Discussion of AC mains isolation transformers

[Ralf11]

 GTT HOSPITAL GRADE POWER STRIP 6 OUTLETS ON/OFF SWITCH FOR EACH OUTLET 15A 120V

 

$44.xx on ebay

[One and a half]

Stray-Currents, compensating-currents and ground-loops in Transformers

 

This 16 min video explains how 50/60Hz leakage currents 'jump' across from primary to secondaries of isolation transformers. The example in this case was a transformer with a measured by current and LCR meter the value of 160pf. This transformer leaked 13uA at 50Hz, 230V to earth/ground since the ground and neutral are bonded back at the main panel. To compare the Topaz is at least 160/.005 less, so the leakage current is going to be in the same proportion, hardly anything. 

[Johnseye]

1 hour ago, One and a half said:

Stray-Currents, compensating-currents and ground-loops in Transformers

 

This 16 min video explains how 50/60Hz leakage currents 'jump' across from primary to secondaries of isolation transformers. The example in this case was a transformer with a measured by current and LCR meter the value of 160pf. This transformer leaked 13uA at 50Hz, 230V to earth/ground since the ground and neutral are bonded back at the main panel. To compare the Topaz is at least 160/.005 less, so the leakage current is going to be in the same proportion, hardly anything. 

 

Is there a grounded shield between the primary and secondary in the Topaz?

[One and a half]

13 minutes ago, Johnseye said:

 

Is there a grounded shield between the primary and secondary in the Topaz?

There are two of them, one for the primary and one for the secondary. Both are black sleeved and slightly longer to allow for connections to various terminals.. In this photo the shield is connected to X4. If I remember, there's a fair bit of voltage induced on the shield.

 

 

[Elberoth]

Just bought the 5KV 91005-31T model. I should have it installed in 6-8 weeks. I have two identical separate dedicated power lines in my listening room - my plan is to put the transformer on one and compare.

[One and a half]

1 hour ago, Elberoth said:

Just bought the 5KV 91005-31T model. I should have it installed in 6-8 weeks. I have two identical separate dedicated power lines in my listening room - my plan is to put the transformer on one and compare.

Wow, 5kVA would need adding circuit breakers on the output for short circuits, as well as RCD. Upstream use D class circuit breaker to clear the inrush.

[Elberoth]

Can one use TWO identical transformers in parallel to double the VA rating ?

 

My monos have 1.2kVA transformers EACH, so I'm thinking of getting not just one but two 5kVA units for a combined 10kVA - just for the peace of mind.

[One and a half]

10 minutes ago, Elberoth said:

Can one use TWO identical transformers in parallel to double the VA rating ?

 

My monos have 1.2kVA transformers EACH, so I'm thinking of getting not just one but two 5kVA units for a combined 10kVA - just for the peace of mind.

It is possible to parallel transformers primary and secondary, however the sharing won't work out that well, since one transformer is made a  little different to the other and will work less than the other on the secondary side. The regulation is a little different to, so one will feedback the other's voltage in a loop, which will lead to buzzes and hums

 

Recommend to use #1 5kVA for one amp, and #2 5kVA for the other amp. Sources like CD Players, Tuners and DACs can be wired from either transformer, but best if they are on the same supply, there's enough headroom.

 

Computer gear should go on another route to the audio equipment. On its own Topaz or on the primary side of the audio transformers #1 or #2. 

 

Another consideration is the earth. Don't loop them from one to the other device. Arrange all earths in a star structure or like a tree with trunk and branches.

 

[Speedskater]

9 hours ago, Elberoth said:

Can one use TWO identical transformers in parallel to double the VA rating ?

Now that depends on just how identical they are. If they were manufactured the same day, then probably yes.

But even one turn of coil wire difference, will mean they will fight each other.

[Speedskater]

9 hours ago, Elberoth said:

My monos have 1.2kVA transformers EACH, so I'm thinking of getting not just one but two 5kVA units for a combined 10kVA - just for the peace of mind.

