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Thread: 5E3 Negative Feedback Loop

  1. #1
    Supporting Member AppleScrappler's Avatar
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    5E3 Negative Feedback Loop

    I just implemented the negative feedback loop mod on my 5e3. It squealed like a newborn kitten so I switched the OT primaries on the power tubes and that problem went away. I used a DPDT switch that, when set in the "on" position, removes the cathode bypass capacitor from stage 1 of V2 and at the same time connects a 56k resistor from the hot lead of the OT on the speaker jack to pin 3 on V2. when the switch is off it goes back to stock 5e3. From my understanding of most comments I've read about doing this mod it usually makes the amp a little quieter but with more headroom. when I flip the switch to the "on" position the amp noticeably gets louder (I leave a guitar with single coils plugged in and position it to get a nice hum for the initial testing purposes. who said that stupid hum wasn't useful?!... i tested playing the guitar too but only a little being that I'm in a hotel at the moment between moves and can't crank the amp). It doesn't get a LOT louder - but certainly isn't the same.
    Is it normal for it to boost the volume a little? I've tested it with the volume set at different places and get the same result. Could this just be the effect of the headroom increase relieving some compression? or does this sound totally foreign to those who've done the mod and are familiar with its normal response?

    This conversation kind of started in another thread I had titled "5e3 build - fuse keeps blowing" but that thread moved off topic so I'm starting this in a new thread to help those who search the forum in the future.

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    Two roads diverged in a wood, and I--/ I took the one MOST traveled by, / And that has kept me away from the freaks.

    http://www.xkcd.com/730

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    Supporting Member AppleScrappler's Avatar
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    OK never mind I fixed it. I had the switch wired "wrong." I had wired it according to where it said its contacts were made (just like any other DPDT switch). wellllllll after hours of troubleshooting I finally got fed up and decided to quickly disassemble the switch and take a look inside (sure I could have done continuity tests on the lugs to solve this - but I was mad and felt like ripping something apart). turns out the contacts were made the opposite of what was diagrammed. So thank you again Radio Shack for wasting my time... can't we band together and open a chain of GOOD electronics stores all over the world that sell components for us nerds? I don't like waiting for stuff in the mail!

    I now have the feedback loop wired and working as described in the first post. Thus ends another saga...

    0 Not allowed! Not allowed!
    Two roads diverged in a wood, and I--/ I took the one MOST traveled by, / And that has kept me away from the freaks.

    http://www.xkcd.com/730

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    [QUOTE=AppleScrappler;197099] can't we band together and open a chain of GOOD electronics stores all over the world that sell components for us nerds? I don't like waiting for stuff in the mail! QUOTE]

    Amen to that brother I mean if we actually put our minds to it its not impossible . I had my debit card number stolen from my excessive vacuum tube shopping sprees. Plus im now addicted to ebay looking for the next best thing and all the "deals". Its funny half the people in the world could care less about tubes yet somehow the price of them all seems to inflate like a hot air balloon lol. Im serious tho you ever get a burr in your ass you contact me and we will make a chain of electronics stores a tube junky can be proud of!!!!!!!!!!!!!


    nate dog red fox

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