One of best filter cap for class-D is polypropylene. See this page: WIMA
As you can see polyester can have high dissipation factor at high freqs, they serve well usually, but polypropylene is better, specially for high power.
Hi folks.
I now plan to go for this setting:
Filter:
Roederstein KP 1832 0,52uf ( I had them around from earlier projects), I could also use Vishay MKP1844 at 0.44uf.
Decoupling:
Kemet COG 1206 0,068uf
Inductors:
Mundorf aircoils 2*10uh (replacing (for now) my earlier choice of Würth coils)
Now I'd need some support to verfiy the dimensioning:
Goal:
Q:
A 0.707 > Q < 1.0 would be acceptable I guess. A little overshot would be acceptable if going towards the upper value.
With above BOM I'd end up at a
Q=0.8
and
Fo=49khz
assuming an Rl=5R.
Things get slightly better if I'd consider the inductvity of the drivers.
One thing I'm not sure about. Calculating/figuring out a rather exact Rload value I'd have to apply.
I'm running a 2way system (Bastanis). One driver at 11Rdc (no crossover parts) one at 9Rdc (hp with 1uf cap). Can I just use these DC values for a rather reasonable dimensioning? Above 5R is the result of that calculation.
Thx.
I now plan to go for this setting:
Filter:
Roederstein KP 1832 0,52uf ( I had them around from earlier projects), I could also use Vishay MKP1844 at 0.44uf.
Decoupling:
Kemet COG 1206 0,068uf
Inductors:
Mundorf aircoils 2*10uh (replacing (for now) my earlier choice of Würth coils)
Now I'd need some support to verfiy the dimensioning:
Goal:
Q:
A 0.707 > Q < 1.0 would be acceptable I guess. A little overshot would be acceptable if going towards the upper value.
With above BOM I'd end up at a
Q=0.8
and
Fo=49khz
assuming an Rl=5R.
Things get slightly better if I'd consider the inductvity of the drivers.
One thing I'm not sure about. Calculating/figuring out a rather exact Rload value I'd have to apply.
I'm running a 2way system (Bastanis). One driver at 11Rdc (no crossover parts) one at 9Rdc (hp with 1uf cap). Can I just use these DC values for a rather reasonable dimensioning? Above 5R is the result of that calculation.
Thx.
The output coil thing is still bugging me.
I know -- over the years we've seen endless discussions over here, what inductors to use on the amp output, how to wind them, core materials, wire asf. asf.
The majority of those typcially used coils on class-d amps which I looked
at are ususally not made for that particular audio HIGH-Power NF purpose.
Many of those are a kind of spin-off from normal coil production.
These coils do reside at the same position as the traditional crossover inductors.
From that perspective I just anticipate that the ususal CLASS-D output coil performs worse than well done crossover coils on sound related attributes
-- since these crossover coils were made to perform best in the audio frequency range . ( Has anybody ever seen Würth or Coilcraft inductors used in crossover designs?)
I tried those Mundorf air-coils, since these are the result of years of
evolution in the speaker crossover design.
I'm well aware that these are a comprise in terms of filtering the HF stuff out. Though I should mention that I'm in the comfy posititon running speakers with a 98db/SPL.
That leads to a rather low power draw and avoids excessive radiatiton.
My latest listening tests have shown and confirmed again ( I used to use them earlier) , that the sound signature becomes really pleasant without loosing anything.
They sound IMO that good that they gonna stay...
...for now - I'll keep trying.
As usual in audio land - It's always about finding the best compromise.
Enjoy.
I know -- over the years we've seen endless discussions over here, what inductors to use on the amp output, how to wind them, core materials, wire asf. asf.
The majority of those typcially used coils on class-d amps which I looked
at are ususally not made for that particular audio HIGH-Power NF purpose.
Many of those are a kind of spin-off from normal coil production.
These coils do reside at the same position as the traditional crossover inductors.
From that perspective I just anticipate that the ususal CLASS-D output coil performs worse than well done crossover coils on sound related attributes
-- since these crossover coils were made to perform best in the audio frequency range . ( Has anybody ever seen Würth or Coilcraft inductors used in crossover designs?)
I tried those Mundorf air-coils, since these are the result of years of
evolution in the speaker crossover design.
I'm well aware that these are a comprise in terms of filtering the HF stuff out. Though I should mention that I'm in the comfy posititon running speakers with a 98db/SPL.
That leads to a rather low power draw and avoids excessive radiatiton.
My latest listening tests have shown and confirmed again ( I used to use them earlier) , that the sound signature becomes really pleasant without loosing anything.
They sound IMO that good that they gonna stay...
