What is the best tube pre-amp for my system

A sound recommendation. But I have yet to find a used one on the market....

Snooker14 hi, Have you tried direct connection between your Ayon CD5 and Pass 350.8?

As the Ayon has output level control at it's lowest setting from 0-4V variable.

And your Pass amp is 50kohm input impedance and only needs 2v in to drive it to max output.

So as you can see you don't need more electronics and gain in the signal path.
As doing a direct connection from Ayon to the Pass is a perfect match, impedance, gain and drive, and will give you the most transparent sound you can get, also save you a stack of money not getting a preamp.

Unless you wish to add some colouration by using preamp, then you will have the added problem of way too much gain.

Cheers George

I agree with George. You would be spending a ton of money to purchase a preamp that would do justice to your existing equipment, and if it provided any benefit at all it would probably be the result of either providing a more transparent volume control mechanism (which I doubt, given the apparent quality of the CD-5), or masking an existing deficiency in the system (which would be best addressed, if present, by determining the root cause and correcting it). And at the same time it may reduce overall transparency unacceptably, and it would probably result in too much gain, as George indicated. The latter issue forcing you to either use the preamp's volume control undesirably close to the bottom of its range, or to use it in conjunction with a lowered volume setting on the CD-5, which would negate what may be the main potential benefit of adding a preamp.

Regarding the impedance question raised by Reynolds853, both the 30 ohm output impedance of the Spheris and the 300 ohm output impedance of the CD-5 are fine matches for the X350.8.

Regards,
-- Al

If you don't plan to use any other source, while I rarely agree with George (and his comments about tube coloration are really off the mark), in this case it does not seem to make a lot of sense to employ a preamp.

Now if you have to have long interconnects between the amp and the volume control, a preamp might be in order, or if you plan to have more sources. But your CDP has a volume control, you might just try hooking it up directly. As best I can make out, that is part of its design.

Snooker14
This Ayon CD5 source you have has a 300ohm 6H30 tube output buffer, and it's stronger and has better drive than most tube preamps have, but still not as strong as most solid state output buffers (which I prefer), so keep your interconnects below 4 or so meters long.

What you'll get then by driving direct is a sound that is true to what the source is attempting to give you, and not be influenced by any additional tube or solid state preamp colourations/masking as well, with all their added needless electronics in the signal path, plus also another set of interconnects as well.

Cheers George