KG CFA3 headphone amp
Oct 29, 2020 at 11:22 AM Post #46 of 1,793
measured with the keithely 2015 high voltage thd meter and the james m king hpib software...

In Zero Feedback Mode with +/-24v power supplies, 16 watts rms balanced into 50 ohms with a Thd+N of <.006% 20hz to 20khz +0, -.01db 10 hz to 3.7Mhz +0,-3db
In SuperSymmetry mode with +/-24v power supplies, 16 watts rms balanced into 50 ohms with a Thd+N of <.003% 20hz to 20khz +0, -.02db 10hz to 300khz +0,-3db with 10db of feedback
 
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Oct 29, 2020 at 12:02 PM Post #47 of 1,793
measured with the keithely 2015 high voltage thd meter and the james m king hpib software...

In Zero Feedback Mode with +/-24v power supplies, 16 watts rms balanced into 50 ohms with a Thd+N of <.006% 20hz to 20khz +0, -.01db 10 hz to 3.7Mhz +0,-3db
In SuperSymmetry mode with +/-24v power supplies, 16 watts rms balanced into 50 ohms with a Thd+N of <.003% 20hz to 20khz +0, -.02db 10hz to 300khz +0,-3db with 10db of feedback

Wow, that's a lot more than I expected. I have never seen it posted anywhere but is there similar data for the SuSy Dynahi?
 
Oct 29, 2020 at 5:15 PM Post #48 of 1,793
So the zero feedback amp gets much closer to the rail voltages than does the various dynahi designs. If you boost the power supplies to +/-30v then the output power is very similar.​
zero feedback amp generates less heat for same output power.​
 
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Oct 29, 2020 at 6:01 PM Post #49 of 1,793
Thanks, Kevin.

That gels right along with how I hear things. Quite the powerful amplifier.
 
Oct 29, 2020 at 6:14 PM Post #50 of 1,793
measured with the keithely 2015 high voltage thd meter and the james m king hpib software...

In Zero Feedback Mode with +/-24v power supplies, 16 watts rms balanced into 50 ohms with a Thd+N of <.006% 20hz to 20khz +0, -.01db 10 hz to 3.7Mhz +0,-3db
In SuperSymmetry mode with +/-24v power supplies, 16 watts rms balanced into 50 ohms with a Thd+N of <.003% 20hz to 20khz +0, -.02db 10hz to 300khz +0,-3db with 10db of feedback

16W in 50 Ohms is 28.28V. Where do the extra volts come if the supply is +/-24VDC?
 
Oct 30, 2020 at 9:10 AM Post #51 of 1,793
balanced output.

single ended output is 40 volts peak to peak. balanced output is twice that, 80 volts peak to peak.
 
Nov 10, 2020 at 1:16 AM Post #53 of 1,793
Over the Beta22, yes. Over a Dynahi. Depends on the version. I also think you should consider what design parameters of CFA vs Dynahi. For planar drive, the CFA is pretty special.
If you're only using, say, an HD800, sure, still build the CFA with SuSy switch. :stuck_out_tongue:

That's a good point regarding the design. An NFB, current feedback amp will certainly be something different than what I have.

For the record, I have a slight preference for the Beta 22 over the Dynahi.
 
Nov 10, 2020 at 2:33 PM Post #54 of 1,793
You could also look at loading the CFA into a hybrid. @Dukei and I discussed this a bit but he's busy doing a CFA run and quite frankly, I'm really rather satisfied with the CFA and Pass to feel that lit urge.

You might even consider the B24.
 
Jan 13, 2021 at 7:56 AM Post #56 of 1,793
Bumping this thread because I have some downtime while I wait for some parts to be cleared by the customs.
Have 2 custom CFA projects on my table at the moment. The larger one is a 3U case while the smaller one is 2U. Roughly the same spec as my previous builds but both are going to have some uniqueness to them, which I will reveal when they are finished. :)
 

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Feb 17, 2021 at 3:00 PM Post #59 of 1,793
Way to take holiday @Dukei

Let's go! :grin:
 

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