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Building a 70s system??

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Re: Building a 70s system??

Postby CS70 » Fri May 29, 2020 10:41 am

Hugh Robjohns wrote:No, nothing is lost at all... and this is a fundamental aspect of sampling theory that eludes many people.

Indeed, this is what most people have hard time getting! I blame these pictures in introductions to sampling, where a crude ladder of levels is shown superimposed to a nice smooth curve. In these pics there's lot of information loss obviously, as the sampling rate is super low. People remember that and think "hey there's always gonna be some small error".

It's a bit like the infamous model of an atom as little solar system... great to remember, "right" within a very narrow meaning and totally misleading as a model of the actual thing!

Perhaps it would probably be better to just start these intros with "a discrete space can preserve all the information carried by an continuous space" and then follow with what "can" means..
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Re: Building a 70s system??

Postby The Elf » Fri May 29, 2020 11:12 am

It took a few attempts from the knowledgeable guys here to nail the *true* (as opposed to what I *thought* it to be) dithering to my brain. Once I grasped this the rest made a LOT more sense.

Which is why I have no time for this 'analogue good - digital bad' nonsense. You get out what you put in - simple as that.
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Re: Building a 70s system??

Postby Hugh Robjohns » Fri May 29, 2020 12:35 pm

Strictly speaking, you get out what the system allows in... :lol:
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Re: Building a 70s system??

Postby Eddy Deegan » Fri May 29, 2020 12:43 pm

Fantastic explanation Hugh. I am sure I've read much if not all of this in bits and pieces elsewhere but putting it all together and applying it to the scenario we've been discussing really has enlightened me.

Thank you very much for that :clap: :thumbup:
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Re: Building a 70s system??

Postby blinddrew » Fri May 29, 2020 12:43 pm

The Monty video is excellent. :)
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Re: Building a 70s system??

Postby Eddy Deegan » Fri May 29, 2020 12:49 pm

blinddrew wrote:The Monty video is excellent. :)
Yep - watching it now :-)
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Re: Building a 70s system??

Postby Hugh Robjohns » Fri May 29, 2020 12:55 pm

Monty has a done a few and they're all very good. But that one is particularly informative and I love the way he has gone to the trouble of getting analogue test gear and has created some very slick demonstration tools on the thinkpad.
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Re: Building a 70s system??

Postby Martin Walker » Sat May 30, 2020 1:58 pm

I've watched all of Monty's videos on various occasions and they are indeed a most rewarding listen/view :clap:

I still think of stuff like this every time I download a new album via Bandcamp in FLAC format only to discover that it's 24-bit/96kHz - I immediately run all the tracks through a Wavelab batch converter - no-one needs 24-bit downloads for a final product, and (even worse) there's one otherwise wonderful label out there that actually charges MORE for their 24-bit releases than the 16-bit ones.

If I can think of a quick way to temporarily discard the top 16-bits to listen to what's lurking down there in the bottom 8 bits , without endangering my hearing or my gear if I make a mistake, I'll be fascinated to see whether there's any valid musical data down there that I could actually hear in a typical playback environment to make it worth paying more. ;)


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Re: Building a 70s system??

Postby Tim Gillett » Sat May 30, 2020 3:31 pm

I sometimes check the noise floor of a quality live acoustic recording with a bit meter. Unless the recording's been plastered with NR the noise floor rarely if ever sits as low as 16 bits. But I know people who won't buy anything less than 24 bit releases. As if the 16 bit noise floor was a problem for them in the past.
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Re: Building a 70s system??

Postby Arpangel » Sat May 30, 2020 4:38 pm

Tim Gillett wrote:I sometimes check the noise floor of a quality live acoustic recording with a bit meter. Unless the recording's been plastered with NR the noise floor rarely if ever sits as low as 16 bits. But I know people who won't buy anything less than 24 bit releases. As if the 16 bit noise floor was a problem for them in the past.

I think the dynamic range of a symphony orchestra is around 70dB? so 16 bits, AFAIK, should be more than OK for that.
I use 24/48, I don’t know why, because I can I think, but I really can’t tell the difference between that and 16 bit, I can definitely hear the difference at lower resolutions than 16 bit though, on some types of music, but higher, and my ears just aren’t good enough.
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Re: Building a 70s system??

Postby The Elf » Sat May 30, 2020 4:56 pm

Arpangel wrote:
Tim Gillett wrote:I sometimes check the noise floor of a quality live acoustic recording with a bit meter. Unless the recording's been plastered with NR the noise floor rarely if ever sits as low as 16 bits. But I know people who won't buy anything less than 24 bit releases. As if the 16 bit noise floor was a problem for them in the past.

I think the dynamic range of a symphony orchestra is around 70dB? so 16 bits, AFAIK, should be more than OK for that.
I use 24/48, I don’t know why, because I can I think, but I really can’t tell the difference between that and 16 bit, I can definitely hear the difference at lower resolutions than 16 bit though, on some types of music, but higher, and my ears just aren’t good enough.
16 v 24-bit in tracking is about noise floor, dynamic range and headroom. You're not likely to 'hear' an isolated difference, because there really shouldn't be any difference (what goes in is what comes out, remember?). But gather all those separate 16 or 24-bit tracks together and...

And don't use the word 'resolution' if you don't want to incur the wrath of the digital gods! :lol:
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Re: Building a 70s system??

Postby Hugh Robjohns » Sat May 30, 2020 6:11 pm

[quote="Arpangel"]I think the dynamic range of a symphony orchestra is around 70dB? so 16 bits, AFAIK, should be more than OK for that.

Depends on the frequency, but 70dB is a good rule of thumb. At the most it's about 80dB...

Image

But that's from a 'normal' listening position. Close mics and enthusiastic percussion could create a greater dynamic range during the recording, of course. And an enthusiastic audience sat under a stereo pair can create quite a high SPL too.

So yes, 16 bits are plenty for a consumer format, even for produced recordings with 'natural dynamics'. But 24 bits makes life a heck of a lot easier during the recording by allow more headroom.
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Re: Building a 70s system??

Postby Mike Stranks » Sat May 30, 2020 9:14 pm

When I was 'active' most of my recordings were 'live'. I wouldn't have dreamt of recording at less than 24-bit. As Hugh says, headroom, headroom, headroom.

Even if you've 'lined up' at a full rehearsal you can never guarantee that the levels would be the same... usually not! :)
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Re: Building a 70s system??

Postby Hugh Robjohns » Sat May 30, 2020 10:27 pm

Yep, red light syndrome. Always 6-10dB louder than the rehearsal.
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Re: Building a 70s system??

Postby Sam Spoons » Sat May 30, 2020 10:30 pm

:thumbup: Something every live sound guy learns very early in their career.
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