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12ax7/12AT7 Recommendations

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I have an A.R.T Dual Tube Parametric EQ that uses 12ax7a tubes. The present tubes say Phillips ECG 8752 aja, Jan 12at7wc

I am not well versed on tubes so I have some (silly) questions:

1) Are all 12ax7a tubes the same in regards to their use? In other words, is a 12ax7 the same as a 12ax7a? What does the "a" at the end mean?

2) For audiophile purposes, what tubes would be recommended for this type of application?

What little I know about tubes tells me that they can have different characteristics, like low/high distortion. Some tubes sound more "tubey" than others. Some are warmer than others. So I may need help defining what type of tube, or the sound I want from them. But going on what I know to this point, id say:

a) low distortion
b) lots of midrange warmth
c) as transparent as possible
d) moderate as to how "tubey" they sound.
e) under $75 a pair?

any suggestions?

The people art A.R.T. recommended Electro-Harmonics tubes.

I am looking for high quality. To improve over the original tubes.
 
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The "A" at the end of 7 and 9 pin mini types indicates controlled heater warmup time, which is relevant only in series strings of dissimilar types, as was found in tubed TV sets.

Reasonable price and good midrange = "reissue" Mullard long plate 12AX7s out of Saratov, Russia. The EH 'X7 is OK in a combo guitar amp, but ... FWIW, the EH labeled tube comes from Saratov too. ;)
 
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So far the
Genalex Gold Lion 12AT7 / ECC81 / B739


Look good. Opinion?

That's not a 12AX7 is it?

IMHO tube rolling is over rated. Though I enjoy owning rare NOS tubes, honestly I have a hard time hearing a big difference.

Granted...I've never tried the cheapest Chinese types and I'm sure there are brands that are bad, but I've had good and bad Sovteks and I've had good and bad Telefunkens.

Sorry no help here...I'd get some JAN 12AX7s since they are usually not THAT costly but still NOS, or I'd stick to the recomended EH.
 
That's not a 12AX7 is it?

IMHO tube rolling is over rated. Though I enjoy owning rare NOS tubes, honestly I have a hard time hearing a big difference.

Granted...I've never tried the cheapest Chinese types and I'm sure there are brands that are bad, but I've had good and bad Sovteks and I've had good and bad Telefunkens.

Sorry no help here...I'd get some JAN 12AX7s since they are usually not THAT costly but still NOS, or I'd stick to the recomended EH.

http://www.worldtubecompany.com/mm5/merchant.mvc?Screen=TF-2

[FONT=Monotype Corsiva, Arial, Helvetica][FONT=Arial, Helvetica] What tubes can you substitute or replace for a 12AX7?
ANSWER - You can substitute a 12AX7 for a 12AT7, 12AU7, 12AY7 or a 7025. But what are the differences? It depends on which tube you are replacing. Let's assume it is the first preamp tube.

12AT7 * * * * The 12AT7 is a clearer sounding tube than a 12AX7 but with a little less gain.
12AU7 * * * * The 12AU7 sounds like a 12AX7 but produces a lot less gain in the preamp circuit.
12AY7 * * * * The 12AY7 sounds warmer with more bottom end to it than a 12AX7.
7025 * * * * The 7025 has a higher gain than a 12AX7 tube. It is also a crisper sounding tube. This is the industrial version of the 12AX7. You can beat the crap out of it and it will still go!



This is the clearest explanation I have read so far as to the differences between different 12ax7 types.

I am leaning towards the "AT" type given thats what was in the unit to begin with.

[/FONT][/FONT]
 
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That is weirdly, bizarrely, totally incorrect information. Wow. These are all TOTALLY different types of tubes. You won't cause a fire substituting one for another, but your equipment will not work right (gain, bandwidth, distortion, and noise will be badly affected).

OK, so since my original tubes are Phillips Jan 12at7wc, the 12AT7 types is what I need to limit myself to look at, yes?

