[SilverEars]

That's correct. Unless you get a completely transparent (wire with gain) amp then you don't need to worry how the amp pairs with your source

I'm actually looking into an amp called "the wire"  Not sure how well it performs, but they describe it like just wire with gain.  

 

[burtomr]

  I'm actually looking into an amp called "the wire" 

 
Interesting, can we have a link please...?

 

[SilverEars]

http://www.diyaudio.com/forums/headphone-systems/179298-wire-ultra-high-performance-headphone-amplifier-pcbs.html
 
http://www.diyaudio.com/wiki/The_Wire_Headphone_Amp_Build_Wiki
 
Hi Guys,

I just finished building my latest headphone amplifier project, and this one is definitely worth sharing with the community. After a few prototypes, I went ahead and had some PCB's made, and there are plenty extra available if people are interested.

I basically wanted a headphone amplifier that was as close as could be to a wire with current gain. I didn't want it to impart anything at all to the source signal. That led me to the following design criteria:

- Perfectly flat FR from DC to over 100kHz
- No phase shift from 0-100kHz
- No capacitors (except for PSU)
- Extremely low harmonic distortion
- Extremely low IM distortion
- Extremely low noise floor
- Ability to drive down to 4 ohms with no load dependence
- Enough voltage swing to drive any reasonable headphone set.
- Excellent input CMRR
- Simple circuitry using the best parts available.

I needed a balanced input, and wanted to use a standard 1/4" jack for the output.

The resulting amplifier is basically an instrumentation amp using three LME49990 op-amps and an LME 49600 buffer nested into the last stage. These parts represent the absolute best you can get for this sort of application. I used all 0.1% Susumu thin film resistors, and all X7R ceramic bypass capacitors placed directly on the supply pins. Bulk caps are all solid polymer for the absolute lowest ESR and best HF performance. Layout was optimized for short signal length, low noise and low crosstalk.

The circuit provides differential input, or the option to ground one phase and drive the circuit with an SE input. Gain is set to 1, but can easily be changed to pretty much anything with just two resistors It runs on +/-5VDC up to +/- 15VDC and has enough drive to run anything you can throw at it.

As for sound, having a DC coupled amplifier makes for some of the most stunning bass I have ever heard. I'm driving a pair of Denon AH-D2000 headphones, and there's a world of difference between this amplifier and every other source I have ever tried when it comes to performance below 100Hz. It has incredible impact, depth and cleanliness. In the midrange and top end, it passes on the characteristics of the source like nothing I have ever heard. I've driven it with an Aikido linestage, a BZLS, straight from a DAC and a multitude of other devices, and all you hear is the device driving it. I now use this setup as my primary means of evaluating all preamps and sources since nothing else I have ever used even comes close to exposing the true nature of the sources like this circuit does. It's honestly like it's not even there... hence the name.

I've attached some pictures of the finished product below, and I'll follow up with some measurements done on an Audio Precision. Schematic to follow also.

 

[AnakChan]

Looks like Japan is (kind of) doing their own thing again with iBasso. Hibino, iBasso's distributor in Japan is bringing in the DX90j. I'm going to need a better translator than Google but it seems it's the same spec as the international DX90 (i.e. same DAC, OpAmp, etc.) but supposedly with higher quality (content?) silver soldering for almost $130 more at Y54,500 (ok no shipping fees required in Japan so maybe $110 more then).

Further news here about the DX90j (in Japanese) :-
http://av.watch.impress.co.jp/docs/news/20140627_655456.html

 

[lin0003]

  Looks like Japan is (kind of) doing their own thing again with iBasso. Hibino, iBasso's distributor in Japan is bringing in the DX90j. I'm going to need a better translator than Google but it seems it's the same spec as the international DX90 (i.e. same DAC, OpAmp, etc.) but supposedly with higher quality (content?) silver soldering for almost $130 more at Y54,500 (ok no shipping fees required in Japan so maybe $110 more then).

Further news here about the DX90j (in Japanese) :-
http://av.watch.impress.co.jp/docs/news/20140627_655456.html

Any reason why the output impedance is 16 ohms? 

 

[SilverEars]

  Any reason why the output impedance is 16 ohms? 

I'm guessing they mean headphone load of 16ohms, then they go into power output at different gain levels at 16ohm load.
 
The headphone output (16Ω at the time) 115mW × 2ch (LO), 275mW × 2ch (Hi).

 

[headwhacker]

And while I'm here....

