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Post subject: Re: Current 12AX7 Comparison
Posted: Fri Jul 12, 2013 4:25 am
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Aspiring Musician
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Location: australia
Dont mind the tung sol 12ax7 for v1..But you cant beat 1960-70s RCA or GE 12ax7 For Tone..5751 GE 5 star There Pretty Good to..If you can find them...Cheers From Aus..


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Post subject: Re: Current 12AX7 Comparison
Posted: Fri Jul 12, 2013 2:42 pm
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The title of this thread is "Current 12AX7 Comparison" so I'm not sure why we are now discussing NOS tubes.

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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 7:46 am
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Three of my favorite reissue 12ax7's are the tung sol, mullard, and Sovtek lps. These three tubes can definately deliver the goods with the sovtek lps having the best gain of the three. Just keep the lps out of the phase inverted, it doesn't seem to like it very much and have had two go bad in that position, really fast. I don't think they like being worked very hard.
Looking at the Mullard in comparison to the sovtek, they both share very similiar structures. Could it be that the Mullard is a rebranded sovtek made to their specifications? Maybe that's why I like it so much. I'm thinking I prefer long plates over others as well. I've also tried the JJ ecc803s, another long plate, and found that tube to be a pretty good tube as well. Thing is, that one didn't last very long either. What is it about long plates that makes them unreliable? That's the only reason I've held back on ordering any more sovtek or JJ long plates.

Edit:
Found this on the tube depot web site.
" The Tung-Sol brand name is now owned by New Sensor Corporation, which is the same company as Sovtek, Electro-Harmonix, Mullard and Gold Lion."
At least now I understand why I favor the Mullard and Sovtek long plates as well as the tung sol so much. :D

Bluesky
"The title of this thread is "Current 12AX7 Comparison" so I'm not sure why we are now discussing NOS tubes."

I get what your saying but had the title of this thread been "12AX7 Reissue comparisons" then I would understand the point your trying to make. But since it reads as "current", then I could reasonably apply any 12ax7 that is "currently" available on the market to this thread, NOS included. So I could see how some might make that assumption. Don't you agree? :wink:

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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 9:25 am
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socal323 wrote:
Don't you agree? :wink:


No.

The title of the page I linked to is "A COMPARISON OF CURRENT PRODUCTION 12AX7 TUBES". That does not include NOS tubes of which there is plenty of discussion about.

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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 11:16 am
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" Just keep the lps out of the phase inverted, it doesn't seem to like it very much and have had two go bad in that position, really fast. I don't think they like being worked very hard. "

You aren't putting a 12AX7 into the phase inverter position that normally uses a 12AT7?

Just wondering...


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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 12:36 pm
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Good question BMW. The reports that I've seen are particularly positive for the LPS in the PI position. :?:

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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 1:32 pm
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BMW2002Ti wrote:
" Just keep the lps out of the phase inverted, it doesn't seem to like it very much and have had two go bad in that position, really fast. I don't think they like being worked very hard. "

You aren't putting a 12AX7 into the phase inverter position that normally uses a 12AT7?

Just wondering...


Yes, I was, :cry: but only because some vacuum tube sellers praise them in that slot. I tried it and well, they failed. I learned my lesson, and personally I don't think they're suited for that slot.
However, in V1 and V2 they perform very well. I don't run a combo amp so I didn't experience any of the micro phonics or noise that some reviews say they exhibit.

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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 1:37 pm
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shimmilou wrote:
Good question BMW. The reports that I've seen are particularly positive for the LPS in the PI position. :?:


Yeah, me too. But I won't dare brave installing them in that slot anymore. Actually, as I recall, they only went bad on the trri I had. I haven't tried them in my bandmasters so maybe it was only with that amp......oh I don't know and honestly with the current price of tubes, I don't care to find out. :wink:

Anyways, I still prefer tungsol, Mullard, and sovtek lps in the preamps. I might give the JJ ec803s another try. I recall positive results with that tube other than early failure.

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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 2:03 pm
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This could be the reason for early 12AX7LPS failure. In general, it's ok to sub a 12AT7 into a 12AX7 position. But, you need to be careful putting a 12AX7 into a 12AT7 slot.

Manufacturers use the 12AT7 or 12AU7 in PI and reverb driver positions because they can handle higher idle bias current than the 12AX7 types. This is useful in many long-tailed phase inverters. Ubiquitous in many blackface and silverface Fender amps. And carried over to most of their reissued amps.


http://www.webphix.com/schematic%20heav ... manual.pdf


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Post subject: Re: Current 12AX7 Comparison
Posted: Sun Jul 14, 2013 9:17 pm
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BMW2002Ti wrote:
In general, it's ok to sub a 12AT7 into a 12AX7 position. But, you need to be careful putting a 12AX7 into a 12AT7 slot.


+1

Similar circumstances apply to the 5751 as well.

Arjay

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