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Power Isolation Transformer Channel Strips
Old 9th February 2010
  #1
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Question Power Isolation Transformer

Why would someone use an isolation transformer for ac power? Under what circumstances would it be essential and what would happen if you didn't use one?
Old 9th February 2010
  #2
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Quote:
Originally Posted by JustAnotherUser View Post
Why would someone use an isolation transformer for ac power? Under what circumstances would it be essential and what would happen if you didn't use one?
Here's a good FAQ: FAQ's About Balanced Power
Old 9th February 2010
  #3
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not all isolation transformers output balanced power, do they?
Old 9th February 2010
  #4
Gear interested
 

Strongly recomend doing this symetrically driven from 2 phases AC with the Audio Consulting Transformers. Serge Schmidlin is a going new directions in audio. His trafos run cool cool. And important use on trafo for each device with a combo recitifier/trafo. It acts like a firewall, switching powersupplies send alot of ripples back into the AC.

News

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Philosophy
We would like to explain our philosophy :

Time may have come to give you further information about how products are being developed and manufactured at Audio Consulting.
We choose to list a series of issues that we have accepted as guide lines over some three decades of R&D.
This list may be completed in the future.
If physical measurements are certainly important in what we do, the final word always comes to the ear.

1. First issue: the mains power supply
We consider the mains as inadequate a source of power for the audio equipment of the resolution that we are aiming for.
Today, the loads that are connected to the mains are more and more of the non linear type, which dramatically lowers the power and energy transfer to audio circuits. This has a dramatic impact on sound.

6moons.com - industry features: A Visit To Audio Consulting
Attached Files
File Type: pdf Power.pdf (261.7 KB, 1585 views)
Old 9th February 2010
  #5
Gear interested
 

Isolation transformers and balanced power are two different animals.

Isolation transformers are nice to filter out EMI and harmonics that might be on house power from lighting equipment or other sources that muck up the power source (motors and motor controllers would be other bad offenders, although not as common).

One must be careful with grounding when using isolation transformers. Once your power is isolated from house or stage power, there is a greater chance for a voltage potential between your isolated equipment and non-isolated equipment that you might interface with. This isn't an issue if your recording setup is a standalone system, but becomes an issue if you interface with the house audio system.

Balanced power takes things a few steps further by eliminating additional noise and whatnot by providing a balanced voltage supply (as well as isolation) to your equipment. The Eqi=tech website has lots of good information on balanced power.

Balanced power supplies or transformers will cost you much more than just an isolation transformer.

Some folks insist on isolated power, some on balanced, some get by just fine without either. Do you have to have it? You know what they say about opinions and assholes....

Terry
Old 10th February 2010
  #6
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Remoteness's Avatar
Some very good replies...

I'd like to add this tag to this discussion: transformer

The tag search I presented above has quite a few threads about this topic.
They are not all about power transformers, but the thread titles will help guide you in the right direction.
Old 10th February 2010
  #7
Gear maniac
 

thanks
Old 11th February 2010
  #8
Gear interested
 

Quote:
Originally Posted by db_dude View Post
Isolation transformers and balanced power are two different animals.

Isolation transformers are nice to filter out EMI and harmonics that might be on house power from lighting equipment or other sources that muck up the power source (motors and motor controllers would be other bad offenders, although not as common).

One must be careful with grounding when using isolation transformers. Once your power is isolated from house or stage power, there is a greater chance for a voltage potential between your isolated equipment and non-isolated equipment that you might interface with. This isn't an issue if your recording setup is a standalone system, but becomes an issue if you interface with the house audio system.

Balanced power takes things a few steps further by eliminating additional noise and whatnot by providing a balanced voltage supply (as well as isolation) to your equipment. The Eqi=tech website has lots of good information on balanced power. In Switzerland we have 230 AC on the wall plugs I mesured 35 -90V AC on the cases. And even when all componets or simply one was grounded we could here the difference with this method

Balanced power supplies or transformers will cost you much more than just an isolation transformer.

Some folks insist on isolated power, some on balanced, some get by just fine without either. Do you have to have it? You know what they say about opinions and assholes....

Terry
Measuring AC Potential differences between devices (on the case) is also a good idea without transformers. Audiocables disconnected switch phase and neutral in the powerplug (Ground liftet) and use the lower voltage. Mark with a color coded Plug/Outlet. Repeat these steps with all your gear in the chain. If you use only XLR symmetric connections, then the potential difference flow is not affecting the music signal I guess.
I find 35 - 90 AC on the cases (switzerland 230 V AC) and even when one or all devices are grounded there was a difference to hear. Cancelling the AC flow over the audiosignals brings benefit.

Last edited by headroom2000; 11th February 2010 at 12:19 PM.. Reason: more text
Old 16th February 2013
  #9
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ampsarus's Avatar
Quote:
Originally Posted by JustAnotherUser View Post
Why would someone use an isolation transformer for ac power? Under what circumstances would it be essential and what would happen if you didn't use one?

An isolation transformer also lowers the output impedance of the AC line.
Old 18th February 2013
  #10
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Thomas W. Bethe's Avatar
I still carry a TOPAZ ultra isolator when I do live recording gigs in places that have poorly designed or installed lighting systems and it has saved my butt more than once. I got the TOPAZ used for $50.00 at an industrial supply store. The new price was over $1200. Well worth it.
Old 18th February 2013
  #11
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Quote:
Originally Posted by db_dude View Post

Isolation transformers are nice to filter out EMI and harmonics that might be on house power from lighting equipment or other sources that muck up the power source (motors and motor controllers would be other bad offenders, although not as common).
Exactly what I used mine for back at the studio. Unfortunately it wasn't enough. We had the studio right in the middle of an industrial zone and there nothing we could do to cure interferences and noise creeping in on the AC. But the isolation transformer at least brought the differential between neutral and ground back down to "normal" levels (never had a reading of 0V in years).
Old 18th February 2013
  #12
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ampsarus's Avatar
Quote:
Originally Posted by Thomas W. Bethe View Post
I still carry a TOPAZ ultra isolator when I do live recording gigs in places that have poorly designed or installed lighting systems and it has saved my butt more than once. I got the TOPAZ used for $50.00 at an industrial supply store. The new price was over $1200. Well worth it.
I run my amps and everything thru a surplus 5000VA Topaz Ultra isolator as well. I didn't get mine for only $50 though! Nice score!
Old 11th May 2018
  #13
Gear Nut
 

Quote:
Originally Posted by ampsarus View Post
I run my amps and everything thru a surplus 5000VA Topaz Ultra isolator as well. I didn't get mine for only $50 though! Nice score!
Do you run your Topaz at your main power, or inside?

I have 5kva topaz sitting around and don't know what to do with it. I live in an apartment and can't easily make electrical changes with getting the landlord involved. In fact, I don't even know if it works!

I've also heard that higher rated transformers (such as 5kva) can have a very audible mechanical hum, which would definitely defeat the purpose indoors. If it is wired at the main, I am concerned about 2 things - don't know if these are valid or not because I'm not an electrician, just a humble practitioner:

1) leakage power at idle (no load)

2) floating grounds. I'm confused here because I've seen that the topaz secondary can be floated ground or bond the neutral to ground, yet in either case safety ground remains in tact?
Old 12th May 2018
  #14
Every AC powered audio device comes with an isolation transformer, it's called the power supply. If there is no AC sag an extra iso won't do much. Better is to install an AC line filter into each piece. I like Corcom IEC filters, those fit most devices and will remove most of the AC line noise.
Old 13th May 2018
  #15
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Quote:
Originally Posted by ampsarus View Post
An isolation transformer also lowers the output impedance of the AC line.
I'd really like an explanation of how that works.

Unless you're talking about constant voltage (ferro-resonant) transformers, which come with a whole bunch of other problems.

I have used dual conversion UPS units to eliminate power induced noise in systems that couldn't be cured by other means (including isolation transformers). Unfortunately, they also have problems with cost, weight and noise.

Geoff
Old 13th May 2018
  #16
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Hi
The assertion by Ampsarus that an isolation transformer can reduce the AC line impedance is false UNLESS the transformer is bringing the voltage DOWN from as much higher potential.
A transformer taking 220 down to 110 is very unlikely to actually reduce the original line impedance unless it has ridiculously low winding resistance.
Power, when in the cables that are plugged into your gear is already CURRENT balanced even if the Neutral is joined to ground at the fuse/breaker board (where it normally would be). The 'radiation' of 'hum' from power cables is largely a CURRENT balance issue as that is the fundamental parameter behind magnetic coupling.
Capacitive coupling at 50/60 Hz is minimal and as a result the 'interference' that might get into your (properly shielded) audio cabling is minimal.
Decent filtering may be necessary to reduce higher frequency interference getting transferred into audio gear and cables. A dedicated isolation transformer can act as a filter but it is a very expensive and cumbersome way to achieve it and it will ALWAYS increase line impedance unless as I said earlier it is transforming down from a MUCH higher voltage (think 11,000 or whichever your country uses as the step above 120/240 or it's 3 phase parent). A 1:1 isolation will ALWAYS be worse (conservation of energy theory applies).
Dual conversion can be useful if the incoming mains has a lot of 'noise' superimposed on it but the output impedance will likely be a lot HIGHER than the raw supply but it will be very effective at suppressing the line noise.
Ferro resonant transformers will also increase the impedance but as they are effectively a 50/60 Hz pass filter (rejecting all other frequencies) they can reduce 'interference' (anything that isn't 50/60 Hz)..
The power supply section of any piece of gear is designed to tolerate fluctuations in the mains supply within a certain range, usually 10 percent low to 6 percent high of nominal. The regulation circuitry is already coping with an incoming stream of voltage variations so as long as the raw supply never dips below a certain minimum the gear is guaranteed to work to specification.
The incoming mains does not need to be a distortion free sinewave with the caveat that if it is seriously distorted the regulation circuity in your gear might 'drop out' of regulation and that a lot of harmonic content may 'breach' the existing filters.
Unless the mains voltage arriving at your gear falls below the level that the gear's regulation can cope, there is no actual issue with the power line impedance anyway. The fact it may bounce up and down a bit is not actually important, it is an issue dreamed up be people wanting to sell you things by suggesting it is bad.
In fact having a very low incoming supply impedance can increase the initial surge at switch on, stressing mains switches.
Matt S
Old 13th May 2018
  #17
Lives for gear
The BBC was obsessed about not electrocuting musicians or the punters when recording in BBC premises not studios
So the house engineers would always turn up with huge isolating transformers painted bright yellow and insist on their use
Most of our film gear was 12vdc and battery powered
They were a bit like the firemen ,they had to be tolerated, but were clueless
Old 14th May 2018
  #18
Quote:
Originally Posted by Rolo 46 View Post
So the house engineers would always turn up with huge isolating transformers painted bright yellow and insist on their use
Most of our film gear was 12vdc and battery powered
They were a bit like the firemen ,they had to be tolerated, but were clueless
I don't mean to read too much into your description, but for some reason I am envisioning the above as the setting for some sort of long-lost Monty Python sketch.
Old 14th May 2018
  #19
Gear Nut
 

Quote:
Originally Posted by Jim Williams View Post
Every AC powered audio device comes with an isolation transformer, it's called the power supply. If there is no AC sag an extra iso won't do much. Better is to install an AC line filter into each piece. I like Corcom IEC filters, those fit most devices and will remove most of the AC line noise.
I like this idea Jim – I can't seem to find where do buy those filters – do you know of a good place to order from online?

I was only interested in the isolation transformers because I happened to have one – but being 5kva I can't really see a use for it, and it is enormous.


What about the idea of isolating the power sources of digital gear vs analog gear? (by having each, or one on an iso transformer). I never got the purpose of that, since isn't it common to have them interconnected anyway?

(example, laptop is digital, and is interconnected via firewire to audio interface, which then has balanced connections to powered studio monitors)
Old 14th May 2018
  #20
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Quote:
Originally Posted by tygman View Post
I like this idea Jim – I can't seem to find where do buy those filters – do you know of a good place to order from online?
Here in the USA, both Digikey and Mouser stock literally hundreds of different models of Corcom filter products. And I saw over 1000 hits on Ebay when I serched for: Corcom filter There appear to be a great abundance of online vendors of Corcom filters.

But since we don't know where you are on the planet* perhaps your shopping options are different (and unknowable to us).

* You could complete your user profile to at least reveal what country you are in. As you can see some types of questions are quite location-specific.

Quote:
What about the idea of isolating the power sources of digital gear vs analog gear? (by having each, or one on an iso transformer). I never got the purpose of that, since isn't it common to have them interconnected anyway?
In modern times it is getting more difficult to find (and distinguish) purely "digital gear" and "analog gear". Is there some particular problem you are trying to solve? Or is this just free-floating anxiety casting about for another project? Most recording situations would gain much more benefit from acoustical attention. Or perhaps a different microphone.

Quote:
(example, laptop is digital, and is interconnected via firewire to audio interface, which then has balanced connections to powered studio monitors)
Seems dubious. HOWEVER, connecting audio input and output from a computer (ESPECIALLY A PORTABLE/LAPTOP COMPUTER )is frequently a source of difficulty (ground loops, etc). And that interface would be a good place to use an audio isolation solution (like a signal transformer).

Last edited by Richard Crowley; 14th May 2018 at 06:22 AM..
Old 14th May 2018
  #21
Corcoms are everywhere including cheapo surplus sellers like
www.jameco.com
They run around $5 bucks. Do order them in a higher current than the gear draws, the common units are 3 or 6 amps. Larger sized are mounted internally from the IEC connector.

In a fixed facility a large iso mains transformer can quiet down a room if installed correctly. That means it must be mounted further away than the adjacent outside wall. They are best used to isolate the audio AC feeds from air conditioning systems and other stuff. Use one with a center tapped output and then wire the room balanced AC. Run the center tapped ground to a copper rod driven into pre-wetted ground. Then yer Strat won't hum like a banshee. Do use a licensed electrician and follow the local codes and inspections.
Old 14th May 2018
  #22
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Yes for a large iso transformer be sure to locate it FAR (several meters) away. Otherwise your transformer becomes the SOURCE of a large magnetic field that your Strat pickups will love to pick up. So you could easily end up making things worse.
Old 14th May 2018
  #23
Gear Nut
 

thanks Richard, I will get around to doing my profile one of these days. I'm located in NJ.

I am familiar with Mouser and see a lot of those Corcom filter products, but really I don't know exactly what I'm looking for (in regards to the specs of a product I may need). I'm a DIY person but not an electrical engineer!

The issue I've always had is that I have a noisy monitors. I'm using a new pair and still have the noise problem. I also have a hum - but that's a new (and separate) issue, and started when I added the A/C unit to the system (doesn't need to be on to cause hum, just plugged in).


My situation is less than ideal – we live in an apartment in an old building. I have one 15A circuit that powers the whole apartment (I may be able to get this upgraded to 20A). The outlet the fridge is on in the kitchen has no ground wire to the outlet – lights flicker and speakers crackle every time compressor kicks in; however, this could be a faulty part in the fridge and have nothing to do with lack of ground.


Despite this I've been able to get some nice recordings done, but I would love to have less noise – it sort of doesn't get to you until you hear what's its like without it. That's when I got into reading about isolation transformers and what not.


Regarding the digital vs analog, I was asking because I've read about digital items such as a computer injecting DC noise back into the system – forgive me if I don't know what I'm talking about here. I can be humbled very easily when it comes to electrical discussions.


