Discussion of AC mains isolation transformers

[zilch0md]

On 6/1/2017 at 7:27 AM, Duke40 said:

 

TL:DR  I'm not sure if it is floating secondary or grounded secondary, though I do wish I knew.

 

[snip]

 

 

To determine whether an IT has a grounded-neutral or floating-neutral secondary...

 

1) With a load applied to the output of the IT, unplug the IT's input from the mains, so that the load will de-energize the IT.

 

2) Using a multimeter at the unplugged, de-energized output of your IT, test the continuity between the safety ground and neutral. 

 

3) If your meter reads "OPEN", your IT has a floating-neutral secondary (not shorted to the safety ground).

 

    If your meter reads "SHORT", your IT has a grounded-neutral secondary (shorted to the safety ground).

 

[zilch0md]

Thank you, Alex and John, for putting this one to bed, so to speak. I was on the fence, in ignorance.  :-)

[zilch0md]

Having finally taken the plunge to get a Topaz 0.0005 pF (91095-32), I'm very pleased with the results had vs. the Tripp-Lite is500 I'd been using.  Here's my current setup/guide:

 

[zilch0md]

Hi Abtr,

 

I'm always impressed with people who have the DIY skills that you have.  It really hit home, though, when I realized that I've never had a couple of 3300 uF 50V capacitors lying around.    There must be something wrong with me.  

[zilch0md]

1 hour ago, Abtr said:

 

Well, I wouldn’t worry about that. Not too much DIY skills needed for this one. And of course you can always buy a prebuild balanced isolation transformer + DC filter. DIY is much cheaper though. If you have the skills I highly recommend the earlier described configuration. Balanced mains power gives a huge SQ improvement in my system.

 

Are you going to enclose your creation in a case?

[zilch0md]

 

59 minutes ago, Abtr said:

 

Yes. I've ordered this:

https://www.conrad.nl/nl/gss10-universele-behuizing-250-x-200-x-150-staal-aluminium-zwart-1-stuks-520497.html

 

I can imagine the satisfaction of building something like that, more or less from scratch.  I tend to live in a more virtual world - where almost everything is done via a QWERTY keyboard.   :-/

 

I did, however, find myself having to a perform a major restoration of the Topaz 91095-32 Ultra-Isolator that I had ordered from an eBay seller who had described it as "Used" but "Fully functional."  (Ahhemm!)

 

It was only after receiving it that I discovered no less than FIVE problems, any one of which could disqualify the  transformer from being described as "fully functioning."

 

1. The 3-prong plug was missing from the supply cable. (The end of the cord had not been visible in the eBay photos.)
2. The hard-to-find fuse was missing from the fuse holder.
3. The difficult to research (obsolete, now redesigned) cap was missing from the fuse holder.  
4. Late in the game, I discovered the fuse holder itself had the metal remains of a glass-bodied fuse jammed into the bottom of it, preventing insertion of a new fuse (even though the overall length of the new fuse holder is identical to the old and the new cap fits the old holder perfectly, without a fuse). Get out the soldering iron.
5. One of the two outlets refused to accept the full length of any three-prong plug because something was broken off inside that receptacle that could not be extracted and replacement required de-riveting (drilling out) two, threaded spring clips from the old outlet, salvaged for mounting the new outlet to the cover plate.

 

When I contacted the seller, he assured me that he had no idea how it could have left his warehouse with so many unidentified problems (really?), so he offered me a 100% refund if I returned the unit (which would have required my paying for return shipping) or a 50% refund (not applied to what I had paid for the original shipping), if I would agree to keep it, running or not.  

 

Over the next two days I scrambled to affect repairs to all five problems and tested the unit, before accepting replying to accept his 50% refund offer.  

 

I had originally paid only $125.00 + $27.00 shipping - I should have figured the price was too good to be true - but he has 100% positive feedback across the past 12 months, so I figured he just didn't know what it was worth (the 19095-32 usually sells for closer to $250.)

 

I ended up paying...

 

$  62.50 (after the 50% refund)
+  27.00 for shipping
+  7.50 for a heavy-duty 3-prong plug
+  7.34 for a Bussman fuse holder
+  2.38 for two Bussman 10A 250V slow-blow fuses (very difficult to find, locally)
+ 13.21 (for a Leviton 20A commercial-grade outlet)
------------
$119.93  (before mileage to accumulate parts, some solder and the value of my time - to restore it to the condition for which it had been advertised.)

 

I did well, in the end, but for me, the best part of the whole experience has been that great satisfaction of restoring a very capable piece of equipment, the likes of which is no longer manufactured, that was headed to the trashcan, otherwise.

