Is anyone here still using AKG C451 mics, or remembers using them?

I've had my 4 for some time but am becoming more and more aware of a low
level hum on the output. The hum gets worse the more of them that are
plugged in to the mixer. If only one is faded up, the hum gets worse as
others are plugged in. At first I thought the phantom power supply was
giving trouble but I have now tried them on two different mixers and a,
stereo, standalone mic pre-amp (M-Audio) with similar results. I wondered
if one of them was drawing too much current and dragging the PS down but it
doesn't seem to matter which combination of mics I use. I think the hum is
100 hertz, which still suggests PS but on three differant i/ps?

Both mixers and the standalone are fine when used with dynamic mics.

The C451s are long in the tooth so are they prone to draw high current as
they age? Or am I barking up the wrong tree altogether?

Any suggestions, polite ones, would be appreciated.

Thanks.

Alan S.

Does the buzz happen in any location, or just in one. I was thinking some
kind of inductive or rf pick up in the particular location, after all, not
much to go wrong in this way is there?
Brian

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Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Alan S." wrote in message
.145...
Is anyone here still using AKG C451 mics, or remembers using them?

I've had my 4 for some time but am becoming more and more aware of a low
level hum on the output. The hum gets worse the more of them that are
plugged in to the mixer. If only one is faded up, the hum gets worse as
others are plugged in. At first I thought the phantom power supply was
giving trouble but I have now tried them on two different mixers and a,
stereo, standalone mic pre-amp (M-Audio) with similar results. I wondered
if one of them was drawing too much current and dragging the PS down but
it
doesn't seem to matter which combination of mics I use. I think the hum is
100 hertz, which still suggests PS but on three differant i/ps?

Both mixers and the standalone are fine when used with dynamic mics.

The C451s are long in the tooth so are they prone to draw high current as
they age? Or am I barking up the wrong tree altogether?

Any suggestions, polite ones, would be appreciated.

Thanks.

Alan S.

"Alan S."

Is anyone here still using AKG C451 mics, or remembers using them?


** The C451 is not a mic - but a pre-amp / handle for the CK series of
capsules.


I've had my 4 for some time but am becoming more and more aware of a low
level hum on the output. The hum gets worse the more of them that are
plugged in to the mixer. If only one is faded up, the hum gets worse as
others are plugged in.

** That can only mean the phantom power has hum.


At first I thought the phantom power supply was
giving trouble but I have now tried them on two different mixers and a,
stereo, standalone mic pre-amp (M-Audio) with similar results. I wondered
if one of them was drawing too much current and dragging the PS down but
it
doesn't seem to matter which combination of mics I use. I think the hum is
100 hertz, which still suggests PS but on three differant i/ps?

** Your story indicates that it is all 3.


Both mixers and the standalone are fine when used with dynamic mics.


** Naturally.


The C451s are long in the tooth so are they prone to draw high current as
they age?

** C451s draw about 6mA from a 48 volt phantom supply - many other mics
draw less than this.

The design is such that they work fine from as little as 9 volts of phantom
at the mic signal pins, with a much lower current draw than when that
voltage is 48.

From recollection, C451s are not particularly immune from hum on the phantom
supply ( there should NOT be any of course ) so your probelm as decribed is
not likely due to any fault in the mics.


...... Phil

"Brian Gaff" wrote in
m:

Does the buzz happen in any location, or just in one. I was thinking
some kind of inductive or rf pick up in the particular location, after
all, not much to go wrong in this way is there?
Brian


It has been apparent at two different locations in particular, both of them
CofE churches as it happens. It was, however, with the same mic cables. Can
I assume that the phantom power supply would not work if one leg or ground
is missing on the cable? They were each approximately 25metres.

Thanks for your thought, but to be pedantic, it is a hum, not a buzz. If it
was a buzz I'd be looking for things like lighting dimmer buzz etc.

Thanks again.

Alan S.

"Phil Allison" wrote in
:


"Alan S."

Is anyone here still using AKG C451 mics, or remembers using them?


** The C451 is not a mic - but a pre-amp / handle for the CK series
of capsules.

I think most epeople referred to them as C451 mics but for the record,
it was C451 bodies with CK1 capsules.



I've had my 4 for some time but am becoming more and more aware of a
low level hum on the output. The hum gets worse the more of them that
are plugged in to the mixer. If only one is faded up, the hum gets
worse as others are plugged in.

** That can only mean the phantom power has hum.


At first I thought the phantom power supply was
giving trouble but I have now tried them on two different mixers and
a, stereo, standalone mic pre-amp (M-Audio) with similar results. I
wondered if one of them was drawing too much current and dragging the
PS down but it
doesn't seem to matter which combination of mics I use. I think the
hum is 100 hertz, which still suggests PS but on three differant
i/ps?

