Article: USB v. S/PDIF

[Gonzo1]

I agree for the most part. Lately I've been using the USB just to free up room on the PS Audio DLIII for other Toslink inputs. <br />

<br />

On another front, I seemed to have a problem with a firewire cable that was solved by buying a better shielded one. The music seemed to lack some excitement when I moved the HD and ran the cable vertically. Put in a shielded beefier cable and all is well.

[curious_george]

I'm interested in your thoughts on using Toslink to Mini-Toslink adapters. I assume there is a downside...?<br />

<br />

Can you buy decent adapters for use with good Toslink cables like Audioquest OptiLink-5?<br />

<br />

[The Computer Audiophile]

Hey curious_george - The reason I have the Monster cable that I do is because I have been unable to find another solution that I think is better. I don't consider the adapters an audiophile solution even though I've never tried one. It is just one of those things that doesn't seem right to me based on experience. I would be very happy if someone found a solution that allowed people to use their very nice Toslink cables. Maybe cable manufacturers will jump on the bandwagon with more people using Macs & PCs as their sources.

[TimH]

Thanks for the write-up Chris. And congrats on the new house. Always fun living out of boxes for a few months. (BTW, if you texted out that whole review on your iPod Touch then your thumbs must be sore. Assuming you didn't.)<br />

<br />

As you know I am starting to piece together my own system and over the weekend I hooked up my new Macbook Pro for the first time via that same Monster mini-to-TOS cable directly into the fairly decent DAC on my Yamaha AVR. My wife and I A/B'd several music selections against the original CDs and we're pretty darned happy with the sound. I'm sure I have about 50% of the "ear" that most around here have, but so far so good. <br />

<br />

I second your wish for suggestions for a better mini-to-TOS solution. I'm OK with that Monster cable but IMO it's definitely middle of the road. <br />

<br />

As you also mentioned, at some point I would like to hear a good USB DAC like the Benchmark to check out the difference and see if it's worth the expense to me, but am not sure how to go about an "audition" since there are no high end electronics stores near me. Is B&H OK with people doing this? <br />

<br />

TheOtherTim<br />

[The Computer Audiophile]

Hey Tim - B&H is a great store to purchase from, but I'm not sure of their audition policy. I know Benchmark as a 30 day money back guarantee. If you want I can talk to them to see how to go about an audition. I'm guessing they'll suggest ordering the piece and returning it if you don't want to keep it. <br />

<br />

If you have another specific DAC you want to audition I can try to help you get one to audition. Sometimes the manufacturers are very understanding about the lack of places to try their equipment. Let me know how I can help.

[Wavelength]

Chris,<br />

<br />

A better preface to anything is how it is implemented!<br />

<br />

There will always be some SPDIF products that will outpreform USB or other computer interfaces because the company that implement one or the other is superior.<br />

<br />

That being said... common... remember the story about how SPDIF started. An engineer at Philips was asked to devise a way to test a closed box completed CD player as easily as possible. The end was that the qc engineer would place the left/right analog as well as the SPDIF cable into the test rig and run the test disk. The test rig would verify the digital signal against the analog output signals. Some say that the interface was never even released until the Philips Picture CD units were released (WHY??).<br />

<br />

Anyway... USB went through years of development. Allot was considered and specifications (although convoluted) were released and parts started pouring out.<br />

<br />

To me there are basically 3 tiers of USB products that are available today:<br />

<br />

<em>1) Standard Adaptive products based on the PCM27xx series parts from TI/BB</em><br />

<br />

In the case of number 1 the company wants to come to market and be a player. But really this maybe only good as some of the SPDIF results and this is why some of the testing appears to be better leaning on the SPDIF side. Not to say that after these devices that you can't clean up the signal because you can but you are still limited to buffer size and formats described by the part.<br />

<br />

<em>2) TAS1020/TUBS3200 designs based on Adaptive or ASYNC using custom or adapted TI Reference designs.</em><br />

<br />

The TAS1020/TUB3200 are programable parts. You cannot buy these parts put them into your product and just use them. Every aspect of USB and audio has to be programmed. I have 18 (26 header files) modules of source code for my ASYNC implementation if you get the idea. These are great parts but are limited mainly in buffer memory size to 24/96. The problem is the TI Reference code is not documented well and there has been at least 10 programmers hands envolved in working with it so it takes a while to wrap your hands around it.<br />