 

:-)

 

 

[zilch0md]

41 minutes ago, Abtr said:

 

Very nice. How does it sound?

 

You never know how much improvement can be made in noise reduction, until you actually make more improvements.  

 

The Topaz 0.0005pF isolation transformer does a much better job of common-mode noise reduction in the higher frequencies, than does a Tripp-Lite is500 isolation transformer, with which I had been perfectly content, for over a year.  The Tripp-Lite's inter-winding capacitance isn't specified, but it's overall construction is identical - 500 VA, two outlets, a grounded-neutral secondary, with a Faraday shield, but my Oppo Sonica DAC, which uses the "latest and greatest" ESS chip, sounds much cleaner in the highs, when powered by the Topaz vs. the Tripp-Lite isolation transformer - especially when listening with my LiPo-battery-powered headphone amp and the highly resolving and therefore, unforgiving, Sennheiser HD 800 headphone.  

 

Before taking the plunge with a Topaz 0.0005 pF transformer, the Tripp-Lite really had made a difference that could easily be tested by taking it in and out of the Sonica DAC's power chain, while adjusting a particular TRIAC dimmer switch, that's located in our dining room, to about 50% brightness.  The Tripp-Lite made an obvious reduction in the noise floor, with or without the noise-generating dimmer switch - but it just can't compete with the Topaz 0.0005 pF performance.  

 

Quoting a paragraph from this page: http://www.mastec.co.nz/JST/PK8.html

 

"With all transformers, stray capacitance, called inter-winding capacitance, can exist between the windings. It is via this inter-winding capacitance that [incoming] high frequency [common-mode] noise [from the mains] can couple through to the secondary winding. However, when a grounded [Faraday] shield is used to separate the primary and the secondary windings, the inter-winding capacitance is significantly reduced. This effectively increases the impedance (resistance) of the coupling path and therefore reduces the amount of high frequency [common-mode] noise that can couple through to the secondary winding."

 

Thus, the lower the inter-winding capacitance, the greater the reduction of high frequency common-mode noise.  

 

I wish I had heeded Jon Swenson's very similar words on this subject, a long time ago, but I was too proud of my Tripp-Lite setup to acknowledge that something better could be out there waiting for me.

 

The Tripp-Lite transformers only claim a 1000:1 to reduction in common-mode noise (-60 dB), where the Topaz model numbers ending in -31 (which have power cords and outlets) or -32 (which have screw terminals) - both of which have no more than 0.0005 pF capacitance at the various VA ratings, all the way out to 20kHz - delivering a 20,000,000:1 reduction in common-mode noise (-146 dB).

 

Let me tell you, it's easy to hear a difference between -60 dB of high-frequency noise reduction and -146 dB.  (My Tripp-Lite is500 is powering my flatscreen TV, now, but this has me wondering if I shouldn't run out and find another Topaz!  :-)  And maybe one for my WiFi router, while I'm at it!  :-)

 

There is, no doubt, a difference in how the Faraday shields are constructed relative to the primary and secondary windings, that sets these Topaz models apart, even from some other Topaz models they made, which have higher capacitance, and thus, less common-mode noise reduction in the high frequencies.  

 

CA member "archtype," who encouraged me to take the Topaz plunge, compared a 0.005 pF Topaz to a 0.0005 pF Topaz and found the difference to be readily discernible - especially in the highs.

 

You have to hear it to believe it. (A trite statement, but true. YMMV, depending on how clean your mains power is to begin with, of course. ) 

 

Unfortunately, by beating this drum, the Topaz transformers are becoming all the more rare as hens' teeth.  On the flip side, many electrical supply houses, don't realize what they have - they will sell a -31 or -32 model, expecting no premium over the higher capacitance model numbers.  

 

Also keep in mind that these same model numbers were used in later years by MGE and Daitron - so don't confine your searches to only Topaz.  Here's an MGE brochure that covers the specs and gives the model numbers for all of the 0.0005pF  transformers (ending in -31 or -32):

 

MGE specs:

 

http://www.pacificparts.com/vends/mge/images/t1.pdf

 

Daitron specs:

http://daitronglobal.com/products/power/power-supply-transformer.html

 

Happy hunting!  :-)

 

Mike

[zilch0md]

Yup!  The Topaz -31 models have screw terminals an the secondary can be center-tapped for balanced output.  

 

I think I'll go another year assuming my unbalanced Topaz is giving me the lowest noise floor possible.  Then I can upgrade, rave about it and let Speed Racer and a couple of other guys tell me, "I told you so!"   :-)

 

Just kidding, but I really do like to pace myself.  The journey is half the fun!

