Discussion of AC mains isolation transformers

[Speed Racer]

34 minutes ago, spacexpert said:

Ok I removed the link on the output side.  X1 and X2 together made a spark when touched.  I immediately pulled the multimeter away.

 

Is that good?  I don't want to kill myself until I've seen the Grand Canyon.   

 

http://www.surplussales.com/Transformers/Pdfs/tp-91092-31_N.pdf

[Speed Racer]

8 minutes ago, spacexpert said:

 

Oh there's instructions?  Cool I'll print them off.  Thanks.  

 

[Speed Racer]

7 minutes ago, One and a half said:

The 91097 model is 240V input and output only, so the windings are all the same!

 

The 91097-31 is a 120v/240v model. 

 

120v input to 120v balanced output would be wired like this:

 

Input:
Hot (black) to H1
Neutral (white) to H4
Jumper H2 to H3
Ground to chassis

Output:
Hot 1 (black) to X1
Hot 2 (white) to X4
X2/X3 center tap connected to chassis ground and outlet ground.

[Speed Racer]

3 minutes ago, One and a half said:

 

All four windings are 120V a piece. If the input is 120V, then 

 

Hot to H1 & H3, Neutral to H2 & H4.

 

The secondary is as you mentioned a 240V output all the time in balanced mode, here's why:  Since both windings X1-X2, X3-X4 have 120V applied, the centre tap on the secondary is the series join, the outputs are added to 240V.

 

If 120V is desired on the output in balanced mode, the transformer would need to be wound 120V-60V two parallel windings. The input can then be configured for 120V or 240V.

 

 

 

 

It's not clear to me what you are saying. My Topaz is wired as I described above with 120v input and has balanced 120v output.

[Speed Racer]

10 minutes ago, One and a half said:

 

From the centre tap to each of the Hot tines, there's 120V unless the topaz is not mentioned above in the flyer.

The secondaries are 120V a piece and are wired in parallel in the 120V connection example. That Topaz can be wired for 120/240V to 120V/240V,  not 120V/240V to 60/120V which is what you need for a balanced supply output.

 

My Topaz is a 91002-31 (2.5kVa). It is fed 120v on the input side. I wired it as follows:

 

Input:
Hot (black) to H1
Neutral (white) to H4
Jumper H2 to H3
Ground to chassis

Output:
Hot 1 (black) to X1
Hot 2 (white) to X4
X2/X3 center tap connected to chassis ground and outlet ground.

 

On the socket: When I measure Hot to ground I get 62v. When I measure Neutral to ground I get 62v. When I measure Hot to Neutral I get 124v. 

 

In other words, I am getting balanced power.....

 

[Speed Racer]

39 minutes ago, One and a half said:

 

Ah, OK, by connecting the input windings in series and not supplying 240V but 120V, effectively, the secondaries receive 60V (as well as each primary winding). So in effect you have a 60-0-60 balanced connection on the output!

The more closer the voltages are to each other hot 1 to ground, Hot 2 to ground, the better the crap can be filtered and the hotter the transformer will get.

 

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

 

 

 

When I went to balanced, my Topaz ran quieter and cooler! Each hot leg has the exact same voltage.

 

I don't know why they were discontinued. I bet audio nuts didn't know much about them until after they stopped being made. The fact that you can buy so cheaply on eBay tells me most people still don't know what a fantastic device they are!

[Speed Racer]

36 minutes ago, spacexpert said:

I noticed you mentioned VAC not DC...  Should I try and find a VAC output wall wart?

 

The wall wart has to put out AC...what are we testing here??

[Speed Racer]

2 hours ago, zilch0md said:

 

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

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

[Speed Racer]

22 hours ago, Cornan said:

When I talked about external grounding in my previous post I was'nt talking about chassi to chassi grounding, but about connecting the chassi to a grounding box to enhance/clean the ground path.

 

Do you mean a grounding box like an Entreq?? Why introduce snake oil to an otherwise reasonable thread??

[Speed Racer]

5 hours ago, spacexpert said:

No, it is a steady pitch coming from the toroidal.   

 

3 hours ago, spacexpert said:

I will confess to being a bit ignorant about balanced mode.  Is the 240V balanced by default, or does that require some funky rewiring?

 

The Topaz units are not toroidal designs.

 

240v in/out is balanced with 120v on each conductor relative to ground.

[Speed Racer]

26 minutes ago, mikicasellas said:

I am too having issues with my second "new" acquired Topaz 91002-32 / 2.4 KVA / .0005pF, it gets hotter than my first Topaz 91001-22  / 1KVA / .001pF with the same amount of gear connected and also it makes the sound more bright, less clean...?? i am so frustrated, i thought i was going to improve on SQ but went back with this.

 

So being 1.4 KVA more than my previous, it gets hotter and sounds brighter, i was trying to divide the charge of my entire system, putting the more obvious gear on the bigger Topaz:

 

Topaz 91002-32 / 2.4 KVA / .0005pF:

MacMini

DAC

Preamp

Amp

 

Topaz 91001-22  / 1KVA / .001pF:

Receiver

TV

Router

External USB HD

 

I guess it must be damaged, any suggestions?

