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Thread: Electric Ukulele Hum - definitive, technical answer sought (Risa electric ukes)

  1. #11
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    The major difference between battery and AC power is that batteries will give you a pure DC voltage while AC power has a 60hz component that is filtered out by the power supply in the amplifier. When I say filtered out, know that there is always some small amount of the 60hz, that cannot be filtered out, which is the source of the hum you here in some setups. It would appear that your RISA is more susceptible to this 60hz than your other instruments. So it follows that something is different electrically in the RISA. Perhaps a different pickup? Or if it has the same pickup as your other instruments, different wiring. One thing to check is if the hum changes volume when you touch the RISA.
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  2. #12
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    Quote Originally Posted by kissing View Post
    Do you use your Microcube with battery or mains power?
    Always used on mains.
    Trying to do justice to various musical instruments.

  3. #13

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    Quote Originally Posted by kkimura View Post
    The major difference between battery and AC power is that batteries will give you a pure DC voltage while AC power has a 60hz component that is filtered out by the power supply in the amplifier. When I say filtered out, know that there is always some small amount of the 60hz, that cannot be filtered out, which is the source of the hum you here in some setups. It would appear that your RISA is more susceptible to this 60hz than your other instruments. So it follows that something is different electrically in the RISA. Perhaps a different pickup? Or if it has the same pickup as your other instruments, different wiring. One thing to check is if the hum changes volume when you touch the RISA.
    Thanks for this. I didn't know that batteries = DC and mains = AC, and that this is the distinguishing factor.
    With the Risa, the Hum does silence up if I touch the metal parts near the jack, either the metal housing or the metallic joint of the cable.

    Quote Originally Posted by Bill1
    In answer to the question of whether it can be fixed. The electronics in the Risa are simple, the hum is 50Hz from mains power leaking into the circuit and getting amplified. You seem to have eliminated that it could be a problem with the amp or the chord, which means it is likely to be in the simple circuit in the Risa. Which should be fixable. It could be a bad solder joint or a faulty component. Both of which can be fixed by a competent technician.
    It is probably too late for a warranty claim, but Risa may still provide some support by answering communications with a repair person. Support in the form of a circuit diagram will help the repair process.
    Tricky faults in electronic equipment can take a few manhours to pin down and rectify with quality joints and good components, so I suggest you get a quote before proceeding with a repair process. It may turn out to be cheaper to buy a new Risa stick given that Australian technicians can charge $60 - $100 per hour on top of the cost of components. It seems that you can get a new one from Europe for around AU$500, which is about how much some companies want for 1/2 days work from a competent technician. (Its not what the technician gets paid).
    If you can use a solder iron yourself, you could try touching up all the solder joints on the Risa and see if you get rid of a loose joint. Some other component testing is also not hard if you can use a multi-meter. You might find some YouTube videos on testing solder joints and components like capacitors and pick-ups. Some multi-meters have built in component testers and they are not expensive.
    I'm not sure, at this stage whether it's actually a "faulty" Risa, or whether it is inherent in its design.
    I have had a handful of Risa uke-sticks in the last decade or so (from back n forth UAS, sell, buy cycles) and they always had this issue.
    I vaguely remember contacting the company about it when I first realised - and was basically told that's just how they are.

    *edit* found the email from back in 2009:

    Quote Originally Posted by Email from RISA in 2009
    Hi,

    all piezo pickups have a little background noise, because Nylon strung
    instruments can not be grounded through the strings, as it is done for
    electric guitars.
    And he's sort of right. I have a handful of other passive piezo pickup instruments, and they have a bit of hum. However, the issue for me is the degree. I can tolerate the small hum on the other instruments as it feels nearly non-existent. But the Risa gives a very prominent and noticeable hum at any level relative to the other instruments.

    For years, I've tolerated it by simply using my small battery amps disconnected to mains. But I've recently acquired a bigger amp, and my ears have become accustomed to the superior tone and headroom a larger amp offers - and it's a shame I can't really enjoy it with the Risa due to the hum issue.


    Quote Originally Posted by Croaky Keith
    Always used on mains.
    Then you are very fortunate
    I've owned 5 or more Risa sticks in the past decade and always had hum on many different amps, including the Microcube, when connected to mains power.

    I live in Australia, if that means anything in terms of the kind of electricity we get in our homes vs. other countries.
    All my amps are bought locally and designed to use the current available in my location.
    Last edited by kissing; 09-28-2018 at 04:57 AM.

  4. #14

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    Quote Originally Posted by bacchettadavid View Post
    Have you tried grounding yourself using one of those anti-static belts or wrist straps?
    This is an option I haven't ventured yet which I will look into.
    However, I'm not particularly fond of the idea of getting a separate device/gadget that I'll need to wear specifically just for this instrument - which may or may not help.

