Fixed: hardware solution for humming problem



  • Hi there,

    after opening the case I found a place on the back to add a grounding-screw. I drilled a hole installed the screw and - after putting things together again - I connect a short piece of wire to a crimp connector to an electrical ground. It instantly killed any hum so that I could revert the restrictive noise gate settings.

    If you want to do it: Be careful to blow away any of the small metal metal particles which might fall on the electrical board when drilling the hole. 0_1591601043838_IMG_20200606_200047.jpg



  • @ksmichel Wouldn't ir be easier just to buy a properly grounded adapter? Most of users experiencing the same (damn) issue have solve it by buying a laptop type power supply (19V 2.5 Amp)



  • You're probably right. But I didn't have a calibre-tool to know the exact needs for the pins. And I didn't like the idea to buy a new power supply, when only a ground is needed.



  • @ksmichel what did you attach the other end of the ground wire to? I can see it screwed onto the back of the amp but not what you connected it to. Thanks.



  • but a "tampering" could void the warranty ..



  • I only need to connect the wire to a ground level. For testing I used the gound pole of my mains socket (attention!). For a more stable But you can also connect it to the copper / sheer metal pipe of e.g. a central heating. You can also try to find other ground levels e.g. the sleeve of a connected notebook.

    As you can see a plugged-in Charging device is preventing my ground cable from accidentally touching any dangerous mains leads. If you want to further fool proof that, you can also use a proper plug an install only the ground wire and fully leve out the metal plugs for mains-power. #sigh: @spark: It would have been so easy to use a proper power supply.

    0_1591619022301_IMG_20200608_142235.jpg



  • @ksmichel Thank you for the clarification and the picture. I'll wait and see what power supply ships with my Spark, but I've already got a computer power supply in my wish list at Amazon.



  • @dhbailey hello Michel, which power supply did you pick for your wish list on Amazon, can you post the link? I want to buy one as well... Thank you



  • Sounds like this amp was rushed to production if we have to drill holes in a new amp or rig it with jumper wires careful not to touch the mains to eliminate humming from it.



  • @johnny said in Fixed: hardware solution for humming problem:

    Sounds like this amp was rushed to production if we have to drill holes in a new amp or rig it with jumper wires careful not to touch the mains to eliminate humming from it.

    yea... PG!!!
    sort it out... how can you have people opening their units to rectify a problem PG should've easily factored in R&D?
    I wonder if anyone is going to make a mistake with this method and electrocute themselves or a family member.
    Besides voiding their warranty.
    lol... what next?



  • Hi everybody,
    well OK. I admit: It IS not a method suitable for everybody. I am used to things like that as a radio amateur. I had solved a grounding problem years ago before with a small pa for a radio. But, in fact, it is not really difficult at all. For me it was the solution with the lowest possible footprint. Better to send the unit away to the USA, wait for months and not really sure that they can solve this. I decided to do it myself when I realized that simply by touching a metal part of the spark with my (grounded) body cured the disease. So you don't really have to go into the electrical "innards" of the spark - the only thing to do is to establish a stable ground connection. And luckily enough there is plenty of space to install a screw for that purpose.

    Power Supply: I didn't expect a new Power Supply to solve that problem as the mostly used power supply with only two connector-pins don't have a ground connection. So switching to another power supply would imho only be needed if the power supply itself produces ripples. That was not the case - I found that my positive-grid-power-supply (a chinese Moso switching power Adaptor) was ok and within normal parameters. There was no need to change it and I kept it. The hum comes from different potentials of the Spark-GND-potential and the GND-potential in the wiring of the electrical installation of the house. Thats why some of us don't have that problem - as they are lucky to not have different electric potentials.



  • @pontesilli70 I just removed the one I had put into my wish list. The one I originally placed there was only $24US but it had only a two-prong plug. I just realized that if the problem with the hum is caused by the unit being ungrounded then I should buy a unit with a 3-prong plug. Most of the computer power supplies with replaceable tips to fit various computers have only 2--prong plugs, while many of the ones for a few specific models of computers have 3-prong plugs. I thought I had found one that would be good but reading the reviews I found one which says it's not for delicate audio equipment because there's an AC hum on the DC output side of things.

    So now I don't have any in my wish list and I'm hoping that my Spark shows up with one of the newer power supplies I've read that some people apparently have been receiving with their amps which are properly grounded. I hope that someone who owns the amp and has purchased a replacement power supply will post what they've bought that worked.

    One thing I haven't seen anybody mention is whether they have tried reversing the plug in the outlet (if possible) or reversing where the AC power cord plugs into the power supply. I know that used to do the trick quite often on older guitar amps to get rid of ground-loop problems.



  • HI I am in the UK and have been having the same grounding issue. I have sent a ticket into Positive Grid and they got back to me within 4 days, they are going to send me a new power supply which will be arriving next week, I replied to them asking if it would be a two pin adaptor or three as I believe this is where the problem lies, they have got back to me and said it is a two pin, so I don't think this will cure the problem but I will try it and let you know. Any amp I have used in the UK always has a three pin Adaptor. I have a VOX cambridge 50 that I brought as I got sick of waiting for the spark to arrive, this has a three pin adaptor and there is no grounding issues with this amp, unfortunately it has a different connection at the amp end so I can't try this in the spark.



  • Anyone know what the spec is of the dc connector? I'm pretty sure it's 5.5mm but it's the inner diameter that caught me on something before. Anyone know?



  • @clive-hawnt it is also a female connection there is no pin in the middle



  • @caj951 Sorry not correct. Its not female, it plugs into the dc socket on the back of the amp, it is male. And DC connectors come in different internal hole sizes, 1.7mm, 2.1mm and 2.5. So some DC connectors wont go into the Spark amp socket. So I was asking if anyone knows what the INTERNAL diameter is. Examples below.

    0_1591701202095_CleanShot 2020-06-09 at 12.12.09@2x.png



  • Since 2 weeks i use this one, from a Fujitsu Laptop and the big hum has gone.
    You need a grounded power supply with the Schuko-Plug, not
    the Euro-Plug. It must be the big round one not the flat.
    On the other end it must be outside 5,5mm and inside it must have 2,5mm.
    And have attention, that there is no pin in the middle.

    0_1591702034564_IMG_0561.JPG



  • @de_cunny Thank you for being so specific -- it's great to know the dimensions of the plug that goes into the amp. That makes it a lot easier to find a replacement power supply if needed.



  • @clive-hawnt sorry maybe the wrong term to use some connectors have a pin in the middle some don't, the one on the spark has the pin on the connection on the amp, have a look the DC in socket, the connection from the power supply has no pin in the middle. This is the other way round on some power supply's so you have to be careful what you may connect, you could bend the pin if you fit the wrong power supply. The connection on my Vox amp is the complete opposite to the spark.



  • @de_cunny thanks for this info have found a similar power supply on Amazon, I will compare it to the replacement Positive Grid are sending out