combatting large transformer noise in multiFX box, Pictures included

[sjaltenb]

hello,

I just receieved my custom transformer from a small company and they did an awesome job! Looks to be standard EI but with a belly shield (?) and a tap for the shield that will go to ground. It has 120V primaries and 14 individual windings, with each FX board getting its own PSU.

All PSUs will be highly regulated and filtered. Wiring from transformer to PSU is shielded with tap grounding to a bus. Wiring from PSUs to FX are shielded as well with the tap grounding to the PSU board. The fuzz and Boost are 30" away from the Xformer, with the closest high gain FX (RAT) at 24". The closest PCB is the electric mistress at 7".

Here is my board: http://www.diystompboxes.com/smfforum/index.php?topic=70440.0

Every wire on the board is shielded, including pots.

So do I need to mount this thing in an iron box? What about the PSUs? The problem is, if i mount the transfomer in the box, i'll have like 17 wires coming out, all pretty thick, so some big holes  in the box.

Suggestions are much appreciated! Also, ignore all the power stuff in the pictures, thats all been replaced.

[sjaltenb]

Updated pictures:
the Xformer would go directly to the right of the small hole in the back left corner... mounted on the small lip so it when the board is rightside up, its actually sitting on the bottom.





sorry for the bad pics of the Xformer, dont have my camera....

[km-r]

first i would like to comment...

man youve got a mostrous pedalboard! thats pretty awesome...
im not really an expert with EMI and shielding...

maybe placing the effects section in a metal box will eliminate most of the EMI comming
from the PSU and the outside world [radio stations etc]... while boxing up the psu will just reject the EMI from the tranny.
maybe you can try lining up your pedal board with aluminum tape. since cheap n nasty aluminum tapes are non conductive on the sticky side, you can connect each aluminum strips [as long as possible] with thumbtacks...
you might want to shield the tranny too because the guitar pickups might get EMI's from it.

ok, another thing but i might be wrong here...

i dont really think you really need the 14 individual windings... ground loops happen only when theres a loop... omg.
so its possible to have only one power spot [with a large cap] and connect all ground points from the effects to that spot.
then as for the signal path, you dont need two wires [signal and ground] since the signal ground is also the power ground so theres only one signal path for the signal going to effects through effects and the star ground [main ground stop] is just the common ground point.

my 2c but i might be wrong... correct me, i could learn.

[sjaltenb]

Thanks...

Well i was going by R.G.'s article about the Spyder, also, i wanted the absolute cleanest possible power and so i wanted each effect to have its own regulated power supply, which is basically like using a battery, so I wanted to use seperate windings. in the article he explains this is the only complete way to prevent power ground loops.

I should have noted, the entire inside of the board is coated with EMF Cu-Pro Coat shielding paint! http://www.lessemf.com/paint.html -- its supposed to be some pretty good stuff. Hopefully this will do a good job preventing noise from entering/leaving the board. My old board was lined with copper and it got messy and just looked awful. (and cuts you up pretty bad too!) The 120v Mains will be connected directly to the wooden enclosure and therefor the shielding paint.


anyways, yes your right i will not be connecting the boards ground to ground, they the signal will simply travel from in--switches--out, board grounds will (hopefully) just tie into the power grounds, etc.


***all of the above is in the "i think" category

[Auke Haarsma]

Sometimes this project scares me Stephen! You put so much time, effort and money into the power/shielding section and I still have to do all that for my project .

No tips to add, just posting to say "Keep up the great work!"  This thing will rock when it is finished!

[sjaltenb]

haha hey auke, hows yours goin??

I wouldnt say a lot of money, time thinking? yes. building the power PSUs is going to be relatively cheap, and the transformer i had made in the czech republic at a VERY good price for me. The only other thing is the shielded wire really, which i get for $20/100ft.

Anyways, Im probably going overboard with all the shielding and stuff but I would rather do it right the first time, its doing it wrong that costs you $$$$