Best 12AU7 Type Tubes for a Preamp

@mitch2 

Good choice going with the Amperex PQ.

I sent you a PM.

@mitch2

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.

From this description I would recommend Amperex. But you’ve tried one of the best tubes out there, Amperex PQ 7308. It presents lush mids smooth highs, and a 3D soundstage. Since you like the new production Mullards, it seems as though you don’t want extended highs since these are rolled off on top. I suggest trying NOS Mullard long plates with either square or round getter. If not available, Mullard box plates CV4003. Brimar is another brand from the UK, same time period, that have more clarity, are less warm with a good soundstage. I've seen box plates CV4003 for sale.

NOS Mullards don’t have extended highs like Amperex or Bugle Boys, but have more realistic highs than new production. They’re also more detailed, have a lush midrange, and 3D soundstage which can be holographic in the right preamp. The problem is price and availability. After the shortage of Russian tubes this past year, inventories of US and European tubes have been exhausted, so prices are very high. What I’ve been doing is buying slightly used tubes that test as NOS. Mullards, Amperex, Telefunken will still fetch a premium, but if they are ANOS (almost or about NOS) they could last years in a preamp. Brent Jessee would be the first dealer I would contact. Andy at Vintage Tube would have the best stock, but there’s a 6 week wait at this time. Use Google to check out prices. Maybe others can suggest some trusted dealers.

@holmz 

Brent Jessee has a detailed description of NOS brands and their sonics.

Tube’s sonics will perform differently depending on the circuit. What preamp are you using?

RCA blackplates, Mullard boxplates, and Amperex 7316 are all excellent tubes but have different sonic signatures. What type of sound do you seek; warm, lush, neutral, high-end extension?

The Amperex 7316 is a premium, in-demand tube and fetches a high price. That would be my blind recommendation, airy highs, dynamic, lush midrange, and 3D imaging. When buying NOS, only use a reputable dealer that publishes test results.

I've already expressed my preference for NOS tubes and to buy from a reputable dealer, but I must give props to Psvane. My preamp came with a Psvane 12AU7-S with gold pins and it had very nice tonal qualities. It presented a wide soundstage, but lacked the depth that so many NOS have. Nice top-end, not etched like some of the Russians, just a pleasant sounding tube that works very well when combined with NOS.

if the circuit can handle it 12BH7 is the preferred alternative to the 12AU7

5963 (industrial) and 5814A & 6189 (military) are drop-in replacements for 12AU7/ ECC82. 

@mitch2 

You need to decide which direction you want to go with the sound. After using the stock tubes, what kind of change do you want, more clarity, airy highs, more bass? There have been good tube recommendations, but they cover the gamut of sonic signatures as well as price points.

@mitch2 

Sounds promising, you've used premium Amperex before so you know how great they are. Did you look for any NOS Mullards?