Warm, yet detailed tube preamp

You didn't mention budget but you could upgrade to a Rogue RP5 v2 for less than half  the $$ of these other options.  I spoke to Rogue regarding an upgrade path from my integrated Cronus Magnus III.  They said that the RP1 would be an upgrade.  I was asking about the RP7 at which point they said that the RP5v2 is maybe better since newer development.

For my $2000 budget I went with the Audio-GD Vacuum HE1 MK3 (using an older Rotel 1080RB for amp)  several high end features in the Audio-GD.  I feel like I did very well for my budget.  and can save on cables- use XLRs

Backert represents a value and sound way above its price point. I’ve never been happier with a hifi component. It’s a lifetime preamp and I recommend it fervently!

Another vote for a Don Sachs pre. Another one that comes to mind is a CJ Premiere 17LS II.

I agree with inna the Vac preamp would be worth your consideration.

I have Zu Omen Defs also, along with an RP1 (RCA Cleartops).I feel the Rogue with those particular tubes has just the right touch of warmth. It replaced an LTA MZ2 which was not warm at all no matter what tubes were tried,but was very transparent and clear.I enjoyed it more as a 1watt power amplifier.The only fault I find with the RP1 is the volume control - not enough steps to fine tune it just right.I owned a Conrad Johnson PL10 in the past that I wish I'd hung on to sometimes. If I upgrade someday I would have CJ on my short list.

I’ll add a +1 to look at Don sachs. I have his model 2 and it’s outstanding. I prefer a more neutral sound and so I am running this with the provided rectifier tube; however experimenting with Mullard GZ34 gave exactly the warmer detailed sound you are asking about.  But given your price point you are right at the Raven cost point which is noted to be even more special.

There's a Supratek Chardonnay on Hifi Shark that will help in this regard, Ran one for 5 years before switching to a balanced system. Still have mine but keeping it in reserve for a second system someday. Made in Australia but good service here in US.

The not to expensive (for some) LTA MICROZOTL MZ3 PREAMPLFIER that punches far beyond it’s $3700 price tag. And when I rolled in NOS tubes it responded that much better. I got mine used from LTA which came with a $400 discount on a one month old unit from a trade up and haven’t looked back. Fantastic piece of kit.

I don't like the term "warm".  I think it is a euphemism for bland and muddy.  It is generally an attempt to fix a too bright system.  and often the too brightness is really a lack of bass.  People don't understand this but it makes sense if you think about it.  For example, you have a crappy power conditioner that limits current to your amp that mostly affect bass.  So to get the normal bass and volume, you have to turn it up.  now the highs are screaming at you.  

So instead of buying a "warm" preap, I'd try to find out what is causing problems in my system.

Jerry

I go to plenty audio get togethers  and for quality and build in the $5-6k range Linear Tube Audio made in U.S.A designed by Tube guru David Berning 

then later upgraded still if you use xlr the Swedish Lundahl Transformer upgrade 

and order with the 6 sn7 tubes , then there is a small set of tubes 12at7 or others 

very good all around and not like many that use the cheap $20 silver can alps pot like prima luna , these guys you a true resistive ladder  for the volume. Which is ultra important for detail. Mike at Audio Archon  gives excellent service and a fair price off on retail.

Honorable mention: Audible Illusions ... 

https://www.audibleillusions.com/

Backert is probably the best pre for the money.  For those with inclined ears and less aggressive budgets, my people: Apt Holman is powerful good too .... no tubes however.

hmn...van alstine fet valve CFR; T10RB is a little more tubey
 

The Cary SLP98 is a very warm and smooth sounding unit, even moreso than the SLP05.  Audio Research and LTA are not particularly warm.

I suspect that you Zu speaker is the reason for wanting a warmer sound.  While I appreciate the liveliness of those speakers, the have a very hard edge to their sound that I don’t think can be easily tamed with other component choices; it is too extreme in sound for that—you live that sound or find something else.

I think, VAC should be mentioned, though I don't know how it would match with your power amp. And NOS better Mullard tubes.

Yes, +1 on the LTA preamp. It is not warm like an old school CJ preamp (I owned a few), but is natural sounding, dynamic, and detailed, it is open and airy with breadth and depth with the right source components, Tube life is excellent. It takes a classic design from David Berning and truly elevates it. Really worth listening to.

Check the Spatial Audio Raven thread here.  Lots of comments posted by the two designers Don Sachs and Lynn Olson.  I own the Raven and it will be my last preamp.

I've never heard the Cary SLP98, but I, personally, do not consider my SLP05 to be warm.  However the air and detail is great.  In my opinion.

+1 LTA microZOTL Level 2 preamp. I don’t think mine is “warm.”  But, it sure is smooth and very detail. The LTA sounds noticeably better than the PS Audio BHK Reference pre amp it replaced (and I was very happy with the BHK, until I auditioned the LTA in my system 😉.)

The LTA uses 2 premium hand selected 12AT7 input tubes, and two premium hand selected 12SN7 output tubes.  (6SN7s can be used with jumper settings.)

Not audio research or lta. 

Any don sachs tube preamp. 

Supratek Cabernet 6SN7

Used Audio Research or Conrad Johnson.

I've always like Rogue (not Rouge). I'd look at an Aric preamp built around the 6SN7 tube. Take a look at what comes up, here.

Of note: 

Don Sachs

Cary 

Modwright

I’d be looking hard at the new Spatial Audio Raven and Aric Audio Motherload II preamps.  Not sure, but I think they both offer a trial period of some sort.  Best of luck. 

The LTA Preamp is exactly that. 

Have you tried rolling in some other tubes?

A good amp with great tubes can best a great amp with average tubes.