I'm a Mullard man myself, so I would recommend the Mullard CV4003 (12AU7), (platnium grade) from Upscale Audio and a pair of Mullard GZ34 (5AR4). These are getting a little harder to find, but there were a few here on Audiogon.
The Mullards have a marvelous midrange which makes females vocals "to die for".
I have drawers full of NOS tubes and always go back to the Mullards...
which one should I get first which will give me the best bang for the buck?
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 :)
You might find some added benefit in a bit of power conditioning. Power conditioning does exactly what you want. Smoother upper frequencies. Some do seem to lean out the midrange a bit (really making it tighter, and tighter bass, but it can seem as if that made the lower freq. leaner. IF you have a warm lower end, and don't mind it being made tighter, then i would really recommend a powerline onditioner for your electronics.
If you love the lower end exactly as is, it will be harder to find a great Powerline conditioner that will work for you.
this is only a suggestion to help you find the sound you seek. And i do not endorse any particular conditioner product.
I do own several (furman REF20i, Monster 7000SS, PS Audio P600, PPP), and power cords and also use quartz crystals for power conditioning
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 =)
BTW, I got a question in buying tube. On eBay, there are many single tubes. But most of the time people would need a match pair. The test score provided seems to be different depends on the instrument used. So .. if I buy a single tube, would it be very difficult to find one that match? It seems those score reflects the life of the tube. If I got un-matched tubes, does it means one may die earlier than the other? Or it will affect the sound in a negative way?
Thanks in advance.
There is no best tube, only a best tube that will allow you to achieve the sound that you want. I would suggest living with the pre-amp for a while and then describe in detail what attributes you would like to improve. If you find that your current tube set up is too lush and warm you will get remarkably different tube suggestion if you had posted too dry and analytical.
Since you don't have a tester your better off buying matched pairs from one source not trying to match single tubes that have values from different testers.
Looking at the specifications on your amp it has a gain of 12db. That would point to the 12au7's being your signal tubes as you are calling them. Really they are the first tubes in the gain stage and the 12ax7's are used as drivers. Unless there is a way of drastically reducing the gain of the 12ax7's or they attenuated at the output, but I don't think so. They will both be important. The 5AR4's are rectifiers. They will make a difference but your right for trying the other four first.
I have Mullard 4004 and Telefunken ribbed plates. They both have attributes that I really like. But the tubes that stay in my set-up the most are Full Music 12ax7's. They are really nice tube. IMHO
I think I will give the Psvane 12ax7's a try next. Happy rolling!
RCA 12AU7A clear tops with side getters. You won't need another pair for many years to come. For less money, consider Philips JAN 12au7a.
I just bought a Prologue 3 a little over a week ago. Unfortunately I haven't had as much time to listen as I want to. Kevin said to wait a a few weeks until the pre has had a chance to break in. I am trying to be patient, but have been contemplating tubes to roll. The stock tubes so far seem pretty good. Kevin selects the platinum grade tube for PL line, so they are screened to begin with. I am not sure which tube the x7 or u7 affects the sound more. I think I will shoot him an e mail. The rectifier tube used in the Prologue 3 have a good reliability record, so I am bit reluctant to change that out--but I probably will. The Mullard 5AR4 is expensive, you might want to look at the alternative versions listed in the manual.
If I may ask what is your amp and interconnects and speaker wire. These can greatly influence the sound stage etc.
I bought my unit used and it comes with PrimaLuna brand tube. Actually, they are very good. The whole unit with stock team is a big upgrade from my previous Audible Illusions L1. The AI is very good and a great leap from SS preamp, but I am very impressed with PrimaLuna even with stock tube.
Michaelo, what tube does it comes with your unit?
Detredwings, you get me very interested in the Full Music. I did a google search, it seems it got rave reviews! And price is much more reasonable than Amperex or Mullard NOS tubes. That is the next one on my list.
I still can't find out which one is the signal tube. I will send an email to PrimaLuna to ask.
Instead of guessing call Kevin at Upscale from whence your unit comes from. He knows more about this then anyone answering your thread.
Gte357 which of the two tubes is first in line is not really so important. You can be sure they are both in the signal path. I build tube preamps myself (diy). All the designs I have came across use one stage for gain and one is for drive/impedance matching.
I have not tried the Full Music 12au7's yet. But I'm building an Aikido line-stage preamp and plan to use those in the gain stage. I can't see how you would be disappointed if you tried them.
In my experience with my Rogue 99 preamp and M180 monoblocks the signal tube position, as I call it, definitely provided the dominant signature. This was also my experience with an Ayon Spirit integrated amp. It sounds like you'll have to experiment and see if the same holds true for your preamp.
I bought mine new and it comes with the Prima Luna labeled Sino (China) tubes. Those Full Music tubes seem to be no longer available Grant audio suggest the Psvane 12AU7-T. Do you have a SS or tube Amp? I have a stash of tubes I can roll into the Prologue. I tend to like the RCA black plates or the long plates. The RCA 12au7 black plates are pretty lush tubes you may like them. I e mailed Kevin, but haven't recieved a reply. Will let you know when I recieve his e-mail.