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Discussion of AC mains isolation transformers

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7 hours ago, Speedskater said:

Oops, with regard to:

(with the exception of the secondary of an isolation transformer)

This only applies if the transformer is wired as a Separately Derived System.

 

 

That makes sense for an isolation transformer.  There is no return path from neutral to ground in the panel otherwise.  The regulation also makes sense, since you want the return path to ground to be at the panel, and not get cut short

 

Thank you for the context and information!

 

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Some of the best AC power information is in this Middle Atlantic white paper:

 

"Integrating Electronic Equipment and Power into Rack Enclosures"
'Optimized Power Distribution and Grounding for Audio, Video and Electronic Systems'

 

https://www.middleatlantic.com/resources/white-papers.aspx

 

The part about wiring isolation transformers starts at page 19 or 20.

You do need to enter an e-mail address now.

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I'm getting Strange mV readings through my pseudo P12 > Topaz.  

 

It used to be that the the mV readings (in Alpha EMI meter) would be about as follows:

 

Wall 300 >  P12 600 > Topaz 100      But, now it's:

Wall 300> P12 600 Topaz 600

 

And oddly, this is concurrent with me being able to put my power amp in line after the Topaz without 

a bad hum.   Before, when it was getting the clean readings from the Topaz, I was getting a lot more hum

and it was running pretty hot.

 

So, it's running quiet and cool now , but with high emi noise readings

Could this indicate something is amiss with the Topaz?

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Follow up:   When measured through an Entech powerline noise analyzer, the noise goes from very high out of the wall to very low after the Topaz.  The Entech has a more narrow range (300 - 700 khz) than the Alpha meter (10 khz - 10 mhm).

 

According to C. Gabriel of Shunyata, the Entech (300-700 khz) is in the range that effects musical audio quality the most.

 

So, given the Topaz is drastically reducing this range, is running cooler and with less hum, maybe it's operating optimally.

I'd sure like to know why the change all of a sudden...

 

The only change I've made is disconnecting 3 of my three earth ground rods (on the thought that I put them too close together).

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@wwc, I haven’t looked at the P12 spec and the Topaz you’re using, but one reason the Topaz runs hotter in front of the P12 is it has more work to do in that connection.

Typically the Topaz works by filtering (used sparingly here) on the primary and by the time the secondary creates an output, the common mode noise is really cleaned up.

When the P12 is connected on the secondary of the Topaz, much of the common mode noise and harmonics are coming back from the P12, so the losses increase in the Topaz, which is working correctly.

This shows how unfriendly inverters are for AC networks.

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Any advice on a way to shield the Topaz magnetic field from other components?  

My set up is not very flexible which leaves my DAC only about 2' from the Topaz.

 

Mu Metal in some form between the Transformer and the components? 

 

And, is the Dac more sensitive to magnetic fields than a an amp?

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20 minutes ago, wwc said:

Any advice on a way to shield the Topaz magnetic field from other components?  

My set up is not very flexible which leaves my DAC only about 2' from the Topaz.

 

Mu Metal in some form between the Transformer and the components? 

 

And, is the Dac more sensitive to magnetic fields than a an amp?

I'm positive in this or the headfi thread someone measured their power before and after a topaz was installed and it significantly reduced measured emi.  If your dac is in a thick aluminum case it should at least reduce the effects of other magnetic fields, alot of these components have big transformers in them anyway.  As always the most susceptible components are line level interconnects, and quadrapole wiring and various shielding techniques should take care of the majority of emi.

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Has anyone compared the Topaz to the Equitech balanced iso transformers (like their Q series)?

 

I haven't been able to find any noise reduction specs yet on the Equitech.

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14 hours ago, wwc said:

Has anyone compared the Topaz to the Equitech balanced iso transformers (like their Q series)?

 

I haven't been able to find any noise reduction specs yet on the Equitech.

I have both, Topaz low C 2kVA and Q series 1kVA. The Topaz replaced the Equitech for some 12 months + , I liked what I heard.

As far as Equitech are concerned, their treatment of existing customers is poor to zero. Some technical issues existed with the Q, the LED driver circuits exploding on power up for the first time. Equitech sent new drivers which worked. The delivery was very slow, production problems. I would not recommend Equitech, although their OEM suppliers make a decent transformer, so buy from them instead. You won't find published specs on the common mode noise reduction for Equitech, they couldn't even measure an inch let alone common mode noise.

 

For the money, search high and lo for a low pf Topaz, Elgar or the like. They may not look pretty, but they do a great job.

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After checking (and double checking) that my downstream equipment would be happy with balanced power, I rewired my Topaz 91002-31 for balanced power (+-60V on hot/neutral output lines) and things are working great!

 

As others have mentioned, all the buzz/clicking from my transformer has gone away.  It is still warm (no longer hot) but pretty much silent (I have to lean in to ~10" to hear a very muted/quiet buzzing).  It definitely seems like it is running cooler to the touch

 

Hard to tell if it is a change in power quality or the elimination of the background buzz from the IT, but things are definitely sounding better.

