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Add diode clipping?

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  • #16
    Max

    Ray, would that work for clipping in a non tube pedal? As back to back diodes do?
    The "non-tube" category is pretty large, and I'd have to be a lot fresher than I am now to figure out the differences in behavior between NPN/PNP/enh. MOSFET/dep. MOSFET/P-JFET/N-JFET/etc. My gut feeling tells me it won't work exactly the same in any of them, but I could be wrong.

    And in tube environement, would back to back diodes above a zener do anything intresting?
    Yes, they sure would - the grid would diode-clip between roughly 1.2V positive, and approximately the Zener voltage in the negative direction. The diode above the Zener isolates it from the grid during the positive signal swing; back-to-back diodes would remove this isolation.

    By the way, your atachement above doesn't seem to work!
    I don't know what to tell you - I uploaded it fresh from my hard drive to the 'Manage Attachments' section just liked I did before, then cut & pasted the shortcut using the 'Insert Image' button just like I did before, and it displays properly on my screen in both the text body and thumbnail footer, just like before - I'm looking at it right now, as I type. There's not even a thumbnail?

    Ray

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    • #17
      You can't see attachments unless you're logged in dudes
      "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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      • #18
        Steve,

        I think something's wrong, though - the pic's gone now, the thumbnails won't open, and the link is invalid. I'll try posting it again.

        Ray
        Attached Files

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        • #19
          Here goes nothing...

          Lonzo,

          If at first you don't succeed...



          It looks fine here, which means nothing, I guess.

          Here's the picture link:

          http://music-electronics-forum.com/a...1&d=1157030357

          Ray

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          • #20
            The new board software seems to automatically log you out after a while too.
            "Enzo, I see that you replied parasitic oscillations. Is that a hypothesis? Or is that your amazing metal band I should check out?"

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            • #21
              Regarding the smoothing effect, that's exactly what I would expect (so I was surprised everyone else expected otherwise). Example: Fuzz into clean amp...harsh; Fuzz into overdrive pedal (diode clipping)...smooth.

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              • #22
                Matt,

                IMO the key word is "fuzz" - smoothness gained at the expense of a fuzzy tone is a Pyrrhic victory, at least in my book - but YMMV, and FWIW I have heard diode-clipping circuits I thought sounded OK.

                Ray

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                • #23
                  Zener Value

                  The only Zener I could find (on short notice) has a volt rating of 12 volts & 1watt.

                  Will this work?

                  Thanks,
                  'zo

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                  • #24
                    Lonzo,

                    The only Zener I could find (on short notice) has a volt rating of 12 volts & 1 watt. Will this work?
                    Probably not - but try it and see.

                    Ray

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                    • #25
                      Another option along similar lines as Enzo mentioned is to parallel up a series string of diodes. This will give you more signal swing before they clip. Two diodes gives you 1.2 volts before clipping, 3 gives you 1.8v, etc. Then add a small value ceramic cap across the whole wad to take the hard edges off the signal when the diodes clip.

                      -Carl

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                      • #26
                        diode clipping experiments

                        I have tried clipping circuits with tube amps, You can use what KOC calls compliance to get around the more harsh clipping and massive signal
                        loss of diodes strapped to ground, I think the last time I tried about 82k in series
                        with the clippers to ground this resistor value you can vary to taste for more
                        or less clipping and signal.. basically it helps dump less signal to ground ans softens the effect

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                        • #27
                          Thanks Everyone!

                          Thanks everyone for all the suggestions and advice.

                          I tried the Zener diode ckt Ray detailed but found that my 1W 12V Zener must not be effective. Another experiment found a quad of parallel (reverse polarity) diodes from the cathode to ground. This effort was to no avail as well.

                          I think I'll go with a 12AT7 in the phase inverter spot and sub 12A_ into the first gain stage; probably should have started here first....

                          Again, thanks for all the advice. I really expected to get flamed for such a strange request.

                          lonzo

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