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Streaming output way too hot

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Streaming output way too hot

Postby Watchmaker » Wed Sep 16, 2020 2:09 pm

This may be the wrong forum but I need help with a software level problem. Basically, streams from the internet using players without volume controls results in a signal far too hot going through my playback system. (27"iMac, late 2013, Catalina, Safari). Over explanation follows:

I usually avoid podcasts but, because Mike Senior is so cool, I thought I'd try to listen to his latest https://www.soundonsound.com/techniques/improving-your-mixes-distortion-podcast. Unfortunately SOS's player does not have a volume control and it's rendering the product unusable. (Ironically enough, it's distorted beyond listenability).

I have calibrated my reference levels (see: https://www.soundonsound.com/techniques/establishing-project-studio-reference-monitoring-levels) and am very comfortable with the results such that both my interfaces will read -20dbFS out and my monitor controller reads 0db. This aligns green/yellow/red metering in the digital and analogue parts of my monitoring chain.

Output meters on both a Focusrite 8PreX and and a UAD Apollo 8 show that all headroom has been removed from the audit stream appears brickwalled at -3dbfs. However, this occurs outside on my nice DAW matched reference level and -3dbFs at the interface output induces regular clipping (>+18) at the monitor controller (Audient Nero).

I'm assuming the digital stream is passed directly to the device's DA convertors, yes? If true, I'm unaware of any means to manage this part of the signal path. How can I regulate the amplitude in this layer? I'm not quite at a level where I can fiddle with APIs, Mac Audio Device manager does not allow me to control the interfaces from that UI, and neither Focusrite Control nor UAD Console allow me to adjust the software input.

Perhaps there is a simple variable I'm missing? Perhaps it is impossible. I look to you for guidance.

Thanks!
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Re: Streaming output way too hot

Postby ef37a » Wed Sep 16, 2020 3:22 pm

Now, "Hai no NOthing Mr fa...." but, what happens if you ignore the interface and listen to the steam via the internal sound card? (I am about to do that on a W10 lappy)

Well, it IS hot! Crowding 0dBfs but never distorted (I can't actually tell on that voice!)

I monitored in Audacity and the speech is hovering around -12 with peaks to neg 3 or 2.
I then plugged in my UCA202 (cos it was handy) and the sound was still clean, well hot but clean.

All listened to on AKG K92s.

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Re: Streaming output way too hot

Postby Kwackman » Wed Sep 16, 2020 3:29 pm

I've just listened on a MacPro, (High Sierra & Safari) and using a Audient iD22.
Before putting it on I'd been listening to music on this computer, and didn't move the volume control.
The podcast sounds fine here, reasonable level compared to the music and certainly no (unintentional!) distortion.

I also listened on a MacBook's internal speakers, (Catalina & Safari) and even with the Mac's own volume turned up full, there's no distortion.
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Re: Streaming output way too hot

Postby Hugh Robjohns » Wed Sep 16, 2020 3:51 pm

Watchmaker wrote:Unfortunately SOS's player does not have a volume control and it's rendering the product unusable. (Ironically enough, it's distorted beyond listenability).

I share your frustration at the lack of a volume control in the app... but it really shouldn't be 'distorted beyond listenability' -- if that's the case it's something you're doing at your end. The source material peaks to around -2dBFS and has an average level of around -12 or -14dBFS -- so exactly on a par with most commercial streaming services.

I have calibrated my reference levels...

Your distortion problem suggests you have some serious gain in the signal chain from the streaming app somewhere... and that's rather difficult for me to fathom.

Yes, I can see that the streaming content would be LOUD compared to music on the DAW hovering around an average level of -20dBFS... but it should still be clean.

If it's not, that suggests your monitoring chain can't accommodate signal peaks approaching 0dBFS, and if that's the case your reference level alignment hasn't taken into account the maximum SPL capability of your speakers!

Output meters on both a Focusrite 8PreX and and a UAD Apollo 8 show that all headroom has been removed from the audit stream appears brickwalled at -3dbfs.

Sounds perfectly reasonable to me...

...and -3dbFs at the interface output induces regular clipping (>+18) at the monitor controller (Audient Nero).

Busted! :lol: Your system alignment is clearly very, very awry!
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Re: Streaming output way too hot

Postby Watchmaker » Wed Sep 16, 2020 4:15 pm

:clap:

Thanks Hugh. I guess I need to orient the DAW to the system level, whatever that may be!

I guess I gotta figure out how to generate a test tone from within the OS then twiddle the DAW to that. I incorrectly assumed that software levels were governed by a standard so that DAWs output would correspond to the system level but apparently that ain't the case. Any handy SOS articles on that?!
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Re: Streaming output way too hot

Postby Watchmaker » Wed Sep 16, 2020 4:21 pm

Interesting, When I try to configure speakers using Mac system prefs, the pink noise tone fully clips the interface, as in pegged to the top of the meters!

This is where the problem lies. How do I normalize/regulate/attenuate at this hand-off?
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Re: Streaming output way too hot

Postby Hugh Robjohns » Wed Sep 16, 2020 5:15 pm

Watchmaker wrote:I guess I need to orient the DAW to the system level, whatever that may be!

I'm not sure what you mean by system level!

The concept is straight forward though...

Audio within your computer -- from the DAW or streaming services or whatever -- is all digital, and all related to 0dBFS.

