DAXgroup said:
Firstly, my apologies for a misunderstanding. I did not mean to describe your DAX as a poor performing power DAC. I meant to describe power DAC’s as poor-performing. I have gotten the impression that improving a power DAC's performance pretty quickly becomes a matter of improving the power supply. See TACT.
Secondly, I am not technically strong in digital, so I am here to learn about digital audio.
So how can I justify jumping to conclusions about power DAC’s? Because I can read and research.
Take a look here:
http://www.classd.org/oem_products/products/ti_dig_amp.htm
http://www.classd.org/qna/qnafs.htm
and here:
http://audioholics.com/techtips/audioprinciples/amplifiers/digital_classD_amplifiers.html
Of course, not all that is written is true, but sometimes the writer is authoritative. Putzeys impresses me. He declined to join this thread.
So, perhaps you guys at DAX are inadvertently asking the technically strong people on this thread to accompany you in hurtling towards the brick wall at the end of a dead end street, at least regarding the power DAC. There’s nothing wrong with that. If you break through, you’re all heroes.
I accept your comment that high distortion amps can sound good. Is it the goal of this project to design such an amp?
Finally, can you explain how exactly the project will be inferior if it uses an analog class D power stage? What do you stand to lose, apart from distortion and a purist principle? If the answer is to see how good a digital input Class D amp can be, then see TACT.
I hope, instead of being seen as negative, my posts are seen as “testing” the strength of the project and its goals.
Grant
I am personally a fan of switching amplifiers but I would also like to mention that it isn't worth USING new technologies just for the sake of new technologies if they don't have other advantages than being new ..........
I am convinced that it is easier to make a high-precision DAC at low levels and high precision amplification in analog.
But it is still worth trying of course !
Regards
Charles
Ok, I couldn't resist another post. As far as the discussion about "state of the art", I think the jaded attitude many audiophiles have towards new technology is understandable, though I personally feel its excessive. Decades ago, a hifi system was just that, a system that strove for high fidelity. In the last 30 years or so, we've seen so many "new technologies" that offered wiz bang effects and gee wiz features that really had nothing to do with fidelity, it is no wonder why hard core audiophiles stick to tubes/vinyl/class A ect. I personally have been exited about digital amplification, be it based on class D or direct amplification, and have been frustrated by peoples casual dismissal of it as just another gimmick. How this technology may be implemented may seem like a trivial question compared to the issues you are dealing with right now, but implementation is where I see many new technologies fail to really catch on. We could have better audio systems NOW if we just brought together all the off the shelf technologies that already exist, let alone implementing new ones. If this device is perfected, maybe it could serv as a leapfrog into a new type of audio system.
Hi,
nowater, why am I under impression that you want to persuade what you consider a group of technically savvy but otherwise misguided people who are willing to share their knowledge (DAX) into making you a digital playground?
I am well aware of Bruno Putzeys opinion regarding all digital power amplifier. In fact I posted the same link before in another thread about Philips digital amplifier.
Now about the merits and problems of various approaches:
Analog modulated switching amplifiers can have feedback taken either from switching stage or even from output filter. Thus they are capable of power supply and output stage distortion rejection. But modulator stage is always a comparator comparing two slow signals: one is usually triangle shaped (either carrier or output from integrator in self oscillating designs and another is almost dc relative to the switching frequency (either output from error amplifier or reference value for hysteresis modulators). This works well as long you have only one half bridge switching leg working. Comparator timing decision is made ahead of switching leg transient so there is no interference. Things radically change when you have a multichannel amplifier. Every switching leg transient introduces several millivolts of noise on slow changing comparator inputs. Result is several nanoseconds of jitter from the output stage. Countermeasures include separate power supply stages for error amplifier, comparator and output stage and elaborate grounding scheme, Bruno Putzeys own US patent 6046636 is a proof of that.
