Question about analog and digital audio

[Ajelvani]

So today i found some old boston ba735 speakers. In the subwoofer, it has a digital in which used a coaxial cable and an analog in with 3.5mm. The coaxial cable the speakers came with has coaxial on one end and what looks to be a 3.5mm mono on the other. I realized the reason the 3.5mm end was mono was because its digital, not analog. My sound card doesn't support digital on 3.5mm but only on optical, so i will need an adaptor. But knowing digital is much better than analog, why do phones and many devices still use analog 3.5mm and why are headphones still using analog 3.5mm when it could all be digital audio? What about microphones?

 

[dave_the_nerd]

Sound, as it travels through the air, is analog. To convert to and from analog to digital, you need a D/A converter, power, and for output, an amplifier. So it's a logistics problem: where do you put the converter and circuitry, and why? And how do you get power to it? (More importantly, how do you get power to it without mangling the audio signal?)

Headphones use analog connections, usually, for cost reasons. Cheap ones are cheap, and cheaper is better. Conversely, manufacturers of expensive headphones are assuming that you will be plugging them into a much nicer D/A converter and amplifier than they could possible build into the headphones themselves. But the cables are, presumably, verity high quality, and if you're an audio nerd, you're going to be smart enough not to wrap the wire around a power strip or something, so interference shouldn't be an issue.

In the middle ground, there are USB headphones.

Microphones are basically the same story. Cheap ones are cheap and don't have D/A converters because cheap. Expensive ones are expensive and don't need D/A converters because you already have an expensive D/A converter, and there are USB microphones in the middle.

There have been a few different digital connection standards over the years, some were brand-specific. I haven't seen any coax in a while - most of my digital stereo gear used S/PDIF. (5mm square connectors.) And many motherboards have S/PDIF outputs. A lot of newer computers use 3.5mm optical out because you can do a dual-mode optical/analog on a single port. (This used to be standard on Apple computers, dunno if it still is.)

In the last ten years or so, devices that were intended to interface only with computers have usually had USB interfaces. (Headsets, speakers, audio interfaces, microphones, etc.)

 

[Ajelvani]

Wow thanks for all that info man. Also, are rca connection for audio, left and right better than a singal 3.5mm connector for left and right. If their is no difference, how come some higher end soundcards and most amps have rca instead of 3.5mm jack

 

[Cerb]

I haven't seen any coax in a while - most of my digital stereo gear used S/PDIF. (5mm square connectors.)

S/PDIF is coaxial, traditoinally using RCA connectors. Optical is TOSLINK.

 

[Ajelvani]

S/pdif i believe means its digital. The connector can then be optical (toslink) or coaxial which i believe can work with any rca wire, correct?

 

[Ajelvani]

Another question. Lets say i have a blu ray player or soundcard, with a good dac. Lets say this blu ray player or soundcard then has a digital output (optical) if i connect this blu ray player or soundcard to a speaker with optical connection and analog connection, would it be better to use analog connection such as rca sine then the audio would use the dac in the blu ray player or soundcard rather than the one in the speaker itself?

 

[dave_the_nerd]

S/PDIF is coaxial, traditoinally using RCA connectors. Optical is TOSLINK.

Whoops. See what happens when I drink?

 

[dave_the_nerd]

Wow thanks for all that info man. Also, are rca connection for audio, left and right better than a singal 3.5mm connector for left and right. If their is no difference, how come some higher end soundcards and most amps have rca instead of 3.5mm jack

A bigger connector, thicker cable, etc., has/have different electrical qualities - theoretically you get a cleaner signal. That's why pro microphones used those gigantic XLR connectors forever, or why older studio headphones use those 6.25mm connectors instead of the 3.125mm ones.

Same with using a different cable for each channel (mono) vs. stereo. (Some people claim you can hear the L channel on R and visa versa.)

A decent quality 3.125mm stereo connector is good enough for most circumstances, most of the time. It's just the difference between "good enough" and "as good as possible." And in fairness, the smaller connectors CAN be good, if they're built well and you're not yanking them all over the place, twisting them, etc. (Which is often the case with portable music players.)

 

[Cerb]

S/pdif i believe means its digital. The connector can then be optical (toslink) or coaxial which i believe can work with any rca wire, correct?

All kinds of things are digital.

S/PDIF = Sony/Phillips Digital Interface. It is/was a "75-Ohm" interface, for short cables (quotes because it is rarely close to an ideal 75 Ohm with RCAs, but instead of changing connectors or standards, they've made transmitters and receivers for S/PDIF quite complicated to make it work well).

TOSLINK (TOshiba LINK) uses the same protocol, but is optical (because Toshiba had to be different).

Another question. Lets say i have a blu ray player or soundcard, with a good dac. Lets say this blu ray player or soundcard then has a digital output (optical) if i connect this blu ray player or soundcard to a speaker with optical connection and analog connection, would it be better to use analog connection such as rca sine then the audio would use the dac in the blu ray player or soundcard rather than the one in the speaker itself?

