[art]

Here is the cheap knock-off, made by Pulse Engineering. I have used these at times when I could not get any decent ones. Mouser sells 'em...........fairly cheap, so when one is really in need.......:



Well, now you can see why I only use them when I have to. The rho is around 0.4, so that gives us a value of around......175 ohms. And since it has more leakage inductance, the decay is longer. (Remember, we need both rho and decay time to come up with a value for reactance. More reactance......longer decay time.)

OK, I need to do my "other" job. The bills don't pay themselves. More later tonight, or tomorrow.

Pat

[art]

Here are a bunch of transformers I am not wild about.

The first 2 are most likely Schott. They do not have bifilar windings. They use a typical cylindrical core, as opposed to a toroid. (This method would be better, if the windings were bifilar. And the form factor was right.......etc., etc., blah, blah. Don't ask me why they never did it. I know that they knew how to do it that way.)

Anyway, this style is pretty popular with a lot of manufacturers.





Well, you guys can see.......the first one has a rho around 0.5, and the second is better at 0.35.

The next one is, well, odd to say the least. It has 3 windings. I'm not sure why, and from my conversations with the guy who uses them, I'm not sure he knows either. In any case, he cuts the leads to one of the windings, so it can not get hooked up. But, it has the disadvantage of being one of those 1:2 transformers.



You can see that the rho.....after it settles down......is around 0.35, which gives us a load or around 150 ohms. (For those of you in Rio Linda, that is twice what the line should be terminated in.)

OK, to be fair, I added the right amount to make it look like 75 ohms:



So.......let's just say that this is a good reason not to use anything other than 1:1. I think you guys should be smart enough to figure out that the trace should not ring this bad.

(Part of the reason it looks so bad is that extra winding.........it acts like a big hunk of stray reactance, just hanging in the air. Which is exactly what it is. Keep this in mind when we talk about shields!!!!!!!!)

Pat

[art]

Yep, what most of you are waiting for.........Scientific Conversions.

OK, I do not know the actual p/n. The guy who builds the piece of gear that this came out of assured me it is an SC. And a 2:1 one, at that! Oh boy........!

Anyway, after I measured "how bad" it was in its stock form, I shoved a modded Schott in its place (as Schott was still in business at that time). The guy's comment was something to the effect:

"Well, that certainly is interesting, but since the unit is already in production, changing the PCB is not something that we would be interested in doing at this time. Perhaps in a later version.

Where do you buy those transformers, anyway? And how much do they cost?"

Ok, here it is.........enjoy!



Well, I have only one word to describe it:

Yuk!

Ok..........I have it hooked up into a 75 ohm load......and it is a 2:1....or 1:2, depending. (This way is 1:2.)

So, in fairness.........I may be a horse's butt, but I believe in fairness.......here it is with the right load Z on the secondary:



Well, sorry guys, but I am not impressed. If you want something that rings this bad, and has a rho of around 0.6 in your system, then do as you wish. All I can do is point you in another direction. Follow it or ignore. Does not matter to me.

OK.......this is the point where someone who is really mad at me, and has his thinking cap on says:

"Hey, bub.....what happens when you reverse it, and make it a 2:1?"

Well, good question! You are thinking.

So..........here is your answer:



Well, the rho is a bit better. And it does not ring as long. But now you have to contend with this nasty spike in the capacitive direction. And just try to come up with a network to compensate for it. Heh, heh....!

So, take your pick. I would not advise using one in either configuration.

But.........do as you like..........

Pat

[art]

.......And that is not being talked about."
"I wish that I had said that."
"You will, Oscar.........you will."

OK, as promised...........a Newava with a prototype compensation network. "Prototype" means that it is "space wired", but then.....everything else in this exhibit also has been. The final version....the one on a PCB with less stray reactance floating around........looks a bit better.

But why rub it in?




So....as Eric Cartman would say:

"You mean.....'screw you guys, I'm  going home'?"

No, I'll save that for another day.

This one:

"Respect mah ah-thor-a-tah!"