Digitally modulated switching amplifier usually has no feedback, so it has no power supply and output stage distortion rejection. So theoretically it is inferior. But it has very well defined modulator timing with almost no jitter and no crosstalk from other channels in multichannel amplifier. Since modulator can be made almost ideal, only power stage remains the problem. One solution is to use Pulse Edge Delay Error Correction (PEDEC). You can read more about it in the following links: http://bogo-united.oeb.tdk.net/grap..._digital_pulse_modulated_amplifier_system.pdf and http://pearlx.snu.ac.kr/Publication/PESC0203.pdf One might argue that we have analog modulation scheme again, but in case of PEDEC, slopes of signals at comparator inputs are much steeper resulting in less jitter susceptibility.
Another advantage of analog modulation scheme is that you can include output filter in the feedback loop. This is hard to do in the digital domain, but there are remedies. One is multiphase approach. Basically in most switching amplifiers you set corner frequency of output LC filter somewhere between 40 and 80kHz, resulting in max 40dB attenuation at 400Kkz switching frequency. Another trade off in filter design is that you need a relatively small inductance (typically around 20uH) to have correct damping factor with speaker impedance around 6Ohm. With this values there is a few A of ripple current in the inductor, which is consequently removed by output filter capacitor. Now if there is a way of reducing inductor ripple current to a few tens of mA, you might eventually get away with output capacitor. Ripple can be reduced by multiphase ripple cancellation technique, first introduced in Crown BCA amplifier http://www.crownaudio.com/amp_htm/amp_info/bca_op.htm. Another article worth reading of multiphase technique would be: http://bogo-united.oeb.tdk.net/graphics/powerhouse/user_graphics/library/aes_publications/4917.pdf.
It is obvious that multiphase modulation has been conceived with analog modulators, but advantages are lost by noise coupling to the comparator inputs. Easiest way of ripple cancellation is achieved by phase shifted fixed frequency PWM modulated signals which are then summed by inductors
of output stages.
My idea on how to do it on raw sigma delta data stream (let's say this is 2.8MHz DSD) is as follows:you take 8 consecutive data samples from N to N+7 and count number of ones in it. At N+8 you output another 8 cycles long data stream which now has all the counted ones at the beginning and the remaining zeros at the end. At the same time you count ones in another sequence of input data stream from N+8 to N+15 and then output counted ones first. So basically input DSD data stream is transformed into 2.8MHz/8 PWM modulated data stream with 8 level resolution. Now if you take the same algorithm, but process input data from N+1 to N+8, you get another PWM modulated data stream, but this time phase shifted 12.5%. If you again repeat this with another input data set from N+2 to N+9 and so on you eventually have 8 phase shifted PWM modulated data streams, each with 350kHz switching frequency. But the resulting switching frequency after summation is again 2.8MHz not counting ripple current cancellation. This results in almost negligible current ripple at the output. One can also use one transistor and diode (as in Crown BCA) instead of half bridge for each PWM output stage thus reducing complexity. I really don't know how the noise spectra of such manipulation would be, but I hope it would not be worse than before. I wanted to simulate this first before posting the idea, but since you asked for it, here it is.
Best regards,
Jaka Racman
nowater, why am I under impression that you want to persuade what you consider a group of technically savvy but otherwise misguided people who are willing to share their knowledge (DAX) into making you a digital playground?
I am well aware of Bruno Putzeys opinion regarding all digital power amplifier. In fact I posted the same link before in another thread about Philips digital amplifier.
Now about the merits and problems of various approaches:
Analog modulated switching amplifiers can have feedback taken either from switching stage or even from output filter. Thus they are capable of power supply and output stage distortion rejection. But modulator stage is always a comparator comparing two slow signals: one is usually triangle shaped (either carrier or output from integrator in self oscillating designs and another is almost dc relative to the switching frequency (either output from error amplifier or reference value for hysteresis modulators). This works well as long you have only one half bridge switching leg working. Comparator timing decision is made ahead of switching leg transient so there is no interference. Things radically change when you have a multichannel amplifier. Every switching leg transient introduces several millivolts of noise on slow changing comparator inputs. Result is several nanoseconds of jitter from the output stage. Countermeasures include separate power supply stages for error amplifier, comparator and output stage and elaborate grounding scheme, Bruno Putzeys own US patent 6046636 is a proof of that.
