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12ax7LP substitute

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TFMStudios

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Joined 2011
#1
Hello All,

First post here. I did a search and couldn't find anything specific.

Bought a Behringer Untragain Pro 2200 Mic preamp uses. It has a single 12ax7LP Sovtek. I was getting a little crackling and since I have some really nice tubes I thought I'd change it.

So the specs say it's a 12ax7 but when you crack open the case (which isn't easy) it's actually a 12ax7LP. My question is can I swap a different tube in it's place and which would be the best choice. Here's what I have available.

(2) Sylvania Green label 5751 Triple Mica, double support rod.
(1) Sylvania 12ax7a halo
(1) Sylvania 12ax7WA green label (military spec).
(1) GE/Hammond 12au7 halo
(4) 12ax7 from a Lowery Organ (Halo)
(2) RCA 12ax7a halo.

Which one would be the closest match to this Sovtek 12ax7LP?

Thanks for your input,

Mike
 
#2
TFMStudios said:
Hello All,

First post here. I did a search and couldn't find anything specific.

Bought a Behringer Untragain Pro 2200 Mic preamp uses. It has a single 12ax7LP Sovtek. I was getting a little crackling and since I have some really nice tubes I thought I'd change it.

So the specs say it's a 12ax7 but when you crack open the case (which isn't easy) it's actually a 12ax7LP. My question is can I swap a different tube in it's place and which would be the best choice. Here's what I have available.

(2) Sylvania Green label 5751 Triple Mica, double support rod.
(1) Sylvania 12ax7a halo
(1) Sylvania 12ax7WA green label (military spec).
(1) GE/Hammond 12au7 halo
(4) 12ax7 from a Lowery Organ (Halo)
(2) RCA 12ax7a halo.

Which one would be the closest match to this Sovtek 12ax7LP?

Thanks for your input,

Mike
Click to expand...

Any of those, except the 12AU7, will be very close. The 5751 is spec'd for slightly lower gain but, in practice, may be within tube to tube variation of the other AX7 types. Try em, and see what you like.

Sheldon
 
#3
The 12au7 is a low output tube. I went with the One of the Lowery tubes. I just wanted to make sure there was no big mismatch. From what I could find, the Sovtek 12ax7LP is exactly the same as a regular 12ax7. They just add the "LP" to be fancy. It's a crappy Russian tube no matter how you slice it.

Thanks for your input,

Mike
 
#5
TFMStudios said:
The 12au7 is a low output tube. I went with the One of the Lowery tubes. I just wanted to make sure there was no big mismatch. From what I could find, the Sovtek 12ax7LP is exactly the same as a regular 12ax7. They just add the "LP" to be fancy. It's a crappy Russian tube no matter how you slice it.

Thanks for your input,

Mike
Click to expand...

While you may have had a bad specimen, the Sovtek 12AX7LPS is anything but bad. AAMOF, the 'LPS is better than much of the remaining NOS. The difference between the 'LP and 'LPS is a spiral wound, hum bucking heater, which makes the 'LPS a genuine 7025 equivalent. The 'LP should not be used in an AC heating situation.

New Sensor "cloned" the Siemens long plate, hence the LP designation. This time, they got it right. If you have a 12AX7 based phono section, you would be very hard pressed to do better than the clean and QUIET Sovtek 12AX7LPS.
 
#6
Eli Duttman said:
While you may have had a bad specimen, the Sovtek 12AX7LPS is anything but bad. AAMOF, the 'LPS is better than much of the remaining NOS. The difference between the 'LP and 'LPS is a spiral wound, hum bucking heater, which makes the 'LPS a genuine 7025 equivalent. The 'LP should not be used in an AC heating situation.

New Sensor "cloned" the Siemens long plate, hence the LP designation. This time, they got it right. If you have a 12AX7 based phono section, you would be very hard pressed to do better than the clean and QUIET Sovtek 12AX7LPS.
Click to expand...

Agree.
 
#8
Eli Duttman said:
While you may have had a bad specimen, the Sovtek 12AX7LPS is anything but bad. AAMOF, the 'LPS is better than much of the remaining NOS. The difference between the 'LP and 'LPS is a spiral wound, hum bucking heater, which makes the 'LPS a genuine 7025 equivalent. The 'LP should not be used in an AC heating situation.

New Sensor "cloned" the Siemens long plate, hence the LP designation. This time, they got it right. If you have a 12AX7 based phono section, you would be very hard pressed to do better than the clean and QUIET Sovtek 12AX7LPS.
Click to expand...

I've a very long history with this tube, and have got to agree completely with Eli on this one. I've got 7+ yr old LPS that still measure well within acceptable parameters after many thousands of hours of use in the error amplifiers of the regulated power supply that feeds my power amp. They also seem to work just fine in phono stages, sound good and are quieter than most alternatives. As Eli indicates the LP should not be used in AC heated applications, but otherwise performs as well as the LPS.
 
#10
I agree about the 12AX7LPS , a really good 12AX7.

My behinger started crackling .. mine had some short plate chinese 12AX7 in it ... it's now got a 12AXLPS in it ... although that didn't sort the crackling, which was some poor soldering on the socket pins.
 
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