[KaiSc]

Line level refers to low level signals like the rca analog output of a dac, 1-5v, 2v rca 5v xlr, headphone amps and preamps, while not quite high level(high level being an amplified signal, think speaker wire) are higher at 10v to 20v.

In fact the world of audio signals is divided in three main groups:

Low Level 0.001V to 0.3V, low energy:
microphones, turn table pickups etc., all kind of low voltage and low energy signals, often before being electronically amplified.

Line level, Voltage 0.3V - 20V, low energy, typically 2V:
intercontacts between different electronic audio devices, outputs from cd-players, cassette-decks and tape machines, interconnect between preamplifier and power amplifier, interconnects in recording studios, even the analog telephone line counts into that and gave the signal its name.

Power level, Voltage 0.1V to 100V, energy/power 0.001W to multiples of 10,000W:
all kind of signals originating from power amplifiers, intended to drive some kind of speakers or headphones.
This one has the widest variety of voltage and energy transmission, because it's an enormous difference if you want to drive sensitive InEars, or a big PA system in a show.
For a sensitive InEar 1/1000 of a Watt might be sufficient for earhurting levels, on a PA system for a bigger audience 100,000W may be necessary to serve the same purpose.
As can be seen, there is quite some overlap with the line level voltages, and such power amplifiers can be used as line drivers too, as long as the receivers maximum healthy voltage is not exceeded.
The problem might be, that power amplifiers, in contrary to most dedicated line drivers, are capable of supplying sufficient energy to literally toast electronic parts.

Mobius Aux input works with line level, and it's only the voltage that counts. It does not draw significant amounts of energy out of the source (it has a high input impedance).
According to my measurements Mobius can handle up to 1.8V without distortion, and and this is what's needed to drive it to full scale sound level.
If this level is not exceeded, nothing can break, no matter where the signal originates from.
This is about the output voltage that most home HiFi cd-players send.
There is no analog variable gain circuit built into Mobius, so levels far below this will not drive Mobius sufficiently.

 

[Deders]

In fact the world of audio signals is divided in three main groups:

Low Level 0.001V to 0.3V, low energy:
microphones, turn table pickups etc., all kind of low voltage and low energy signals, often before being electronically amplified.

Line level, Voltage 0.3V - 20V, low energy, typically 2V:
intercontacts between different electronic audio devices, outputs from cd-players, cassette-decks and tape machines, interconnect between preamplifier and power amplifier, interconnects in recording studios, even the analog telephone line counts into that and gave the signal its name.

Power level, Voltage 0.1V to 100V, energy/power 0.001W to multiples of 10,000W:
all kind of signals originating from power amplifiers, intended to drive some kind of speakers or headphones.
This one has the widest variety of voltage and energy transmission, because it's an enormous difference if you want to drive sensitive InEars, or a big PA system in a show.
For a sensitive InEar 1/1000 of a Watt might be sufficient for earhurting levels, on a PA system for a bigger audience 100,000W may be necessary to serve the same purpose.
As can be seen, there is quite some overlap with the line level voltages, and such power amplifiers can be used as line drivers too, as long as the receivers maximum healthy voltage is not exceeded.
The problem might be, that power amplifiers, in contrary to most dedicated line drivers, are capable of supplying sufficient energy to literally toast electronic parts.

Mobius Aux input works with line level, and it's only the voltage that counts. It does not draw a significant amounts of energy out of the source (it has a high input impedance).
According to my measurements Mobius can handle up to 1.8V without distortion, and and this is what's needed to drive it to full scale sound level.
If this level is not exceeded, nothing can break, no matter where the signal originates from.
This is about the output voltage that most home HiFi cd-players send.
There is no analog variable gain circuit built into Mobius, so levels far below this will not drive Mobius sufficiently.

Thank you for a very informative post, it does raise a few questions for me.

I used to own a (several in fact) Sony NWZ-A3000 MP3 players which had the ability to switch the output from headphone to line out. If my earbuds were plugged in (albiet very low powered compared to most that you'd find on here) when line out was selected, they would be very distorted. It would also drain the battery much quicker.

