Discussion of AC mains isolation transformers

[One and a half]

1 hour ago, wwc said:

Another question on these iso transformers?

 

I'm not sure if I want to run my subs (combined 3000 Watts RMS)

through the transformer or into the wall outlets.  I only need a 1800 VA

transformer for everything else, but would need at least 5000VA if 

using the Subs.

 

First question, if I do not use the Subs, is there any downside to having

an oversized transformer (other than probably more expensive)?

 

For the very low frequencies Subs are working at, is the iso transformer of 

significant benefit?

 

Thanks

Measure the power draw with a Kill-A-Watt at ear splitting levels, then you'll know exactly what the power draw is, in VA. 3000W is more PMPO or marketing ratings. To cater for that amount of current, that's 25A at 120V, is the cable to the sub a 10 or 12 guage cable? I'd say not.

[One and a half]

9 hours ago, flkin said:

John, does the Topaz impede current flow in any way in comparison to direct from wall socket? Does the magnetic way of transferring AC signals reduce the ability to send transient current demands instantaneously? 

Have a look at this post. The transformer has enough capacity to deliver (over) current.

[wwc]

24 minutes ago, One and a half said:

Measure the power draw with a Kill-A-Watt at ear splitting levels, then you'll know exactly what the power draw is, in VA. 3000W is more PMPO or marketing ratings. To cater for that amount of current, that's 25A at 120V, is the cable to the sub a 10 or 12 guage cable? I'd say not.

The 3000 watts I'm referring to is listed as RMS (1500 per sub).  Is RMS more accurate, as it's measured over time, whereas "Peak Momentary Output" is measured in micro seconds?

 

If everything (except the subs)-- that is, Amp, DAC, etc are plugged into a power strip, or in my case

a Richard Gray Power 1200c (parallel chokes, no capacitor filtering), will plugging the Kill A Watt into that unit give an accurate power draw reading?   Thanks

[One and a half]

1 hour ago, wwc said:

The 3000 watts I'm referring to is listed as RMS (1500 per sub).  Is RMS more accurate, as it's measured over time, whereas "Peak Momentary Output" is measured in micro seconds?

 

If everything (except the subs)-- that is, Amp, DAC, etc are plugged into a power strip, or in my case

a Richard Gray Power 1200c (parallel chokes, no capacitor filtering), will plugging the Kill A Watt into that unit give an accurate power draw reading?   Thanks

A Kill-A-Watt will give you an idea of power draw. As to the accuracy, it's a little doubtful, but it's on the generous side. If <2% accuracy is needed, then a DMM with a current probe is the best option.

[Ralf11]

a torus is just a fancy name for a doughnut shape - the article link posted earlier gave a good run-down on the different designs and the several factors favored or dis-favored in each design

 

 

to me, the man issue with the Kill-A-Watt is how it responds to transients rel. to the amp, etc. - take it as an estimate and add a safety factor

[Cornan]

13 hours ago, wwc said:

 Cornan,

 

Thanks for the advice.  Could you be more specific as to what you're talking about?  

Torus, Plintus...?

 

A make, model example would help get me on the trail!

 

And are you advising against the low capacitance IT's ?  

 

Any elaboration you want to go into, please feel free!

 

Thanks

 

Personally I am using a custom made balanced IT from ATL Hi-Fi. Here is the schematics.

 

This IT have a toggle switch to ground or float the secondary balanced center tap that I added to make it possible to quickly compare the two. Floating is so much better in my setup so the toogle switch in not used anymore. This IT requires a 2-pole RCD/GFCI at the output for safety.

 

I am not arguing against low capasitance, but I am questioning that it is the only great argument for a good IT. A Topaz can for example be rewired this way without too much work involved.

[jamesg11]

“ A Topaz can for example be rewired this way without too much work involved.”

 

Which would have both the low capacitance + the floating balanced advantages?

[Cornan]

4 minutes ago, jamesg11 said:

“ A Topaz can for example be rewired this way without too much work involved.”

 

Which would have both the low capacitance + the floating balanced advantages?

 

Yes! You would possibly end up with a quiet Topaz as well. Win win! ?

