Spyder PS questions

[Leevibe]

I recently built RG Keen's Spyder power supply using the Weber 120vac pedal transformer.  Aside from some heat-sinking stuff to work out, I'm really happy with the way it turned out.  All 9v taps are measuring at between 9.02 & 9.08 volts.  At 300mA each, it's loads of power. 

My first question has to do with isolation.  With my DMM, it's simple to verify that each filter/regulator circuit is completely isolated UNTIL I interconnect effects with instrument cables.  I hadn't really thought about it before, but as soon as pedals share a common ground connection through the signal cable, their power grounds also have continuity.  Again, this is easily proven by touching the metal tabs on the regulators with my DMM probes.  With this being the case, what advantage do I have in having isolated power?  I'm no longer isolated.  I know there's something I'm missing, but I can't wrap my brain around it.

My second question has to do with fuses.  I'm using two separate fuses, one for the PS circuitry and one for the courtesy outlet.  Right now I have a .6 amp fuse on the PS and 2 amp on the outlet.  I just guessed at those values.  Any recommendations?

links:

Spyder circuit:  http://www.geofex.com/article_folders/spyder/spyder.htm
Weber transformer:  https://taweber.powweb.com/store/pdlxfmr.gif

[selfdestroyer]

I unfortunately can not help with your question as I have never made a PSU before, but I had to tell you that thing looks awesome. You did a great job. Hope you get your questions answered.

Cody

[Leevibe]

I unfortunately can not help with your question as I have never made a PSU before, but I had to tell you that thing looks awesome. You did a great job. Hope you get your questions answered.

Cody

Thanks for the vote of confidence, Cody. It's a bit scary posting pics of all that spaghetti given the amazing gut shots I've seen on this forum. 

[selfdestroyer]

I unfortunately can not help with your question as I have never made a PSU before, but I had to tell you that thing looks awesome. You did a great job. Hope you get your questions answered.

Cody

Thanks for the vote of confidence, Cody. It's a bit scary posting pics of all that spaghetti given the amazing gut shots I've seen on this forum.

I think it looks great. There is only so much you can do with that many wires.

Cody

[Leevibe]

Hope it's ok to bump this thread.

I have a perfectly good 1 Spot that I've never had issues with.  I'm afraid I may have wasted a bunch of time building a neato box that adds a lot of weight to my board. 

What am I missing on the ground loop/isolation thing?

[jimijam]

the problem lies in having more than 1 path to ground. this causes ground loop hum. isolated power circuits remove the second path. so the are less noisey and make daisychaining pos ground fuzz pedals possible.

[Leevibe]

Thanks for the reply, jimijam.  I appreciate it.  I understand that the idea is to eliminate ground loops.  The thing that I didn't foresee is that the grounds of all those nicely isolated taps get tied right back together as soon as you interconnect pedals with instrument cable because signal ground is tied to power ground. 

If I touch my DMM leads to two different regulators in my isolated supply, there is no continuity, even if I have them powering pedals.  If I then interconnect those pedals with a patch cable, there is continuity between the grounds of the regulators.  This happens via the sleeve connection of the patch cable.  How does this eliminate ground loops?

[mattlee0037]

Well I would think that it would get rid of it because it's not an actual ground loop. They are grounded commonly through the pedals, but to complete the loop you would need to ground the two dc jacks together? So I think you have ground 'U's maybe which seem perfectly fine and how all isolate powers work. Also awesome job, I really need to make something like this, although it seems a little intimidating.

[Leevibe]

Well I would think that it would get rid of it because it's not an actual ground loop. They are grounded commonly through the pedals, but to complete the loop you would need to ground the two dc jacks together? So I think you have ground 'U's maybe which seem perfectly fine and how all isolate powers work. Also awesome job, I really need to make something like this, although it seems a little intimidating.

That's exactly what's happening. If you think about it, it will dawn on you that when you connect the signal sleeves of two effects you are simultaneously tying the grounds of the power jacks.

And you can totally do it!  It looks like a complex build but its just the same simple circuit repeated over and over.  I added some bells and whistles but you wouldnt have to do that. 

[mattlee0037]

Yeah are the switches for the 'dying battery' mod that RG wrote about? I've been looking up all the info for this and it seems doable. Definitely high on my list. What enclosure did you do use and how did you suspend the board?

[Leevibe]

Yeah are the switches for the 'dying battery' mod that RG wrote about? I've been looking up all the info for this and it seems doable. Definitely high on my list. What enclosure did you do use and how did you suspend the board?

The switches allow me to take the last two pairs of jacks and switch them into series to give me two 18v jacks instead of four 9v.  I can then switch either of those 18v down to 12v using additional regulators.

[Leevibe]

What enclosure did you do use and how did you suspend the board?

It's this one:

http://www.frys.com/product/2090830?site=sr:SEARCH:MAIN_RSLT_PG

I got it at Fry's in Wilsonville, OR

Here is a chart that shows the dimensions of their cases.  It's part #4012.

The case has slots for PCB mounting.  It will perfectly fit a 4" wide board.  The board I used was shy of that so I suspended one edge in the slot and used screws and nylon standoffs for the opposite edge.  These enclosures are really nice to work with and I plan to use one for a pedal build.  They have them in a shallower depth.

[Leevibe]

What enclosure did you do use and how did you suspend the board?

It's this one:

http://www.frys.com/product/2090830?site=sr:SEARCH:MAIN_RSLT_PG

I got it at Fry's in Wilsonville, OR

Here is a chart that shows the dimensions of their cases.  It's part #4012.

The case has slots for PCB mounting.  It will perfectly fit a 4" wide board.  The board I used was shy of that so I suspended one edge in the slot and used screws and nylon standoffs for the opposite edge.  These enclosures are really nice to work with and I plan to use one for a pedal build.  They have them in a shallower depth.

Oops, didn't post the second link. Sorry!

http://contextengineering.com/split_body_enclosures.html

[playpunk]

Would there be any problem in doubling a couple of the outputs, so instead of one at 9v and 300ma, you could have 2 9v 150ma each with a common ground?

So you could have a 10 output ps.

[mattlee0037]

It'd be easier to just chain 2 pedals to one outlet. You could easily power your whole dirt section (assuming its analog) off of one outlet. Or you could do 2 pedals to one outlet, which would have the same hum canceling as 2 9v 150ma sharing a common ground.