| Author |
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Porky
Guest
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 Posted:
Tue Nov 08, 2005 5:42 am Post subject:
Re: mic preamps |
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"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:jMidnSU8dvQK0_LeRVn-jw@comcast.com...
| Quote: | "hank alrich" <walkinay@thegrid.net> wrote in message
news:1h5mkr1.1sl9fvz1wwusouN%walkinay@thegrid.net
It's probably also an interesting measurement task.
Conceptually, it seems like it is not that much different from measuring
speakers and amps. The permissable voltage levels are down by a few orders
of magnitude, and the actual impdances are up by similar amounts.
How would we measure that interaction?
A mic and a preamp are just halves of an electrical network. Putting the
two halves together is something like a third year undergraduate
electrical circuits problem.
Once you have measured the impedance curves for the mics and the preamps,
the next logical step would be to calculate a joint transfer function. ]
Then, someone needs to step into the lab and do some measurements to
verify the theoretical results.
Once the model of interaction is verified, then preamps could be mixed and
matched pretty freely using the verified theoretical model.
With condenser mics, which have built-in pre's, the output impedance should |
be almost totally resistive. Dynamic mics, on the other hand would be more
complex. Preamps with direct coupled inputs would also be almost purely
resistive, while those with capacitor coupled inputs would have a reactive
component.
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Porky
Guest
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| Posted:
Tue Nov 08, 2005 5:42 am Post subject:
Re: mic preamps |
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"CWCunningham" <charlesw-at-blackfoot.net> wrote in message
news:dkjvjh02kc1@enews2.newsguy.com...
| Quote: | "Paul Stamler" <pstamlerhell@pobox.com> wrote in message
news:cy7bf.43468$zb5.25798@bgtnsc04-news.ops.worldnet.att.net...
| The problem with this is that part of the difference preamps make is
that
| they make microphones behave differently, depending on what sort of load
| they present to the microphone. That's why it's necessary to test
mic-preamp
| systems, rather than preamps alone.
|
Well I guess you have to make a choice.
You either want to test a preamp, - or -
You want to test the combination of a mic and a preamp.
If you choose the former, then a quality circuit could be built to put the
preamp through it's paces, reliably and repeatably.
If you choose the latter,
How many different microphones will it take to create a valid test.
What about the room? That's part of a "real world test" as well.
If so, how many permutations of mics and rooms will suffice?
It depends on what you want I suppose, if you want an objective test of a
mic
pre, you can do it, but if you imagine it requires a microphone, then you
can't
do it. You just have to make a choice.
--
Therin is the whole ball of wax. One must use a mic/preamp combination, |
and it's the combination of mic and preamp that we must evaluate to decide
it it's right for our purposes. One mic might sound beautiful with a given
preamp, while another mic might suck with the same preamp. Evaluating every
possible mic/preamp combination would be virtually impossible because new
mics and preamps would be coming out faster than the combinations could be
evaluated.
The only practical solution is for each person to evaluate preamps with
the mic(s) they will be using. My friend has a Lawson L47 mic with a UA LA
610 pre, and it is one of the best sounding setups I've ever heard. It works
well with a wide range of vocalists, so it isn't user-centric like many
mic/pre combos are. |
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Porky
Guest
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| Posted:
Tue Nov 08, 2005 5:42 am Post subject:
Re: mic preamps |
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"Arny Krueger" <arnyk@hotpop.com> wrote in message
news:17OdnRMtdrIbV_DeRVn-ug@comcast.com...
| Quote: | "Porky" <noham@nospam.com> wrote in message
news:7xebf.677$kd.71@bignews4.bellsouth.net
One would think that instrumentation could differentiate
between component responses, but I've seen various
equipment with virtually identical specs but totally
different audible sonic characteristics, as I'm sure most
of us have.
Some of that is due to specs that are actually audibly broader than they
might seem.
For example, if I get to specify where the in-spec response variations
are, you *will* hear the difference between two pieces of equipment that
are speced at 20-20 KHz +/- 1 dB. A piece of equipment with 1 dB
octave-wide dip at 1 KHz can easily sound different than a piece of
equipment with a 1 dB peak at the same frequency. But, both will be
arguably 20-20 KHz +/- 1 dB.
Agreed, and it shows that standard specs simply aren't adequate to the task |
of predicting how a given piece of equipment will sound. Those standars
specs are used because very few folks would know what the needed specs
meant. Understanding them would require more training than 99% of listeners
would be willing to invest just to know what those specs meant. Better just
to listen and decide for oneself which sounds better. |
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Bob Cain
Guest
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| Posted:
Tue Nov 08, 2005 5:42 am Post subject:
Re: mic preamps |
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Paul Stamler wrote:
| Quote: | Okay, let's think about this. If you wanted to completely characterize the
input impedance of a microphone preamp, how would you go about it? In
particular, how would you measure the phase characteristics? Amplitude
should be relatively easy.
|
If the stimulus is a sweep and the measuring instrument is a full band
characterized and calibrated A/D then the data recorded by measuring
current through a series resistor and voltage across the pre, along with
the instrument calibration data are sufficient to calculate the complex
input impedance of the pre.
