Old 06-11-2019, 08:58 PM   #1
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default Software for testing Mic Pres

I'm gathering piles of mic pres in order to do some actual real world, quantified, not nonsense numbers to see just exactly how different these things are and especially to look at so many mythical or near mythical claims

I have been trying Rightmark Audio Analyzer, Plugin Doctor and Room EQ Wizard

Noise and frequency response measurements are easy enough in all of these programs, but distortion has been tricky

All three have THD analyzers, but what I really want to see is distortion vs level on these. It seems like all three just send a static level to check. Plugin Doctor seems to do it at 0dbfs as well which makes it tricky



Any suggestions on how I measure the distortion? The claim so often is that you can magically know at all times the level that is coming in and then you can "push" the mic preamp hard and reveal all this magic "character"

I really like the way this distortion chart goes, but I dont know which software it is
Attached Images
File Type: jpg distortion tests.jpg (62.1 KB, 432 views)
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-11-2019, 11:12 PM   #2
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

Quote:
Originally Posted by pipelineaudio View Post
Any suggestions on how I measure the distortion?
Yes, run a sine wave through it and the output into spectrum analyzer. Run it hotter and hotter, at some point harmonics will appear on the FFT, that's your distortion, those harmonics - that's why they call it "harmonic distortion". That's where/how that spec is derived when it is placed on gear such as ~n% harmonic distortion. It's the exact same concept I was 'splanin in the snake oil thread.
__________________
If it requires a null test to find it, it is by definition minuscule.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 12:13 AM   #3
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

I am hoping for software that can make a graph to capture where in the gain the distortion starts. The way in the picture is awesome, i just dont know what software that is.
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 12:14 AM   #4
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

whats a good spectrum analyzer for that by the way? SPAN can be goofy to me
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 03:19 AM   #5
cyrano
Human being with feelings
 
cyrano's Avatar
 
Join Date: Jun 2011
Location: Belgium
Posts: 4,587
Default

If you're serious about this, you also need a millivolt meter, besides software. That's for measuring gain. And an XLR with a 200 Ohm resistor between pins 2 and 3, for noise measurements.

A reference preamp also comes in handy.

REW should have everything you need. There's also ARTA. Not free, not JAVA. And Rightmark:

http://audio.rightmark.org/index_new.shtml/
__________________
“It has become appallingly obvious that our technology has exceeded our humanity” Albert Einstein
cyrano is online now   Reply With Quote
Old 06-12-2019, 08:44 AM   #6
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

If you use a triangle wave instead of a sine, the resulting wave basically shows you the curve of the distortion. It’ll get skewed some by any filters in the path, but with supposedly flat preamps, it should show you...something...
ashcat_lt is online now   Reply With Quote
Old 06-12-2019, 09:07 AM   #7
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

You can just use built in JS stuff to get a feel for what changing a waveform does to harmonics. Here I'm using the JS Tone Generator > JS Distortion > JS Analyzer:



I just think it's good to get one's head wrapped around what changing a simple waveform does. THEN start running real stuff through it.
__________________
If it requires a null test to find it, it is by definition minuscule.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 09:23 AM   #8
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

But what the OP actually asked for can be achieved with a triangle source and just recording in Reaper.

That one looks a little kinky, but if you zoom in a little, it gets a lot smoother.
(this time with a lot more distortion)
ashcat_lt is online now   Reply With Quote
Old 06-12-2019, 10:44 AM   #9
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

Anyone is free to disagree with me but they'd be wrong (just kidding) - more seriously, I think it is important to at least watch pure sine wave behavior and how clipping/shaping them creates harmonics, just sayin' I don't care what the ask is in that regard because it's something worth understanding first and foremost.

I picked sine because it is a basic building block with zero harmonics, and if he cares about what preamps impart, the first thing he should do is run a sine through one, turn it up until he just starts seeing harmonics, then decide when he actually starts hearing them and so on. I'm seriously considering doing a YT tutorial on sine waves all the way down to strapping a pencil to a transducer to demonstrate how it can draw a sine wave coming from a DAW.
__________________
If it requires a null test to find it, it is by definition minuscule.

Last edited by karbomusic; 06-12-2019 at 10:49 AM.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 11:12 AM   #10
JamesPeters
Human being with feelings
 
JamesPeters's Avatar
 
Join Date: Aug 2011
Location: Near a big lake
Posts: 2,667
Default

"Saike Spectral Analyzer" (available in ReaPack) is a nice spectral analyzer with lots of features.