 

 

[zilch0md]

On 11/30/2016 at 4:13 PM, JohnSwenson said:

There have been several posts recently in this and other threads where it has been stated that the common mode noise attenuation of an isolation transformer depends on whether the secondary is connected to safety ground or not.

 

This is simply not true. It is easy to test this. Take any transformer (it doesn't have to be an expensive iso transformer, any transformer will do) it can be anything as long as it is a true transformer, not an autoformer. For the test a simple 120V to 12.6 V transformer will do fine. You need a signal generator and a scope, set the generator to either 200 or 240 Hz. If in an area with 60Hz AC line use the 200Hz, if in an area with 50Hz AC line use 240Hz. You want something that is NOT a multiple of the line frequency. You will need a safety ground. Take it off a chassis that is grounded, or the green wire of a power cord etc. We will NOT be using the hot or neutral, just the safety ground.

 

The definition of common mode noise is that it is noise that is the SAME on both wires of the primary of the transformer relative to some other reference point, usually the safety ground. So we will deliberately inject a common mode signal into a transformer and see if we can detect it on the output. So connect the negative of the signal generator to safety ground, and the positive to BOTH primary wires of the transformer. Nothing else connected to the primary wires, DO NOT connect the primary wires to the AC line. You have been warned, I will NOT be responsible for what happens to your signal generator if you do that!!!

 

Now use a scope to measure if you see any of the input signal on the secondary wires. But first we have to figure out what we are testing. Are we testing common mode noise on the output (common mode in to common mode out) or differential (common mode in to differential out). Nobody ever mentions this distinction when talking about the subject. So lets measure both.

 

But second we have to figure out where safety ground comes into this. The problem is that most scopes have their "gnd" of the probes connected to safety ground, which makes it very difficult since we are testing how the system behaves relative to safety ground. So the best way to do this is with an isolating differential probe.

 

Then it is simple, use the differential probe to measure between the two secondary wires, this measure the differential output, then measure between safety ground and one wire of the secondary, then between safety ground and the other. THEN connect the safety ground to one of the secondary wires and repeat the three tests.

 

THIS will test whether common mode attenuation of a transformer has anything to do with how safety ground is connected.

 

John S.

 

Thank you, John, for boldly yet graciously setting me (and others?) straight regarding the fact that isolation transformers with floating-neutral secondaries provide Common-Mode noise reduction, just the same as those with grounded-neutral secondaries.

 

It has taken me several months to get around to investigating this further, but I'm now convinced you are correct.  (I'm eating some humble pie, here, but I'd much rather learn and communicate the truth than mislead other readers.)  

 

Here's a lengthier retraction of my previous contention on this topic:

 

 

[zilch0md]

Hi Abtr,

 

This is my current understanding, eager for correction, where appropriate...    :-)

 

Whether starting out balanced (with the secondary grounded from a center tap) or unbalanced (with the secondary grounded at the neutral wire), if you then float the secondary, you will still get the same amount of common-mode noise reduction as you had before floating the secondary, with the only difference being that if you started out balanced, with a grounded center tap, you will have just converted it to an unbalanced transformer with a floating Secondary.  

 

So... In your experience, you have essentially said you prefer the sound of an ungrounded (floating) secondary to the sound of a balanced secondary (which, by definition, is grounded via the center-tap.)

 

I suspect the reason you prefer the floating secondary is because you've got a ground loop between one or more components that gets attenuated somewhat when you float the secondary that they are all sharing.

 

I'm not a big believer in balanced power, perhaps because I so strongly believe that the "magic" of common-mode noise reduction occurs via the Faraday shield that inhibits capacitive coupling from the Primary into the Secondary.  In other words, what work is left to be done, by the time the 60 Hz AC power has passed unharmed from the Primary through to the Secondary (via magnetic induction), stripped of any DC signals (Common-Mode noise) that have, at that point, already been attenuated 20,000,000:1 (-146 dB), in the case of the 0.0005 pF Topaz units?  Whether we ground the secondary at a center tap (balanced) or ground it at the Neutral (unbalanced), the Common-Mode noise that came into the Primary on the Mains has already been diverted to ground by the Faraday shield(s), converting any residual common-mode into transverse-mode (normal- or differential-mode) noise - which most 1:1 transformers would just pass into your loads, but the Topaz Ultra-Isolators have some kind of double or triple Faraday shield configuration that manages to provide -65 dB of normal-mode noise reduction without using modern filter circuits (i.e. Y-Caps at the input, an X-Cap across the outputs (for modest voltage surges) or one or more serially arranged MOVs across the inputs or outputs (for heavy surge protection).  Keep in mind that MOVs actually create some common-mode noise when suppressing normal-mode transients, and the Topaz can already absorb a lot of surge, at least until the voltages are high enough to saturate the transformer and penetrate the insulation of the windings.  :-)