That digital audio is routed to your interface, and the D-As in your interface convert the digital signal to analogue with a fixed relationship between 0dBFS and an analogue system level -- in the case of the Audient id22, 0dBFS equates to +18dBu.

So... you need to adjust the input sensitivity of your speakers to that +18dBu delivers the maximum SPL you want in your room... and/or -2dBu delivers the acoustic reference level associated with -20dBFS in the DAW.

I can't remember how the monitor controller facilities in the ID22 work now, but the manual should provide all the relevant information for optimising the gain structure.

I incorrectly assumed that software levels were governed by a standard

They are... 0dBFS is 0dBFS whether it comes from the DAW or a streamer...

The problem in your situation appears to be that the speakers or some other part of the signal chain can't cope with the full digital signal range up to 0dBFS.
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Re: Streaming output way too hot

Postby Hugh Robjohns » Wed Sep 16, 2020 5:20 pm

Watchmaker wrote:When I try to configure speakers using Mac system prefs, the pink noise tone fully clips the interface, as in pegged to the top of the meters!

Firstly, a signal can legitimately hit 0dBFS without being clipped!

What you need to know is what peak amplitude that pink noise signal actually has... but a peak-level pink noise signal isn't very helpful for aligning speakers!

I'm afraid I'm not a Mac user so I can't help when it comes to controlling audio levels within a Mac. sorry.

My go-to for accurate reference audio files is the BlueSky site:

http://abluesky.com/support/blue-sky-calibration-test-files/
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Re: Streaming output way too hot

Postby Watchmaker » Wed Sep 16, 2020 5:54 pm

Dr. Hugh, you are a treasure I will explore the blue sky content, with thanks!

Just for clarity, I'm using an Apollo 8 through an Audient Nero.

Good to know that 0dbFS is consistent within the code. I figured that had to be the case, but oddments raise odd questions. What I don't understand is why that seems to be getting adjusted somewhere between the browser and the DA conversion.

I've run a couple of tests, one of which informed me, partly:

I ran the iMac headphone out to the controller and get a reasonably comparable volume with the Apollo. Subjectively (as I don't have a way to measure what the onboard sound card is outputting) it tracks with the Apollo and since I know what that output is, it's close enough for listening.

However, going through the Focusrite, is where it goes south. This device is much louder and clearly clipping significantly. With an SPL set C weighted/slow, the Apollo generates 63 db while the Focusrite is kicking 74db at the listening position, ceteris paribus. Go figure. I'm lucky enough to be able to switch around at the push of a button so will learn to live with it rather than go down a bunny trail of probably unsolvable logic traps and be-knighted program incompatibility. Although this is a new behavior relating only to one podcast. I've simply been turning down the streaming volume on other sites so it hasn't ben an issue.

As an aside (old man story time)... When I was in the Navy studying electronics, the instructors welcome to the class was to enquire what "AM" stood for "amplitude modulation" was the enthusiastic response. "good. very good. Now, what does FM stand for?" We all dutifully shouted "frequency modulation, sir!" to which he shook his head in sorrow and looked at us with utter contempt. "f*** Magic," he said. Truer words were never spoke.
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Re: Streaming output way too hot

Postby Watchmaker » Wed Sep 16, 2020 6:55 pm

Ok, I figured out that I had the wrong template loaded in FR Control so I simply lowered the volume of the software playback. Lousy metering so it's all judging by the Nero's meters but there ya have it. I can do a more careful reset later. Nothing like thinking out loud in public thanks for the help.
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Re: Streaming output way too hot

Postby Hugh Robjohns » Wed Sep 16, 2020 7:19 pm

Watchmaker wrote: Just for clarity, I'm using an Apollo 8 through an Audient Nero.

Okay..l so where does the Audient id22 fit in?

...going through the Focusrite, is where it goes south. This device is much louder and clearly clipping significantly.

It's quite possible that, for a specific digital signal level into different converters, their analogue output signal levels might be different. For example, some converters generate +18dBu for a 0dBFS input, and some generate +24dBu, and some do something else entirely...

A +24dBu converter connected to a speaker will obviously sound 6dB louder than a +18dBu one, all other things being equal!

But a converter shouldn't be clipping unless the digital signal feeding it has been boosted beyond 0dBFS.

So, the first thing to establish is precisely what is 'clipping significantly'? The interface or something connected to its analogue outputs?

If its the Audient interface's D-A that's clipping, there must be some digital gain present in the signal routing to the interface, either in the Mac's operating system somewhere, or in the Audient's controller app.
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Re: Streaming output way too hot

Postby Kwackman » Wed Sep 16, 2020 10:03 pm

Hugh Robjohns wrote:Okay..l so where does the Audient id22 fit in?.

I mentioned in a post above that I use one, maybe that's caused a bit of confusion?
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Re: Streaming output way too hot

Postby Hugh Robjohns » Thu Sep 17, 2020 11:52 am

I am easily confused! :D
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Re: Streaming output way too hot

Postby Kwackman » Thu Sep 17, 2020 11:54 am

Hugh Robjohns wrote:I am easily confused! :D

"Where there is clarity, let me bring confusion" that's my USP! :)
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Re: Streaming output way too hot

Postby Hugh Robjohns » Thu Sep 17, 2020 11:59 am

I might use that as my signature... :lol:
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