Be aware that these things have serious linearity (signal quality) issues, to the point where us "mere mortals" who design analog circuitry for T&M equipment try to stay away from them wherever possible. Audiophiles, of course, can hear the difference between copper, silver, gold, or platinum plating on the cable shield's drain wire in their neighbor's washing machine when he's on vacation in Hong Kong, so, you know, use with caution, you don't want to give them a heart attack or anything.
(Unless you like the particular flavor of distortion these guys give. Then, by all means, help yourself!)
Your comment can only be truly appreciated by plumbing the bizarre depths of "high-end audio" where nitwits (errr... customers) will pay $700 for a 6' Kapton-insulated power cord for their stereo. You know, to plug into the wall where it connects to 100 ft of Romex that cost $0.20/ft...
Just like everywhere else, silliness in the audio world is Pareto distributed.
As someone who loves good sound reproduction, it's tiresome to have people endlessly start talking about magic rocks or whatever whenever the topic of audio quality or audio electronics is brought up online. What's sad to me is that a lot of this cynicism seems to come from people who haven't even heard a really good pair of speakers or headphones, and it drives people away from having potentially beautiful experiences. Go visit your local high end audio shop and ask for a demo. They will probably be glad to have you. Listnening to well-recorded music through great transducers and electronics in a well-treated room is a mind blowing experience if you haven't tried it.
If it's nonlinear, the audiophile is guaranteed to relish the warm tone.
The definition of an audiophile is: someone who listens to the speakers (or the equipment, in general) rather than the music. Without distortion, there is nothing for the audiophile to listen to.
Optocouplers are neat. I few months ago, it was the middle of the night and I was thinking about how to add AC frequency monitoring to my GPS clock project. (Any frequency source is fun; I have two GPSes, a DS3231, a WWVB module, etc.) I didn't have any optocouplers, but I heard that LEDs work as photodiodes. Indeed, I found some random LEDs, connected one to mains with a large resistor, and pointed it at another LED. A 60Hz voltage appeared on the leads of the second LED. I then went to sleep instead of finding an ADC and writing the frequency sampling code... and so the thing never made it into production. But, neat surprise. If you want a quick and dirty optoisolator, you only need one type of component: the humble LED.
If you do get back to this project, you'd be better off with an X rated capacitor instead of a resistor. Lower power consumption, and it's explicitly rated to be across the line. I'd add a small fast acting fuse, as well.
If you need to electrically isolate an audio signal path, decent audio transformers aren't that expensive these days. A Triad Magnetics TY-250P is less than €6 at Mouser in single quantity, and is for sure a lot more linear than most optocouplers.
I've used the IL300's to interface signals in a legacy machine to a PLC and found they were not very linear. Don't see how these 4N25's will be any better. Wound up using texas instruments/burr brown isolation amplifiers instead (ISO122 or something).
Those are probably great if you can afford them. I've never had the budget for them in a production design, so haven't played with them much. Standard practice these days is just to toss a full ADC on the other side of the barrier and then isolate the SPI bus (or what-have-you). A few ADCs have the isolation built in, but for others there's stuff like TI's ISOW7841, which have 4 isolated digital lines plus isolated power in one package. It's all kind of expensive when added up, but it's cheaper than the old style analog isolation amplifiers, and you'll usually get more than one ADC channel once everything's together, so you win as soon as you want two signals to cross the barrier.
I am not an audio expert, and those circuits, 324 op-amp and all, hurt my eyes. That said, I didn't look close, and they might be fine for what you might call "utility audio".
The IL300 at least has defined linearity specs. If you do audio design you'll be better qualified than me to comment on them. But I can say: remember, too, if you're using these that they're basically current devices, the transfer ratio across the gap is going to be all over the map in production, feedback is another design challenge, and the saturation voltage will be high, all over the map, and basically the point where more light will not turn on the transistor any more.
If it's a hobby project, have fun, that's the point.
I solved a lot of audio problems in my complex setup (multiple inputs into multiple outputs) with a Toslink switch. Which is essentially a beefed up optocoupler...
I had a brief foray into electronics a few years ago hacking about with making a really crummy arduino synth. Part of that involved wiring it up to the midi output of a controller.
The concept of an optocoupler is just beautiful - isolate the circuits from each other by transferring your signal using light!
Looking at the diagrams here of how to increase the bandwidth through the device, electronics is all still total voodoo to me.
The second circuit is actually really boring once you recognize the parts. From left-to-right, it's:
1. A voltage to current converter
2. An optocoupler
3. A buffer
4. An amplifier
Stage #1 drives the optocoupler, since current is what gets turned into light inside the optocoupler.
The output is high-impedance, so you add a buffer, which is #3.
The output has a low-level, so you amplify it, which is #4.
If you work through a chapter of an EE book that explains op amps, and you're not afraid of algebra, you'll find this stuff becomes approachable very quickly. Designing circuits like this is a bit more challenging, but reading them is very approachable.
The LA-2A is great compressor. To be clear it uses a different application of "optical coupling" in that Audio is not passing through the optical connection.
The light source is driven by a DC amplifier that generates a control voltage derived from the audio signal. The light shines onto a photo-resistor that is used as the shunt component of an audio pad. (attenuator)
As the light intensity increases the pad reduces the signal level at the pad creating an audio compressor.
Could someone explain why nearly all amplifiers I see only amplify one half of the wave? I am seeing these optocouplers as only being able to amplify the positive side of the cycle and ignoring the negative.
