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PSU ground problems - diy power conditioning |
wavehead
Ultra Wiggler
Joined: 14 Nov 2009
Last Visit: 23 May 2013
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 Posted: Thu Apr 25, 2013 8:57 pm Post subject: PSU ground problems - diy power conditioning |
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hopefully i'm just missing something really obvious here and there are some ways i can fix this.
i have a Power One (HCC-15-A3) powering a little over 9U of eurorack and have some ground issues i am unsure of how to fix right now. i know grounding can get extremely complicated and it's very likely my house has some ground loops, but i still want to try and do something (besides getting my house all re-wired at least for now).
one of the more obvious things is that when a cable's tip touches any of the metal on the faceplates of the modules or the outside of the jack the signal cuts out completely (until it's removed from any contact).
what i noticed just now, because it's hard to hear it, is that the quiet hum the PSU makes actually changes in tone if my hand is on the faceplates/hardware of the modular. it's hard to hear, but it's clear that it's happening and seems it would also have to be a ground issue.
i had the thing wired up by a professional tech in a slanted mixer case (the EWI one a lot of people here use mostly made of wood), but maybe a better ground from the PSU to the rails is needed? anyone have suggestions for the best way to do this?
also wondering what i can do about the dirty power signal in this house, but there are just so many options and obviously a lot of them are super expensive. anyone have a good, cheaper solution for this? is there such thing as a DIY power conditioner? |
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data
Learning to Wiggle
Joined: 11 May 2010
Last Visit: 02 May 2013
Posts: 8
Location: Lala Land
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| Posted: Fri Apr 26, 2013 1:17 am Post subject: Re: PSU ground problems - diy power conditioning |
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| wavehead wrote: | | one of the more obvious things is that when a cable's tip touches any of the metal on the faceplates of the modules or the outside of the jack the signal cuts out completely (until it's removed from any contact). |
Not easy to diagnose sight unseen, but this sounds like much more than misconnected ground. Something is shorted.
Ground loops or mismatches typically manifest as hum or other noises -- not major behavioral shifts like this.
| wavehead wrote: | | what i noticed just now, because it's hard to hear it, is that the quiet hum the PSU makes actually changes in tone if my hand is on the faceplates/hardware of the modular. it's hard to hear, but it's clear that it's happening and seems it would also have to be a ground issue. |
This is definitely not normal. I don't think this is just ground wiring. Make sure rats haven't been munching on stuff.
| wavehead wrote: | | also wondering what i can do about the dirty power signal in this house, but there are just so many options and obviously a lot of them are super expensive. anyone have a good, cheaper solution for this? is there such thing as a DIY power conditioner? |
A power conditioner is really not a worthwhile DIY project IMHO. At most you might look for a filter of some sort, but honestly if you have a decent power supply it's not going to help much, if at all.
Regarding house wiring problems: if you're paranoid, buy an outlet tester, shouldn't be more than US$15-$20. Mine is a device with a plug on it and LEDs which are meant to light up in a certain pattern if the wiring to the outlet is OK. Otherwise the LEDs will tell you what's wrong, like hot/neutral swapped, ground missing, etc.
Missing ground can be a problem in older houses. If you really need a good ground, you can tie off to a water pipe, or even drive a grounding spike. But unless you're building a world-class studio, or you have safety issues, or you have enemies in the city building inspection department, you should probably not worry about it too much. |
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diablojoy
Veteran Wiggler
Joined: 22 Jan 2010
Last Visit: 23 May 2013
Posts: 518
Location: melbourne
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| Posted: Fri Apr 26, 2013 3:00 am Post subject: |
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| Quote: | | one of the more obvious things is that when a cable's tip touches any of the metal on the faceplates of the modules or the outside of the jack the signal cuts out completely (until it's removed from any contact). |
I will assume since its euro modules these are 1/8 jacks and that we are talking of audio signal paths in that case
the tip is the live hot signal so when you touch the tip to something that is grounded either current will flow from an output or 0V will be presented to an input.