Would a normal phone's headphone out count as a lineout or headphone out?

I'm currently using a LG V30 phone which has a built in amp that auto selects how much to output depending on the resistance it comes up against.

If it detects < 50 Ohm, it switches to "Normal device mode"; between 50 Ohm and ~ 750 Ohm, it switches to "High impedance mode"; above ~ 750 Ohm, it switches to line out.

For the Mobius it switches to Normal device, but If I plug in a headphone amp or similar, it selects line out. There is a trick to force it to line out with an extension cable (I haven't got one yet) Would this be better for the Mobius?

When I plug it straight in the volume is much lower than it is via USB or Bluetooth, this is the same across multiple devices.

 

[acia]

Thank you for a very informative post, it does raise a few questions for me.

I used to own a (several in fact) Sony NWZ-A3000 MP3 players which had the ability to switch the output from headphone to line out. If my earbuds were plugged in (albiet very low powered compared to most that you'd find on here) when line out was selected, they would be very distorted. It would also drain the battery much quicker.

Would a normal phone's headphone out count as a lineout or headphone out?

I'm currently using a LG V30 phone which has a built in amp that auto selects how much to output depending on the resistance it comes up against.

If it detects < 50 Ohm, it switches to "Normal device mode"; between 50 Ohm and ~ 750 Ohm, it switches to "High impedance mode"; above ~ 750 Ohm, it switches to line out.

For the Mobius it switches to Normal device, but If I plug in a headphone amp or similar, it selects line out. There is a trick to force it to line out with an extension cable (I haven't got one yet) Would this be better for the Mobius?

When I plug it straight in the volume is much lower than it is via USB or Bluetooth, this is the same across multiple devices.

try usb-c to usb-c to your v30. may need to switch to 2ch or high-res if 7.1 doesn't work.

for ldac, same quality as high res.

 

[Deders]

try usb-c to usb-c to your v30. may need to switch to 2ch or high-res if 7.1 doesn't work.

for ldac, same quality as high res.

Ok I've got USB working. I was having trouble before because the USB-C cable that comes with it isn't OTG, but I found an adapter that is, I'm glad I've got this working.

But what If I wanted to use this in a situation that didn't have USB or Bluetooth available? @The Socialist Nerd mentioned his Pono player, and since finding out that headphones can play from Bluetooth and line in simultaniously I've been toying with the idea of using it to jam along to tunes with my guitar.

I could potentially run the 560 Ohm line out from my attenuator that sits in between my guitar amp and speakers (It can safely soak up the load from the amp so I don't need to have the speakers on) to the line in on the mobius, or I could use a headphone amp depending on what's the safest load for the Mobius, and then bluetooth the tracks I wanted to jam along to at antisocial hours.

 

[KaiSc]

Thank you for a very informative post, it does raise a few questions for me.

I used to own a (several in fact) Sony NWZ-A3000 MP3 players which had the ability to switch the output from headphone to line out. If my earbuds were plugged in (albiet very low powered compared to most that you'd find on here) when line out was selected, they would be very distorted. It would also drain the battery much quicker.

Would a normal phone's headphone out count as a lineout or headphone out?

I'm currently using a LG V30 phone which has a built in amp that auto selects how much to output depending on the resistance it comes up against.

If it detects < 50 Ohm, it switches to "Normal device mode"; between 50 Ohm and ~ 750 Ohm, it switches to "High impedance mode"; above ~ 750 Ohm, it switches to line out.

For the Mobius it switches to Normal device, but If I plug in a headphone amp or similar, it selects line out. There is a trick to force it to line out with an extension cable (I haven't got one yet) Would this be better for the Mobius?

When I plug it straight in the volume is much lower than it is via USB or Bluetooth, this is the same across multiple devices.

iPhone's analog headphone outs deliver 1.0V and about 0.05W (EU crippled version 0.5V / 0.015W), so they can count as both, headphone amp and line out.
iPhone is capable of driving Mobius Aux In into ear-damaging levels, but not to max (-6dBFS International-, -12 dBFS EU-version; FS=full scale).
BTW: there is a well working adapter (Apple CCK) for digital connection available for iPhone.
I cannot comment on the wide variety of other phones or music players, I have no figures.