Digitally modulated switching amplifier usually has no feedback, so it has no power supply and output stage distortion rejection. So theoretically it is inferior. But it has very well defined modulator timing with almost no jitter and no crosstalk from other channels in multichannel amplifier. Since modulator can be made almost ideal, only power stage remains the problem. One solution is to use Pulse Edge Delay Error Correction (PEDEC). You can read more about it in the following links: http://bogo-united.oeb.tdk.net/grap..._digital_pulse_modulated_amplifier_system.pdf and http://pearlx.snu.ac.kr/Publication/PESC0203.pdf One might argue that we have analog modulation scheme again, but in case of PEDEC, slopes of signals at comparator inputs are much steeper resulting in less jitter susceptibility.
Another advantage of analog modulation scheme is that you can include output filter in the feedback loop. This is hard to do in the digital domain, but there are remedies. One is multiphase approach. Basically in most switching amplifiers you set corner frequency of output LC filter somewhere between 40 and 80kHz, resulting in max 40dB attenuation at 400Kkz switching frequency. Another trade off in filter design is that you need a relatively small inductance (typically around 20uH) to have correct damping factor with speaker impedance around 6Ohm. With this values there is a few A of ripple current in the inductor, which is consequently removed by output filter capacitor. Now if there is a way of reducing inductor ripple current to a few tens of mA, you might eventually get away with output capacitor. Ripple can be reduced by multiphase ripple cancellation technique, first introduced in Crown BCA amplifier http://www.crownaudio.com/amp_htm/amp_info/bca_op.htm. Another article worth reading of multiphase technique would be: http://bogo-united.oeb.tdk.net/graphics/powerhouse/user_graphics/library/aes_publications/4917.pdf.
It is obvious that multiphase modulation has been conceived with analog modulators, but advantages are lost by noise coupling to the comparator inputs. Easiest way of ripple cancellation is achieved by phase shifted fixed frequency PWM modulated signals which are then summed by inductors
of output stages.
My idea on how to do it on raw sigma delta data stream (let's say this is 2.8MHz DSD) is as follows:you take 8 consecutive data samples from N to N+7 and count number of ones in it. At N+8 you output another 8 cycles long data stream which now has all the counted ones at the beginning and the remaining zeros at the end. At the same time you count ones in another sequence of input data stream from N+8 to N+15 and then output counted ones first. So basically input DSD data stream is transformed into 2.8MHz/8 PWM modulated data stream with 8 level resolution. Now if you take the same algorithm, but process input data from N+1 to N+8, you get another PWM modulated data stream, but this time phase shifted 12.5%. If you again repeat this with another input data set from N+2 to N+9 and so on you eventually have 8 phase shifted PWM modulated data streams, each with 350kHz switching frequency. But the resulting switching frequency after summation is again 2.8MHz not counting ripple current cancellation. This results in almost negligible current ripple at the output. One can also use one transistor and diode (as in Crown BCA) instead of half bridge for each PWM output stage thus reducing complexity. I really don't know how the noise spectra of such manipulation would be, but I hope it would not be worse than before. I wanted to simulate this first before posting the idea, but since you asked for it, here it is.
Best regards,
Jaka Racman
DAXgroup said:
let me chime in as a potential user of a DIY amp - 40 watts, even if for each driver, isn't going to be of any interest for me. I have magnepan speakers, and I am seraching for amps that can control these inefficient speakers.
200watts each, and I'm game. I don't think I am alone with this - many owners of inefficient speakers are starting to look at digital as an option.
Peter
Jaka Racman wrote:
I have a distinct feeling that this is even a problem with a single amplifier channel. Since a (analogue) sigma-delta modulator samples at discrete time-intervals it might be less susceptible to this effect than a PWM amp (when the next decision is taken, the overshoots of the last transition etc are already over).
That is just what my imagination tells me, I don't have any mathematical proof for it.
But it makes me enough curious to try it out once.
Regards
Charles
I have a distinct feeling that this is even a problem with a single amplifier channel. Since a (analogue) sigma-delta modulator samples at discrete time-intervals it might be less susceptible to this effect than a PWM amp (when the next decision is taken, the overshoots of the last transition etc are already over).
That is just what my imagination tells me, I don't have any mathematical proof for it.
But it makes me enough curious to try it out once.
