[Gord]

Hi,

I have a question. Is it possible for a mic pre to overload before the
red lights go on? It is my understanding (and please correct me if I'm
wrong) that the signal gets larger as it moves from the input to the
output of a preamp, and if anything will overload, it will be at or
near the end of the circuit. If the red LED doesn't light up, I
understand it that it means that the mic pre isn't clipping at the
output stage.

Can is still clip on the front end though, without the red light? The
reason I'm asking is because lately on some vocal tracks I've noticed
some distorted parts. It's happened with my M-149 and KM-140s into
both API and GML preamps. The level going into my soundcard is fine,
the wav files on my computer aren't clipped anywhere, and during the
performance there was no clipping on the mic pres.

What on earth else could cause distorted tracks?

I'd appreciate any suggestions.

Thanks,
Gord

[Laurence Payne]

I have a question. Is it possible for a mic pre to overload before the
red lights go on? It is my understanding (and please correct me if I'm
wrong) that the signal gets larger as it moves from the input to the
output of a preamp, and if anything will overload, it will be at or
near the end of the circuit. If the red LED doesn't light up, I
understand it that it means that the mic pre isn't clipping at the
output stage.

Can is still clip on the front end though, without the red light? The
reason I'm asking is because lately on some vocal tracks I've noticed
some distorted parts. It's happened with my M-149 and KM-140s into
both API and GML preamps. The level going into my soundcard is fine,
the wav files on my computer aren't clipped anywhere, and during the
performance there was no clipping on the mic pres.

What on earth else could cause distorted tracks?

Wherever there's an interface there can be a level mis-match.
Certainly a mic can overload a preamp input. Maybe because it's a
particularly "hot" mic, maybe because the source is particularly loud.
That's why there's an input level control on a preamp, and,
presumably, why that red light is there.

But you say the recorded waveform isn't clipped? Are you sure? Look
closely and see if it's flattened off, indicating the level having
"hit the buffers" at some earlier stage. Just because the level has
been subsequently reduced and it isn't reaching 0dB doesn't mean it
isn't clipped.

[Scott Dorsey]

Gord wrote:

I have a question. Is it possible for a mic pre to overload before the
red lights go on?

Sure. It's also possible for the microphone itself to overload before
the preamp does too.

It is my understanding (and please correct me if I'm
wrong) that the signal gets larger as it moves from the input to the
output of a preamp, and if anything will overload, it will be at or
near the end of the circuit. If the red LED doesn't light up, I
understand it that it means that the mic pre isn't clipping at the
output stage.

SOME preamps have devices that check each stage for clipping and light
the light if anything goes wrong on the front end. Some do not. In
general, you shouldn't trust the lights.

Can is still clip on the front end though, without the red light? The
reason I'm asking is because lately on some vocal tracks I've noticed
some distorted parts. It's happened with my M-149 and KM-140s into
both API and GML preamps. The level going into my soundcard is fine,
the wav files on my computer aren't clipped anywhere, and during the
performance there was no clipping on the mic pres.

Do you have the gain controls on the preamps way down? That's a sign
that maybe you ought to throw a pad between the mike and the preamp.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

On Aug 15, 9:17 am, Gord wrote:

Is it possible for a mic pre to overload before the
red lights go on? If the red LED doesn't light up, I
understand it that it means that the mic pre isn't clipping at the
output stage.

It depends on where the red light is in the circuit. Often, but not
always, the "CLIP" light on a stand-alone mic preamp indicates
clipping at the first stage. Some preamps have an additional gain
stage, usually controlled by an Output Level" knob calibrated from -10
dB to +10 dB. If the input is close to clipping and you add 10 dB more
gain, it could be possible for the output stage to clip and you won't
know it until you hear it. Back in the day when they used to design
consoles right, the CLIP light often monitored multiple points in the
chain and informed you if anything (though it didn't indicate what
stage) was clipping. But they don't usually do that any more.

Understand that a preamp that can't handle a signal barely under
clipping level with its output control turned up full isn't designed
very well. But we get a lot of that these days. It's one of the many
things that differentiates a $1500 preamp from a $200 one.

Can is still clip on the front end though, without the red light? The
reason I'm asking is because lately on some vocal tracks I've noticed
some distorted parts. It's happened with my M-149 and KM-140s into
both API and GML preamps. The level going into my soundcard is fine,
the wav files on my computer aren't clipped anywhere, and during the
performance there was no clipping on the mic pres.