This is what I found according the LG V30 (from reddit):
... V30 will use "regular" amp mode until 50+ohm headphones are plugged in. In regular mode it outputs about 0.75Vrms, "aux" mode is ~1vrms, and high impedance mode is 2vrms. ...
... You can trigger high impedance mode on your LG V30 if your headphones have a removable cable. First remove the cable from your headphones and then plug the cable into your mobile phone. That will trigger high impedance mode.

LG V30's "Hi impedance mode" is what you want with Mobius, because Mobius' Aux input has an input impedance of 4.3kOhm (measured by me) and needs a voltage of 1.8V for Full Scale Drive.
I have no idea why that does not work automatically with the V30 (it should), so you'll need to use the mentioned workaround.

Ok I've got USB working. I was having trouble before because the USB-C cable that comes with it isn't OTG, but I found an adapter that is, I'm glad I've got this working.

But what If I wanted to use this in a situation that didn't have USB or Bluetooth available? @The Socialist Nerd mentioned his Pono player, and since finding out that headphones can play from Bluetooth and line in simultaniously I've been toying with the idea of using it to jam along to tunes with my guitar.

I could potentially run the 560 Ohm line out from my attenuator that sits in between my guitar amp and speakers (It can safely soak up the load from the amp so I don't need to have the speakers on) to the line in on the mobius, or I could use a headphone amp depending on what's the safest load for the Mobius, and then bluetooth the tracks I wanted to jam along to at antisocial hours.

@KMann : I can only guess what voltage would kill Mobius Aux input. This is a figure that AUDEZE should publish! Please!
In fact designing the Aux Input in a way that it is breakable is an oversight IMO, there are easy ways to avoid this (series input resitor + clamping diodes). I guess, there is something like that built in, but might be a bit too weak for a very strong signals, so the warning.

The safe way working with Mobius' Aux input is:
- bring Mobius volume full up.
- SLOWLY dial up the level control of your source until a bit more than the desired volume is reached.
- dial back Mobius volume a bit, to the desired level.
- be careful and avoid to bring up the source volume control beyond the determined level.

@KMann There probably is a safety margin beyond the point of distortion, but how much only AUDEZE does know?!

 

[Deders]

iPhone's analog headphone outs deliver 1.0V and about 0.05W (EU crippled version 0.5V / 0.015W), so they can count as both, headphone amp and line out.
iPhone is capable of driving Mobius Aux In into ear-damaging levels, but not to max (-6dBFS International-, -12 dBFS EU-version; FS=full scale).
BTW: there is a well working adapter (Apple CCK) for digital connection available for iPhone.
I cannot comment on the wide variety of other phones or music players, I have no figures.

This is what I found according the LG V30 (from reddit):
... V30 will use "regular" amp mode until 50+ohm headphones are plugged in. In regular mode it outputs about 0.75Vrms, "aux" mode is ~1vrms, and high impedance mode is 2vrms. ...
... You can trigger high impedance mode on your LG V30 if your headphones have a removable cable. First remove the cable from your headphones and then plug the cable into your mobile phone. That will trigger high impedance mode.

LG V30's "Hi impedance mode" is what you want with Mobius, because Mobius' Aux input has an input impedance of 4.3kOhm (measured by me) and needs a voltage of 1.8V for Full Scale Drive.
I have no idea why that does not work automatically with the V30 (it should), so you'll need to use the mentioned workaround.

@KMann : I can only guess what voltage would kill Mobius Aux input. This is a figure that AUDEZE should publish! Please!
In fact designing the Aux Input in a way that it is breakable is an oversight IMO, there are easy ways to avoid this (series input resitor + clamping diodes). I guess, there is something like that built in, but might be a bit too weak for a very strong signals, so the warning.

The safe way working with Mobius' Aux input is:
- bring Mobius volume full up.
- SLOWLY dial up the level control of your source until a bit more than the desired volume is reached.
- dial back Mobius volume a bit, to the desired level.
- be careful and avoid to bring up the source volume control beyond the determined level.