Regards
Charles
diy vs commercial developement
Ive been following this thread and thought I would thrown in my observations. I do not have an engineering backround and am just an avid diy enthusiest. I think that digital amps are most definetely the future but as for the basic music buff/DIYer in the here and now, I echo pburkes' opinion. I too have Maggies and the promise of high efficiency and little heat etc. is most attractive for high watt amplification.
Now a 40watt amp for active speakers is fine but I see this as really a commercial product rather than for diy guys. Why would we chose a new, sonically unproven design, when so many wonderful 20 - 50 watt designs are already available. Other than class A, heat really isnt a concern. Ive got several Gainclones that run cool, sound great and are dirt cheap. A 200 watt monoblock that doesnt heat my house, break my back to move, cost a small fortune, or pop the fuses in my house during turn-on (Thresholds monos I borrowed) and you will truely have something. Use for subs alone would be huge I think.
I dont think your average, non-EE type diyer is going to thrown his Aleph away quite yet. Im not sure I would replace any of my 6 amps with one either. Now for packaging in a COMMERCIAL active speaker, multichannel HT in a box, that 40watts is fine. Are we helping design a commercial product or one that can be flexible enough for the wide range of needs we here have?
Im not beening negative, just voicing an opinion that might be held by many of the less vocal and non technical.
amt
Ive been following this thread and thought I would thrown in my observations. I do not have an engineering backround and am just an avid diy enthusiest. I think that digital amps are most definetely the future but as for the basic music buff/DIYer in the here and now, I echo pburkes' opinion. I too have Maggies and the promise of high efficiency and little heat etc. is most attractive for high watt amplification.
Now a 40watt amp for active speakers is fine but I see this as really a commercial product rather than for diy guys. Why would we chose a new, sonically unproven design, when so many wonderful 20 - 50 watt designs are already available. Other than class A, heat really isnt a concern. Ive got several Gainclones that run cool, sound great and are dirt cheap. A 200 watt monoblock that doesnt heat my house, break my back to move, cost a small fortune, or pop the fuses in my house during turn-on (Thresholds monos I borrowed) and you will truely have something. Use for subs alone would be huge I think.
I dont think your average, non-EE type diyer is going to thrown his Aleph away quite yet. Im not sure I would replace any of my 6 amps with one either. Now for packaging in a COMMERCIAL active speaker, multichannel HT in a box, that 40watts is fine. Are we helping design a commercial product or one that can be flexible enough for the wide range of needs we here have?
Im not beening negative, just voicing an opinion that might be held by many of the less vocal and non technical.
amt
I think the response is again "you have to walk before you can run." At the moment we have exactly zero end-to-end DIY digital solutions. This project is the first step in realizing that, and it is great that it is being designed from the ground up as flexible enough to accomadate various topologies. I think the emphasis is on gaining the knowledge to move from 1st generation to 2nd generation, not on replacing all existing analog amplifiers.
Hi,
to those that a concerned with 40 watt power limitation of current design, this is only a technology demonstrator. Digitally modulated switching amplifiers can scale far better than analogly modulated, since power stage and modulator stage a totally separated. Here is an estimate of currently possible technology:
-supply voltage around 400V due to 450V electrolytic capacitor rating.
-switching frequency up to 350kHz with use of Coolmos FETs and SiC schottky diodes.
-current capability around 10A per switching leg with such frequencies. Paralleling of switching legs is required, but with summation on output inductors, not by direct FET paralleling. Ideal for multiphase design.
So with modulating index at 0.8 and full bridge design, one can output 720V peak to peak sine wave or 8100W into 8ohms. Enough to drive Maggies (I also own them). It may sound preposterous, but it is technically entirely possible.
Best regards,
Jaka Racman
to those that a concerned with 40 watt power limitation of current design, this is only a technology demonstrator. Digitally modulated switching amplifiers can scale far better than analogly modulated, since power stage and modulator stage a totally separated. Here is an estimate of currently possible technology:
-supply voltage around 400V due to 450V electrolytic capacitor rating.
-switching frequency up to 350kHz with use of Coolmos FETs and SiC schottky diodes.
-current capability around 10A per switching leg with such frequencies. Paralleling of switching legs is required, but with summation on output inductors, not by direct FET paralleling. Ideal for multiphase design.
