Aspen Headphone Amp

[AndrewT]

Originally Posted by keantoken

with an AB amp, where it might cross over into B during low load impedances; but this isn't a problem with the current class A design.

a single ended ClassA amp will go into current clip. It cannot supply more than what the CCS is set to.

[lohk]

Can somebody pls explain the value of R3 in the latest SE schematic for me? Is it a pot to adjust the offset, or what does the value "1020.3" mean?
(Well, I might have missed a few posts already...)

I appreciate very much this discussions&develepments @this thread - thank you.

[lohk]

BTW, for an easy double blind listening test for audio files another add-on for the very versatile foobar player can be useful, the so called "ABX comparator". It is activated by the context menu /utils/ABX two tracks.

[AKSA]

Hi Lohk,

Nice to see you here!!

This is the precise value of resistor needed to achieve zero offset. In practice, it would simply be a 4K7 resistor supplying a blue LED, around 2.5V, with a 1K pot across it. The wiper would supply the bias voltage, suitably decoupled with a cap.

There is, of course, no readily available resistor of that size! However, even there were, the bias would still vary with applied voltage, so it's adviseable to have a voltage source in that position. An LED is useful, of course, as it gives a visual indication of operation.

Hugh

[Sheldon]

I assume the one earth connection at the input is something used in a sim? Bleeder resistor missing? Hard to generate a signal when it's shorted.

Is the virtual earth supply still contemplated?

Sheldon

[Nico Ras]

Anyone thought of using a simple three terminal voltage regulator as CCS, low component count and good noise rejection. And temperature stable.

[Nico Ras]

I forgot. And voltage independant

[lohk]

Thanks, Hugh.

As a proud owner of a new AKG K702 I am looking for a better amp anyway.
I do not know the price of these headphones overseas but here it is less than 400EUR, they are pretty unbeatable for that price.

[AKSA]

I assume the one earth connection at the input is something used in a sim? Bleeder resistor missing? Hard to generate a signal when it's shorted.

Yes, for the purpose of assessing loop gain you need to short out the input signal.

Is the virtual earth supply still contemplated?

But of course!

Hugh

[AKSA]

Nico, I prefer to use the MJE15031 with a led. Simple, and better bandwidth. Besides, current regulation is not too important here; you could replace the CCS with a resistor, as you did with the earlier SE CFP, and not see much quality degradation.

Hugh