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Discussion of AC mains isolation transformers


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Thanks John.  That all sounds favorable.

 

IIRC, your location sounded rural (septic).  Any ideas on noise sources in the house or nearby?

 

Your comment makes me wonder if Staging could be altered by a lower noise floor - I mean as a psycho-acoustic phenomenon (in the brain, not in the DAC, etc.)...

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48 minutes ago, Ralf11 said:

Thanks John.  That all sounds favorable.

 

IIRC, your location sounded rural (septic).  Any ideas on noise sources in the house or nearby?

 

Your comment makes me wonder if Staging could be altered by a lower noise floor - I mean as a psycho-acoustic phenomenon (in the brain, not in the DAC, etc.)...

 

What John is reporting is typical of a lower noise floor when you further reduce low level wideband noise, which is sometimes evidenced as a slightly " gritty" sound. Female voices can often sound a little more individual too.

It isn't psycho-acoustic either. Given the right equipment you should be able to see the difference at the analogue output of the DAC. You may need to save the waveforms for direct side by side comparison though.

 WRT the improvement with Female voices, it's more likely to be due to higher order ,very  low level harmonics being less masked by residual System Noise. They may even sound very slightly higher pitched too, due to the less masked upper order harmonics.

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.

PROFILE UPDATED 28-06-2020

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25 minutes ago, Ralf11 said:

Thanks John.  That all sounds favorable.

 

IIRC, your location sounded rural (septic).  Any ideas on noise sources in the house or nearby?

 

Your comment makes me wonder if Staging could be altered by a lower noise floor - I mean as a psycho-acoustic phenomenon (in the brain, not in the DAC, etc.)...

 

Not rural.  A suburb of Chicago.  Just lucky to be in an unincorporated subdivision.  My own septic and water means much lower taxes.  There's a lot of possibility for noise.  Nothing industrial in the immediate vicinity, but a couple miles away.

 

Anything's possible when running in house experiments.  I can't rule out psycho acoustic bias.  I do have the ability to swap between a circuit without the transformer and did that briefly.  I thought I heard a difference, but looking back I could put more time and effort into testing.

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is there anyone in the house who would enjoy messing with your head?

 

say, a person with too many X chromosomes who would set up a blind test with the outlets -- just to "prove" that you are wasting time by messing with the audio system?

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Hi all! Just picked up a 5 kVa 0.0005pF topaz from a surplus store, in preparation for adding dedicated lines to my Audio room.

 

The plan is to add two MC 10/2 or 10/3 lines from my basement panel to the music room which lies above the garage. I had a couple of question that I was hoping those more knowledgeable could chime in on. I have a licensed electrician doing the work even though I’m reasonably comfortable with doing outlet and switch work.

 

The Topaz would sit at the end of the basement closest to the music room although in the basement, it is still 30 ft or so away from the music room. It would sit in line with one of the dedicated lines, with the other being a nice comparison for transformer or no transformer.

 

1. Would it be better to run 240V in to the topaz, or 120V? My electrician offered to run 240V line from breaker panel. Not sure which is better- any views? Would doing 240V in reduce the VA rating? I’m guessing not, only if balanced out was used?

 

2. I’ve decided to stick with 120V single ended output as I don’t want to deal with the potential code violations and having to install a GFCI/DPDT switch for balanced, unless someone can convince me otherwise. Anyone here running balanced out 120V from their Topaz?

 

3. Is it a mistake having the Topaz be 30 ft away from final outlet? I’ve seen recommendations that the Topaz be close to the final outlet although I was hoping to not worry about transformer hum having it in the basement.

 

Any input appreciated, especially from the likes of @Speedskater @One and a half @zilch0md @Johnseye @sandyk

All of your contributions have taught me so much!

 

Yeang

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Superdad may also be able to offer some valuable advice in this area.

One and a half  (Garry) is well across this whole area, with both indepth theoretical and practical experience .

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.

PROFILE UPDATED 28-06-2020

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Well, reading back a few pages I had missed that @One and a half did indeed install as a balanced out. What code restrictions/violations do we need to contend with in the US doing this?

tempted..

 

also I see that the recommendation is to keep the Topaz as close to the equipment as possible. Consensus on that? Worried about noise being an issue.

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Thanks @sandyk , I’ll throw in the questions above to @Superdad too, if he has time off assembling the tons of LPS1.2s that we’ve all ordered.

 

question on for @Speedskater - anything particular I need to do to make sure that the circuit containing the Topaz is a Separately Derived System?

 

i assume that the answer has to do with the grounding scheme.

 

thanks all!

