Hiss when amp turns off... or on? Mystified...

[mrsuspend]

Sorry if this is slightly off topic but it's doing me in and it does involve my hand built pedals...
At our rehearsal studios me and the bass player share the same power line. Every time he turns his amp on off my pedals start hissing like crazy.
If I then step on ANY pedal on the board it stops. It doesn't seem to matter which pedals are actually on at the time.
My amp is not involved since the same thing happens if I plug directly into the PA.
Is this some strange grounding issue? Or is it impedance related in some way? I can't get my head around this one... 

My chain: Colorsound Overdriver => Treble Booster => Pickup Booster => Orange Squeezer => CE2 Chorus => Chicklet Reverb.
True bypass and built by me except the Pickup Booster and Reverb(which is buffered).

Yours Sincerely,
Magnus "At my wit's end"

[GibsonGM]

1) how are you powering your pedals - with a regulated wall-wart?
2) Does the hiss "time out" after a while, or stay as long as you care to let it?
3) Are both of your amps grounded properly ("3 prong)?
4) Have you tested the outlet(s) with a tester to be sure they're wired ok?

Just out of curiosity of the thing, I'd move both of you guys' stuff over to another circuit and see if it still happens! 

[R.G.]

GM's comments are correct.

The "hiss" is one thing you can hear from RF oscillation. It's an "angrier" sound than thermal noise hiss. I'm guessing that because it starts and stops from some event, it's RF. And something about the amp on/off starts it.

But GM's comments are how to start.

[mrsuspend]

Thanks for replying GM!

I'm powering my board with a One Spot.
As far as I know the hiss doesn't stop or taper off although I haven't waited very long as it's quite annoying...
The amps are grounded.
When I've occasionally used my own ungrounded 60's amp I've had to run a ground cable from the chassis to the ground prong or the vocal mic would shock me.
I haven't used a tester on the cabling but as the above worked I guess the grounding as such is OK?
Because of the outlet placing it's a bit awkward to move us but I could run a longish cable over just to see what happens.

/Magnus

1) how are you powering your pedals - with a regulated wall-wart?
2) Does the hiss "time out" after a while, or stay as long as you care to let it?
3) Are both of your amps grounded properly ("3 prong)?
4) Have you tested the outlet(s) with a tester to be sure they're wired ok?

Just out of curiosity of the thing, I'd move both of you guys' stuff over to another circuit and see if it still happens! 

[mrsuspend]

Thanks RG! The hiss sounds a lot like a white noise generator, much more aggressive than the accumulated hiss of a few pedals.

GM's comments are correct.

The "hiss" is one thing you can hear from RF oscillation. It's an "angrier" sound than thermal noise hiss. I'm guessing that because it starts and stops from some event, it's RF. And something about the amp on/off starts it.

But GM's comments are how to start.

[R.G.]

Hmmmm. Your comments do suggest something may be odd about the AC power grounding if the 60s amp can generate shocks.

As a side note, you ought to get that 60s amp fixed by installing a three-wire grounded cord. It's much safer. I'd hate to lose you to an ungrounded amp now that you're all growed up and playing guitar and making pedals and such.   

This only happening when the bass player cycles power suggests that something the bass amp is doing is driving the pedal power supply nuts. What kind of amp is he using? Is it one of those big class D rigs or an SVT?

[mrsuspend]

Thanks for the concern RG,  I will eventually but I don't use that amp very often. My everyday amp is a Vox Night Train.
Our Bassist's amp is an old Marshall something (grounded). However, this happened with our previous bass player as well!
Could there be something going on with the wall wiring? We're renting a room in an old air raid shelter but the wiring seems recent enough.
How could I test for faults? I have multimeters but seldom go higher than 18 volts... 

/Magnus

Hmmmm. Your comments do suggest something may be odd about the AC power grounding if the 60s amp can generate shocks.

As a side note, you ought to get that 60s amp fixed by installing a three-wire grounded cord. It's much safer. I'd hate to lose you to an ungrounded amp now that you're all growed up and playing guitar and making pedals and such.   

This only happening when the bass player cycles power suggests that something the bass amp is doing is driving the pedal power supply nuts. What kind of amp is he using? Is it one of those big class D rigs or an SVT?

[R.G.]

Home improvement places frequently carry AC wall test plugs. These plug into a receptacle and tell you by means of colored lights whether all is well with the wiring. I highly recommend these to every musician that plugs equipment into the wall for gigs. Some venues are not well wired.

They're not very expensive. I would try that. Or simply haul the amps and pedals to another place and try a different building for a test instrument.  

