type problem.

Check all the points Ron made too.

Graham
 
D

Dave Plowman (News)

Jan 1, 1970
0
Eventually me and owner have discovered what the intermittant noise
problem is with his large mixer. I could never find the reported noise
problem on the bench. Eventually the owner twigged that the problem only
occured at 2 venues and not the others. Both have full dimmable stage
lighting, but not audio modulated or sequenced , and what he was
reporting as excessive background hiss static was mains-bourne spike
noise from the triacs. What sort of retro-fit mains filtering for his
mixer.? Internal or external in-line Y/delta + small choke unit, plug-in
pulse/surge protector, or one of the large choke/transformer? types that
hi-fi bods use in the mains feed..

I've yet to come across a pro mixer not designed for this sort of venue -
so I'd look to the earthing etc if you're certain it's not being picked up
on the cables. Unless of course the mixer is situated right beside a
dimmer trolley. If it is a cable problem, star quad is likely to sort it.

Worth also checking any DIs in use - some don't make a decent job of
balancing their output.
 
N

N Cook

Jan 1, 1970
0
Ron(UK) said:
But does it buzz with no input cables in? If not, it`s a cable problem,
probably using an unbalanced line in for guitar (or some other
instrument) instead of a balanced line into a microphone input and a di box.

The correct fault finding method is to strip it back to basics to see
where the hum gets in, if it`s coming up the mains cable, you probably
have a struggle on your hands, it IS a budget mixer.

Ron(UK)

I'm not going to start going to his gigs, as they are quite distant regular
venues, so will have to coach him for what to look for.
He plays with another using in all about 10 instruments/mikes and it seems
its a consistant problem, constant level problem, at those 2 venues ,
whatever instruments/cables. They play seated but I'll ask one to move
around at sound check and get the other to monitor for any change in hash
level which should vary if induced from the lighting cabling via air into
signal leads, cf mains-bourne should be constant level.
While I've got the mixer here open for a minor repair I'll fix a 3 amp
in-line small off-the-shelf standard C/L filter inside , on the mains feed.
 
D

Dave Plowman (News)

Jan 1, 1970
0
I'm not going to start going to his gigs, as they are quite distant
regular venues, so will have to coach him for what to look for. He plays
with another using in all about 10 instruments/mikes and it seems its a
consistant problem, constant level problem, at those 2 venues , whatever
instruments/cables. They play seated but I'll ask one to move around at
sound check and get the other to monitor for any change in hash level
which should vary if induced from the lighting cabling via air into
signal leads, cf mains-bourne should be constant level. While I've got
the mixer here open for a minor repair I'll fix a 3 amp in-line small
off-the-shelf standard C/L filter inside , on the mains feed.

Again I'd be amazed if the PS doesn't include decent filtering - after all
even the cheapest mixer is likely to be used along with light dimmers.
Many will pick up heavy interference nearby though - hence not having a
mobile phone close to them - due to being unbalanced internally.
As I said, I'd ask if it is situated close to a dimmer rack etc at the
location where it gives the problem. And if it is, the only practical way
is re-siting either, as screening will be very difficult.
 
R

Ron(UK)

Jan 1, 1970
0
N said:
I'm not going to start going to his gigs, as they are quite distant regular
venues, so will have to coach him for what to look for.
He plays with another using in all about 10 instruments/mikes and it seems
its a consistant problem, constant level problem, at those 2 venues ,
whatever instruments/cables. They play seated but I'll ask one to move
around at sound check and get the other to monitor for any change in hash
level which should vary if induced from the lighting cabling via air into
signal leads, cf mains-bourne should be constant level.
While I've got the mixer here open for a minor repair I'll fix a 3 amp
in-line small off-the-shelf standard C/L filter inside , on the mains feed.

It`s a constant level? Do you mean it doesn`t change with the level of
the light dimmers? Dimmer hash is pretty instantly recognisable to
anyone in the business of PA hire, it changes in 'tone' as the lights
are brought up and down. Are there any neon signs in this venue? they
kick out all sorts of nasty chit, but nothing a properly set up rig
can`t reject. i.e. fully balanced lines in and out.

Just tell then to disconnect each channel in turn till the buzz goes
away. If it still buzzes with no inputs, it`s the desk, or the cables to
the power amps. It`s not impossible that it`s being induced into the
speaker cables.

Also, make sure that they arent using el-cheapo mains fourways for
distro, sell them some decent quality ones - I like the orange Permaplug
ones.

It might be some kind of mains phase issue. Usually stage lighting is
spread across all three phases, but sometimes it`s all dumped on one
phase causing wierd imbalances.

It`s still most likely to be an unbalanced lead into a line input or a
mike cable fault. Make sure that they aren't using a high impedance mike
anywhere.

Ron(UK)
 
R

Ron(UK)

Jan 1, 1970
0
Dave said:
Again I'd be amazed if the PS doesn't include decent filtering - after all
even the cheapest mixer is likely to be used along with light dimmers.
Many will pick up heavy interference nearby though - hence not having a
mobile phone close to them - due to being unbalanced internally.
As I said, I'd ask if it is situated close to a dimmer rack etc at the
location where it gives the problem. And if it is, the only practical way
is re-siting either, as screening will be very difficult.

If that`s the case, sometimes, just turning the unit through 90 degrees
will reduce the buzz.

Ron(UK)
 
D

Dave Plowman (News)

Jan 1, 1970
0
If that`s the case, sometimes, just turning the unit through 90 degrees
will reduce the buzz.

Yes. It sounds as if the operator is a newbie at this sort of thing - most
will be quite used to the tricks of the trade for reducing lighting
interference which has been a problem since DC disappeared and solid state
dimmers arrived. Or even before that - what were the 'valve' ones -
Klyriston?
 
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