Topaz Low-Capacitance Isolation Transformers - for Affordably Clean Power

[L0rdGwyn]

Well I made a late-night hardware run. I replaced the Schuko plug and rewired the secondary side for 120V using the included jumpers, how convenient is that. I also spotted the noise suppression capacitor, it is mounted behind the panel in the photo, wired in parallel across X1 and X4, the two white wires. Haven't taken the panel apart yet to see its value, will have to investigate if it needs replacing.

Plugged the sucker in and measured voltages on the output. I am getting 124V across hot and neutral and all of the continuity readings check out. I know the secondary is floating, but I measured the hot and neutral voltages to ground as well, 44V between hot and ground, and 74V between neutral and ground.

 

[L0rdGwyn]

Well all appears to be working as intended. I plugged in my amp (Glenn OTL), PC, and computer monitor. As expected, the transformer does have a mild "in the room" hum. It can also be heard on my amplifier at close to max volume without music playing (ear-bleeding volumes). Tomorrow I think I will do a little A-B listening to see if the noise suppression is clearly audible.

The next step is to see if a balanced wiring setup is going to suit my needs and work with my gear. Pretty keen on giving it a try, not so keen on damaging something that is incompatible.

 

[L0rdGwyn]

Did some A-Bing this morning. So as to remove other variables, I listened with my laptop and USB powered DAC so the only thing connected to the mains was my amplifier. Listening was done with the ZMF Auteur and Glenn OTL. I swapped back and forth powering the Glenn OTL from my old Furman PST-8 and the 91002-31T.

I like the track "Not Okay" by SOPHIE for testing. This electronic song is not for the faint of heart, it is intense and dissonant, but it will put any amp through its paces with some very, very complex passages. Took a few back-and-forth's to confirm what I was hearing. Yeah, there is an improvement in sound. There is a sort of veil that is lifted allowing more microdetail to be gleaned from the recording, better definition of space and a blacker background, better air on good recordings.

Funny as this noise is not something you can truly hear. It isn't like, "oh there it is, now its gone," but the sound is noticeably more chiseled and well-defined with the 91002-31T.

While it is easy to pick out on headphones, I wonder if the same benefit is easily heard on a two-channel system, I'll have to experiment and find out.

Well I am sold. Now to try balanced.

 

[Zachik]

Did some A-Bing this morning. So as to remove other variables, I listened with my laptop and USB powered DAC so the only thing connected to the mains was my amplifier. Listening was done with the ZMF Auteur and Glenn OTL. I swapped back and forth powering the Glenn OTL from my old Furman PST-8 and the 91002-31T.

I like the track "Not Okay" by SOPHIE for testing. This electronic song is not for the faint of heart, it is intense and dissonant, but it will put any amp through its paces with some very, very complex passages. Took a few back-and-forth's to confirm what I was hearing. Yeah, there is an improvement in sound. There is a sort of veil that is lifted allowing more microdetail to be gleaned from the recording, better definition of space and a blacker background, better air on good recordings.

Funny as this noise is not something you can truly hear. It isn't like, "oh there it is, now its gone," but the sound is noticeably more chiseled and well-defined with the 91002-31T.

While it is easy to pick out on headphones, I wonder if the same benefit is easily heard on a two-channel system, I'll have to experiment and find out.

Well I am sold. Now to try balanced.

Following this thread, my main concern is the hum from the Topaz itself...
You did comment yesterday that there IS a hum. I am curious how far from the Topaz do you sit, and whether you can still hear it or not?
I am also curious after you place it in a chassis how would that affect said hum.

 

[L0rdGwyn]

Right now it is on the left side of my desk, about 3-4 feet away from me. In a silent room with open back headphones, it could probably be heard with quiet music (e.g, classical, chamber music, acoustic). I suspect that if it were placed in a chassis, it would be significantly muted, others here can comment on that I am sure.

Once the transformer is wired in a balanced configuration, I suspect that the hum will be muted further still or go away completely, that seems to be the experience of many owners in the thread. I'm probably going to wire it up in balanced later today, this will be going in my stereo eventually, so I would prefer the hum to be minimized, it will be less of an issue with headphone listening.

 

[Zachik]

Right now it is on the left side of my desk, about 3-4 feet away from me. In a silent room with open back headphones, it could probably be heard with quiet music (e.g, classical, chamber music, acoustic). I suspect that if it were placed in a chassis, it would be significantly muted, others here can comment on that I am sure.

IF added to my setup, it would probably live on the floor, 5-6 feet from when I sit. Can you still hear it if you move 2-3 feet away from the Topaz?

Once the transformer is wired in a balanced configuration, I suspect that the hum will be muted further still or go away completely, that seems to be the experience of many owners in the thread.

Interesting. What is the downside of balanced?
For the record, I have never heard that power can be balanced or non-balanced. I thought that AC power is just AC power...

 

[oneguy]

IF added to my setup, it would probably live on the floor, 5-6 feet from when I sit. Can you still hear it if you move 2-3 feet away from the Topaz?


Interesting. What is the downside of balanced?
For the record, I have never heard that power can be balanced or non-balanced. I thought that AC power is just AC power...

