Tube rolling 12AX7As

It takes 6 tubes, 2 each for the preamp stage, the mm phono stage and the mc phono stage. It will take 12ax7's. New old stock Telefunken 12ax7's seem to be popular however when I had mine I enjoyed new old stock Mullards. You do not have to replace all 6 tubes, your phono needs will dictate whether you need to place any good tubes in your phono stages.

Have fun but take your time when removing the cover and the subsequent removal of the tubes. There is a silly and poorly thought out tube "holder" that will require you to remove screws on the left and right of the the tube section so the top tube guide can be removed. Use both hands so you dont drop the screws into the preamp. Dont ask me how I know this can happen.

There are a number of 12ax7 types you could use. Got to
http://www.audiotubes.com/12ax7.htm He has a nice list of different variations of the 12ax7.

If the C2300 is new and breaking in, my advise is to leave it along for a while. If something goes wrong, one of the first questions you will get from any customer service person is "What tubes are you using and where did you get them? ".

12AX7 tubes are also named ECC83. Search both on the web, tons of information out there. Grinnell's posted link above is a great start. Where or from whom you buy from is huge. Keep in mind, New Old Stock {NOS) is hard to prove. Finding the right dealer, someone you feel you can trust is pretty tough. Also, search the audio forums for good tube dealers.

Good Luck!

I'm liking the Psvane 12AX7T-IIs...a relative bargain tube that really sounds great.

There are two reasons to change tubes in an amp. 1) Improve quality of tube and 2)Change the tone of the amp. Different brands of tubes, both new issues or NOS, impart a distinctly different tone. To be sure you get the tube that is best for you, you will have to be able to articulate what it is you want to change.

To do this you will have to listen to your unit for a considerable period of time to learn its sound and know where to take it. So listen and take your time. Come back in 6 months or so and someone will be able to give you pertinent help.

Do so now and you will probably be wasting your money and will go through multiple tube sets before you accidentally find what you like.

I agree with Newbee, if your preamp is new, let the unit and the stock tubes go thru a burn-in period. Otherwise you'll never know the true sound of the preamp and how it integrates into your system.
If you're curious, open it up to see what brand tubes McIntosh has used in your unit. But let the burn-in happen first before tube rolling and during that period you can research the different brands of NOS tubes and their sonic signature.

Newbee and Lowrider are correct. The C2300 is a wonderful unit out of the box and you'll want to know how it matches with everything else in your system before fooling around with changing its sound. Took me about 6 months with mine until I had a good handle on it all.

Thanks everyone for the wonderful replies. I will be heeding the advice. A few things......

The C2300 is not brand new. I have bought it used, with the original owner lightly using it. It has about 10 hours of actual operating time. I am assuming that 10 hours is not enough time for burn-in of the tubes. That leaves me to question, what is a reasonable length of time? 30, 40, 60 hours??

Secondly, for the first few months I will using the C2300 only via the headphone jack. The reason being is now I have to save up for an amp. I slowly but surely want to have a complete McIntosh system, so I am aiming for a completely refurbished MC240 (recapped with updated power supply) or a modern MC275. So I hope this does not seem like a stupid question, but will further burn-in occur while only utilizing the headphone portion of the preamp??

Lastly, about 80% of my music listening is via vinyl. That is why I chose the MC2300, for its phono stage. So if/when I wish to tube upgrade, the MM phono tube will be my main concern.

Either way, I will wait a few months before doing any tube rolling. Once more TYVM everyone for the advice thus far and recommended web sites!

The 12AX7 and 12AX7A is essentially the same tube. In the 12AX7, there are variants used for their quietness, ruggedness and even broadcast and military versions. They even have balanced versions and general upgraded variants.

