Sizing Isolation Transformer

[Lavcat]

As funds permit, I hope to connect the power for my audio components (amp, preamp, turntable, SACD player) through an isolation transformer.

Power, as measured with a Kill-a-Watt, is 2 Watts for the preamp and 13 Watts for the amp (the amp is AB so the power goes up of course when it is driven hard).

Would a 500 Watt isolation transformer be reasonably sized for my application?

Is there any audio advantage (as opposed to safety advantage) in going with a medical grade transformer, such as the following:

Tripp Lite Isolation Transformer - Medical Grade line noise reduction and spike suppression (IS500HG)

For a medical grade transformer the leakage current is low and is specified, whereas I have not seen leakage current specified for any non-medical grade isolation transformer.

Any thoughts?

[GloBug]

What benefits are you expecting?

All of your items should already have isolation built in.

Perhaps you mean a Power Line Conditioner?

I can see the benefit from a safety POV, audio....not so much.

One has to draw the line somewhere, I prefer my gear to work great, even when plugged into a "dirty" outlet.

So no harm in getting one. 500w sounds OK in your case.

[jameshillj]

I'm no expert about these things but I've tried a couple and ...

My system consumes a lot more power than yours (about 250W) and using a different line noise filter for the amp and source/pre, and I first tried a 600VA very good quality 600VA isolation transformer and it did get rid of some noise in the system but much better result when I found another older unit on eBay (30 year old industrial unit) that is about 1kVA using an EI build (huge thing) with additional filter caps

Many of us out here (with our deteriorating quality 240volt mains) are chasing down even larger units as this seems to work better even with low power demand systems - we have also found that adding dc traps and split (or balanced mains) helps things a lot.

Many people are using some way of "lifting" the components central "0volt point" away from the "chassis earth point" by thermistor, resistor, diodes/caps, etc so all the line sheilds, signal gnds, etc are floating above gnd about 100 ohms for sources, about 10ohms for pwr amps, like a lot of pro gear, studios, etc - not difficult to organise and simple, very effective part of the power system upgrades, including the isolation txr, IMO.

Plenty more discussion about this here awhile back - also, plenty of experts, too, particularly about US power grid anomolies and solutions - you do need to search it out.

Hope this is of interest ....

So, I'd suggest looking for larger 2nd hand units set for your local power supplies to start with - it can get expensive very quickly with just small incremental improvements

Not sure about the specific type of medical grade but mostly extra filtering used but some do have low leakage specification - not sure how relevant to domestic hifi systems.

[Lavcat]

Originally Posted by GloBug

What benefits are you expecting?

All of your items should already have isolation built in.

Perhaps you mean a Power Line Conditioner?

I can see the benefit from a safety POV, audio....not so much.

One has to draw the line somewhere, I prefer my gear to work great, even when plugged into a "dirty" outlet.

So no harm in getting one. 500w sounds OK in your case.

I currently have two computers and three SCR dimmers on the same circuit as the audio equipment. The isolation transformer should remove any DC and much of the noise, but in addition give me a clean, local ground to neutral connection, and a proper place to ground the turntable, which does not have a grounded plug.

[Lavcat]

Originally Posted by jameshillj

I'm no expert about these things but I've tried a couple and ...

My system consumes a lot more power than yours (about 250W) and using a different line noise filter for the amp and source/pre, and I first tried a 600VA very good quality 600VA isolation transformer and it did get rid of some noise in the system but much better result when I found another older unit on eBay (30 year old industrial unit) that is about 1kVA using an EI build (huge thing) with additional filter caps

Many of us out here (with our deteriorating quality 240volt mains) are chasing down even larger units as this seems to work better even with low power demand systems - we have also found that adding dc traps and split (or balanced mains) helps things a lot.

Many people are using some way of "lifting" the components central "0volt point" away from the "chassis earth point" by thermistor, resistor, diodes/caps, etc so all the line sheilds, signal gnds, etc are floating above gnd about 100 ohms for sources, about 10ohms for pwr amps, like a lot of pro gear, studios, etc - not difficult to organise and simple, very effective part of the power system upgrades, including the isolation txr, IMO.

Plenty more discussion about this here awhile back - also, plenty of experts, too, particularly about US power grid anomolies and solutions - you do need to search it out.

Hope this is of interest ....

So, I'd suggest looking for larger 2nd hand units set for your local power supplies to start with - it can get expensive very quickly with just small incremental improvements

Not sure about the specific type of medical grade but mostly extra filtering used but some do have low leakage specification - not sure how relevant to domestic hifi systems.

Thanks, I now have found an isolation transformer thread from 2010 that I had missed. Maybe I should think about larger capacity, but I can't afford that for now. So I guess I'll wait.

But I am not in favor of lifting chassis ground from safety ground.

[jameshillj]

"But I am not in favor of lifting chassis ground from safety ground". Me Neither!!

Sorry, must have written that wrong - leaving off a chassis earth isn't a recommendation at all, adding a chassis earth is often required with domestic hifi equiptment.

What I meant was that you add a thermistor, resistor, etc between the chassis earth (still connected to the chassis and the earth wire) and the components central 0 volt point that is uaually located between the power supply capacitors - usually written as "lifting the power supply central 0 volt point above chassis ground"....

Sorry for the confusion.

I use 10R thermistors for the power amps like the Zen designs and the First Watt amps designs, and an 60 - 100R thermistor for source, preamps, etc so all of my gear that has 240 volt ac supply has a chassis earth, even if it doesn't come supplied with one (as unfortunately, a lot of domestic hifi equiptment still doesn't, relying on the sheild wire for safety!) and I get around the problem of ground loops by "seperating" the internal central 0volt point (usually at the power supply) from chassis earth with a thermistor, resistor, etc - in the case of the developing electronic Xover, I've added a signal isolating transformer (as per Stu Yanager - Acheron design).

In comparison to ProAudio, domestic systems are relatively simple, power wise, and elimenating "hum" and "noise" is fairly straight forward, but sometimes extra components are required - for example, a local guy here lives near a big transmitter and we get around the breakthru problem by using the a 2 wire conductor interconnect (+signal and 0volt on the RCA phono plugs, as usual) but with an extra outer sheild that's only connected to the case (chassis earth) - don't need the extra cctry for balance line system and works very well.

You're in the US, right - just go looking for a 2nd hand Isolating unit that will fit your domestic supply - if you only have 10A outlets, then you're looking for a 1.1kVA unit but in the manufacturing, computer, communications, 2nd hand industial supplies, etc - they regularly upgrade them so there's quite a few around these days and cheaper than specific audio sources.

Something you have to look out for is the way they're wired up - some come setup for "balanced primary use" in which the new earth point is tired to the central tapping of the primary winding and the active (+) and Neutral (-) are at 55volt ac (US Supply)to the new Gnd point, not the usual way of doing things - a number of advantages, but you need to check that it can be altered back for "normal" equiptment.

Hope this is less confusing.