mixer measurements

Archived from groups: rec.audio.pro (More info?)

"Tim Perry" <timperryspammenot@adelphia.net> wrote in message
news:ALOdnbqd_44xs7XcRVn-og@adelphia.com...
> i decided to run some measurements on the Behringer mixer i just got then
> compare it to some other mixers. here's what i got:
>
> Behringer MX 2642A
>
> % THD
> 50 Hz .048
> 100 Hz .05
> 1000 Hz .05
> 10 kHz .058
> 15 kHz .064
>
> IM distortion (60 & 7kHz) .06 %
> noise* .0355 mv
>
> Soundcraft F1-16
>
> %THD
> 50 Hz .048
> 100 Hz .05
> 1000 Hz .052
> 10 kHz .06
> 15 kHz .068
>
> IM .052 %
> noise* .035 mv
>
> Mackie 32-8
>
> %THD
> 50 Hz .052
> 100 Hz .058
> 1000 Hz .05
> 10 kHz .064
> 15 kHz .072
>
> IM .06 %
> noise* .09 mv
>
> no mixer: straight from sig gen to analyzer
>
> %THD
> 50 Hz .046
> 100 Hz .048
> 1000 Hz .05
> 10 kHz .056
> 15 kHz .062
>
> IM .052 %
> noise* .014 mv
>
> *methodology:
> noise measurements made referenced to -40 dB input and 0 dB output with
sig
> gen muted and one ch open all others down.
> all other measurement made with 150 ohm source at -40 dB into mic input.
> mixer output set to 0 dB into active balanced (transformerless) meter.
tone
> controls all at neutral.
> in "straight through" measurements the sig gen output was increased by 20
> dB.
>
>
> conclusion: i was rather surprised at how well the 2642 tested relative to
> the other units.
> the online spec sheet claims a THD of .007% @ +4 dB
> i wonder if its an actual measurement or is derived in some fashion.



** Most likely just measued the usual way.


> my equipment seems to be functioning within its specified tolerances.
> http://www.pi-usa.com/ag51/ag51g.htm#SPECIFICATIONS
>

** But is not up to modern standards.

Decent audio generators have less than 0.001% THD at 1kHz nowadays.





........... Phil

Archived from groups: rec.audio.pro (More info?)

"Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
news:41283E6F.1A27FE5@hotmail.com

> Tim Perry wrote:

>> i decided to run some measurements on the Behringer mixer i just got
>> then compare it to some other mixers. here's what i got:

> < snip near identical figures >

Agreed, the test results are very similar, thus raising the possibility that
these are not actually tests of the UUTs, but instead tests of the residuals
of the test equipment.

>> *methodology:
>> noise measurements made referenced to -40 dB input and 0 dB output
>> with sig gen muted and one ch open all others down.
>> all other measurement made with 150 ohm source at -40 dB into mic
>> input. mixer output set to 0 dB into active balanced
>> (transformerless) meter. tone controls all at neutral.
>> in "straight through" measurements the sig gen output was increased
>> by 20 dB.

http://www.pi-usa.com/ag51/ag51g.htm#SPECIFICATIONS

The INTRINSIC DISTORTION *
Harmonic Low Distortion Fast Response
20 Hz to 10 kHz less than 0.05% less than 1%
10 kHz to 20 kHz less than 0.08% less than 1%
Intermodulation less than 0.03%
Incidental FM(3.15 kHz) less than 0.01%

This would be pretty hot stuff in 1965, but by modern standards it's pretty
grim.

I'll give you modern farily mninmal standards in a nutshell:

All spurious responses and noise 100 dB or down (0.001%) or better.
Frequency response (I don't see it on the web page) within 0.1 dB or better
with phase response to match per minimum phase.

And here's SOTA:

All spurious responses and noise 120 dB or down (0.0001%) or better.
Frequency response within 0.02 dB or better with phase response to match
per minimum phase.

I think that test equipment that met minimum standards would tell a
different story.

You can emlulate really pretty good modern test equipment with a good
computer audio interface and software such as the Audio Rightmark analyzer.

>> conclusion: i was rather surprised at how well the 2642 tested
>> relative to the other units.

In fact, you seem to have published tests of essentially the residuals of
your test gear, twice.