I don't understand. You say the level into your sound card is fine,
there is no clipping of the waveform, and no clipping of the mic
preamps, yet it sounds distorted? It must be a playback problem then.

You have some good preamps so I wouldn't expect that they'd run out of
headroom. But they also are probably capable of putting out a pretty
healthy level without clipping. If there was clipping in the recorded
waveform, I'd suspect that you may have been hitting the A/D converter
(the sound card input) too hard. You can turn down the digital level
so the sound card won't hit full scale, while still overdriving its
input stage. However, you'd still see a clipped waveform.

Check your mixing and monitoring chain. Maybe you're putting too much
poop into your monitor amplifier. Or maybe something's broken.

[David Satz]

If the red LED doesn't light up, I understand it that it means that the mic pre isn't clipping at the output stage.

Yes, that's usually how the LEDs operate. Either the output stage or
the driver stage right before it is usually monitored.


Can is still clip on the front end though, without the red light?

Absolutely. This is unfortunately a very common problem.


The reason I'm asking is because lately on some vocal tracks I've noticed some distorted parts. It's happened with my M-149 [ ... ]

Say no more; the M 149 is an almost absurdly over-sensitive
microphone. Even at fairly ordinary sound pressure levels, its output
voltage can clip the inputs of many (perhaps most) preamps.

I truly do not understand Neumann's design decision here. 47 mV/Pa in
the cardioid setting, and 62 mV/Pa in figure-8--that's 12 or more dB
higher output than most typical condenser microphones, and 30+ dB
higher than many dynamics! It's running basically at consumer aux
level. Some people allegedly don't use preamps with it at all.

Fortunately if that's the problem, the diagnosis is relatively easy to
make. Get a 10 or 20 dB in-line resistive pad (or an adjustable one
such as Shure makes in their A15 accessory line) and put it at the
input of your mike preamp the next time you use the M 149. If the
problem goes away or is greatly reduced, then the pad can also be your
longer-term solution.

The KM 140 isn't such an extremely high-output microphone by today's
standards, but when pushed hard it can put out several Volts of
signal, and that again can overload many, perhaps most, mike preamps
without a pad.

Sometimes the problem is actually wind or breath noise (e.g. vocal
popping on consonants) which can contain huge amounts of low-frequency
energy, so don't overlook the possibility of a wind or pop screen if
that applies in your case. It might even make the difference between
overload vs. no overload.


[ ... ] the wav files on my computer aren't clipped anywhere [ ... ]

As others here have pointed out, that seems strange. Maybe you mean
that the waveforms don't hit full scale (0 dBFS)? But if so, please
look carefully at the highest-peak-level waveforms you have in the
files, and you may find that they are failing to rise above a certain
threshold--which represents the clipping point of some piece of
circuitry along the way.

--best regards

[Arny Krueger]

"Gord" wrote in message
oups.com...
Hi,

I have a question. Is it possible for a mic pre to overload before the
red lights go on?

Yes -for two reasons.

(1) There may be amplification stages that clip in the signal path leading
up to the clipping light.

(2) It can take a fair amount of clipping to provide an indication that you
notice. Short clipped peaks may not be noticable.

It is my understanding (and please correct me if I'm
wrong) that the signal gets larger as it moves from the input to the
output of a preamp, and if anything will overload, it will be at or
near the end of the circuit.

That is almost always true, but not always true.

If the red LED doesn't light up, I
understand it that it means that the mic pre isn't clipping at the
output stage.

Hopefully.

Can is still clip on the front end though, without the red light?

Possible with a few preamps. Usually not.

The
reason I'm asking is because lately on some vocal tracks I've noticed
some distorted parts. It's happened with my M-149 and KM-140s into
both API and GML preamps. The level going into my soundcard is fine,
the wav files on my computer aren't clipped anywhere, and during the
performance there was no clipping on the mic pres.


What on earth else could cause distorted tracks?

So what you're really saying is that your tracks sound distorted, but they
don't look clipped?

If they are actually clipped, that fact is usually pretty apparent from the
waveform view. Flat tops and/or bottoms.

If they sound distorted, but don't look clipped, then maybe your problem is
coming from somewhere else.

How does your audio interface check out with the RMAA benchmark?

[Gord]

No part of the wave hits 0 dBFS, and the distorted parts aren't on the
peaks of the wave forms. Hmmmm......
When I get to my computer later today I will zoom in on the wave to
see if anything looks strange during the distorted parts.

