Running an External Phono with a Hovland HP-100

That is correct, it is the P5xe. I'm not quite as ignorant as it may seem; I couldn't layout or interpret a tube or a solid state circuit if my life depended upon it but I do know what sounds good...I'm definitely not a technician so before I plug something new into my $6,700 Hovland (the very best preamp that I have owned in 30 years) I want to be positive that I am not missing something important...

You're right, variances in the 12AX7 (and all tubes in general) can make a huge difference in the quality of sound. I've tried several sets of Mullard's with varying success. The first set I tried was a definite improvement over the stock factory tubes; the second set of Mullards were terrible (very noisy after a few months and both sets came from UpScale Audio). I'm back to the stock tubes and they sound great.

I educate myself with my ear :), and through interactive mediums like Audiogon. If I like the way it sounds I go for it. The purpose of the exercise is to compare several external phono's to the Hovland's internal realizing that ultimately they all pass through the line stage. Next up is probably the Audio Research PH7. The new Ref 2 phono will follow. And then , a combo of the Ref 5 preamp with the Ref 2 phono. It will be interesting (for me at least) to hear how the Hovland compares to these other combos...

I did not mean to belittle you in any way. For many years, my audiophilia took the same path that you are on. I am just saying that in the long run you will benefit (i.e., save a lot of money) by acquiring some basic knowledge of the circuit's design. What I also meant to imply is that there are a plethora of cookie-cutter products out there that all in the end use the 12AX7 in some sort of single-ended topology. If you want to try something that is likely to have a "different" sonic character, you might want to investigate balanced phono stages or phono stages that use a different sort of input gain stage, etc, etc. Specifically, if the Audio Research and the Hovland utilize similar topologies, I would look elsewhere for variety, rather than to purchase the AR. This is no knock on the AR taken by itself.

Did you use the Ayre in unbalanced or balanced mode? That device has a true balanced circuit, so you are not hearing it at its best if you use the "unbal" input and output. I have read elsewhere that its performance is subpar if used in that manner.

The Hovland is unbalanced only. I believe that all the Audio Research pieces have both balanced and unbalanced. That would be an interesting trial too; use the Ref 5 and the Phono Ref or the PH7 in balanced mode.

So I don't think you can use the bal inputs on the Ayre and the unbal outputs, both at the same time. I think the switches at the rear of the Ayre require you to choose between all bal (inputs and outputs) or all unbal. But if you can mix and match, I recommend you try the Ayre with bal input from the cartridge and the unbal output to your Hovland. The latter will be a necessary evil, because as you say the Hovland is unbal or single-ended. (In this case, the two terms mean the same thing.) If you used the Ayre in unbal mode throughout, you really did not hear it at its best. The same will probably apply if you try to run any of the balanced tube phono stages thru the Hovland linestage section. In that regard, try to find out whether the AR units are true balanced circuits or just provide a balanced XLR output for convenience. If the latter is true, then you are better off using the unbalanced or single-ended mode from cartridge thru to the amplifier. (The XLR or balanced output derived from an unbalanced circuit may introduce an extra buffer stage which often colors the sound and robs detail.)