 

Well, you could rewire it to run balanced power. I did that with my 91002-31 2.5kVa Topaz and it ran much quieter and much cooler.

 

Regardless, I would not put the Mac Mini on the same Topaz as your DAC, preamp, and amp. I put all my analog audio gear on one Topaz and put the other gear on a wall outlet or another Topaz. I would isolate your Mac Mini from the DAC somehow (Schiit Eitr would be a good choice) and not plug it into the Topaz with your audio components.

[Speed Racer]

55 minutes ago, mikicasellas said:

 

Would it also be that could have damaged cables inside or bad soldering...don't you think?

 

Running balanced seems very interesting, but i don't have an idea on how to do that...would you be kind enough to share perhaps some pics to see how the connection looks and how to be connected that way?

 

Thanks for the feedback!

 

I doubt you have bad wiring in your Topaz.

 

I wired mine as follows:

 

Input:
Hot (black) to H1
Neutral (white) to H4
Jumper H2 to H3
Ground to chassis

Output:
Hot 1 (black) to X1
Hot 2 (white) to X4
X2/X3 center tap connected to chassis ground and outlet ground.

 

I had to make a jumper to connect X2 (or X3) to GND.

 

On the socket: When I measure Hot to ground I get 62v. When I measure Neutral to ground I get 62v. When I measure Hot to Neutral I get 124v.

[Speed Racer]

38 minutes ago, Cornan said:

Great to have you around here @Speed Racer. Even if we do not agree on everything your know-how is a great asset here! ?

 

The world would be boring if everyone agreed with everyone else! I still think you are little bit off because of your like of grounding boxes! 

[Speed Racer]

My 2.5kVa Topaz was a bit noisy until I converted it to balanced power. It went from noisy and hot to silent and cool.

[Speed Racer]

10 minutes ago, One and a half said:

Is your model the 0.005 pf or 0.0005 pf? If the voltage symmetry is really close, there's no need for the Equitech.

 

It's a 91002-31 so it is .0005pF. The unit offers 146dB of common mode noise reduction and 60dB of normal mode noise reduction.

[Speed Racer]

1 hour ago, oneguy said:

Very nice! My new old stock 1.8 kVa (MGE 91018-32T) was waiting for me when I came home on Saturday. The exterior looks great but I unfortunately can’t check it out operationally since it came with a twist lock plug. I just ordered an adapter plug but I have anothe 7-10 days before that arrives. 

 

Do you know how it is wired? 240v or 120v?

[Speed Racer]

7 minutes ago, One and a half said:

If the Topaz output is balanced, ie 120-0-120 (60-0-60) with the centre tap earthed, then use this RCBO. This RCBO is a 2 pole device, since there are two wires above ground with different potentials to ground. By different potentials I mean direction, one is 180 degrees out of phase with the other.

 An RCBO is a combined circuit breaker plus an RCD (GFCI) in the same package. The 6A rating is about the smallest available in current rating. In the event of a leakage current to earth or imbalance btween the two hot conductors, or current drawn is greater than 6A (double the output of the 750VA transformer, then the breaker will trip. There are ways to detect excess current with an adjustable overload, but more on that a lot later. Still working on protection systems for transformers much to do still.

 

If one of the outputs is earthed, there's a different RCBO to choose and it's a LOT cheaper, since they make them by the millions.  A portable one is fine, like this one but it's only an RCD and doesn't have the thermal protection. 

 

I wired mine as follows:

 

Input:
Hot (black) to H1
Neutral (white) to H4
Jumper H2 to H3
Ground to chassis

Output:
Hot 1 (black) to X1
Hot 2 (white) to X4
X2/X3 center tap connected to chassis ground and outlet ground.

 

That means I need the less expensive RCBO or the RCD because the output is earthed, correct?

 

Why would you wire it the other way?

[Speed Racer]

Just now, spacexpert said:

 

This would be how I wired mine as well for 240V.

 

That makes sense as 240v is balanced  by default.

[Speed Racer]

4 minutes ago, Ralf11 said:

has anyone tried these leakage current reduction / isolation transformer setups on systems where the computer or server is galvanically isolated from the DAC?  if so, what were the results?

 

e.g. using optical isolation ( @jabbr) or WiFi ??

 

Of course! My setup uses a Topaz 2.5kVa ISO transformer wired for balanced power. The only digital device plugged into the Topaz is my DAC which is galvanically isolated from the computer feeding it using an Eitr.

 

What do you want to know?

[Speed Racer]

2 hours ago, Ralf11 said:

Can you describe the subjective improvement in SQ, before vs. after Topazification?

 

Also, have you done any blind tests, by moving the AC feed, etc.?

 

The biggest differences I noticed were a more black background and better instrument and voice separation. What I mean by the later is that the locations on the soundstage are more distinct. The blacker background means there is more clarity as the whole sound is less muddled.

 

I didn't do A/B blind testing. It takes too long to power everything down and power everything back up. Too much time would pass for it to be meaningful.

[Speed Racer]

23 minutes ago, One and a half said:

Very, very complex system. 

 

That is an understatement!!!!! I think "Rube Goldberg machine" when I read the configuration descriptions.....