Retrofit a tube rectifier in place of SS?

Discussion in 'Amps and Cabs' started by soniq7, Jun 24, 2008.

  1. soniq7

    soniq7 Member

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    I have a 2x6L6 fixed bias amp with full wave SS rectifier (2 diode). Im toying with the idea of fitting a 5AR4 tube. Just to see how its sounds. You understand I hope.


    So my question:

    Who can comment on tube rectifier conversions?


    Thanks!
    Soniq
     
  2. pula58

    pula58 Silver Supporting Member

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    Let me preface this: I am just learning about this kind of stuff. So, take my advice with a grain of salt!

    your amps transformer (the power transformer) needs to have 5V heater output capable of supplying the necessary current (as much as several amps) to the heater pin of the rectifier tube. So, if your amps power transformer has a 5V heater output you need to make sure you don't fry the power transformer by pulling too much current out of it (you will exceed its power rating). That is: make sure the power trasnformer has a 5V output with enough current driving capability!

    If your amps power transformer does not have a 5V heater output, then, unless you get a new power transformer I don't think it is possible to use a tube rectifier! Maybe there is a halfway in between solution of using a weber "copper cap." I have never used one to see how it affects the sound, but I know it comes as a "tube" you can plug into a rectifier socket (but it has no heater and so your power transformer would be no problem), or, they have another one that is not a tube-like thing, but rather, a module that goes inside your amp chassis.

    Or, I guess you could put a power resistor after the diodes and beofre the first filter caps and that would give you some sag-like behavior. I think that is essentially what the Weber device is: A power resistor and some other passive devices.

    Anyone else?
     
  3. doctord02

    doctord02 Member

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    Thats a lot of work for a whim. You will need to add a 5 volt 3 amp transformer just to power the tube and you will need to punch your chassis for an octal tube socket. Say goodbye to any resale value on the amp. If you want to be able to switch between the two rectos, then theres some additional wiring to be added, as well as drilling a panel for the switch, which has to be a very heavy duty switch that can handle the full voltage and current your PT produces.
     
  4. mr.blacksummer

    mr.blacksummer Member

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    don't do it!!
    the ss recto is so much more solid and stable...and it won't (arguably, I suppose) really help the sound of the amp. plenty of good amp builders are bypassing the tube rectifier these days...(take my Reeves Custom 30 for instance). I'd spend more time switching out the existing pre and power tubes...now THAT can dramatically change the sound and feel of the amp. just offering up my opinion, even though I'm sure you know what you're doing. good luck!
     
  5. soniq7

    soniq7 Member

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    Thanks all. Please stay on topic. Have you any direct experience in rectifier conversions?

    Soniq
     
  6. Blue Strat

    Blue Strat Member

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    Post 2 and 3 above summarize the situation nicely. There's nothing that needs to be added to the discussion.
     
  7. SatelliteAmps

    SatelliteAmps Member

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    There is a tiny bit to add, you can run a 6v rectifier tube (EZ81, EZ80 are both 6 volt rectifiers), and possibly not need an extra 5v filament transformer. Depends on the amp really.

    To do this is not hard, I have done it numerous times, with and without extra transformers. A lot depends on what the amp in question is, and how much extra oomph the original power transformer has. Assuming it has enough, it is a simple wiring job. There are tonal benefits to a tube rectifier. Mostly depends on whether you want to punch wholes in your chassis, to see if it will make much of a difference.

    One other issue is that a 5AR4 won't be a huge difference compared to most current production rectifiers. But some other tubes will. 5AR4 would require a filament transformer, but would also work for 5Y3, 5V4, 5U4, etc.
     

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