...for now - I'll keep trying.
As usual in audio land - It's always about finding the best compromise.
Enjoy.
Soundcheck: Is this a fixed-freq PWM amp, is there feedback, or is it self-osc, hysteresis, UcD...?
If UcD or other post inductor feedback, the impedance of the load does not matter so much. Even the type of output inductor doesn't count so much there.
If its pre inductor feedback, or without feedback, then you cannot really optimise the output filter, unless you set corenr freq high, so any peak would happen off audio range.
You should forget air-core inductors in class-D, unless you want a noisy radioantenne.
A speaker crossover should separate different audiobands (without any >20kHz material), so they are made to perform this the best. Here you must separate whole audio band from the HF band. Normal crossover inductors are not made for this, so different inductor is needed.
The inductor you shoved are multilayer ones, with so much parasitic capacitances. They will have a hard time filtering, and they will radiate much.
How do you check sound? Do you make a bode plot measurement? Do you do blind-tests? Otherwise you just hear back your preconception.
If UcD or other post inductor feedback, the impedance of the load does not matter so much. Even the type of output inductor doesn't count so much there.
If its pre inductor feedback, or without feedback, then you cannot really optimise the output filter, unless you set corenr freq high, so any peak would happen off audio range.
You should forget air-core inductors in class-D, unless you want a noisy radioantenne.
A speaker crossover should separate different audiobands (without any >20kHz material), so they are made to perform this the best. Here you must separate whole audio band from the HF band. Normal crossover inductors are not made for this, so different inductor is needed.
The inductor you shoved are multilayer ones, with so much parasitic capacitances. They will have a hard time filtering, and they will radiate much.
How do you check sound? Do you make a bode plot measurement? Do you do blind-tests? Otherwise you just hear back your preconception.
IMO as long as the signal travels through that inductor, it's about physics
impacting the signal. Doesn't matter what feedback scheme you're running.
The filter performance is of cousre a different issue. And that's what I mentioned in my post.
My choice might not be the best filter (I'd need to measure that) for now it sounds better then the alternative
solutions I have on the table.
BTW: DIY-Paradize has produced and sold hundreds of really nice sounding Tripath amps with air-cores on the output over the years.
On low power amps air-cores are not that bad.
impacting the signal. Doesn't matter what feedback scheme you're running.
The filter performance is of cousre a different issue. And that's what I mentioned in my post.
My choice might not be the best filter (I'd need to measure that) for now it sounds better then the alternative
solutions I have on the table.
BTW: DIY-Paradize has produced and sold hundreds of really nice sounding Tripath amps with air-cores on the output over the years.
On low power amps air-cores are not that bad.
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Feedback can have much greater impact on signal than the inductor.
A post-inductor feedback will (try to) decrease the impact of the inductor on signal. (for example see a bode diagramm of an UcD amp with different loads, and compare it to an amp with pre-inductor feedback) Usually the differences between inductors in a post-inductor feedback amp will not be audible, only measureable.
Sound better means only listening test? (I asked whether its blind-test, since if its not then you cannot even know it is really better, or your bias is talking)
What is your other inductor choices?
A post-inductor feedback will (try to) decrease the impact of the inductor on signal. (for example see a bode diagramm of an UcD amp with different loads, and compare it to an amp with pre-inductor feedback) Usually the differences between inductors in a post-inductor feedback amp will not be audible, only measureable.
Sound better means only listening test? (I asked whether its blind-test, since if its not then you cannot even know it is really better, or your bias is talking)
What is your other inductor choices?
Quite some people and even companies (e.g. Dexa-Newclassd) consider pre-filter-feedback the prefered choice, because it just sounds better.
In this case I 'dbetter take care on matching the output stage
with the drivers, to get the impact as low as possible.
If you look some posts back, I had asked a question how to calculate "properly" the Rload for that pre-feedback design.
Thx.
In this case I 'dbetter take care on matching the output stage
with the drivers, to get the impact as low as possible.
If you look some posts back, I had asked a question how to calculate "properly" the Rload for that pre-feedback design.
Thx.
"it just sounds better" Why? Is this your opinion? Or is it based on measurement or blinded listening tests with lots of listeners?
Or is this statement like "tube justs sounds better"?
Pre-filter-feedback is more widespread because lots amps are hysteresis self-osc amps. Easy to accomplish, and not under patent protection.
Or is this statement like "tube justs sounds better"?
Pre-filter-feedback is more widespread because lots amps are hysteresis self-osc amps. Easy to accomplish, and not under patent protection.
10uF NP Elcap in Low Pass Filter behind Output - which Replacement?