 

Now to rewire the Topaz I use for my digital zone balanced and hopefully get rid of that buzz as well

 

Appreciate the information and coaching from those far more expert than I.  It's great to know enough about how these things work to have the confidence for this type of rewiring job.

 

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2 hours ago, ray-dude said:

After checking (and double checking) that my downstream equipment would be happy with balanced power, I rewired my Topaz 91002-31 for balanced power (+-60V on hot/neutral output lines) and things are working great!

 

As others have mentioned, all the buzz/clicking from my transformer has gone away.  It is still warm (no longer hot) but pretty much silent (I have to lean in to ~10" to hear a very muted/quiet buzzing).  It definitely seems like it is running cooler to the touch

 

Hard to tell if it is a change in power quality or the elimination of the background buzz from the IT, but things are definitely sounding better.

 

Now to rewire the Topaz I use for my digital zone balanced and hopefully get rid of that buzz as well

 

Appreciate the information and coaching from those far more expert than I.  It's great to know enough about how these things work to have the confidence for this type of rewiring job.

 

That’s great news! Yes the buzzing noise is caused by frequencies that are trapped in the windings with nowhere to go.

By using a balanced supply, the same frequencies are cancelled, the transformer is cooler and less noisy.

 

For SQ, deliberately listen to the silence between tracks or a very long fade out, there should be less mire and more black.

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Confirmed that I got the same impact/benefit with my second Topaz isolation transformer (a 91018-31T this time)

 

I also finally got around to using my KillAWatt to measure power factor.  Coming in at 0.7 with the linear power supplies and class AB amps I have connected to the first unit.  I'm out of hobby time this weekend, but on the list is to measure the PF going into the Topaz to see how well it is insulating the rest of my house from the heavy PF load from the amps and LPS

 

I did have time for one other quick experiment.  I just got some BK Precision 1604A isolation transformers to help isolate some smaller switching supplies.  These buzz quite heavily.  Naively, I would have thought that plugging them into the balanced output of the topaz would impact them as well, but the buzzing is the same whether plugged into balanced power or normal power.

 

I just added cracking the case open to see how these guys are wired internally (does anyone have a wiring schematic for the 1604A's?)

 

 

 

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5 hours ago, ray-dude said:

Confirmed that I got the same impact/benefit with my second Topaz isolation transformer (a 91018-31T this time)

 

I also finally got around to using my KillAWatt to measure power factor.  Coming in at 0.7 with the linear power supplies and class AB amps I have connected to the first unit.  I'm out of hobby time this weekend, but on the list is to measure the PF going into the Topaz to see how well it is insulating the rest of my house from the heavy PF load from the amps and LPS

 

I did have time for one other quick experiment.  I just got some BK Precision 1604A isolation transformers to help isolate some smaller switching supplies.  These buzz quite heavily.  Naively, I would have thought that plugging them into the balanced output of the topaz would impact them as well, but the buzzing is the same whether plugged into balanced power or normal power.

 

I just added cracking the case open to see how these guys are wired internally (does anyone have a wiring schematic for the 1604A's?)

 

 

 

The Kill-A-Watt meters don't read reactive pulses very well, but they give you a within 20% in range reading as a safe measurement.

 

The front end of a transformer pf will be low due to the loading of the transformer, the lower, the worse pf, but you aren't invoiced by the power company for pf penalties at home.

 

The BK transformer, looks like a single winding only, with no taps. If you have two of these, and feed the primaries in series, so each will have 60V. The secondaries can then be wired 60-0-60. The rating is the same as a single unit tho. There are some tests to do, you need a DMM to make sure the secondary polarity is correct to achieve a balanced output.

 

Depending on the symmetry, you could cancellation, but a purpose transformer with the same windings on the same core will cancel better. 

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Thank you, that’s great info!

 

i did end up cracking open a 1604a last night and can confirm two wires in and two wires out (floating shield as expected)

 

The interesting thing is the two point mounting scheme they use for the heavy transformer. One of the mounting brackets had been bent (presumably in transit). A little muscle action and the mechanical buzzing went way down.   A reminder that these transformers definitely have a mechanical aspect to them. 

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A question for those that have played with a capacitor across the output terminals of their Topaz isolation transformers.

 

One of my Topaz units has a large capacitor connected to the hot and neutral lines on the output (when I switched to balanced configuration, now connected to +-60V lines).  Reading through the Topaz manual, it looks like these are there to minimize transverse-mode noise.

 

I practice, how does transverse-mode noise manifest itself (if at all) in an audio system?  Given the importance of the ground and voltage reference, common-mode noise reduction makes a huge amount of sense to me (which is why I have a couple of the Topaz IT's).  I'm trying to get my head around transverse-mode noise, both in a conventional Hot-Neutral configuration (Neutral connected to ground at the breaker box, and at the output of the transformer), and in a balanced Hot-Hot (+-60V, center tapped ground) configuration.

 

For those that have researched/played with this stuff, how important/impactful is transverse-mode noise reduction in an audio context?  Is it worthwhile for me to be adding a large cap to the output of my other Topaz IT?

 

 

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