<br />

<em>3) Custom controllers with custom code in either Adaptive or Async.</em><br />

<br />

Since like the TAS1020 there are other micro devices which have CODEC interfaces (able to link to dacs and adc's) and USB device ports that support USB 2.0 specification speeds that in the future there will be allot more robust DAC's and ADC's based on other devices such as some of the ARM devices used in iPod's such as the Samsung parts and the Portal Player units.<br />

<br />

~~~~~~~~~~~<br />

<br />

As far as the computer in it self being an issue with software etc... the great thing there is it is ever changing.<br />

<br />

Tell me the last time you received a firmware update for your SPDIF transport?<br />

<br />

Thanks<br />

Gordon<br />

<br />

[The Computer Audiophile]

Hey Gordon - Thanks a lot for the detail. I think you are really opening people's eyes and minds to the fact that USB is a prime-time major league player in high performance audio. You made a great point about firmware upgrades!

[kana813]

Chris-<br />

<br />

Here’s another SPDIF option to try with your set up. Get a Audio Authority 977R optical-to-coax converter for $75, see:<br />

www.audioauthority.com/product...<br />

<br />

FYI, Toslink is also effected by the quailty of TX/RX modules.<br />

<br />

This pass weekend, I ran my wife's Powerbook via the same <br />

Monster Cable(2 meters) you use into my upgraded Genesis Digital Lens and then into my digital processor via coax(Audience Au24).<br />

<br />

The sound quality didn't equal my Theta Jade transport directly into the processor.<br />

<br />

I haven't tried any USB to SPDIF converters, and I have no need for<br />

a USB DAC.<br />

<br />

Until the new PSAudio digital products are released, I'm using an upgraded SD Duet for PC playback.<br />

<br />

Aloha,<br />

<br />

Dan<br />

<br />

<br />

[The Computer Audiophile]

Hey Dan - thanks for the link. I know quite a few people looking for good converters for whatever reason. I'm not a big fan of them, but could be persuaded if the sound quality is there.

[carlseibert]

For all you manufacturers out there reading this - in audiophilia, interoperability is key. If every device has at least TWO OF THE THREE I/O formats, everybody can play nice together! Which means a positive user experience as we go forth compulsively upgrading our systems one component at a time. It also means that most combinations of components will have two possible interface choices. That means that we can endlessly amuse ourselves figuring out which interface you implemented better. And that means the cable companies can sell us miles of cable. All those cable dollars will trickle back through the economy and end the recession. Well, maybe.<br />

<br />

Personally, I've heard particular combinations of gear that have been happiest with each of the interfaces, but, apart from some early and painfully bad Toslink implementations, the differences haven't been huge.<br />

<br />

-Carl

[undilutedigital]

Should you have access to better than Red Book audio files and actually want to hear them a full resolution, then the interface you use can make a huge difference. I am the ecstatic owner of a PS Audio Digital Link III. It dramatically showed me the vinyl fanatics are right about this: mass-market digital audio does sound harsh, etc. But a device like the DL3 makes clear the problem isn't the digital format.<br />

<br />

The DL3 is advertised as supporting up to 24b/192kHz. But what they don't mention is that that's ONLY OVER S/PDIF. USB is limited to 16b/48kHz. This is a consequence of the TI/BB27xx USB DAC they're using to get S/PDIF from a USB source. The 27xx won't support high resolutions (probably because it wouldn't make a difference with the internal DAC anyway).<br />

<br />

And getting high res data out of a computer over S/PDIF can be a challenge too. Even if the computer has a S/PDIF output, don't presume you're getting anything higher than 96kHz out. And maybe not even that. This is a challenge of both hardware and software. Your operating system may downsample the data in software before outputting it to S/PDIF and IT WON'T TELL YOU THAT IT HAS CHANGED THE DATA. Unless your DAC or AV receiver has a display that tells you what data is reaching it, there's really no simple way of knowing.<br />

<br />

Sadly, these are the very early days for true high-res computer audio. I'm among those who nearly tore my hair out trying to figure out how to fix the audio dropouts over USB I was getting in Vista. Turns out the solution was relatively simple: I went back to XP.

[The Computer Audiophile]

Hi undilutedigital - Welcome to Computer Audiophile. Thanks for sharing your experience and knowledge about the DLIII. I plan on doing a followup to my review shortly. I finally ripped my DVD-Audio discs which have me some great 24/96 content I can output through my MacBook Pro optical port. The sound is so much better. It is literally a night and day difference.

