Solution for hum?



  • I was having hum issues—and picking up radio station interference, when using boosted distortion. It was easy to dial it out by using the noise gate, so I considered it a minor problem. However, I started to notice that that hum was present while using a clean, non-distorted sound—it sounded like a slight distortion, riding above the sound. Even touching the strings (grounding), or turning off all gain, made no difference.

    After checking the specs of the power supply, I replaced it with a laptop brick, with the same voltage, polarity, and a grounding plug (19v @ 6.3 amps).

    The problem went away!

    The sound is VERY clean now, and the fizzle and hum are completely gone, even with the noise gate disabled.

    I am not suggesting others replace their power supply, unless you know what you are doing, and can assume the risk.

    IF the power supply is indeed the problem maybe PG can recommend a replacement supply, and offer a rebate, or product, for our troubles? I know PG will do the right thing, because this amp is amazing and will sell like crazy.

    This post is not meant to cast aspersions on PG, or assume they are a bad company. I have been happy with their other products, with the exception of no midi support, as of yet, in Bias FX 2! I stand corrected...midi is implemented...off to try it out...

    Dave



  • @daveishere

    Many people here have already grappled with PG support and eventually got replacement power adapters with proper grounding sent to them, so PG is well aware. Some of us gave-up and already bought new adapters. I bought this one for US$15, which has proper grounding and a ferrite core ring, and works flawlessly for me. In addition to improper grounding, the Spark's included power supply also has no ferrite core rings, which is why you also get radio (RFI/EMI) interference.

    Keep in mind that there is a workaround for the AC hum with the Spark's included power supply. If you plug the USB cable into the Spark, and the other end into a computer that is properly grounded (even if turned off), then the AC hum goes away. So if you don't mind having the Spark's USB plugged into a computer or something else grounded, then you don't actually need another power adapter, or at least for the grounding issue.



  • @daveishere said in Solution for hum?:

    I was having hum issues—and picking up radio station interference, when using boosted distortion. It was easy to dial it out by using the noise gate, so I considered it a minor problem. However, I started to notice that that hum was present while using a clean, non-distorted sound—it sounded like a slight distortion, riding above the sound. Even touching the strings (grounding), or turning off all gain, made no difference.

    After checking the specs of the power supply, I replaced it with a laptop brick, with the same voltage, polarity, and a grounding plug (19v @ 6.3 amps).

    The problem went away!

    The sound is VERY clean now, and the fizzle and hum are completely gone, even with the noise gate disabled.

    I am not suggesting others replace their power supply, unless you know what you are doing, and can assume the risk.

    IF the power supply is indeed the problem maybe PG can recommend a replacement supply, and offer a rebate, or product, for our troubles? I know PG will do the right thing, because this amp is amazing and will sell like crazy.

    This post is not meant to cast aspersions on PG, or assume they are a bad company. I have been happy with their other products, with the exception of no midi support, as of yet, in Bias FX 2!

    Dave

    I've the same problem, if I use noisegate there is no noise with clean tone but if the strings vibrate it comes back..if I touch metallic parts no made difference...
    I've to try another power supply

    I hope solve the problem



  • @blueingreen said in Solution for hum?:

    I bought this one for US$15, which has proper grounding and a ferrite core ring, and works flawlessly for me. In addition to improper grounding, the Spark's included power supply also has no ferrite core rings, which is why you also get radio (RFI/EMI) interference.
    Keep in mind that there is a workaround for the AC hum with the Spark's included power supply. If you plug the USB cable into the Spark, and the other end into a computer that is properly grounded (even if turned off), then the AC hum goes away. So if you don't mind having the Spark's USB plugged into a computer or something else grounded, then you don't actually need another power adapter, or at least for the grounding issue.

    Thanks for the recommendation.



  • I opened a ticket for this. I had to take a video showing the issue and they basically said that there are lots of environmental reasons why this happens and it's not a flaw, but since we are so good we are going to send you a replacement. Take that how you want, but it's a very well know issue, which doesn't bother me right now since I have the usb connection plugged into the PC. In the video I took I showed touching the USB cable to a grounded screw on a wall outlet and the crazy loud hum going silent, just to prove my point.



  • Could you post the video in the forum, so we can understand the differents problems..



  • @cbrandst

    Yeah -- that's frustrating, because it is a flaw. I've played since '86, and know the differences among the various types of noise:

    • AC hum from poor grounding, shielding, and isolation.
    • Radio interference (RFI) that certain circuitry in devices like pedals can pick-up, and any attached cables can magnify as an antenna.
    • EMI from things like lighting that pickups can, well, "pickup".
    • "Regular" single-coil hum -- I'm a pure Tele/Strat guy, but I'm sure some humbucker players consider this is a "flaw" too! ;-)

    The first two are controllable by the manufacturer. The last two by the end-user. In any case, this is definitely pure AC hum, because AC hum goes away when you touch the guitar strings due to grounding (plus the noise itself is a giveaway, since it is harsher than single coil hum). RFI is obviously identified as a radio signal, not hum. EMI is identified simply by moving and re-positioning the guitar. But the support people have no control over the product design decisions, and it's unfortunate that they have to bare the brunt of them.

    @Daveishere did mention radio interference (RFI). While not completely eliminated, RFI is usually mitigated by ferrite core rings on the power adapter cable, which this adapter also lacks, and thus a flaw. You can get inexpensive clip-on ferrite rings that are specific to cable size. I use them on some guitar patch cables to isolate a couple pedals that I love, since something in their circuitry picks-up local radio stations. Although...there is a benefit to getting the weather report while playing guitar (a bug or a feature?)!



