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Discussion of AC mains isolation transformers

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I think that those measurements might be what electricians call phantom voltage (very different from microphone phantom power).

A DMM has a very high impedance on the voltage ranges and can pick-up all kinds of stray voltages.  The isolated Hot/Neutral is not referenced to the Safety Ground or chassis.

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When using smaller units(I have a 91092-12 and 91092-31), is it recommended to put anything between the wall and the transformer?  i.e. UPS, AVR, or additional surge protection?  I have 1a or 2a fuses at the input but thats it.

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250VA units aren't good for much. Assuming a power factor of 1, that is 250 watts. A power factor of .8 is more likely and that is only 200 watts.

 

You don't need or really want anything between the wall and the transformer. They "reduce a 6,000 volt spike to an insignificant 0.0030 volt."

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51 minutes ago, diecaster said:

250VA units aren't good for much. Assuming a power factor of 1, that is 250 watts. A power factor of .8 is more likely and that is only 200 watts.

 

You don't need or really want anything between the wall and the transformer. They "reduce a 6,000 volt spike to an insignificant 0.0030 volt."

Using em with headphone systems so I dont think to much wattage is necessary?  Had assumed as much as well with stuff between the wall just wanted to ask, thank you. 

 

How bout power cabling, since usage is for digital devices is having the low inductance quadrapole cabling between the wall and the transformer beneficial, between the transformer and the equipment as well?

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More than enough VA to power a DAC or some preamps like the Freya.  


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Hi: I've bought a Elgar model 2.5-13.  It is 2.5kVa and .0005 pfd.  It appears to be the same as or very similar to a Topaz 91002-31.  

 

The input (from the wall outlet) is wired.

 

The output has to be wired.  Would the black and the white wires go in the same position that they are wired in the input?

1.jpg

output.jpg

pic1.jpg

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On 2/14/2019 at 10:49 PM, diecaster said:

You don't need or really want anything between the wall and the transformer. They "reduce a 6,000 volt spike to an insignificant 0.0030 volt."

The  transformer will have no significant effect on a Hot to Neutral spike! 

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On 2/14/2019 at 10:49 PM, diecaster said:

250VA units aren't good for much. Assuming a power factor of 1, that is 250 watts. A power factor of .8 is more likely and that is only 200 watts.

Yep!

About all a 250VA transformer is good for is reducing ground loop problems on poorly designed hi-fi components.

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6 hours ago, Speedskater said:

The  transformer will have no significant effect on a Hot to Neutral spike! 

 

One of major points that Topaz specifically called out for their isolation transformers was electrical surge suppression.......as I quoted in my post. 

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23 hours ago, diecaster said:

One of major points that Topaz specifically called out for their isolation transformers was electrical surge suppression.......as I quoted in my post. 

 

Sorry, @Speedskater is mostly correct.  Isolation transformers do not suppress differential spikes at frequencies below about 10KHz.

But a lot of the energy in high power surges is contained in high frequency components, which do get suppressed by the very low capacitance of the specialty Topaz transformers.  But generally one can not consider an isolation transformer as serving the same function as a surge suppressor.

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8 minutes ago, Superdad said:

 

Sorry, @Speedskater is mostly correct.  Isolation transformers do not suppress differential spikes at frequencies below about 10KHz.

But a lot of the energy in high power surges is contained in high frequency components, which do get suppressed by the very low capacitance of the specialty Topaz transformers.  But generally one can not consider an isolation transformer as serving the same function as a surge suppressor.

Thanks for the response.  So would you recommend a ups/surge unit before the topaz? I'm also wondering about the switching off of the amplifier(from an outage) while headphones are connected.

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Surge suppression should be dealt with where the AC power enters the building. Using a whole home suppression unit.

Make that a 'UL' rated/listed unit. Been reading on the electricians pages about unlisted units going up in flames.

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1 hour ago, Speedskater said:

Surge suppression should be dealt with where the AC power enters the building. Using a whole home suppression unit.