>> the online spec sheet claims a THD of .007% @ +4 dB
>> i wonder if its an actual measurement or is derived in some fashion.
>> my equipment seems to be functioning within its specified tolerances.

>> http://www.pi-usa.com/ag51/ag51g.htm#SPECIFICATIONS

> Your measurement gear is rubbish.

Agreed. Looks nice, though. It's really a historic artifact from the 1960s.
I built stuff that was better from modified Heathkits in the 1970s.

> With residual figures like that - you'll never be able to measure
> anything meaningful. You're simply measuring the test equipment.

Agreed. First step in any measuement paradigm is know your geat. As you
suggest, that means looping it and seeing what the numbers are.

> Audio Precision kit for example, typically measures 0.0007% THD ( 7
> parts per million ) that's -104dB SINAD if you prefer a dB version,
> with output looped back to input ( certainly at 1 kHz ).

I think that's the old stuff or maybe APs somewhat conservative specs. I'm
told that the new stuff is of the same order of a LynxTWO, whose test
results I published at http://www.pcavtech.com/soundcards/LynxTWO/index.htm
.. It shows up to 115 SNAD with a 20-20K measurement bandwidth, and 107 dB at
comparable bandwidths to an AP S2.

Archived from groups: rec.audio.pro (More info?)

thanks for you comments gentelman.

my gear works fine for my normal aplications (level setting and
troubleshooting, often in high RF envirnments).

i was able to get a much better reading using a DAW and soundcard as a
source (.01% THD on the Behringer), however this is through the line input.
i think iwill have to build a input pad if i want to continue.

i was mostly curious as to noise mesurments.
is the procedure i described sufficienty accurate to compare the results
with published specs?
with 15 uv of self noise is this equipment sufficient to measure noise in
modern gear? http://www.pi-usa.com/aa51a/aa51ag.htm#SPECIFICATIONS

Archived from groups: rec.audio.pro (More info?)

"Eric K. Weber" <eric-nospam@webermusic.com> wrote in message
news:jb4Wc.21$mW5.29830@news.uswest.net...
> For the noise measurement what did you terminate the input with, a short
or
> a metal film resistor?
>
> Rgds:
>
> Eric
>

sig gen switched from operate to test, which mutes the osc .... 150 ohm
output.

Archived from groups: rec.audio.pro (More info?)

Arny Krueger wrote:

> "Pooh Bear" <rabbitsfriendsandrelations@hotmail.com> wrote in message
> news:41283E6F.1A27FE5@hotmail.com
>
> > Audio Precision kit for example, typically measures 0.0007% THD ( 7
> > parts per million ) that's -104dB SINAD if you prefer a dB version,
> > with output looped back to input ( certainly at 1 kHz ).
>
> I think that's the old stuff or maybe APs somewhat conservative specs. I'm
> told that the new stuff is of the same order of a LynxTWO, whose test
> results I published at http://www.pcavtech.com/soundcards/LynxTWO/index.htm
> . It shows up to 115 SNAD with a 20-20K measurement bandwidth, and 107 dB at
> comparable bandwidths to an AP S2.

Yup, it's typical figures for System One or Portable One. It's seems remarkable
now just how long they've been around.


Graham

Archived from groups: rec.audio.pro (More info?)

Phil Allison wrote:

>"Michael R. Kesti"
>
>> Specifications are never measurments.
>
> ** Rubbish.

How CAN one argue with logic such as that?

>> Instead, specifications are chosen
>> values of parameters that, when measured, are promised to be no worse than
>> the values specified.
>
> ** Shame about all those "min", "typical" and "max" figures in data
>sheets then.

I downloaded the specifications of the three mixers referenced in this
thread's base note, and not one of them provided "min", "typical", and
"max" parameter values. There were plenty of occasions of "greater than"
and "less than" for values of distortion, noise, and such parameters, and
untoleranced values of impedance, max levels, and the like. Perhaps you
would be so kind as to supply a link to a spec of a pro audio product that
includes min, typical, and max parameter values.

>When chosing those values, manufacturers are walking
>> a line between how good they want their gear to appear on paper and how
>> many manufacturing rejects and/or customer returns they are willing to
>> tolerate.
>
> ** Most equipment specs represent typical figures found by measurement on
>samples - unless otherwise specified.

If this is true, then about half of the delivered units are going to
perform worse than those figures. Would you find it acceptible to
discover that you had purchased a unit that measured worse than its
published specs?