You'll want to familiarize yourself a bit before shelling out serious money for a NOS Valvo or Telefunken tube. The label often doesn't indicate the tube's origins when dealing with the NOS stuff. I've seen Valvo tubes that were actually Mullards and Amperex tubes that were out of Blackburn as well. There is a way to tell, but don't trust anyone but the most respected sellers until you figure it out if you get the itch to try expensive NOS stuff. North American tubes have similar problems, but they don't usually bring such a premium as the Tele's and Valvos.

As for the burn-in time, I've found that tubes need very little to reach their optimum sound...like less than 20 hours. They will also sound better after being heated for 30 minutes or so.

For what it's worth, if you don't need all the gain of the 12AX7, the lower gain 5751 can really impress and all that I have ever seen are very rugged with closely balanced sections. You wouldn't want to use it in the phono section, but the preamp might like it. There is just way too much gear that uses far too much gain in their designs. Whether or not your Mac falls in that catagory, I don't know.

Congrats on the Mac, btw.

Brad,

a good plan you have there and I admire your patience. Make sure and place the type of tubes in the preamp section that you want to use to flavor your system and you may wish to consider neutral tubes for your phono stage.

Now, I may be setting myself up for a flame or two but there will be some who believe breakin wont completely occur unless your preamp is connected to an amp. They are wrong and likely still live in their parents basement. As a matter of fact, they probably just dropped their video game controller while reading this heresy! LOL.

Brad, I would not worry too much about performing any tube upgrades until you get your amplification sorted and acquired. If I'm not mistaken, the headphone amp of the C2300 is an op amp so the funds spent on NOS 12AX7's might be better utilized presently toward your fund to purchase an amp. In other words, the addition of either amp would be top priority over flavoring the output of your preamp, which you likely would not be able to discern through the headphone outs of a C2300. My 2 cents would be to save for a 275, the 240 being kind of an enigma....not as sweet and lovely presentation wise as MC30's and not as crisp and articulate as the 275 editions. Good luck with your journey.

Telefunken 12ax7 ribbed plates. Deep pocket, Telefunken ecc803s.

The Giant Killing Psvane 12AX7T-II tubes are best bought from a retailer (Canada?) as direct China dealers can be annoying. A tip.

I like the JJ 803S

I'll echo Wolf_garcia in recommending the Psvanes. When I owned the C2300 they were my favorite, and I rolled in plenty of NOS and new production 12AX7. RCA black long-plates from the '50s were also nice in that pre-amp, but they're a bit pricier and harder to source.

I, too, use the Psvanes in my C2300. Grant Fidleity is the outfit I would purchase them from. Get the higher grade tubes.

I too like the JJ 803S having tried all the current 12AX7 and several NOS versions; nicely detailed with great staging and warmth. Not etched or strident at all, great textured bass too. Preferred over current Genalex version IMHO.

Look at the block diagram:
http://www.mcintoshlabs.com/McintoshDocumentMaster/us/c2300om04.pdf

First off, there is a difference between 12ax7 and 12ax7A
"The published difference is that the 12AX7A can be used with heater circuits wired in parallel and series, whereas the 12AX7 can only be used in parallel circuits."

So you need to determine how the heater circuits have been wired before you start. How to tell??? Pull one tube briefly and see if they all go out. Just like Christmas Tree lights. One bulb blows in a series connection they all go out. One bulb blows in a parallel connection, the rest stay on.

If you pull one tube and the rest stay lit, it's wired parallel and you can use either 12ax7 or 12ax7a
If you pull one tube and they all go out, it's series wired and you must us 12ax7a.

The first two tubes do MM phono
The next two tubes do MC phono
The last two tubes do the whole preamp.

The phono tubes (one thru four) should be low noise tubes like 7025 or 7025a
The last two tubes will determine the final character of the sound. Personally, I like NOS Amperex. Tele's are strong but sometimes overbearing. NOS Mullards are also nice, maybe a bit heavy on the bottom end compared to Amperex.
Anything old RCA is great, as are Sylvania's in my opinion.

Roll away, that's the fun of it! It's like changing the strings on a guitar, they all have their own signature sound.