The M-149 into the GML gets a really healthy signal with the gain all
the way down to 15 with a soft voice in front of it. I have a couple
of those Shure variable mic attenuators, which have the 15-20-25 dB
switch on them. I am going to try to experiment with it, or not using
a preamp at all.

My sound cards are Lynx Twos. They have their own testing method in
their FAQ. I can try that out. Where do I get the RMAA software?

I hope that there isn't a service issue with a major piece of gear.

Thanks,
Gord

[Eeyore]

Gord wrote:

I have a question. Is it possible for a mic pre to overload before the
red lights go on?

Which red light ?

Graham

[Laurence Payne]

On Wed, 15 Aug 2007 17:44:21 +0100, Eeyore
wrote:

I have a question. Is it possible for a mic pre to overload before the
red lights go on?

Which red light ?

Presumably the red light that indicates an input overload :-)

[Scott Dorsey]

Laurence Payne NOSPAMlpayne1ATdsl.pipex.com wrote:
wrote:

I have a question. Is it possible for a mic pre to overload before the
red lights go on?

Which red light ?

Presumably the red light that indicates an input overload :-)

We'll have a ball and we'll cut some rug as we dig those tunes as they
should be dug. It's a real homecoming for all those cats...
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Arny Krueger]

"Gord" wrote in message
ups.com...

No part of the wave hits 0 dBFS, and the distorted parts aren't on the
peaks of the wave forms. Hmmmm......

Not impossible, but pretty strange.

When I get to my computer later today I will zoom in on the wave to
see if anything looks strange during the distorted parts.

Flat-topping from clipping is pretty easy to see.

The M-149 into the GML gets a really healthy signal with the gain all
the way down to 15 with a soft voice in front of it. I have a couple
of those Shure variable mic attenuators, which have the 15-20-25 dB
switch on them. I am going to try to experiment with it, or not using
a preamp at all.

That will develop potentionally interesting data.

My sound cards are Lynx Twos. They have their own testing method in
their FAQ. I can try that out. Where do I get the RMAA software?

http://audio.rightmark.org/download.shtml

[Eeyore]

Laurence Payne wrote:

Eeyore wrote:

I have a question. Is it possible for a mic pre to overload before the
red lights go on?

Which red light ?

Presumably the red light that indicates an input overload :-)

I tend not to presume. Experience and all that .....

Graham

[Gord]

I had someone singing a cappella tonight and experimented with both
mics a little. Here's what I found:

-with the M-149 straight into the sound card the vocals were very
clean sounding but the signal in the computer was too small for me to
comfortably use.

-with the M-149 the sound cleaned up well once once I set the Shure
mic attenuator to 25 dB. At that point I had to crank the gain on the
GML to 40dB (from previously 15dB) and it was clean. I guess I just
underestimated how loud this mic really is. When I had the gain set
low with no attenuator, the distortion must have come from somewhere
in the mic pre between the input and the gain knob, I guess.

-the KM-140 were much easier to remedy. A small pad was enough to fix
it.

I guess with the meters you've just got to use your bean.

Gord

[Geoff]

Gord wrote:
I had someone singing a cappella tonight and experimented with both
mics a little. Here's what I found:

-with the M-149 straight into the sound card the vocals were very
clean sounding but the signal in the computer was too small for me to
comfortably use.

Wrong level, wrong impedence !



-with the M-149 the sound cleaned up well once once I set the Shure
mic attenuator to 25 dB. At that point I had to crank the gain on the
GML to 40dB (from previously 15dB) and it was clean. I guess I just
underestimated how loud this mic really is. When I had the gain set
low with no attenuator, the distortion must have come from somewhere
in the mic pre between the input and the gain knob, I guess.

The overload LED should be calibrated to indicate an overload that relates
to a specified input level.

I guess with the meters you've just got to use your bean.


Especially if not specified in the manual what the 'overload' actually
signifies.

geoff

[Chris Hornbeck]

On Wed, 15 Aug 2007 19:59:29 -0700, Gord wrote:

-with the M-149 the sound cleaned up well once once I set the Shure
mic attenuator to 25 dB. At that point I had to crank the gain on the
GML to 40dB (from previously 15dB) and it was clean. I guess I just
underestimated how loud this mic really is. When I had the gain set
low with no attenuator, the distortion must have come from somewhere
in the mic pre between the input and the gain knob, I guess.

Bringing gain reduction all the way back to the input
stage is actually pretty difficult. If done as loop feedback
common-mode rejection could be compromised by small
errors. If done as passive attenuation, noise numbers
may not look as good.

