Dedicated Lines - Sub panel or no?

I use a subpanel but my requirements are unique.

I have 3 amplifiers (2400W combined) for stereo. Much of that in class A.

I supply a large step-down transformer with 240V for balanced AC output for 2 of the amps.

A TVC line stage provides galvanic isolation between the CDP and amps. There can be different voltage between legs which can cause noise but that has not been an issue in my case.

I have the subpanel/transformer located in a closet directly behind the equipment.

The origional main panel is obsolete and breakers are no longer available.

I was able to run 6/3 wire through the crawlspace.

I rent.

No clue about electrical requirements in Singapore but check this out. Surge protection, regulation, isolation and breakers included.

http://cgi.ebay.com/Topaz-7-5-kVA-Power-Conditioner-Isolation-Transformer_W0QQitemZ330314111193QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item330314111193&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A10%7C39%3A1%7C240%3A1318

Hevac1: Did the xformer make a lot of noise and heat?

When I moved, I had mine hooked up to 120V just as I had before but it made noise and heat. It was getting saturated. Rewired for 240V and it's dead quiet and only slightly warm, like before the move. Efficiency is over 95%. Transformers can be picky.

The only group 4 (50Hz) Sola HD on EBay.

http://cgi.ebay.com/EGS-Sola-Constant-Voltage-Power-Conditioner-63-23-775-8_W0QQitemZ400038861928QQcmdZViewItemQQptZLH

Way over your needs, even if you went to balanced AC output. 480 lbs!

Hevac1,

Similar to mine, except I have a 5KVA 480/240-240/120. Wired 240V to 480V input and X1, X4 is +/- 60V with X2/X3 connected ("optionally" to neutral).

Just tested with analog clamp-on and I got 3.5A (average)per 240V leg and 7.5A on the outlets (93%). Unloaded, it was 1.5A on the 240V side, which was higher than I expected. Analog meter is not precise.

Wiring 120V to the 240V inputs proved inconsistent. We are going beyond the design and rating but it seems to help to stay as close as possible. I'm also using a GFCI on the balanced outlet, for safety.

For more fun, I got lower amp draw, compared to unloaded, on the primary side when I had just a little secondary draw.

Transformers are like motors in that they can take 3 times the current at start-up. Maybe oversize the breaker and use a 3 phase starter with overloads. I've been installing Telemanique's recently because of the price and simplicity.

BTW, found the term for draw under no load is called "exciting current".

Just an idea, but how about a motor start capacitor (over 70 mfd) or two and a relay on the secondary side to shut it/them off (for lack of a centrifical switch).

I've also heard of somebody using motor caps in series to block DC offset, which can cause saturation, but I have no idea of the sizing.

Haven't used a Line Reactor but I'm considering options for one site that's been mysteriously chewing up gas valves and ignition modules.

Frankly, I'm having trouble understanding how you've had so much trouble and the numbers you've got. I do remember when I first started experimenting with power transformers and building a TVC (transformer volume control) line stage at the same time. It's a wonder I didn't pull out all my hair. It was like living in a houseful of women, with sychronized cramps.
.

Dug up some old links.

http://diyparadise.com/dablok.html
http://sound.westhost.com/articles/xfmr-dc.htm
.

Hevac1,

Sorry for obsessing.

Here's the question: You have 208V, which is used in condos and multi-tenant buildings and typically just two legs of 3 phase, which is 60 degrees out of phase as opposed to 90 degrees for 240. Could that be the source of the problem?

I'm assuming you're using something like:
http://www.signaltransformer.com/Data/Datasheets/DU-SU.pdf
and
http://www.geocities.com/jonrisch/catch2.htm

The only other options I know being something like APC/Tripplite

As I've said, you can try 120V but ...