Pedalboard Powering issue

[jkokura]

Okay, I've been running various pedalboard setups for a long while now, and one of them is on a Pedaltrain Nano, which is an amazing little setup that I really like. Tuner into compressor into overdrive into El Capistan Delay with Favourite switch. It's super simple, sounds great, and I love the easy size and use.

Except when I power the stinking thing.

The El Capistan doesn't like to be daisy chained. If I daisy chain the El Cap with the other pedals for powering it, I get this really high pitch squeal. It's very noticeable and very annoying when you aren't playing, but isn't audible when you aren't.

The easy solution is to use two power supplies, one for the El Cap and another for the other pedals. But this is DIY, and we don't always go for the Easy Solution, do we! I hate running multiple power supplies. Defeats the purpose of using the small setup.

So, the mission I'm on is to take a generic power supply, like the One Spot or something like that, and send it into a box I can mount under the Pedaltrain, then output at least two isolated 9V signals. The real key is that I need it to mount under the Nano, because I don't want it visible. The other important factor to this project is that the El Cap needs 250mA of power. The other pedals may not need that much individually, but they will collectively.

So - isolating power in a 1590A or 1590B for mounting under a PT Nano? Can we do it? Ideas?

Jacob

[midwayfair]

There's something unusual about the Strymon power supplies, beyond just their mA output and that they're a separate supply. If I try to use them to power a gain pedal, it's horribly noisy, almost like the case isn't grounded, regardless of how good the power filtering is in the pedal.

There isn't really a way to "isolate" a split DC source. The thing that makes power supplies isolated is the transformers. You would need to make a two-output, two-transformer power supply that can give you at least 250mA (and preferably 350 to be safe), and that's just not going to be smaller than a one spot and Strymong power supply.

If it helps, I use a One Spot and the El Cap's supply on a small power strip on my board, and it takes up very little room. I think it would fit mounted under a PT Nano, but I'm not totally certain.

[RobA]

I've been playing with the Murata and Recom isolated DC/DC converters that come in the SIP packages, and they work really well. I'm seriously thinking about moving to a 5V power supply with a USB micro B input and then using the converters to give me the voltage I need, either in the pedal or out from the distribution box depending on the pedal. In all the testing I've done so far, I haven't run into any problems with pedal's power supplies interacting. And, with just a 220µF cap on the output of the converter, my scope shows the noise level to be at the same level as powering with a 9V battery.

I haven't tried any of the high current versions of the converters yet, but they do make them with a high enough power rating to run your pedal. The higher current types are a bit bigger and do cost more though. Here's the link to one that should work from Mouser http://www.mouser.com/ds/2/281/KDC_MEE3C.A01-202925.pdf

One of the reasons I'm thinking about going this way is that big USB battery packs are going really cheap now. So, you could either use a standard USB power supply (like a cellphone charger) or use one of the battery packs, depending on the situation.

[jkokura]

I think an Ideal system for me would be to run an IEC power cable into one end of the PT-Nano, and that's why running two power supplies to the pedalboard is so annoying to me - one hefty cable being plugged in is a lot more durable and a lot less finicky than plugging a pair of supplies into something, then running those thin, terribly twisted and fragile wall wart ends off to the pedal.

Perhaps the simplest hack is to put an IEC adapter into one end of the nano, then cut the end off a multi plug extension cable and use that female end to put the pair of wall warts into, then figure a way out to fasten it all under the Nano.

Jacob

[RobA]

If you are going to run an IEC cable to the board, then you could make half of one of these http://www.generalguitargadgets.com/diagrams/ss-ps4_sc.pdf and meet your needs in a smaller package than two wall warts. It would be cleaner too.

[jkokura]

The trick is, I have no idea what transformer I would use.

Jacob

[midwayfair]

The trick is, I have no idea what transformer I would use.

Jacob

Smallbear categorizes them by milliamps, which is helpful. This one can power the strymon.
http://www.smallbearelec.com/servlet/Detail?no=597

[jkokura]

Yeah, that's not going to work. It's much to big.

Jacob

[electrosonic]

Since the problem is cause by signal ground and audio ground coupling, why not isolate the audio. If you look at the geofex hum free splitter (the one that doesn't use a transformer), and put that in before the delay pedal it should solve the problem. My iPad crashes every time I try to look at it but I think it has a buffer driving a differential output, so the output is isolated from ground. That circuit could fit in a 1590A and be placed on your pedal board.

Andrew

[alanp]

Cioks DC8 or Schizophrenic? (Their website cioks.com seems to have been hacked at the moment, so look at vendor sites instead.)

[brucer]

Hi Jacob.

Is your Nano the older one with square tubing?  It might be possible to mod it and attach a power supply underneath.  These links feature the Fuel Tank Jr, but it seems like you might need the ISO-5:

http://www.tdpri.com/forum/stomp-box/255563-pedaltrain-nano.html
www.tdpri.com/forum/stomp-box/296043-pedaltrain-mini-has-no-room-power-supply.html

Just a thought.  Bruce.

[RobA]

Something like this http://www.mouser.com/ds/2/410/FP24-500-223590.pdf should do the job. Smallbear has a similar transformer http://www.smallbearelec.com/servlet/Detail?no=339, but it doesn't have quite enough current handling to do the strymon. Mouser doesn't carry the transformer that is suggested in the GGG parts list, but they do have some others available that are pretty much the same thing. The main thing about setting up the isolated supplies is to have the dual secondaries. After that, you just need the 12V secondaries and one that can deliver enough current to drive the pedals.

[RobA]

There are also these types that I think would do the job, http://www.digikey.com/product-detail/en/70042K/TE70042-ND/154891. These are really similar to the parts that are in the EHX tube pedals. In the EHX pedals, they are running the other way, they take 12V in and put out 230V on the secondaries.

That particular one I linked at Digi-Key would even be a bit of overkill on the current. It does 417mA on each secondary. You could probable go with the 7VA version and be safe.

[jkokura]

Both of those last two options are getting very close. The only limitation I see with either option is that they are precisely the same height as the interior of a 1590B enclosure. Perfect in one way, because they are the right idea, but too large to get in the max box sizes.

But now I know what I'm looking for. I'm basically perusing the Mouser/Digikey catalog to see if I can get a 110V in 2-4x 9V out toroid or flatpack transformer at about .9" tall.

Jacob

[jkokura]

For example, looking at this transformer, do I have it right that I'll get two taps of 500mA, or just one tap of 500mA off of this?

http://www.mouser.com/ds/2/410/FP24-250-223587.pdf

Jacob