What preamp with your GaN power amp?

I use the CODA 07x preamp with the LSA Voyager 350 GAN amp. It works great sonically. Though the 07x  has some operational gremlins and design choices that annoy me. The sound is mostly a winner though. A little bit of whisper quiet hiss also bugs me.

I have also tried the Topping pre90 preamp with the Voyager, CODA #8, and Benchmark AHB2 amps. On the LSA Voyager the volume on the preamp had almost 0 useable steps. On the CODA #8 it sounded flat, likely impendence mismatch. On the AHB2 it sounds great.

The preamp I sold to replace it with the cheaper Topping pre90 was the Benchmark HPA4 (or LA4). In retrospect I wish I did not sell it because I think it would have worked with all 3 amps. I am going to bring it back in the house to see how it works with the Voyager and CODA #8. I am thinking of ditching the Topping pre90 and moving the Coda 07x with my AHB2 mono amps on a second system, which is an awesome pairing.

I am thinking of getting the Benchmark LA4  preamp with the Voyager or CODA #8 (not sure which stays) since I use this system the most and do not want to get annoyed so much. Benchmark has the 30 day home trial which I will use.

The CODA 07x has some warmth to it and although the Voyager is also a little warm it is not a bad combo. The Topping pre90 and Benchmark HPA4/LA4 do not add much sonically. You will hear your sources and amps. 

Budget

I find the Voyager very holographic, which IMO means one doesn't need a tube preamp. I am using an Audio Alchemy DDP-1 + PS 5 and loving it, though I am sure there are better preamps, but at what price? I recently saw a DDP-1 +PS 5 on AG ads for $1850

hth

I am feeding my Voyager GAN amp with the Don Sachs tube preamp.  It is a blissful sounding combination.

Well not a GaN Class D but I use Audio Research sp16 tube preamp with Bel Canto ref1000m Class D mono blocks and that is a match made in heaven.
Which GaN specifically? The input impedance is the key spec for any amp type to know that will help determine the right pre-amp. Nothing special in this regard with GaN designs. The input stage design is what matters always. Tube preamps have high output impedance. With a tube preamp in general I would go no lower than 40-60 kohm input impedance on a matching amp to be sure things perform well with good dynamics and lowest distortion for detail, imaging and soundstage. For example Ref1000ms are 100 kohm input impedance designed to work with most any preamp. That is a big reason why I ended up choosing it.   I would do same for a GaN amp with tube preamp. Good luck!