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    Tube Rectifier Question

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    Dheick

    Posts : 13
    Join date : 2012-01-10

    Tube Rectifier Question

    Post by Dheick on Thu Jan 12, 2012 8:49 am

    Has anyone tried using an 83 rectifier tube in there st120 amp? Would the 83 tube work ok in the 125 mono block? It would take alittle modification but I hear they are a really heavy duty rectifier. I'm thinking of building a pair of the 125 mono blocks but I really don't want to use the copper caps. I like the tubes. Just wondering if the 83 would be strong enough for it? or is it a bad idea all together? The other thought I had was what if you put in 2 5ar4 tubes in parallel. Would the 125 mono block transformer be able to handle it?

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Tube Rectifier Question

    Post by Bob Latino on Thu Jan 12, 2012 10:33 am

    A Weber WZ68 has a 450 milliamp current flow rating - the same as the current flow rating on the power transformer on each M-125 monoblock.

    A GZ34 tube rectifier is rated at 250 milliamps
    An 83 tube rectifier is rated at 225 milliamps

    Both the GZ34 and the 83 rectifier (IMHO) cannot flow enough current to satisfy the current needs of an M-125 using four output tube. Using the TWO output tube option on the M-125, either the GZ34 or the 83 will work fine. I have used a GZ34 tube rectifier with the two output tube option on the M-125's but never an 83 - although it should work.

    Using two GZ34's as you suggest would require more space on the chassis and would be no better than the single Weber WZ68. Note that all higher powered (125 watts and above) tube amps all (to my knowledge) use solid state rectifiers due to a tube rectifier's inability to deal with the higher current flows required of larger tube amps.

    Keep in mind that Dynaco themselves used solid state rectifiers in their later tube designs - the ST-35 power amp and the SCA-35 integrated amp. Solid state rectifiers have three advantages over tube rectifiers.

    1. They don't draw filament current like a tube rectifier which saves a few milliamps which would be required to heat the 5 volt filament of the tube rectifier. This makes it easier on the power transformer.

    2. They have greater "forward flow" and don't drop the B+ as much as a tube rectifier

    3. They "sag" the B+ voltage much less at higher current demands and will be able to flow more current at higher current demands.

    The one minor disadvange of a solid state rectifier is the instant application of high voltage because it doesn't have to "warm up" like a tube rectifier. This can be dealt with by simple delay systems (3 to 5 seconds) as built in to the Weber WZ68. You can also consider the VTA TDR (Time Delay Relay) which has a 17 second delay built in before high voltage is applied.

    Bob

    Dheick

    Posts : 13
    Join date : 2012-01-10

    Re: Tube Rectifier Question

    Post by Dheick on Thu Jan 12, 2012 2:07 pm

    Thanks for the reply







    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Tube Rectifier Question

    Post by mantha3 on Thu Jan 12, 2012 8:10 pm

    What is a GZ33 and a GZ37 rated for in milliamps again?

    mantha3

    Posts : 298
    Join date : 2010-11-10

    Re: Tube Rectifier Question

    Post by mantha3 on Thu Jan 12, 2012 8:14 pm

    I think a GZ34 and a GZ37 are both 125 milliamps and a GZ33 is 250 milliamps (High current)


    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: Tube Rectifier Question

    Post by Bob Latino on Thu Jan 12, 2012 8:37 pm

    Below is a comparison of various tube rectifiers ... A GZ33 according to some other info I have here is rated at 250 milliamp current flow without a choke input and 300 milliamps WITH a choke input.

    Bob



    Dheick

    Posts : 13
    Join date : 2012-01-10

    Re: Tube Rectifier Question

    Post by Dheick on Fri Jan 13, 2012 7:38 am

    Verry nice comparison chart. Thanks for posting it.

    burnedfingers

    Posts : 31
    Join date : 2009-05-06

    Re: Tube Rectifier Question

    Post by burnedfingers on Sat Jan 14, 2012 8:15 am

    You could use a damper diode tube in conjunction with the SS rectifier. This will allow you a slow B+ ramp on like a 5AR4 does. Its the best of both worlds in my opinion.

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