Just ordered DX90, but I already have one gripe with it  - I don't understand the iBasso's logic of placing HO on the bottom of the DAP  . I bought it to serve as a portable player so it will spend most of its life in my pocket. To prevent it to sit on and put pressure on the straight ended headphone jack I can of course put it in my pocket upside (display) down. No big deal? Yes it is, because now my Volume UP button now sits wrong way! One would just assume that the bottom button will reduce the volume. Not so in iBasso universe it seems.

I know, it may sound ridiculous to some, but I've been using DAPs (iRiver iHP1xx) for quite a while and I know how often I have to slightly adjust the volume up or down by touch, without taking the thing out of my pocket. I also know that eventually I'll get used to this anomaly, but why? It would be my guess that 99% of portable devices that can have a headphone output would have it placed at the top.

I also suspect that I may belong to minority group of DAP users who carry their DAP in their pockets....

[/end rant]

Cheers.

I carry DX90 in my pocket a lot. It doesn't bother me the HO is at the bottom at all. It is actually natural IMO. When you hold a DAP in your hand while looking at screen you will have to turn it up side down anyway when you swing your hand going into the direction of your pocket. I don't have to flick my hand to rotate the DAP before actually putting it inside my pocket.

With the iphone I sometimes forget the HO is at the top. When I put it in my pocket earphone plug is at the bottom. With several coins or debris in my pocket, when I pull the iPhone out of my pocket, those debris comes out when caught by the cable. It happened a few times, it is especially embarassing inside a train.

 

[Lad27]

^^
 
I'm with you that it is rather natural to put in the pocket that way, I just really dislike the idea of having the DAP resting on top of the straight connector. It is going to stuff the cable joint by putting too much bent force on the strainrelief. Right angle connector would alleviate this problem, but I don't have any cans fitted with such connector.
 
I deal with cables and connectors a lot in my profession and that just isn't good design IMO.

 

[nc8000]

iPhone5 onwards also have the ho at the bottom which I actually prefer

 

[Jensenchua]

I carry DX90 in my pocket a lot. It doesn't bother me the HO is at the bottom at all. It is actually natural IMO. When you hold a DAP in your hand while looking at screen you will have to turn it up side down anyway when you swing your hand going into the direction of your pocket. I don't have to flick my hand to rotate the DAP before actually putting it inside my pocket.

With the iphone I sometimes forget the HO is at the top. When I put it in my pocket earphone plug is at the bottom. With several coins or debris in my pocket, when I pull the iPhone out of my pocket, those debris comes out when caught by the cable. It happened a few times, it is especially embarassing inside a train.

 

iPhone5 onwards also have the ho at the bottom which I actually prefer

Yeah now all the Apple devices HO is at the bottom and is not bothering me too

 

[jamato8]

I always have the dap on its side in my pocket. I find this works best for me if the HO is on top or bottom. 

 

[robin1990]

  The DX90 is different, for USB, because the software developed for it makes it show up different than a plug and play. So drivers have to be developed to go along with the custom software being used by the DX90. This is the explanation I got some time back from iBasso and makes sense to me, though I would like a driver for my Mac. :^). 

 

Hi,
We are trying to develop the Mac drive. But we are not sure if we can complete it.
 
Sincerely
iBasso Audio

 
 
Get your finger crossed until it breaks. lol

 

[goodvibes]

  And while I'm here....
 
Just ordered DX90, but I already have one gripe with it  - I don't understand the iBasso's logic of placing HO on the bottom of the DAP 

. I bought it to serve as a portable player so it will spend most of its life in my pocket. To prevent it to sit on and put pressure on the straight ended headphone jack I can of course put it in my pocket upside (display) down. No big deal? Yes it is, because now my Volume UP button now sits wrong way! One would just assume that the bottom button will reduce the volume. Not so in iBasso universe it seems.
 
I know, it may sound ridiculous to some, but I've been using DAPs (iRiver iHP1xx) for quite a while and I know how often I have to slightly adjust the volume up or down by touch, without taking the thing out of my pocket. I also know that eventually I'll get used to this anomaly, but why? It would be my guess that 99% of portable devices that can have a headphone output would have it placed at the top.
 
I also suspect that I may belong to minority group of DAP users who carry their DAP in their pockets....
 
[/end rant]
 
Cheers.

Ipods have had their jacks on the bottom forever. In a pant pocket. upside down gives the same hand orientation as holding it up in front of your face. I get what you're saying but I have devices with both orientations and don't have a preference which is all it amounts to.

 

[nc8000]

iPod Classic never had the ho on the bottom and iPhone only since 5. Touch I can't remember

 

[Dopaminer]

Plus the digital out is on the top, which is where you want it if the dx90 is on your desk hooked up to your DAC.  The bottom is definitely the correct place for the HO in my opinion. . .