Same concept as balanced audio signal in that the same signal is being passed in each conductor just 180 deg out of phase.

http://www.equitech.com/FAQ/whatis.html
http://www.aviom.com/blog/balanced-vs-unbalanced/

As far as negatives, I don’t know of specifically what can go wrong with equipment if they are plugged into balanced power other than my previous example of being told my speakers would not turn on with balanced power.

As for noise, that can vary between based on how they have been cared for but in general the larger units are louder from what I have experienced.

 

[ray-dude]

When I flipped my Topaz ITs to balanced, it made a huge difference: hum went from audible 8' away to audible 8" away, and the temperature went from too hot to touch to barely warm. Very very satisfying change. I was careful to confirm that all devices I plug into the ITs are good with balanced power, and I have big "DO NOT USE" labels on those outlets, so someone doesn't mistakenly plug in something thinking it is a regular outlet.

 

[Zachik]

When I flipped my Topaz ITs to balanced, it made a huge difference: hum went from audible 8' away to audible 8" away, and the temperature went from too hot to touch to barely warm. Very very satisfying change. I was careful to confirm that all devices I plug into the ITs are good with balanced power, and I have big "DO NOT USE" labels on those outlets, so someone doesn't mistakenly plug in something thinking it is a regular outlet.

Ray - how do you know which devices are compatible with balanced power and which are not?
What would be the risk of plugging in a device that is not compatible?

 

[ray-dude]

Ray - how do you know which devices are compatible with balanced power and which are not?
What would be the risk of plugging in a device that is not compatible?

different countries are different, so I can speak only from my perspective of US power. As always, when working with power, know what you’re doing, or bring in an electrician that knows what they’re doing. I am not an expert in this area, so please educate yourself and get professionals involved to be safe.

Standard US power has 120V on the hot lead, relative to the neutral lead. These are where the device pulls power from. Ground should only be connected to neutral back at the panel, not in your device or outlet. Basically, the idea is that current should never flow to ground (the ground fault interrupt circuit in your bathroom actually trips when power flows to ground...this is to keep current from flowing through you to that puddle of water on your bathroom floor)

In a blanaced configuration, you basically have +60V on hot and -60V on neutral (I use the + and - loosely here...this is AC voltage). There is still 120V between hot and neutral and all current goes through hot and neutral, but it is off set to be balanced around ground reference. With the IT, this balance basically keeps certain types of noise from bucking the transformer (the hum and the heat) since it cancels out in the coils.

the problem comes when you have a device where ground gets connected to neutral (usually with a switch). You turn off the lamp, the switch connects neutral to outside of the lamp, and the outside of the lamp is energized to -60V vs ground. Not good for anyone or anything touching the lamp.

If the device keeps ground to chassis ground, and uses hot and neutral for all current, and they are never connected no matter the position of the power switch, you should be fine. Best to check with the device maker though, or have your electrician check.

A trick to help though. If your device is able to switch between 120V and 240V operation, it is probably designed to work in Europe and other places where they have balanced power. Still worth checking with the manufacturer or your electrician.

note that there are electrical codes around having balanced power outlets in the US (so someone doesn’t accidentally plug in something that doesn’t work with balanced power). Your electrician will have details

 

[L0rdGwyn]

Just rewired for balanced. For the sake of ease and consistency of wiring used, I snipped off the excess length of the hot lead on the output side, soldered the ends and made a little jumper for the center tap.

All continuity and voltage readings check out, ~125V across + and - on the output, +/- to ground is ~62.5V.

Have my amp hooked up to it now in the same configuration as before, sounds excellent, background black as can be. Transformer hum is completely gone.

Sorry, I am not going to do a back-and-forth A-B of balanced and unbalanced suffice to say I am happy with this setup, just have to verify the rest of my gear is good to go.

 

[oneguy]

@L0rdGwyn Welcome to the club!

 

[Zachik]

Just rewired for balanced. For the sake of ease and consistency of wiring used, I snipped off the excess length of the hot lead on the output side, soldered the ends and made a little jumper for the center tap.

All continuity and voltage readings check out, ~125V across + and - on the output, +/- to ground is ~62.5V.

Have my amp hooked up to it now in the same configuration as before, sounds excellent, background black as can be. Transformer hum is completely gone.

Sorry, I am not going to do a back-and-forth A-B of balanced and unbalanced suffice to say I am happy with this setup, just have to verify the rest of my gear is good to go.

So basically just plugging your GOTL to the Topaz?

 

[L0rdGwyn]

Yes, I will be using a simple power strip to connect multiple components, at least until I get a chassis to mount a number outlets in parallel. I plugged the GOTL in by itself initially for the sake of having a single variable for listening comparisons. I also know the GOTL will work with balanced power.

Edit: all of my gear is working with balanced power, no issues whatsoever.

 

[chrisdrop]

Very jealous!!

I wish I could find a 230v low capacitance IT here in the UK. I haven't been able to find one.

Is it really the case that only these Topaz (and other names mentioned here) have the low pF?
There are various companies that make toroidal tranfos (airlink etc) and balanced power supplies but they don't have the very low capacitance and thus have less noise rejection.

I was thinking about just getting a toroid and making a small box with IEC socket on one side and plugs on the other but couldn't find a transformer.

Jealous ! And well done.