Pat

[art]

While a TDR is the only way to design one of these things, a Vector Network Analyser is really handy to have. Especially when it comes to the fine tuning.

The main advantage to a TDR, other than its speedy measurements, is that you can see where the part of the circuit that is causing the problems.

IOW......you can see whether it is the input wires or output wires that are too long that are causing the return loss to be off. With a VNA, you can only see how high (or low) it is. But without any clue as to what is causing it.

Having said that, you still need a VNA.

The above Newava, return loss in the frequency domain. Below 32 dB above 1 MHz. (They would need to make a slightly larger core to get it lower. Then run into problems higher in frequency. There is no free lunch.) It is below 40 above 3 MHz or so.



(The reference level on this trace is the dotted black line, which may be hard to make out. It is 4 divisions down from the top. IOW, 0 dB is at the top of the trace.)

Gee......the clock rate of SPDIF is 2.8 MHz. I think maybe.......just maybe........this transformer might actually have a chance of working.

But what do I know.......I never wrote a paper for the AES. Matter of fact, I quit the AES almost 20 years ago.

Yep........what do I know? I'm  from Texas.

Pat

[tonyptony]

Pat, I've been keeping low on this only because I'm not interested in this DIY method for any of my gear, but at this point I had to jump in to say...

good work, fellow engineer 

You have given a nice demonstration on HF measuring techniques to a lot of people here.

(from someone who designs radars for a living, and has used TDRs and network analyzers a WHOLE lot over the years)

[art]

Thanks for the kind words, paesano.

Yep, this is not the kind of stuff the average guy has sitting around the house. And it does take some skill to use.

BTW.....I'm wondering when the rest of the crowd will lend their "thanks, bub....." I know that you guys are reading this........I see the stats for all the hits on the site where the data is stored.

Speaking of which..........this one thread has more interest than all of the other threads, on all of the other half dozen or so forums similar material has appeared, combined.

So, thanks for letting me know that this is not all for nowt. The other forums did not seem to be interested all that much in this type of discussion. (Which may be why I don't do as many on them these days.)

Who could imagine that a forum that is not geared towards strictly DIY would show so much interest? Maybe I will be encouraged to post more stuff like this here.

"Does that mean that you won't be so arrogant, condescending and annoying the next time?"

No, probably not. Maybe worse. I am an engineer..................

Pat

[drmike]

hello,
i'm the one who started this post, i'm just a dentist. i'm trying to learn a few things on this site, you know, where to get these parts and how to  hook them up.
people get way too offended, pat obviously knows his business. just go with the flow and and try to enjoy  better sound.
thanks,
drmike
p.s. can someone post some pictures of a typical transformer instll in a dac?
thanks again

[2wo]

Quote.

Does that mean that you won't be so arrogant, condescending and annoying the next time?"

No, probably not. Maybe worse. I am an engineer..................

You back your assersions with data and mersuments...That might be a first aa

I get sick of folks that say "I'm right" and will produce no proof.

Appreciate the effort...Im listening...John

[tonyptony]

Thanks for the kind words, paesano.

...

"Does that mean that you won't be so arrogant, condescending and annoying the next time?"

No, probably not. Maybe worse. I am an engineer..................

Pat

Not to get too OT, but I suspect those reading this who aren't engineers won't appreciate the double entendre built into your statement, Pat. Over the years I have worked with peers who really are just arrogant a$$holes, but they are the exception. Most skilled engineers that I've had the pleasure to work with have a tremendous amount of pride in what they (I'll include myself here  ) have been able to do in their careers. I've seen many people who aren't in the profession sometimes mistake that expression of pride for arrogance. More often than not that's really not the case. In reading through your posts I'm pretty sure I'm seeing more pride than arrogance on your part as well.

But what do I know? I'm just another engineer. 

BTW, my opinion on all this is that even though I am in a profession that lives by measurable results, I still believe that in audio we maybe haven't figured out how to measure quite everything a skilled listener is able to experience. Having said that, I also believe that if something does measure badly in its intended application, I'd be hard pressed to support using it even if it seems to sound good.