[rappsy]

I read with great interest this thread and although I followed a good part of it, I have some more questions that I know are very subjective, but I think at this point I just need someone to tell me what to do.<br />

<br />

I have the Musiland MD-10 and want to use it to 1) go out of the DVD/CD player and 2) more importantly, my computer. So here are the questions:<br />

<br />

* Do I come out of the computer using SPDIF into SPDIF of the MD-10?<br />

* Do I come out of the computer using USB into the SPDIF of the MD-10 assuming there is even a cable or converter to allow this to happen?<br />

* Do I come out of the computer using USB into USB of the MD-10? <br />

<br />

I will be using the disc drive of the computer to play regular CD's and hard drive music? I am currently confused as to using something like FLAC or MP3 at 256 or 320?<br />

<br />

I am not technically advanced so don't really understand the underlying principles of what make this better or worse. I do however, know what I like and what I want out of my sound.<br />

<br />

One more thing. I have downloaded JR River free music jukebox and it is very easy to set it up and start using. I also downloaded FOOBAR 2K and am having a devil of a time configuring it. I also downloaded EAC and also am having a difficult time in geting it set up. Would dbPoweramp be a better way to go? Or what about using the ripping features of JRiver or Foobar?<br />

<br />

I am enjoying being a part of this community.

[The Computer Audiophile]

Hi rappsy - Don't worry about having more questions than answers at this stage. Since you do have questions and you are asking them you are far ahead of many others :-) Stick around here and you get is all figured out in no time.<br />

<br />

Since you want to use your DAC for both your computer and your DVD/CD player I think you should first try connecting via USB from your computer and via SPDIF from your DVD/CD player. This will be fairly convenient. Only you can decide if the sound is what you want. <br />

<br />

I would skip using the disc drive in your computer and use the hard drive exclusively. Rip the CD to your hard drive before playing it back. to me this is a much better solution. If you use the disc drive in the computer you are really negating many benefits of computer based audio. <br />

<br />

FLAC, mp3, 256, 320 etc... You don't need to worry about much of this unless you want subpar sound in favor of smaller file size. My suggestion is to use uncompressed (AIFF or WAV) or lossless compression (FLAC, WMA, ALAC). <br />

<br />

On Windows J RIver Media Center is a pretty good application. EAC seems to be a very popular ripping app on Windows, but it is certainly not the only one that will rip perfect music. You could always rip with iTunes. There aren't any easier apps than iTunes. You don't necessarily have to use iTunes for playback, but you could certainly rip with it. As long as the app you select has good error correction you should be fine.

[rappsy]

Thanks Chris for the followup. Here are a few more questions. I realize that many of the following questions are totally subjective, but I think at this point, I just need someone to TELL ME what they think I should do instead of more and more suggestions.<br />

<br />

Are you saying that I should go USB to USB for the computer to the DAC and SPDIF from the DVD/CDP player to the DAC instead of trying to convert the USB out of the computer to SPDIF?<br />

<br />

Even though there is supposedly a difference in SPDIF vs USB, are you saying that in my case there will probably be little difference.? Based on what I know about myself, I would rate myself somewhere between 1 and 2 on the following scale:<br />

<br />

1) Someone who is not technical, but has a decent stereo system, 2000 regular CD's, Outlaw receiver, universal DVD/CD player and Axiom M60 Tower Speakers.<br />

<br />

2) Audiophile.<br />

<br />

3) Technophile.<br />

<br />

I understand that and SPDIF cable is the preferable method out of the DVD/CD player than a Toslink optical cable. True??<br />

<br />

You mentioned that it doesn't make sense for me to play CD's out of the transport of the computer and that I should rip it first. I will not be ripping all CD's to the computer so sometimes will be doing this. Is this something I should not even consider? I suppose I can play it with the CD player, but I wll be trying to stay more with the computer.<br />

<br />

Software:<br />

I can see the benefit of using FLAC for Lossless reproduction. Is there really that big a difference in FLAC than MP3 using approx 256 or 320? Also, on jRIver, when I use FLAC it asks me for a number which is the Quality setting and it defaults to 6. Is that a good number to use?<br />

<br />