  • @daveishere

    Out of curiosity, did your replacement laptop power adapter have a ferrite ring on the cable (usually a cylindrical blob on the cable)?



  • @blueingreen Noise and hum is one of two problems for me. The other is poor sustain that is uneven with notes suddenly dropping out. Does the upgraded power supply correct that too ?



  • @rexlarsenphoto The two are actually related since the notes dropping out (esp. on the B & high E strings or while playing softly) and poor sustain are generally due to an overly aggressive noise gate. The noise gate is usually set aggressively to cover-up the hum/noise, which is louder than it should be because of the poor grounding and radio interference of the power adapter. If you disable the noise gate, the dropped notes and sustain issues should go away, but you'll then hear the full force of the AC hum (unless the USB cable is plugged into something properly grounded).

    So, if you fix the grounding issue with the power supply, then you have much less hum, which then allows you to manually tune-down the noise gate (or even turn it off), resulting in much less collateral damage to things like sustain soft notes.

    I also own BIAS FX2, and in a follow-up survey they sent after purchase, my only real criticism at the time was the noise gate and noise suppressor, which I think is the weakest part of their software tech lineup, and often sounds unnatural. They also have the tendency to go overboard with noise gates in their presets.



  • @blueingreen Hi. Thank you for the advice. This might sound like a dumb question, but please respond. I bought the adapter you recommended (has not arrived yet). Do I substitute the entirety or just the part of the electric cord? I will still reach out to PG for an official one, but I want to play my amp without the hum



  • @keithconner22 It replaces the entire thing, from AC outlet to the Spark. The two cable parts aren't interchangeable, since they are different.

    I'll eventually contact support for a replacement too, but figured that they are a bit overwhelmed, and will wait for things to calm-down. Plus, it may be easier (fewer hoops to jump through) after more and more people call them on the issue.



  • @blueingreen Thanks a lot for the detailed explanation. The Spark shows a lot of promise. I look forward to eliminating both issues. I appreciate your help. Rex



  • @rexlarsenphoto Yeah -- there are issues, but I'm fairly optimistic. Most issues are fixable. The existing power adapter has a workaround by using USB as ground, and a new power adapter can fix it for good. I bought a new adapter more out of impatience, plus it was relatively inexpensive, but it wasn't really necessary.

    The sound overall is a bit muddy, but I've found that lowering the "Master" on presets a bit helps, along with tweaking the shelving EQ (and putting a boost pedal, like a Tube Screamer in front of it helps clean-up things even more). At the end of the day, it's a practice amp, so I'm not expecting it to sound perfect.

    There are still some stability issues, but it was a pre-release product when I bought it, so I knew what I was getting into. Although, I personally don't think it should be considered pre-release anymore by this fall, since it will then be about a year old, since first being demo'd. But I'm optimistic that things will improve with subsequent firmware updates as the year goes on, and supposedly new sounds and features will be added. All-in-all, it's a pretty cool device for the price.



  • @blueingreen You make good points but I admit I don’t know what shelving EQ is. I find it interesting no YouTube reviewers that I saw mentioned the issues discussed here. Regarding the so-called muddy or dark sounds, it corrects pretty well by cranking treble and turning bass way down. I’m pleased how well the Spark sounds at ultra low volumes. I use a Strat.



  • @rexlarsenphoto Shelving equalizers (EQ) are just the basic Treb/Mid/Bass tone controls -- as opposed to fancier equalizers like graphic equalizers and parametric equalizers. So, I was essentially just saying the same as you -- cranking the the treble and turning the bass down.

    I find that YouTube reviews tend to be overly positive for guitar stuff. A lot of reviewers get products sent to them by the company, so I think there's some pressure to not offend the company and get cut-off from future products. In any case, I like to follow this guy, who had a good review of the Spark, but he did briefly mention the bass-heavy aspect:
    https://www.youtube.com/watch?v=eWQZJ7k49ok



  • Inquired about a new power adapter which I requested a couple of weeks ago and never got response and did get response today saying there are out of them but rest assured I am on the list and they will send me one when they get some more. Hmmmm heard this before, wonder how long now.



  • I submitted a ticket, then followed up a week later and got the same response; I'm on the list but rest assured.... PG assurances don't really comfort me, especially since I still don't have the bag I paid for.
    While I wait, relatively patiently, for the Power Supply promised by Positive Grid I went ahead and picked up the one identified in a thread here in the forum. OH MY GOD (or whatever higher power you identify with (or not), you get the point), what a difference!! I noted the hum, even with the Clean settings and it got progressively worse with other presets but I didn't realize how much the new power supply would eliminate it. They gave me the same line about environmental factors but the only thing I changed was the power supply with a grounded plug and there is absolutely NO extraneous noise. All I get now is what comes from the guitar with the added effects from the selected tones. IT IS AMAZING!! I couldn't believe how much it cleaned up the sound. There is no question that the power supply is the issue.



  • I can only absolutely agree with that.



  • @cmcwillieb

    I’d be very interested in testing one of the after market units you bought. Could you post a link or failing that the brand model and if possible the input/output specs. A model number would be very helpful as well. Many thanks in advance. I’m trying to get a friend of my sons to put a couple power supplies up on an oscilloscope and look at the out put for various types of noise. Knowing that you have one that largely eliminated the hum relative to the OEM PS makes for a great baseline. Thanks again. Keoki