DIY DC Suppy

Started by FreeTime, March 28, 2017, 01:37:56 AM

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FreeTime

I'd like to build a DC supply to power all my pedals and once. Like this:

                                              DC (Battery)
                                               |
                                               |
                                               ---------------------------------
                                               |            |            |            |
                                               |            |            |            |
                               GKPX--->GP10 --->GR55--->VG99--->Looper ---> Ear

                   
Looking at that design tells me I'll be plagued with Ground loops. Besides cleaning up the 'ol ball-o-wires, getting rid of ground loops was the point of doing this because I already have odd things going on, things that don't happen when I only have one thing plugged in. My thought was that since I'm running off cork-sniffing quality pure DC that those gremlins would go away, but by tying all the PSU grounds together I'm making a loop with the audio cable ground.

Even if I cobble up something with a LiPo and a 7809 for each device I still can't get away from the common ground. The kneejerk guy in my head says just use a seperate battery pack for each unit but then I'm just re-inventing the wheel.

Any thoughts ?


Hurricane

 ;)

Good Question :

This thread I will follow .
My needs are similar .

EZ :

HR

8)

gumtown

I would worry more about installing fuses in the battery supply, but I assume that is already done.

The best solution is to have each supply 'galvanic isolated', by means of a SMPS with multiple isolated output transformer windings.

A poor mans option is to place a 10 ohm resistor in the + and - lead of each output, to 'minimise' the loop coupling effect.
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

FreeTime

Yes, fused with a tiny lightbulb across it that tells me at a glance if the fuse is blown.

Plan B would be to use an audio isolation transformer between each device. I know they were common for turntables, I wonder what it does for audio quality especially once the core saturates with the levels we're using.

Does anyone have any experience with this ?

gumtown

Do you actually have earth loop problems at this moment?
Free "GR-55 FloorBoard" editor software from https://sourceforge.net/projects/grfloorboard/

Elantric

#5
QuotePlan B would be to use an audio isolation transformer between each device. I know they were common for turntables, I wonder what it does for audio quality especially once the core saturates with the levels we're using.

Does anyone have any experience with this ?



http://www.generalguitargadgets.com/effects-projects/power-supplies/four-output-isolated/




Details:
http://wiki.diyrecordingequipment.com/projects/geo-fex-spyder-pedal-power-supply/







I just use one of these  1SPOT CS12 - - but its not battery powered
http://truetone.com/power-supplies/1-spot-pro/1-spot-pro-cs12/




The 1 SPOT Pro Story


For many years, Truetone has made musicians' lives easier with the 1 SPOT, the original compact pedalboard power supply. It works so well that a lot of musicians never felt the need to get one of those brick-style power supplies, and we here at Truetone didn't see the need for those either, even though they were quite popular. Bob Weil, founder of Truetone, explains:
"A lot of people over the years had told us that we should make a power brick. Even some of my own staff urged me to do it, but I didn't want to for two reasons. First, I knew the 1 SPOT could power just about every pedal out there, so I didn't see the need. Second, I didn't want to make just another knock-off of someone else's power brick. If we were going to make one, we were going to do it our way and have features that nobody else could offer. As pedal designs changed and it became more common for digital pedals to require isolation and for others to need something other than 9Vdc, I finally saw a reason for us to design a power brick."

"It took 3 years and lots of experimentation, but we were finally able to design a 1 SPOT Pro, using our own proprietary technology to give musicians all the features they need for today's pedalboards. The original 1 SPOT still works great for most musicians, but for those who need more power and versatility, the 1 SPOT Pro fills the need perfectly."

Features

1 SPOT TECHNOLOGY9VAC OUTPUTMULTIPLE VOLTAGESWORLDWIDE INPUT VOLTAGERUGGED STEEL HOUSINGCABLESPURE ISOLATIONPEDALTRAIN MOUNTING BRACKETSENERGY EFFICIENT
1 SPOT Technology

1 SPOT Technology... what does that mean and why should I care? Technically, it's switching power supply technology, which is very different than what anyone has ever put inside a power brick. Normally, you would find just a big transformer and a handful of small electronic components inside a power brick... old tech that hasn't changed in decades and has a lot of limitations. We took the same switching power supply technology found in our famous 1 SPOT and scaled it up to make the 1 SPOT Pro models. With much more space to work with, we were able to completely eliminate noise, provide total electrical isolation between outputs, create multiple voltages, and still give you the ability to use it anywhere in the world.

