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Thread: 5AS4A acceptable Sub For 5U4G ?

  1. #1
    HJW
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    5AS4A acceptable Sub For 5U4G ?

    I found some info advising a 5AS4A is a substitute for a 5U4GB. Is the 5AS4A ok to replace a 5U4G ?

    tia

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    HJW
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    Really trying to do my homework on this. Am I correct in assuming the data suggests the 5AS4A is indeed an acceptable substitute ?

    http://www.r-type.org/pdfs/5u4g.pdf

    http://tubedata.milbert.com/sheets/106/5/5AS4A.pdf

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    I have an old GE 5U4GB, both the box and the tube are labeled 5U4GB and 5AS4A.

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    Quote Originally Posted by HJW View Post
    I found some info advising a 5AS4A is a substitute for a 5U4GB. Is the 5AS4A ok to replace a 5U4G ?

    tia
    Best site I know to answer such questions:

    5AS4A, Tube 5AS4A; Röhre 5AS4A (5AS4A)

  5. #5
    HJW
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    Thanks guys. I know the 5AS4A is a sub for a 5U4GB. Most sub charts I've found don't list the 5U4G and 5AS4A as = , but a couple of them do.

    What values on these data sheets is of most importance in determining substitutions ?

    If I'm reading the data right on the tubes in question, it appears the 5AS4A is simply a more robust/efficient tube whereas the 5U4G has more sag.

    Or am I way off base here ?

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    Quote Originally Posted by HJW View Post
    If I'm reading the data right on the tubes in question, it appears the 5AS4A is simply a more robust/efficient tube whereas the 5U4G has more sag...
    Checking in my GE Essential Characteristics book, both tubes (5U4GB and 5AS4A) have the same electrical specs.

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    HJW
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    Quote Originally Posted by JoeM View Post
    Checking in my GE Essential Characteristics book, both tubes (5U4GB and 5AS4A) have the same electrical specs.
    Hi Joe, fair enough, it'll work. Thanks for taking time to check it

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    5AS4A Substitute for 5U4GB

    I have a copy of the RCA Receiving Tube Manuals, RC-24 and RC-28
    both manuals refer to the 5U4GB for maximum ratings, typical operation, and curves.
    Both the 5AS4A and the 5U4GB tube base connections are the same.
    My tube substitution manual has the 5U4GB as the substitute for the 5AS4A full wave rectifier tube.
    I would think from three sources that the substitution is correct.

    Jay D.

  9. #9
    HJW
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    Quote Originally Posted by Jay D View Post
    I have a copy of the RCA Receiving Tube Manuals, RC-24 and RC-28
    both manuals refer to the 5U4GB for maximum ratings, typical operation, and curves.
    Both the 5AS4A and the 5U4GB tube base connections are the same.
    My tube substitution manual has the 5U4GB as the substitute for the 5AS4A full wave rectifier tube.
    I would think from three sources that the substitution is correct.

    Jay D.
    Ok, thanks Jay.

    All the sub charts I found say the 5U4GB and 5AS4A are interchangeable. I'm new to all this specs stuff. But I'm replacing the 5U4G, not a 5U4GB, with the 5AS4A. What confused me was that the majority of charts showed the 5AS4A as a sub for the 5U4GB, but not the 5U4G. Only 2 I found did.

    Am I correct in assuming the 5U4G is an upgrade from a 5U4, and a 5U4GB is an upgrade from a 5U4G ?

  10. #10
    Noodle of Reality Steve Conner's Avatar
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    G means glass bottle. Some tubes (like the 6L6) originally had metal can envelopes, and glass versions of them were brought in later, with the G added to distinguish them.

    A, B, C, etc. means a new, improved version which is still backwards compatible, and so can take the place of the old one. A 6L6GC will work in a circuit designed for an original metal can 6L6, or a 6L6G. But the original tube might not work in a circuit designed to take advantage of the higher ratings of a 6L6GC.
    "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

  11. #11
    HJW
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    Quote Originally Posted by Steve Conner View Post
    G means glass bottle. Some tubes (like the 6L6) originally had metal can envelopes, and glass versions of them were brought in later, with the G added to distinguish them.

    A, B, C, etc. means a new, improved version which is still backwards compatible, and so can take the place of the old one. A 6L6GC will work in a circuit designed for an original metal can 6L6, or a 6L6G. But the original tube might not work in a circuit designed to take advantage of the higher ratings of a 6L6GC.
    Hi Steve, thanks for explaining that. Now I know. I'm getting my head wrapped around this stuff finally. I went ahead and put the 5AS4A in the amp, and it works fine. Quieted down a bit.

    Last night I put a Russian TungSol 12AX7 in where someone had put a Amperex Holland 12AU7. The schematic shows a 12AX7 is supposed to be there. Also pulled a very noisy EH 12AX7 an replaced it with a TS. There is also an RCA 12AX7 I left be for now. I replaced the Sovtek EL34's with TungSol EL34B's. What hum is there has dropped dramatically. I pulled the CU10 which is the reverb tube, and a lot of the hiss is gone. They are cheap, so I'll order a couple NOS ones and try them. The amp calls for 3 12AU7's, and I've got 4 counting the one someone had in the 12AX7 socket I mentioned above. They are all Amperex Holland. What little hum is left, I can live with, but I'll swap the 12AU7's around and see if it gets any quieter.

    I may take the internal speaker out as well, since I'm not running it anyway. Getting that magnet out from in between the two chassis and away from the wiring might help. It will certainly make it easier to carry the amp around, and I can take the old rattly casters off too. More weight gone.

    We'll see.

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