if its an input on the other end of the lead you are grounding that input will go silent , its at 0V afterall , that is normal
if we are talking about an output the amount of current is usually limited by the size of the resistor used on the output of the preceeding module a typical value used on the output of an opamp buffer is 1K but can be lower
The current required from the PSU then goes up, this can cause its normal hum to change in pitch, hard to know if there actually is a problem with out knowing what modules you are powering and if they even have buffered outputs or not,
but based on the descriptions so far i would say your grounding itself is fine , if you were hearing some permenant or intermittant horrible hum then i would say otherwise.
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daverj
Vintage Video Wiggler
Joined: 19 Jun 2009
Last Visit: 23 May 2013
Posts: 4821
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| Posted: Fri Apr 26, 2013 11:53 am Post subject: |
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If the cable is a signal from the output of a module, that signal is on the tip of the cable. When you go to patch that cable into an input and touch the tip to ground it shorts the signal out momentarily. That is normal. It won't hurt anything. Modules are designed to handle that.
One way around it is to plug the cable into the input side of the connection first, then plug the other end into the output. If you plug the cable into the output end first, then there is a live signal on the cable as you go to plug it into an input.
On the other hand, if doing that causes other modules to lose sound, or LEDs on other modules to go out, then something is wrong. It should only effect the signal being carried on the cable.
As for the hum. If the hum you are hearing is a mechanical vibration from the transformer vibrating, it is possible that it is vibrating the whole case and that touching parts of the case might change the sound because it dampens the vibration. If you feel that it is an electrical reaction and changes with a very light touch to metal but doesn't happen if you put a piece of plastic, paper or fabric between your finger and the metal, then it might be an electrical ground issue.
Much more likely that it is a mechanical vibration issue though.
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Graham Hinton
Wiggling with Experience
Joined: 02 Jul 2010
Last Visit: 22 May 2013
Posts: 382
Location: England
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| Posted: Fri Apr 26, 2013 5:43 pm Post subject: Re: PSU ground problems - diy power conditioning |
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| wavehead wrote: |
i have a Power One (HCC-15-A3) powering a little over 9U of eurorack and have some ground issues i am unsure of how to fix right now. i know grounding can get extremely complicated and it's very likely my house has some ground loops, but i still want to try and do something (besides getting my house all re-wired at least for now).
...
also wondering what i can do about the dirty power signal in this house, but there are just so many options and obviously a lot of them are super expensive. anyone have a good, cheaper solution for this? is there such thing as a DIY power conditioner? |
Phil, you are presupposing causes and as these questions keep coming up I'm going to use your one for a general answer, so nothing personal.
Firstly, if you need to ask something don't leap to conclusions. Grounding is not complicated, but you have to understand basic electrical circuits first. If you don't you won't understand the answer either.
If you are afraid of ground loops stay away from modular synthesizers because you make one every time you plug in a patchcord (apart from banana systems). It is not a problem until you connect two things together that have separate PSUs and then you can mostly get away with it because most synth modules are unity gain or less. Electricity does not spontaneously flow because there is a loop, there has to be something to provide the driving force and in most cases this is an amplifier.
In the US most mains wall outlets go back individually to the breaker board so there are not normally any loops, ground or anything else. If anything, in older houses you are more likely to have no ground, in which case you definitely need a rewire. In the UK room outlets are on a "ring main" which is a loop and every house has at least two, usually one per floor. This isn't a problem. Mains grounding is a safety issue it isn't anything to do with audio until you use it as a common reference between two pieces of equipment and then it is only local to them. In the US separate outlets would go all the way back to the breaker board, so it is better to have a mains distribution board close to the equipment connected to a one outlet.
You must have a safety ground because you are touching exposed metal parts. It is better not to use the ground as an audio common, which is why professional audio uses three wire balanced interconnections where the ground is only used for a screen.
