Hi Joe, Good to hear from someone else the owns the Kenzie. I am really loving the Kenzie as well. When I purchased the Metrum Octave MKII NOS Dac, it was recommended to look for a zero feedback amp. That is how I found Ampsandsound, and your review of the Kenzie. I knew this was the amp I wanted to try. I have two pair of Hifiman headphones, the HE-6, hard to drive, and the HE-4, that also likes current. Justin recommended the 600ohm setting for the Hifiman, even though the impedance is 50ohms. I route the DAC through my receiver to the Kenzie, as the Denon has the capability of Zone 2 and Zone 3, for both of my tube amps. Sound is just as you described it, black background where the vocals and instrumentals just appear out of thin air. The Kenzie is just so good, but after a few hundred hours the sound just jells. I do give a lot of credit to the Octave DAC though. There are tow higher levels of the Octave, the Hex, and the Psvane (just out), but I am happy with my setup as is. I read a review on the Octave by 6moons, and it was recommended to resample 16/44 to 24/176, work really well with Jriver MC20, soundstage is much bigger, more details, just better sound to my ears.
I have also experimented with several tubes/manufacturers, and I have found some really good ones that better the tubes that Justin sent with the Kenzie. I pulled the RCA 1626’s that Justin sent and I replaced them with Military Qualified 1940’s Ken-Rad VT-137 / 1626 tubes. I did some research on the Darling amplifier designs and other recommended Military or JAN tubes as having the best sound, so I went looking for them. I am very satisfied with what I found, NOS tubes from the early 1940’s. Military and JAN, were made for military use, and from my other tube experience, they can last up to 10,000 hours. The best driver tube I have found is the 1943 NOS In Box Date Matched Pair RCA USA JAN-12SL7GT/VT-289 Black Plate Vacuum Tubes, biggest soundstage, best bass, great mids and lots of detail, my personal favorite in the Kenzie. Another good tube that accentuate the higher end, but a little more compressed soundstage is the Sylvania NOS 40s Navy VT-289 12SL7GT. I have a couple spares of these if interested. Then Justin sent me a Raytheon 2C52, and I purchased another that is a JAN Raytheon 2C52. The JAN sounds better than the non military 2C52, and the Raytheons are also higher gain than the RCA or Sylvania tubes.
I really think the Kenzie is a reference amp, and at a very reasonable price. I would put it up against something like the WA5, any time and be satisfied. The Woo WA5 is three times the cost with quality tubes. Nice thing about the Kenzie is, tubes are cheap. My other HP amp has Mullard NOS tubes that I paid $200 plus each, the Kenzie tubes NOS early 40’s were under $20 each. I have enough of the tubes I like stocked up for many years to come.