hi all
just wondering if anyone changed this 10uH inductor to other values or is it even recommended for us to change it?
application note 9, section 7 from tripath states that they have good results from customer eval boards using 18uH to 22uH combined with 0.22uF caps and an auxiliary RC load (i think this refers to the zobel?) of 33R and 0.1uF.
just wondering if anyone changed this 10uH inductor to other values or is it even recommended for us to change it?
application note 9, section 7 from tripath states that they have good results from customer eval boards using 18uH to 22uH combined with 0.22uF caps and an auxiliary RC load (i think this refers to the zobel?) of 33R and 0.1uF.
Use toroids or bobbins.
Hi there!
Must admit I've read alot stuff recenty where people say don't use air-cored inductors in these amps, but I've yet to hear of anyone who's had problems from using them. I've just finished building an AudioDigit TA2020 kti which uses air cores and it sounds great - certainly no noise that I can hear even with ear close to the speaker.
Noticed that the Charleeze (sp?) amp is now using air cores as well.
Cheers,
- John
Must admit I've read alot stuff recenty where people say don't use air-cored inductors in these amps, but I've yet to hear of anyone who's had problems from using them. I've just finished building an AudioDigit TA2020 kti which uses air cores and it sounds great - certainly no noise that I can hear even with ear close to the speaker.
Noticed that the Charleeze (sp?) amp is now using air cores as well.
Cheers,
- John
Air cores are a problem form a EMI point of view. The flux is not confined inside a core like in troids and E-cores.
It's therefore possible that the air core inductor will induce currents in you're amplifier and cause distortion and noise, not to mention the effect on radio stations and nearby equipment.
It's therefore possible that the air core inductor will induce currents in you're amplifier and cause distortion and noise, not to mention the effect on radio stations and nearby equipment.
DonJuan said:
I say this for several reasons, let me list them:
1) This is radio frequency. It ain't audio until it comes out of the filter.
The Tripath is a switching amp with frequencies well up into the LW and MW radio bands. Those aircore coils are just little transmitting antennae, broadcasting into anything nearby. They should at least be shielded. Shielded bobbins are available, but toroids work well.
2) Air has a very low magnetic flux, thus aircore inductors need a lot more coils than an inductor wound on a ferrite. Making an aircore inductor small enough to fit on the Sonic or Fenice boards means using many coils of fine gauge wire. Not good for DCR or damping.
3) Different ferrite materials have different properties and are effective at different frequencies. Perhaps the ferrites you tested were not meant for the frequency range of the Tripath switching? Most switching PSUs don't run above 100kHz, so the inductors they use are designed for that. The Tripath switches much higher and with a spread frequency band.
Type 61 core looks like a good choice, I'm testing it now.
Aircore inductors are great for audio frequency crossover circuits, we all know that. And this is just a speaker low pass filter, right? Well, not quite. As I said above, "It ain't audio until it comes out of the filter.
A nice aircore with large gauge wire or foil that is properly shielded might be better than a ferrite, but for practical reasons (size, placement) this isn't done. FWIW, I just don't want aircore antennae on my amp board
I've tried it, didn't like it. Too easy to get that RF into circuits where it doesn't belong. Sounds "sour".<END RANT>
Plying arround with Micrometals inductor design software, it seams that only -2 and -8 matrials are suited for 200-600kHz switching, 10Amps DC with a low core loss.
Link to Micrometals software site
T106-2 has very very good properties and it's cheap. I use it for my own Class D design. The loss at +/-40V switching amp with 10amps of current produces less then 0,5W of core losses and the permability is 98% of its initial value at this load.
T106-14, T130-2, T130-14, T157-2, T157-12 cores also have good properties. Try their software.
Go for a DC biased automatic design. It can max. show 40 results. Therfore try selecting only one or two materials at a time, and let it design 20 different inductors for you witn that material. It'l show you core losses, inductance fall as function of IDC load and all kind of stuff. To aviod to much distortion, you should go for a core where the permability dont fall to much from it's initial value under load conditions.
Using their software is seams that material -61 is okey, if you go for a low number of turns. But it's more expensive, has larger core losses and the inductance value fall at high loads. Material -2 and -8 really have the best properties I think.
Link to Micrometals software site
T106-2 has very very good properties and it's cheap. I use it for my own Class D design. The loss at +/-40V switching amp with 10amps of current produces less then 0,5W of core losses and the permability is 98% of its initial value at this load.
T106-14, T130-2, T130-14, T157-2, T157-12 cores also have good properties. Try their software.
Go for a DC biased automatic design. It can max. show 40 results. Therfore try selecting only one or two materials at a time, and let it design 20 different inductors for you witn that material. It'l show you core losses, inductance fall as function of IDC load and all kind of stuff. To aviod to much distortion, you should go for a core where the permability dont fall to much from it's initial value under load conditions.
Using their software is seams that material -61 is okey, if you go for a low number of turns. But it's more expensive, has larger core losses and the inductance value fall at high loads. Material -2 and -8 really have the best properties I think.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.