I think I have had enough time with this phono stage now to make a few remarks about it. In keeping with the spirit of this website I am not recommending this component, just reporting on it.
I got my unit off AudioGon after keeping my eyes peeled for a while. Normally the designer, Kevin Carter, sells kits and finished stuff directly from his own website, and he is also the US rep for Lundahl transformers.
To my knowledge, all of the K&K phono stages are hybrid tube/ss cascode gain with ss power supplies. My unit is mm only, 46 dB net gain and it was modified to use 6DJ8 tubes, 1 per channel, with the tubes’ internal gain pairs run in a parafeed configuration. My unit also has switches for +/- mono or stereo, and a mute, and it has the “Cardas Cap upgrade”, although I cannot address if/how that may factor in. My unit also uses “amorphous core” transformers throughout, which is another topic, I suppose. There are 1 pair/each of RCA and balanced inputs and outputs. I use the RCAs.
Since I changed my pre-amp at the same time I installed this phono stage lots of time has been spent sorting out what part of the new sound was which.
One of the main reasons I went from pure tubes to ss/hybrid was to see if I could get away from a certain “splashy” sound in the upper mids/lower treble that dogged me with all the all-tube phono stages I’ve tried. Also, I hoped to avoid the sort of “collapse” I had gotten on loud, complex music. Although I did escape the splash and the “collapse”, there was instead at first a somewhat reticent and slightly foggy quality that I immediately wanted to change.
I know it’s lame, and I’m sorry to say it, but changing tubes (to NOS Telefunkens in this case) and changing the stock Kimber parafeed coupling caps to Mundorf silver/golds took care of business immediately. Initially I tried 3.3 uF in place of the stock 4 uF, but it was not enough. I added .82 uF and I am going to go up to 4.7 uF in order to better balance the sound spectrum and also preserve ambient cues at both ends of the spectrum.
Note (again) that I use an Ortofon MC 3000 II cartridge along with its dedicated T-3000 transformer. I also use a tweaked (basically, weighted-down) Well Tempered Reference arm on a Sota vacuum holddown ‘table. Pre-amp is the Bent TAP TVC and amps are Lamm ML2s. Speakers are tricked-out Diamond Edition BassZillas, which use tamed Lowther DX-4s high-passed in 2’X6’ OBs(plus folded, tapered "wings" to equal > 3' net width) over 15” Audax woofers in LEAP-derived BR bins, and I use naked Audaphon ribbons over 10k Hz. Speakers are about 96 dB efficient, with great imaging possible.
The sound of my cartridge is as tape-like as any I have heard, and the K&K is probably more “neutral” and plainly accurate than most folks would want. It might be slightly kind to recordings, but you can hear all the “engineering” along with the playing, for better or for worse. Dynamics are as good as I’ve heard, apart from the Boulder 2008. Pitch, timbre, weight and scale are as good as I’ve heard, meaning as “accurate”. The sound was all over the place wiht 3.3 uF but with more output capacitance things have settled down along with a critical-for-me sense of “artistry” and “ensemble” that IMO makes or breaks a hi-fi system, and this sense is conveyed on quiet and loud passages, and even on “obscured” passages, with all types of music.
I need to comment on image density because this is a strong feature of the K&K. Images are pretty damn solid, and the right sounds come from the voices and instruments themselves. There is very little of the usual sense of “air”, since any sense of space becomes the actual listening room. In other words, instead of the more-usual high-end "air", the K&K somehow blends HF with LF ambience and gets throughout the room. The unit also allows music to “charge” the room, but I am not sure if the K&K “creates” this phenomenon or if it just "allows" it.
The K&K is not purely analytical, because it does make plenty of music. But it also lets you hear into how the music was made, which is not something I was/am after, really. This does not usually detract from the music, but occasionally it does. It works especially well on the old Mercurys and RCA shaded dogs, and also on many old Blue Notes, some old Vanguards, etc., etc! Basically, it is wonderful with great recordings and where there is a great performance along with a great recording, it is Heaven! Ah, Tosca!
As soon as someone points me to a great “massed strings” recording that is “realistic”, then I will comment on the K&K’s performance in that area. So far, large scale works are as likely to be satisfying as smaller works, but I have to say that “fluff” has mostly been pretty boring. OTOH, using Romy’s instructions for speaker placement has been working its own wonders, and I will go back and try some Beatles, etc. soon, to see/hear if that can still be fun with the K&K. So far I have been enjoying "important" music too much to be playing around!
I will be keeping and using this phono stage for the foreseeable future because it does most of what I want from a phono stage. It could be more “transparent”, but I would not give up anything it does to get that.