The amazingly complex and combatitive Kevin Aylward (sp?)
suggested an interesting approach, to feed the differential
input pair with separate current sources and to vary the
emitter-to-emitter resistance, varying local degeneration.

Everybody, including sadly, me, beat up on him for attitude
and Hubris problems, but it's an interesting approach. Sorry
also to see him still gone.

There's also a highly regarded but super expensive preamp
(Gordon?) using multiple stages switched in and out of use.
Another approach to the problem of "140dB".

All good fortune,

Chris Hornbeck
"It's just this little Chromium Switch.
You people are SO superstitious."

[Eeyore]

Gord wrote:

I had someone singing a cappella tonight and experimented with both
mics a little. Here's what I found:

-with the M-149 straight into the sound card the vocals were very
clean sounding but the signal in the computer was too small for me to
comfortably use.

-with the M-149 the sound cleaned up well once once I set the Shure
mic attenuator to 25 dB. At that point I had to crank the gain on the
GML to 40dB (from previously 15dB) and it was clean. I guess I just
underestimated how loud this mic really is. When I had the gain set
low with no attenuator, the distortion must have come from somewhere
in the mic pre between the input and the gain knob, I guess.

-the KM-140 were much easier to remedy. A small pad was enough to fix
it.

I guess with the meters you've just got to use your bean.

NO. A meter doesn't lie but you may not be using the equipment competently so
you 'think' it's lying.

Where in the signal chain is this stupid 'red light' of yours ? I see you refuse
to explain your setup in any meaninful way. Maybe that means you don't really
understand what you're doing (this is quite normal these days).

Graham

[Eeyore]

Chris Hornbeck wrote:

The amazingly complex and combatitive Kevin Aylward (sp?)
suggested an interesting approach, to feed the differential
input pair with separate current sources and to vary the
emitter-to-emitter resistance, varying local degeneration.

You just described a fairly typical modern mic pre.

Graham

[Arny Krueger]

"Gord" wrote in message
oups.com...

I had someone singing a cappella tonight and experimented with both
mics a little. Here's what I found:

-with the M-149 straight into the sound card the vocals were very
clean sounding but the signal in the computer was too small for me to
comfortably use.

Even if you recorded it in 24 bit mode and amplified it digitally?

-with the M-149 the sound cleaned up well once once I set the Shure
mic attenuator to 25 dB. At that point I had to crank the gain on the
GML to 40dB (from previously 15dB) and it was clean.

Ouch!

Given that there are preamps in $40 mixers that can handle this chore
without audible clipping...

I guess I just
underestimated how loud this mic really is. When I had the gain set
low with no attenuator, the distortion must have come from somewhere
in the mic pre between the input and the gain knob, I guess.

Possibly your GML has some kind of sample flaw?

-the KM-140 were much easier to remedy. A small pad was enough to fix
it.

I guess with the meters you've just got to use your bean.

Meters are like horses that run fast but have blinders on. They only see
what they are implemented to see, but they can make quick work of that.

Ears are only any good at all because they are attached to a brain. That
brain may be a little slow and limited at times, but with patience and
training it can be the ultimate piece of audio test equipment.

[Arny Krueger]

"Eeyore" wrote in message
...

I had someone singing a cappella tonight and experimented with both
mics a little. Here's what I found:

-with the M-149 straight into the sound card the vocals were very
clean sounding but the signal in the computer was too small for me to
comfortably use.

That might be alleviated with some extra gain courtesy of the DAW software.

-with the M-149 the sound cleaned up well once once I set the Shure
mic attenuator to 25 dB. At that point I had to crank the gain on the
GML to 40dB (from previously 15dB) and it was clean. I guess I just
underestimated how loud this mic really is. When I had the gain set
low with no attenuator, the distortion must have come from somewhere
in the mic pre between the input and the gain knob, I guess.

I notice that the GML 2032 has both gain and trim controls. I'd be instantly
confused until I figured out which did what.

-the KM-140 were much easier to remedy. A small pad was enough to fix
it.

Pads are band aids. They are best implemented as components of mics or
preamps. However, one does see a fair number of cut fingers in this trade,
so walking around with a pocket stash of of band aids can make some sense. I
have about 20 XLR attenuators kicking around, both fixed an variable.

I guess with the meters you've just got to use your bean.

Where in the signal chain is this stupid 'red light' of yours ? I see you
refuse
to explain your setup in any meaninful way.

Actually, we don't even know which GML preamp this is, of several
possibilities.