[jhm731]

"OK, I do not know the actual p/n. The guy who builds the piece of gear that this came out of assured me it is an SC. And a 2:1 one, at that! Oh boy........!"

FYI- SC947-02 which the group purchased and everyone seems very happy with is 1:1.

Without the part numbers how can anyone verify your test results?

[crooner]

Yep........what do I know? I'm  from Texas.

Pat

Better not mess with him. He's from Texas!!! 

[tonyptony]

FYI- SC947-02 which the group purchased and everyone seems very happy with is 1:1.

Without the part numbers how can anyone verify your test results?

Might I suggest, in the interest of keeping this a nice scientific investigation, that if someone who did the group buy has a spare - and Pat is willing to do it - that that person work out with Pat the means to get that sample to him for measurement. I for one would like to see what the objective evidence shows, strictly from a point of engineering curiosity.

[art]

If high-end manufacturers didn't rub all the numbers off all of the parts in their gear.................

Look, some guy on some other forum, a week or two ago, bragged how good this piece of gear is.

And why it was so, because it used an SC transformer.

No, he doesn't like me either now.

But let's talk about verifying results.......

I'll take photos of what I did.

Anyone is welcome to come and watch. Just let me know in advance.

As for SC's test.......

Have you seen their test set-up?

As I have shown, it is possible to construct a network to make a transformer look really good.

Now......what if...........just suppose...........SC made a similar network for their transformer. You know, one that makes it look really good on a TDR.

(It could happen...........)

And then.........they take theirs out, and stick in Brand X.

And either take the network out (since it obviously won't be right), or worse.......leave it in!

Now, I am not saying that they did. But since I have no proof either way, well, their tests are not verifiable to me.

See, it works both ways, bub.

Just admit that I may know what the hell I am talking about and that I may be on to something. Other than look for holes in my position. Or just chose to ignore them, and let everyone else try to learn something.

Besides......need I say it again.......I don't sell transformers. I do not know anyone at Newava. I get nothing out of this. You can chose to ignore my tests, or chose to open your mind to new ideas.

Won't put food on my table either way.

Pat

[tanchiro58]

.I don't sell transformers. I do not know anyone at Newava. I get nothing out of this. You can chose to ignore my tests, or chose to open your mind to new ideas.

Pat,

I am a simple guy like drmike and know nothing about electronic engineering. But I do know listening to my music and which one is for my taste. I do learn experiences of doing DIY (it is only a hobby to relieve stressful life). Since once again I do not throughly understand your tests about pulse transformers you the only one who gave out the proof of your "right." Then you should know what are you testing or did the tests to what models of Newava trannies. "Choose to open your mind to new ideas" is not worth if those ideas are kept hiding and to show in this forum to discuss ONLY? Thanks.

[JoshK]

I been reading quietly, trying to learn something a bit more than a superficial understanding.  Might be more years of learning for that.

I appreciate you sharing your measurements and time to explain them.  If you want one of the SC's that we all bought in the group buy to test out, pm me and I'll send one out to you. 

[rotcoddam]

Pat,
  Cheers to you and thanks for taking your time to show us this info. Please keep posting more. 
Marty   

 
   

[Builder Brad]

Pat,

nice work!

if there are alternatives to the SC transformer and they sound better - Im all ears. Seriously this is such a low cost and easy upgrade, even for those that have fitted the SC parts,  that its got to be investigated.

++++ to Josh for his offer to supply a test sample

Brad

[Builder Brad]

has there been any more developments with this?

anyone tried comparing the sound of the SC transformers with the suggested alternative?

I would do this, as its an easy swap out, however those transformers seem more readily available over in the US.

Brad

[art]

I did some digging into the mystery transformers that are sitting around.......I think "xfrmr2" is a Newava 22160. Again, I am not the guy who takes the p/n's off of these things. The blame on that goes to the companies that think they have some special secret to hide.

Anyway......I played around with a network to make it appear more like a 75 ohm load. Return loss is 32 dB at 2.8 MHz. I'll post some data later, when I get a chance.

Pat