Also, is the JRiver ripping feature as good as others, such as EAC or dbpoweramp? I tried using EAC, and not being technically oriented, I'm lost. I have not tried dbpoweramp yet.<br />

<br />

The same thing with FooBar 2000. I got it to make sounds, but getting it to look and act like I want was not successful. Is JRiver a good alternative? What about JetAudio? <br />

<br />

I downloaded the AISO software and it becomes an option in JRiver. Is that the setting I should use when going through the USB to my DAC?<br />

<br />

Thanks again.<br />

<br />

Lenny...

[The Computer Audiophile]

Hey Lenny <br />

<br />

<i>"Are you saying that I should go USB to USB for the computer to the DAC and SPDIF from the DVD/CDP player to the DAC instead of trying to convert the USB out of the computer to SPDIF?"</i><br />

<br />

100% correct.<br />

<br />

<br />

<i>"Even though there is supposedly a difference in SPDIF vs USB, are you saying that in my case there will probably be little difference?"</i><br />

<br />

The difference all depends on the implementation of each in your system. I can't offer a good opinion either way on this one. Anyone who says they can is doing you a disservice.<br />

<br />

<br />

<i>"I understand that and SPDIF cable is the preferable method out of the DVD/CD player than a Toslink optical cable. True??"</i><br />

<br />

coax is preferable to Toslink.<br />

<br />

<br />

You can certainly playback CDs with your computer, but as a physical disc transport your CD player is probably better than the disc drive on your computer. But, the music ripped to a hard drive first will most likely beat both of them. I personally would only use the hard drive on your computer for playback and use the CD player if you must play a physical CD.<br />

<br />

<br />

Software:<br />

<br />

Never use anything that is lossy such as 256 or 320 mp3 files. I don't even use these on my iPod where space is a premium. FLAC or another lossless compression scheme will do, or I highly recommend uncompressed aiff. I use aiff for all my music, even my iPod.<br />

The FLAC setting of 6 should be for compression in terms of how compressed the files are. As far as I know a lot of people use the default. The level of compression has no baring on the sound quality. It is just for the file size. The more compression the longer the encoding will take.<br />

<br />

For ripping as long as you are using error correction you are good. The only thing some of the geeky rippers allow you to do is set a drive offset and get feedback on each rip to make sure everything ripped perfect. I use iTunes which provides neither of these options. I could obviously use any of the rippers if I want, but I don't feel there is a real advantage and I don't think the hassle is worth it.<br />

<br />

Use ASIO whenever possible on Windows.<br />

<br />

Let me know if I just clouded the waters instead of clearing it up for you :-)<br />

<br />

<br />

<br />

<br />

[rappsy]

Hi Chris:<br />

<br />

Thanks for the direct answers. Let's continue on.<br />

<br />

I see you highly recommended the AIFF format. I understand that it will work with many players including Itunes and the IPOD, so that is indeed handy, but it is also uncompressed and therefore as big as wav's. Does it tag, etc?<br />

<br />

How does FLAC stand up to it? I see that it is about 30-40% smaller and it can be put back into a WAV file for making music CD's with no loss in quality, and when playing it back on Foobar or JRiver it will sound as good as the original. I also understand that FLAC files will not work on Itunes or the IPOD, so it's another step when wanting to play it on these types of machines.<br />

<br />

How does Apple Lossless compare to FLAC? I assume it plays directly on the Ipod and Itunes as is, with no need to convert it to something else?<br />

<br />

If I want to go Lossless instead of uncompressed, what is my best option?<br />

<br />

As far as ripping goes, if you say that it doesn't really matter, then I will probably just go with the ripper in JRIVER. It has Flac, but does not include many other codecs, but I assume I can easily add those into the program. I don't need the best or the most technical, just one that does a good job. JRiver has error correction, so I guess I should enable that.<br />

<br />

As far as player goes, I assume JRIver is as good as most. I know that Foobar has tons of expansion, but even though I was able to get it to play, I couldn't get the GUI to do what I want, and trying to read through the various tutorials has me thinking that it is overkill. I should spend that time enjoying the music. I also saw Catrixx ($40) and Jet Audio, but I think JRiver is where I'm headed . Opinion?<br />

<br />

I installed ASIO. I assume that as long as the player plays sounds when I choose ASIO, than it recognizes the software. I assume that ASIO is software driven and that I don't have to install anything hardware wise.<br />

<br />