So with modulating index at 0.8 and full bridge design, one can output 720V peak to peak sine wave or 8100W into 8ohms. Enough to drive Maggies (I also own them). It may sound preposterous, but it is technically entirely possible.
Best regards,
Jaka Racman
Be assured we are not craving for help in any way. We started this project from scratch, and we all have the technical background to push it further. The reason we are posting here was stated in the first post. We believe the current design has reached a milestone and other people might be interested to experiment on Class D. By making the design open-source, people could share their discoveries and we would all end up with a better product.
Totally agree with you on that. However, we believe that class D amplifiers have a very promising future and that they will eventually give better results than the regular dac/amplifier solution. What we meant is that in order to get there, we need to work on it...
One last word on output power: Please go on our website, read the documents and understand them. The output power of the amplifier only depends on the POWER SUPPLY VOLTAGE. If you need more, build yourself another output stage and power supply. You want 2000W, go ahead and share the design with others:
http://www.irf.com/product-info/audio/fsaudio.html#full8
Exactly.
Jaka Racman:
We are currently carefully reading with a lot of interest the papers you referenced to. The way you are proposing to do it should be easy to implement with the current platform. We have models of the amplifier in Matlab and vhdl, and it should be easy to generate the 8 output streams for FFT analysis. Tell us if it would help. Test results could be stored in text file for Spice simulations. Very interesting stuff. Hope to see more of that.
Technical rationality / customer attractability balance take to analog class D side today (cheap, figures&sound - nice, D still associated with Digital), what about tomorrow if in Yamaha DVX S120 specs, we can read "Digital amplifier", but not this "One of the best analog class D at this planet"?
Best regards Ivan.
Best regards Ivan.
Jaka Racman said:
sign me up for a pair of those
I want to vaporize my tweeters next time I get the amps to clip!Seriously - I am in this for the power - I currently run Odyssey Mono Extreme SS amps, and they deliver very good power, but I want to bi-amp or triamp, which gets far too expensive even with these direct-marketed amps. DIY with class D is the answer. I'm looking at the LCaudio modules right now, but this project here seems worth holding back and keeping an eye on what shapes up, given there's a kilowatt or more in the final implementation
Peter
Hi everyone,
We think it's the moment for a clarification on the situation. For the moment, we lost our interest in releasing our work in open-source. There are still too many people simply interested in a ready-made solution compared to the amount of people that would have the capabilities and interest in bringing real advancement to the project.
We have the will to keep the post alive, but we will do it just like any other project around here: show our progress and keep on asking for suggestion (people have great ideas...). Going into the process of releasing everything in open-source would simply be too much work. Having people understand the basics of the project is already a tedious task. We prefer put these efforts on working on the project directly.
The point is that the timing was probably simply wrong. The 40W output seems to be a big limitation to a lot of people and became the main topic of the thread, even if it is only a matter of building another output stage. This is probably directly linked to the fact that, as we said, people prefer a ready-made project. We never though that DIY would be so close to plug-and-play. The fact is that with a near-final project, the interest would probably be completely different. Therefore, we propose ourselves to develop the following aspects of the project:
- 100W+++ output stage (magic number even if often irrelevant)
- 3-way linear phase output
- Feedback to relax the constraints on the power supply
- 5.1 support
- Etc.
However, in our brief immersion in the DIY world, we have met very knowledgeable people on specific subjects. These people with their ideas guided the future of the project. We will contact these people personally and ask for their opinion.
As we said, we are willing to keep the post alive, but put away our will to release anything for the moment. This forum is a great source of information and ideas but it is unrealistic to have the project evolve here in an open-source fashion.
Nevertheless, if anybody is still interested in obtaining the DAX platform, please contact us directly. We would be more than happy to produce boards in small quantity.
Unfortunately, Jean-Pierre saw the situation from the very start.
Best Regards,
DAX Group
We think it's the moment for a clarification on the situation. For the moment, we lost our interest in releasing our work in open-source. There are still too many people simply interested in a ready-made solution compared to the amount of people that would have the capabilities and interest in bringing real advancement to the project.
