Work around Hum Problem by plugging USB cable into my (grounded) laptop



  • Re: Hum Problem and Power Supply Specs

    I have the same problem.

    I got rid of the hum by plugging the USB cable into my laptop (which is grounded) and the humming disappears.



  • Doesn't that route the volume through the computer??



  • @cmcwillieb only if the computer is turned on. People have reported that just making the connection solves the hum problem. My amp is on its way (finally) but I've already purchased a grounded power supply so I'll be able to start using it as soon as it arrives without having to use the USB connection. I also purchased a battery pack which is most likely the way I'll be powering it most of the time, so there won't be a grounding issue at all.



  • @dhbailey DH, Please post information on the battery pack. Sounds like a great idea.



  • @cmcwillieb Here's the link:
    https://smile.amazon.com/gp/product/B00DN0KBXU/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1
    The product is:
    POWERADD Pilot Pro 32000mAh Power Bank Dual USB Port 4.5A (9V-20V DC Output) with Digital LCD Display for Smartphones, Tablets, Pocket PC, Notebook, Chromebook, Macbook and More

    That cost $110 when I ordered it a couple of weeks ago -- there is a less expensive version with only 28000mAh capacity which had been on sale for $80. I can see this being a great asset when camping or wanting to play outdoors not near an outlet, as well as solving any grounding issues.

    The 32000mAh translates to 32 amp-hours. Since the Spark only draws 2.4 amps, that means just over 13 hours of playing time between charges. The person in the Spark Amp Owners Club at Facebook who originally posted about this unit bought the 28000mAh version and said she had used it with the Spark amp for a few hours and it was only down 25%.

    If this does what I think it will do I'm going to see how it might work attached to the amp itself (velcro probably) to make it a single easy to carry around unit. I don't have the amp yet, but it's supposed to be here Tuesday so I'll be able to report more in the middle of next week.

    There are other units which people have posted about in the facebook group, units which the AC adapter would plug into for the spark. But this PowerAdd unit outputs the DC directly into the amp so there's no need to use the power adapter at all. I've tested it on my HP notebook computer and that started charging right away. Very cool!



  • @cmcwillieb In addition to what @dhbailey said, you can do it with the computer off, so long as the computer is plugged-in and is itself properly grounded. Plugging into my Dell laptop kills the hum, whether on or off. But plugging into my 2011 MacBook Air doesn't do anything, whether on or off -- but I had replaced the power adapter a year or so ago with one I found on Amazon (not official Apple), so I'm guessing it isn't properly grounded, even with a three-prong plug.

    But even if your computer is turned on, it does not reroute the audio. You still have your guitar audio playing locally through the Spark's speakers or headphones. The Spark's USB output is in addition to the Spark's local output (speakers/headphones), and the Spark itself effectively becomes a monitor.



  • @dhbailey That's an interesting product. I've always been big proponent of using rechargeable batteries for my physical equipment, rather than dealing with expensive AC power units and 50/60Hz hum in general (plus, it makes things portable, without having to play near an outlet). Granted, my playing-in-band days are over, and now only play at home as a hobby, so this is easier to pull-off than being on-stage with a pedal board with a dozen pedals...

    For instance, I have a BOSS GT-1 and BOSS Katana Mini, both of which can run off AA batteries -- so I have a dozen rechargeable AA batteries that I cycle through. I also have a set of four rechargeable 9V batteries for pedals, and simply use external DC/battery adapters for pedals that don't support batteries.

    But I didn't think of a battery solution for the Spark. I already ordered a replacement AC power adapter that should be properly grounded, for US$15 on Amazon. It's out for delivery as I write this, so we'll see later today.

    EDIT: And just two minutes after posting this, my package is delivered, and this model did get rid of the AC power hum.



  • I had the humming issue too - power supply only had 2 prongs. When I complained to CS they sent out a new power supply with 3 prongs - this sorted the hum. I waited 4 months for the amp and 3 weeks for the new power supply. It's working fine now thankfully. I hope Postive Grid improve their QA for next hardware release.



  • @leejayd Yeah -- I was going to complain to support, but read stories on the hoops people had to jump through, and then even when they finally got the "new" adapter, it was the same power adapter as before. I already have another ticket on another issue opened three days ago with no reply, so I didn't feel like another ticket, and having it take a month to get the replacement that may or may not be the same thing. If buying a replacement were over $20, I wouldn't have bought it -- but since I found a replacement for $15, I decided to just do it.

    In addition to grounding issues, the included power adapter doesn't even have ferrite core rings. Does the replacement adapter they sent have ferrite core rings?



  • @blueingreen I also ordered a replacement power supply almost immediately after ordering the Spark. Not that big an investment and this way when my Spark finally arrives (supposedly this coming Tuesday) I know I'll be able to use right off the bat, even if the PG power supply has that hum problem. Then I'll request a replacement power supply and won't have to wait for it to come. I'll end up with two, which is fine with me.



  • Just tested this on the iPad as well and it works. The humming returns immediate after I unplug the charger.