You'll also want to use "Oscilloscope Meter" (JS plugin included in Reaper).

You can do both with the VST plugin "Signalizer", and its oscilloscope meter is nicer. I'd still be using it, but the Linux version doesn't work (currently). You use Windows though, so I'd recommend downloading that.

Signal generators (JS plugins included in Reaper) that you'll want to use:

Sine Sweep Generator
Tone Generator
White Noise Generator
Pink Noise Generator
FFT Noise Generator
__________________
http://petersamplification.com
Using REAPER for Linux
JamesPeters is offline   Reply With Quote
Old 06-12-2019, 12:43 PM   #11
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

I don't see how to do a ramp up in REW.

Frequency response is easy, we're covered. Noise is easy, we're covered, but finding out when the distortion starts to happen really needs a ramp like in the included picture.

One of the things I really really want to be looking at, is whther there even is a magic spot in the gain where things start to crunch up. Ladt night I was doing some tests, and specifically referenced some quotes about what people say about these particular preamps, and thru testing, found absolutely nothing of the sort, quite the opposite in fact.

I'd like to be able to show that as a graph, instead of a long, rambling video, so we can directly compare apples to apples

https://www.facebook.com/pipeline.au...?fref=mentions

But I guess, could I record some ramps and then maybe run the waveform in REW or something to get a graph?

I emailed DDMF to see if plugin doctor could be made to use something aside from 0dBFS

I have rightmark, but it doesnt have a ramping function that I can find.
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 12:50 PM   #12
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

Quote:
Originally Posted by pipelineaudio View Post
I don't see how to do a ramp up in REW.

but finding out when the distortion starts to happen really needs a ramp like in the included picture.
You can see exactly what you need the way I explained without this whole ramp picture thing - I use it all the time with analog circuits so I can document the specs and the very thing I want to know is what you want to know. I'll demonstrate this with a high-end preamp when I get home tonight and create you a video.

Yes, there are plenty of more advanced things to get into later as far as graphs and pictures and documenting but I really do feel this basic step 1 shouldn't be ignored for your own knowledge, you did say "I want to learn" but if the question is really "I just want these graphs" confirm and I'll stop bugging you.
__________________
If it requires a null test to find it, it is by definition minuscule.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 12:55 PM   #13
Judders
Human being with feelings
 
Join Date: Aug 2014
Posts: 8,696
Default

Quote:
Originally Posted by karbomusic View Post
I'm seriously considering doing a YT tutorial on sine waves all the way down to strapping a pencil to a transducer to demonstrate how it can draw a sine wave coming from a DAW.
OT: you should do that!
Judders is offline   Reply With Quote
Old 06-12-2019, 01:15 PM   #14
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

Quote:
Originally Posted by Judders View Post
OT: you should do that!
The only thing I'd have to build is the rig to move the paper (or the speaker). It's not that it has to be accurate, just enough to get the mental light bulb to go off about sine waves end-to-end.
__________________
If it requires a null test to find it, it is by definition minuscule.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 01:20 PM   #15
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Quote:
Originally Posted by karbomusic View Post
You can see exactly what you need the way I explained without this whole ramp picture thing - I use it all the time with analog circuits so I can document the specs and the very thing I want to know is what you want to know. I'll demonstrate this with a high-end preamp when I get home tonight and create you a video.
Thats how I did it in the video I linked. However, it doesn't lend itself to a small, simple graph that you can put right next to a small simple graph of another mic preamp, which is what my whole purpose is of doing this.

Like my round trip latency roundup chart....I want to have a place where people can go and actually be able to see and compare these things side by side

No more snake oil

No more mystery marketing

Just apples to apples graphs
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 01:24 PM   #16
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

I think I was just going off the ask in the other thread (below). Graph or no graph, I personally think it's cart before the horse to just blindly run tests and post graphs (because you would be debunking without really understanding any more than those you are debunking) but I certainly don't mind backing off bugging you about it.

Quote:
Originally Posted by pipelineaudio
I really dont understand it so I'd like to hear everything in the world about this! I can;t say enough how interested I am in it
__________________
If it requires a null test to find it, it is by definition minuscule.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 01:46 PM   #17
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

I think those ramp tests in the pics in the OP should tell quite a bit about any alleged nonlinearities dont you? I don't see the problem with that

For sure the frequency response charts would be nearly self explanatory, whats wrong with listing those side by side?