It looks like the GML preamps tend towards being more like channel strips
with filters and eq. That opens the door for a greater possibility of
internal clipping.

Personally, I like my preamps to be either simple and sweet like my
Symmetrix, or worked up into complete consoles like my 02R96.

[Gord]

Graham,

The GML is an 8304. The M-149 into the GML with a loud source gives me
a track that sounds distorted occasionally, especially using tighter
patterns. Nothing in my computer system is overloading. The red lights
that I spoke of are the clipping LEDs on the GML. They don't light up
when I hear the clipping. I posted my original question because with
such a low setting on the gain control (all the way down) on the GML,
I assumed in my trial and error that it might be clipping at the input
prior to the gain control. I don't believe that clipping LEDs on mic
pres are perfect, they only measure clipping at one point near the end
of the circuit. Others agreed. I tested the mic by bypassing the
preamp totally to listen for distortion. There was none. Loud sources
were recorded like this at low levels but were crystal clear. The mic
works fine.

I've tried the same thing through numerous high end preamps and most
preamps will distort with the M-149 and a loud source in front of it.
It seems three times louder than my other condernser mics. The GML
doesn't have a pad and whenever I tried 15 or 20 db of mic line
attenuation, I'd still get the occasional clipping. I discovered that
at the 25dB setting the sound starts to clean up, but I still have to
be very careful.

With the M-149 only into any pre and with a loud source, it's almost
nuts how easily it will overdrive any preamp it's plugged into. Any
preamp I tried won't show clipping on it's LEDs with the M-149, a loud
source and the preamp gain controls all the way down. I assumed that
this is a very specific case where preamp metering might not be as
accurate as a set of ears.

It seems that many people believe that preamp clipping LEDs or meters
are perfect. No clipping at the output means no clipping anywhere in
the circuit. I disagree. I think that in most cases they do their job
well, but in some cases I have to rely on my ears to figure out where
the problem is.

This was a hard one because I keep underestimating how loud it is.

I apologize if I wasn't clear.

Thanks,
Gord

[Scott Dorsey]

Gord wrote:

It seems that many people believe that preamp clipping LEDs or meters
are perfect. No clipping at the output means no clipping anywhere in
the circuit. I disagree. I think that in most cases they do their job
well, but in some cases I have to rely on my ears to figure out where
the problem is.

You shouldn't disagree. You should look at the schematic and see if it
is really the case or not.

On the Millennia HV-3 and most Orban products, the light will clip if
ANY stage clips. If you look at the schematic you will see there is a
whole hell of a lot of logic driving the light. On a lot of other
products, this isn't the case, and the light is driven by one stage,
which the schematic will indicate.

This was a hard one because I keep underestimating how loud it is.

That's why you gotta know your equipment as well as possible.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Anahata]

Gord wrote:

It seems that many people believe that preamp clipping LEDs or meters
are perfect. No clipping at the output means no clipping anywhere in
the circuit. I disagree. I think that in most cases they do their job
well, but in some cases I have to rely on my ears to figure out where
the problem is.

Normally the output stage is the only place you'd expect clipping,
because the preamp has gain, but I suppose at minimum gain (especially
if this amounts to unity gain) the input stage could run out of voltage
range before the output hits the rails.

I would expect any preamp that couldn't handle much input voltage to
have a built in (switchable) pad, otherwise its output level spec. is
lying at low gain settings.

Anahata

[Mike Rivers]

On Aug 16, 9:35 am, Gord wrote:

It seems that many people believe that preamp clipping LEDs or meters
are perfect. No clipping at the output means no clipping anywhere in
the circuit. I disagree. I think that in most cases they do their job
well, but in some cases I have to rely on my ears to figure out where
the problem is.

When I get a new piece of gear, whether it's for my own use or for a
review, one of the first things I do is check its operating level
limits and observe what the metering (if any) is telling me. I need to
know when I can trust the meters or lights and when I need to check
for overloads elsewhere. Sometimes you can't hear an overload in real
time, depending on where it occurs in the system. And "clip"
indicators don't always mean the same thing even if you know what
stage they're monitoring. Some allow more margin than others.

[Eeyore]

Gord wrote:

It seems that many people believe that preamp clipping LEDs or meters
are perfect.

They certainly *CAN* be. If they fail to do their job it's simply down to
poor/indifferent/incompetent design.


No clipping at the output means no clipping anywhere in
the circuit. I disagree.