** Your story indicates that it is all 3.

My first reaction but I couldn't couldn't believe 3 different PSs were
_faulty_.


Both mixers and the standalone are fine when used with dynamic mics.


** Naturally.


The C451s are long in the tooth so are they prone to draw high
current as they age?

** C451s draw about 6mA from a 48 volt phantom supply - many other
mics draw less than this.

The design is such that they work fine from as little as 9 volts of
phantom at the mic signal pins, with a much lower current draw than
when that voltage is 48.

From recollection, C451s are not particularly immune from hum on the
phantom supply ( there should NOT be any of course ) so your probelm
as decribed is not likely due to any fault in the mics.


..... Phil





If I have three phantom supplies which are unable to deliver the
required current, which appears to be the case, then, I need to use an
outside supply. I've been out of the scene for a few years so which are
good units these days?

Thanks for your input, Phil.

Alan S.

In article ,
Alan S. wrote:
Is anyone here still using AKG C451 mics, or remembers using them?

Hi Alan ;-) Yes indeedy - I also have a few.


I've had my 4 for some time but am becoming more and more aware of a low
level hum on the output. The hum gets worse the more of them that are
plugged in to the mixer. If only one is faded up, the hum gets worse as
others are plugged in. At first I thought the phantom power supply was
giving trouble but I have now tried them on two different mixers and a,
stereo, standalone mic pre-amp (M-Audio) with similar results. I
wondered if one of them was drawing too much current and dragging the
PS down but it doesn't seem to matter which combination of mics I use.

Properly designed phantom should be immune to a dead short since standoff
resistors are used at each mic input. That's not to say all mixers have
properly designed phantom.


I think the hum is
100 hertz, which still suggests PS but on three differant i/ps?

Both mixers and the standalone are fine when used with dynamic mics.

The C451s are long in the tooth so are they prone to draw high current
as they age? Or am I barking up the wrong tree altogether?

Not one I've come across.

Any suggestions, polite ones, would be appreciated.

It does sound like a PS fault to me - have you tried other phantom powered
mics? Have you access to a scope to look at the DC?

--
*Never underestimate the power of very stupid people in large groups *

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

"Alan S." wrote in message
.145...
"Brian Gaff" wrote in
m:

Does the buzz happen in any location, or just in one. I was thinking
some kind of inductive or rf pick up in the particular location, after
all, not much to go wrong in this way is there?
Brian


It has been apparent at two different locations in particular, both of
them
CofE churches as it happens. It was, however, with the same mic cables.

Then I think the cables might well need looking at.

Can
I assume that the phantom power supply would not work if one leg or ground
is missing on the cable? They were each approximately 25metres.

If ground is missing the phantom power will not work. It will work if one
leg is missing, but you will get poor audio and added noise.


David.

In article ,
Alan S. wrote:
It has been apparent at two different locations in particular, both of
them CofE churches as it happens. It was, however, with the same mic
cables. Can I assume that the phantom power supply would not work if
one leg or ground is missing on the cable? They were each approximately
25metres.

Seem to remember a one legged cable just results in a low output from a
451. Which may well give hum if you increase the gain for a distant mic.
Do you not have a 'bright eyes' phantom tester? Basically two leds built
into an XLR. If not contact me - I'm sure I've got a spare.

If you lose the screen you'll get no audio at all, IIRC.

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

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

"David Looser" wrote in
:

"Alan S." wrote in message
.145...
"Brian Gaff" wrote in
m:

Does the buzz happen in any location, or just in one. I was thinking
some kind of inductive or rf pick up in the particular location,
after all, not much to go wrong in this way is there?
Brian


It has been apparent at two different locations in particular, both
of them
CofE churches as it happens. It was, however, with the same mic
cables.

Then I think the cables might well need looking at.

Yes, it's looking that way. I'll bet there's a rogue somewhere! Now
where's my bright-eyes?



Can
I assume that the phantom power supply would not work if one leg or
ground is missing on the cable? They were each approximately
25metres.

If ground is missing the phantom power will not work. It will work if
one leg is missing, but you will get poor audio and added noise.


David.





Thanks again.

Alan S.

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

Seem to remember a one legged cable just results in a low output from a
451. Which may well give hum if you increase the gain for a distant mic.


With a one-legged cable the audio must pass through the phantom power
supply, thus directly adding any hum or noise it creates to the audio. The
level will also be down.

If you lose the screen you'll get no audio at all, IIRC.

Because there will then be no phantom power at the microphone.

David.