KVR Audio

AndrewSimon · Post by **AndrewSimon** » Wed Jun 29, 2005 9:27 pm

Hi

Balanced AC Power Filters, anybody using them?
Opinions? recommendations?

I found two that look good to me but way out of my price range
http://www.b-p-t.com
and the industry standard (or so I'm told)
http://www.furmansound.com/products/pro ... anced1.php

My objective is to cut down the "already very low noise" that enters my mic preamp through the ac line.
My biggest noise polluters are dimmers, energy saving light bulbs and TV's and computer monitors.

funkynuts · Post by **funkynuts** » Wed Jun 29, 2005 9:58 pm

A line conditioner would probably suit your needs better.It will filter the electro magnetic radiation interference like radio frequencies etc.from your mains in addition to supplying a constant voltage free from surges or dips.
This should improve your noise floor and generally result in a slightly clearer monitoring enviroment in addition to protecting your equipment from damage in the event of power surges.

AndrewSimon · Post by **AndrewSimon** » Thu Jun 30, 2005 5:17 am

funkynuts wrote:A line conditioner would probably suit your needs better.It will filter the electro magnetic radiation interference like radio frequencies etc.from your mains in addition to supplying a constant voltage free from surges or dips.
This should improve your noise floor and generally result in a slightly clearer monitoring enviroment in addition to protecting your equipment from damage in the event of power surges.

No I am talking about something much better here.
Balanced AC power is a great idea to eliminate power introduced noise (hum,buzz, hiss and most other interferences)
You do not need to "filter" EMR and RF, you can completely eliminate them

It works similar to balanced audio cables.
The 120V goes through an isolations transformer with a center tap.
The center tap is then shorted to ground.
This creates a "balanced power", instead of a "hot" 120V lead and a neutral "0v" lead you now have two 60 Volt leads wired out of phase with each other.
Any noise that is introduced on the electrical grid will now be out of phase and will cancel each other (genius idea)
Every studio should have one of these.
I found a place with down to earth prices.
I think a 500VA or maybe a 1KVA will be more then enough for my needs.

Anybody interested look into:
http://www.toroid.com/standard_transfor ... ormers.htm

I will report results when I will receive it.

C00kie · Post by **C00kie** » Thu Jun 30, 2005 7:03 am

Right, so you get +60, 0 and -60. How do you connect that to something expecting merely 9 or 12V, without losing the balance?

AndrewSimon · Post by **AndrewSimon** » Thu Jun 30, 2005 7:43 am

C00kie wrote:Right, so you get +60, 0 and -60. How do you connect that to something expecting merely 9 or 12V, without losing the balance?

No, we are talking 120Volt AC here not DC.
You basically put a buffer between your studio and the electrical grid.
You create your own power outlets.
Every equipment in the studio (including your 9V and 12V AC adapter) will have to be connected to "your balanced outlets"
This will ensure that no noise can come in from the outside.

Anyway here is how Furman is describing it:
It makes perfect sense to me (I used to be a TV repair tech for many years)

In much the same way that balanced audio lines can reduce the pickup of hum and other types of electromagnetic interference (EMI), the use of balanced AC power lines in sensitive audio, video, or computer installations can make an enormous difference in system noise. But power distribution in North America, unfortunately, is not balanced. The distribution standards currently in use were derived from practices established over a century ago, when electric power use was limited to lighting and motors-long before any EMI-sensitive applications existed. The emphasis then was on convenience (from the power utilities' standpoint) and safety, but not noise cancellation. The result was a three-wire distribution scheme in which 120V branch circuits have a hot wire and a neutral wire, with the neutral tied to a third wire connected for safety to an earth ground. The third wire does not carry any current unless there is a short circuit. This unbalanced scheme causes hum in audio circuits for two main reasons. First, the current flowing in the hot wire induces hum in any other nearby wires, which may carry vulnerable low-level audio signals. Second, because the impedance of chassis and cable shielding to ground is greater than zero, ground current flowing from power supply capacitors and from EMI pickup causes a voltage drop at 60 Hz and its harmonics which is added to the audio signals.

With a center-tapped isolation transformer, the AC power feeding a studio can be balanced at its source. The current-carrying wires then are no longer "hot" (120V) and "neutral" (0V), but two 60V lines of opposite polarity (referenced to the safety ground connected to the center tap), whose difference is 120V. This type of power, when run around a room, does not induce hum into nearby audio wiring, because the two conductors induce equal and opposite voltages that cancel each other out. Similarly, ground currents are all but eliminated by the same common-mode cancellation effect. No longer is it necessary to adopt cumbersome and expensive star-ground systems or use massive bus bars or heavy ground rods. All such systems are doomed to yield only mediocre results because of the impossibility of reducing the ground impedance all the way to zero. The common-mode rejection of a truly balanced AC supply is far simpler, cheaper, and more effective.

Balanced power is a technology whose time has come. Balanced power is recognized by the National Electrical Code (Article 530) for technical power applications. Its use is restricted to electronic equipment only. Balanced power may not be used for lighting equipment, and access must be restricted to use by qualified personnel only.

C00kie · Post by **C00kie** » Thu Jun 30, 2005 10:44 pm

It reminds me a bit of a filter full of chrystals my sister bought to get rid of an overload of calcium in her water (yep, THAT kind of filter.)

