Some interesting research on power supplies

Jack DeVille

Member
Messages
2,439
So...
I ran into a strange phenomena a few weeks back after getting a new pedal. Well, the behavior got me thinking and before I knew it, I was taking measurements and recording findings.
I decided to publish my results, and hopefully, everyone can benefit from this experiment.

Its a fun read, with pictures and even some sound clips of power! Check it out:
http://www.mrblackpedals.com/blogs/...re-than-you-need-to-know-about-power-supplies

I hope folks can benefit from this information as much as I have!
:rockin
 
Messages
5,123
Geez! Nice post/write up.

(For those wondering, no, Jack doesn't have a pocket protector and coke bottle glasses with tape around the arm.)

Jack, did you by chance try your experiment with a little dedicated boss 9 volt power adapter?
 
Messages
999
Very interesting as always! So you did this entirely at home? Do you think the results would be different if you conducted the experiment somewhere else with different wiring? I admit ignorance on electricity but have read a lot about "dirty power" in certain houses or clubs, so I am curious if the results would be the same no matter where you were.
 

MegaMan9

Member
Messages
798
I think the noise is worse with the switching adapter...plus, it seems to add noise even when the pedal is off, while the battery and isolated psu doesn't
 

tnt365

Member
Messages
3,044
This article answered some questions I had concerning battery power vs isolated units. I think many people notice a higher noise floor when using their isolated units, I sure notice it with my PP2+. I would love to see a power supply that emulated battery power/cut the noise floor.
 

drbob1

Gold Supporting Member
Messages
27,622
Couple interesting things:

1. There's obviously some radio interference going on in some of the samples. Suggests that RF isolation of your shop wiring or the pedal itself need some work?

2. The isolated power supply is using power from a transformer/capacitance filtered power supply to drive individual voltage regulators, right? Is the noise inherent in the voltage regulator or could you improve things by using a switching power supply to drive a voltage regulator?

The net result of this is that it appears that "clean power" so far has been snake oil and there's still a market for a device that doesn't add power supply ripple and noise to pedals. I wonder how those 9v NiMH battery packs compare to the 9v carbon or 9v Alkaline cells?
 
Messages
999
Another variable I'd like to hear in comparison would be the Sanyo Pedal Juice, or other rechargeable supplies (e.g. the Volto when it becomes available).
 

Vulteroz

Member
Messages
358
2. The isolated power supply is using power from a transformer/capacitance filtered power supply to drive individual voltage regulators, right?

Maybe not. There are some power supplies with isolated outputs witch work on switching principle and there are some with oldfashioned transformators.

Jack, what power adapter with isolated outputs where you using here?
 

stinkfoot

Member
Messages
6,128
Its a fun read, with pictures and even some sound clips of power! Check it out:
http://www.mrblackpedals.com/blogs/...re-than-you-need-to-know-about-power-supplies
Interesting read, indeed. Of course, noise floor with a single pedal is one thing - when you get into daisy-chaining, all sorts of other factors come into play, which may or may not tip the scale over in the isolated transformer supply's favour.

Interestingly enough, just the other day I came across an article on a pedalboard Vertex built for Mike Landau, where they did some interesting stuff. Firstly, they built a battery box with 4 separate 9v batteries to feed the dirt pedals, since Mike felt they sounded better with battery power. Just to make it road-safe, they also fit relays which automatically switch over to a power supply feed if any of the batteries were to go mid-gig. Another thing they did was custom build the power supplies so they only fed the (other) pedals the amount of current they actually drew (as opposed to feeding a 10mA pedal from a 200mA source), and the consensus was that the pedals sounded better that way. But then we're getting into Eric Johnson territory... :)

2. The isolated power supply is using power from a transformer/capacitance filtered power supply to drive individual voltage regulators, right?
To get proper isolation, just having individual voltage regulators isn't enough. All the isolated psu's I've seen so far has had mains transformers with individual secondaries (one for each isolated output or output section), which means the isolation starts even before the rectifier section. From there on, everything (rectifier bridges, filtering, regulation) is kept separate for each output.

Maybe not. There are some power supplies with isolated outputs witch work on switching principle and there are some with oldfashioned transformators.
I've never seen a power supply with isolated outputs that used switching technology. Just out of curiosity, can you name any of them?
 

Rex Nomad

Member
Messages
584
I've always preferred batteries. Is there a good 9 volt rechargeable out there - something like the newer Sanyo Eneloop AA and AAA batteries? I've had great success with these in flashlights, clocks, etc. But I haven't heard of anything with that quality in a 9 volt. If they could hold the charge as long as a regular 9 volt, that would be a winner for me.
 

Adagietto

Silver Supporting Member
Messages
3,194
I've always preferred batteries. Is there a good 9 volt rechargeable out there - something like the newer Sanyo Eneloop AA and AAA batteries? I've had great success with these in flashlights, clocks, etc. But I haven't heard of anything with that quality in a 9 volt. If they could hold the charge as long as a regular 9 volt, that would be a winner for me.
I've been using Powerex Imedion 9.6V 230 mAh batteries for pedals (and other things). They seem to work fine, probably about Eneloop quality. The best price I've found is directly from Thomas Distributing.
 

walterw

Platinum Supporting Member
Messages
38,016
I've been using Powerex Imedion 9.6V 230 mAh batteries for pedals (and other things). They seem to work fine, probably about Eneloop quality. The best price I've found is directly from Thomas Distributing.
how long do they last, though?

the rap on rechargeables is that they typically lose power just sitting around faster than typical low-draw pedals drain alkaline batteries!

the rechargeables make sense in high-drain stuff like wireless, where a 9V is getting killed in one night.

(i use the thomas distributing 9V ipower lithiums, which are awesome in my in-ear pack, they actually have more power than alkalines.)
 

Adagietto

Silver Supporting Member
Messages
3,194
how long do they last, though?

the rap on rechargeables is that they typically lose power just sitting around faster than typical low-draw pedals drain alkaline batteries!
These are low-self-discharge NiMH batteries. They can sit around for weeks or months and retain some charge, unlike standard NiMH batteries.
 

Vulteroz

Member
Messages
358
I've never seen a power supply with isolated outputs that used switching technology. Just out of curiosity, can you name any of them?
1- JOYO Power Suply 2



http://www.joyoaudio.com/en/product/show_174.html

And i beleve T-Rex Fuel Tank Junior, because of it's size and on the T-Rex web site they say ONLY for Fuel Tank Chameleon this: "Traditional EI Transformer" and this: "...Placement; as far away from pedals as possible (preferable at least last in the chain close to Analog/drive pedals) in order to reduce noise interference in the signal chain." And they dont say that for Fuel Tank Junior. Because Fuel Tank Junior is multiple switching in one housing resulting in isolated outputs
 




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