Balanced Power and Isolation Transformers

[critterkllr]

Hey guys,

I was hoping for some help on this. I posted this on gearslutz and received misinformation along with a bunch of arrogance and "I've answered this before and I won't again" type of bullshit. I don't know why I ever post stuff like this on other forums. If there is any other info you'd need from me to help, please let me know what I'd need to post.

My work is unloading a bunch of medical grade isolation transformers and balanced power supplies. I can grab whatever I want, so I was wondering what would be of good use to me. I have a small studio with a console, around 12 outboard rack units, 6 guitar amps and a few synths.

I don't have any specific noise problems that are out of the ordinary. Since these are free, I'd like to follow a "best practice" to keep out any possible noise and to decrease the noise floor.

I have access to the following:

1 x Tripp Lite IS1800HG: http://www.mouser.com/ds/2/411/IS1800HG-36370.pdf
10 x Torroid IsoBox ISB 300VA: https://toroid.com/Home/Product-Details/ProductID/1
2 x Torroid 1500VA Balanced Transformer: https://toroid.com/Home/Product-Details/ProductID/33

If I am using the balanced transformers, would a isolation transformer do any good at all?
Would I keep everything in the recording chain plugged in to one balanced transformer? Or would I use the two separately?
Would the digital equipment (computer, monitor, etc) get an isolation transformer? If so, should it go straight to the wall or from the isolation transformer into the balanced power? I don't have a UPS for the computer.
This is also a rehearsal space where stereo guitar rigs are used. Should each rig get an isolation transformer?

I've read quite a bit on this, but I am just more confused than before I started. Everything is about having one big balanced power transformer.

 

[JohnRoberts]

I'll try not to be too snarky...    ;D

If I lucked into a free pile of these, I'd probably try to sell them to audio-phools who value them more than I do.

There is some merit to the concept of replacing one 120VAC line  and 0V (neutral) return pair, with a pair of 60V opposite polarity lines.  In theory there will be less electrostatic energy to couple into nearby wiring first because of the lower voltage, and second there will be a first order cancellation of the two opposite polarity voltages (especially if wiring is twisted pair). The current and magnetic fields may be similar.

If you don't have a noise problem I'm inclined to ask why bother..? Especially if you can convert these to cash.

It might make sense for a studio room tracking open coil guitar pick-ups that are pretty sensitive to hum (but I suspect those are more magnetic than electrostatic) .

One thing I am not sure about is safety ground bonding for correct breaker panel fuse tripping. I would be tempted to add GFCI outlets to the output side of these transformers, that way any leakage fault more than 5 mA will open up the power.  Check with electrical code for proper wiring practices.

JR

PS: Note- very old school guitar amps with stinger caps to ground chassis to neutral, will no longer have a relatively quiet 0V neutral to ground the chassis to. Just as well since those old amps need to be properly grounded.

 

[critterkllr]

Thanks John,

I guess I should have added "that I'm aware of" to my statement about not having any obvious noise problems. Truth is, I'm not sure what the noise floor in my studio is versus what it should/could be. These suckers are so heavy to ship and package that my first inclination was to just see if they're of any use. I would definitely rather have money from them to put towards other gear though!

I have read "Build It Like The Pros" by Rod Gervais and he mentions using medical grade transformer isolation. So, I assumed there was some legitimacy.

 

[JohnRoberts]

If we go back a few decades, studio equipment designers were not up to speed about proper handling of pin 1 problem. When shield noise currents are safely dumped to chassis ground, and audio signals handled differentially, interface noise is well managed. But it wasn't always, so balanced power was a brute force solution to quiet down a studio full of legacy gear with questionable I/O design, for cost-no- object studios.

Modern properly designed professional (balanced  I/O) gear should not benefit much if at all from such expensive remedies.

JR

PS: Yes I suspect shipping cost would be prohibitive.

 

[PRR]

> Check with electrical code for proper wiring practices.

The Michigan (US NEC) code does not really contemplate balanced 120v feeds.

IIRC, some exemptions have been granted for specialized audio. I do not know of a Code, this may be case-by-case by the local Authority.

At a different level, I've looked into deriving a 120V-to-common feed from the 240VCT wires (to reduce lamp-dim when the 120V pump kicks in). This really needs a 2-winding ("separately derived") transformer, not a center-tap job. Otherwise Neutral and Ground stray and fault currents just do not go well.

 

[Spiritworks]

NEC Article 647 "Sensitive Electronic Equipment" covers use of a balanced transformer to provide " separately derived systems" voltage.
Most audio related wiring covered by the NEC is in Article 640.
Complete Chapter 6 is titled " Special Equipment"

 

[dfuruta]

I would keep a few of the transformers for use on the bench and sell the rest - good money, there!  Shipping those isn't bad;  just double box 'em and use plenty of bubble wrap.