At first it bought her piece of mind. The water was unaffected, and the stones in her boiler kept growing nevertheless. Finally the filter exploded, which was rather messy.

Maybe it works, but my setup is totally free of 50Hz hum. So with good equipment you do not need it for sure.

AndrewSimon · Post by **AndrewSimon** » Fri Jul 01, 2005 2:44 am

C00kie wrote:It reminds me a bit of a filter full of chrystals my sister bought to get rid of an overload of calcium in her water (yep, THAT kind of filter.)

At first it bought her piece of mind. The water was unaffected, and the stones in her boiler kept growing nevertheless. Finally the filter exploded, which was rather messy.

Maybe it works, but my setup is totally free of 50Hz hum. So with good equipment you do not need it for sure.

Unless you use sesitive microphones or guitars you probably do not need this, but if you do, it can definately help.
If you have tube amplifiers they also pick up all kind of stuff.
It is also possible that the electric grid is much better in Holland, but at my house if somebody turns on the lights in the other room I can hear it in the speakers. (not very loud but it's there and I can measure it, it's in the -68 dB level)

Anyway I ordered the 1KVA transformer $190.
I will report on the results.

Neelix · Post by **Neelix** » Tue Oct 25, 2005 7:40 pm

Wanted to give this thread a little bump as I think it's important! I just called these guys and they were very friendly and helpful. These balancing transformers were designed with AV applications in mind, and the prices are stupid cheap (less than 300.00 for the 2000 VA model, just over 200.00 for the 1000 VA model). I'll be ordering mine tomorrow. Thanks to whoever originally posted the link to these guys!

http://www.toroid.com/standard_transfor ... ormers.htm

Lunch Money · Post by **Lunch Money** » Wed Oct 26, 2005 2:32 am

I've been interested in either balanced power or line conditioning lately, too. I'd love to hear about anyone's experiences with either. Since I'm not a top-of-the-line studio, I don't mind the simpler 'conditioning' solution if the results are at least reasonable without destroying my guitar's tone.

Greg

Neelix · Post by **Neelix** » Thu Oct 27, 2005 1:55 pm

With regard to my previous post about toroid.com - be careful with these guys! I specifically asked for quotes in the models in the enclosures, and what I posted above is what they gave me. A friend of mine called them yesterday and talked to them at length, and there was no question he was getting the enclosed model when he ordered. He paid, they shipped, and he just found out they quoted him the raw transformer version, and that that enclosed version was about twice the price. They're trying to hit him up for a 15% restocking fee, but the way I see it, he could do a chargeback for misrepresentation because they're the ones that screwed up by not listening to their customer! Anyway, looks like their prices aren't that great after all, as you can get a pretty slick looking unit for about the same price (and with the same transformer)... Se La Vi!

Neelix · Post by **Neelix** » Thu Oct 27, 2005 2:23 pm

Ok, in their defense, they ultimately did agree to wave the 15% restocking fee. Still, if you order from them, make sure you know what you're getting and get the right price!

madbaron · Post by **madbaron** » Mon Feb 13, 2006 3:06 am

Results anyone?

AndrewSimon · Post by **AndrewSimon** » Mon Feb 13, 2006 3:55 am

Well I got it.
It helps.
Just as I thought it creates a buffer between anything connected to it and the outside world.
Make sure to connect all your studio equipment to it.
Outside noise like buzz from dimmers in the other room is completely eliminated.
It does NOT eliminate noise that is picked up inside your studio.
For example RF noise that is picked up by guitar pickups when you stand close to the computer monitor.
But even with that it helps a little bit.
Since all your AC wires in the studio now carry 60Vac (not 120Vac) hum that comes from mic cables close to AC lines is reduced.

All in all I am happy with it.
It's not a magic bullet and it is relatively expensive but it definately works 100% for some problems and it helps with the others.

There is no other solution out there, that really works.

I am now taking the next step.
I purchased a tube mic preamp with built in DA converter and optical Toslink outputs.
I connect the guitar to the preamp and from there I go via fiber optic to the sound card.
HOW IS THAT FOR ELIMINATING GROUND LOOPS?

I also ripped the power supply out of the mic preamp and put it in a seperate box so no low signal and AC lines share the same space.

And for the ultimate challenge......
Not sure I will do this, but if I can make the mic pre work on batteries only it should be perfect.
The problem is that I will need several motorcycle batteries and some kind of charging system that will charge them every night.
It's quite some work but I have seen it done with great results.

By the way anybody remembers Mission? the Canadian audiophile amplifiers?
In the 70's they had a very nice preamp and amp where the preamp was working on two motorcycle batteries.
When the power was OFF the batteries were charging, when you turn ON the preamp a relay completely disconnects the AC power and the preamp works of the batteries.

Lunch Money · Post by **Lunch Money** » Mon Feb 13, 2006 6:38 am

Thanks for the report!

I hate my apartment...

madbaron · Post by **madbaron** » Tue Feb 14, 2006 2:20 am

Prices look pretty good. The BT-X is the transformer and the BT-E is the enclosed.

BT 0250E 378.00
BT 0250X 177.96

BT 0500E 394.00
BT 0500X 180.84

BT 1000E 472.00
BT 1000X 223.89

BT 1500E 514.00
BT 1500X 243.06

BT 2000E 775.00
BT 2000X 270.80