noise problems with digital fx and OneSpot

[tempus]

Hey all;

Got a OneSpot for Christmas in the hope of getting rid of a bunch of wall warts. Here's my setup:

Boss CS2 compressor => Zoom G2Nu multiFX => Boss NS2 noise suppressor. I've also got a Zoom A2 for my piezo in a separate signal path. These are all switched in and out of the signal path (except the NS2 which is always in the signal path) by a DIY switching matrix. The 1Spot is powering all this stuff fine, but I now have a lot more noise in my signal ( I was previously using a separate adaptor for each of the Zoom pedals and 1 for both boss pedals). When the G2 is on, there is a high pitched whine (that goes away when I turn the G2 off), even if it isn't switched into the signal path, and it's made worse when the compressor is on and/or the dirty channel of the amp is on. When the A2 is on (and it's never in the electric signal path) there's quite a bit more hiss overall, which is again exacerbated by the compressor and dirty channel of the amp.

From this it seems that the problem is in the power supply somehow, and that there's some digital crap invading my signal path. Does anyone have any ideas to get rid of this, or of some way to isolate things without going back to multiple wall warts?

Thanks

[ashcat_lt]

I got a onespot a while back and find it unusable.  Even filtered by my overkill pedal power distro box it injects way too much noise.  The daisy chain thingy it came with comes in handy, but the wart itself is useless.

[CurtisWCole]

In my experience, the multi-fx units need to have they're own power supply. They just don't play we'll with others.

Curtis

[Mac Walker]

I've noticed this with a one-spot and a Zoom 505, with other effects daisy chained.  I wonder if it is because the Zoom unit is not fully shielded (the base plate is metal but the rest is just plastic, I think Behringer pedals are the same way)?  Maybe the Zoom is dumping noise back on the power bus because of lack of shielding where the power supply is plugged in?  Just a thought....

[tempus]

I don't think it's as much the 1Spot as it is the mixing of digital and analog FX. I didn't notice an increase in noise in my other pedals, and the noise is always added by the digital pedals. I've just been doing some drawing, and (someone correct me if I'm wrong) I'm pretty sure daisy chaining is the same thing as running all the power cables in parallel. I don't really see any other way to do it (I was thinking of having the 1Spot come into a board and distribute power from a buss there, but as I said i can't really see that they'rll be any difference electrically.

Any other thoughts?

[ashcat_lt]

My PSU is heavily filtered and is not daisy chained.  Each pedal has its own parallel jack with a cap across it.  I have used it with a number of (non-switching) wallwarts for several years.  I do get a little more noise with the GigaDelay plugged in, but its not a deal breaker.  I tried the 1spot in a couple different configurations, including lowering one single analog pedal and had unacceptable levels of noise.

[R.G.]

As you probably all know by now, I'm quite interested in situations and pedals that don't work well with the 1Spot.

We know of some already, and in fact post a list of pedals that don't play nicely with the 1Spot on the web page.

They are, in general, digital pedals which  contain their own internal switching power supply to make 5V or 3.3V or whatever the digital needs out of an incoming 9V supply.

I believe the generic problem is that the internal switcher pulls big pulses of current at frequencies similar to but not synchronized with the switching on the 1Spot. I have tuned out noise issues on some pedals by forcing a "victim" 1Spot to change frequencies to synch up with the digital noise a pedal puts on the incoming power line. This is not, of course, a usable technique in general.

The frequencies involved in this clash of the switchers are up where voodoo rules rule and the solutions are difficult to filter in the simple analog sense and need RF solutions.

There are literally many thousands of the 1Spot out in the world working well with great numbers of analog and digital effects, so we have a lot of votes for "it works fine". But there are always marginal situations. When some kind of special case comes along that does not work well, I try to dig into it and find out what I can do in the next rev of the design to eliminate the issues, if that's possible. For some perspective:

My PSU is heavily filtered and is not daisy chained.

I'm taking this to mean that you have a power supply distribution box of some kind. Is this correct?

Each pedal has its own parallel jack with a cap across it.

At the frequencies of modern switching power supplies, a few millimeters of wire can be an inductor, a capacitor, or a tuned circuit and/or antenna. A cap across a parallel jack may or may not look like a capacitor at all up in the MHz ranges of the switching harmonics.

I have used it with a number of (non-switching) wallwarts for several years.  I do get a little more noise with the GigaDelay plugged in, but its not a deal breaker. 

What I find odd about this is that with the Gigadelay there ia any noise at all in the setup. What that says is that the Gigadelay (which I'm not familiar with at all) is generating enough noise to be heard in other pedals on the same power even if it's powered through a linear regulated power supply, which are generally good about reducing RF noise.

I tried the 1spot in a couple different configurations, including lowering one single analog pedal and had unacceptable levels of noise.

I'm quite interested in the situation where you have one analog-only pedal and a single 1Spot, but had unacceptable levels of noise. What kind of noise?