Well, as long as you don't mind the questions, I will keep on firing them to the forum. My next post will probably be on the specific settings that I will need to use to maximize the perfomance of the different software programs.<br />

<br />

Thanks in advance and sorry if there are any repeat questions.<br />

<br />

Lenny...

[The Computer Audiophile]

Hey there Lenny - AIFFs tag much better than WAVs. Cover art and other meta data are supported. <br />

<br />

Since FLAC is not supported in iTunes which is my application of choice I convert all my FLAC downloads to AIFF. FLAC certainly works excellent for many people around here and elsewhere. I don't want to deal with compression or compatibility issues and the larger size doesn't really matter to me. It is kind of funny to hear people with $100,000 audio systems talk about compressing their music so they don't have to spend that extra $500 on disk. Since FLAC is lossless I am sure you'd be completely happy with its performance and tagging ability.<br />

<br />

ALAC is another good lossless codec. The same things I said above about FLAC are also pertinent here. The only additional item to consider is that ALAC is proprietary. It may or may not even matter, but I think it is something to consider.<br />

<br />

I think JRiver is a great option on a Windows based computer. Some of the other application like Foobar are more like lab tools than music server applications. Don't get me wrong though, foobar is a very solid app for playback sound quality. ASIO can be a combination of software and hardware. If you audio card alters the data then it is of no use. If you have an external DAC like the Wavelength Cosecant v3 and use ASIO there is nothing to worry about.<br />

<br />

I'm all ears/eyes, so fire away when you have the next batch of questions or want clarification on something above.

[carlseibert]

Hi Lenny,<br />

<br />

If your setup is server-client or multiroom, especially if your network is wireless or maybe has a lot of other traffic on it, that might figure into your format choice.<br />

<br />

Personally, I use FLAC for that very reason. Save some disk space, too, but that's not such a big deal anymore.<br />

<br />

Like Chris, I like AIFF better than WAV for an uncompressed format. <br />

<br />

Another consideration is whether your system handles a given file format natively. My SlimDevices system, for example, will play just about anything, but some formats are transcoded on the fly before they're sent to the clients and we certainly wouldn't want that. <br />

<br />

If you're willing to take the battery life for sound quality trade-off to play lossless files on your portable, that's a consideration, too. Do you want a format that will work on your portable or do you want to transcode for the portable? I've lately gone the latter route. If I want an album on my iPod, I just trasncode an MP3 of it. <br />

<br />

-Carl

[rappsy]

Hi Again:<br />

<br />

Ok. I've made some decisions based on the wonderful feedback. I also want to thank Chris and everybody else who took the time to explain some of these questions in English. Other sites are so overtly technical that I couldn't figure out what was being said. There is a difference between data and information. Over there, I got data. Here I received information. Thanks.<br />

<br />

I am using my Musiland MD-10 DAC for my computer audio. Based on suggestions here, I will be using a USB out of the computer to USB in to my DAC instead of SPDIF out of the computer to the DAC. (This machine has multiple inputs.) As USB is different technically, does the cable matter? To get some sounds out of the system, I am using the USB cable that came with my printer, but I supposed there is something better. I will need about 8-10 feet. I am also using AISO as the output from JRiver. Do I need to order online, or is there a quality cable that Best Buy or Circuit or Radio Shack sells?<br />

<br />

Also, I need recommendations on a ground loop isolator. I have one from Radio Shack but the RCA's are hard wired. Any recommendations or does it matter? The isolators has reduced my buzz to zip so I know it works, but is there something bette?. I am not hearing any sound degradation, but is there? I know Radio Shack gets it share of criticism but they do a good job on many fronts.<br />

<br />

Also, the Musiland is now burned in. Do I need to keep it on all the time, or is an instant on good enough for listening? Should it be turned on for 2 minutes, 5 minutes before for best sound.? It's solid state, so I wouldn't think it would need much time to get up and running. I would prefer not to leave it on all the time.<br />

<br />

That's it for now.<br />

<br />

Lenny...

[musicalsound]

I've been comparing the following 2 configuration:<br />

<br />

1.) Mac OS X 10.5.3 with iTunes 7.6.2 playing AIFF files --> (via USB with 24 bit / 44.1 kHz setting in Audio Midi and standard USB cable) Benchmark DAC1 PRE <br />