    I am hoping for a solution that will just fix the issue, allowing me to plug and play without excessive hum, rather than having to wear an additional piece of equipment every time I want to play.

    Thanks

  5. #15
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    With the sound diminishing when you touch a metal part of the jack socket or another part of metal it leads me to believe that you have an open ground between the metal items on the instrument itself, this can be a common occurrence with electric guitars when the pickups, bridge, pots and the jack socket are not grounded to each other.

  6. #16
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    Is the electronics cavity shielded? If not, that might be a good place to start. It would give you something to ground to, at least. That might be enough to fix the problem.

    In my experience with a soldering iron, even a well-wired electric guitar (I recently built two lap steels) should be relatively quiet without touching to strings to complete the ground. If you have to touch something to make the hum shut up, something is probably wrong and can be fixed (or you're standing next to something that causes major electrical interference - I found the washing machine to be a problem).

    You'd do well to watch a couple videos on how to solder and buy the tools for $30-40. Good skills that will take you much further than your RISA. Take notes, then disassemble the whole thing and resolder. If that doesn't work, I might try and find a circuit diagram on the Seymour Duncan site to follow: https://www.seymourduncan.com/wiring-diagrams. Starting from scratch is what I'd do if I knew this was an ongoing problem with the model.
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  7. #17
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    I think this is what you need - a Faraday suit.
    Faraday Suit.jpg

    I'm glad you posted this about the Risa. That will keep it from being added to my mental "want" list.
    Too many ukes, but I can't stop buying!

  8. #18
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    Quote Originally Posted by Spicysteve View Post
    With the sound diminishing when you touch a metal part of the jack socket or another part of metal it leads me to believe that you have an open ground between the metal items on the instrument itself, this can be a common occurrence with electric guitars when the pickups, bridge, pots and the jack socket are not grounded to each other.
    This is headed in the right direction if not the actual answer to the RISA humming on AC mains phenomenon. All of the metal parts need to be electrically attached to each other and to the ground wire of the jack properly to prevent the residual 60hz, or in the case of Australia 50hz, from the amplifier's power supply out of the audio circuit. Sometimes a manufacturer will rely on mechanical connections like star washers or just nuts and bolts to do the ground connections. That can work as long as the mating parts are clean and tight. Properly soldered ground connections are better electrically and more durable over time.
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  9. #19
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    Is there a Risa owners board or site that may have discussed this problem?

    Or the seller may know of a repair shop familiar to the problem and can advise.

    If the instrument was designed for 60 Hz, and the OZ electrical is 50 Hz, would this make it more susceptible to the hum? (I obviously am not an electronics expert.)

  10. #20
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    As Hippie Guy and others said, and to add my 2 cents...

    Magnetic pickups are susceptible to both ground loops if not soldered well and also if the body cavity with the electronics and the cavity with the pickups are not shielded with foil tape.

    I would verify the solder joints, yes ALL of them are to have good integrity, as well as if the body cavities for both the electronics and the pickups are shielded with foil tape. the foil tape also needs to be grounded to the either the metal of the bridge or the earth of the output jack...

    Also, magnetic pickups are highly susceptible to both RF and EMI interference, for after all they are huge inductors that act as an antenna. You can move away from things like the heater, A/C unit and refrigerator, all of which give off RF/EMI as well as pollute your mains with rogue electrical noise.

    A ground lift is the best way to resolve most of this. If the sound goes away when the amps is on battery but is present when on the mains, then by process of elimination, this means that something via interacting with the mains power is the root cause of most of the problem.

    All of the above comes from my own performing over the years, as well as long conversations with Booli while getting tech support from him. I am not as technical as he is, but these are the things he has told me, that have helped me when I had similar issues to you Kissing. Not always the same answer to each problem, but usually some combination.

    Also, lots of inferior piezo pickups need proper shielding as well, otherwise you get the buzzing or humming from either the RF and EMI and possibly also the ground loops.

    You asked for help here Kissing, and say you tried it all already, yet the problem is still there, so maybe there are options with various combinations that you have not yet tried?

    Think about it.

    I tried to get in touch with Booli to ask him to chime in here, I sent him a text message with no reply as of yet and when I called him I kept getting his voicemail the past few days (he lives near me and we have jammed together as well a few times). I know he is dealing with some family issues and does not have lots of free time lately. If he sees this thread, maybe he can offer some advice later on.

    Kissing, I hope you can figure it out. The humming is really annoying to me as well when it happens.
    -Joe......Have uke, will travel...

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