tube recommendation please

The CV4003's (12AU7) are cheaper, I would try those first. The 5AR4's are kinda pricey.

Since Kevin Deal (owner of Upscale Audio) is also the importer for PrimaLuna, I would call/e-mail and ask him. He has never steered me wrong over the past 12 years or so and I have bought alot of tubes from him. I'd use his knowledge.

If the manufacturer could confirm this, that would be great, but I found a picture of your amp on the internet and it looks like the 12AX7 tubes (the pair in the front) are most likely the signal tubes and the 12AU7 tubes (the pair in the rear) are the driver tubes. The signal tubes will have the dominant sound and will be the most sensitive to tube microphonics. So, in terms of best bang for the buck, one way to look at it would be to replace the signal tubes first with the highest quality you can find, followed by the driver tubes later.

As Mofimadness mentioned, the Mullards are indeed warm and are fine tubes. If you find them too warm, RCA and Tung Sol are nice also, albeit not as warm as the Mullard.

Here's some examples of the degree to which you could fine tune your system, in order of decreasing warmth:

1. Signal & Driver both Mullard
2. Signal = Mullard; Driver = RCA or Tung Sol
3. Signal = RCA or Tung Sol; Driver = Mullard
4. Signal & Driver both RCA or Tung Sol

In my system I am currently running Telefunken for the signal tube and RCA for the driver tubes, although I am about to go all Telefunken. But Telefunken are on the neutral end of the spectrum, however, which is what I prefer.

But if you experiment with the Mullards, RCA, Tung Sol and Amperex tubes I'm confident you will find a satisfactory combination.

IMO the Mullards are hard to beat. Telefunken are also quite good and I agree w/ Reynolds853 in regards to neutrality.
Brimar/Amperex bugleboy have been good for me also but it's been a while since I've used them and memory can't always be relied upon...
This may be anathema but Groove tubes has a spiral filament
12ax7 that is supposed to emulate the Mullard, but I have only used them in a guitar amp. (Old Marshall- that originally came w/ cv series Mullards- I took them out so I didn't wear them out) The Groove tubes are a great substitute in that application and I really don't think the character of the amp changed much if any- I was smiling the entire time I played it which was true with the Mullard preamp tubes as well :)

Thanks, great explanation on the signal tube versus driver tube. I will double confirm that 12ax7 is the signal tube. I also read some comments saying the rectifier may not have any tonal impact. I just order a pair of CBS-Hytron 5814A (12au7) from eBay based on some comments on the internet. I think I am good now. I will wait for the tube and see how much difference does it make. If the result is positive, then I will spend more money and get some nicer 12ax7, like the Amperex long plate D getter =)