Noise isn't nearly that hard to measure or as murky as some would have you believe. Especially not at the hyperbolic claims of difference rampant in the forums

I don't know why apples to apples comparisons of these things would be a bad thing
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 01:50 PM   #18
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Because I and very nearly every single other person who has ever bought, tested, or even created, yes, most every plugin maker of these things would fall into this category, doesn't completely understand how the nonlinearities in guitar amps work means I can't understand enough to measure whether or not mic preamps are distorting seems quite a stretch.
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 02:19 PM   #19
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

I don't have a problem with any of ^that but I mistakenly thought you said you wanted to learn more which puts me OT at this point.

If you don't understand what any of the signals are actually doing or why they sound like they do when they are distorted at the basic level, isn't it just the blind leading the blind in favor of winning an argument, dispelling a myth or whatever you want to call it? Don't we have enough of that on the Internet already?

It's just my opinion though; I'm sure it's fine if you do those tests and post them.
__________________
If it requires a null test to find it, it is by definition minuscule.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 02:28 PM   #20
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Quote:
Originally Posted by karbomusic View Post
I don't have a problem with any of ^that but I mistakenly thought you said you wanted to learn more which puts me OT at this point.

If you don't understand what any of the signals are actually doing or why they sound like they do when they are distorted at the basic level, isn't it just the blind leading the blind in favor of winning an argument, dispelling a myth or whatever you want to call it? Don't we have enough of that on the Internet already?

It's just my opinion though; I'm sure it's fine if you do those tests and post them.
I think you were reading way more into me wanting to learn more about the modelling of the nonlinearities of guitar processors (which seems quite a mystery even among our very best DSP gurus in the industry, as you can watch them argue about it all day long) than is in any way relevant to this particular topic of measuring mic pres to give an apples to apples chart
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 02:36 PM   #21
karbomusic
Human being with feelings
 
karbomusic's Avatar
 
Join Date: May 2009
Posts: 24,755
Default

Quote:
Originally Posted by pipelineaudio View Post
I think you were reading way more into me wanting to learn more about the modelling of the nonlinearities of guitar processors (which seems quite a mystery even among our very best DSP gurus in the industry, as you can watch them argue about it all day long) than is in any way relevant to this particular topic of measuring mic pres to give an apples to apples chart
I'll say much of that non-lineararites mystery is pure bullshit - the music industry thrives on black boxes and so called mystery, it always has... but that's the exact reason I wanted you experimenting. It's fine, I'm not offended or bothered whatsoever with what you want to accomplish and best of luck getting it posted.
__________________
If it requires a null test to find it, it is by definition minuscule.
karbomusic is online now   Reply With Quote
Old 06-12-2019, 02:53 PM   #22
JamesPeters
Human being with feelings
 
JamesPeters's Avatar
 
Join Date: Aug 2011
Location: Near a big lake
Posts: 2,667
Default

The issues with trying to call out something like this as "snake oil" are:

1) Everything distorts your source signal. Any change is a distortion. Plus what a person will appreciate for distortion will be different for different situations, and a matter of personal taste. You've probably heard dozens of people saying that differences in A/D and D/A converters these days don't matter, but sometimes they do, even something relatively subtle like that.

2) Measuring it means knowing what to measure. We look at 2D graphs to represent 3D things, "frozen in time" at that. So then we have to extrapolate what that means based on our understanding of the data. You'd be hard pressed to find anyone who can look at some graphs and say "I know what that preamp sounds like".

3) There are different circumstances under which the hardware is used, such that doing tests is that much more problematic. I've heard comparisons of preamps recording the same source (with variables eliminated as much as possible) and thought "these all sound virtually identical", but when I've tried the preamps I could hear differences right away. So some of it is about how you use the gear. Good luck getting that on a graph, in a way that makes intuitive sense to anyone.

You owe it to yourself to try some different preamps, converters and so on. My takeaway: some of it matters to me, for how I work. So I focus on that. I can also go "bargain basement" on recording gear and know exactly what I'm sacrificing (usually not enough that it would stop me from getting a good recording for my own standards). I also know that I could do tests on my preamps for comparison (to some cheap ones) and most people wouldn't think the "better" preamps would sound any different or better based on those tests. See point #2.

