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Thread: How would i isolate this?

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    Old Timer daz's Avatar
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    How would i isolate this?

    I have a tuner that has a bypassed output so that when you tune it mutes the output. I have the tuner and a boost pedal sharing the same wall wart and it works fine until i tune at which point i get this digital noise hitting the amp as i tune and if i unplug the only other pedal it stops. So how would i isolate it short of using 2 power supplies? The sound is fine when playing so the issue is only when tuning with the output muted. It's not a huge deal but it is really annoying so if i can isolate it with a cap or whatever that would be nice. Thanks.

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    Supporting Member mozz's Avatar
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    Maybe a .1 or .01uf cap across the power supply jack on one or both of the pedals. Other than that, maybe a better power supply?

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    Old Timer daz's Avatar
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    Quote Originally Posted by mozz View Post
    Maybe a .1 or .01uf cap across the power supply jack on one or both of the pedals. Other than that, maybe a better power supply?
    Nope, no worky.

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    Supporting Member mozz's Avatar
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    Have you tired one of those pwr jack to 9v battery clip things? That would eliminate the power supply as the cause. It's not truly muting the output if something is going through. See what kind of switch or switching the tuner pedal is using.

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    Supporting Member Jazz P Bass's Avatar
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    Which power supply are you using.

    It sounds like an SMPS.

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    Old Timer daz's Avatar
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    Quote Originally Posted by mozz View Post
    Have you tired one of those pwr jack to 9v battery clip things? That would eliminate the power supply as the cause. It's not truly muting the output if something is going through. See what kind of switch or switching the tuner pedal is using.
    Thats what i'm using, the battery clip. The power jack was unusable on the board due to space. But it;s not outputting sound, it's digital noise thats apparently getting into the signal path thru the power rail.

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    Old Timer daz's Avatar
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    Quote Originally Posted by Jazz P Bass View Post
    Which power supply are you using.

    It sounds like an SMPS.
    It's a 9v wall wart from some sort of tascam device. I think one of those CD/trainer devices that you play along with CD's with headphones. I suppose i may have a boss adaptr around here somewhere i could try.

    EDIT: it's not the supply. I tried a battery and same thing. But as i said, if i unplug the boost pedal it gets quiet. And the boost pedal is tru bypass so the signal path remains intact with the power source removed.
    I also tried unhooking the negative button on the 9v clip to allow the signal path ground to to the job and eliminate a possible ground loop.

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    Last edited by daz; 04-01-2018 at 10:29 PM.

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    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by daz View Post
    I have a tuner that has a bypassed output so that when you tune it mutes the output. I have the tuner and a boost pedal sharing the same wall wart and it works fine until i tune at which point i get this digital noise hitting the amp as i tune and if i unplug the only other pedal it stops. So how would i isolate it short of using 2 power supplies? The sound is fine when playing so the issue is only when tuning with the output muted. It's not a huge deal but it is really annoying so if i can isolate it with a cap or whatever that would be nice. Thanks.
    I smell itīs not a power supply issue at all.

    I have verified that symptom many times and, at least in my case, the problem was that the tuner mutes by *opening* its output , instead of shorting it to ground.

    So next pedal or amp now has an unterminated input jack and cable: Hiss/Hum/Buzz City.
    Which will sound digital if going through a digital pedal.

    Basically same as if you unplugged your guitar cable from Guitar end.

    Clearly an oversight by Tuner manufacturers.
    Of course it works fine ... in a Lab that is, but not in a real World situation.

    Just to check this, donīt trust me, build/mod a guitar cable so you can short Hot to Ground ... I highly suspect noise will disappear or be highly attenuated.

    IF so, *maybe* there is some voltage which changes inside the Tuner to open its output, (measure switch pins) if so you might amplify/invert it as needed and use it to *besides* mute the tuner out by shorting across it (with a FET or even a Bipolar transistor if pressed).

    Or the switch itself might have an unused section you could use by shorting output to ground.

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    Juan Manuel Fahey

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    Old Timer daz's Avatar
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    It's not loud at all like unplugging the cable. Theres zero noise at all till you pluck a string, then it;s not loud and it's not a buzz but a very low hum. The thing that makes me say it's a PSU noise getting into the signal path is that if i unplug the boost pedal's PSU plug it;s dead quiet as i tune even tho the signal path remains. The boost is true bypass. or not exactly true bypass bt i forgot what it;s called, but it works the same becaue you can unplug the power and as long as the switch is in the off position the signal flows thru it.

    Quote Originally Posted by J M Fahey View Post
    I smell itīs not a power supply issue at all.

    I have verified that symptom many times and, at least in my case, the problem was that the tuner mutes by *opening* its output , instead of shorting it to ground.

    So next pedal or amp now has an unterminated input jack and cable: Hiss/Hum/Buzz City.
    Which will sound digital if going through a digital pedal.

    Basically same as if you unplugged your guitar cable from Guitar end.

    Clearly an oversight by Tuner manufacturers.
    Of course it works fine ... in a Lab that is, but not in a real World situation.

    Just to check this, donīt trust me, build/mod a guitar cable so you can short Hot to Ground ... I highly suspect noise will disappear or be highly attenuated.

    IF so, *maybe* there is some voltage which changes inside the Tuner to open its output, (measure switch pins) if so you might amplify/invert it as needed and use it to *besides* mute the tuner out by shorting across it (with a FET or even a Bipolar transistor if pressed).

    Or the switch itself might have an unused section you could use by shorting output to ground.

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  10. #10
    Supporting Member Jazz P Bass's Avatar
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    So what brand tuner do you have?

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    Old Timer olddawg's Avatar
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    First thing I would do is try some different cables connecting the pedals. It could be a resistive ground issue. If you made your own cables and it does turn out to be a hanging input when switched, you might try unscrewing the plug casing and solder a tiny 1m resistor from tip to sleeve. I have a TU2 Tuner (in a similar if not the same configuration) and OneSpot powering it and most of my pedal board without any digital noise at all. Btw.

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  12. #12
    Old Timer daz's Avatar
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    Quote Originally Posted by olddawg View Post
    First thing I would do is try some different cables connecting the pedals. It could be a resistive ground issue. If you made your own cables and it does turn out to be a hanging input when switched, you might try unscrewing the plug casing and solder a tiny 1m resistor from tip to sleeve. I have a TU2 Tuner (in a similar if not the same configuration) and OneSpot powering it and most of my pedal board without any digital noise at all. Btw.
    It's not the cables. And let me clarify that it does NOT make any noise when off. Only when tuning and in bypass mode that mutes the output. And the noise is also not there till i hit a string at which point its a random on and off sound thats like a digital clock randomly firing or some such thing

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  13. #13
    Old Timer daz's Avatar
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    Ok, it's done. I found the power wires i used were causing it. They were excessively long and routed the long way around to keep the board clean. I found moving it further from the signal cables eliminated the noise so i shortened it and routed it as short as possible further away from the cables.

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