 

OK, I got into a bit of a ramble, there, but to answer your first question...  There are two reasons for putting only one component (one load) on a transformer with a floating secondary:   1)  If you were to plug two components into one floating-secondary transformer, and the first component somehow shorted Hot to the case, you would be fine, until, by chance, at some point in the future, the other component shorted Neutral to its case -AND- you happened to touch both cases at the same time - allowing hot to flow into one hand over to the other hand.  The probability of this happening is extremely low, but if the two components were plugged into the same transformer with a grounded secondary, you wouldn't have to worry about the improbable possibility.  2)  Much more probable is the chance that you've got a DAC, CD Player, Blue-Ray player or other microprocessor-equipped component that's dumping digital "hash" common-mode noise back onto the power cord, where it could pollute the power going to any other component that's plugged into the same outlet, power strip, or transformer.  You could also have one or more components that are equipped with SMPS, which are also known for dumping noise back onto the mains.  

 

A well-made analog component, with a linear power supply, like an amplifier, is more likely to be a victim than a culprit, when sharing a power strip with other components, so these non-backwashing components can be plugged directly into a grounded-secondary transformer (whether balanced or unbalanced - your choice), but all the backwash suspects (DACs and other digital sources, plus anything with an SMPS) should be segregated from each other and from the analog components, by using floating-secondary transformers that themselves plugged into the one, larger capacity, grounded-secondary transformer.  Each of the floating-secondary transformers will prevent any backwash noise from polluting other components - the common-mode noise attempting to flow upstream will be attenuated as it attempts to get from the secondary coil to the primary coil. (A transformer with Faraday shield can attenuate common-mode in both directions.)   

 

It will also break ground loops - even if you have signal cables running between components - i.e. between a DAC and an amp - no loop can be formed to get back to a shared power ground when they are each plugged into independent, dedicated, floating-secondary transformers. Remember, each component with a three-prong plug still has a safety ground that goes all the way back to the wall outlet, through both transformers, per code, but neither the Hot nor the Neutral supplying power to each compoent is connected to that safety ground - at least not within their respective floating-secondary transformers.  Joy!

 

You can, however suffer some leakage currents, caused by voltage differences coming out of their independent transformers - i.e. when an amp is plugged into the powerstrip of the big grounded-secondary transformer, but the DAC is plugged into a floating-secondary transformer that has been inserted between the DAC and the big transformer - the amp and the DAC will see different voltages, in which case, if you want to discourage leakage currents, you can really pull out all the stops and insert a high-bandwidth signal transformer, such as one of these, made by Jensen:

 

https://www.amazon.com/Jensen-CI-2RR-IsoMax-Isolator-Jensen/dp/B00ASVWYCS

 

or

 

https://www.amazon.com/Jensen-DM2-2XX-Iso-Max-Isolator-Jensen/dp/B00ASVWYO6 

 

But to start with, I would encourage you to just ground the secondary of your main transformer (unbalanced is my preference), then insert Hammond 171 Series transformers (which range from 100 VA to 1000 VA and have floating secondaries) or a B&K Precision 1604A, ahead of each digital component or those with SMPS.  Give that a try and see if it doesn't sound better than plugging everything into your single, floating-secondary transformer.

 

I would, however, caution you to use a Kil-A-Watt to measure the voltage going into each component when operating.  Each transformer in a series will likely increase the voltage that came into it, even though they are technically 1:1, until you fully load them to their rated capacity - which you really don't want to do, especially for power amps, because you want to leave "headroom" for the transformer to supply instantaneous peak currents on demand, above rms current requirements.  

 

If stacking two 1:1 transformers serially has your component seeing more than about 127V, you should consider getting an APC LE1200 voltage regulator, and setting it to an output voltage of 107V (the lowest of three available settings.)  Plug your big grounded-secondary transformer into the voltage regulator, then the smaller floating-secondary transformer, and you'll measure something closer to 120V at the second transformer's output.  :-)

[zilch0md]

Here's a great article about Floating vs. Grounded output:

 

http://www.aptsources.com/resources/pdf/Floating Output.pdf

 

[zilch0md]

On 8/29/2017 at 4:31 PM, Cornan said:

 

Great post Mike! ?

 

This part is why I only use power supplies with safety ground isolated from the DC output negative/chassi.

 

 

However, do not fall in the trap that SMPS is the root of all evil. SMPS have its advantages and draw-backs just as LPS. It just about dealing with those draw-backs and use the advantages! 

Here is some interesting info from Benchmark in the subject.

