What is best concept to achieve this?I made a lot of amplifiers in my life including D class amplifiers.What i am aiming on is to eliminate output filter completely.R there already some diy solutions which i can try?
On google there is very short theory about this and no available solutions to try ..... ???? ..... is this so hard to make?
On google there is very short theory about this and no available solutions to try ..... ???? ..... is this so hard to make?
What is best concept to achieve this?I made a lot of amplifiers in my life including D class amplifiers.What i am aiming on is to eliminate output filter completely.R there already some diy solutions which i can try?
Low power class D chips work without output filters, made possible also because of short wiring distances.
R there any concepts (on paper) available......with explanations of how to implement logic and which type of PWM modulation?They force small power chips as filter less couse on low power u have low EMI......Now,what about high power.....will EMI stay in normal levels or even if it is filter less we will need chokes and caps?
Filterless Class D (when done properly e.g. by a competent chip manufacturer) spreads the electromagnetic interference around in order to sneak under the EMC limits. It turns any amp into a wideband noise generator.
DIY filterless would require some understanding of generating pseudo-random sequences. However, there is no audio reason for going filterless - cheap low-power commercial circuits just do it to save a few pence and a little PCB space. DIYers should always include a filter.
DIY filterless would require some understanding of generating pseudo-random sequences. However, there is no audio reason for going filterless - cheap low-power commercial circuits just do it to save a few pence and a little PCB space. DIYers should always include a filter.
There's no point in high power filterless class D either. As power increase the parasitic inductances and capacitances of the speaker cable itself will make it into a highly uncontrollable filter while at the same time being a radio noise transmitter. All you can hope to achieve is getting much lower sound quality and much lower efficiency. You can naturally shorten the cables but only up to a certain point as you have to remember that the leads to the voice coil from the speaker terminals also count, so even if you mounted the outputs directly on the speaker terminals you could only get to about 100W-200W or so depending on actual speaker used.
I may point out that in most countries it is illegal to make or use a device which transmits radio frequency noise above a certain level. In my opinion, you're putting lives at risk if you experiment with high power filterless class D without knowing what you're doing.
I may point out that in most countries it is illegal to make or use a device which transmits radio frequency noise above a certain level. In my opinion, you're putting lives at risk if you experiment with high power filterless class D without knowing what you're doing.
Last edited:
Even pseudo-random sequences will not significantly impact on a class D amplifier operating as a wide band radio noise transmitter. It is in the high switching pulses where most of the nasty stuff gets produced, not in the switching frequency by itself (methinks).
The sharp edges produce harmonics of the switching frequency, but probably modulated by the audio signal.
No, the sharp edges produce all frequencies up to a certain point (but in bursts, the timing of these bursts determined by the switching frequency)! The sharpness of the edge determines the frequency up to which these frequencies are produced.
Because of the fast switching frequencies, very high frequencies are produced, for which even small pieces of wire act as effective antenae.
Because of the fast switching frequencies, very high frequencies are produced, for which even small pieces of wire act as effective antenae.
I think Mr. Fourier would disagree. The frequency components of any periodic signare all at harmonics of the fundamental frequency. For Class D this is complicated by the audio waveform too, but for simplicity we can consider a time when the audio is silent.vacuphile said:
Yes.
Yes.
Trust me, you dont wanna get in problems with filterless class d,there is no advantage in diy,advantage is seen only in very small devices like phones where you need to save every penny and square milimeter of space.
High power radio frequency will turn everything metallic into speakers,from fences to pipes and metal plates, it will be scary, something similar happened to me.
High power radio frequency will turn everything metallic into speakers,from fences to pipes and metal plates, it will be scary, something similar happened to me.
Petruv i will not agree with you at all.Smart design can do much if u know exactly what r u doing.I am very sharp in designing and i am missing few details about the concept of filter less scheme.....Once i get it 100% i will make high power filter less design which will over perform every single existing design in D class.
Highly doubtful but as long as you take care in not emitting copious amounts RFI and thereby potentially putting lives at risk, you're certainly welcome to try.