I want to replace the electrolytic capacitors in the output low pass filter in a class-D modul from follow Electro-Voice-SXA180 powered subwoofer amplifier plate:
Electro Voice SXA180 Powered Subwoofer Amplifier Plate Repair Service | eBay
and post #9 about
bad full-wave rectifier? | Electronics Forum (Circuits, Projects and Microcontrollers)
The schematic you will find here
ELECTRO-VOICE SXA180-18 SCH Service Manual free download, schematics, eeprom, repair info for electronics
or here
Electro-Voice SXA180 Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics
You will find a 24 db low pass filter with 120µH-10uF/NP-35µH-10uF/NP bihind the output of the class-D output stage, which looks different from usual designs like here:
http://www.ti.com.cn/cn/lit/an/sloa119b/sloa119b.pdf
the main reason sems to be the lower cut off frequency, maybe due an application only for powered subwoofer use.
Due not enough space it isn't possible to replace C16 and C17 by WIMA MKS or MKP versions. But I have found follow SMD versions, which are small enough - but the question is, whether from the electrical view and from the view to high reliability which one of the follow showed examples are a good choice:
1) 3x 3,3uF/100V SMD in parallel mode: TDK CKG57KX7R2A335M335JH (5,-- €)
https://product.tdk.com/en/search/capacitor/ceramic/mlcc/info?part_no=CKG57KX7R2A335M335JH
CKG57KX7R2A335M335JH TDK | Mouser
2) 5x 2,2uF/100V SMD in parallel mode: Murata GRM32ER72A225KA35L (1,50 €)
http://www.farnell.com/datasheets/415312.pdf
https://www.reichelt.de/Vielschicht...dex.html?ACTION=3&GROUPID=5155&ARTICLE=107460
3) 1x10uF/100V SMD: Cornell-Dubilier 106K100CS4G-FA (28,-- €)
http://docs-europe.electrocomponents.com/webdocs/13e5/0900766b813e52d1.pdf
106K050CS4G-FA | Capacitor Polymer 10uF | Cornell-Dubilier
4) 1x10uF/100V SMD: TDK C5750X7S2A106M230KB (4,-- €)
http://www.farnell.com/datasheets/1698875.pdf
C5750X7S2A106M230KB. - TDK - CERAMIC CAPACITOR, 10UF, 100V, X7S, 20%, 2220, FULL REEL | Farnell element14 Deutschland
5) 1x10uF/100V SMD: AVX RH221C106MA3RA3 (6,50 €)
RH221C106MA3RA3 | AVX RH Vielschicht Keramikkondensator X7R, 10μF 20% / 100 V, SMD RH22 | AVX
http://www.mouser.com/ds/2/40/rh-16777.pdf
According the image under
http://bilder.hifi-forum.de/max/731560/aktivmodul-ts2bq_206643.jpg
an non polar (NP) elcap isn't the correct choice at this place.
Thank you for your advices.
I want to replace the electrolytic capacitors in the output low pass filter in a class-D modul from follow Electro-Voice-SXA180 powered subwoofer amplifier plate:
Electro Voice SXA180 Powered Subwoofer Amplifier Plate Repair Service | eBay
and post #9 about
bad full-wave rectifier? | Electronics Forum (Circuits, Projects and Microcontrollers)
The schematic you will find here
ELECTRO-VOICE SXA180-18 SCH Service Manual free download, schematics, eeprom, repair info for electronics
or here
Electro-Voice SXA180 Service Manual free download,schematics,datasheets,eeprom bins,pcb,repair info for test equipment and electronics
You will find a 24 db low pass filter with 120µH-10uF/NP-35µH-10uF/NP bihind the output of the class-D output stage, which looks different from usual designs like here:
http://www.ti.com.cn/cn/lit/an/sloa119b/sloa119b.pdf
the main reason sems to be the lower cut off frequency, maybe due an application only for powered subwoofer use.
