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The Dynaco Tube Audio Forum

Dedicated to the restoration and preservation of all original Dynaco tube audio equipment - Customer support for Tubes4hifi VTA tube amp and preamp kits and all Dynakitparts.com products


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    5R4WGB rectifier tube

    billd
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    billd


    Posts : 7
    Join date : 2015-08-30
    • Post n°1

    5R4WGB rectifier tube Empty 5R4WGB rectifier tube

    Post by billd Tue Aug 21, 2018 7:40 am

    I have a pair of M-125s and currently use Genelex GZ34s that I bought from Jim McShane. Someone I was speaking with here in Bangkok (my home) told me that I could use the 5R4WGB as a replacement for the GZ34. In fact, he recommended it. I looked at the Five Volt Fullwave Rectifier Tube chart that Bob Latino posted. The 5R4 has a much higher voltage drop (67 vs. 17) and a much higher Max PV (900 vs 450).

    My tube knowledge is limited. I'd like to know if the 5R4WGB can be used as a direct replacement and what the differences between the two tubes mean in practical terms.
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    Bob Latino
    Bob Latino
    Bob Latino
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    • Post n°2

    5R4WGB rectifier tube Empty Re: 5R4WGB rectifier tube

    Post by Bob Latino Tue Aug 21, 2018 8:08 am

    billd wrote:I have a pair of M-125s and currently use Genelex GZ34s that I bought from Jim McShane. Someone I was speaking with here in Bangkok (my home) told me that I could use the 5R4WGB as a replacement for the GZ34. In fact, he recommended it. I looked at the Five Volt Fullwave Rectifier Tube chart that Bob Latino posted. The 5R4 has a much higher voltage drop (67 vs. 17) and a much higher Max PV (900 vs 450).

    My tube knowledge is limited. I'd like to know if the 5R4WGB can be used as a direct replacement and what the differences between the two tubes mean in practical terms.

    You CAN use a 5R4 rectifier in the VTA M-125 amp if you want and yes a 5R4 does have a higher voltage drop (Vdrop) than a 5AR4. As such, the amp's overall power level will drop a bit. Whether you will actually notice the drop in power or not, I can't say ? Below is the 5 volt full wave rectifier tube list and the characteristics of each tube ..

    Bob

    5R4WGB rectifier tube Tube_rectifier_comparison
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    billd
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    billd


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    • Post n°3

    5R4WGB rectifier tube Empty Re: 5R4WGB rectifier tube

    Post by billd Tue Aug 21, 2018 8:14 am

    Bob Latino wrote:
    billd wrote:I have a pair of M-125s and currently use Genelex GZ34s that I bought from Jim McShane. Someone I was speaking with here in Bangkok (my home) told me that I could use the 5R4WGB as a replacement for the GZ34. In fact, he recommended it. I looked at the Five Volt Fullwave Rectifier Tube chart that Bob Latino posted. The 5R4 has a much higher voltage drop (67 vs. 17) and a much higher Max PV (900 vs 450).

    My tube knowledge is limited. I'd like to know if the 5R4WGB can be used as a direct replacement and what the differences between the two tubes mean in practical terms.

    You CAN use a 5R4 rectifier in the VTA M-125 amp if you want and yes a 5R4 does have a higher voltage drop (Vdrop) than a 5AR4. As such, the amp's overall power level will drop a bit. Whether you will actually notice the drop in power or not, I can't say ? Below is the 5 volt full wave rectifier tube list and the characteristics of each tube ..

    Bob

    5R4WGB rectifier tube Tube_rectifier_comparison

    Thanks, Bob. That's the chart I was referring to in my post. Since my speakers, Bozak Symphony's, have 93dB sensitivity, I wouldn't expect to notice much difference.
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    peterh
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    • Post n°4

    5R4WGB rectifier tube Empty Re: 5R4WGB rectifier tube

    Post by peterh Tue Aug 21, 2018 9:36 am

    billd wrote:I have a pair of M-125s and currently use Genelex GZ34s that I bought from Jim McShane. Someone I was speaking with here in Bangkok (my home) told me that I could use the 5R4WGB as a replacement for the GZ34. In fact, he recommended it. I looked at the Five Volt Fullwave Rectifier Tube chart that Bob Latino posted. The 5R4 has a much higher voltage drop (67 vs. 17) and a much higher Max PV (900 vs 450).

    My tube knowledge is limited. I'd like to know if the 5R4WGB can be used as a direct replacement and what the differences between the two tubes mean in practical terms.

    5r4 is a direct heated tube, thus the B+ will rise faster then the consuming tubes and the
    B+ capacitor might encounter a short overvoltage.
    In addition, the spec for 5r4(wgb) states that maximum allowed capacitor is 4uF, used in a M125
    it violates this.
    See https://frank.pocnet.net/sheets/127/5/5R4WGB.pdf

    I would advise not to use in a M125
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    billd
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    billd


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    • Post n°5

    5R4WGB rectifier tube Empty Re: 5R4WGB rectifier tube

    Post by billd Wed Aug 22, 2018 4:19 am

    Thanks, Peter. Fortunately, this is an academic question but I am confused since Bob said I can use it but you advise against. I wish I understood more about electronics.

    Njrob likes this post

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