 

https://benchmarkmedia.com/blogs/application_notes/152143111-audio-myth-switching-power-supplies-are-noisy?utm_source=Benchmark's+Application+Notes&utm_campaign=ebfa3d2c6f-Application_Note_2017_8-4-17&utm_medium=email&utm_term=0_7c8c792ee5-ebfa3d2c6f-198221561

 

 

Did I say that I have only SMPSs in my setup? All floating and with AC & DC starquad cables. It sounds awesome!

?

 

Micael

 

 

Hey Micael!

 

I'm sold on star quad cables - thanks!  That's a great video.  Notice however that he is not testing for any backwash onto the power line from the DAC 1 (with the big toroidal transformer in its LPS) vs. the DAC 2 (with the much smaller SMPS transformers, and thus, much smaller magnetic fields affecting his cable measurements).   

 

In other words, there would be no "audible" difference in magnetic field strength, between the power supplies of the DAC 1 and DAC 2, if the standard vs. star quad cables were moved farther away from the DACS, instead of sitting them right underneath their transformers.

 

Which means...  The only thing left to worry about, when comparing SMPS to LPS is the backwash that the SMPS might be putting onto the power line - which he makes no attempt to measure, in that video.

 

Again, I am convinced that the star quad cables are a winner, but I think your choice to use floating-secondary isolation transformers on each of your SMPS-equipped components is more likely to offer noise reduction improvements than the use of star quad cables - unless you've got your cables in very close proximity to magnetic fields or other sources of RFI/EMI. 

 

Radiation falls off with the square of the distance.  Notice how quickly the hum vanishes in that video, when he moves those various chargers away from the standard cable.

[zilch0md]

 

On 9/7/2017 at 2:09 AM, One and a half said:

 

[snip]

 

BTW I found these great graphs on the performance of the Topaz transformers. Some very impressive results. So why on earth were these discontinued?

 

 

 

For real!

 

 

[zilch0md]

9 hours ago, One and a half said:

Right, thought so, there's an error on the drawing. The H's are screwed up.

 

Left to right, the sequence should be H1, H3, H2, H4 as the photo from Speed Racer. The flyer indicates H1, H2, H3, H4 which is wrong!! It's the Paris in the the Spring type scenario. See the double the?

 

The X's are correct. 

 

Do you have a 12V or 16V AC wall wart to sacrifice?

 

 

 

Which drawing (or flyer) is incorrect?  

 

I haven't seen anything wiring diagrams for the Topaz -31 models that show this incorrect sequence on the H terminals.  (Or maybe I have and didn't notice.)  In any case, I would like to know which resources is in error.

 

Thanks!

 

Mike

[zilch0md]

6 minutes ago, One and a half said:

EEEUWW the CA editor went downhill there.

 

Try : My eyes play up couldn't see the markings that well. The pdf linked in this post is correct. 

 

Yes, the "H1," "H2," etc. are difficult to read in that PDF, but it's correct.    

 

Thanks for this follow-up!

 

Mike

[zilch0md]

On 9/10/2017 at 11:46 AM, Cornan said:

 

Hi Mike!

 

Yes, the starquads do not cure anything with SMPS leakage current. That is solely due to the floating SMPS (safety ground not passed through to the DC negative or chassi) and the isolation transformer with floating secondary. What the amazing starquad AC mains and DC cables do is to let you hear those differences much better than with other cable types that I have tried. However, if you have'nt dealt with the SMPS backwash by using dual floats (floating SMPS into a IT with floating secondary) the starquads will reveil that very clearly too! Starquads will simply give you a brutally honest result since it is very efficient in rejecting EMI and overall very immune to ouside noises. They are especially effective against outside AC magnetic fields.

For every cable I have changed out it have benefit the overall SQ quite a bit in my two setups. I am now on a mission to change out all my cables to starquads. I have currently orders on a starquad wired power distributor and a starquad USB cable with JSSG Faraday type shield. We will see where that ends up!  ?

 

Micael

 

Micael, your enthusiasm is so infectious!   :-)

 

I've started my Star Quad collection with this very affordable pair of RCA cables to run between my DAC and amp:

 

https://www.amazon.com/1-5-Foot-Cable-Pair-High-Definition/dp/B01ALHUSYE

 

We shall see...  er... hear what they can do...

 

:-)

 

Mike

[zilch0md]

1 hour ago, Cornan said:

 

That´s pretty hot!

It seems that it must be something with the wiring then. Not many could answer that subject better than @One and a half

Here is a Hammond overheating trouble shooting link that might come in handy?

https://www.hammondpowersolutions.com/innovation/overheating/

 

 

That's a comprehensive list, for sure.