Not at all sure what voltage system your equipment operates on. That appears to be a US system unit.

However I believe that you are in Poland?

But if it's 120V then you need 20A breakers protecting the outlets.

A 5kVA transformer can be split to two 20A circuits.

So there is no need to combine two 5kVA transformers and then split it into four circuits.

What is the fuse size on the monos? A 5kVA transformer should be more than sufficent

[Speedskater]

15 hours ago, Elberoth said:

Just bought the 5KV 91005-31T model. I should have it installed in 6-8 weeks. I have two identical separate dedicated power lines in my listening room - my plan is to put the transformer on one and compare.

It would be good to wire it as 240V input with two 120V outputs. With a small breaker box on the outputs.

[Speedskater]

For anyone doing AC system power, the Middle Atlantic white paper should be their reference:

"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

[Speedskater]

20 hours ago, One and a half said:

Stray-Currents, compensating-currents and ground-loops in Transformers

This 16 min video explains how 50/60Hz leakage currents 'jump' across from primary to secondaries of isolation transformers. The example in this case was a transformer with a measured by current and LCR meter the value of 160pf. This transformer leaked 13uA at 50Hz, 230V to earth/ground since the ground and neutral are bonded back at the main panel. To compare the Topaz is at least 160/.005 less, so the leakage current is going to be in the same proportion, hardly anything. 

But, but, but.

In the US system, the secondary  Neutral is required to be connected to the Safety Ground! (or rather vice versa).

[Johnseye]

On 1/25/2018 at 9:35 AM, Johnseye said:

What are the negatives, if any, of using an isolation transformer?  Is there any possibility of one negatively impacting the sound?  In this case let's take the .0005 pF Topaz or similar model as an example.

 

On 1/25/2018 at 10:30 AM, Speedskater said:

a] What size Isolation Transformer?

b] What size audio system?

c] Placement of Isolation Transformer?

d] How is the Isolation Transformer wired?

 

Don't worry about that 0.0005 pF  stuff.

 

Does anyone have thoughts about whether an isolation transformer could produce a negative effect on sound quality?

Another question I have is regarding the frequency, whether only high frequency noise is filtered or if the noise is pushed into a different frequency.  Still unclear on exactly what happens to the noise in the transformer and what frequencies are filtered.

[Speedskater]

Oops, I never did answer that question.

Unless the power amplifier causes the transformer to saturate, then no negative effect.

But unless the transformer is wired as a Separately Derived System, don't expect the great gains that some claim.

And even then, in a good setup with good components, don't expect much if any audible improvement.

But following good engineering practices is always smart.

 

[sandyk]

2 hours ago, Johnseye said:

Does anyone have thoughts about whether an isolation transformer could produce a negative effect on sound quality?

 

 Quite possibly with high powered Class AB Power Amplifiers at high volume levels. .

[Johnseye]

30 minutes ago, sandyk said:

 

 Quite possibly with high powered Class AB Power Amplifiers at high volume levels. .

 

How so? And, do you know what the transformer does with regards to noise at certain frequencies?

[Ralf11]

an isolation transformer could produce a negative effect on sound quality when it is under-sized for the current draw, including transient dynamics - as per above that is most likely when a lot of current demand is required at high SPLs

 

Sandy mentioned Class AB as a Class A will always suck a lot of current even at idle, so the change in demand will be greater with AB

 

BTW, John - earlier, you mentioned your system did sound different with the iso. trans. in the circuit - can you describe the differences with any specificity?

- which types of music?  female vocals, drum strikes, etc.??

[sandyk]

5 minutes ago, Johnseye said:

 

How so? And, do you know what the transformer does with regards to noise at certain frequencies?

 John

 I am not talking about noise . I am talking about instantaneous high power delivery and recovery.

Even the  power boards/mains receptacles used can have a small audible impact in this area with very high powered amplifiers.

