What is the best Reel To Reel machine ever built?

Sorry to sound like a broken record but "Best" is in the eye/ear of the beholder. There is no definitive "best" anything, it's all subjective. When you ask a question like this, the answers will always be what folks think is "best" to them in their system.

as far as best Reel to Reel machine ever built, i'll agree it does become a matter of personal preference. but there are some objective things that can be said. there is a difference between consumer machines, pro-sumer/broadcast machines, and master recorders. and only master recorders, where the build level and transports are not compromised, are really candidates for being the best machines. there is a reason that the master recorders were used in studios to make our beloved music.

this is not to say that a particular hot rodded broadcast level machine cannot have perfect heads and output electronics and sound better than nice master recorders.

i still own a stock Technics RS-1500. i owned a deParavicini modified RS-1700, which sounded great. but when i compared either of those to my Studer A820, either with or without the King/Cello.....there was a refinement to the music with the Studer which the Technics could not attain.

and when you look at the way tape is handled, my Studer A820's and ATR-102's simply are in another league compared to even broadcast machines. i think the Nagra T would also fall into that territory.

so talking about the best ever tape player you need to consider the build quality and tape handling mostly. heads and output electronics can be changed. i'd liken it to a turntable and arm in vinyl. yes, the cartridge and phono stage is important; but if the turntable and arm don't properly put the cartridge in the perfect position to do their job there is compromise.

and since all these machines are 25-60 years old; how do you objectively compare RTR decks that are in such variable states of repair and optimization?

as far as which master recorders are best, i have very limited experience. maybe Ki Choi would be the guy to have the most to say about that question. he owns almost every master recorder ever built, in most cases multiple, and is able to work on them too. i suspect i know his preference.

there is a RTR repair facility which does answer this question from a slightly different perspective. here is the question they ask. and here is their answer.

i'm not sure i 100% agree with them. but they know quite a bit more than me about the subject. and their answer is a bit self-serving.

Well, while I certainly agree regarding mechanism and transport, I have good reason for recommending the C-37 especially for home use 2-track playback. Carefully serviced, their built-in amplification is about as close as you can get for the best possible in tube-based RTR playback.
Sure - there are customized ss based playback amplifiers by notable audiophile origin (Cello etc.), but they never moved the earth beneath my feet.
A top-notch C-37 may have more hiss in playback than most japanese RTRs of the 1970s/80s and certainly can't compete with Nagra either, but then you will have a very hard time getting the dimensionality, soundstage, micro-color and "live-feeling" a C-37 can provide.
After all we are talking home use playback here - not recording, not pre-mix master taping.
My vote for playback - and meant for that purpose only.
Another point - easy access (at least in Europe...) to NOS/NIB original parts. Tube-based plug-in devices can be serviced quite comfortably too.
Lastly and maybe of relevance - I am not bias on tubes.
My power amps are SEFets, battery powered - for good reason.
Cheers,
D.

Most studios in the US with functioning tape machines have newer Studers. There were still a few new ones for sale as recently as a few years ago. Sadly, most of them sit in the corner unused. There are a few engineers who still insist on them, but its getting to be a very small number-mostly engineers with private studios of their own. The pressure and speed (and budget) of the modern studio/client combo makes it a tough decision and a big commitment. Its so cool to see Stevie Wonder Innervisions liner notes and see a friend (who now works at JBL) listed as "Tape Operator".

i almost traded my Dobbins Garrard 301/Loricraft for a 220v 50hz C37 from Europe....but in the end i did not want to deal with the power converter issues. so i purchased the 'American' C37, the Ampex 350. which, like the C37 in Europe, has lots of parts available and has that tubed output. and i purchased an additional set of Ampex 351 output electronics to be able to use that too.

which is better in that light? C37 or Ampex 350/351? many different opinions on that. lots of great music was mastered on both.

i do think that neither of those machines are the 'one answer' for all tapes. and the tape transports of either are crude and abrupt compared to the A820/A80/ATR-102.