If it were so easy to just "put it all on paper for everyone to see", it probably would've been done by now. You can do it if you like, but I suspect the results won't seem worthwhile to you.
__________________
http://petersamplification.com
Using REAPER for Linux
JamesPeters is offline   Reply With Quote
Old 06-12-2019, 04:06 PM   #23
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

A lot of this came about, because as some of you surely remember, I had piles of ALL the mic preamps everyone could name, between Vintage Recorders and Studio Z. Except on some pathological stuff, nobody, not any of the people who constantly claimed these HUGE world ending differences, could reliably pick one mic preamp from another, nor could they even tell if the preamp had been changed or if they were listening to the exact same file back to back, when these things were operated in their nominal range.

So now I'm being taken to task that "ITS SO TOTALLY OBVIOUS ANYONE CAN HEAR IT OMGZORZ !!!!!!!!" they are somehow super drastically different when pushed a bit. Thats a lot of what I want to measure


But if I can also document the frequency response as well (as again, this is where HUGE world shattering claims of differences are also made), then that is a bonus. And noise

Noise is a biggie

Potentially, this one if bad enough, should be noticeable in realistic conditions, but that's a big if
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 04:57 PM   #24
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Why are there so many Strawmen being thrown at me?

Is my Round Trip Latency Chart somehow biased or not objective?

Do I have a track record of doing these things wrong?

Do I have a track record of trying to prove a preconceived notion instead of just finding the truth and then just figuring its easier to deal with reality on reality's terms?

I really don't know where any of this is coming from

Go ahead and try to google for an objective set of measurments on mic preamps. If you find it, let me know and I wont bother

I don't know why people are so against objective information
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 05:33 PM   #25
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

Can I say this again?

When the source is a triangle (linear ramp, sawtooth wave works too) then the output wave IS the graph. Run triangle (or saw) through thing, record, look at waveform. As long as thing isn’t messing too much with frequency response, the shape of the nonlinearity is right frickin there. If it is messing with the frequency response significantly, then it’s really a lot harder, and probably less meaningful.
ashcat_lt is online now   Reply With Quote
Old 06-12-2019, 05:45 PM   #26
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Could you make an example wave file? I don't know how this would do the volume ramp part, but if it does it would greatly simplify things!
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 05:50 PM   #27
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

Quote:
Originally Posted by pipelineaudio View Post
Could you make an example wave file? I don't know how this would do the volume ramp part, but if it does it would greatly simplify things!
What? Did you see my pictures above? JS Tone Generator makes triangles if you ask it to.
Quote:
Originally Posted by JamesPeters View Post
so you can find whatever threshold for distortion you're after (and how much it changes when pushed beyond).
I'm sorry, I think you missed the point also. You can line up the two waveforms, maybe normalize them to take out the gain portion of the nonlinearity, and then the threshold and what happens beyond is just there. Pick an individual sample. An input of that voltage creates an output of this voltage. It IS the graph of the curve!

Last edited by ashcat_lt; 06-12-2019 at 05:55 PM.
ashcat_lt is online now   Reply With Quote
Old 06-12-2019, 06:28 PM   #28
JamesPeters
Human being with feelings
 
JamesPeters's Avatar
 
Join Date: Aug 2011
Location: Near a big lake
Posts: 2,667
Default

Quote:
Originally Posted by ashcat_lt View Post
I'm sorry, I think you missed the point also.
If you're talking about using test signals which are more complex than what a tone generator can do, I think it's worthwhile. However if you're talking about using a basic test tone from a signal generator plugin, you can view that on an oscilloscope and then you can turn the preamp knobs in realtime to see what happens to the signal. You can run 2 instances of the scope, or use 2 channels of the scope. The result should be what you're describing.

Maybe we're talking past each other somehow.
__________________
http://petersamplification.com
Using REAPER for Linux
JamesPeters is offline   Reply With Quote
Old 06-12-2019, 06:32 PM   #29
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

Quote:
Originally Posted by JamesPeters View Post
Maybe we're talking past each other somehow.
We might be.

As long as the gain knob does nothing but gain, and you adjust it to where it really hits the absolute limit, you can see every point between silence and the rail.