It depends entirely on the 'gain structure'. If you try to drive an output hard
with a fader at say -20, that'll probably clip too even if everything else is
fine.


I think that in most cases they do their job well, but in some cases I have to
rely on my ears to figure out where
the problem is.

This was a hard one because I keep underestimating how loud it is.

I apologize if I wasn't clear.

There are many factors. A simple 'clip led' may respond only to the level at the
mic amp. Beter designs have 'multi-point' sensing such as post-EQ and post fader
and will give you a 'red light' even when the mic pre itself isn't close to clip
but other sections of the circuitry are.

Note that a led that indicates actual clipping is fairly useless. It should
indicate somewhere between 3-6dB BEFORE clipping to actually be useful.
Indicating a clip is a bit like shutting the stable door after the horse has
bolted. I've seen some 'clip indicators' that are indeed useless for exactly
this reason. That why I call mine a 'peak' indicator not 'clip'.

So, there's a few variables to consider. Not all red lights are created equal by
a long way.

Graham

[Eeyore]

Anahata wrote:

Gord wrote:

It seems that many people believe that preamp clipping LEDs or meters
are perfect. No clipping at the output means no clipping anywhere in
the circuit. I disagree. I think that in most cases they do their job
well, but in some cases I have to rely on my ears to figure out where
the problem is.

Normally the output stage is the only place you'd expect clipping,

Not in my experience !


because the preamp has gain, but I suppose at minimum gain (especially
if this amounts to unity gain) the input stage could run out of voltage
range before the output hits the rails.

Such things depend on the gain structure and also the internal overload
structure. How the user adjusts the controls also affects it. Not all channel
strips are born equal in such respects.

Graham

[Mike Rivers]

On Aug 16, 11:28 am, Anahata wrote:

Normally the output stage is the only place you'd expect clipping,
because the preamp has gain

Normally, you wouldn't expect clipping at all. The normal gain
structure of a preamp is that all the gain is in the first stage and
everything beyond that is essentially a buffer. A few designs have an
intermediate stage of gain, and some preamps have an output stage that
has gain as well as attenuation. But a good design should have
sufficient headroom so that anything beyond where there's gain won't
clip at the maximum level that it can see.

But it's always possible to clip the first stage. Once that happens,
it doesn't matter how much headroom the following circuitry has. It's
clipped and it stays clipped.

I would expect any preamp that couldn't handle much input voltage to
have a built in (switchable) pad

Many do. But there are considerations. If they put a pad and switch in
there, it's always going to be in the circuit (at least the switch
contacts will) and a manufacturer may want to avoid an additional
source of noise that's there all the time when it's only needed some
of the time. If you have a $2,000 preamp, you shouldn't balk at buying
a $20 in-line attenuator. And you also should take the time to learn
fully how it works and what its indicators mean. It's part of what we
call "professional."

[Paul Stamler]

There are ways to build a clip LED so that it lights up when *any* stage in
the chain clips. The lowly E-V Entertainer of yore (designed by Greg Mackie)
had such a circuit, hooked to the input preamp and the EQ amp.

Peace,
Paul

[Eeyore]

Paul Stamler wrote:

There are ways to build a clip LED so that it lights up when *any* stage in
the chain clips. The lowly E-V Entertainer of yore (designed by Greg Mackie)
had such a circuit, hooked to the input preamp and the EQ amp.

Makes Gord's GML look a bit silly really doesn't it ? That's boutique kit for
you.

Graham

[David Grant]

But you say the recorded waveform isn't clipped? Are you sure? Look
closely and see if it's flattened off, indicating the level having
"hit the buffers" at some earlier stage. Just because the level has
been subsequently reduced and it isn't reaching 0dB doesn't mean it
isn't clipped.

At what scale do you recommend looking for clipping? 1" = 1ms?



--
Posted via a free Usenet account from http://www.teranews.com

[Mike Rivers]

On Aug 16, 1:09 pm, Eeyore
wrote:

Makes Gord's GML look a bit silly really doesn't it ? That's boutique kit for
you.

Yeah, but if you have a GML, you're expected to know how to use it
correctly. With an EV all-in-one system, they need to protect the user
from being too much of a dingbat so they put a lot of blinky red
lights on it.

[Eeyore]

Mike Rivers wrote:

On Aug 16, 1:09 pm, Eeyore
wrote:

Makes Gord's GML look a bit silly really doesn't it ? That's boutique kit for
you.