[jamesg11]

2 minutes ago, Cornan said:

 

Yes! You would possibly end up with a quiet Topaz as well. Win win! ?

Interesting.

Get rid of any hum? How does it achieve that ...?

[Cornan]

1 minute ago, jamesg11 said:

Interesting.

Get rid of any hum? How does it achieve that ...?

 

Mainly the balanced wiring which is known to reduce IT hum. In my non Topaz balanced IT the floating option is more quiet that the grounded. Not completely sure why though?

[One and a half]

21 hours ago, Ralf11 said:

a torus is just a fancy name for a doughnut shape - the article link posted earlier gave a good run-down on the different designs and the several factors favored or dis-favored in each design

 

 

to me, the man issue with the Kill-A-Watt is how it responds to transients rel. to the amp, etc. - take it as an estimate and add a safety factor

All meters work to a given sampling rate that's afforded by the microprocessor in the meter. Higher sampling rates, the more accurate the reading, a familiar analogy with audio ADC.

[One and a half]

5 minutes ago, Cornan said:

 

Mainly the balanced wiring which is known to reduce IT hum. In my non Topaz balanced IT the floating option is more quiet that the grounded. Not completely sure why though?

If the earth is lifted from the centre point, the transformer doesn't do any work at absorbing unbalanced crud, that's why it's quiet.  

[wwc]

I'm trying to figure what size Iso Transformer I need for my components load.

 

From the info on component back and spec lists I estimated my load would be about 

1200 watts: 

 

 Amp  60 watts, Speaker bass amps  1000 watts, Dac  100 watts,  Network switch 11.

I did not include my subs (rated at 1500 watts RMS).

 

So I'm confounded at the readings off the Kill a Watt.  This is with music playing loudly.  

 

Amp   20,  Speaker amps  60 watts,   Subs  50 watts.

 

If this is correct I could easily get away with a 500 VA Transformer or less  (including using the Subs through it)

 

Please tell me what I'm missing?   Thanks

[One and a half]

3 minutes ago, wwc said:

I'm trying to figure what size Iso Transformer I need for my components load.

 

From the info on component back and spec lists I estimated my load would be about 

1200 watts: 

 

 Amp  60 watts, Speaker bass amps  1000 watts, Dac  100 watts,  Network switch 11.

I did not include my subs (rated at 1500 watts RMS).

 

So I'm confounded at the readings off the Kill a Watt.  This is with music playing loudly.  

 

Amp   20,  Speaker amps  60 watts,   Subs  50 watts.

 

If this is correct I could easily get away with a 500 VA Transformer or less  (including using the Subs through it)

 

Please tell me what I'm missing?   Thanks

If you can wait until the weekend, I can compare the VA of a load using a Fluke 289 and clamp meter versus the kill a watt reading of an audio system. 

 

Its very likely the kill a watt doesn’t sample enough for an accurate reading and a factor applied may achieve a semblance of accuracy.

 

The issue is the current draw by the amps are non linear and weird shapes, difficult for the kill a watt to measure.

[sockpit]

I have a 500VA topaz.  I run a 100watt amp and a JS2 feeding a DAC and mRendu with it.  I don’t run a sub or anything from it.

 

when I plug the kilowatt in just prior to the Topaz, I get readings of about 32 Watts for the whole kit, even when playing loudly.  I asked about this somewhere above and someone replied that the kilowatt can’t capture or record the transient peaks my amp demands.

 

I continue to doubt that such transient draws would ever come close to 500va. Others will actually understand your specific needs better, but I suspect most moderate wattage systems don’t need a massive humming transformer heating up the room.

[Ralf11]

play it loud and also play bass heavy music

[wwc]

The highest reading I've been able to get from the Speaker bass amp (Avantgarde Duo Grossos) is 59 watts.

The Speaker  amp's spec is 250 watts/channel RMS.  On the back of the Speaker it reads "530 watts."

The Speakers "power output" is 100 watts.  

 

I will be upgrading these speakers to a 500 watts/channel RMS.  So that peak I measured at 59 could possibly be extrapolated

to 120 watts.

 

So it seems  even if the new speaker amps were to peak as high as 150-200 watts, it seems a 500 VA Topaz or Elgar 

would be enough for my set up-- that is, unless the Kill a Watt is not reliable for testing audio power output?