Edit - I guess I don't care if you use an oscilloscope or record or whatever. The real point being that a sine wave has a curve of its own, and to get the actual curve of the non-linearity out of it, you have to do some interpolation. If the source is a triangle or saw, the curve you see on the output is exactly that of the non-linearity.
ashcat_lt is online now   Reply With Quote
Old 06-12-2019, 08:57 PM   #30
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

The triangle would just show the distortion at one level if I do it the way you showed in those pictures, What I would like is a graph that shows distortion vs input level.
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 08:57 PM   #31
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Quote:
Originally Posted by ashcat_lt View Post
As long as the gain knob does nothing but gain, and you adjust it to where it really hits the absolute limit, you can see every point between silence and the rail.
That's one of the claims I'm trying to test though
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 09:42 PM   #32
cyrano
Human being with feelings
 
cyrano's Avatar
 
Join Date: Jun 2011
Location: Belgium
Posts: 4,587
Default

Shouldn't you be measuring gain then?
__________________
“It has become appallingly obvious that our technology has exceeded our humanity” Albert Einstein
cyrano is online now   Reply With Quote
Old 06-12-2019, 10:13 PM   #33
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Yes, gain vs distortion
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 10:23 PM   #34
cyrano
Human being with feelings
 
cyrano's Avatar
 
Join Date: Jun 2011
Location: Belgium
Posts: 4,587
Default

How do you count on measuring gain?

I mean, it's not as if your ADDA is calibrated, is it?
__________________
“It has become appallingly obvious that our technology has exceeded our humanity” Albert Einstein
cyrano is online now   Reply With Quote
Old 06-12-2019, 10:31 PM   #35
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Ok this has gone so far affield now.

Does anyone know software that will plot THD or THD+noise vs level?
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 10:40 PM   #36
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

This...

...shows what happens at any given signal level between silence and 0dbFS.

This...

...looks a little weird. I lowered the threshold instead of input gain, but then I added an arbitray and incorrect amount of makeup gain to make it even visible in this picture. if it was your project, you could zoom in, but this was obviously a mistake.

If I do this...

You can pretty clearly see that near the zero crossing, it is not really a 1:1 correlation. The gain causes the output to get to and around the curvy part and then hit the limit really fast. That's not the display clipping off, it's ReaComp.*

OTOH, if I do this...

The linear portion of the "circuit" (near the zero crossing) does map 1:1 visually with the original input. It still hits the curve and limit just as fast.

Which do you prefer?

One could (assuming any of the gear we use was DC coupled, which it probably isn't) put in a series of DC voltages to the input and read the DC voltages that come out. It doesn't matter actually if the circuit multiplies (adds gain to) that DC voltage or the DC voltage is just bigger to begin with. By the time it reaches the actual non-linearity, that DC input will have a given level, and will produce some DC output. One could measure a number of different points between 0V and wherever the output stops getting bigger in order to make a graph. As the number of those points approaches infinity, it starts to just be easier and faster to run a triangle wave through it.


Edit/PS - If I use a sine wave instead...

...well, there's less gain so that I can make the point, but the input is already curvy, so how can I tell what part of the curve is the original and what part is ReaComp?

I definitely understand that you need to use a pure sine if you want to do the spectrum analysis route to see which harmonics are "generated", but if what you want is something like this...

...then the input should be triangle or saw.


*Actually, I did manage to crop out the very top of the picture of track 1's waveform, if I'd scrolled up just one more click... I'm not shooting it again.

Last edited by ashcat_lt; 06-12-2019 at 11:02 PM.
ashcat_lt is online now   Reply With Quote
Old 06-12-2019, 10:54 PM   #37
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

You know, this might actually be something cool to include.

I am hoping for quantifiable numbers like 1% THD at -3dBFS type of chart thing, but let me think about whether this would work instead
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-12-2019, 10:56 PM   #38
pipelineaudio
Mortal
 
pipelineaudio's Avatar
 
Join Date: Jan 2006
Location: Wickenburg, Arizona
Posts: 13,444
Default

Something like this
__________________
REAPER Shirts are Back! - https://shop.spreadshirt.com/pipelineaudio/
pipelineaudio is offline   Reply With Quote
Old 06-13-2019, 09:31 AM   #39
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

Ah! So like this then?

I understand that Reaper doesn't give us the fancy grid lines, but it ultimately tells me everything I need to know. This would be a simple JSFX to write if I had a clue about graphics in JS.
ashcat_lt is online now   Reply With Quote
Old 06-13-2019, 09:39 AM   #40
ashcat_lt
Human being with feelings
 
Join Date: Dec 2012
Posts: 4,219
Default

Quote:
Originally Posted by karbomusic View Post
The only thing I'd have to build is the rig to move the paper (or the speaker). It's not that it has to be accurate, just enough to get the mental light bulb to go off about sine waves end-to-end.
Do it right at the woofer and use a really low frequency. All this you kind of have to do anyway, since you can only move the paper so fast. Has the added bonus of busting the myth that low frequencies need space to develop.
ashcat_lt is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 05:53 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.