Yeah, but if you have a GML, you're expected to know how to use it
correctly. With an EV all-in-one system, they need to protect the user
from being too much of a dingbat so they put a lot of blinky red
lights on it.

I found this about the GML mic amps.

" A +24dBv CLIP indicator warns of any impending overloads "
http://www.massenburg.com/cgi-bin/ml/mod8304

I'm not sure if they mean +24dBV or +24dBU (I've hardly seen dBv in nearly 30
years) but either way that's near useless since most other kit (that you connect it
to) will clip well before +24.

Boutique nonsense is my conclusion.

Graham

[Geoff]

Eeyore wrote:

I found this about the GML mic amps.

" A +24dBv CLIP indicator warns of any impending overloads "
http://www.massenburg.com/cgi-bin/ml/mod8304


"Impending overloads' . Wow. How does it know what signal is about to come
?

geoff

[David Satz]

How does it know what signal is about to come ?

That's just a pretentious way of saying, "The LED lights up when the
signal levels are a few dB below overload." In some preamps if the LED
comes on it means "You blew it," while in others, it means "You're
getting some nice levels now; keep it up."

--best regards

[Chris Hornbeck]

On Thu, 16 Aug 2007 11:36:27 +0100, Eeyore
wrote:

The amazingly complex and combatitive Kevin Aylward (sp?)
suggested an interesting approach, to feed the differential
input pair with separate current sources and to vary the
emitter-to-emitter resistance, varying local degeneration.

You just described a fairly typical modern mic pre.

Really? I thought everything was still instrumentation
inputs and such. I'm out of date.

The locally degenerated input should have potentially a
really large input acceptance. I wonder if the OP has
the degeneration ("input trim") somehow mis-set?


Thanks, as always,

Chris Hornbeck
"It's just this little Chromium Switch.
You people are SO superstitious."

[Agent 86[_2_]]

Eeyore wrote:

I found this about the GML mic amps.

" A +24dBv CLIP indicator warns of any impending overloads "
http://www.massenburg.com/cgi-bin/ml/mod8304

I'm not sure if they mean +24dBV or +24dBU (I've hardly seen dBv in nearly
30 years) but either way that's near useless since most other kit (that
you connect it to) will clip well before +24.


Then you watch the meters on the other gear and congratulate yourself for:

a. buying a preamp with more headroom than you need.
b. not paying extra for meters when a single light tells you more than you
need to know about what's happening in your preamp.

[Mike Rivers]

On Aug 16, 3:51 pm, Eeyore
wrote:

I found this about the GML mic amps.

" A +24dBv CLIP indicator warns of any impending overloads
http://www.massenburg.com/cgi-bin/ml/mod8304

I'm not sure if they mean +24dBV or +24dBU (I've hardly seen dBv in nearly 30
years) but either way that's near useless since most other kit (that you connect it
to) will clip well before +24.

Given who it is, I suspect that it may very well be +24 dBV, though it
might have been more "marketing" to say +26 dBu, which is higher than
most anything to which it would be connected. The trouble with kids
these day, though, is that they want all the lights to light because
they're afraid that either they'll be losing resolution or their CD
won't be loud enough.

Boutique nonsense is my conclusion.

I don't think that's an appropriate term to use for describing high
grade pro audio equipment. Too bad some magazine writers decided to
pick it up because it sounds cool.

[Scott Dorsey]

Eeyore wrote:

I found this about the GML mic amps.

" A +24dBv CLIP indicator warns of any impending overloads "
http://www.massenburg.com/cgi-bin/ml/mod8304

I'm not sure if they mean +24dBV or +24dBU (I've hardly seen dBv in nearly
30 years) but either way that's near useless since most other kit (that
you connect it to) will clip well before +24.

No, the clip light tells you if the GML is clipping. If you're plugging it
into something else that can't handle high levels, you'll have to rely on
the clip light on THAT device to tell if IT is clipping.

Snide comment about boutique equipment deleted

It's true that some of the boutique gear is pretty silly. But the GML is
definitely not in that category. You really should refrain from making
snide comments.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[david correia]

In article ,
"Arny Krueger" wrote:

It looks like the GML preamps tend towards being more like channel strips
with filters and eq. That opens the door for a greater possibility of
internal clipping.

Personally, I like my preamps to be either simple and sweet like my
Symmetrix, or worked up into complete consoles like my 02R96.



He posted later saying it was an 8304. Which has exactly one knob and a
clip light for each of the 4 pre's.


If you were recording something complex, say a vocal chorus or a grand
piano, and you took your favorite mic and plugged it into your Symmetrix
and then again into the GML, you would have a new point of view.





