Request for an idiot's guide to using the optical line in/out

[SlowRunner]

Would anyone be kind enough to provide an idiot's guide to explain the following:

a) what the optical line in/out is/does
b) why is it so highly sought after?
c) how is it utilised?
d) what to do with it in a recording context?

Thanks!

[sweetspot]

Here's a good place to start

Usage may vary, but it's a great option to have in a portable device, especially if you also have a portable (or non if you'd prefer) DAC (digital to analog converter) with which to connect it to. This will totally bypass the iHP's internal DAC and provide you with a whole other level of sound quality, in combination with a good external source (receiver, pre and pro amp etc..)

Look at it this way, get yourself a iHP 140, throw an 100 gig (or more if one fits) HD in it, load it up with FLAC files, and hook it up to a great external DAC and amp, and you've got a premium system right there.

For a more technical explanation, if Shadesbass is around here at some point, he'd be THE man to give the dissertation ! Though I'm sure that there will be more than a few people chiming in here in a while..

Doug

[BBD]

Let Shadesbass handle the "Guide" and I'll cover the "Idiot" portion of the OP.....

Having just picked up a new H120, I can tell you the output signal is far cleaner than any other DAP I've heard, whether through my Jeep's in-dash stereo or home hi-fi.

[jamato8]

I have to agree. The output from the line section of the 100 series is extremely good. I use the optical out all the time going into a good external dac that then feeds my headphone amplifier but the line out to an amp also works well and it is surprising how good the internal dac of the iriver is and how sad that they don't make this unit any longer. The reason why I have too many of these and may pick up one more. Now to figure out the right adapter so I can use a zif hard drive in the H140.

[sweetspot]

Originally Posted by jamato8

I have to agree. The output from the line section of the 100 series is extremely good. I use the optical out all the time going into a good external dac that then feeds my headphone amplifier but the line out to an amp also works well and it is surprising how good the internal dac of the iriver is and how sad that they don't make this unit any longer. The reason why I have too many of these and may pick up one more. Now to figure out the right adapter so I can use a zif hard drive in the H140.

I'm sure I linked you to the right one. But if you're in doubt, guess we'll keep looking..

[caligula]

Hey, to continue the idiot thing... lol

If I got an Ibasso D1 would I simply need to connect the optical out of the ihp120 to the optical in of the ibasso and then connect my headphones, or would I then need to connect another amp to the ibasso?

Apart from headroom amps, the ibasso is the only other portable amp I know of which features an optical connection.

Cheers, I suppose this question is aimed more towards Jamato.

Cheers and ps sorry to hijack

[shadesbass]

Originally Posted by sweetspot

For a more technical explanation, if Shadesbass is around here at some point, he'd be THE man to give the dissertation ! Though I'm sure that there will be more than a few people chiming in here in a while..g

Thanks for the big build-up!
I think most of it has been covered, at least from a playback point-of-view, but I'll try and explain the complete picture...

Originally Posted by SlowRunner

Would anyone be kind enough to provide an idiot's guide to explain the following:

a) what the optical line in/out is/does
b) why is it so highly sought after?
c) how is it utilised?
d) what to do with it in a recording context?

Thanks!

a) - c): We can think of an mp3 player as being constructed from several basic sections:

| Storage | -> | DAC | -> | Amplifier | (-> | Headphones |)

Storage consists of a hard drive or flash memory, where the music is stored in digital format.
The DAC (Digital to Analogue Converter) converts this digital data into an analogue signal, before it gets amplified to drive a pair of headphones.

Most mp3 players only have an output after the amplifier, but the H1xx players also feature a line-output (taken before the amp but after the DAC) and an optical (Mini-Toslink) output (taken before the DAC).

Most DACs and amplifiers in mp3 players are relatively low quality to keep production costs at a minimum, and this is acceptable for most people, as they use small inexpensive earbuds to listen to their music. However, when higher quality headphones are used, the shortcomings in the DAC and amplifier are revealed, and they become a bottleneck in the signal quality.

The optical output therefore provides a way of retrieving the music whilst it's still in digital format. This allows the user to connect an external DAC (and headphone amp) to their mp3 player, thus bypassing the lower-quality internal DAC and amp.
The external DAC must have an optical (Toslink or Mini-Toslink) input in order to connect to the H1xx. (A lot of portable DACs nowadays only feature USB connections for use with laptops.)

d) The optical input works in much the same way, but in the reverse direction. A digital signal is received through the optical input and stored directly to the storage medium (hard drive in this case). Receiving an equivalent analogue signal would mean having to convert it to digital format using an ADC (Analogue to Digital Converter) before storing it. So again, using the optical input bypasses a conversion process, which can degrade the signal quality*.
*This is a little more complex, as it is dependant on the sampling rate of the ADC and is out of the scope of this explanation.