We have the will to keep the post alive, but we will do it just like any other project around here: show our progress and keep on asking for suggestion (people have great ideas...). Going into the process of releasing everything in open-source would simply be too much work. Having people understand the basics of the project is already a tedious task. We prefer put these efforts on working on the project directly.
The point is that the timing was probably simply wrong. The 40W output seems to be a big limitation to a lot of people and became the main topic of the thread, even if it is only a matter of building another output stage. This is probably directly linked to the fact that, as we said, people prefer a ready-made project. We never though that DIY would be so close to plug-and-play. The fact is that with a near-final project, the interest would probably be completely different. Therefore, we propose ourselves to develop the following aspects of the project:
- 100W+++ output stage (magic number even if often irrelevant)
- 3-way linear phase output
- Feedback to relax the constraints on the power supply
- 5.1 support
- Etc.
However, in our brief immersion in the DIY world, we have met very knowledgeable people on specific subjects. These people with their ideas guided the future of the project. We will contact these people personally and ask for their opinion.
As we said, we are willing to keep the post alive, but put away our will to release anything for the moment. This forum is a great source of information and ideas but it is unrealistic to have the project evolve here in an open-source fashion.
Nevertheless, if anybody is still interested in obtaining the DAX platform, please contact us directly. We would be more than happy to produce boards in small quantity.
Unfortunately, Jean-Pierre saw the situation from the very start.
Best Regards,
DAX Group
Hi,
DAX, I am glad that you find idea interesting and you are willing to spend time to simulate. Please post the results when you are finished. I also hope that someday you will post your Matlab model. For some time now I have a desire to start learning Matlab, and your model would provide great motivation. Spice is not so great for digital hardware simulation.
Best regards,
Jaka Racman
P.S> I started this post before I saw yours. While I was typing I was thinking that something like this was bound to happen.
Digital section of this forum is relatively small and major part of posts here deals with merits of capacitor changing on existing designs.
DAX, I am glad that you find idea interesting and you are willing to spend time to simulate. Please post the results when you are finished. I also hope that someday you will post your Matlab model. For some time now I have a desire to start learning Matlab, and your model would provide great motivation. Spice is not so great for digital hardware simulation.
Best regards,
Jaka Racman
P.S> I started this post before I saw yours. While I was typing I was thinking that something like this was bound to happen.
Digital section of this forum is relatively small and major part of posts here deals with merits of capacitor changing on existing designs.
DAXgroup,
I'm sorry that you were disappointed with the response. I don't think you should be; it is only natural that in an unmoderated atmosphere such as DIYaudio you will end up getting lots of feedback that is unhelpful when you make a blanket statement like "how can we improve X." What is unfortunate is that there are probably knowledgable folks who have not commented because they were waiting to see if the platform would materialize or would remain vaporware. I think we are all familiar with schedules slipping and some of us perhaps are a bit jaded about product announcements. I also think you underestimate the desire to tweak and to learn new things that many of us DIY people have.
I think any effort in the future could incorporate a forum like DIYaudio but certainly would need its own CVS and developer mailing list, etc. (ala Sourceforge) for the main effort.
Best of luck in your endeavor and I hope to see some updates on your efforts at some point in the future.
Tiroth
I'm sorry that you were disappointed with the response. I don't think you should be; it is only natural that in an unmoderated atmosphere such as DIYaudio you will end up getting lots of feedback that is unhelpful when you make a blanket statement like "how can we improve X." What is unfortunate is that there are probably knowledgable folks who have not commented because they were waiting to see if the platform would materialize or would remain vaporware. I think we are all familiar with schedules slipping and some of us perhaps are a bit jaded about product announcements. I also think you underestimate the desire to tweak and to learn new things that many of us DIY people have.
I think any effort in the future could incorporate a forum like DIYaudio but certainly would need its own CVS and developer mailing list, etc. (ala Sourceforge) for the main effort.
Best of luck in your endeavor and I hope to see some updates on your efforts at some point in the future.