In my mind I see the sound pressure as a positive and a negative where each side could be very different but ultimately adding up to zero over time.
Is it just that if you make a positive pressure wave the negative is right after and does not matter?
Class A amplifiers seem to take both sides into account. I am expecting to see some sort of H-Bridge configuration but never really see it. The most I see are positive and negative rails.
I think the search term you're looking for is "AC coupling". I have mostly done instrumentation work, which is usually DC-coupled, needing bipolar supplies to get the job done but doesn't have a low-frequency cutoff from the coupling capacitor.
"Wider bandwidth" is not so useful if the wide bandwidth does not include the frequencies you care about. Generally speaking, the higher the frequency, the smaller the transformer. Ethernet deals with very high frequencies, so they can make nice, cheap transformers.
Try putting audio through an ethernet transformer and see how much comes out the other side... I bet it won't be much, and you'll get extreme distortion unless your signal levels are very low.
[+] [-] exmadscientist|3 years ago|reply
(Unless you like the particular flavor of distortion these guys give. Then, by all means, help yourself!)
[+] [-] GeneT45|3 years ago|reply
Looks like my favorite example has disappeared, but there are always these: http://www.audio-consulting.ch/?Parts:Woodlenses
[+] [-] voldacar|3 years ago|reply
As someone who loves good sound reproduction, it's tiresome to have people endlessly start talking about magic rocks or whatever whenever the topic of audio quality or audio electronics is brought up online. What's sad to me is that a lot of this cynicism seems to come from people who haven't even heard a really good pair of speakers or headphones, and it drives people away from having potentially beautiful experiences. Go visit your local high end audio shop and ask for a demo. They will probably be glad to have you. Listnening to well-recorded music through great transducers and electronics in a well-treated room is a mind blowing experience if you haven't tried it.
[+] [-] kazinator|3 years ago|reply
The definition of an audiophile is: someone who listens to the speakers (or the equipment, in general) rather than the music. Without distortion, there is nothing for the audiophile to listen to.
[+] [-] dylan604|3 years ago|reply
[+] [-] xani_|3 years ago|reply
Page 9 if anyone is interested.
TL;DR to get good specs out of it is complex, just use ausio isolation transformer
[+] [-] melony|3 years ago|reply
[+] [-] jeffbee|3 years ago|reply
[+] [-] fuckstick|3 years ago|reply
[+] [-] jrockway|3 years ago|reply
[+] [-] mindslight|3 years ago|reply
[+] [-] squarefoot|3 years ago|reply
https://eu.mouser.com/datasheet/2/410/TY_250P-1892894.pdf
[+] [-] MisterTea|3 years ago|reply
[+] [-] exmadscientist|3 years ago|reply
[+] [-] xani_|3 years ago|reply
[+] [-] buescher|3 years ago|reply
The IL300 at least has defined linearity specs. If you do audio design you'll be better qualified than me to comment on them. But I can say: remember, too, if you're using these that they're basically current devices, the transfer ratio across the gap is going to be all over the map in production, feedback is another design challenge, and the saturation voltage will be high, all over the map, and basically the point where more light will not turn on the transistor any more.
If it's a hobby project, have fun, that's the point.
[+] [-] twawaaay|3 years ago|reply
[+] [-] snvzz|3 years ago|reply
[+] [-] aidos|3 years ago|reply
The concept of an optocoupler is just beautiful - isolate the circuits from each other by transferring your signal using light!
Looking at the diagrams here of how to increase the bandwidth through the device, electronics is all still total voodoo to me.
[+] [-] klodolph|3 years ago|reply
1. A voltage to current converter
2. An optocoupler
3. A buffer
4. An amplifier
Stage #1 drives the optocoupler, since current is what gets turned into light inside the optocoupler.
The output is high-impedance, so you add a buffer, which is #3.
The output has a low-level, so you amplify it, which is #4.
If you work through a chapter of an EE book that explains op amps, and you're not afraid of algebra, you'll find this stuff becomes approachable very quickly. Designing circuits like this is a bit more challenging, but reading them is very approachable.
[+] [-] CPLX|3 years ago|reply
[+] [-] lebuffon|3 years ago|reply
The light source is driven by a DC amplifier that generates a control voltage derived from the audio signal. The light shines onto a photo-resistor that is used as the shunt component of an audio pad. (attenuator)
As the light intensity increases the pad reduces the signal level at the pad creating an audio compressor.
[+] [-] buescher|3 years ago|reply
[+] [-] jensenbox|3 years ago|reply
In my mind I see the sound pressure as a positive and a negative where each side could be very different but ultimately adding up to zero over time.
Is it just that if you make a positive pressure wave the negative is right after and does not matter?
Class A amplifiers seem to take both sides into account. I am expecting to see some sort of H-Bridge configuration but never really see it. The most I see are positive and negative rails.
What am I missing here?
[+] [-] exmadscientist|3 years ago|reply
[+] [-] unfocused|3 years ago|reply
https://youtu.be/qTb65aoYA_Y
Careful, as Mr Carlson’s lab is addictive to watch :)
[+] [-] achr2|3 years ago|reply
[+] [-] klodolph|3 years ago|reply
Try putting audio through an ethernet transformer and see how much comes out the other side... I bet it won't be much, and you'll get extreme distortion unless your signal levels are very low.
[+] [-] jleahy|3 years ago|reply