--
========================================================================
Michael Kesti | "And like, one and one don't make
| two, one and one make one."
mkesti@gv.net | - The Who, Bargain

Archived from groups: rec.audio.pro (More info?)

"Michael R. Kesti"
> Phil Allison wrote:
>
> >"Michael R. Kesti"
> >
> >> Specifications are never measurments.
> >
> > ** Rubbish.
>
> How CAN one argue with logic such as that?
>

** You posted no proof of an wild claim.

I should have said **BULLSHIT** !!!


> >> Instead, specifications are chosen
> >> values of parameters that, when measured, are promised to be no worse
than
> >> the values specified.
> >
> > ** Shame about all those "min", "typical" and "max" figures in data
> >sheets then.
>
> Perhaps you
> would be so kind as to supply a link to a spec of a pro audio product that
> includes min, typical, and max parameter values.


** You said: " Specifications are never measurments."


> >
> > ** Most equipment specs represent typical figures found by measurement
on
> >samples - unless otherwise specified.
>
> If this is true, then about half of the delivered units are going to
> perform worse than those figures.


** But only by trivial amounts.


> Would you find it acceptible to
> discover that you had purchased a unit that measured worse than its
> published specs?
>


** Yep - when the specs are all **way above* what is needed to do the job.

But this has nothing to do with what maker's specs tell you.



............ Phil

Archived from groups: rec.audio.pro (More info?)

In article <znr1093262843k@trad>, Mike Rivers <mrivers@d-and-d.com> wrote:
>In article <41296A84.67BD3C85@gv.net> mkesti@gv.net writes:
>
>> > ** Shame about all those "min", "typical" and "max" figures in data
>> >sheets then.
>>
>> I downloaded the specifications of the three mixers referenced in this
>> thread's base note, and not one of them provided "min", "typical", and
>> "max" parameter values.
>
>In typical Phool style, the subject has been changed from "mixers"
>(the final product) to "components" (the little things inside the
>product). He's just messing with you. Pay him no mind. He won't go
>away.

Hell, some of the Chinese component manufacturers don't even have "min,"
and "max" figures, just "typical" ones and some of those have to be taken
with a grain of salt too.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

Tim Perry <timperryspammenot@adelphia.net> wrote:
>
>having lived through an era where 125 W/ch car stereo amps were often sold
>with 2 amp fuses to the 13.8 volt inputs i sometimes get a bit skeptical
>when specs seem too good to be true.

Through it? I don't think that era is over yet. Except perhaps in that
they are now sold as 500 W/ch amps....

>so if i had it to phrase over again i think i would say: i wonder if there
>is some way to derive or extrapolate a resonably accurate measurement of THD
>with such poor and substandard test gear as i have managed to aquire. (i
>suspect the answer is no way in heck, but one can hope)

It is easy to measure THD at high levels. And at low levels, measuring THD
isn't very useful.

And if you want to buy an HP 334B distortion test set, I have one in need
of some repair work that I am considering putting up on Ebay.

>i guess its back to subjective evaluation for now

That's what it all comes down to in the long run to some extent. THD
is handy for comparing similar systems, though. The distortion meter
is great for finding maximum output levels on tapes, for instance.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Archived from groups: rec.audio.pro (More info?)

"Tim Perry" <timperryspammenot@adelphia.net> wrote in message
news:_eOdnbLeYo7mEbfcRVn-iA@adelphia.com...

> so if i had it to phrase over again i think i would say: i wonder if there
> is some way to derive or extrapolate a resonably accurate measurement of
THD
> with such poor and substandard test gear as i have managed to aquire. (i
> suspect the answer is no way in heck, but one can hope)

The good news is that it's possible to derive quite a good measurement of
THD using a relatively affordable computer soundcard such as an M-Audio
Delta or a CardDeluxe (look on e-bay; they show up all the time). The bad
news is that, once you've done the THD measurement, you still don't know
squat about how good the amplifier might or might not sound, because THD
correlates damned poorly with the latter unless you use it to find grossly
defective amplifiers. But the further good news is that you can use the
soundcard to make some tests that are actually relevant, looking at the
actual harmonic spectrum of the distortion produced by a single frequency,
or doing intermodulation distortion measurements of various sorts.

Peace,
Paul