Hi all: My AKHA journey started May 2015. As you might remember I revived this project as it is too important to let die. Had many interruptions along the way; ie many visits to the heart specialist w my wife etc. etc. The main question: Was it worth it? A resounding YES. You may recall I came up with an easy way to raise the operating voltage of the SCHA to +- 20vdc, a marked improvement to that amp.
Moving on: The AKHA is at an entirely different level. The first thing you notice is there is more air around the music. Dead quiet & free of distortion & the cleanest audio I have ever heard! The channel separation is improved with a wider sound stage. Had to have a friend evaluate stereo separation & sound stage as I have been virtually deaf in Right ear, most of my life. I am using a ladder type volume control. There are only 2 resistors in the circuit on each of 23 steps; this eliminates the choke point that series resistance string controls introduce.
I am listening thru modified Fostex T50RP Orthodynamics; they are a big improvement over standard dynamic driver headphones. Orthodynamic drivers are a wide range version of a ribbon tweeter; simply put they are a ribbon microphone in reverse. More later after the caps completely form etc.
My AKHA now has had 100 hrs. of running time. There has been progressive improvement as the capacitors in the power supply are now fully formed. I have added an output impedance switch, having 4 positions, low, 65 ohm, 120 ohm & preamp output of 100 ohms.
For those members who bought boards & dual matched transistors; you need to build this amp., it is worth every bit of time & money required, for the build.
For everyone who participated in the group buy for the AKHA headphone amplifier but have not built it; let me encourage you to get to work & build it. It has the cleanest sound of any amp. I have ever heard. It also has a lot more air around the audio than I have ever heard. It easily outperforms most of the high end units on the market.
As Sandy K. is no longer a member & cannot be contacted, I will be able to answer any questions you may have.
Post by freddypipsqueek on Jun 23, 2017 15:19:21 GMT
I'm one of those with the kit (I have a spare Chiara as well) but little time. I will put some aside this summer. A.
Black Box 2, Benchmark DAC2D, Arcam irDAC, SoTM SMS-100, Sony CDP227ES, QA550, Systemdek IIX & mods, Chiara & Andante, WNA MK3 & Cascode, Music First Phones, Audiophileo, Singxer F1, SoTM USB cards, Mission Cyrus One & 751's, Headroom The Little, HD580, HD590, HD600, HD555, HD700 K612. Too much wire !! - Kimber, DIY silver stuff and Stereovox cables - AND a bottle of wine & a lot of Mods.