 

I think this item would tell you a lot regarding the "health" of your Topaz:

 

Check no load current.

If no load current is high (varies with transformer efficiency but no load current is typically less than 2-3% of total kVA), inspect the core and coils for damage. In most cases you will not be able to inspect the insulation between the core and coil without returning to the factory for testing and disassembly. If there is a short between the core and coil, the unit will have to be replaced or repaired.

 

@spacexpert , if you could measure the current consumed by the transformer when it's not loaded, given how much heat it's producing, I suspect it will be a lot higher than 2-3% of the total kVA rating.   In which case, despite all the excellent help from @One and a half, the way it reads, above, I suspect the transformer would be a lost cause.

 

Not to rub salt in your wounds, but rather, to establish a point of reference for this subject of overheating...

 

With my 500 kVA Topaz 19095-32 having been energized for several weeks, seated on the floor of my den, while not loaded, my laser thermometer measures a maximum (peak hold) temperature (at a couple of spots on top of the core) of 40.6 C (105.0 F), with an ambient temperature (of the flooring, 30 cm away from the transformer) of 22.8 C (73.0 F).  

 

That's a difference of 17.8 C (32.0 F) between ambient temperature, at floor level, and the top of the transformer core.

 

[zilch0md]

12 hours ago, Speed Racer said:

I have those exact cables....and found the Blue Jeans RCA cables to be quieter and sound better.

 

Thanks for your advice!  I've successfully canceled the order for those star-quad RCA cables and have instead ventured into star-quad by placing an order for a GhentAudio star-quad DC power cable - which I'll use with my USB Regen.  I have a Blue Jeans Coaxial cable that rocks, by the way.  They make great stuff at great prices.  

[zilch0md]

6 hours ago, spacexpert said:

I think so too.  I will have to buy another one, shipping is a nightmare.    

 

I feel for you.  At the risk of discouraging you, but in the interest of sharing that you are not alone...   My Topaz 19095-32 was purchased from an ebay seller who described it as "used, fully functional," when that could not be any further from the truth.

 

Consider this list of FIVE undisclosed problems that I had to fix myself - any one of which disqualified the Topaz  from being described as "fully functional" - listed in the sequence of discovery after unpacking it: 

• The 3-prong plug was missing from the supply cable. 
• The hard-to-find fuse was missing from the fuse holder.
• The difficult to research (obsolete, now redesigned) cap was missing from the fuse holder.
• The fuse holder had the remains of a fuse jammed into the bottom of it, preventing insertion of a new fuse, even though the overall length of the original fuse holder was the same as the new fuse holder I'd purchased to obtain only the cap.  The same fuse fit the new fuse holder perfectly, so I had to de-solder and replace the defective fuse holder in addition to replacing the missing cap.
• One of the two outlets in the original receptacle refused to accept the full length of any three-prong plug I attempted to insert, because something was actually broken off, at the bottom of the Neutral slot! (Much like the fuse holder had something jammed into the bottom of it.)  And replacement of the outlet required de-riveting (drilling out the rivets) two, threaded spring clips, for mounting the new outlet to the cover plate with the original machine screws.

How could so simple a device be so messed up, yet described as "fully functional," with no disclosure of any of these five show-stopper issues? 

 

I managed to negotiate a 50% refund from the seller AFTER I had determined that I had restored it to "fully functioning" condition and tested it.  I never told him I had already fixed everything.  I accepted the 50% refund on the understanding that I would keep it, "as is."  
 
This was not a case of negligence or incompetence, but in the end, I feel really good about having rescued a beautiful piece of no-longer-made equipment from the trash can.  It's very happy in its new home.  

 

:-)

 

Mike

 

 

 

[zilch0md]

10 hours ago, One and a half said:

Temperature and loading results 1000VA 0.001pf 91001-21 transformer.

 

Ambient : 22.7C 

Idle :

Consists of energising 1000VA Equitech transformer and MPD-3 DAC which is on 24/7 . Primary current 0.47A, 239V input 112.33VA.

Lamination temperature : 37.5 C

 

On Load : Ssytem 1 and System 2 on, low level music, maybe 1 Watt output

1.43A, 239V, 342VA input. 

 

Left on load for an hour, Lamination temperature : 38.3 C, Ambient Temperature 24.4 C

 

Temperature readings with a contact K type thermocouple. 

 

Unloaded, you've measured a difference of 37.5 C - 22.7 C = 14.8 C, relative to ambient.

 

Quoting my earlier post:

 

"That's a difference of 17.8 C (32.0 F) between ambient temperature, at floor level, and the top of the transformer core."

 

So, my transformer runs a little hotter than yours, apparently. 

