Ever tried the type 0 toroids?

[sendler]

Originally Posted by Saturnus

Air cores of any type should be avoided at all cost to achieve the best sound.

Sorry. Measurements and theory aside, my air cores sound way better than my type 2 toroids in the output filter of a Sure 2X100 amp. Same wire.

[Pafi]

Saturnus! If you don't know that trafo, core and coil are not the same things, then please don't "help"!


Sendler! With the same inductance?

[Saturnus]

Originally Posted by sendler

Sorry. Measurements and theory aside, my air cores sound way better than my type 2 toroids in the output filter of a Sure 2X100 amp. Same wire.

"cable effect"?

Seriously though, I'm sure you think they do, and maybe they do because you had a lucky day winding them and that the original where completely lousy quality, which they are, but all things being equal cored output coils sound better and measures better than air cores.

[Nikolas Ojala]

Originally Posted by Saturnus

It means that high frequency operating cores like in the output of a class-D will always function best the less parasitic resistance and capacitance it has, both are ensured by correctly coring the trafo. Air cores of any type should be avoided at all cost to achieve the best sound.

Tell me: Why are air core inductors produced?



Least parasitic capacitance: One layer coil wound on a plastic former.
Least resistance: Enough copper.

[JohnG]

Originally Posted by phase_accurate

Even if a toroidal coil is wound perfectly it still has one single loop that is causing a stray field. And this is unavidable. Don't forget about that !

Regards

Charles

It is not uncommon to have a single anti-turn on the PCB that cancels the single loop formed by the toroid. It's not perfect, but it can be quite effective. for a core who's axis is parallel to the PCB, this can be accomplished with a loop of wire, or for better cancellation, two parallel loops on either side of the toroid.

John

[sendler]

Originally Posted by Pafi

With the same inductance?

There are other variables in play for me to make sweeping statements but eventually I will address all of the differences and feel confident that the class D filters will follow the experience of speaker designers who learned years ago that air cored inductors sound better than magnetic cores especially when we are stuck with using them in series with our tweeters. I have 6uH for the T106-2 and 4uH for the solenoidal air core so you are right. I am still dealing with substantial variables. As it often happens here, we start with a simple question in a thread which eventually degenerates somewhat to where the posts start to get defensive of each view point. It is apparent to me after many posts and threads over the last month that there have been very few reports by people doing listening trials with various coils. The ones that did report improvements are using air cores until they are warned about the EMI. This lack of comparrisons still surprises me as caps have been discussed ad nauseam everywhere but maybe class D is still much smaller in interest that not nearly as many serious DIYers are trying to push their sonic envelope as much as we see in the solid state forum. The emission problem also creates a log jam for the styles that can be implemented. Tripath seems to have done some listening and settled on the type 2 core with 22guage wire at 12uH but most manufacturers have a high priority on miniaturization which I do not.
Let's see what these monsters will do. They turned out quite large due to the 14ga wire.

[stoc005]

According to Ferroxcube, a gapped toroid is the preferred coil form (which they sell, of course). The gap helps the core by storing more energy in the gap and preventing saturation of the core. If the core saturates, the inductance collapses.
They have an app. note where an IR class D amp had the output inductors were replaced with gapped toroid coils and the audio distortion measured was noticeably lower. Makes sense to me but I'm an engineer.

[sendler]

Originally Posted by stoc005

According to Ferroxcube, a gapped toroid is the preferred coil form (which they sell, of course). The gap helps the core by storing more energy in the gap and preventing saturation of the core. If the core saturates, the inductance collapses.
They have an app. note where an IR class D amp had the output inductors were replaced with gapped toroid coils and the audio distortion measured was noticeably lower. Makes sense to me but I'm an engineer.

.
So who sells Ferroxcube cores I can try?

[tinitus]

Speaker xo is where I come from
And there the ordinary air coil is the best
But when biggies are needed toroids are the best

Some are air gapped, but not sure how its done
A few are special ironpowder toroid core containing enough air to function alike air gapped

I dont really like foil inductors, but with such small inductor needed here this makes me wonder if it would be useable combined with a toroid core

toroid core foil inductor

But it may not have the minimal interference radiation of a wirewound toroid

[stoc005]

http://www.ferroxcube.com/appl/info/gaptoroids.pdf

Use a TN26/11-3C20-A113 if you are going to order some. It is the largest and will handle 100W or so. Read the app. note and find out why you want the big one.....

Ferroxcube can be bought at their distributors but I see no stock on the above PN at any of their distributors. Bummer. I am going to need (4) pcs soon.