Audio Transformer Jaycar

[Octavis Marquez]

Ifyou can specify the impedance of the transformer, say 15% and higher still, you get the effect of reducing the pulse rate (ramp). The transformer gets warm, and it's only reactive losses that contribute to that heat, it's not real power you pay for. The 'danger' of overating the transformer means it has nothing to do, and the effect is gone and reducing the power factor even more but I guess a resonance is also not a consideration anymore due to the lower impedance of the transformer.

Makes it kind of tough for the hobbyist to choose. If you don't want to experiment, then you may as well buy the correct (in this case) DAC with the correct transformer for where you live. The added advantage is the mains AC section has been tested and approved to local regulations and from a commercial sense a full (limited) warranty is available.

I was happy that I could go ahead and buy the Japanese unit as this transformer was of good quality and it would actually improve the sound. But now there are contradictions that good is not really good and could be bad?

The dimensioning of the transformer is where the issue lies. Transformers are rated in VA and assumes the power factor to be a 1 with a pure resistive load like a filament lamp or a non inductive resistor.

Once a non linear load is connected, and that means anything else, the load draws reactive current. The more reactive current there is, the more the transformer has to draw on real watts to produce that reactive current. The end result is, the transformer needs to supply real current and reactive current as a vector sum of the two. Effectively the transformer gets hot and can overload, but what you measure with a current probe only reveals 1/2 the story.

If you were to measure the power factor in the load circuit, you can see how much reactive 'power' there is and correct it with AC rated capacitors. Practically this is very difficult for the hobbyist, since you can correct for your neighbour as well.

Actually, there is very little disagreement between all 3 of you. It never hurts to use an over dimensioned transformer though, as it can be reused elsewhere at a later date if need be. It's a different matter if you need to squeeze in a smaller transformer in the same case

How a Digital Audio file sounds, or a Digital Video file looks, is governed to a large extent by the Power Supply area. All that Identical Checksums gives is the possibility of REGENERATING the file to close to that of the original file.

In a cheap isolation transformer (I was using a $12 one) the core losses are so high that they damp any parasitic resonances of the transformer itself, AND help with resonances of the device plugged into it as well. With devices that do not have good control over their transformer resonances (almost everything) this can make a significant difference.

Be prepared, that because of the losses they will get warm, that is normal and means you are getting what you want, a lousy (er lossy) transformer. Cheap ones can also buzz, so the trick is to find one that gets warm, but doesn't buzz. Since they are cheap you can try several and see which works best.

What John says is true. For a few years at Hovland Company, we (not including John here, though I did get him involved with us on a big digital project around 2005, and we are of course doing things together again now) offered a 1:1 isolation transformer in a shinny box (which also helped keep it quiet), and called it the VoltAire.

It was developed in response to the fact that we often preferred the sound of our preamps being run through a large cheap VARIAC or the step-up or step-down transformers we used--all when auditioning and running in a bit each unit before shipment, more than half of which went overseas.

The custom transformer house we used for all our amps and preamps (nothing was ever "off-the-shelf" at Hovland--a contributor to our demise) was Frost Magnetics in Oakhurst, CA (entirely a coincidence that Oakhurst is the next mountain town over from where I have lived for 23 years, while Hovland was 300 miles south in Los Angeles). They can make everything from small, high-precsion transformers for aerospace, to huge beasts the size of a washing machine. And they did some tricky units for us (quasi-C-core anyone?).

Anyway, we asked them to make us samples of some modest 250W 1:1 EI transformers. They did their usual quality job of making a tightly-coupled, low loss unit, vacuum-impregnated with shellac and baked. The sounded terrible!! So we asked them to loosen the spec a bit and also put in some extra layers of whatever the dielectric insulation wrap was. Definitely better, but not quite there. So we begged them to through out the book and make something really sub-standard--but to still impregnate and bake it so it would not bee too noisy. They thought we were nuts but did it anyway. Bingo!! A fabulous sounding isolation transformer was born. Really would not want to try to size one for a big power amp, but for source components it is magic. Plus it offers some protection without using the typically bad-sounding, dynamics-restricting filter elements that a lot of "power conditioners" have. And since I float the ground of the input of mine, it is almost like having an Equitech-style balanced AC line.

I used to visit Japan all the time for business. Almost every time I went there, I bought some piece of audio exotica in the Aki Habara region of Tokyo. All of it was rated at 100 Volts/60 Hz. I've plugged it into US Mains and operated some of it for years with no problem. The equipment's power supplies didn't even get warm. US mains is generally given at 110-120V, so we're talking 10 to 20% over voltage, when plugging Japanese home market equipment into US mains. I think one might have a problem the other way around, i.e. 15% under voltage, but not with a measly maximum of 20% over-voltage! I just don't think it's a problem.

If you're trying to convince yourself that nothing will do but a Luxman DAC built for a different market then base your purchase with due consideration for the future resale and serviceability factors.

I would be suspicious of any isolation step-up/down device that cost just $25 (including both Amazon's and the manufacturer's profit and cost to ship it from China). Then again, I bought just such a device a couple of months ago for pre-testing our JS-2 LPS units at 220/230/240V before shipping them overseas:

My point was that the cost savings - with the need for a transformer that may or may not affect the sound quality, and with a possible frequency mismatch - and the fact that if something goes wrong with it you may not be able to find someone willing to service it - and if and when you go to sell it you might have a hard time finding a buyer could all possibly add up to your wanting to consider other options.

Alice, you may have some of us confused. Tommy (tboooe) started this thread long ago about bring a 100V Luxman DAC to the USA for 120V operation. You said you are looking at the same DAC, but only now did I go back and see that you are in 230V Australia. Very different.

I guess what some of us are trying to suggest is you may want to be a bit more flexible with your selection of hardware. Always your decision, of course. You may want to contact a local dealer or supplier (if there is one) to enquire if they will service if needed. It could be considered as grey market and untouchable.

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