hum analysis, onespot vs. boss psa vs. alkaline 9 volt

[joegagan]

my brother is getting a stripped down rig together for an upcoming european tour. he doesn't want to take his pedalboard.
i was telling him about some of the posts here referring to different brands of power supplies being noisy.
he did his own test in protools, the onespot adaptor was quieter than a boss psa and an eveready 9 volts alkaline.

house AC power to this studio is good, did not test current on this day, but in the past is 118-121 volts.

test specifics:
Lakland 55-94 bass, active single coil, volume max, strings muted
Boss OC2 octave pedal in on position
Radial JDI passive DI
Massenburg 8300  mic preamp, gain @70 (max)
Digidesign 192 I/O into Pro Tools HD @ 24/88.1
Boss PSA-120S
Visual Sound Onespot
Eveready Alkaline 9 volt, tested at 10.45 volts

all of the files were normalized. gain was boosted after recording by 3600 %.  

9 volt battery in purple, boss psa in orange:


visual sound onespot in purple, boss psa in orange:

visual sound onespot in orange, battery in purple:

[R.G.]

I've run many similar tests, on many of the adapters on the market. In the switching power supply arena, there are variations with some of the adapters. It has to do with how well the control circuits deal with noise at higher frequencies than the first few harmonics of the power line, and how well damped the output circuits are.

There is a residual hum on almost all power supplies which can only be minimized, not eliminated, as a consequence of how the safety and EMI standards interact. In a well designed power supply this residual is quite small, less than the effect of varying and imperfect electrical wiring.

In fact, for doing a European tour, it's worth doing some thinking about how his amps will do with the wiring he'll find.  Carting along your own isolation/stepdown transformer is a true pain, but can get rid of a lot of hum in some situations.

[joegagan]

amps?

thanks rg.

they are running DIs into  PA systems with in ear monitors these days. jon plays bass with ottmar liebert. i am not sure how they do their power conversion for the pedals, DIs, etc , but they have pretty good people handling that stuff. they've been at it since 89, so they do hire good people.

[R.G.]

amps? they are running DIs into  PA systems with in ear monitors these days.

Well, never mind that "amps" stuff then! 

jon plays bass with ottmar liebert. i am not sure how they do their power conversion for the pedals, DIs, etc , but they have pretty good people handling that stuff. they've been at it since 89, so they do hire good people.

We've run the 1Spot and compared residual hum/noise, etc. against a number of other similar and competing power supplies, just to keep this particular issue in focus. They all hum some, as do linear regulated ones. Batteries are hum free, but that just gets you below the hum of the larger setup if you weren't already.

One thing that may be interesting. All 1Spots run from 100Vac to 250Vac. The plug shape is a convenience and a match to local sockets more than preventing voltage damage. It's the same  PCB in all 1Spots - only the outer plug pins and plastic change.

[joegagan]

thanks for that rg, i do recall now that you had mentioned that multi voltage feature before. sometimes i need to read it twice.

i will pass that along to jon, if he has adaptors it may possibly add some convenience for him.

for my own self, i use batteries everywhere i possibly can, a onespot where delay or other large draw is present.