It is always possible that you accidentally got a defective 1Spot. That can happen, no matter how we try to stamp it out. But all 1Spots are tested with a high gain analog pedal before leaving the factory, so there may also be some oddity in the interaction with this pedal.

I'd like to try to figure out what's happening.

This process is how we found out about AC adapters killing pedals; that was blamed on 1Spots until we found the cause. It's also how we found out about shorting the inputs of unprotected regulators killing the regulators. That was also attributed to 1Spots until we dug the info out.

[ashcat_lt]

RG - I'd be happy to work with you to figure out what's going on here.  I bought it because I had heard good things.  I honestly tried it one time the day I got it, was dissatisfied, and haven't touched the wart itself since.  Unfortunately my work schedule the next few days means that I'll have plenty of time to hang out here, but no chance to touch my pedals.  Definitely on the list of things to do ASAFP.

I do have a DIY power distro box.  I've made several to the same basic design, basically copied from an SKB brand powered pedalboard thing.  A smallish resistor into a BAC across the input and smaller caps across each individual output.  The one I tested with is built into a single gang Raco switch box with a true-bypass feedback looper.

I'll try to get my crap together and run some more tests soon.

[tempus]

I appreciate your concern here RG. Just to clarify my situation, the 2 digital pedals that I'm having trouble with (Zoom G2Nu and Zoom A2) no doubt "contain their own internal switching power supply to make 5V or 3.3V or whatever the digital needs out of an incoming 9V supply", since they can be power via USB or 2 AA batteries. The G2 produces a high pitched whine (which is not terribly noticeable; it mostly gets filtered out by my noise suppressor), and the A2 produces a much more noticeable white noise. That one's kind of  a head scratcher, and it appears in both the guitar amp that my humbucker signal chain feeds (although it's not actually in that signal chain) and the PA that my piezo feeds (it is in that signal chain).

The 1Spot is also powering 2 analog pedals and my uC based switching matrix with no issues, so I think in my case the issue is the switching war, for which it sounds like there is no solution.

Thanks again

Oh one more thing RG - the G2 is fine when I use the supplied wall wart, which is definitely a switcher (it's awfully small and light for a 500mA supply), so maybe they engineered it to work specially with the G2?

[pinkjimiphoton]

i wouldn't use the one spot with the zoom. one spots work GREAT with "analog" pedals, provided there are no ground loops, or charge pumps in the stuff connected to them.

you may wanna run the analog pedals with the one spot, and the zooms with the power supplies designed for them, but i doubt it will help. on the zooms (or in their documentation) it will state that due to fcc regulations, they have to accept noise and may produce it as well. not being shielded is absolutlely part of it, but mostly it's the crud that digital pedals dump into the power supplies...all the "noise" gets sent to ground, which of course means it gets sent to everything else connected.
i'd reccomend putting the noise suppressor before the zoom pedal so the noise reduction can filter out crap getting put into the zoom and amplified (as well as not gating off your reverbs and delays and stuff) and either run the zooms with their own PSU's, or, even better, (especially for less noise) with batteries. that will take care of most of your noise issues right there. sucks, but like most things of this nature, a certain amount of compromise is inevitable.

another trick you could try that helps sometimes is to use 2 conductor plus shield "microphone" cable between the pedals...hook up one conductor to tip, and one to sleeve on each plug, but connect the shield/braid to ONLY ONE SIDE. that way you can "float" the shielding between the pedals...one way will be quieter than the other. it's different with each pedal i've used this with, but you can get quite a bit of noise reduction by doing this...noticeable, probably 3-4 db quieter. ideally, you want the "shield" to only connect to "earth/ground" on one side...generally the shielded end would go to the amp, the unshielded to the last effect in the line's output.. and so on down the line. in practice tho, sometimes reversing the polarity can help nuke noise, much like a second coil bucking hum.
it's not perfect...but hey, any port in a storm, right?

can also try putting a small cap to ground from the hot inside the plugs on the cables. it may make it worse tho.

a buffer between the offending boxes also may help a little...

but for quietest operation, and i know it's a drag, batteries rule.

i have a whammy pedal i dearly love, but i can't use it live cuz it won't play nicely with my analog boxes, and i use them a lot more than i do the whammy. it's just the nature of the beast, sadly...those digital multis are intended pretty much to be standalone. once ya add other pedals, all bets are off.

is there an effects loop in your amp? if so, try patcing a cable into it, and see if the "whine" diminishes. if it does, get some plastic safe contact cleaner, and with the amp off, spray a quick blast into the send and return  jacks, and repeatedly plug a plug into each jack. sometimes the contact of the switching jacks commonly used can oxidize and make a crummy contact, and lead to squeals and noise, too.. good luck!!