David Correia
www.Celebrationsound.com

[david correia]

In article .com,
Gord wrote:

Graham,

The GML is an 8304. The M-149 into the GML with a loud source gives me
a track that sounds distorted occasionally, especially using tighter
patterns. Nothing in my computer system is overloading. The red lights
that I spoke of are the clipping LEDs on the GML. They don't light up
when I hear the clipping. I posted my original question because with
such a low setting on the gain control (all the way down) on the GML,
I assumed in my trial and error that it might be clipping at the input
prior to the gain control. I don't believe that clipping LEDs on mic
pres are perfect, they only measure clipping at one point near the end
of the circuit. Others agreed. I tested the mic by bypassing the
preamp totally to listen for distortion. There was none. Loud sources
were recorded like this at low levels but were crystal clear. The mic
works fine.

I've tried the same thing through numerous high end preamps and most
preamps will distort with the M-149 and a loud source in front of it.
It seems three times louder than my other condernser mics. The GML
doesn't have a pad and whenever I tried 15 or 20 db of mic line
attenuation, I'd still get the occasional clipping. I discovered that
at the 25dB setting the sound starts to clean up, but I still have to
be very careful.

With the M-149 only into any pre and with a loud source, it's almost
nuts how easily it will overdrive any preamp it's plugged into. Any
preamp I tried won't show clipping on it's LEDs with the M-149, a loud
source and the preamp gain controls all the way down. I assumed that
this is a very specific case where preamp metering might not be as
accurate as a set of ears.

It seems that many people believe that preamp clipping LEDs or meters
are perfect. No clipping at the output means no clipping anywhere in
the circuit. I disagree. I think that in most cases they do their job
well, but in some cases I have to rely on my ears to figure out where
the problem is.

This was a hard one because I keep underestimating how loud it is.

I apologize if I wasn't clear.

Thanks,
Gord





Give GML a call. The one time I called them it was George who answered
the phone.

As you've already discovered, looks like you to have to pad the output
of that mic.

Have you heard what the mic sounds like without using a pre, using just
a high quality line level boost? Might be interesting to hear.

As an aside, I have found the clipping light on the gml to be
conservative. A track will sound fine even if the led lit a few times
during a take.

I've really enjoyed my gml for almost 20 years now. I wouldn't want to
track a lead vocal, a drum kit, or a piano without it. It delivers a lot
out of your mics.




David Correia
www.Celebrationsound.com

[Paul Stamler]

Okay, there's something in this story that doesn't compute. The OP has
reported:

1) Audible clipping with 15dB of gain on the preamp.

2) No audible clipping with 25dB pad followed by 40dB of gain on the preamp.

3) Inadequate levels when running the M 149 straight into the sound card.

GML reports a clip light which flashes at +24dBV; let's take him at his word
and assume that the light is, therefore, flashing at about +26dBu,
reasonable for a preamp with, say, +/-24V regulated supplies. (The external
supply provides +/-28V, and I assume this gets regulated down to about 24V
in the box.

Let's do the arithmetic. Assume the preamp really is clipping at +26dBu out.
It seems reasonable (actually conservative; bear with me) that the output
amplifiers for each leg might be clipping at, say, +20dBu. That would be
+26dBu out, since they're feeding the two output pins with opposite
polarity.

Let's make a jump now, and assume the input stage (before any gain
switching) also clips when it's putting out +20dBu. Since the OP had the
gain set for +15dB, that means the microphone must have been putting out
about +5dBu on loud peaks.

That's not ridiculous; a U 87 has been shown to put out 0dBu when you yell
into it, and the M 149 apparently is more sensitive than a U 87. I've seen
comparable levels coming out of other modern, hot, transformerless mics.

But if that's what the mic is putting out, *why is the level inadequate when
you run it straight into the sound card*??? If it's hot enough to clip the
input of a preamp, it should be plenty hot to drive a +4dBu (nominal level)
sound card input. And, pace Eeyore, the impedance isn't an issue. The sound
card's input impedance is presumably between 5k and 10k, which should leave
the mic essentially unloaded. And there's no transformer that needs
termination to avoid ringing.

So something isn't right. If I had to guess, I'd say the preamp might be
broken. To the OP: One thing to check might be whether all the power supply
voltages (coming from the power pack) are what they're supposed to be.
(Don't short one out while measuing.)

In any case, I think a call to GML might be in order.

Peace,
Paul