Tiroth
It is a fact that there is limited volume in the digital section
My own experience also indicates that unless one is lucky enough to hit the nail on the head, this forum is best used for idea generation and single point assistance (for which is it incredible), rather than true design assistance. It is also true that many of us get enough joy out of doing relatively simple upgrades of existing designs rather than revolutionary new work. It is also a fact that most of us are amateurs and not all that well versed in more than one or two areas - that way, we probably reflect many of the employees in commercial audio companies but those guys work as a team). One should not place value judgement on that and I expect this forum will grow.
It is also pretty clear that a thread rarely has high activity longer than several weeks unless there is an engine adding new stuff continuously.
What is also quite clear to me is that with few exceptions, those who have great ideas are often unwilling to share. In this regard your openness is exemplary!
Can you please explain the 3 way linear phase function - is this multi-phase output?
I for one hope that you will devote all your attention to producing a super-high quality output stage rather than divert to non-ground-breaking integration scenarios that anyone with half a brain and enough time can do
Fixing a crummy power-supply with feedback is also something that saddens me - if you look into Sandler et al's work (London), you will see they were unable to integrate feedback with enough speed to make it a positive addition to the project. A better approach would be an adaptive algorithm unless you are confident that you can get the feedback (and it must be done in the digital domain) fast enough, fine.
If you want to go down in history, it is the quality of the individual technology which will enable you to reap such rewards be them financial or community hero oriented. Think Linux where the KernelMeister is king.
Petter
My own experience also indicates that unless one is lucky enough to hit the nail on the head, this forum is best used for idea generation and single point assistance (for which is it incredible), rather than true design assistance. It is also true that many of us get enough joy out of doing relatively simple upgrades of existing designs rather than revolutionary new work. It is also a fact that most of us are amateurs and not all that well versed in more than one or two areas - that way, we probably reflect many of the employees in commercial audio companies but those guys work as a team). One should not place value judgement on that and I expect this forum will grow.
It is also pretty clear that a thread rarely has high activity longer than several weeks unless there is an engine adding new stuff continuously.
What is also quite clear to me is that with few exceptions, those who have great ideas are often unwilling to share. In this regard your openness is exemplary!
Can you please explain the 3 way linear phase function - is this multi-phase output?
I for one hope that you will devote all your attention to producing a super-high quality output stage rather than divert to non-ground-breaking integration scenarios that anyone with half a brain and enough time can do
Fixing a crummy power-supply with feedback is also something that saddens me - if you look into Sandler et al's work (London), you will see they were unable to integrate feedback with enough speed to make it a positive addition to the project. A better approach would be an adaptive algorithm unless you are confident that you can get the feedback (and it must be done in the digital domain) fast enough, fine.
If you want to go down in history, it is the quality of the individual technology which will enable you to reap such rewards be them financial or community hero oriented. Think Linux where the KernelMeister is king.
Petter
Dax, you have to remember that this forum contains all types of audio DIY'ers, from bigginers to experts, and in all realms of audio. I may have asked "stupid" questions, but my forte is speaker design, not amp design. You seem to have taken offence to some of the questions and comments posted, but I would suggest to you that I and others really just wanted more information because this project sparked out interest. Even if those of us who don't have the technical expertise to really help at this point; I hope that you see it as healthy to the project to keep people learning and interested about it. I understand if it seems like a tedious waste of time to try to educate those of us with only a very basic knowlege of digital amplification, but if you could keep us posted with additional links of info as you can do it, I think I and others would appreciate it, and then when the project is farther along would could actually contribute something of value. I think a thread starter like "high end digital amplification for eveyone" is rather audacious, and kindof challenges people to see "whats in it for them". There is just no need to be defensive or *****ly about it. You seem to have at least gotten some value out of these discussions, which I would hope you could see as worthwhile, even if it didnt' meet youre very high expectations. Let's face it, were just not all engineers in here, so PLEASE have an open mind and a sense of humor!
I think he was talking about an intrinsic digital three-way crossover that is phase linear (or phase_accurate).
Dax:
You have to keep in mind that not all people here come from the electronics area. Many just build readily available designs, which is nothing wrong and still fun and educational.
Not everyone has the mathematical skills and imagination to fully understand how DSP and especially noise-shaping works.
I am currently dealing with an analog delta-sigma amp topology. If I would come accross an idea that would be helpful to you I would certainly not keep it for myself.
Regards
Charles
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