Due not enough space it isn't possible to replace C16 and C17 by WIMA MKS or MKP versions. But I have found follow SMD versions, which are small enough - but the question is, whether from the electrical view and from the view to high reliability which one of the follow showed examples are a good choice:
1) 3x 3,3uF/100V SMD in parallel mode: TDK CKG57KX7R2A335M335JH (5,-- €)
https://product.tdk.com/en/search/capacitor/ceramic/mlcc/info?part_no=CKG57KX7R2A335M335JH
CKG57KX7R2A335M335JH TDK | Mouser
2) 5x 2,2uF/100V SMD in parallel mode: Murata GRM32ER72A225KA35L (1,50 €)
http://www.farnell.com/datasheets/415312.pdf
https://www.reichelt.de/Vielschicht...dex.html?ACTION=3&GROUPID=5155&ARTICLE=107460
3) 1x10uF/100V SMD: Cornell-Dubilier 106K100CS4G-FA (28,-- €)
http://docs-europe.electrocomponents.com/webdocs/13e5/0900766b813e52d1.pdf
106K050CS4G-FA | Capacitor Polymer 10uF | Cornell-Dubilier
4) 1x10uF/100V SMD: TDK C5750X7S2A106M230KB (4,-- €)
http://www.farnell.com/datasheets/1698875.pdf
C5750X7S2A106M230KB. - TDK - CERAMIC CAPACITOR, 10UF, 100V, X7S, 20%, 2220, FULL REEL | Farnell element14 Deutschland
5) 1x10uF/100V SMD: AVX RH221C106MA3RA3 (6,50 €)
RH221C106MA3RA3 | AVX RH Vielschicht Keramikkondensator X7R, 10μF 20% / 100 V, SMD RH22 | AVX
http://www.mouser.com/ds/2/40/rh-16777.pdf
According the image under
http://bilder.hifi-forum.de/max/731560/aktivmodul-ts2bq_206643.jpg
an non polar (NP) elcap isn't the correct choice at this place.
Thank you for your advices.
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Lorylaci is right partly. A post-filter feedback allows higher inductor and capacitance value variation, including nonlinearity. This is a simple math fact.
But blue bird of best sound quality and optimal design is a very complicated topic.
Post filter designs are more sensitive to capacitor inductance, channel to channel separation (inductor leakage), and PCB layout. This is one of the reason why somebody finds a pre filter feedback is 'better'. The other, for production is the fact that Hypex has the patent for the best topology, so nobody else are allowed to use it (except... long story...)
Designing filters not fed back: it can be done properly only for fully specified load impedance. A resistance is not a good model of a speaker. Inductance is needed also. But I dont care magic numbers and rule of thumbs, I always simulate it.
But blue bird of best sound quality and optimal design is a very complicated topic.
Post filter designs are more sensitive to capacitor inductance, channel to channel separation (inductor leakage), and PCB layout. This is one of the reason why somebody finds a pre filter feedback is 'better'. The other, for production is the fact that Hypex has the patent for the best topology, so nobody else are allowed to use it (except... long story...)
Designing filters not fed back: it can be done properly only for fully specified load impedance. A resistance is not a good model of a speaker. Inductance is needed also. But I dont care magic numbers and rule of thumbs, I always simulate it.
True, the feedback will correct the frequency response..
..however doesn't wrapping feedback around a non-linear device just multiply the harmonics? If true I think a linear filter is still a pre-requisite, perhaps more so with NFB.
I suspect part of the clarity of a good class D amp is due to a simpler harmonic structure than the typical boring non-linear analog amp with the tired feedback loop wrapped around it, winning the measurement battle but losing the audio war.
supplement to post #12:
the class-D schematic from page 25 under
http://akdatabase.org/AKview/albums/userpics/10004/JBLSCS150SISCS160SI SCS180_6S Owners.pdf
shows a better resolution.
the class-D schematic from page 25 under
http://akdatabase.org/AKview/albums/userpics/10004/JBLSCS150SISCS160SI SCS180_6S Owners.pdf
shows a better resolution.
While I'm sure you are correct as any switch is fundamentally non-linear, I was referring to the audio distortion - not the switches
Product How-To: 350W + 350W Class D power amp in the size of an iPod | EE Times
"Class D topology is perfect in theory. It is free from non-linearity, meaning there is zero distortion."
Why? A switch is a device. Your sentence applies.
"Class D topology is perfect in theory. It is free from non-linearity, meaning there is zero distortion."
This is not true. Nor in practice, nor in theory. One of my former teachers studied nonlinearities of several different modulation methods in 1978. (Of course in theory, with ideal parts.)
PWM is perfectly linear only for DC modulation (0 Hz) signal. For higher freq it has nonlinear behaviour.
"Class D topology is perfect in theory. It is free from non-linearity, meaning there is zero distortion."
This is not true. Nor in practice, nor in theory. One of my former teachers studied nonlinearities of several different modulation methods in 1978. (Of course in theory, with ideal parts.)
PWM is perfectly linear only for DC modulation (0 Hz) signal. For higher freq it has nonlinear behaviour.
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Apologies for the necrobump, but I was reading this thread and felt I should point out that it has been proven that PWM can be theoretically lossless under specific conditions:
The Sampling Theorem With Constant Amplitude Variable Width Pulses - IEEE Journals & Magazine