Hum! Solved with grounded DTK power supply.
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I got my DTK supply and plugged it in. Hum totally gone. Same Voltage rating. More amps but my understanding is that the Spark will only pull the amps that it needs.
"A higher voltage than a device is designed for will most likely blow up some components, but amperage is derived from how much current is actually drawn, based on the device's resistance, so having “too much” is not a problem and will do no harm."
So the voltage spec on the DTK is the same as that shipped with the SPARK. There is probably just as much chance that the power supply that shipped with the Spark is putting out the wrong voltage as the voltage rating on the DTK. I know that I saw someone here who shipped his DTK back because he measured the voltage and it said it was higher than 19 amps. They are both made in China. I will take my chances. The hum was intolerable. I sort of doubt that DTK is shipping power supplies putting out higher voltage than rated because if they did they would be blowing up a lot of laptops and the rating on the device would not be 4+ stars on Amazon. ( I wonder if that person who measured the voltage measures the voltage on all his power supplies when he gets them?)
Fact is that PG should have shipped the unit with a grounded power supply. That might have added $5 to the price. I mean really?
Dtk 19V 4.74A 90W for Asus Toshiba Ac Adapter Laptop Computer Charger Notebook PC Power Cord Supply Source Plug Connector: 5.5 x 2.5mm. is the product description I ordered from Amazon. $18 fix.
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I've heard noise problems can be corrected by connecting to a laptop via usb. Does it work if the computer is turned off?
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@rexlarsenphoto apparently not, from other postings I've read. The computer must be turned on so that the circuit is completed and the computer's chassis is grounded.
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@r_koby I've got that same power supply and when I tested it, it worked great. And even though the plug was a tiny bit looser than the original PG power supply (it should be 5.5mmx2.1mm instead of the 5.5mmx2.5mm of the DTK power supply) I have no fear of it falling out while playing. Such a small expense to pay for the security and the ability to use the amp while waiting for a replacement power supply from PG, if a person has asked for one. Given PG's statements that grounded power supplies are out of stock and won't be back in stock for a few weeks, at least people can use the amp now with the DTK power supply and when the replacement finally shows up from PG they'll have a spare.
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@dhbailey , @r_koby & @rexlarsenphoto ,
Guys I’m trying get a handle on wharpt exactly PG is shipping out as a replacement power supply, if you haven’t seen my “OEM Power Supply...” thread on the switching Power supplies provided by PG, could you check out the questions I posted in my self reply and perhaps take a couple of minutes to respond if and when you guys get your replacements from PG. Much appreciated.
Thanks! Keoki
Oh yeah @r_koby, I think you’ve got a typo in your original post, “I saw someone here who shipped his DTK back because he measured the voltage and it said it was higher than 19 amps.” I assume you meant 19 volts?
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The DTK power supply worked for me also. Big difference. Thanks to whoever posted that.
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@dhbailey I appreciate it, thanks a lot.
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@keoki Yes. He measured higher volts. Sorry.
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I think someone may have mentioned this before,
the output dc voltage on the adapter is always couple volts higher than stated, if you just put a multimeter and check the voltage.
it drops to correct permissible voltage when under load. -
@crystalpit If we were speaking about 'unregulated' power supplies your statement would be correct in that the output voltage would be dependent on current draw (load) as well as input voltage. Even then, however, you can't assume just any load is going to cause the necessary voltage drop to bring the output to the correct level. The load and power supply would need to be spec'd to each other as well as to the input voltage. But when discussing the SMPS units we are using with the Spark amplifiers we are speaking of 'regulated' power supplies. The regulator circuitry on a well designed SMPS is intended to continuously supply the rated voltage at any current draw (even under no load) so long as it does not exceed the maximum current rating. There should be minimal, if any, voltage sag while operating within the load rating, but definitely not a couple of volts. I have seem SMPS designs that will not power on unless there is a load and some that will fail in short order if not connected to a load (cheap/bad design), but none that were designed to provide more than the stated output voltage to whatever tolerance they were designed.
The typical tolerance for a regulated power supply is +- 5%, such as your typical ATX power supply in a desktop PC, but higher-end units have much tighter tolerances than that. So to get 'a couple volts' over spec using the rather loose +-5% we'd be talking about a 40V or more SMPS for it to still be in spec. But not on a 19V unit like we are dealing with here.
When I was testing the output of various other 19V SMPS units I have access to while troubleshooting the noise issue with the Spark none measured more than 19.38V (and that one was the original one shipped with the Spark). All the rest were between 18.89V and 19.25V. The only one that measured more than 20V was the DTK.
I would be very careful connecting a regulated power supply spec'd at 19V that was measuring an output of 21V to anything I was not certain could handle those 2 extra volts. 2V may not seem like much extra, but it can do more harm than you think if you are not familiar with the circuit design and tolerances of whatever you are connecting it to.
