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Thread: deluxe reverb amp with extra gain stage on chanel 1 to make it more like channel 2

  1. #36
    Bent Member Chuck H's Avatar
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    Quote Originally Posted by loudthud View Post
    3K is a standard value for 5% parts as is 750. Fender used 10% parts for the most part.
    Yes. Thank you. 3k is available. I was considering what a person might have on hand or what would be easiest to source. When I design I usually go with the standard values for 10% parts in case I ever run across the need for an immediate repair and have to get a resistor at Fry's or something. So that's just my personal bias on the matter.

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    In a single tube stage clipping is never completely symmetrical, rather positive and negative output signal peaks are clipped differently : different mechanisms, different shape, different harmonics produced. Depending on biasing one or the other appears first. Center biasing ensures that positive and negative clipping starts at similar levels.

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    There are examples by many major manufacturers, but the most obvious would be the AC30 using 220k loads and a shared 1.5k cathode resistor for two triodes. Similar to Fender BF amps using 100k loads and a shared 820 ohm cathode resistor. So for a single stage that doesn't share the cathode circuit you'd need a 3k resistor. Not a standard value. 2.7k or 3.3k would work fine. With 2.7k seemingly being the preferred choice with a 220k plate load among designs I've seen. These are also the values used by Fender on some models.
    In many (if not most) cases classic amp manufacturers (especially Leo Fender) just went with the tube manufacturers' recommendations/examples as they can be considered best practice.
    No wonder the chart I posted lists the 100k/1.5k and 220k/2.7k combos.

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  4. #39
    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Helmholtz View Post
    No wonder the chart I posted lists the 100k/1.5k and 220k/2.7k combos.
    Yep. And the "standard value" thing is probably why Vox used a 1.5k resistor for the shared cathode. Because 1.35k isn't a standard value

    2 Not allowed! Not allowed!
    "Never bet your life on somebody else doing their job." SoulFetish's good friend

    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

    "Back to the amp. It makes horrible sounds when I play my guitar thru it... because I suck at playing guitar." Mike6158

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