Come on, you know better! A pulse contains all frequencies, you are confused between the switching frequency, and the spectral content of the switch on and off pulses, which because of the fast rise times contains high frequency hash. These frequencies are not related to the switching frequency.
mr. Fourier loves me for grasping this.
Technically it would not contain all frequencies though as it would be limited by the rise time but that just me being pedantic. Like when I say it is technically not possible for any electrical signal to be analog, all electrical signals are digital in the sense that the electrical charge of an electron is indivisible, and that there is a maximum and a minimum frequency that is possible to make limited by the total energy in the Universe and it's diameter.
Getting back on topic though, I don't really understand this fascination with filterless class D designs, especially when it doesn't make sense.
Tube amps have output transformers for impedance matching for example and people generally agree that they can sound pretty good. Class D amps have output filters to transform the output into an analog signal. So what if there are instances where you can avoid using an output filter, for example at very low power, the only reason to do so really is to save cost and/or board space for improved lay-out of a compact (low power) amp. There are no inherent sound quality benefits but lots of drawbacks.
Getting back on topic though, I don't really understand this fascination with filterless class D designs, especially when it doesn't make sense.
Tube amps have output transformers for impedance matching for example and people generally agree that they can sound pretty good. Class D amps have output filters to transform the output into an analog signal. So what if there are instances where you can avoid using an output filter, for example at very low power, the only reason to do so really is to save cost and/or board space for improved lay-out of a compact (low power) amp. There are no inherent sound quality benefits but lots of drawbacks.
Last edited:
That is what I said in my first post.
Like you, I don't understand why people would want to run a class D amp without output filter. It's like running a DAC without reconstruction filter.
Julf u r my man 😀 ..... I love you.Making judgement about someone just on what he/she wrote is great sign how inteligent and stable you are.....ha hah ah ah ahha .....Ok,I will stop here and I am pleasing you to not to continue.Ask your self what if i am right...I am facinated with D class amplifier concept completely and i have designed many amplifiers for USA market (oops u didnt know that,srry) ...I have more than 18 years in circuit designing and thats my life-me. I will make filter less design , there r no doubts there.....thing is where to hit.
We all r discussing why not or why to do that ..... Original post here is about HOW TO ACHIEVE filter less modulation....What is the catch?What is best way to go?I have been thinking a lot about this and rise / fall ltimes r playing big role in this.....If we slow down a little rise fall times we will eliminate a lot of harmonics....BUT we will have lower efficiency.So good way to go is lower frequency.....On other side that will give us high ripple currents through speaker and low sampling rate ......So we need high frequency and still to hit high efficiency with slower up/down edges.There must be a way.Key is type of modulation ..... smart PWM can overcome all issues related to EMI.If there r some serious thoughts about this i will be glad to discuss.
We all r discussing why not or why to do that ..... Original post here is about HOW TO ACHIEVE filter less modulation....What is the catch?What is best way to go?I have been thinking a lot about this and rise / fall ltimes r playing big role in this.....If we slow down a little rise fall times we will eliminate a lot of harmonics....BUT we will have lower efficiency.So good way to go is lower frequency.....On other side that will give us high ripple currents through speaker and low sampling rate ......So we need high frequency and still to hit high efficiency with slower up/down edges.There must be a way.Key is type of modulation ..... smart PWM can overcome all issues related to EMI.If there r some serious thoughts about this i will be glad to discuss.
Yes, I am afraid I make judgements about people based on silly things like how they write. I believe in results, not hot air and talk.
You do seem to make assumptions about my experience and background too.
Filterless class D is accomplished by noise modulation, but that doesn't actually reduce the noise, it just spreads the spectrum over a wider range. If you have managed to come up with some great new scheme that gets around that, then good for you! Looking forward to reading the AES or IEEE paper about it!
You do seem to make assumptions about my experience and background too.
Filterless class D is accomplished by noise modulation, but that doesn't actually reduce the noise, it just spreads the spectrum over a wider range. If you have managed to come up with some great new scheme that gets around that, then good for you! Looking forward to reading the AES or IEEE paper about it!
- Status
- Not open for further replies.