Compairing two switching power supplies on an oscilloscope

[Rockhorst]

Just to be save: I'm not in any way affiliated with either of the products mentioned below. I do occasionally repair effects for a local guitar store and this is done purely out of curiosity (theirs and mine). Ok, here we go.

I've always liked my 1Spot power supply and from what I've read, RG Keen committed a great deal of research time to the 1Spot. Now recently, local Dutch pedal designer Dr.No has released a switching power supply. There's been quite some debate about it, since people discovered the brand sticker on the unit could be removed and revealed it to be a possibly rebranded el cheapo Stagg power supply. Some claim that it was a labeling mistake at the factory and that the unit is actually different from a 'real' Stagg. The jury is still out on that one. I expect to have a definite answer by the end of the week (waiting for a Stagg unit to come in for comparison). But to keep me entertained, I hooked both unit up to an oscilloscope (settings: 0.5 us/div, 50 mV/div). Here's the results:

1Spot


Dr.No


To my untrained eye, the 1Spot signal looks a lot cleaner compared to the Dr.No, which has a lot of extra junk (resulting in a somewhat fuzzy picture). What I'm unsure about is how much you would actually notice of this in practice. My guess would be that less junk is better, the cleaner the power going in, the less potential for noise, whistling and what not. Anybody with some more experience with power supplies and scope signals that can shed some light on this issue?

[twin1965]

I'm no expert but my experience with Switch Mode Power Supplies is that they can introduce some noise into certain types of circuit. I haven't used the One Spot so can't comment on it.

I've had issues with powering circuits with LFO's such as phasers and Univibes. Also an FET based booster. They all exhibited a lot of noise. I eventually bought a Voodoo Lab PSU that solved all the noise problems. This PSU has a large transfomer and isolated outputs. Maybe that's the difference.

Interested to see your findings.

Sent from my GT-I9100 using Tapatalk 2

[Willybomb]

Interesting.  I have crappy power in this flat and everything sounds noisy...