A major benefit of using a switching power supply is that it can handle far more current (power being pulled out of it) than any transformer-based power supply. Although we had to put power rating labels on each output to satisfy certification agencies (yes, we actually certified these, unlike most companies), the outputs can generally handle far more than the label shows. For example, you can connect a 300mA pedal to a 200mA output, without causing any problems. With a transformer-based power supply, you can't get away with that. The important thing is to not exceed the total of all the labels. With a CS7, the output labels add up to 1900mA total. That means the total current draw of all your pedals should be less than 1900mA. That total current rating is roughly double the current load of the most common power brick, for a lot less money.


Elantric

#6




https://www.premierguitar.com/articles/Powering_Your_Board


If you experience ground loop noise - there are several ways to resolve this.

if it's permanent configuration of FX pedals on your FX pedal board - you can stop ground loops on unbalanced audio FX by enforcing only ONE common Ground physical connection path between each FX  :

*   use the audio shields on the audio cables as the common ground reference that ties all FX to the same Ground, and then simply disconnect all but ONE Ground connection from the DC power supply that feeds your FX power input jacks. Connect only one wire, the (+) DC voltage connection from the power supply to most of your target FX  power input jacks.

or

*   use the common DC (-)  connection on the DC power cables as the common ground reference that ties all FX to the same Ground, and then simply disconnect all but ONE Ground connection on all audio cables that interconnect the devices. Typically accomplish with custom audio cables that interconnect each FX pedal that has the Cable Shield connection floating on one end only.
 

FreeTime

Quote from: gumtown on March 28, 2017, 12:03:31 PM
Do you actually have earth loop problems at this moment?

There is some noise when using the VG/GR/GP together but I attribute that to shoddy cable layout/too much EMI.

There was one loud one coming from a second computer but I fixed that one with a DI box with ground lift. (Should be called a ground disconnect)

Elantric

QuoteThere is some noise when using the VG/GR/GP together

COMMON issue  - traced to a Ground loop from your common GK-13 pin cable source.

FreeTime

Quote from: Elantric on March 28, 2017, 12:25:38 PM

*   use the audio shields on the audio cables as the common ground reference that ties all FX to the same Ground, and then simply disconnect all but ONE Ground connection from the DC power supply that feeds your FX power input jacks. Connect only one wire, the (+) DC voltage connection from the power supply to most of your target FX  power input jacks.

or

*   use the common DC (-)  connection on the DC power cables as the common ground reference that ties all FX to the same Ground, and then simply disconnect all but ONE Ground connection on all audio cables that interconnect the devices. Typically accomplish with custom audio cables that interconnect each FX pedal that has the Cable Shield connection floating on one end only.


Option B sounds like a good plan. A quick check with an ohm-meter shows there is continuity between the power connector and the sleeve of the instrument cable on VG/GR/GP. I would probably ground the instrument cables at the mixer and cut the shield at the device.




I looked at the individual transformer way but that defeated the point of DC. The losses going from DC to AC and then back to DC again add up even with modern inverters. LiPo will punish you for your ignorance if you discharge them too deeply as I learned when I thought it would be a good idea to put one on a trolling motor (short burst to get sailboat on trailer) without undervoltage protection.

Elantric

#10
If your goal is 100% battery power- consider multiple Li-Po battery packs

On Amazon i purchased a few of these 9VDC battery packs for $15 each last year
http://www.amazon.com/PwrBlast-External-Battery-Hd-Hdx-Tab-portable/dp/B0061TK28O?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s01
8000mah Li-Po Battery Pack


or

$25 for this one
XTPower 10000mAh External Battery Pack (Dual USB Output 5V plus DC Output 9V / 12V 2A)

http://www.amazon.com/gp/product/B00935L44E/ref=oh_aui_detailpage_o00_s01?ie=UTF8&psc=1


Like buying fish on Friday - The price at Amazon varies widely week to week.