Fully Balanced pre to SET amp

I have an Atma-sphere MP-1 pre that is fully balanced. My cartridge is wired balanced with XLR to pre. Also my CD is sent XLR from the fully balanced cd player. I have an XLR cable to the SET power amp. Two pins are shorted at the amps input with an adapter to rca. This is what Atma-sphere recomended to me. Is there a way of staying fully balanced up to the amp's input. Transformer maybe? inside chassis or out. What are SET amps with XLR balanced inputs doing. Is it anything more than shorting out two pins like I am doing.
I know this does not answer your question but, if additonal cost is not an issue, you should consider an M-60 monoblock pair (w/Speltz Zeroformers if loudspeaker impedance presents a difficult load). This, of course, assumes your loudspeakers are not power-hungry (most SET-compatible ones aren't).

I run balanced output from an Audio Note DAC into an MP-3 preamp into M-60s. My loudspeakers are connected only via Zeroformers. This system presents me, for the first time, an absolutely quiet background. The sound is thoroughly enjoyable (rock and acoustic/electric jazz). With proper listener/loudspeaker position the center images are holographic. I'm a permanent member of the "fully balanced" club.

I bought both the MP-3 and M-60s used on 'Gon, then had them fully tricked (recently added V-caps to both). This proved a very cost-effective (relative to high end gear prices) way to go. If you are concerned about Sino/Soviet 6AS7 output tube quality or availablity, I can attest to the very high quality and ruggedness of both the Chinese and old Soviet military versions. I've paid an average of under $10/tube for my stock of about 200 (roughly half Sino, half Soviet).

I can understand if you truly enjoy the sound of your SET amp, as I've owned a few myself. It's just that the, "Transformer maybe?", remark in your post caught my attention in the context of Atma-Sphere gear, albeit preamp only.

Best wishes in your search for the sound you want.

There are three ways to to go from balanced to single ended :

1. use a transformer
2. combine the + and - signals with an active circuit
3. just use the + signal as Atmasphere recommends

Both 1 and 2 would have to degrade the signal in some way.

The bigger question is why do you want to stay fully balanced to the input of the amp? If you are going to use that preamp with an SET amp you have to convert somewhere so why not do it as the manufacturer recommends?

FYI your CD player is not really "fully balanced." The information that is encoded on the CD is not balanced so the player is somehow creating the minus signal.
Single Ended Triode (SET)amps are by nature Single ended.... Hence the name SET.