1. zzmoore

    zzmoore Member

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    Every time I see another solid state rectifier I just kind of shake my head. A lot of time and money is spent on bigger and better, caps, transformers, tubes, resistors, and even power cords For Pete Sake. But what about diodes? They always seem like the smallest, cheapest, crappiest, pieces of junk on the turret board. But are they? Are there better ones to be had? A diode upgrade so to speak.
    What do you guys say? Is there better sound and touch available by trying some different diodes?
    Thank You
     
  2. Chrome Dinette

    Chrome Dinette Member

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    Diodes are the size they need to be to do their job. You pick them based on the voltage and current requirements of the circuit.

    Having said that, some people like FREDs. Someone else can explain it better than me, but in terms of switching noise, they perform more like a vacuum tube rectifier. This doesn't mean sag and voltage drop, mind you.

    I guess if you want something that looks like it has "mojo," there are selenium rectifiers:
    [​IMG]

    ...just kidding, they contain poison and like to go up in smoke.
     
  3. MjCartney

    MjCartney Neo-Maxi Zoom Dweebie Silver Supporting Member

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    Yeah, but what a tone! I wish someone would build a "Death of a Selenium Rectifier" pedal... ;)
     
  4. donnyjaguar

    donnyjaguar Member

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    With all those cooling fins you just *know* there's gonna be a voltage drop there. ;)
     
  5. Chrome Dinette

    Chrome Dinette Member

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    I fell into the burning rectifier.
    The volts went down and the current climbed higher.
    And it burns, burns, burns,
    The rectifier,
    The rectifier.
     
  6. donnyjaguar

    donnyjaguar Member

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    You should make a song out of that, Chrome. I'm thinking something with a man in black flavor.

    As for the original poster's observation. If you think about it, diodes are probably the most efficient part, next to wire, inside a tube amplifier. Hence, you don't need them to be big. There has been much discussion on using HexFREDs and other high-speed diodes on this board. Do a search and see. I think they are a waste of money myself, but others disagree and I'll accept that.
     
  7. scottl

    scottl Member

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    But would you not use one of the many ultra-fast, soft recovery diodes available in place of the venerable 1n4007? They are mere pennies and offer performance approaching Hex-FREDS. Probably no more $ than bypassing your slow diodes with a .01uf ceramic.

     
  8. rooster

    rooster Member

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    I use UF diodes in all my stuff. I don't know if I can really hear a difference, but when you buy 1000 of them, they don't cost any more than the 1n4007, so I don't see a downside.

    rooster.
     
  9. scottl

    scottl Member

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    Exactly. :AOK

     
  10. pfrischmann

    pfrischmann Member

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    I've had FREDS in a Marshall for a while. I do not hear much of a difference but the little I do hear, I do not like. They sould too HIFI for a '68 1959 circuit. IMHO.
     
  11. donnyjaguar

    donnyjaguar Member

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    I mentioned on this board in the past that I did some tests with ultra-fast diodes. At 50 & 60Hz they actually didn't work as efficiently as the venerable 1N4007. You could see it on the 'scope face with the reduced area under the curve. I don't recall the exact type of diode, but it was one we used in a high-speed (150kHz) switcher, where it worked perfectly. Didn't take it any further, but was an interesting test nonetheless. If you have a digital 'scope you can take snapshots and compare. It has to be done under load, of course.
     
  12. slorinczi

    slorinczi Member

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    May 6, 2007
    I'm rebuilding a late-model SF Super Reverb. New electrolytics and some other parts, plus a general going-over, but there's still a little bit of hiss in the thing. So that leads me to two questions:

    -I'm told diodes can be "noisy." Is it standard practice to change out original diodes as one would, say, power supply resistors?

    -The diodes in this amp are bypassed with ceramic .002s (see bottom of the schemo). Is that for recovery speed? Noise? Can anyone tell me exactly what they're doing and if I need them?

    Thanks much,
    Seth

    [​IMG]
     

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