In my experience the noise floor in a home studio is going to be determined by acoustic noise, not electrical.

 

[sodderboy]

You have a smallish setup so there is not much chance of issues that prompt balanced power.
If you were in a commercial building, elevator building, or industrial estate the IS1800 would give you isolation from the hash created by large motors and machines. 
If you had a synth setup larger than 24 outs then I would recommend balanced power.  Same with a console-less DAW based setup with more than 3 patch bays worth of connections.  When you have power, audio, AND data connections between more than 12 devices, or more than 100-ish I/O without a large metal chassis console(one that you cannot push an inch by yourself), then system noise will be a problem.

All the boxes up for grabs (except for the smaller toroids) have their applications in a recording studio, but it does not look like it is yours.

 

[alexc]

I've wanted to try balanced power transformer stuff in my place - I am rural and the mains supply has these 'tics' 2Hz or so which become noticable at strong gain levels .. like +60dB and beyond or so, superimposed on my anaglog channel strips.

I managed to capture them on my old analog storage cro but it took a while
A short duration pulse train (four or five clicks) with a decaying envelope : here a while, gone  a while etc.

Didn't happen in the bug city - I was accustomed to well high gains applied to guitars and never noticed it.
Same gear moved to the country side - an unwelcome addition.

Although the usual things of good grounding, shielding I've applied, I do seem to find the 'tic - tic' creeping in on compressor-eq-limited-gained tracks. I've eliminated obvious sources of noise by successive 'offing' of all the other equipment in the place.

No change. Anyway - I wanted to experiment with some power isolation transformering. But haven;t yet.

I have a central ground spike for the whole place (a smallish house) as well as up-to-code electrical wiring.

And a 'tic-tic'. I've learn't that it's my ulitmate noise floor - some -74dBu  or so.  A few uV of hash with this tic-tic when gain creeps just over some (imagined) threshold.

It's *not* 'audio weirdness syndrome'. It's an actual thing!

 

[alexc]

It's also interesting a 'lead in' to considerations of power conversion and storage systems for audio

ie. some solar cells, modern power electronics converters and good batteries along with an on/off 'grid' switch

Sort of a 'Les Stroud' style of recording studio!

Would the noise floor get worse (probably) or better (doubtful).

Hopefully one day I'll try it and see (hear) for myself.

 

[Speedskater]

'alexe' I would enlist the aid of a Ham (amateur radio operator) to find the noise source.
But first check your building.
Turn of all the circuit breakers but the one for your audio system.
Check all the CFL bulbs.  A burnt-out bulb can make nasty noises.
The door-bell transformer.  It may be hard to find the transformer, but this is the kind of noise that they make.
Get a battery powered AM radio. Tune it off station at the low end of the band.  Listen for noise all through your building and outside near the power lines  for as far as you can.

 

[sodderboy]

I think isolation is your best first step rather than balancing.  With a tick on the electrics, just like a noisy, clocking, unbalanced synth output- if you then balance it with iron or Si you will still have the tick.  An isolation transformer serves to give you a "fresh neutral" that is not connected to the source.  If there is some cow fence PSU throwing a tick back into the supply, a balancing transformer will not do anything.  Balanced power deals with YOUR mess, and most studios are not a mess.  It's when you get into big I/O DAW based, huge synth setup, multiple PC or programming stations, multi-room (but small equipment count) facilities that want to patch their assets between rooms, etc. type situations that balanced power is tech "glue".
Mike

 

[moamps]

.....If you were in a commercial building, elevator building, or industrial estate the IS1800 would give you isolation from the hash created by large motors and machines.  If you had a synth setup larger than 24 outs then I would recommend balanced power.  Same with a console-less DAW based setup with more than 3 patch bays worth of connections.  When you have power, audio, AND data connections between more than 12 devices, or more than 100-ish I/O without a large metal chassis console(one that you cannot push an inch by yourself), then system noise will be a problem.

Same here.

The isolation transformers are useful tools, as Di-boxes. Especially  if you are changing your setup often or you do field recording or OB like me.

The smaller transformers are ideal for solving ground loop problems created on one or two devices with lot of outputs (imagine a violin hooked to a preamp, several pedals, laptop and 8 channel external audio card) where you are short in DI-boxes or you simply don't like the sound of your DI-box for a particular source.

The balanced power is just add-on to the IS based power system with some safety issues (which can be solved easily).

IMHO, the optimal small recording studio should be equipped with one or two big (balanced) IS (with electrostatic shied between primary and secondary windings)  for the control room and few smaller for studios, carefully designed and wired audio and safety grounds wise.