With all mains wiring you have to conform to the regulations in your country. You are not a special case. People often think they need special grounds and actually make an unsafe installation. If there are problems it might be a fault in the mains wiring or in the audio wiring and only carefully listing the symptons is going to get a remote diagnosis. No-one can see your setup unless you post a picture. That may show something that you didn't think was important enough to mention.
Now what exactly is "dirty power"? You haven't said how this is manifesting itself.
You are sharing your electricity with thousands of people on the same substation. The only thing that separates you is the small resistances in breakers, fuses and cable. In UK house wiring you can get clicks from appliances like fridges and central heating that get into audio equipment. The fix is to make sure that they are on separate circuits and that is only the resistance of two breakers/fuses apart. In the US you have that anyway. Appliances with electric motors should be fitted with interference suppressors so if that is the problem that is what needs to be fixed. Digital equipment usually has mains filtering built in both to protect themselves from interference and from putting interference back onto the mains.
There is a class of gadgets that use mains wiring for communication, baby alarms, home automation, etc. Generally these are a bad idea to have around if you are half serious about audio. Just pull them out or switch them off when you want to work.
If you are wiring up an OEM PSU you can use a filtered IEC inlet rather than a plain one, but this is only going to attenuate signals above 1MHz.
The hum from your PSU is because it uses a rectangular transformer. Magnetic fields stray from corners and can vibrate any iron or steel nearby, eg panels. The more current is drawn the stronger the fields. The solution there is to use PSUs with toroidal transformers which keep the magnetic field constrained in a circle.
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wavehead
Ultra Wiggler
Joined: 14 Nov 2009
Last Visit: 23 May 2013
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| Posted: Fri Apr 26, 2013 6:40 pm Post subject: |
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thanks for chiming in guys, i know there wasn't much info to go off of and it's hard to present everything without a lot of pictures or tedious descriptions.
the outlet tester is a really good idea... the house is 100+ years old and rats have definitely chewed up their fair share of wiring.
i think the PSU hum is indeed most likely nothing but vibrations, but i really need to take a closer look to make any conclusions on that. pretty embarrassing if it is literally just the case vibrating.
| Quote: | | Appliances with electric motors should be fitted with interference suppressors so if that is the problem that is what needs to be fixed. |
the "dimmer" (a rotary switch) for the speed of the overhead fan in this room will make a loud click in my monitors every time it's adjusted - so this is definitely a problem, but how much of a problem and what it's contributing to i'm not sure of. i generally just keep the fan off these days.
everything is going to the same outlet (modular, computer, interface, monitors) via a power strip - i have been looking to get a higher quality "mains distribution board" and am not sure where to go. what actually makes a difference for these types of products is hard to discern, but having more protection for spikes in voltage might be a good idea.
is it any improvement to be powering things from a UPS with a pure sine-wave output? this isn't something i would necessarily get for audio-purposes, but i need one for the mac pro. |
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Graham Hinton
Wiggling with Experience
Joined: 02 Jul 2010
Last Visit: 22 May 2013
Posts: 382
Location: England
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| Posted: Sat Apr 27, 2013 4:41 am Post subject: |
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| wavehead wrote: |
the "dimmer" (a rotary switch) for the speed of the overhead fan in this room will make a loud click in my monitors every time it's adjusted - so this is definitely a problem, but how much of a problem and what it's contributing to i'm not sure of. i generally just keep the fan off these days.
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When you have switching interference from a source in the same room it may not necessarily be coming through the mains wiring. It may be radiated from the fan wiring and picked up by sensitive parts of circuits. A little experimentation would show which, but the problem might be solved by replacing the fan switch with a modern suppressed one. Do you still get clicks when the synthesizer or mixer output is turned down?
| Quote: |
everything is going to the same outlet (modular, computer, interface, monitors) via a power strip - i have been looking to get a higher quality "mains distribution board" and am not sure where to go. what actually makes a difference for these types of products is hard to discern, but having more protection for spikes in voltage might be a good idea.