@KMann There probably is a safety margin beyond the point of distortion, but how much only AUDEZE does know?!

Thanks, again very useful info.

I had assumed that the cable trick would select the line out mode, not the high impedence mode because having no connection at one end would be more than 750 Ohm resistance. I will have to find a suitable cable to test. I have an app that tells me which mode it is using at any given time. Would line out still be ok? If it's expecting higher resistance is it likely to distort?

I would have thought being a built in DAC that it would accept lower impedence signals and work like a headphone amp. Oh well.

Edit: just tested, can confirm it selects line out with an extension cable. Not tried the Mobius yet.

Edit2: so 4.3kOhm is 4300 Ohm. Is this high for most equipment? Does measuring with the Mobius on and set to Aux make a difference?

 

[KaiSc]

Thanks, again very useful info.

I had assumed that the cable trick would select the line out mode, not the high impedence mode because having no connection at one end would be more than 750 Ohm resistance. I will have to find a suitable cable to test. I have an app that tells me which mode it is using at any given time. Would line out still be ok? If it's expecting higher resistance is it likely to distort?

I would have thought being a built in DAC that it would accept lower impedence signals and work like a headphone amp. Oh well.

Edit: just tested, can confirm it selects line out with an extension cable. Not tried the Mobius yet.

Edit2: so 4.3kOhm is 4300 Ohm. Is this high for most equipment? Does measuring with the Mobius on and set to Aux make a difference?

4.3kOhm or 4300Ohm means Mobius does not challenge the source, the source has not to deliver much energy to drive Mobius. What Mobius needs is quite some voltage (1.8V) for being driven full scale (for maximum possible loudness), more than most portable devices deliver.

Most portable devices are built to drive low impedance headphones, this means they put out low voltage (typically 0.2-0.5V max.), but are able to deliver some amount of energy ("current", mA).
A typical line output can deliver higher voltage (typically 2V), but is not able to deliver enough current to drive low impedance headphones.

If people are interested here I would dig deeper into this Voltage, Current, Impedance, ... thing.
It's not that complicated, and all calculated with elementary school mathematics.

 

[Deders]

4.3kOhm or 4300Ohm means Mobius does not challenge the source, the source has not to deliver much energy to drive Mobius. What Mobius needs is quite some voltage (1.8V) for being driven full scale (for maximum possible loudness), more than most portable devices deliver.

Most portable devices are built to drive low impedance headphones, this means they put out low voltage (typically 0.2-0.5V max.), but are able to deliver some amount of energy ("current", mA).
A typical line output can deliver higher voltage (typically 2V), but is not able to deliver enough current to drive low impedance headphones.

If people are interested here I would dig deeper into this Voltage, Current, Impedance, ... thing.
It's not that complicated, and all calculated with elementary school mathematics.

So the higher the Ohms the less resistance? Interesting.

I for one would like to know more about this. I know that Watts = Volts x Amps and that it's usually the amps that kills you.

I was intrigued to see how very high voltages were being used in my 100W tube guitar amp to make the sound, but the killawatt reading for watts at the wall didn't seem to be changing all that much like it would for other electronics.

 

[sebas388]

hi, is there a new firmware available? i read somewhere that there was one, but it got pulled back to fix some stuff. is it available right now?
sidenote, i think its awesome that audeze keeps working on these stuff; not only its exiting to think that there is more to come, it also talks about the company dedication to great products.

 

[KaiSc]

So the higher the Ohms the less resistance? Interesting.

I for one would like to know more about this. I know that Watts = Volts x Amps and that it's usually the amps that kills you.

I was intrigued to see how very high voltages were being used in my 100W tube guitar amp to make the sound, but the killawatt reading for watts at the wall didn't seem to be changing all that much like it would for other electronics.

(Electrical) Resistance is a physical property, and is measured in Ohm,
As the name suggests, the higher the Resistance (more Ohm) the less Current (less Ampere) does flow, because the Resistance inhibits the electrons to move.
I will prepare a posting explaining all in simple words, Wikipedia, as usual in those type of things, is too complicated for bigginners.
Give me a bit of time, I need to translate (I'm German) correctly.