 

 

[zilch0md]

17 hours ago, tims said:

Anyone please comment if this DIY project from 2005 - the Felicia balanced power conditioner would help with leakage currents as discussed?

 

Schematic here:

Secondaries are running at 15vAC

 

Felicia Balancing Power Conditioner

 

"The principal benefit of the Felicia conditioner, (like the Jon Risch SQ&D Iso Trans project upon which the Felicia was based -
http://db.audioasylum.com/cgi/t.mpl?f=tweaks&m=43988) is power conditioning. Specifically, its very effective at eliminating differential (transverse) mode noise, in addition to attenuating the easier to deal with common mode noise.
The benefits of making the conditioner provide balanced (technical) power are real for components that have a grounded chassis (they're also there for certain other components without 3 prong grounded plugs whose chassis are grounded to other components via various circuitous routes). Specifically, that benefit is minimization of reactive leakage currents to the chassis which causes noise, and in its most extreme form, ground loop hum."

 

That's a very interesting contraption.  I know just enough to say that all those X-Caps would indeed reduce normal-mode noise, but it seems like overkill, when a Topaz can provide -65dB of normal-mode attenuation all by itself (in addition to -146dB of common-mode attenuation.)  Also:  Common-mode noise sources tend to be more constant, where normal-mode sources tend to be intermittent or even infrequent.

 

See the last page of this pdf:

 

http://www.murata.com/~/media/webrenewal/products/emc/emifil/knowhow/26to30.ashx

 

And:  http://www.controlledpwr.com/whitepapers/electrical_noise_attenuation.pdf

[zilch0md]

On 9/12/2017 at 8:18 AM, zilch0md said:

 

Thanks for your advice!  I've successfully canceled the order for those star-quad RCA cables and have instead ventured into star-quad by placing an order for a GhentAudio star-quad DC power cable - which I'll use with my USB Regen.  I have a Blue Jeans Coaxial cable that rocks, by the way.  They make great stuff at great prices.  

 

I realize this thread isn't the right place for discussion of cables, but I feel compelled to correct some misinformation that has been posted here.

 

 l am still waiting for the Ghent star-quad power cable to arrive, but I've been studying the subject of star-quad cables and have concluded that they are ONLY useful for incoming noise immunity when the signal voltage is quite low - as with microphone cables or line-level signals (i.e. RCA interconnects).

 

When the voltage on the line is higher, as with speaker cables and power cables, the advantage is actually reversed - star-quad cables will inhibit emission of magnetic fields from the cable!

 

Quoting this Canare Star-Quad document:  "Canare Star Quad is designed for use with microphones but is also excellent for all line-level signals (e.g. mixer to power amps)."  AND "The signal generated by a microphone during quiet periods can be very low in level, -70dB to -120dB (0.3 millivolts to 1 microvolt). The cable that must carry this signal to the mixer is very sensitive to Electromagnetic Interference (EMI), Radio Frequency Interference (RFI) and electrostatic coupling of hum and noise."   

 

Note the conspicuous absence of any recommendation for using their star-quad cables for purposes other than microphone or line-level signals.

 

Quoting Blue Jeans Cables:   "Speaker cable is a bit different from a lot of the interconnect cables we handle, in several respects. Because speakers are driven at low impedance (typically 4 or 8 ohms) and high current, speaker cables are, for all practical purposes, immune from interference from EMI or RFI, so shielding isn't required." AND "Canare 4S11 is a "star quad" 14-gauge cable, with four conductors together in one outer jacket; it is popular for bi-wiring (where separate wires run to each of four speaker terminals, two of which drive the high and two of which drive the low-frequency elements of the speaker assembly). When conventionally wired [with two conductors shorted together for each channel], star quad speaker cable has the advantage of reducing the EM field around the cable, which will tend to diminish the effect of the signal in the speaker cable upon nearby interconnects--though this is not, in most applications, a significant concern."

 

They're saying that you can reduce the outward emission of electromagnetic fields from a speaker cable by using star-quad cable, but that there's little concern for doing this.  Again, note the absence of any claim for improving immunity from inbound noise when star-quad is used as a speaker cable (not as a microphone or line-level cable).

 

Quoting a Wikipedia article:   "The combined benefits of twisting, differential signalling, and quadrupole pattern give outstanding noise immunity, especially advantageous for low signal level applications such as long microphone cables, even when installed very close to a power cable."  AND "While the above discussion focuses on preventing noise from getting in (e.g. into a microphone cable) the same star-quad quadrupole configuration is useful for audio speaker cable,^[10] for split-phase electric power wiring, and even for open-wire star quad transmission line. In these cases, the purpose of the star quad configuration is reversed. The star-quad geometry cancels the magnetic fields that are produced by the two pairs of conductors. This cancellation reduces the magnetic emissions of the cable."

