|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
208.179.6.250
Hi Folks,I'm thinking about using 12AT7's in place of the EH 12AX7's in my Cayin TA-30 integrated. I only have a pair of JAN-Philips (early 80's)and some Chinese ones on hand to try. I've heard mixed things about these tubes. Are there better alternatives in this price range? I can't afford Siemens or Amperex.
Follow Ups:
Thanks for the info folks! I've been a guitar player longer than I have been a tube hifi enthusiast and I naturally thought that I could easily sub AT7's in place of the AX7's. I'm actually pretty happy with the stock EH tubes.
The 12AT7 is NOT a sub for the 12AX7, as the others have stated. But the problem does not have to do with gain. The 12AX7 does afford a lot of gain and can be used legitimately in phono stages, as the first voltage amplifier. But if your unit uses a 12AX7 as the linestage tube, that is way overkill with respect to gain. A 12AT7 will still be more than enough in terms of gain, and the 12AU7, with lower gain still, is your best bet. However, you cannot go from a 12AX7 to a 12AT7 OR 12AU7 without modifying the associated circuit elements. The latter two tubes, for one example, require much more current than a 12AX7 for proper performance and are likely to sound dull and rolled off in a circuit optimized for a 12AX7. In summary, although the 12AX7 is not a good choice for a linestage, you should probably continue to use that type unless you know enough to modify the circuit.
12AT7 does not sub for 12AX7 in hifi gear. There is often misinterpreted substitution info because this forum is used by both hifi and guitar amp folks. Tube guitar amp guys WANT extra distortion or some other "effect" by subbing tubes; that advice is often not valid for hifi gear. Use a 12AX7. Type 5751 is the only sub I would even try, but really, use a 12AX7. They are cheap and they are everywhere. If you are on a budget, www.vintageelectron.com has ElectroHarmonix 12AX7, Shuguang 12AX7, and sometimes Sovtek LPS 12AX7/ECC83 for $5-$7 each, tested for microphonics and noise on a VTV "valve charcterizer". That's a HELL of a deal! Don't be afraid of ebay; bid superlow on a number of less popular brands from popular, good feedback sellers (i.e. check for "Baldwin" labeled RCA and Raytheon, Philco, Zenith, and Admiral labeled RCA and early GEs, and Hammond, Fisher etc labeled Dutch Amperex and Mullard) I have won such tubes for as little as 50 cents and never more than $5! If the selling price goes above that, I just wait a day or two and try again. You will get some noisy tubes that you will have to throw away, but they will not damage your amp and you will wind up with some wonderful tubes at rock bottom $. For the sure thing, check out Vintage Electron.
Pat S,I don't know the Cayin integrated, but 12AT7s can not (as far as I know) be used where 12AX7s have gone before. The 12AX7s is typically the principal preamp gain tube and a 12AT7 will not work in that position as it does not amplify the signal enough. I don't know the actual figure, but an AT may provide only 20% of the gain of an AX- but don't quote me! Check with the maker in case this substitution can be made, but I doubt it.
If indeed you are going to be using 12AT7s, I found the probably worst tubes I've ever owned were 80's Philips ECG 12AT7s- harsh little nasties they were too. My favourite general 12AT7 is the regular Siemens ECC81, but the 6201 type is usually quieter and I am really enjoying a pair of Valvo (Philips, Hamburg made, gold pin 6201s).
But, if you need 12AX7s, these are fundamentally important items to so many pieces of tube gear and there are many, many choices. And competition for the known nice ones can make these expensive. Really good NOS ones like the Amperex Bugle Boy can start at $50 and Telefunken ECC803S can be $250-500 each. The first thing is verify to identify how you would like to steer the sound and then look for tubes that have a reputation for producing that effect.
Check to see which type you really need then I would suggest spending a little time in the search/archive section on this site. There are probably 10,000 posts concerning 12AX7s!
Please write again when you have narrowed your needs a bit and I'm sure we can provide a few dozen conflicting opinions!
Cheers,
This post is made possible by the generous support of people like you and our sponsors: