Okay... THIS IS A MONSTER!!!! IN THREE PARTS
Here is a topical thread... one of several... from the recpit. I pulled it out and gave it a light edit to present here. I'll do a more through review, boil out some of the repetition and condense this into an article... MAYBE (because time is a limited commodity in my life as it is with most of you I am sure).
As with all my posts… the things I suggest are grounded on simple practical empirical experience backed with as much real physics and technical grounding as I can muster. Now – the world is not perfect. Everything in my experience will follow the “laws” of physics but theory and practice do not always line right up… why? Because in practice there are lots of variables, things that are coming in from outside your theoretical model that you are trying to apply in a real world implementation… for example… it is really REALLY difficult to avoid all ground loops in a real world studio system – my solution is minimize them and make all the ground connections – including remaining loops as solid, as low impedance and as small in cross sectional area as practical. Another item… there is no perfect ground… there is no wire we can lay our under funded hands on that is superconducting at room temperature. So… we have to avoid the use of ground as a landfill for noise, stray line current leakage from partially blown MOV’s in surge protectors that protect one time and then, often, leak to ground, audio currents driven to ground when active balance outputs are connected to unbalanced inputs (transformers on outputs or made available on patch as needed are a good thing in my book)… and so on… all this can be discussed in this R/E/P forum as time goes by.
Give this a read - it may not have a damned thing to do with your particular noise, power, ground problem but as power will certainly come up... this does cover a lot, it will answer someone's questions and inspire many more… and may cause some debate, which, if kept civil and to the point, are fine. Find two techs who agree on everything and you have found an anomaly.
NOTE: the following is centered around permanent installed power systems for music and post studios. Portable Road systems have other sets of issues and I don't deal with those day to day.
NOTE: IMPORTANT – POWER SYSTEMS HAVE VOLTAGES THAT CAN REALLY HURT OR KILL YOU SO TAKE ALL OF THIS AS INFORMATIONAL – THE FOLLOWING INFORMATION WILL NOT MAKE YOU QUALIFIED TO DO ALL THIS YOURSELF… YOU MUST PROCEED WITH AT YOUR OWN RISK AND WITH EVERY REASONABLE PRECAUTION TO PROTECT YOURSELF AND KEEP YOUR SYSTEMS SAFE… HIRE A LICENSED ELECTRICIAN IF YOU CAN AFFORD TO DO SO.
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shelton
Here Often
Post subject: Studio Electrical System Questions
I recently came upon your article in Mix magazine about studio electrical systems. In it you recomend running the system off batteries and then through an isolation transformer. Can you provide me with a link to a manufacturer of this type of battery system? The only kind I can find are APC UPS types.
Thanks,
Shelton
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klett
Has No Life
Post subject: Studio Electrical System Questions
Actually, this unit is an Uninterruptible Power Supply (UPS). There are different kinds and many manufacturers. What you want ideally is one that is always "on line" and does not actually switch into a standby mode
so you do an "and" search on Google with these words
double conversion UPS single phase KVA
Double conversion UPS systems are always online so there is no changeover - you run on the regulated and controlled UPS output at all times instead of only when power fails.
Double conversion means it is converting to dc and converting back to AC simultaneously
Here are links
http://www.stacoenergy.com/singlephase.htmlhttp://www.engineeringdynamics.com/single_phase_ups.htmmaybe this link will work for MGE
http://www.mgeups.com/products/pdt120/1ph/cometex/help/resul t.php
If you are in an area where 3 phase “208Y” service is the norm you can do a three phase UPS and distribution (which works just fine in larger studios if don’t correctly and I can expand on that elsewhere) OR you can have a single phase UPS set to take 208VAC on the input and output 120VAC or 240VAC on the output. When you do an install where the UPS is doing a phase and/or voltage conversion (from two 117VAC hot legs spread 120 degrees apart to two 115 to 120VAC hot legs 180 degrees apart (or single phase 120VAC, or balanced power with two 60VAC hot legs 180 degrees apart) you can’t bypass the UPS unless it’s with a transformer… that takes us elsewhere so…
and... by the way... someone was asking about transformer (autotransformer actually) lighting dimmers…
http://www.stacoenergy.com/variable_transformers.htm#Panel%2 0Mount
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Klett
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speers
Should Get Out More
Post subject: Studio Electrical System Questions
One clarification:
I looked at a few of the double-conversion units. None actually run off the batteries [as the article stated incorrectly] . If they did, battery life would be drastically shortened. They use large capacitors, with the batteries used only for outages, as with "simpler" UPS's.
This is still, as John says, always converting to DC then back to AC, but the "battery" thing is misleading.
Perhaps there IS a model that actually uses the batteries all the time, but I haven't seen one. I would think that the capacitor thang achieves the same isolation and cleanliness.
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klett
Has No Life
Post subject: Studio Electrical System Questions
I always run the risk of oversimplifying or jamming out too much information - so...
In double conversion supplies you are not really running off the batteries all the time - the batteries are being held at full charge until needed... ...AC power comes in to UPS - gets turned to high voltage DC, filtered like a mofo (big caps), used to charge the batteries AND feed an inverter which takes it back to AC at your selected line voltage and frequency. If the UPS does not get enough power at it's input to hold up the output then the batteries drain into the inverter and keep you going. THAT is also an oversimplification... but no matter how you describe it the desirable UPS is one that is always “on line” and does not need to "change over". Thus you want an “on-line double conversion UPS”.
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Klett
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thedug
Should Get Out More
Post subject: Power
Doest the UPS have any effect on the "quality" of the line?
I always thought of a UPS as more of insurance to avoid intermittency.
How does this compare to ... balanced power?
Thanks.
d./
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klett
Has No Life
Post subject: Power
thedug: "Doest the UPS have any effect on the "quality" of the line?"
Not the incoming line but on the output that your equipment sees you get controlled and regulated power. You really should view a UPS as we are applying it and a power and voltage regulator with the added feature of a battery back up that buy’s you time to save your files/projects and shut down everything in an orderly manor. One badly timed blackout or line fluctuation can cost you more than a UPS will so it does pay for itself – It’s not really a luxury.
NOTE - you do need the look at the incoming power/neutral/ground because, as with most things, you should start with the foundation and build up from there... if your service and technical grounds blow you can only get so far. Those really come before the UPS.
The UPS holds the line at a constant voltage with a reasonably (for power) low distortion sine wave. When you have brown outs and other off-voltage conditions the bias in just about ALL your tube gear will change... so guitar amps will sound good one day and not the next because of line voltage changes (Joe Perry powers his back line off a large UPS for this reason). In low voltage situations pre-regulation supply voltages drop so filtering and regulation in solid state gear can be degraded... etc. you want stable supply voltage to your gear.
In some older and stressed out parts of the NYC power distribution we see incoming line voltage running down to 95 volts on a hot day when ALL the air conditioners are going full blast and then pop up to 130 volts at night when it cools down and offices clear out. It helps... assuming you buy a decent, properly-sized, UPS of the right type. I talked about that in some detail in the article.
HERE is some sort of fun thing... if you have an enviable budget...
This is a "carrying it all the way through" power system - more than 95% of people are willing to do.
If...if... if a client demands solid and consistent power in a big SSL/Neve Vseries kind of studio and they want to stay up seamlessly 24/7 even if there is a severe ice storm and some guy spins off the road and knocks down a pole a mile down the road that carries the power feed to your place... and it takes five days for the utility to get out to you to fix it.... ...like that.
block description...
INCOMING LINE TO METER - prefer 240VAC single phase 200A (min) service which will be the assumed for this list... suburbs. Three phase systems are nearly the same but there are some other things to look for that we can get in to...
MAIN SERVICE CUTOFF
MASTER BREAKER/RELAY/CONTACTOR - has a trip control input
OVER-VOLTAGE CLAMPING – giant MOV’s that will trip the main breaker if you get a big transient
MASTER GROUND STAKES – a whole topic on it’s own
CHANGEOVER FOR GENERATOR (automatic once up to speed) – An MG set of some sort feeds this – there are “on line” versions of those too that I can tell you about.
MAIN HOUSE PANEL – feeds all convenience outlets, lights, air conditional… everything not within your studio systems
Here is where house power and tech power part company
TECH BREAKER - single 2 pole breaker with alarm contacts to kill power in the event of a fire
LINE CONDITIONING / FILTERING ahead of UPS – optional – helps protect UPS
UPS - Double Conversion On Line 18-25KVA 30mins @12-15KVA load with hard bypass switch for servicing (see note above about bypass)
K-20 (high K factor or primary to secondary isolation)ISOLATION TRANSFORMER - typ 15-18KVA
208VAC/60Hz or 240VAC/60Hz primary: primary is where dirty "mechanical" ground stops
230 single phase split 115/115 secondary (which is balanced 230VAC and what most suburban house get off the pole): secondary is where clean isolated ground starts
MAIN TECH PANEL - single and 2 pole breakers
Large items like consoles, workstation racks, big analog machines and other stuff that does not move much... large power amps... they all get what is effectively balanced 230VAC via twist-lock outlets.
Outboard gear and small format machines get unbalanced 120VAC. Outboard gear racks don't draw a lot so they are 120VAC with 0V neutral… load the two sides of the 230 volts equally.
Optional – on some installs we’ve added some European style 220(230)VAC outlets on producer desk/racks in control rooms – this is balanced power and some Euro gear won’t like is (most will). Contrary to what some people think – 220 is not balanced in most of Europe – not that I have seen. I’ve done power systems there. Anyway – some of those English stove plug strips (with fuses on both neutral and hot if there are fuses at all – those are often inside the plug) and round pin Euro outlet strips are cool to have if someone comes in with a Bel delay they just brought over and have not converted.
Optional - on two installs we added an EquiTech Wall mount system fed from a two-pole breaker in Main Tech Panel and distributed balanced 120 as well...
I won't go in to the grounding details because that has been or will be covered in other topics I’ll bring forward from the ‘pit
thedug: "I always thought of a UPS as more of insurance to avoid intermittence How does this compare to ... balanced power?"
120VAC (60/60) Balanced Power is not a big increment up from a well-done unbalanced power distribution. It can sometimes be more trouble than it’s worth… you have to make accommodations for gear that hates balanced power and once you connected, say a guitar amp to the standard power before your EquiTech (or whatever) you have blown your isolation. This is why end up with the two transformer in the over the top illustration above.
Anyway… There are certainly positive aspects. Balanced Power is not a bad thing. It’s just not a panacea. In addition, it does not fix incoming line problems. I have not seen an off the shelf ferro-resonant isolation transformer that does 120 split 60/60 on the secondary (these transformers self regulate output voltage within a narrow range).
This whole approach I just went through evolved out of the need to keep sessions from loosing a data if power drops. You have to figure that in a 9K with Recall and Ultimation (or Neve V88R w Encore - whatever) studio there is a lot of info that could be lost if the timing sucks... and the ProTools system... ANY computer or workstation, and all the other stuff that needs to save before shutting off... There is a lot of potential for data loss and more coming all the time.
Once you look at backing up your CONSOLE you may as well go the whole nine yards and do the whole thing... better anyway from a distribution point of view...
Ho-Kay?
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Klett
www.technicalaudio.com/techmecca/ ------------------------------------------------------------ ---------next post
thedug
Should Get Out More
Post subject: Small Install
I am currently converting my garage to a control room. I don't have the money to do all these big things.
But I would love input on the inexpensive things I can do to avoid costing a lot later to upgrade.
For instance, If I have want to run balanced power I should prolly get the outlets that don't connect neural to ground.
I am thinking that I'll install those outlets and run each one straight back to the panel so I can star ground them.
Any tips? Any things I can't live without?
Thanks,
d./
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End of part one of three – go to next R/E/P post…………