[AlanHell]

  It doesn't have a toroidal transformer but impulse one.
I'm not sure about amplification if it is A or D class...

Cannot be A...... The unit been running for a whole a day is cooler than the volume nob of my class A amp...............

 

[jagwap]

  It doesn't have a toroidal transformer but impulse one.
I'm not sure about amplification if it is A or D class...

It is Class A, which should get cooler when played hard, as it is sending the power out of the box into the headphones.

 

[AlanHell]

  It is Class A, which should get cooler when played hard, as it is sending the power out of the box into the headphones.

But I tough Class A has a theoretical efficiency value of 50%.
Meaning at least 50% of them goes to heat or other useless stuff~~~~
 
So not sure what you mean by "get cooler when played hard".
 
P.S.
I suck at analogs, so please be patient with my ignorance.
 
I though when you power on the amp, it already starts "amping" with constant gain weather or not you are sending the signal. The volume nob is just added resistance that reduce the "full gain" to less power so it does not hurt your ear? No matter what happened, the power been send out by the amp is always constant which the efficiency between the transformer and the amplifier circuit is always the same less than 50%?

 

[ALRAINBOW]

No class draws about the same power weather you are using it it not
It is like this till about 50 or more and slowly goes into AB
In theory it shaw draw the same no matter how much you use or not
Al

 

[jagwap]

What you are describing is heavily biased class AB, not pure class A.
 
Class A means all the current which could be required by a transducer is flowing through the output stage, all the time until required.  The output stages never switch off as in class B or class AB.
 
So when some of the current is directed to the headphones, the output stage gets a little cooler.  Probably not noticably in the case of headphones.

 

[germanium]

 
But I tough Class A has a theoretical efficiency value of 50%.
Meaning at least 50% of them goes to heat or other useless stuff~~~~
 
So not sure what you mean by "get cooler when played hard".
 
P.S.
I suck at analogs, so please be patient with my ignorance.
 
I though when you power on the amp, it already starts "amping" with constant gain weather or not you are sending the signal. The volume nob is just added resistance that reduce the "full gain" to less power so it does not hurt your ear? No matter what happened, the power been send out by the amp is always constant which the efficiency between the transformer and the amplifier circuit is always the same less than 50%?

 
Class A is only about 40% efficient at best & that is if you are using solid state. Expect that to drop below 30% for vacuum tubes because of their heater circuits required for them to operate.
 
A tube amp that a  friend of mine built was 37% efficient before taking into account the heater circuit but was only 21% efficient when you added the power draw of the heaters. The heaters drew 25 watts per tube for 50 watts per channel & 100 watts total just to heat the power tubes on a 25 watt per channel amp. Each power tube drew 33.2 watts for 66.4 watts per channel idle current power draw. This comes to 116.4 watts power draw per channel to get 25 watts pure class A power output to the speakers.

 

[jagwap]

However, a look inside shows it is not a class A amplifier in the DVDA800...

 

[Bartez75]

   
Class A is only about 40% efficient at best & that is if you are using solid state. Expect that to drop below 30% for vacuum tubes because of their heater circuits required for them to operate.
 
A tube amp that a  friend of mine built was 37% efficient before taking into account the heater circuit but was only 21% efficient when you added the power draw of the heaters. The heaters drew 25 watts per tube for 50 watts per channel & 100 watts total just to heat the power tubes on a 25 watt per channel amp. Each power tube drew 33.2 watts for 66.4 watts per channel idle current power draw. This comes to 116.4 watts power draw per channel to get 25 watts pure class A power output to the speakers.

But what a sweet power it then

 

[LFC_SL]

On a final note, it is a shame that are no Auralic dealers that I know of in London. 

Pedro

The website says there are two Auralic dealers not too far outside M25, though it would be easiest if my local retailer got in touch with the UK distributor...

 

[AlanHell]

 
Class A is only about 40% efficient at best & that is if you are using solid state. Expect that to drop below 30% for vacuum tubes because of their heater circuits required for them to operate.
 
A tube amp that a  friend of mine built was 37% efficient before taking into account the heater circuit but was only 21% efficient when you added the power draw of the heaters. The heaters drew 25 watts per tube for 50 watts per channel & 100 watts total just to heat the power tubes on a 25 watt per channel amp. Each power tube drew 33.2 watts for 66.4 watts per channel idle current power draw. This comes to 116.4 watts power draw per channel to get 25 watts pure class A power output to the speakers.

 


So, basically it cannot be a class A and cannot be "cooler" when play hard~~~~

Thanks

 

[ruthieandjohn]

New discovery on amp temperature just reported...
 

 

[jagwap]

It depends on the output stage.  If it is single ended triode (not the HDVD800 as there are no valves) then it will not run cooler.  But if it is a push pull output stage with the output stage set up as a constant current (like the original A1 from musical fidelity) then it can run cooler.
 
There are many different amplifier topologies in each class.
 
However the HDVD is not class A so this is moot.  It is a chip amp, all be it a very good one.

 

[Priidik]

 
It is a chip amp, all be it a very good one.

Do you know what's below the heatsink? And then, why so many opamps before it..

 

[jagwap]

Yes, under the heatsink are the four headphone amplifier channels, in the form of two dual channel chip amplifiers.
 
Before that is the opamp stage from the DAC which is acting as an I to V stage (converting the current out from the DAC to voltage).  The others are employed as unbalanced to balanced stages for the RCA/phono inputs, and balanced common mode rejection inputs, or balanced output stages.

 

[ruthieandjohn]

Bass question...
 
I JUST received my Sennheiser HDVD 800 DAC/amp, as well as the HD 800 headphones.  It sounds GREAT on .wav files played via USB port into the HDVD DAC, then amp, then HD 800 headphones.
 


Colorware-coordinated Sennheiser HD 800, HDVD 800, and FIAT Abarth for the best in on-the-road headphone listening!
 
Then I tried my bass test track, which happens to be an AAC (i.e. "iTunes" file at 256 kb/sec VBR) file.  Test track is "Throwback" by B.o.B. on album "Underground Luxury," where starting in the third verse, strong bass below 50 Hz (i.e. in the lowest octave of the piano) is played.
 
The bass sounded CLIPPED and SATURATED and DISTORTED!  It sounds similarly distorted on another headphone (Sennheiser HD 598) through the HDVD 800 amp instead of the HD 800 headphones.  So it was not the HD 800s.
 
I tried another song, Massive Attack's "Angel," coded in the same way.
 
Sub bass was again DISTORTED!
 
Neither are the least bit distorted when played on my iPod in the same format. 
 
I then tried iPod Lighening connector digital output to Sony PHA-1 DAC and amp to HD 800 headphones (PHA-1 actually decodes the digital stream from the iPod, not recreating an analog line out from a DAC in the connector as is sometimes the case).  Again, NO distortion.
 
I then went to the "Heartbeat" track of Chesky's Ultimate Headphone Demonstration Disk (pulses at first 50 Hz, then 40 Hz, then 30 Hz, then 20 Hz).  No problem, no distortion.
 
I then managed to find a lossless version of "Throwback" (Chinese site!). NO BASS DISTORTION!
 
So...
 
1)  Is it a characteristic of iTunes compression to distort very low bass, but you must have a powerful amp for it to be maintained at its original volume for the distortion to appear?
 
2)  Can you suggest a lossless song with strong subbass and where to find it so I can try that?
 
Thanks!