Some CD/DVD players, computers and MiniDisc players have optical outputs which can be connected directly to the H1xx, but a majority of stereo digital signals are transmitted by copper coaxial cable terminated in RCA phono connectors.
Fortunately both optical and coax formats use the same protocol (S/PDIF), meaning they can easily be converted from one to the other, thereby greatly increasing the number of products that can be connected to the H1xx.
This also means that an external DAC with a coaxial digital input could be used with the optical output, provided an optical->coax converter is used.

As a final note, converting from optical to coax or vice-versa does mean adding a conversion process into the signal chain, which is what we've been trying to avoid above. However, digital<->digital conversion losses are tiny (although not necessarily negligible - again out of the scope of this discussion) when compared with the potential losses incurred in the digital<->analogue conversion process.

Originally Posted by caligula

If I got an Ibasso D1 would I simply need to connect the optical out of the ihp120 to the optical in of the ibasso and then connect my headphones, or would I then need to connect another amp to the ibasso?

The D1 has in integrated headphone amplifier, so you can connect your headphones directly to it.
However, it also features a line-output, allowing you to use a different headphone amp if you wish.

[SlowRunner]

Thanks, Guys (especially, Shadesbass!)

I had to read through the Shadesbass's guide twice to take all the information in; I now can visualise how the optical line in/out now works and understand why the sound quality (through an external DAC and amplifier) would be that much better than, say, my H340.

There is still some confusion in my mind, though, about recording with the optical line in - would I need to buy a microphone with a mini toslink? Does such a thing exist or am I talking complete tosh? Excuse my ignorance but I'm a complete novice when it comes to electronics in general! I have an H120 on the way and want to be able to exploit it's full potential! I intend to use it mosly for recording but it may replace my H340 as DAP of choice.

[BBD]

So...as I've volunteered (rather, been destined) to be the "Idiot" portion of the discussion......

Does this mean I should get a new amp for the home system? I currently hook up my DAPs to the RCA jacks w/ a Y-cable (it's a Monster--bought it before I knew better, though it works a treat), but would a different connection be needed to take full advantage of the optical-out?

[shadesbass]

Originally Posted by SlowRunner

Thanks, Guys (especially, Shadesbass!)

I had to read through the Shadesbass's guide twice to take all the information in; I now can visualise how the optical line in/out now works and understand why the sound quality (through an external DAC and amplifier) would be that much better than, say, my H340.

No problem. I'm glad it was useful!

Originally Posted by SlowRunner

There is still some confusion in my mind, though, about recording with the optical line in - would I need to buy a microphone with a mini toslink? Does such a thing exist or am I talking complete tosh?

A microphone produces an analogue electrical signal (its operation is exactly like a speaker in reverse), so you will not find a microphone with an optical output.

A similar signal chain exists for the input to the H1xx as the output:
| Microphone | -> | Amplifier | -> | H1xx line-in |
OR
| Microphone | -> | Amplifier | -> | ADC | -> | H1xx optical-in |

Note that the amplifier 'module' above is not the same as the headphone amplifier in the output signal chain above. They perform different roles and are not interchangeable.

A lot of microphones require a separate amplifier to increase the signal strength to line level and sometimes to power the microphone if it is a condenser type (see here for different microphone types).
Some microphones do have small integrated amplifiers and therefore do not need a separate amplifier (although many still benefit from one).

The line-in of the H1xx is generally considered to be pretty good, so investing in a separate ADC to feed the H1xx optical input would not be a cost effective improvement in sound quality IMHO. You would be better off spending more money on a good mic setup.
Check out this thread for some useful live recording and microphone tips.

Originally Posted by BBD

Does this mean I should get a new amp for the home system? I currently hook up my DAPs to the RCA jacks w/ a Y-cable (it's a Monster--bought it before I knew better, though it works a treat), but would a different connection be needed to take full advantage of the optical-out?

To take advantage of the optical output, you will need an external DAC, either in the form of a separate unit or integrated into an amp/receiver (i.e. one with digital inputs). If you're happy with the other features of your current amp, I would suggest looking into a standalone DAC.
Any external DAC you consider must obviously surpass the quality of the H1xx internal DAC, otherwise you may as well just use the line-out as you are currently doing.
A mid-fi (Sony, Phillips etc.) amp/receiver with digital inputs will probably not produce significantly better results than your current setup, as the H1xx DAC is reasonably good IMHO.

Of course, if you want ultimate sound quality you should consider spending $50k on a Meridian Audio processor and DSP speakers, as this would keep the signal in the digital domain right up until the last minute.

[jumbuck]

Very informative Shades , all the things I've wondered but was never game to ask.

Um...

While your doing guides ...

