[drez]

Ahh AKG again with the 3 pin single entry connector, this time Lemo instead of Mini XLR...

 

[nakedhand]

Thanks for taking the time to do this review. Very well written.
 
I can not wait to hear the K812

 

[Brooko]

   
Directly from the Little Dot MK IV pages...
 
Pre-Amplifier Output Impedance: 600 ohms
 
You will find upon opening the MK IV that the cables going to Line Out jacks and Headphone Out socket are both connected to the same traces on the board. 

 
So are you saying that there isn't any difference between output impedance on the line out and headphone out (ie - nothing else in the circuit to affect the 600 ohm??)
 
That would seem very strange to me - as damping factor would make it unusable for most headphones.  Are you sure there is nothing else in the circuit?

 

[calaf]

great review: well-researched, well-organized, and very well written. I feel I know a lot more about the K812 now.
 
I also appreciate your candour in admitting you can't hear a difference between aac256 and lossless (neither can I). After reading that, I knew I was going to enjoy  your write-up, and I did!

 

[zorin]

   
 
 
Directly from the Little Dot MK IV pages...
 
Pre-Amplifier Output Impedance: 600 ohms
 
You will find upon opening the MK IV that the cables going to Line Out jacks and Headphone Out socket are both connected to the same traces on the board. 

The impedance of T1's driver at the bass frequencies, centered on 100 Hz, is about 1400 Ohm [that's a lot] - 800 Ohm difference from the nominal T1's impedance of 600 Ohm at 1000Hz. That is the crux of the matter. An amp that can deal with 600 Ohm impedance might not be able to supply enough voltage to overcome 1400 Ohm and the bass will sound weaker and the tonality will be thinner. See the 'electrical impedance and phase' graph of T1 - the pink color impedance curve : http://www.innerfidelity.com/images/BeyerdynamicT1SN3964.pdf

 

[Jeff Y]

The K812 with the AK240 sounds amazing. You should give the pair a listen if you get a chance.

 

[TrollDragon]

   
So are you saying that there isn't any difference between output impedance on the line out and headphone out (ie - nothing else in the circuit to affect the 600 ohm??)
 
That would seem very strange to me - as damping factor would make it unusable for most headphones.  Are you sure there is nothing else in the circuit?

 
Not a single thing...
 
The image on the left is the top of the board, the three big VIA's (Solder Pad's) above the tube socket is where the cable solders on to the rear RCA Line Out jacks. The image on the right marked L - GND - R is the bottom of the board where the headphone socket wires connect to. These are the exact same VIA's and It is only a double sided board so there are no layers in the middle.
 
I couldn't believe it myself when I took my board out to make a schematic of the LD MK IV.
 

 

[Brooko]

Thanks TD
 
Well that would explain why the LD MKIV sounds so good with the T1 - but why does it still sound very good with other lower impedance cans - especially with potential overdamping?
 
Perhaps one to ask on the LD forums? 

 

[kman1211]

  Thanks TD
 
Well that would explain why the LD MKIV sounds so good with the T1 - but why does it still sound very good with other lower impedance cans - especially with potential overdamping?
 
Perhaps one to ask on the LD forums? 

Because dampening factor doesn't apply to all headphones equally. The K812 for example has quite a flat impedance vs frequency response, this basically means while it is affected some by dampening, its not going to be affected in the same way or degree as say the T1, HD 800, or HD 600 which have all large impedance bumps in the bass region while the K812 is quite flat in this region.
 

 

[62ohm]

  Because dampening factor doesn't apply to all headphones equally. The K812 for example has quite a flat impedance vs frequency response(with the treble being the area that changes the most in the impedance curve), this basically means while it is affected some by dampening, its not going to be affected in the same way or degree as say the T1, HD 800, or HD 600 which have all large impedance bumps in the bass region while the K812 is ruler flat in this region.

 
I wouldn't say ruler flat, but it is flatter than the HD800's impedance vs FR.

 

[kman1211]

   
I wouldn't say ruler flat, but it is flatter than the HD800's impedance vs FR.

True, I looked at it closer and corrected it, it's quite flat, but it isn't ruler flat. Orthos are pretty much ruler flat.

 

[62ohm]

The measurements from Tyll would suggest the impedance vs FR graph is not as flat as the one from headroom.
 
http://www.innerfidelity.com/images/AKGK812SN001130.pdf 

 

[Carlsan]

I don't think Tyll was very happy with the K812.
I own the T1, K812, hd800, as well as some other headphones.
I have to agree with the review, fairly spot on.
My biggest gripe with the K812, which is otherwise excellent, is with the cable. Single entry, no option to change to balanced.
With such good drivers, I just know that a balanced K812, with the right cables, would be a killer.
thanks again for the review.

 

[kman1211]

  The measurements from Tyll would suggest the impedance vs FR graph is not as flat as the one from headroom.
 
http://www.innerfidelity.com/images/AKGK812SN001130.pdf 

That is interesting. There is some differences in the two K812s he measured on the impedance vs FR graph as well. It's interesting because Tyll's measurements of the K712 impedance vs FR graph is quite similar to headrooms. But when the K812 is compared, it's a bit different. The graphs are set up a bit differently though. 

 

[62ohm]

  That is interesting. There is some differences in the two K812s he measured on the impedance vs FR graph as well. It's interesting because Tyll's measurements of the K712 impedance vs FR graph is quite similar to headrooms. But when the K812 is compared, it's a different story. Seems there is something weird going on with the K812.  

 
Probably the K812 is just not as consistent as other cans, which may explain few of the tantrums being thrown to the K812. It is also worth noted that there has been several cases where a channel of the K812 dies after some time, which is also a concern. That is actually why I bought a demo-unit of the K812, if it had managed to survive for more than 6 months I guess it would survive for longer. Plus it is much cheaper than a BNIB