True issues with the Spark



  • @radu7 said in True issues with the Spark:

    Well, I discovered I had another power supply on hand already that worked perfectly! It's actually the power supply for this little guy:

    https://www.hotoneaudio.com/products/nano-legacy-floor/mojo-attack

    It's got a 5.5x2.5mm connector so the fit is a bit loose in the Spark, but the voltage output on it is the same as the power supply that shipped with my Spark per my meter.

    I powered the Spark up with it and it's dead silent now. If anyone is interested it is a Delta Electronics model 'ADP-90MD H' 19V/4.74A supply. I wouldn't say it's worth hunting this particular one down or anything, just putting this out there as an FYI. I'm familiar with the Delta brand though as they are a huge OEM for server power supplies for the likes of Dell, HP, etc...

    Also, someone on another thread was asking about this model power supply:

    https://www.parts-express.com/19v-25a-dc-switching-power-supply-adapter-with-21-x-55mm-center-(-)-plug-4-ft-ac-grounded-c--129-184

    I happened to have this same power supply on hand and I can confirm that even though it has a three-prong connector it does not resolve the hum/noise issue. It performs the same as the stock power supply with regards to noise levels in my case.

    @radu7

    Curious are either of the substitutes “switching“ power supplies? Also I’d you have a chance read sarawasons reply and our discussion in my thread “The OEM Power Supply...” Simply having a grounded wall plug does not assure you of a fix for the hum.



  • @keoki Both of the substitutes I've tested are SMPS units. For AC to DC regulated power supplies, that are used in applications such as with the Spark, it will either be a SMPS or a linear power supply. A linear power supply for this application would be quite heavy/bulky/expensive. I have a linear lab/bench power supply that I may test the Spark with, but there's not a lot of point in it other than for experimentation's sake as that power supply costs more than the Spark did.

    That is quite correct to say that simply having a three-prong plug won't resolve the issue as we don't know the actual design of the SMPS we are testing. For all we know that ground prong isn't even connected internally. I've disassembled quite a few of these types of power supplies over the years and it is shocking to see the vast differences in quality and design of these SMPS units. Some of them simply had the ground pin tied to some metal shielding and nothing more.

    Once I've finished-up a few other projects I'm working on I may test these various supplies' output qualities on a DSO under various loads to see how noisy the output of them actually is, voltage sag, etc... For now though my particular issue with hum, which seems to be nowhere near the level that others are experiencing, is resolvable when using a different SMPS (that just happens to have a three-prong AC plug) or when using the original SMPS and connecting the chassis of the Spark to mains earth.

    If I get a chance I'll test this new SMPS that resolves the hum issue for me with the ground prong bypassed. If the hum returns then there's no doubt that there is something with the design of that particular supply which incorporates the ground prong/earth connection that mitigates the issue in my particular case.

    Now the root cause of the actual issue is another story. Just to say 'it's a grounding issue' may or may not be correct. All we know is that grounding the amp chassis corrects the problem in some cases and using a different SMPS that happens to have a three-prong AC connector in others. Then again there appears to be others that don't have the issue at all using the factory provided power supply. Throw in the variability of other factors such as differences in each person's house wiring, local sources of interference, etc... and you've got your work cut out for you determining a single root cause (if a 'single' one even exists).

    I'll check out your other thread in a few minutes. I did see it last night, but have not read any of the updates just yet.



  • @davidscott95 I too notice sustain problems more at very low volumes. I don't have the grounded power adapter yet. Thanks for your comment.



  • @rexlarsenphoto @DavidScott95 I'm having the same issue with the sound cutting out when I pluck lightly. No sustain, the sound just drops. Curious if you've been able to find a solution to this?



  • I've found a solution and am very happy with it



  • @crystalpit Okay -- I'll take the bait. What was the solution you found that you're very happy with?



  • @braunaa Check your noise gate settings and turn it down or off.



  • @dhbailey the spark is just a toy to play around with, it does everything average and some app features below average.
    To expect anything more is ludicrous.
    if you want to get serious, one needs to go back to basics and use a regular amp.



  • @crystalpit So you haven't found a solution using the Spark -- to get better sustain you use a better amp. That makes sense -- I agree that we sometimes are expecting a bit much from the Spark. But a string vibrating over a pickup should be able to be amplified by any amplifier. That the Spark fails to produce a sound when a string is continuing to vibrate is a problem that should be able to be fixed by a firmware upgrade that improves how the noise gate functions. When every other amp that a person might own allows that vibrating string to be heard longer but the Spark cuts the sound off much earlier, it's a problem with the design of the Spark, toy or not. Even toys can be made to function properly.



  • @dhbailey correct