Can I request a Idiots (me) guide for speaker impedance?
In particular what is the minimum ohms for speakers you could connect to the player? And does the volume setting offer any protection from over loading the internal amp if lower ohm speakers are being used?
I've seen some small non-amped external speakers with 8ohm ratings which would be useful for listening to podcast at night but have never been game to purchase them for fear of damaging the player.

[SlowRunner]

Originally Posted by shadesbass

No problem. I'm glad it was useful!


A microphone produces an analogue electrical signal (its operation is exactly like a speaker in reverse), so you will not find a microphone with an optical output.

A similar signal chain exists for the input to the H1xx as the output:
| Microphone | -> | Amplifier | -> | H1xx line-in |
OR
| Microphone | -> | Amplifier | -> | ADC | -> | H1xx optical-in |

Note that the amplifier 'module' above is not the same as the headphone amplifier in the output signal chain above. They perform different roles and are not interchangeable.

A lot of microphones require a separate amplifier to increase the signal strength to line level and sometimes to power the microphone if it is a condenser type (see here for different microphone types).
Some microphones do have small integrated amplifiers and therefore do not need a separate amplifier (although many still benefit from one).

The line-in of the H1xx is generally considered to be pretty good, so investing in a separate ADC to feed the H1xx optical input would not be a cost effective improvement in sound quality IMHO. You would be better off spending more money on a good mic setup.
Check out this thread for some useful live recording and microphone tips.

Thanks again. When recording gigs with my H340 I use the Skytronics EM-8 condenser mic + battery box (as recommended by Framesaver) via line in with some pretty decent results. I guess my set up won't change when I switch to using the H120.

To make the most out of the optical in/out, I've been checking out DACs today but how "portable" can you go? Do you guys take your DACs out for country walks or are they for home use only? Being vertically challenged and a bit of a weed, I try to keep the weight of my bag to a minimum!

[sweetspot]

These things are NOT cheap. But they're out there.

First and foremost, the DAC/amp combo, from the wonderful Mr. Ray Samuels.. Introducing, the Predator Nice piece of kit right there. No digital toslink input though.. so may not be what we're after. The next one however, looks nice

Then, Google was able to score me:

Core Sound — HeadLine Portable 24/192 DAC, Headphone/Line Amplifier and Source Selector

HeadRoom makes some combo packages

Packaged Systems - HeadRoom - Right Between Your Ears

If you're feeling kind of froggish, you can leap at this:
HeadWize - Project: A Portable DAC with Headphone Amplifier by Andrija Ifkovic

While I'm sure there are more, I'm also sure that you have Google at your disposal as well.

[SlowRunner]

Thanks, Sweetspot.

Checked the above out today too and whilst they all look fab I was hoping that they'd come in a little cheaper. I think I'm going to have to hold off on the external DAC/amplifier dream for now but I'll realise it one day!

[jamato8]

I use the Predator with the iRiver most every day. I also have an iBasso D1, which has a dac that can receive either optical or coax digital in and has the ability to swap out opamps, much like changing tubes on a tube amp. There are many fine portable amps out there of all shapes and sizes. The Predator is one of the highest quality for playback on the market for portables.

[caligula]

Awesome info sweetspot, shades and Jamato, really appreciate the simply laid out and informative information, and to the op, the ibasso d1 would most probably be the best portable solution (in regards price at any rate ) to employ a toslink connection and it retails at $250 which for a dac/amp combo is a snip at the price.

Sadly, for me at any rate, its gonna be a few mths before I can purchase it lol oh well ya standard mini-mino will have to do me for connecting the iriver up for the time being.

[sweetspot]

Originally Posted by caligula

Awesome info sweetspot, shades and Jamato, really appreciate the simply laid out and informative information, and to the op, the ibasso d1 would most probably be the best portable solution (in regards price at any rate ) to employ a toslink connection and it retails at $250 which for a dac/amp combo is a snip at the price.

Sadly, for me at any rate, its gonna be a few mths before I can purchase it lol oh well ya standard mini-mino will have to do me for connecting the iriver up for the time being.

The standard line out really is quite good, and when used in conjunction with a decent portable amp (IF your cans need that much juice, of course) you can still be the bell of the ball ! The iHP is quite the versatile DAP, really.

[caligula]

I have the k701's, w1000 and beyer dt880 did start out with portable gear at the start of this year bur obviously with the move to "proper" cans will need a decent home amp. Currently using a little dotII tube amp, but will be hoping to get a decent-ish home amp at some stage in the fututre but I happen to see an ibasso d1 before then lol I do have a few portable headphone amps, but none of them use the optical connection so it's good to hear the ihp120's standard mini out is a good one. I am impressed with the h340's and by all acounts the h100 betters it?