Make that a 'UL' rated/listed unit. Been reading on the electricians pages about unlisted units going up in flames.

 

Since the whole home units use MOVs (as far as I know), is there any possible issue with them losing effectiveness over repeated use, or even "going up in flames"?


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With MOV's there is always a small possibility of failure. It was un-rated units that went up in flames.

Go with top shelf name brand units from an electrical supplier and replace them every decade or two. 

Everything in your AC power system should be 'UL' rated.

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Question: in one of his latest videos in YouTube, PS Audio's Paul McGowan states that switch mode power supplies are happier with single ended power as opposed to balanced power. He does not explain why.

 

Is this true? And if so, can anybody explain it technically (in terms that I as a generalist can understand.... 😉)? The reason I ask this is because I use an isolation transformer in a 230V country, wired for balanced output to power all audio components of which two use switch mode power supplies.


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17 hours ago, skatbelt said:

Question: in one of his latest videos in YouTube, PS Audio's Paul McGowan states that switch mode power supplies are happier with single ended power as opposed to balanced power. He does not explain why.

 

Is this true? And if so, can anybody explain it technically (in terms that I as a generalist can understand.... 😉)? The reason I ask this is because I use an isolation transformer in a 230V country, wired for balanced output to power all audio components of which two use switch mode power supplies.

 

Anyone? @JohnSwenson for instance?


Roon server (Mac Mini/i7/SSD/16GB/Uptone DC mod/external SDD via firewire/Uptone Audio JS-2 LPS) Streamer dCS Network Bridge DAC Chord DAVE Amplifier / DRC Lyngdorf TDAI-3400 Speakers Lindemann BL-10 | JL audio E-sub e110 Cables CAT6 UTP ethernet, Transparent premium AES/EBU, Nordost Leif Red Dawn analog RCA, Kimber 8TC speaker cables, custom star-quad power cables with Oyaide termination Head-fi and reference Bakoon HPA-21 | Audeze LCD-3 (f) | Audio-technica ATH-M50 Software High Sierra | Roon 1.6 | Tidal hifi Power and isolation Dedicated power line | Xentek extreme isolation transformer (1KVA, 0.0001pf, balanced) | Vibex one 6R power distributor | Uptone EtherREGEN | Emo Systems EN-70HD network isolator | Jensen CI-1RR isolator

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Folks, forgive the newbie question, but I'm lost a bit in the various wiring scenarios for the Topaz Ultra Isolation transformers.  

 

I've tracked down a 91018-31T and 91002-31 on eBay.  I'm US-based (120V) so I have H2/H4 (neutral) jumpered and H1/H3 (hot) jumpered on input, and X2/X4 (neutral) jumpered and X1/X3 (hot) jumpered on output.

 

My question is where to wire ground on input and output.  On one unit, ground was jumpered to H4 (neutral) on input and X4 (neutral) on output.  On the other unit, ground was only connected to X4 on output (not jumpered to H4 on input)

 

Should ground stay floating from the primary and secondary, or should it be grounded to the secondary or should it be grounded to both primary and secondary?

 

 

9999137.jpg.2aa5fd271db4f44154eb0842212b859b.jpg

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20 minutes ago, ray-dude said:

Folks, forgive the newbie question, but I'm lost a bit in the various wiring scenarios for the Topaz Ultra Isolation transformers.  

 

I've tracked down a 91018-31T and 91002-31 on eBay.  I'm US-based (120V) so I have H2/H4 (neutral) jumpered and H1/H3 (hot) jumpered on input, and X2/X4 (neutral) jumpered and X1/X3 (hot) jumpered on output.

 

My question is where to wire ground on input and output.  On one unit, ground was jumpered to H4 (neutral) on input and X4 (neutral) on output.  On the other unit, ground was only connected to X4 on output (not jumpered to H4 on input)

 

Should ground stay floating from the primary and secondary, or should it be grounded to the secondary or should it be grounded to both primary and secondary?

