Question about a preamp tube?

[reecebors89]

I think my preamp tube blew up in my SWR 550x, they said that 12AX7A preamp tube are used in them, I've found many different tubes that are very similar, like 12AX7EH and many others, does it matter if they tube is exactly the same or not?

 

[ampcarfan]

I found a thread that had quite a bit of info on this very thing. I think "Chef" is pretty knowledgable on this subject. Might want to do a search.

 

[reecebors89]

thank you, will do

 

[hired hand]

What you are looking for is a 12AX7. The "EH" in your example stands for Electro Harmonix, a brand name of sorts. Any 12AX7 will work in your amp, as will a host of other 12A..... series tubes. The difference will be in the gain structure of the tube, most all others will have a gain rating that is less than a 12AX7, which is probably what you should stick with. There are quite a few modern day AX7's to choose from, each one may sound different to your ears. Some of the notables would be the 12AX7 offerings from JJ, TungSol, and the Sovtek 12AX7LPS.
There is no need for you to spend a lot of money on NOS tubes. Just try a few of the different modern day offerings from one of the reputable on-line tube dealers. These guys buy pre tubes in huge numbers and do a good job of culling the weak components. The number of tubes they reject would surprise you. But that is what is required to be able to sell tubes with a reasonable warranty.
Good Luck

http://www.dougstubes.com/index.html

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http://www.tubedepot.com/

 

[ErnieD]

hired hand thanks for those URL's to search those tube outlets, they'll come in real handy to better research what's available for us.

I read a thread awhile back where a TBer dropped a, IIRC, Tung Sol 12AX7?? Gold Tip tube in his GB Neopak and he stopped using the LF Shape button on his amp.

I have a Neopak and plan to order possibly that same tube, looks to be going for about 25 bucks. I use the LF Shape button constantly on my Neopak. And maybe gain some other benefits along the way, I hope, for their small price. Might pickup another brand or two of tube to compare.