It's going to vary. If the output from the sound card is clean, though, a good sound card is probably better than what's inside a speaker that has an integrated DAC and amp. The chances of such a DAC's PSU and filtering being all that great are generally not going to be too high, as it was put in there more as a convenience feature, than anything else. And, unlike an amp, there's not really anything to be done with a DAC to tailor it to a set of speakers. OTOH, are the drivers really good enough to discern a difference between quality of DAC implementations (for which, in any given scenario, there will be a wall beyond which you can't hear a difference, even if it exists, once it's good enough for the amp and speakers)?

However, if it has optical in, that's one less place for a ground loop to occur. So, if the output from the sound card to the speaker isn't all that great, that will cut any electrical coupling between the player and output.

 

[MongGrel]

Yep they are both digital.

I prefer using TOSLINK myself.

 

[dave_the_nerd]

Another question. Lets say i have a blu ray player or soundcard, with a good dac. Lets say this blu ray player or soundcard then has a digital output (optical) if i connect this blu ray player or soundcard to a speaker with optical connection and analog connection, would it be better to use analog connection such as rca sine then the audio would use the dac in the blu ray player or soundcard rather than the one in the speaker itself?

If everything is working as well as it could and there's no interference, it's very unlikely you'd be able to tell the difference. But unless the DAC in the speaker was actually pretty bad, I'd probably be more worried about interference on the wire to the speaker. (Mine pick up radio signals!)

Older DACs that are limited to 16-bit/44KHz audio (standard CD Audio quality - common for older hardware) sometimes get goofy if you pipe a 24-bit or >44KHz signal to them. (My dad has this problem with his Behringer MS40s). Then you'd want to use analog.

But the actual DACs themselves are usually not the quality bottleneck - it's just doing math, after all. The problem tends to be the other associated circuitry, and interference from other nearby electronics. So I'd be disinclined to trust the DAC in your sound card, for instance, since it's inside your computer with a bunch of stuff whirring and buzzing around it. (There are good ones, and even shielded ones, but I don't know what kind you have, so I'm assuming it's, like, a low end Sound Blaster or something.)

The electronics in the typical consumer blu-ray player are also going to be good but probably not excellent. (So, likely, no better than what's in the speakers.)

 

[Ajelvani]

So i have the soundblaster recon 3d pcie. Im guessing if i got a usb dac, it wouldn't really make that much of a difference? Im also thinking of getting an av receiver to connect speakers and everything into. So an optical cable to the av receiver from my soundcard should be just fine. Right?

 

[dave_the_nerd]

So i have the soundblaster recon 3d pcie. Im guessing if i got a usb dac, it wouldn't really make that much of a difference?

The little thumb drive sized ones are... well they work, so I hesitate to use the word "scam" but I doubt it would make any kind of difference.

Im also thinking of getting an av receiver to connect speakers and everything into. So an optical cable to the av receiver from my soundcard should be just fine. Right?

Yes, a digital signal from your sound card to the receiver would be ideal.

 

[Cerb]

So i have the soundblaster recon 3d pcie. Im guessing if i got a usb dac, it wouldn't really make that much of a difference?

Do you hear noises or distortions that you know shouldn't be there, while using your PC? If not, I doubt you'll notice any difference at all.

 

[MongGrel]

So i have the soundblaster recon 3d pcie. Im guessing if i got a usb dac, it wouldn't really make that much of a difference? Im also thinking of getting an av receiver to connect speakers and everything into. So an optical cable to the av receiver from my soundcard should be just fine. Right?

The little thumb drive sized ones are... well they work, so I hesitate to use the word "scam" but I doubt it would make any kind of difference.

Yes, a digital signal from your sound card to the receiver would be ideal.

:thumbsup::thumbsup:

 

[Ajelvani]

Ok thanks

 

[mindless1]

But knowing digital is much better than analog,

Here's where the misconception starts. A person with average hearing, especially with average headphones, couldn't hear the difference between average quality analog output and digital.

Notice I wrote output, the last stage of amplification after any SNR issues are dealt with, since in the end, the speakers you hear are still driven by an amp approximating analog output (even if it's a digital amp).

I have issues with analog for a different reason. The average 1/8" headphone jack is crap that loses tension if used much then you get one channel cutting out. In modern electronics it gets even worse with the jacks not being through-hole, rely on mechanical fortitude from solder pads. Bump the plug wrong and you can rip it off the PCB. I could go on ranting about mUSB ports too but I digress.

 

[Ajelvani]

Yeah thats why i don't know why companies don't just use rca on most condenser Mics. I have a condenser mic and theirs always a buzzing because of the 3.5mm jack having connection issues because they dont last

 

[dave_the_nerd]

Yeah thats why i don't know why companies don't just use rca on most condenser Mics. I have a condenser mic and theirs always a buzzing because of the 3.5mm jack having connection issues because they dont last

What's your budget? If you're doing podcasting or something and need a nice mono recording, the AT2020USB or the Samson C01 USB is worth a look. (I mentioned before, those "midrange" USB microphones.)

 

[mindless1]

Pro mics use XLR connectors. If you're handy with a soldering iron (and using a sound card makes it more practical) you can wire up any connectors you want, though even panel mount 1/4" jacks are a big improvement over 1/8" PCB mount, if you get a decent brand from an electronics supplier. Alternate jack(s) can be mounted on a spare rear case slot cover... or just put a hole in the case rear for that matter though in either location you may want isolated jacks so they aren't creating a ground loop through the case.