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56k modems relied on digital trunk lines

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Re: 56k modems relied on digital trunk lines

#121

Post by numpad0 »

sneak wrote: post #118
IncreasePosts wrote: post #108

Earlier quoted context omitted.

Why do 96 or 128khz sampled audio files sound better than 48khz ones? I blind tested and could always tell the difference between them, but not between 128 and 192

Did you generate the 48khz ones from the 96/128khz ones via downsampling or are they different recordings? Are they the exact same volume? We perceive things slightly louder as higher quality. Is it a double blind test, ie an ABX test? Are the bit depths the same? Many 96khz sampled files use 24 bits per sample, whereas 48khz usually uses 16 bits per sample.

ime 48/96/128kHz 16/24bit through a modern DAC and well warmed Class AB amp and barely more than okay headphones can be told apart in a double blind test

but you do need phile-enough gears(minus the gilded pebbles hot glued onto circuit breakers)

Re: 56k modems relied on digital trunk lines

#122

Post by genewitch »

cjrp wrote: post #76
OhMeadhbh wrote: post #18

Earlier quoted context omitted.

I think it was ubiquitous. NPR in the 90s and 2000s used ISDN to allow many of their commentators to work from home. I think where you hear those crazy 8KHz clipped calls is where it's not an option. Mostly these days remote radio and podcast interviews I hear remote participants sound more like they're on mobile phones: variable voice quality with an almost unbearable latency.

Apparently it was still used for commentators at the BBC until 2023 https://www.linkedin.com/pulse/ode-isdn-paul-furley/

ISDN was just completely phased out a year or two ago in the US, too.

Re: 56k modems relied on digital trunk lines

#123

Post by genewitch »

toast0 wrote: post #109
IncreasePosts wrote: post #108

Earlier quoted context omitted.

Why do 96 or 128khz sampled audio files sound better than 48khz ones? I blind tested and could always tell the difference between them, but not between 128 and 192

Typically, high sampling rate files are part of a different mastering process than what is published as a 44.1kHz cd audio or 48kHz dvd audio. Also, you might possibly be sensitive to resampling artifacts if your output device runs at 44.1kHz and your file is 48kHz or vice versa. Audio testing is hard, and testing on yourself is tricky... But if you have a sample that you're convinced sounds better at high rates than…

Oh come on. I have handheld recorders that do 192khz.

"Headroom"

And the idea that humans can't hear over 20khz is like "humans taste 'sweet' on the tip of the tongue, and 'bitter' on the sides"

As we get older the hairs in out ears break or whatever and our perception decreases, but I could hear the fly backs in my old monitors, I used to be able to see the flicker in 3khz pwm LEDs, and my induction hob drives my kids crazy but it's merely midly annoying to me.

Get a real soundcard and some young people and play square(pwm) and sine tones starting at 16khz and find out where they can't hear it anymore. I find studio monitors with tweeters that are not paper are the best.

Re: 56k modems relied on digital trunk lines

#124

Post by genewitch »

numpad0 wrote: post #121
sneak wrote: post #118

Earlier quoted context omitted.

Did you generate the 48khz ones from the 96/128khz ones via downsampling or are they different recordings? Are they the exact same volume? We perceive things slightly louder as higher quality. Is it a double blind test, ie an ABX test? Are the bit depths the same? Many 96khz sampled files use 24 bits per sample, whereas 48khz usually uses 16 bits per sample.

ime 48/96/128kHz 16/24bit through a modern DAC and well warmed Class AB amp and barely more than okay headphones can be told apart in a double blind test but you do need phile-enough gears(minus the gilded pebbles hot glued onto circuit breakers)

You only need low THD and accurate clocks.

Re: 56k modems relied on digital trunk lines

#125

Post by immibis »

OhMeadhbh wrote: post #17

Yup. I worked on the "Rapport" series of switches at Bell Canada. It was DS1 (Digital Signal 1) out one end and a rack full of Zyxel modems on the other side. The idea was RBOCs (Regional Bell Operating Companies) would put these in their CO (Central Office) and terminate 56k modem signals over the analog "last mile" loop to the customer premises and then do Frame Relay over the phone company's data lines to your ISP…

Isn't DSL basically the same thing? If you live in a jurisdiction with unbundled local loops (which I suspect you do not), your phone company terminates your DSL at their nearest "office" (often a roadside equipment cabinet nowadays) and then does Metro Ethernet over the phone company's data lines to your ISP.

If you don't live in that jurisdiction, it's the same but your ISP and your phone company are the same company.

Also you don't dial your ISP with a number.

Re: 56k modems relied on digital trunk lines

#126

Post by genewitch »

badc0ffee wrote: post #113
phil21 wrote: post #34

Earlier quoted context omitted.

The most bang for buck "employee benefit" I ever offered to my guys back in the earl 00's was a T1 line to their home for free. We could do this since local loops to most folks were about $150-200/mo, and we already had a channelized DS3 terminated at our rack at a local datacenter for our phone banks. If you bought your own DS1 retail you'd be paying upwards of $1k/mo back then to a provider. It was by far the best…

I had 1.5 Mbps DSL in 1999, and I think nearly all of my co-workers either had that or a cable modem with similar speed. I think T1s were like 5x the price for the same download speed.

What market did you have 1.5mbit dsl in, in 1999? GTE in LA county offered 768k/768k symmetric. In 1999. I can't remember when that was increased, but it was after GTE got bought out.

Re: 56k modems relied on digital trunk lines

#128

Post by Sesse__ »

genewitch wrote: post #123
toast0 wrote: post #109

Earlier quoted context omitted.

Typically, high sampling rate files are part of a different mastering process than what is published as a 44.1kHz cd audio or 48kHz dvd audio. Also, you might possibly be sensitive to resampling artifacts if your output device runs at 44.1kHz and your file is 48kHz or vice versa. Audio testing is hard, and testing on yourself is tricky... But if you have a sample that you're convinced sounds better at high rates than…

Oh come on. I have handheld recorders that do 192khz. "Headroom" And the idea that humans can't hear over 20khz is like "humans taste 'sweet' on the tip of the tongue, and 'bitter' on the sides" As we get older the hairs in out ears break or whatever and our perception decreases, but I could hear the fly backs in my old monitors, I used to be able to see the flicker in 3khz pwm LEDs, and my induction hob drives my ki…

If you think you can hear ultrasound, it's nearly always due to nonlinearities in your system producing non-ultrasound when you try to play it. Seriously. (You can sometimes hear above-20 if it's very loud and/or you are pressing the source against your skull. Above-40 would be completely insane.)

The extra headroom can indeed be useful for some kinds of processing, but you can safely discard it for actual listening.

Re: 56k modems relied on digital trunk lines

#129

Post by Sesse__ »

numpad0 wrote: post #111
IncreasePosts wrote: post #108

Earlier quoted context omitted.

Why do 96 or 128khz sampled audio files sound better than 48khz ones? I blind tested and could always tell the difference between them, but not between 128 and 192

sampling theorem only applies to sine waves. the rate is bit like the order of (fourier)series expansion and so approximations deviate as rate reduces. how many orders is enough depends and is situational

No, it does not.
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