[geowak]

I had some problems with my integrated tube amplifier as I had posted earlier. It was fixed and the tube socket under the tubes fried and was replaced. Also one of three transformers needed replaced. It got me to think and worry about my NOS tube choices. So here are the tube questions.

Are these two types of tubes equivalent.
12BH7 12BH7A
12AX7 12AX7A 12AX7WA ECC83S JAN-5751 12AU7 12AU7A

My amp requires a pair of 12BH7 and a pair of 12AX7. It is a push pull tube amp.

Thanks in advance for all answers.

[FullRangeMan]

I had some problems with my integrated tube amplifier as I had posted earlier. It was fixed and the tube socket under the tubes fried and was replaced. Also one of three transformers needed replaced. It got me to think and worry about my NOS tube choices. So here are the tube questions.

Are these two types of tubes equivalent.
12BH7 12BH7A
12AX7 12AX7A 12AX7WA ECC83S JAN-5751 12AU7 12AU7A

My amp requires a pair of 12BH7 and a pair of 12AX7. It is a push pull tube amp.

Thanks in advance for all answers.

Two tubes? You mention nine tubes.

12ax7 = gain around 100x
12au7 = gain around 20x
12bh7 = Gain around 15-20+ according manufacturer.

For HV values see site below, it may not be the same:
http://www.mif.pg.gda.pl/cgi-bin/vs4.pl

http://www.mif.pg.gda.pl/cgi-bin/vs4.pl
Or get the book:
http://www.amazon.com/Tube-Substitution-Handbook-Barry-Buchanan/dp/0790611481

[geowak]

I had some problems with my integrated tube amplifier as I had posted earlier. It was fixed and the tube socket under the tubes fried and was replaced. Also one of three transformers needed replaced. It got me to think and worry about my NOS tube choices. So here are the tube questions.

Are these two types of tubes equivalent.
12BH7 12BH7A
12AX7 12AX7A 12AX7WA ECC83S JAN-5751 12AU7 12AU7A

My amp requires a pair of 12BH7 and a pair of 12AX7. It is a push pull tube amp.

Thanks in advance for all answers.

FRM

Thanks for lending a hand. Maybe I should clarify my question.
Are these two tube types or classifications the same? (functionally) 12BH7 12BH7A
Are these seven tube types or classifications the same? (functionally) 12AX7 12AX7A 12AX7WA ECC83S JAN-5751 12AU7 12AU7A

I tried your links but nothing appeared on the page.

[JackD]

The two "groups" are the same functionally, but if you use anything with lower gain like the 5751 or AU in the AX slot you will lose fairly significant amount of gain.  Many times the letters that appear behind the numbers refer to military contracts or grading levels.

[Escott1377]

These are all small signal input tubes with the same pin out.

Please tread careful with this next statement since it is your gear .  The lower gain tube 12au7 should not cause any harm to the circuit since it is providing less current.

You may however, run into an issue if subbing a 12ax7 where a 12au7 is required.

The other nomenclature you list are just different branding of the same tube.

i have had success subbing a 12av7 or 12at7 in the same scenario.

[FullRangeMan]

FRM

Thanks for lending a hand. Maybe I should clarify my question.
Are these two tube types or classifications the same? (functionally) 12BH7 12BH7A
Are these seven tube types or classifications the same? (functionally) 12AX7 12AX7A 12AX7WA ECC83S JAN-5751 12AU7 12AU7A

I tried your links but nothing appeared on the page.

12BH7 & 12bh7A= according this database they are the same.
Please search 12bh7 in this link:
http://www.mif.pg.gda.pl/homepages/frank/vs.html
You will see 12bh7 and 12bh7a are in the same group page.

The second group have three sets:
12AX7 12AX7A 12AX7WA = Gain around 100x
5751 = Gain around 70x
12au7= Gain around 16 to 20x according the manufacturer

As you see in this db there is many types and manufacturer of the same tube.
Before put a tube in your amp do a detailed search and get the bliss from your tube broker.

[geowak]

Guys... this is the info I needed. Thanks

FRM

That link is a great resource. Thanks for the info.

Also when testing a 12BH7 and a 12AX7 on a tube tester using that set data, can one test an equivalent tube like a 12BH7A or 12AX7A?
Can the results be considered the same? Even if the tube will be of a lesser or greater gain?

[FullRangeMan]

Guys... this is the info I needed. Thanks

FRM

That link is a great resource. Thanks for the info.

Also when testing a 12BH7 and a 12AX7 on a tube tester using that set data, can one test an equivalent tube like a 12BH7A or 12AX7A?
Can the results be considered the same? Even if the tube will be of a lesser or greater gain?

I no even own a tube tester, but I would not consider the same 100% for audio use.
In this case one must report to the info chart table from the tester to check over.

[JackD]

The letters that appear behind the numbers, in this case the 7, are designations for contract specs or grading levels for microphonics or durability.  The tubes themselves structurally are the same.