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8 hours ago, seatrope said:

Hi all! Just picked up a 5 kVa 0.0005pF topaz from a surplus store, in preparation for adding dedicated lines to my Audio room.

 

The plan is to add two MC 10/2 or 10/3 lines from my basement panel to the music room which lies above the garage. I had a couple of question that I was hoping those more knowledgeable could chime in on. I have a licensed electrician doing the work even though I’m reasonably comfortable with doing outlet and switch work.

 

The Topaz would sit at the end of the basement closest to the music room although in the basement, it is still 30 ft or so away from the music room. It would sit in line with one of the dedicated lines, with the other being a nice comparison for transformer or no transformer.

 

1. Would it be better to run 240V in to the topaz, or 120V? My electrician offered to run 240V line from breaker panel. Not sure which is better- any views? Would doing 240V in reduce the VA rating? I’m guessing not, only if balanced out was used?

 

2. I’ve decided to stick with 120V single ended output as I don’t want to deal with the potential code violations and having to install a GFCI/DPDT switch for balanced, unless someone can convince me otherwise. Anyone here running balanced out 120V from their Topaz?

 

3. Is it a mistake having the Topaz be 30 ft away from final outlet? I’ve seen recommendations that the Topaz be close to the final outlet although I was hoping to not worry about transformer hum having it in the basement.

 

Any input appreciated, especially from the likes of @Speedskater @One and a half @zilch0md @Johnseye @sandyk

All of your contributions have taught me so much!

 

Yeang

 

I don't have any idea what a MC 10/2 or 10/3 is. Something like #6 screw or shoe? A link is fine.

 

The Topaz can be far away or close to the audio equipment, it's up to you, mine is 80' away.

 

1. 240V means no neutral involved and smaller wire needed. Go for it.

2. 120V output is OK. Parallel the windings on the secondary, X4 & the shields are grounded inside the Topaz. A GFCI is needed on the output, considering a 5kVA, an RCBO is better whatever the term is in USA.

3. See 2nd sentence.

 

Tell your electrician to wire 150C wire to the Topaz, they get hot. Topaz recommends 90C, but I don't think it's enough. Mount the Topaz on something really solid, like a metal bedplate or flat concrete, but NOT on timber wall studs with a 2 x 4. Can use solid hardwood, which is bolted to concrete, an alternative.

 

Shielded cable is the best option for your distance, but effectiveness of that cable is best with EMC glands and correct terminating techniques.

 

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Thanks much guys @One and a half and @Superdad

 

MC 10/2 is 10 gauge metallic sheathed Cable with 2 conductors and a separate insulated ground, the more updated version of BX (US terminology).  

 

Ok I’ll ask for 240v in. That’s also balanced wrt the two legs of the household supply. 

 

Can anyone comment on how much potential code violation there is doing a balanced 60-0-60 output?

 

also, @One and a half, how did you have the ground connections set up at input and output?

 

thank you guys so much!

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  • first thing, print out the Middle Atlantic white paper. For link see my Friday 11AM post. (why don't the posts have numbers?)
  • a Topaz is rather quite, but if 30 feet is the best you can, it will be OK.
  • as above, a 240V input has some advantages.
  • I think the Middle Atlantic paper covers wiring Separately Derived System. But basically it's how the Safety Ground wire is attached.
  • A GFCI is needed on the output, considering a 5kVA, an RCBO is better whatever the term is in USA.  In the USA they are all called GFCI's.  They are available as circuit breakers or dual receptacles. They are much more sensitive than RCBO's.
  • There is little to be gained from a balanced 60/60 [120V] line over a Separately Derived System. Because the Ac power supplies don't take advantage of a balanced input.
  • a 5kVA transformer should be wired with two 20A output circuits (including two 20A breakers).
  • what did I miss?
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58 minutes ago, Speedskater said:
  • A GFCI is needed on the output, considering a 5kVA, an RCBO is better whatever the term is in USA.  In the USA they are all called GFCI's.  They are available as circuit breakers or dual receptacles. They are much more sensitive than RCBO's.

For EU and AU use, an RCBO is a combined thermal/magnetic circuit breaker combined with out of balance circuitry on the line and neutral. The US has 5mA  (adjust value please) whereas 30mA is the norm for EU and AU, which I personally think is rather (too) high for out of balance on domestic installations.

The reason to suggest an RCBO is that for a 5KVA transformer, the secondary should be protected against thermals and direct shorts as well as personal safety in the one package.

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Just about the same in the USA.

Ground Fault Circuit Interrupter breakers are a combination of a breaker and a GFCI. While a receptacle is just the GFCI. They are permitted to be used in old two wire systems to add 3 wire receptacles. While in this situation they add human safety but not the basic Safety Ground/Protective Earth function.

