Best 12AU7 Type Tubes for a Preamp

Thank you everyone. The unit is (not actually but sort of) a preamp.  I have owned a lot of tubed preamps in the past and didn't think I would again but when I purchased Hattor's The Big Preamp to run in passive mode so I could have remote volume control and a display, I took a chance and also purchased their Hattor Tube Active Stage, which uses two 12AU7 tubes.  IMO, the unit sounds way better than it should for what it costs, and good enough that I am seriously considering keeping it in my main system.  The gain from my unit is +6dB.  FWIW, the Big Preamp can be run in passive mode, passive with the Tube Active Stage, or through its own internal NewClassD opamp output stage at a selectable  +3/6/9 dB gain.  The opamp output stage also sounds quite good.

Back to tubes, I like the idea of not having to rely on NOS tubes but wasn't sure if the Psvane or Genelex Gold Lion were even in the same league as the NOS offerings.  Back when I was using tubes in preamps years ago, it seemed everyone was after NOS 6922 tubes and the 12Au7/AX7 varieties were relatively inexpensive.  Times have changed.  Things sound good now, so I may just try the Psvane tubes and call it good, but I will also look hard at some of the reputable NOS tube sellers and see what I can come up with.

Thanks all - you have offered some really good thoughts and suggestions for me to consider, and thanks @dekay, the linked thread did have interesting and useful information.  

I live about an hour from Andy Bouwman • VINTAGE TUBE SERVICES, and I can get up there almost any time I want for my work so there would be no need to ship tubes.  I purchased from him long ago so I know how meticulous he is, which means higher prices, longer lead times, but almost surely a more successful result than dealing with mass market type sellers.  Since I only need two tubes, I plan to call him on Tuesday when he is next open and then purchase whatever he recommends.  As a bonus, there is some really good mountain biking very close to his shop!

As a last thought, this thread has reminded me of what a helpful, friendly community we have here - thanks again.

@lowrider57 

After using the stock tubes, what kind of change do you want

Actually, there is nothing "wrong" with how it sounds now.  The sound is clean, clear, and there is no noise I can hear over what I get using the internal SS opamp output stage in the Hatter The Big Preamp.  Dynamics are good, as is the bass, but I don't typically split hairs over bass since I have dual subs so I can mostly adjust the sound of the bass as needed.  If anything, I wouldn't mind a bit more tonal density in the midrange through upper bass, but not at the expense of clarity.  I am also curious whether I will hear any spatial differences with NOS tubes, like greater perceived dimensionality.

I have been comparing the stock JAN PHILIPS ECC82 (12AU7/5963) tubes with reissue/new Mullard ECC92 tubes and have a slight preference for the Mullards.   I have used different tubes in the past in preamps by Lamm, NAT, Lector, BAT, and others.  In preamps using 6dj8/6922 type tubes, I gravitated to the Amperex 6922 PQ white label or Amperex 7308/E188CC white label.  I cannot remember which brands/vintage of 12au7 tubes I have used previously.

@lowrider57 - You are correct about Andy's availability.  I went to contact him this morning and found this message on his website:

Notice: Due to extreme demand, I am only answering the phone on Fridays and I am running about 2-3 months behind on filling orders.

I tried calling anyway and received a busy signal.  Even if I were able to speak with him, I am not patient enough to wait 2-3 months for delivery of two tubes.  However, I did also find the following message on Andy's website so at least there will be a future solution for people who want a faster turn-around.

Online ordering of select tubes is coming soon and those orders will be shipped within 2 days.

In the meantime, I will try contacting Brent Jessee or will look around at some other vendors. 

Interestingly, I was looking in the drawer where I used to keep tubes and found four matched, measured, and unused NOS Amperex JAN 7308 tubes that I no longer have any use for.  I cannot remember the preamp I had planned to use them in so I was surprised to find I still have them.  Some surprises are better than others!

There is an ebay seller with over 1,500 sales at 100% positive feedback who has several pairs of strong measuring Amperex 7316 tubes at what I would consider reasonable pricing (less than $200 each).  I found two pairs and emailed the seller for advice on selection.

Just bought a matched pair of Amperex PQ 7316/ECC186 Holland Short Plate O-Getter 1965 Ct5 tubes that measure like new.   Should be here by Saturday.

No, I did not look for the Mullards.  I believe those short plate Amperex tubes are supposed to fall somewhere between the lusher Mullard long plates and box plates, and the more precise/detailed Telefunken and Siemens tubes.  I did like the PQ 7308 version in other preamps I owned some years ago.

I was recently asked a couple of questions related to this thread so I will partially answer here.

Q: Any update on how the new tubes sound in your system ?

• New Tubes: Amperex PQ 7316/ECC186 Holland Short Plate O-Getter 1965 Ct5. I have had these in the Hattor Tube Active Stage for a couple of weeks now and the tube stage is sounding the best it ever has. While the tube stage does not seem to be terribly sensitive to the tubes being used, the Amperex tubes seem a little more musical with maybe a little more definition than the new stock Mullards I was using. However, I could have lived with the sound from the Mullards.

Q: What changes does the tube buffer makes over the Big Preamp?

• I need to do more listening to answer this. As I remember it, I was impressed with the sound through the internal NewClassD op-amp active stage of Hattor’s The Big Preamp. The drive, dynamics, and clarity were very good but I need to make the time for a direct comparison with the Amperex loaded Tube Active Stage before I answer the question. However, as with the tube question above, my recollection is that I could live with either option, either the tube stage or the internal op-amp stage. BTW, my preferred gain with the internal active stage as I recall was +6dB. I will report back on this comparison after I listen some more.