Using a sweep instead of an MLS sequence eliminates the effects of a
typically small amount of non-linear distortion.
Bob
--
"Things should be described as simply as possible, but no simpler."
A. Einstein |
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Porky
Guest
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| Posted:
Tue Nov 08, 2005 5:42 am Post subject:
Re: TWO MORE MIXER CHOICES (Soundcraft and NADY) any good? |
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"WillStG" <willstg@aol.com> wrote in message
news:1131264012.397564.155090@f14g2000cwb.googlegroups.com...
| Quote: | normanstrong@comcast.net wrote:
Yes, I really think that none of people "here" could tell the difference
between the expensive setup you mentioned above v. the same setup with
the
cheap Yamaha mixer substituted for the expensive Grace or Hardy mike
preamps.
Your trolling disdain for people who do this for a living aside,
I have basically agreed that, given a very limited and unchallenging
source material, or with other things in the signal chain that mask or
diminish the micpre's character, or with poor monitoring this may be
the case. But what I want to know is, how have *you* tested and
challenged the performance capabilties of this $100 Yamaha mixer that
it has so convinced you it is the equal of $1000 micpres as you so
doggedly would claim?
Somehow I suspect you have little idea what kind of challenges
the real world might present to a piece of gear at all, and that what
you lack in practical experience you are seeking to make up for with
hubris.
And yes, I really do believe that people spend 10-20x more on preamps
just
to impress clients.
"_Just_ to impress clients"? No, but large studio's do really
wish to meet their client's Professional expectations.
I doubt guys like Tom Lord Alge or Mutt Lange are much
"impressed" by the Neumann, Manley or Neve brand name. But they do
want to work on familiar, good sounding gear that meets a certain
professional standard of performance. It makes the job easier and
faster to accomplish, and time is money you know.....
|
Exactly right. There are certain name brands that you will see in every
professional studio, and folks do expect to see those brands there, but they
aren't there because folks expect to see them, they're there because they
have proven themselves time after time, in studio after studio, under a wide
range of conditions. Mutt Lange doesn't give a damn what name is on a piece
of equipment as long as it performs like he wants it to, but he will grab
one of those big name brands off the shelf, because he knows exactly how it
will perform. |
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Paul Stamler
Guest
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| Posted:
Wed Nov 09, 2005 12:28 am Post subject:
Re: mic preamps |
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"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:dkpkv401qh8@enews4.newsguy.com...
| Quote: |
Paul Stamler wrote:
Yesh, that's where I'm trending too. The complicating thing is to do all
that without screwing up the preamp's operation by screwing up the
grounding.
You need to do the measurements full differential so maybe that would
ameliorate the grounding issue.
And not loading the microphone further while we measure the
voltage across the preamp input.
I'm suggesting that the impedance measurements of the pres and that of
the mics be done independently. They can then be computationally
combined in a pairwise fashion to guage the real significance of this
matching issue in technical rather than subjective terms.
|
Sorry, brain fart. I'm agreeing, basically looking at characterizing the
input impedance of the preamps. But the problem of keeping the preamps from
misbehaving may still be tough.
Peace,
Paul |
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Jim Carr
Guest
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| Posted:
Wed Nov 09, 2005 5:42 am Post subject:
Re: mic preamps |
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"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:dkplb30245l@enews3.newsguy.com...
| Quote: | It's about isolating factors. In the case of impedance interaction, it
can be done just fine without dealing with the issues of a reproducible
and adequate acoustic stimuli.
|
I don't understand why it's about isolating factors. I thought it was about
audio, not math. |
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Porky
Guest
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| Posted:
Wed Nov 09, 2005 5:42 am Post subject:
Re: mic preamps |
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"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:dkplb30245l@enews3.newsguy.com...
| Quote: |
Jim Carr wrote:
"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:dkp9jf02uvn@enews2.newsguy.com...
Using a sweep instead of an MLS sequence eliminates the effects of a
typically small amount of non-linear distortion.
And I still sit here and wonder why nobody has an audio clip that says,
"Here, listen. See much better this one sounds than that one?"
It's about isolating factors. In the case of impedance interaction, it
can be done just fine without dealing with the issues of a reproducible
and adequate acoustic stimuli.
The problem with doing all these measurements is that mic preamps are |
anything but flat, they all color the sound, as do microphones, and the
trick is to choose the mic/preamp combination that will sound the best. All
the preamp measurements in the world aren't going to do any good unless you
also have the exact characteristics of all the microphones that might be
used with any given preamp. Even then, you'll also need all possible typical
room characteristics and how they will interact with any given combination.
There are probably several ways to measure preamp response accurately
under given conditions, but the real problem is trying to figure out how it
will relate to a given mic in a given room. Antares makes a plugin that
models most popular mics, and does so fairly well. One might also be able to
make digital models of popular preamps and create a plugin that allows one
to try out various combos to see how they might sound, but it would still be
a very rough approximation at best.
