[Maxvla]

So does that mean since we're using so little power it never switches? Electronics noob here.

 

[El_Doug]

To have 40 watts of Class A (which the RSA website used to say, but no longer claims), youd need probably 100 pounds of heatsinks - I'd love to know the point at which the amp goes into B myself
 
Quote:

So does that mean since we're using so little power it never switches? Electronics noob here.

 

 

[Steve Eddy]

Quote:

In this case with an opamp as powerful as the opa541, to bias the amplifier significantly into class A at the rail voltages ray has specified will generate all sorts of extra heat
and change the slew rate characteristics of the amplifier. Detailed high resolution pictures have been posted by skylab that show no presence of either active or passive
current sources necessary to accomplish this. Nor the extra heatsinking necessary to handle this.

 
Fair 'nuff. My point was simply that the device's datasheet's not going to tell you about the actual implementation of the device.
 
Quote:

The issue of using a current source to bias an opamp into class A is probably more of a red herring than one might expect, as it probably does more
harm than good.

 
Which is a whole other issue.
 
se
 
 
 
 
 

 

[Ray Samuels]

My web site has never been altered regarding the DarkStar. We have not up-dated it either as it has been the same since day one.
I have made it clear to everyone who has asked me including Mike from Headfonia, that the DarkStar is running in class A due to it's ample power of voltage swing & current capability.
Having four amps as powerfull as those used in the DarkStar teaming together in balanced mode to drive any headphones is like a walk in the park for the DarkStar.
The amp will not switch or cross to class B due to it's capability. This has been said to Mike & to every one who called me. Those who don't like it Don't Buy IT.
Read this...
Class AB is widely considered a good compromise for audio amplifiers, since much of the time the music is quiet enough that the signal stays in the "class A" region,
where it is amplified with good fidelity, and by definition if passing out of this region, is large enough that the distortion products typical of class B are relatively small.

 
Quote:

To have 40 watts of Class A (which the RSA website used to say, but no longer claims), youd need probably 100 pounds of heatsinks - I'd love to know the point at which the amp goes into B myself
 


 

 

 

[Beefy]

Quote:

The amp will not switch or cross to class B due to it's capability

Surely that depends on the load. How much class A bias / quiescent current is it running through the output stage?

 

[Steve Eddy]

Hello, Ray!
 
Quote:

I have made it clear to everyone who has asked me including Mike from Headfonia, that the DarkStar is running in class A due to it's ample power of voltage swing & current capability.
Having four amps as powerfull as those used in the DarkStar teaming together in balanced mode to drive any headphones is like a walk in the park for the DarkStar.
The amp will not switch or cross to class B due to it's capability.

 
Unfortunately an amplifier's voltage swing and current capability doesn't say anything about the amplifier's class of operation. A pure class B amplifier may have the same voltage swing and current capability as a pure class A amplifier. It's the biasing level of the output stage that determines how much power can be delivered in class A. Ideally, in a complimentary push-pull output stage, you can deliver twice the bias current before the device(s) on one side turn off, putting you in class B operation. So ideally, unless you're employing some external means of biasing up the output stage, and assuming that all of the OPA541's maximum quiescent current of 25mA is in the output stage, you'd be able to deliver 50mA into the load before switching to class B. Into a 50 ohm load, this would be about 63mW RMS.
 
se

 

[johnwmclean]

Quote:

Those who don't like it Don't Buy IT.
 

Companies and manufacturers should be able to withstand any scrutiny and stand by their products no matter if it’s a potential customer or not. People here have an active interest in what’s commercially available and benchmarks companies achieve. They have high demands for a very competitive industry, they critique products for the better of our hobby. Heaven forbid if this wall of defence was to vanish.
 
 

 

[Steve Eddy]

Quote:

Originally Posted by johnwmclean /img/forum/go_quote.gif
 
Companies and manufacturers should be able to withstand any scrutiny and stand by their products no matter if it’s a potential customer or not. People here have an active interest in what’s commercially available and benchmarks companies achieve. They have high demands for a very competitive industry, they critique products for the better of our hobby. Heaven forbid if this wall of defence was to vanish.

 
But a wall of defense against what exactly?
 
se

 

[johnwmclean]

 
Quote:

 
But a wall of defense against what exactly?
 
s

 
I'd say you've done a fair amount of contribution yourself Steve, challenging AMBs 3 channel design comes straight to mind. 
 
Defense against poor design implementation and component choice. For example Headrooms adoption of the 2 x 3 pin XLR for headphone balanced output, over the 4 pin. You know that one Steve. A very bad example with cataustrophic consequences being the Singlepower debacle.
 
Shrugging of the hard questions with the "If you don't like it don't buy it" line in response to El_Dougs comment is appalling from a companies perspective.
 
 
 
 
 

 

[TheWuss]

john - a simple question for you.  have you heard the dark star?

 

[johnwmclean]

     Quote:

john - a simple question for you.  have you heard the dark star?

 
Simple but nothing to do with the discussion at hand, I frankly don’t see the point. Is there a point?

 

[grokit]

That sounds like a no.

 

[musicman59]

What really matters the most to us as audiophiles? Just the design or the actual enjoyment of the sound?
My personal vote is for what actually makes feel good and smile which is the enjoyment of the sound.

 

[TheWuss]

Quote:

 
Is there a point?

What I suppose I mean is that the man has answered the inquiries about his amp design.
 
And if you and Spritzer and Gilmore all want to continue to challenge the legitimacy of Ray's design, the burden of proof is now upon you.
 
The headphone world needs your investigative minds. 
But continuing this line of discussion in this thread isn't getting anyone anywhere.
 
So, go disect a Dark Star.  Run calculations.  Do whatever it takes.
 
Come back with something clear and concise.
 
Until then, your discussion carries no weight, and contributes nothing to this thread.
And certainly doesn't carry any weight vis-a-vis those who have heard the amp.
 
 

 

[Pars]

^ which part of 25mA bias, 63mW into 50 ohms before switching out of Class A didn't you understand? And the 25mA is the MAX value from the datasheet... 20mA is TYPICAL.