 

 

9999137.jpg.2aa5fd271db4f44154eb0842212b859b.jpg

My Topaz was delivered with H4 connected to GND, and was swiftly removed. Thou shalt use but only one connection from GND to the neutral, and that's at the main panel. Things get complex for generators in the same installation, let's assume you don't have one, so kick the connection from H4 to GND.

 

So the green wire from the wall, connect it to the H part of the box to GND.

At the X part on the other side of the transformer, best for now to jumper X4 to GND, and the green wire to the connected loads.

 

The GND should pass all the way through the structure of the transformer from the H to the X boxes, please check it with a mulitmeter. There should be some more wires connected to the GND terminal internally, these go back to the GND, don't float these shield wires.

 

You have the connections right for the hot and neutral on both sides. H1 is the black and H4 the white. X1 is the hot (black) and X4 (white) on the output. 


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Thank you @One and a half!  I appreciate the quick reply.

 

To confirm, leave neutral on the  primary disconnected from ground, but connect neutral on the secondary to ground. Ground and shield should be continuous through the transformer (per the graphic).

 

Can you add some color on the motivation/implications of leaving neutral disconnected from ground (except at the main panel)?  Is the intent of connecting neutral on the secondary to ground to mimic the same connection at the main panel?

 

 

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12 minutes ago, ray-dude said:

Thank you @One and a half!  I appreciate the quick reply.

You're Welcome.

12 minutes ago, ray-dude said:

 

To confirm, leave neutral on the  primary disconnected from ground, but connect neutral on the secondary to ground. Ground and shield should be continuous through the transformer (per the graphic).

Yes leave the incoming neutral disconnected from GND, just connect to H4.

12 minutes ago, ray-dude said:

 

Can you add some color on the motivation/implications of leaving neutral disconnected from ground (except at the main panel)?  Is the intent of connecting neutral on the secondary to ground to mimic the same connection at the main panel?

 

Oh, simple. Rules are Rules, it's in the NEC code, @Speedskater could cite the exact enforced clause that applies. It's not that leaving the neutral off is the complication, it's the leaving it on is the problem.


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Everywhere (with the exception of the secondary of an isolation transformer) the only place that the Neutral and the Safety Ground/Protective Earth may be connected together is at the main breaker box and this connection is required.

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On 2/21/2019 at 5:54 PM, Speedskater said:

With MOV's there is always a small possibility of failure. It was un-rated units that went up in flames.

Go with top shelf name brand units from an electrical supplier and replace them every decade or two. 

Everything in your AC power system should be 'UL' rated.

 

also check for any known issues - one US brand had a number of problems but did not issue a recall 


"The overwhelming majority [of audiophiles] have very little knowledge, if any, about the most basic principles and operating characteristics of audio equipment. They often base their purchasing decisions on hearsay, and the preaching of media sages. Unfortunately, because of commercial considerations, much information is rooted in increasing revenue, not in assisting the audiophile. It seems as if the only requirements for becoming an "authority" in the world of audio is a keyboard."

-- Bruce Rozenblit of Transcendent Sound

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20 hours ago, ray-dude said:

Folks, forgive the newbie question, but I'm lost a bit in the various wiring scenarios for the Topaz Ultra Isolation transformers.  

 

I've tracked down a 91018-31T and 91002-31 on eBay.  I'm US-based (120V) so I have H2/H4 (neutral) jumpered and H1/H3 (hot) jumpered on input, and X2/X4 (neutral) jumpered and X1/X3 (hot) jumpered on output.

 

My question is where to wire ground on input and output.  On one unit, ground was jumpered to H4 (neutral) on input and X4 (neutral) on output.  On the other unit, ground was only connected to X4 on output (not jumpered to H4 on input)

 

Should ground stay floating from the primary and secondary, or should it be grounded to the secondary or should it be grounded to both primary and secondary?

 

 

9999137.jpg.2aa5fd271db4f44154eb0842212b859b.jpg

 

I'd go look at posts #854 to #872 in this thread.

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