2.) Sony DVP-S9000ES --> (via coaxial) Benchmark DAC1 PRE<br />

<br />

I wanted 1. to sound better but 2. always end up sounding cleaner. <br />

<br />

Is this possible? Could this be the version of iTunes or the USB cable or something else?<br />

<br />

[musicalsound]

I've been comparing the following 2 configuration:<br />

<br />

1.) Mac OS X 10.5.3 with iTunes 7.6.2 playing AIFF files --> (via USB with 24 bit / 44.1 kHz setting in Audio Midi and standard USB cable) Benchmark DAC1 PRE <br />

2.) Sony DVP-S9000ES --> (via coaxial) Benchmark DAC1 PRE<br />

<br />

I wanted 1. to sound better but 2. always end up sounding cleaner. <br />

<br />

Is this possible? Could this be the version of iTunes or the USB cable or something else?<br />

<br />

[The Computer Audiophile]

Hey musicalsound - Anything is possible. I know a few people who really don't care for the Benchmark sound very much and they probably would not be surprised by your findings here. I can tell you that my experience hasn't matched yours. The Benchmark is a really clean sounding DAC in my opinion. <br />

<br />

To be honest the first thought that comes to my mind is you are hearing all of the recording through the Benchmark / Mac system, and the Sony system may be removing some offensive sounds in order to sound "better." I'm not knocking your opinion or even suggesting you are wrong. This has just been my experience with some equipment I've heard in the past.

[The Computer Audiophile]

Hey Lenny - This can be a touchy subject but I've made up my opinion based on listening tests I've conducted personally. USB cables do make a difference. I highly recommend the Kimber USB cable available at <a href="http://www.audioadvisor.com/">Audio Advisor</a>. I did a review on this cable a while ago and took some serious heat for my opinion, but I stand by it 100%. If you want a technical explanation, from CA member Gordon Rankin, on why USB cables make a difference I recommend checking out <a href="http://www.audioasylum.com/forums/pcaudio/messages/2/28679.html">this discussion</a> over on Audio Asylum. <br />

<br />

I've never used a ground loop isolator so I have nothing to offer in this area. I do have a recommendation for you to get rid of a ground loop without anything like an isolator. I suggest floating the ground. Use a three prong to two prong adapter which "floats" the ground and removes any hum from a ground loop. I've personally done this before with great success and no need for mid-fi compenents in the audio chain.<br />

<br />

As far as leaving solid state gear on all the time, I don't do it. I usually give my system and my ears about 15 to 20 minutes of music flowing through them to warm up.

[One and a half]

There’s a lot to talk about which is better, more musical, dynamics…it’s only an electrical signal with an important difference.<br />

<br />

Toslink has the advantage of no electrical connection by conduction between the source and the receiver because the medium of data is pulsed light. <br />

<br />

The light what you see in a Toslink cable is generated by a LED at the source, and at the receiver, a device that receives light and converts the light energy to electrical signals. These devices are called optocouplers and have an inherent long term reliablity problem in that the success or failure of the device depends on how hard the LED is driven, temperature of the device and the switching response of the electrical section.<br />

<br />

An optocoupler is far from perfect and given current commercial considerations, many devices are at their limit of operation as a normal design criteria. Whether this applies to high end DACs I would hope not, but certainly worth the question for computer sound cards and outputs. This would have a bearing on the throughput by the optocoupler at either end of the cable don’t forget. So you end up with the drama, twice, with degrading optocouplers at different rates since you have different manufacturers of optocouplers. In my line of work in industrial electronics, many optocouplers have failed in service on printed circuit boards after about ten years service. For rotating equipment, you’re lucky to get six years. Current testing for reliability is stated for 1000 hours, so you can get that time at least.<br />

<br />

So despite isolation advantages, long term, reliable sound quality is best afforded by cabling with copper/silver/ptfe et al instead of the light. It would also explain sound quality differences from built in SPDIF light outputs from sound cards versus using USB or coaxial cables from the same computer.<br />

<br />

References:<br />

Google : Optocoupler Degradation<br />

<br />

http://jase.esrgroups.org/2_3_3_08%20proof.pdf<br />

<br />

http://www.secomtel.com/UpFilesPDF/PDF/Agilent/PDF_DOCS/ISONCONT/01_OPTO/1_636_41.PDF<br />

<br />

http://vishay.ru/docs/83718/83718.pdf<br />

<br />