While 30mA may be too high, 5mA may be too low. Power conditioners sometimes trip the GFCI.

New US rules are requiring GFCI protection on more and more circuits.

And the newest thing is Arc Fault Circuit Interruption protection (AFCI).  Older appliances drive the AFCI's crazy.

 

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Here is a picture which I hope brings some light to this discussion. This is 10 years old so there might be some additions to it now, but the basic concepts should still be valid.

 

250-30a105un250-73revise.jpg

 

There are two methods to hook up the output of the transformer, and in both methods the "safety ground" wire of wiring connected to the secondary of the transformer is connected to the center tap of the secondary.  In neither case is there a grounded neutral.

 

In the top one the safety ground wire of the primary (input side) is connected to the safety ground of the secondary wiring. This is the way I have done it for the transformer feeding my listening room.

 

In the bottom one the safety ground of the input is NOT connected to the safety ground secondary side, BUT an additional earth electrode connection is added to the safety ground. The NEC states that this earth electrode should be near the transformer. This earth connection is there to prevent the secondary voltage from wandering all over the place, it is not part of the safety system.

 

If I understand what is meant by a "balanced system" it sure looks like both of these systems are in fact balanced.

 

John S.

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@Speedskater I read the middle Atlantic white paper. Very useful but still not quite sure how to translate that into concrete directions wiring the Topaz ground wires. 

 

@JohnSwenson thanks for chiming in. Much appreciated! Can you shed some light on the actual connection configuration of your Topaz? I see your description above but am not sure how that translates for configuration if the ground wire on the input and outputs of the Topaz.

do you have 240V input to your Topaz, John? If you could, would you choose to do so?

 

many thanks to you both for sharing your knowledge!

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1 hour ago, seatrope said:

@Speedskater I read the middle Atlantic white paper. Very useful but still not quite sure how to translate that into concrete directions wiring the Topaz ground wires. 

 

@JohnSwenson thanks for chiming in. Much appreciated! Can you shed some light on the actual connection configuration of your Topaz? I see your description above but am not sure how that translates for configuration if the ground wire on the input and outputs of the Topaz.

do you have 240V input to your Topaz, John? If you could, would you choose to do so?

 

many thanks to you both for sharing your knowledge!

This drawing is the same as in the Middle Atlantic paper, with the transformer connections labelled. Do you need a photo?

 

5a72a4f4bba9e_120Vwiringdiagram.thumb.jpg.773e4a88e07ac434e7078c9aff6e3edf.jpg

 

 

 

 

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First, thanks to many people in this thread - John Swenson, Superdad, and especially Speedskater - for assistance and encouragement that allowed me to have a Topaz transformer serving my audio system circuit in my new home.

 

I wanted to post because I thought this tidbit might be interesting: Because the usual electrical inspector for the area had his son's wedding to attend, the chief inspector for the state came out to inspect the electrical installation, including the transformer. While done to the specifications in the (invaluable) Middle Atlantic paper, the installation was sufficiently unfamiliar to the inspector that he required it to be changed so the transformer draws its power from a wall plug rather than the original hard-wired arrangement.

One never knows, do one? - Fats Waller

The fairest thing we can experience is the mysterious. It is the fundamental emotion which stands at the cradle of true art and true science. - Einstein

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Okay, found the plate photo (click for larger image):

5a7347a1ea69d_Topazplate.thumb.jpg.81d50f2ea19a0b71d4b14c05a9684027.jpg

 

And this post by @One and a half is an invaluable resource for anyone that buys a Topaz tranny:

https://www.head-fi.org/threads/topaz-low-capacitance-isolation-transformers-for-affordably-clean-power.857448/page-9#post-13804344

Great instructions on checking/verifying that all is okay.

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9 hours ago, Jud said:

First, thanks to many people in this thread - John Swenson, Superdad, and especially Speedskater - for assistance and encouragement that allowed me to have a Topaz transformer serving my audio system circuit in my new home.

 

I wanted to post because I thought this tidbit might be interesting: Because the usual electrical inspector for the area had his son's wedding to attend, the chief inspector for the state came out to inspect the electrical installation, including the transformer. While done to the specifications in the (invaluable) Middle Atlantic paper, the installation was sufficiently unfamiliar to the inspector that he required it to be changed so the transformer draws its power from a wall plug rather than the original hard-wired arrangement.

Wow, what a bummer! Funny, people just always need to find a way to add value, even when they can't.

nuckleheadaudio.com

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  • Superdad changed the title to Discussion of AC mains isolation transformers

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