I'm all for whatever will help me get a cleaner, less noisy idle sound, without getting into esoteric discussions about silver vs copper.
Old 14th May 2018
  #24
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Hi
Having a proper ground on ALL gear, audio and domestic appliances would be a good start and might even solve all the problems.
If having a proper earth on everything doesn't clear it, put filters on the gear that CREATES the noise, such as fridge or aircon. the contact sparks from the thermostats create a small radio frequency (wideband) splat that can radiate through the air to your mic cables etc as well as by direct coupling by the wiring so you need to stop the 'spark' noise from getting OUT in the first place. Modern appliances should have suppressors fitted anyway but if they are not grounded and should be they will radiate. Another 'plus' of having the fridge etc grounded is that there is less chance of getting electrocuted if it develops a fault!
Matt S
Old 15th May 2018
  #25
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Richard Crowley's Avatar
 

Quote:
Originally Posted by tygman View Post
I...see a lot of those Corcom filter products, but really I don't know exactly what I'm looking for (in regards to the specs of a product I may need).
There are many different products because it depends on what you are installing it in. There is no simple universal solution.

Quote:
The issue I've always had is that I have a noisy monitors. I'm using a new pair and still have the noise problem.
Without knowing what kind of "noise" this is we can't really offer any useful suggestions. The problem may or may not be affected by a power line filter (or a power iso transformer, or balanced power, for that matter.

Quote:
I also have a hum - but that's a new (and separate) issue, and started when I added the A/C unit to the system (doesn't need to be on to cause hum, just plugged in).

My situation is less than ideal – we live in an apartment in an old building. I have one 15A circuit that powers the whole apartment (I may be able to get this upgraded to 20A). The outlet the fridge is on in the kitchen has no ground wire to the outlet – lights flicker and speakers crackle every time compressor kicks in; however, this could be a faulty part in the fridge and have nothing to do with lack of ground.
Your symptoms indicate that you have very significant power issues, quite possibly issues that threaten life and property. Hope you have good renter's insurance including fire coverage.

Quote:
I'm all for whatever will help me get a cleaner, less noisy idle sound,
You have rather severe mains power issues which would seem to be a much larger concern than the noise level of your recordings.
Old 15th May 2018
  #26
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Quote:
Originally Posted by tygman View Post

My situation is less than ideal
Really, what Richard said. Be careful and don't get electrocuted! I used to live in an apartment in NYC that was just like you described. 110v from the fridge to the kitchen faucet. Could never get the landlord to look at it, but this was in the 70's before every one knew how to sue.

D.

Oh, and before I knew that I could file down the fridge plug and turn it around and mitigate the danger
Old 16th May 2018
  #27
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Hi
Fitting filters on gear is a good idea but they must have an ground connection to be effective.
As I said previously, ground everything that should have a ground, ALL appliances and any audio gear that has ground pins on plugs.
As a note, the filters fitted to many pieces of gear (and household appliances) use capacitors which are wired to 'shunt' noise into the ground pin. If the ground pin is not actually connected to ground it is possible to get approximately HALF of the mains voltage (55 or 120) on the ground pin and chassis of the gear. This is at a very high impedance and is deemed safe as it is such a low current, typically 0.2 milliamps. You would just feel a slight 'fuzziness' if you stroke the metal casing of gear with your fingertips.
The chance of electrocution from properly grounded gear and building is minimal.
Matt S
Old 16th May 2018
  #28
That NYC building sounds like a 3rd world blockhouse. Report the unsafe electrical system to the authorities. Fires are bad for repeat business.
Old 7th July 2018
  #29
Very interesting discussion about having "clean power" to your studio gear...

Does an EMF/EMI filter like the STETZERiZER filter or other could have an impact in a studio environment on sound?

Cheers,
Old 7th July 2018
  #30
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Richard Crowley's Avatar
 

Quote:
Originally Posted by Ntchi View Post
VDoes an EMF/EMI filter like the STETZERiZER filter or other could have an impact in a studio environment on sound?
Maybe. Does this studio environment have an audible RFI noise problem?
If not, then why would you need a filter?

Furthermore, do a search on "stetzerizer filter hoax". They look like your typical consumer hype overpriced plastic toys. If you really have an RFI problem, little plug-in plastic gadgets probably aren't going to get the job done.

If you have a "dirty power" problem you would know about it. And little plastic toys are probably not the solution.
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