 

I therefore seriously doubt there is any advantage to be had by using star-quad cable for anything other than weak, low-voltage signals.  It's especially useful with weak signals running in close proximity to devices that are emitting electromagnetic interference, as seen in the YouTube video where energized transformers are placed directly on top of microphone cables.  With higher-energy signals, it would be a rare situation in which there's anything to be gained by reducing the outward emission of magnetic fields from the cable. 

 

Then again:  Why not use star-quad everywhere?  We get inbound noise reduction with low-level signals (very advantageous) and outbound noise reduction with high-level signals (not so advantageous).  There's only one disadvantage that I've read about - in the Wikipedia article: Roll-off of high frequencies, but this only happens with really long cable runs.

[zilch0md]

Thanks Cornan.  Reading John's posts again (quoted above), I have no contention with his statement that the star-quad configuration does a great job of reducing vulnerability to externally applied EMI.  None of the article I quoted say otherwise.  

 

What's being debated here is the degree of concern one must have for blocking external sources of EMI (by using star-quad cables) for applications other than microphone cables and line level cables - where weak signals are far more vulnerable to external EMI than stronger signals, especially in long cable runs, as with microphone cables on a stage.

 

Both Canare and Blue Jeans discount the value of using star-quad cables for higher voltage (higher current?) applications, except when the goal is to limit magnetic emissions outward from the cables themselves (all of which is consistent with the quoted Wikipedia article.)

 

In the end, it's possible that Canare and Blue Jeans Cable and the contributors to that Wikipedia article are simply underestimating the noise-reduction benefits of using star-quad cables in applications other microphone and line-level cables and, as I mentioned previously, it probably can't hurt to use star-quad cables everywhere, even though the benefits are allegedly less valuable or, at least, less cause for concern, with some applications.

 

[zilch0md]

4 hours ago, Forehaven said:

Thanks for the help guys.  I bought a 1kV Elgar, model HIT .001R

 

Sounds like I'm kind of screwed with the noise.  Unfort. I live in a 1905 built home, with old....circa 60's?...wiring.  Plus, I live on a street surrounded by lg multi residential bldg's.  

 

Are there actually IT's that are silent??

 

My 500VA Topaz 19095-32 is also pretty close to silent.  I have to put my ear close to it to hear anything.  It is not a toroidal transformer, though.  Then again, there are some people out there with noisy Topaz transformers (i.e. John S.) 

 

I really think the quality of the incoming AC mains power is a big factor, no matter what type of transformer you are using - and that incoming quality can fluctuate throughout the day.  

 

There are are a lot of people out there who have silenced noisy transformers that are inside their various audio components, just by inserting a DC blocker ahead of the their A/V systems - here in the States, too, not just elsewhere.  See the reviews of the relatively affordable Emotiva CMX-2, which is more than just a DC blocker.  It's the people who had noisy transformers who are writing the most positive reviews of the CMX-2 - so, I'm pretty sure it does a good job of DC blocking, even if it only does a fair job of CM or DM noise reduction.

 

If I had a noisy transformer, even a noisy Topaz, I would try putting the CMX-2 in front of it.  I definitely would not put anything like this (containing MOVs for surge protection) in between my Topaz and the power strip into which all my gear is plugged.  Surge protectors, if really needed, should be placed ahead of the Topaz - which is exactly where you want a DC blocker, too.

[zilch0md]

On 9/12/2017 at 8:18 AM, zilch0md said:

 

Thanks for your advice!  I've successfully canceled the order for those star-quad RCA cables and have instead ventured into star-quad by placing an order for a GhentAudio star-quad DC power cable - which I'll use with my USB Regen.  I have a Blue Jeans Coaxial cable that rocks, by the way.  They make great stuff at great prices.  

 

Since receiving it three days ago, the reduced inductance of my Ghent Audio star-quad DC power cable has been lowering the voltage drop that would otherwise be suffered in supplying 7.0V DC to my USB Regen from my el cheapo LPS - making no audible improvements whatsoever as it is incapable of offering any significant reduction in EMI thanks to the voltage being so high (relative to voltages seen in microphone cables and line level interconnects, where star-quad cables can make a huge difference.)

 

So now, with the exceedingly well-made Ghent Audio DC cable making no audible improvements, I'm going to select and order some star-quad RCA interconnects, where the line level voltages are more susceptible to EMI - and as long as the interconnects are short, as mine will be, the star-quad disadvantage of increased capacitance shouldn't be a problem.