tubes 4 hifi
 "the path of least resistance is through a vacuum"

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HA14 headphone amp for Dave

front view

rear view

inside front view

inside top view - "iso-damp" material on chassis base

inside rear view

This HA14 headphone amplifier was a custom design and build for my good customer Dave.
Based on the schematic of an existing $800 product, we decided to do several upgrades to the basic design of the original
for better sound and higher power output, using octal tubes rather than common noval tubes.
These upgrades include choke filtered high voltage power supplies, with regulation for the signal amplifier.
The result is more similar to products in the $1500-2000 range, with a completely dual mono design,
using a pair of dual primary transformers as the only common element.
Each channel has a 6X5GT tube rectifier with a CLC filter using a choke. There are two inputs, and dual mono gain/balance attenuators,
followed by a very high quality TKD volume control. The high voltage to the 6SL7 signal amplifier is regulated for very low noise.
The signal thru the 6L6GC output tube goes thru a high quality SoniCap to the impedance matching output transformer, with outputs for
low-Z (32-100 ohm) and hi-Z (200-600 ohm) headphone outputs. Frequency response is measured to be flat from 10Hz to 40KHz.
Output power is meaured to be 1000mw into 100 ohms, about 6 times as much as the original base design.

here's an exact copy of an email I got from Dave P who bought this headphone amp . . .
"the head amp is just AMAZING. IMO that head amp was the best audio buy Ive made in a LONG time.
Love the amp and the cans. Thanks again so much for that!
 I'm listening to it now and simply can't get over how breathtakingly beautiful it sounds.
Roy, I really will never be able to convey to you how grateful I am you made this for me.
I mean that from the heart. This amp paired up with these HE-500 headphones is like an angel
sitting in my room with me singing to me late at night, not disturbing anyone near by.
Since this change you made to the amp its been rock solid and the sound really couldn't be improved in any way possible IMO.
I really can't believe how amazing it sounds. Currently this headphone setup sounds better than any stereo I own
or have heard in recent time. You stand on god like abilities in your design and creation IMO.
I just can't believe how great this setup sounds.
I know I'm gloating on an embarrassing level, BUT ITS TRUE!
The only thing I can tell you is I'm so glad I / you pursued this tube design headphone amp."
Dave P

The same circuit design but using more common and less expensive 9 pin tubes (12AX7, EL84, 6CA4) is our new HA12 headphone amplifier.
All on one compact circuit board (7.2' x 5.4") and using a single power transformer, a complete kit is available for $790, or finished and plug-in ready for $995.
see photos and info on this page here
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 tubes 4 hifi
 "the path of least resistance is through a vacuum"