It's worth noting that it could be a problem with the pedal power supply unit as well, but the other things are more likely. Has this always been this way, slowly gotten worse, or started suddenly?

[mrsuspend]

It's always been like this in this room.
We gigged at a pub tonight and I had no problems at all.
I will test the AC as you suggest and report the findings. Thanks! 

/Magnus

Home improvement places frequently carry AC wall test plugs. These plug into a receptacle and tell you by means of colored lights whether all is well with the wiring. I highly recommend these to every musician that plugs equipment into the wall for gigs. Some venues are not well wired.

They're not very expensive. I would try that. Or simply haul the amps and pedals to another place and try a different building for a test instrument.  

It's worth noting that it could be a problem with the pedal power supply unit as well, but the other things are more likely. Has this always been this way, slowly gotten worse, or started suddenly?

[GibsonGM]

Home improvement places frequently carry AC wall test plugs. These plug into a receptacle and tell you by means of colored lights whether all is well with the wiring. I highly recommend these to every musician that plugs equipment into the wall for gigs. Some venues are not well wired.

They're not very expensive. I would try that. Or simply haul the amps and pedals to another place and try a different building for a test instrument. 

It's worth noting that it could be a problem with the pedal power supply unit as well, but the other things are more likely. Has this always been this way, slowly gotten worse, or started suddenly?

Other than what we discussed above, I'd be at a loss to explain that...something somewhere is radiating RF, and seems to have to do with the AC wiring.  Tons of things can do this, both in his amp and yours!  Like R.G.  said - make it a priority to get a plug-in outlet tester with 3 lights.  Usually "amber amber red", which will tell you how the plug is wired up.   I expect you'll find an open ground or something.  Having, and using, one is important - I've found some HORRIBLE wiring over the years, potentially deadly, and the little $8 tester has kept us safe.  Worth every penny.

Sometimes things are finicky...I've had just ONE bar (neon sign) mess with some of my stuff, but NO other place will do it.   This is where we enter the "art" of design/build...test that outlet and report back!    Now everyone is curious, ha ha.

[mrsuspend]

Thanks GM, I will!

/Magnus

Home improvement places frequently carry AC wall test plugs. These plug into a receptacle and tell you by means of colored lights whether all is well with the wiring. I highly recommend these to every musician that plugs equipment into the wall for gigs. Some venues are not well wired.

They're not very expensive. I would try that. Or simply haul the amps and pedals to another place and try a different building for a test instrument. 

It's worth noting that it could be a problem with the pedal power supply unit as well, but the other things are more likely. Has this always been this way, slowly gotten worse, or started suddenly?

Other than what we discussed above, I'd be at a loss to explain that...something somewhere is radiating RF, and seems to have to do with the AC wiring.  Tons of things can do this, both in his amp and yours!  Like R.G.  said - make it a priority to get a plug-in outlet tester with 3 lights.  Usually "amber amber red", which will tell you how the plug is wired up.   I expect you'll find an open ground or something.  Having, and using, one is important - I've found some HORRIBLE wiring over the years, potentially deadly, and the little $8 tester has kept us safe.  Worth every penny.

Sometimes things are finicky...I've had just ONE bar (neon sign) mess with some of my stuff, but NO other place will do it.   This is where we enter the "art" of design/build...test that outlet and report back!    Now everyone is curious, ha ha.

[guitarkill]

Sometimes when everything seems to be right but something is still wrong, the little tester in this video can come in handy. At least in terms of seeing if something has a floating ground anyway.

https://www.youtube.com/watch?v=6ZGokkrsO_Y

I think RG may be right, somehow you may be getting an ultrasonic oscillation in your system. Maybe when your friend has his bass amp on it stabilizes everything but when he turns it off things go haywire. I don't get why that would be happening but it seems to be the case. Something an electrical engineer told me once about harmonic oscillation happening in building grounding comes to mind. This is basically a "dirty ground", or a very noisey ground system in a building. Maybe in your case it's at a very high frequency (above human hearing).

[GibsonGM]

Circuits can FOR SURE suffer from oscillation problems, both sub-audible and ultra high (dog) frequencies.  We can't hear either, but they wreak havoc with equipment!  And dirty grounds inside amps, pedals, both, whatever - sure can cause weird issues like this.    At that point, you're now dealing with a small RADIO rather than an amp or pedal!!    Junk on the ground *sigh*   Star grounding techniques are Awesome!

You may experience this simply because there's something going on for one or both of you, and on that particular circuit, it goes over the top.   One of those odd conditions where inductive and cap. reactances are the same, or some such thing.     

Weird, tho!  You guys should make a video!