[tempus]

Hey all;

A while back I posted this thread. At the time, I had the following problems:

1. whine from Zoom G2Nu
2. hiss from Zoom A2

Neither of these conditions present themselves using the provided Zoom adaptor. At the time RG suggested that there may be some weird interaction between the 1Spot's switching frequency and the circuitry in the Zoom pedals that allow them to be powered from lower voltage sources (like USB). In my case at least, I think he's wrong.

I'm using the 1Spot to power my uC based switching matrix (running at 4 MHz), as well as a Boss CS2 and NS2, plus the above mentioned digitals. I don't really have tons of time to troubleshoot this kind of stuff, but I was messing around today and found that if I use the 1Spot to power only either of the pedals individually, it's as clean as anything (i.e., no power supply noise added). I've concluded that in my case at least, there must be some interaction among the devices I'm powering, particularly with the digital Zoom pedals. I'm going to try to figure out some way to isolate them while still using the 1Spot in my rare spare time. Hopefully something like a DC-DC converter will help. Does anyone else have any other ideas?

So for anyone who's been apprehensive about buying a 1Spot, contrary to some reports, it actually works perfectly on digital pedals individually (at least the Zoom ones I've got) - it's when you start combining them that you may run into problems.

I'll update when I get more info...

[Mark Hammer]

These problems are not unique to the OneSpot.  I've used several different supplies with my ToneCore pedals, including switching and non-switching supplies.  Daisy chaining digital pedals on the same supply CAN be a crapshoot.  A switching adaptor that works like a charm and provides dead quiet power with one pedal, turns into a set of bagpipes from hell when used with multiple digital pedals.

[R.G.]

Now that I think of it, all the setups where there has been really bad trouble has more than one pedal, and it vanished with only one pedal.

I wonder why digital supplies with switching internal power supplies don't go one more step and make the switching regulators ... isolating... with another winding on the inductors that have to be there anyway. I suspect I could talk a boss and an accountant into this if I could convince them that we could make up for the added cost in the pedal by not shipping a matching power supply at all.

Hmmmm...

Nah. Never work. The idea is not to atone for your own sins, but to make them not obviously yours. 

[tempus]

After a little messing around, I think I've solved the noise problem using a 1Spot and different digital/analog pedals.

If I connect the output of the 1Spot that's going to either of the digital pedals to a DC-DC converter, the high pitched noise/whine goes away. Unfortunately, when the effect is engaged (i.e., not bypassed) there is a lower frequency whine, but this can be eliminated by the noise reduction module in the pedal. Not perfect, but it works. I also tried just using a 7809 for isolation. This had no effect on the G2nu, but did get rid of the hiss on the A2. The voltage is dropped to 7.7v, however, but as long as this isn't an issue (is it?) I should be good to go with a 7809 on the A2 and the DC-DC converter on the G2. I haven't actually wired them in yet, so I have to make sure that the DC-DC converter doesn't induce any noise in the surrounding circuitry of my switching unit.

Again, not perfect, but there is a way around it. Any other ideas?

[R.G.]

Actually, that does help. My experimentation showed no amount of filtering or regulating did much good on the + side. Apparently it's ground-conducted noise or common-mode noise on both lines.

I'm guessing the DC-DC converter is an isolating converter?

(parenthetically, so is the 1Spot; it just happens to have a rectifier/filter in front of it to make DC out of the AC line, like all off-line switchers)

[tempus]

The DC-DC converter is this:
http://www.suntekstore.com/goods-14002072-lm2596_dc-dc_step-down_adjustable_power_supply_module.html

I've measured and the ground is common (there's a statement for ya) to the input and output. It's actually too bad that the linear regulator didn't work for both; it would've been an easy and non-noisy way to isolate everything. Do you think the reduced voltage on the A2 could damage the unit? It seems to work fine at this voltage, but I don't know if there may be any long term effects.

Thanks R.G.

[R.G.]

Hmmm.

Grinding on that. I may have to order a converter and try to recreate this.

[tempus]

Hold that order form R.G..

I had some time to mess around with it today, and found that inserting a low value series resistor also cures the noise problem, on either pedal. I started with 1.1 ohm, then 5.1, then 10, and all allowed enough current to power the pedal but blocked the high frequency whine from the G2 and the hiss from the A2. Much more elegant and streamlined solution than inserting a linear or switching regulator in there. It's hard to tell if there's any difference between this and using separate supplies, but I wonder if a bypass cap might improve noise levels even further. I'm only going by listening tests, since I don't have the proper gear to analyze it more scientifically. I could've sworn I tried this when I discovered the problem originally, but evidently I didn't because it works like a charm now.

One more addendum to that - I tried dropping a couple of caps of different sizes to ground to see if that made any difference, but if anything this seemed to increase the noise slightly, in the form of a very slight high pitched whine. This was using a 470uF. I also tried switching between the 1Spot powering the G2Nu and batteries, and there was no audible difference. Again, I don't have the tools to measure this, but I couldn't hear any change.