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If it is cheap plastic at a bargain price and says "made in China" do not expect good performance. Quality types have more copper/brass between the outlets which you need for low impedance, especially in the ground being used for audio common.
There are better types made for fitting in the rear of 19" rack cabinets, either as a 19" unit or as a long strip that goes up one side. They tend to be in the several hundred £/$ bracket , but they are often thrown away in refits and it is worth checking eBay and surplus dealers. This sort of product.
| Quote: |
is it any improvement to be powering things from a UPS with a pure sine-wave output? this isn't something i would necessarily get for audio-purposes, but i need one for the mac pro. |
It's a bit of a sledgehammer to crack a walnut and it won't solve radiated spikes. I wouldn't share one with a computer system. There are different types of UPS, online and offline, and offline will not solve spike problems. You also need to know the total wattage of all your equipment.
Don't grab at straws. Definitely don't grab at "balanced" mains conditioners. You won't get a solution until you know what the problem really is, but you could waste a lot of money trying snake oil.
I prefer mains protection and filtering to be on a per equipment basis, and that is often omitted on OEM PSUs.
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wavehead
Ultra Wiggler
Joined: 14 Nov 2009
Last Visit: 23 May 2013
Posts: 816
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| Posted: Sat Apr 27, 2013 7:47 pm Post subject: |
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i get loud clicks from that fan switch with no synths or anything plugged into the interface... it goes right to the monitors (and will do this without the computer on as well). i haven't tested it to see if it comes through the modular or anything else because i generally avoid using it at all. the fan is a piece of shit and could probably fall down at some point anyway.
it does seem i may be best off waiting to eventually upgrade the PSU to something with a toroidal trans. in the mean time i am going try and seek on a nice power strip as that just seems a common sense thing to do for all my electronics.
if anyone knows where to find good deals on these in the US it would be greatly appreciated... can be hard to see what is snake oil and what isn't.
i guess there are a lot of small issues going on and isn't going to come down to any one or two simple solutions. some things like living on a hill near a radio tower are unavoidable, but ever since i got the RME interface i am using i get almost no interference/hum ever (at least no open interference not coming from synths, mixers etc.). |
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Graham Hinton
Wiggling with Experience
Joined: 02 Jul 2010
Last Visit: 22 May 2013
Posts: 382
Location: England
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| Posted: Sun Apr 28, 2013 6:46 am Post subject: |
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| wavehead wrote: | i get loud clicks from that fan switch with no synths or anything plugged into the interface... it goes right to the monitors (and will do this without the computer on as well). i haven't tested it to see if it comes through the modular or anything else because i generally avoid using it at all. the fan is a piece of shit and could probably fall down at some point anyway.
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Obviously sources of interference like this need eliminating, but before you do it is a useful way of testing the noise immunity of everything else.
You can waste a lot of money on solutions and not know if they are really working or not.
Monitor amplifiers are very often the cause of problems and usually that comes down to them being unbalanced or unisolated.
Do you still get clicks from the fan if the amplifier volume is turned down and if the input cables are disconnected? That would point to the interference coming up the mains cable. Is it grounded?
If they don't happen with the volume down, what are the input connectors and is there an input transformer option?
| Quote: |
in the mean time i am going try and seek on a nice power strip as that just seems a common sense thing to do for all my electronics.
if anyone knows where to find good deals on these in the US it would be greatly appreciated... can be hard to see what is snake oil and what isn't.
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Devices that "balance" the mains are snake oil. Mains transformers do that anyway.
Look for something with solid construction and weight and no fancy features. It's best to avoid companies aimed at hi-fi and home recording markets, look at professional recording or server installation suppliers.
| Quote: |
some things like living on a hill near a radio tower are unavoidable, but ever since i got the RME interface i am using i get almost no interference/hum ever (at least no open interference not coming from synths, mixers etc.). |
Most equipment is RF savvy now, but older gear may not be. It is a lot harder to demodulate FM than AM radio, where any diode in the right place can do it.
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