 

So I guess the uncertainty I'm left with is should I base VA sizing on the Kill a Watt measurements or on the RMS 

watt specs?  

[jamesg11]

Wait for the one & a half xfactor calculation ...

[Ralf11]

I would upgrade the speakers first, unless you are certain they are the same efficiency.

[flkin]

I have a Topaz 1.8kW unit rated for 120/240V. But for this unit, I don't see any S1 or S2 shields which I'm more familiar with having done the wiring for another 1kW Topaz. So I'm writing to ask for advice on how I should do this unit. I am trying to wire it for 240V and am following the schematic on the black end plate.

 

Input:

Jumper between H2 & H3

Live wire on H1

Neutral wire on H4

 

Output:

Jumper between X2 & X3

Live wire on X1

Neutral wire on X4

 

 

Having done the above along with earth to chassis, the output multimeter reading is indeed 240V but it seems that live and earth are also connected and this surely isn't correct. Have I made any obvious mistakes?

 

I'm also concerned that the black and white cables (from the pics) from the windings are not attached correctly. Currently they are connected as:

 

Input side: Black H1 and H2, White H3 and H4

Output side: Black X1 and X2, Whilte X3 andX4

 

Can anyone help with the necessary connections?

 

Thanks!  Kin

 

 

 

[Abtr]

14 hours ago, wwc said:

I'm trying to figure what size Iso Transformer I need for my components load.

 

From the info on component back and spec lists I estimated my load would be about 

1200 watts: 

 

 Amp  60 watts, Speaker bass amps  1000 watts, Dac  100 watts,  Network switch 11.

I did not include my subs (rated at 1500 watts RMS).

 

So I'm confounded at the readings off the Kill a Watt.  This is with music playing loudly.  

 

Amp   20,  Speaker amps  60 watts,   Subs  50 watts.

 

If this is correct I could easily get away with a 500 VA Transformer or less  (including using the Subs through it)

 

Please tell me what I'm missing?   Thanks

I used a 900VA isolation transformer with a 200watt amp and 1000watt subs and it properly shook the room. No problem at all for the transformer, which may easily deliver transient power above its rating..

[Abtr]

On ‎7‎-‎4‎-‎2018 at 11:45 PM, One and a half said:

If the earth is lifted from the centre point, the transformer doesn't do any work at absorbing unbalanced crud, that's why it's quiet.  

I use an Airlink mains isolation transformer with balanced output (BPS1500EU). IME disconnecting the secondary center tap from mains Earth significantly improves SQ. Only the analogue gear and the DAC are connected to the Airlink AC output and all chassis/grounds are disconnected from the center tap and from each other. So basically everything 'floats' which gives the best SQ in my system. A further SQ improvement is obtained by connecting the secondary center tap of the Airlink to some mass such as the chassis of an unused amp or cdp. I think that connecting the center tap to its own dedicated pin into Earth would be best.

 

So connecting the secondary center tap to mains Earth is no option for me. My mains Earth connection is obviously noisy and I don't want that noise in my system. YMMV. The SQ improvements I mentioned above are quite audible and I think each can be readily measured as reduced noise and THD at the outputs of the pre-amp or power-amp..      

[wwc]

Has anyone noticed a difference in audible hum between the Topaz and Elgar IT's ?  

 

 

[wwc]

On 4/7/2018 at 4:23 PM, jamesg11 said:

“ A Topaz can for example be rewired this way without too much work involved.”

 

Which would have both the low capacitance + the floating balanced advantages?

If one is not electronically experienced or diy inclined, would you just try to find an electrician

or someone more specialized?

[One and a half]

8 hours ago, flkin said:

Having done the above along with earth to chassis, the output multimeter reading is indeed 240V but it seems that live and earth are also connected and this surely isn't correct. Have I made any obvious mistakes?

Is this H1 to earth, then it's correct, since the earth and neutral are tied back at the main switchboard panel.

 

On the output, X1 to earth should read 240 V provided X4 and Earth are jumpered. 

 

It's odd the shield wires aren't there, what's the label on the lid say? Perhaps they are bonded already inside.