Don Sach's pre amp

Can't answer all of your questions, but I'd say the DS pre is a touch on the warm side of neutral. A little tough to say because so much will depend on what tubes and output capacitors you have on it.

With the cv-181s and miflex copper caps, I found it pretty "modern" sounding. Extended and detailed. I liked it and definitely found that it improved the sound of whatever dac I fed it (ps audio perfect wave dac -> directstream dac -> audio mirror tubadour III se). 

I did eventually settle on vintage tubes (40s/50s rca grey glass vt231s and Sylvania Jan's) however. I lose a little extension with them, but gain refinement, tonality, and imaging. 

I also tried out a variety of output capacitors. The miflex had good tone, but were very 2 dimensional in my system. Mundorf Supremes added depth to the imaging, mundorf Supremes silver/gold in oil added even more depth and refinement but took away some bass, and v-cap tftf were too cold (tonally) for my system. I have some duelund tinned copper cast on the way.

All of these variables definitely change the sound, which I like to attribute to a quality, revealing circuit.  Does make it a little hard to nail down the pre's sound for a new buyer though.  

The pre does come with a remote by default. The newest modification gives you both volume and input switching but loses balance control. If you need balance control (not available on the remote) then you only get remote volume and muting. 

Final caveat, as always, these impressions are likely very system dependent. I need to update my dac description, but you can see the details on my system page.

Also, do note that input impedance to Don (or any other manufacturer). If the preamp design uses output capacitors you'll need 8uf caps to prevent any low frequency rolloff (https://www.v-cap.com/coupling-capacitor-calculator.php).  That'll limit your boutique cap choices unless you've got no budgetary constraints. If you were to buy the miflex copper caps yourself, it'd be $500 at partsconnexion... And they're huge, maybe too big to fit. 

I'm sure Don will have some options for you however. The mundorfs are smaller and cheaper. 

Thanks, cal. Lots of variables. You’ve obviously put in a lot of work and money to find what works for you. I’ve been sticking to the easy changes, such as rolling tubes in the Lampi. I had a bad experience with the sale of my DSD, so I’ve got it back and am listening now with a PrimaLuna Dialogue preamp that came with old Mullards, while I await the return of my Lampi and think about whether or not to ditch the PL for something better. People -- developers and users -- were correct that although counterintuitive, sticking a good preamp between dac and active speakers, i.e., amp, improves the sound. Finding the right preamp for one’s tastes and budget is the trick.

@highstream Wish I could comment more about preamp options, but the DS pre is my first. Prior had run DAC direct from the PWD and DSD. Like you said, adding in a preamp is really a huge improvement. Counterintuitive as it may be. My reading did convince me that any relatively simple preamp circuit either based on 6SN7s or DHTs would be optimum. I suspect many of the simple 6SN7 pres (Supratek, the DS kit, deHavilland, etc.) would all be excellent and more similar than different.

Also, just checked my pre's height and it looks to be under 8" tall with tubes (and some vibration control).  A little hard to check inside the cabinet.