Of course if the Isolation transformer is very large and needs to be kept hidden away from  the audio gear because of audible hum problems, that won't natter too much.

 

Alex

[sandyk]

3 minutes ago, Ralf11 said:

an isolation transformer could produce a negative effect on sound quality when it is under-sized for the current draw, including transient dynamics - as per above that is most likely when a lot of current demand is required at high SPLs

 

Sandy mentioned Class AB as a Class A will always suck a lot of current even at idle, so the change in demand will be greater with AB

 

Exactly.

 

Surprisingly , even with big 100W Nelson Pass Class A Monoblocks , even the powerboards used can have an audible effect, as we verified at a listening session a while back. The very expensive Powerboards did sound better than a properly functioning power board from a Bunnings hardware store under non sighted conditions.

 

[Johnseye]

14 minutes ago, Ralf11 said:

an isolation transformer could produce a negative effect on sound quality when it is under-sized for the current draw, including transient dynamics - as per above that is most likely when a lot of current demand is required at high SPLs

 

Sandy mentioned Class AB as a Class A will always suck a lot of current even at idle, so the change in demand will be greater with AB

 

BTW, John - earlier, you mentioned your system did sound different with the iso. trans. in the circuit - can you describe the differences with any specificity?

- which types of music?  female vocals, drum strikes, etc.??

 

12 minutes ago, sandyk said:

 John

 I am not talking about noise . I am talking about instantaneous high power delivery and recovery.

Even the  power boards/mains receptacles used can have a small audible impact in this area with very high powered amplifiers.

Of course if the Isolation transformer is very large and needs to be kept hidden away from  the audio gear because of audible hum problems, that won't natter too much.

 

Alex

 

My transformer is 3x the equipment draw.  I'm not concerned about power delivery or draw.  Audible hum from it isn't a concern.

 

Why I'm digging into this is because I do hear a difference and I'm trying to learn why.  What I hear is a deeper, darker, background.  I guess you call it the noise floor.  This has allowed female vocals to stand out more.  Moon River from Jacintha is a favorite track of mine to use because it's her in a box singing with headphones on.  You can sometimes hear a faint keyboard in the background through the headphones she was wearing to keep time.  With this track her breath in between verses is much more pronounced than before.  Guitar feedback and amp noise (guitar amp on the recording, not mine) is another sound which is more pronounced.  I'll have to listen for drum strikes.

 

What I want to make sure I don't loose is soundstage width, depth and height.  I don't think I have, but the lower noise floor has changed things and I want to make sure I'm not pushing noise into different frequencies with the transformer instead of eliminating it.

 

[sandyk]

25 minutes ago, Johnseye said:

Why I'm digging into this is because I do hear a difference and I'm trying to learn why.  What I hear is a deeper, darker, background.  I guess you call it the noise floor.  This has allowed female vocals to stand out more.  Moon River from Jacintha is a favorite track of mine to use because it's her in a box singing with headphones on.  You can sometimes hear a faint keyboard in the background through the headphones she was wearing to keep time.  With this track her breath in between verses is much more pronounced than before.  Guitar feedback and amp noise (guitar amp on the recording, not mine) is another sound which is more pronounced.  I'll have to listen for drum strikes.

 

 Have you also tried Jacintha singing Danny Boy ?

[Johnseye]

2 minutes ago, sandyk said:

 

 Have you also tried Jacintha singing Danny Boy ?

 

Not yet, I'll check it out.  Thanks.

[sandyk]

1 minute ago, Johnseye said:

 

Not yet, I'll check it out.  Thanks.

 I presume you have a copy of the " Jacintha-Best Of" SACD,  or the 24/88.2 rip of it ?

[Johnseye]

37 minutes ago, sandyk said:

 I presume you have a copy of the " Jacintha-Best Of" SACD,  or the 24/88.2 rip of it ?

 

I do not.  Tidal only.