I posted the above to see if it was accurate, if it is not, I thank you for pointing it out.
 
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I'm confused based on multiple comments on this thread about 12AT7 and 12AX7, just because there are 12AT7s installed in the equalizer now does not mean that is the correct tube if ART Audio says it should be 12AX7.. So which is it?

SY is right on the money about those tube comments.. All rubbish..:D
 
I'm confused based on multiple comments on this thread about 12AT7 and 12AX7, just because there are 12AT7s installed in the equalizer now does not mean that is the correct tube if ART Audio says it should be 12AX7.. So which is it?

SY is right on the money about those tube comments.. All rubbish..:D

I just sent A.R.T. another email to clarify the issue as to 12ax7 or 12at7. Whats in the unit says 12at7, but their literature says 12ax7a.
 
This gets weirder and weirder: the OP stated "I have an A.R.T Dual Tube Parametric EQ that uses 12AX7A tubes"

He somehow confounded the 8752 date code with a 8752 tube number which he believes for some reason is a 12AT7. None of my tube manuals list a 8752 and Fathauer's _Electron Tube Locator_ lists no 8752: there is no such tube!

This guy needs a 12AX7 not a 12AT7; he states it in his original post!
 
This gets weirder and weirder: the OP stated "I have an A.R.T Dual Tube Parametric EQ that uses 12AX7A tubes"

He somehow confounded the 8752 date code with a 8752 tube number which he believes for some reason is a 12AT7. None of my tube manuals list a 8752 and Fathauer's _Electron Tube Locator_ lists no 8752: there is no such tube!

This guy needs a 12AX7 not a 12AT7; he states it in his original post!

Here is what the tube says that I pulled out of the unit, line by line exactly:

JAN 12AT7wc
Phillips ECG 8752 aja
34167 usa

I stated, initially i needed a 12ax7a because (before i opened the unit and pulled the tubes) i was going by what the instruction booklet says for the unit, which is:

12ax7a

Yes. The two do not match and I am trying to find out from ART which is right.

I am sorry for the confusion, but with the owners manually specifying 12ax7a, I expected to find a 12ax7a inside. I didnt, I found a 12at7 instead.

http://artproaudio.com/files/owners_manuals/om_dualtubeeq.pdf - This is the manual for the unit.
 
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Even with this issue in doubt, we can continue. Both are readily available. I have emailed Jim McShane and Galen Carol and they both recommended a Mullard CV4024/12AT7 NOS. I assume I can also get this as a 12ax7 if needed.

What do folks here think of this tube?
 
I think I see what the source of the confusion is. That EQ is a recording effects box.

Is it this piece?:
http://artproaudio.com/files/owners_manuals/om_dualtubeeq.pdf

If it is, it uses "Hand-selected 12AX7a tubes."

If that's the case, you want to use 12AX7, 12AX7A, 7025, ECC83 or maybe even 5751. But using 12AT7 would be a "mod" - and would certainly not help make it any more "hi-fi."

--

Yup. Same as the link I posted above. I am only trying to put into it what its designed to use. I already know what the manual says. But thats not what I found in it when I opened it up.
 
and you dont know what else may have been changed
it may be 'readjusted' to the 12AT7
who knows

I think the recomended Mullard may be a special long plate
maybe its low microphonic, or something ?

It sounded fine with the Phillips JAN 12at7wj. If it was modifiied, I see nothing on the circuit board (like messy solder points) that might suggest it.

Ive owned this unit 4 years, and having bought it used, no telling how much time was on the tubes before I had it. So I felt it was time to replace them. And lets upgrade to better tubes while im at it.

For clarity, I AM trying to improve the sound, but not through changing the 12xx type, but rather by an improved version of what the unit is suppose to have.

I have found the very tubes I pulled out of it for about $14 a piece. I will go up $40 a piece. Surely I can better the performance for this much?
 
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