I'm afraid that at present, auditioning preamps with the mic one will be
using is still the best way to choose a preamp. |
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Bob Cain
Guest
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| Posted:
Thu Nov 10, 2005 5:42 am Post subject:
Re: mic preamps - Response to Gary Sokolich |
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the_professor@hotmail.com wrote:
[his usual]
the_professor is Gary Sokolich. Gary follows me around to all the
groups where I post to stalk and sniff my ass. He can't seem to get
enough of it. The answer is still _no_, Gary. I'm not into that.
Bob
--
"Things should be described as simply as possible, but no simpler."
A. Einstein |
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Agent 86
Guest
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| Posted:
Thu Nov 10, 2005 5:42 am Post subject:
Re: mic preamps |
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On Thu, 10 Nov 2005 02:04:56 +0000, the_professor wrote:
eat shit gary. |
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Guest
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| Posted:
Thu Nov 10, 2005 5:42 am Post subject:
Re: mic preamps |
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Bob Cain <arcane@arcanemethods.com> wrote in
news:dksabb0i00@enews2.newsguy.com:
snip....snip
| Quote: | My background is science, engineering and physics.
|
snip...snip
My background is science, engineering and physics, and you are a lying,
hypocritical and technically-inept fraud.
This thread is just another amusing example of the same sort of mindless,
nonsensical discussion that took place among the same three "audio" stooges
last year regarding the existence/non-existence of so-called Doppler
distortion. Obviously, birds of a feather...... |
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Porky
Guest
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| Posted:
Thu Nov 10, 2005 5:42 am Post subject:
Re: mic preamps |
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<the_professor@hotmail.com> wrote in message
news:cVxcf.225446$mQ3.134927@fe02.news.easynews.com...
| Quote: | Bob Cain <arcane@arcanemethods.com> wrote in
news:dksabb0i00@enews2.newsguy.com:
snip....snip
My background is science, engineering and physics.
snip...snip
Bob
My background is science, engineering and physics, and you are a lying,
hypocritical and technically-inept fraud.
This thread is just another amusing example of the same sort of mindless,
nonsensical discussion that took place among the same three "audio"
stooges
last year regarding the existence/non-existence of so-called Doppler
distortion. Obviously, birds of a feather......
|
Bang! I just killfiled another ghost! |
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Arny Krueger
Guest
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| Posted:
Thu Nov 10, 2005 10:27 pm Post subject:
Re: mic preamps (was: TWO MORE MIXER CHOICES (Soundcraft and |
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"Paul Stamler" <pstamlerhell@pobox.com> wrote in message
news:ktNbf.31576$qk4.24838@bgtnsc05-news.ops.worldnet.att.net
| Quote: | Okay, let's think about this. If you wanted to completely
characterize the input impedance of a microphone preamp,
how would you go about it?
|
Start out with the method I used for measuring amps and
speakers, with the impdances scaled up.
I might end up using mic preamps as the sensing elements
instead of using the line inputs of a sound card.
Balanced inputs are key to this procedure.
The basic measurement is a transfer-function measurement so
the response of the sensing mechanisms is immaterial as long
as it is not too horrible. IOW +/- 3 dB response would be
fine, but +/- 20 dB response would probably not be fine.
| Quote: | In particular, how would you measure the phase
characteristics? Amplitude should be
relatively easy.
|
One I got things calibrated, I would just take a screen shot
of a transfer function measurement in Spectra Lab.
Please see
http://www.pcavtech.com/pwramp/macrot-5000VZ/index.htm#SR_001S
http://www.pcavtech.com/pwramp/mag%20left_hi.gif
http://www.pcavtech.com/pwramp/phase_left.gif
for examples. |
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Arny Krueger
Guest
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| Posted:
Thu Nov 10, 2005 10:30 pm Post subject:
Re: mic preamps |
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"Jim Carr" <jim@azwebpages.com> wrote in message
news:0UWbf.3409$zu6.2970@fed1read04
| Quote: | "Bob Cain" <arcane@arcanemethods.com> wrote in message
news:dkp9jf02uvn@enews2.newsguy.com...
Using a sweep instead of an MLS sequence eliminates the
effects of a typically small amount of non-linear
distortion.
And I still sit here and wonder why nobody has an audio
clip that says, "Here, listen. See much better this one
sounds than that one?"
|
For one thing, just one clip proves nothing. Generally
auditioning is or at least should be more complex than that. |
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Arny Krueger
Guest
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| Posted:
Thu Nov 10, 2005 10:36 pm Post subject:
Re: mic preamps (was: TWO MORE MIXER CHOICES (Soundcraft and |
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"CWCunningham" <charlesw-at-blackfoot.net> wrote in message
news:dkggpp02rr3@enews4.newsguy.com
| Quote: | I expect a proper double blind test is easily done, but
extremely expensive.
|
Have you ever visited www.pcabx.com?
The actual out-of-pocket expense for the whole site was next
to zero - lots of borrowed stuff, and stuff I had laying
around.
However, building that site arguably got me into resuming an
old interest in recording live performances, and that hasn't
been cheap at all! ;-) |
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