[Sko0byDoo]

DIY 45/2A3 SE amp.  Auto-bias with Lundahl output/Electra-Print interstage.  Regulated DC filaments for output (AC for input).  Six selectable output impedances.  Separate amp and power chassis (not shown):
 

 

 

 

[DutchGFX]

I'm in the process of building my own 2A3/45 SE amp, cathode bias as well, but no selectable output impedance, as the transformers are so expensive.

Curious as to what B+ voltage and Cathode resistors you used?

 

[Klechty]

  Kerry thanks for the encouragement.
 
The knob was made by a head-fier from Estonia. Engraving is his specialty. His work is impeccable. A better picture of my knob is in his gallery on his website.
 
viljomarrandi.com

The knob is absolutly amazing , a piece of art ; i would love to see it on my amp 

 

[Zashoomin]

  DIY 45/2A3 SE amp.  Auto-bias with Lundahl output/Electra-Print interstage.  Regulated DC filaments for output (AC for input).  Six selectable output impedances.  Separate amp and power chassis (not shown):
 

 

 

Love the point to point.  I wish I had the balls to try point to point as well.  Very lovely amp.  how does it sound?

 

[Sko0byDoo]

  Love the point to point.  I wish I had the balls to try point to point as well.  Very lovely amp.  how does it sound?

Thanks for the compliment.  It may sound crazy, but 275-ohm output to the HD800 sounds amazing.

 

[Zashoomin]

  Thanks for the compliment.  It may sound crazy, but 275-ohm output to the HD800 sounds amazing.

I don't think it sounds crazy at all.  275 is a bit high(I think), but for the 300ohm HD800 it doesn't sound that insane.  I mean if it sounds good, it sounds good.  

 

[joeyjojo]

  Thanks for the compliment.  It may sound crazy, but 275-ohm output to the HD800 sounds amazing.

 
Interesting. A damping factor of 1.09 is miserably low. I wonder if it sounds better to you because the flabbyness of the amp cancels out the precision of the headphones

 
Nice craftsmanship all the same.

 

[Sko0byDoo]

   
Interesting. A damping factor of 1.09 is miserably low. I wonder if it sounds better to you because the flabbyness of the amp cancels out the precision of the headphones

 
Nice craftsmanship all the same.

 
Thanks.  The amp got 5 other, lower output impedances and I've tried them all.  The low damping brings out the bass booming in the 800. 

 

[00940]

I cannot resist posting a pic of an amp in progress. It's kind of the opposite of my most recent project (a small usb dac-amp). It's a rebuild of this amp in order to use some parts I had stashed around. 
 
Ridiculously big caps ? Check.
Ridiculously big stepped attenuator ? Check.
Ridiculously big knob ? Check.
Ridiculously low power ? Check.
 

 

 

[funch]

Sounds perfect to me. 

 

[muskyhuntr]

Completed pictures of my KSA5.  I have only listened to it for a short time but so far it sounds great.  Bass seems to be especially well controlled.
 

 

 

 
Me

 

[vixr]

  Completed pictures of my KSA5.  I have only listened to it for a short time but so far it sounds great.  Bass seems to be especially well controlled.
 

 

 

 
Me

WOW! That's AWESOME!!!

 

[Mullet]

As always Musky your builds are immaculate. I've heard from another long-time head-fier, that he's tried a lot of headphone amps and he keeps on going back to the KSA-5. He has one of the original Krells, not the Klone. I have the boards, so eventually when money isn't so tight I'll build this one.

 

[GrindingThud]

Sweet!

Completed pictures of my KSA5.  I have only listened to it for a short time but so far it sounds great.  Bass seems to be especially well controlled.

Me

 

[joeyjojo]

  Thanks.  The amp got 5 other, lower output impedances and I've tried them all.  The low damping brings out the bass booming in the 800. 

 
Off-topic, but I'm just reading an article that made me think of this. Especially this bit:
 

Axel Grell, the chief-designer at Sennheiser, once told me that their top-of-the-range headphones are always designed to sound best at a low output impedance. The figure below shows the current flow of a HD-800 with the amplifier having an output impedance of 0 Ohm. There is no oscillation. Just a nice bump after the initial pulse-current, as could be expected from a critically damped system.

 
http://www.innerfidelity.com/content/musings-headphone-amplifier-output-impedance
 
This confirms my thoughts on the HD800, that it loves very-low output impedance amps to get the most driver control. If I were you I'd be using the lowest output impedance mode on the amp and bumping the LF up a bit with a good EQ.