Here's an appetizer:

As a start, there are only 3 basic physical properties that are of interest for us:
- (Electrical) Tension (even called Voltage) U, measured in Volt, V.
The force electrons create, waiting for a way to move.
- (Electrical) Current I measured in Ampere, A.
The number of electrons moving through a conductor.
- (Electrical) Resistance R measured in Ohm, Ω.
The amount of braking the moving electrons, transforming electron movement into heat.

If you know 2 of the values the remaining one and other, dependant values can be calculated:

- (Electrical) Power P measured in Watt, W.
Power floating through a transducer is responsible for creating the loudness.
Power happens at the very moment you look at a system, momentary only.

- (Electrical) Energy E measured in Watt x Seconds, Ws or in Joule, J.
Energy is Power happening over a period of time.
This one is, although people like to use the word Energy, less important for our purpose.
We're not interested in how much Energy headphones have consumed over a period of one month e.g.

- (Electrical) Impedance Z, measured in Ohm, Ω.
Impedance is a special version of Resistance that takes into account that, for non-constant voltages (e.g. alternating current, AC, like our music signal) it can happen that Current and Voltage might not be sycronised, one might be time-shifted relatve to the other.
This always happens when reactive loads (loads that can store energy) like dynamic headphones come into play,
Therefore this is even called Reactance.
We mostly use the word Impedance to express that we expect the Resistance (of headphones e.g.) not to be the same for different Frequencies.
For Mobius Aux input this is not the case, it's simply pure resistive 4300 Ω, we can ignore impedance.


In our next lesson we will learn how to calculate one out of others, using simple math.
Don't hesitate to ask.

Wikipedia uses the water hose analogy.
Although quite descriptive I don't like this approach.
I think it's better to understand the real thing (electron movement) without any abstraction inbetween.

If you see any mistranslation please tell me, it's sometimes hard to find the right one.

 

[Deders]

@KaiSc So you are saying there are 2 different things we measure in Ohms, Reactance and Resistance, and because all the electronic signals are in time with each other in the Mobius, we are only dealing with resistance?

I may have had some experience with electronic signals that haven't been in sync when connecting 2 power supplies to a computer. Unless you sync or isolate the signal, someting is going to go bang.

For what it's worth I quite like the water pipe analogy, but I've never heard how resistance or reactance fits into it.

 

[KaiSc]

@KaiSc So you are saying there are 2 different things we measure in Ohms, Reactance and Resistance, and because all the electronic signals are in time with each other in the Mobius, we are only dealing with resistance?

I may have had some experience with electronic signals that haven't been in sync when connecting 2 power supplies to a computer. Unless you sync or isolate the signal, someting is going to go bang.

For what it's worth I quite like the water pipe analogy, but I've never heard how resistance or reactance fits into it.

The difference between Resistance R and Impedance Z is, Impedance contains a Real Part R and an imaginary part i.
R is the part that creates Power; i is the part where Voltage U and Current I are out of Phase and don't create Power.
As P= U x I, if U and I don't come together (antiphase) the result is zero, no Power, "imaginary".
This means an amplifier feeding an Impedance has to (partly) deliver voltage and current that does not result in sound level.

DC power supplies - can or cannot be used in parallel, depending on the construction. Standard computer PSUs cannot, they need to be constructed for the purpose of redundancy.
AC power supplies cannot, except if great measures are taken to synchronize them - think power plants.

Remark: I've added the substitute letters for the terms in my former post.

 

[emba4]

I love the level of technicality in these replies. Nothing dumbed down just solid educational posts. You guys are awesome

 

[Kerdh]

Hey guys. Tried to connect through bluetooth to my Sony Bravia and the TV can't find the Mobius. Is it even just possible? The pairing works fine with my smartphone for example (for the two of them, the TV and the Mobius).

 

[Kerdh]

And I just found a test from a French laboratory - lesnumeriques - with an excellent conclusion: 5/5.

https://www.lesnumeriques.com/casque-audio/audeze-mobius-p43627/test.html
https://www.lesnumeriques.com/casqu...rtuel-casque-gaming-audeze-mobius-n84377.html