hi.
our pwm amps are clock controlled, their upper f3 is dependant on the actual design (we have several) and they behave very well into capacitive and inductive loads (the ones relevant to audio....) meaning they are stable into these.
charles, you said earlier you would be among the first to buy decent pwm amplifier boards , what is your application?
rgds karsten madsen - www.cadaudio.dk
our pwm amps are clock controlled, their upper f3 is dependant on the actual design (we have several) and they behave very well into capacitive and inductive loads (the ones relevant to audio....) meaning they are stable into these.
charles, you said earlier you would be among the first to buy decent pwm amplifier boards , what is your application?
rgds karsten madsen - www.cadaudio.dk
Good news
Hi Charles,
I think that good developed math models, basically used for motor control, today can be successful to improvement class D amps (smart example- mueta), because this tasks is very similar and, actually, different just at the speed. Semiconductors progress gives us easy possibility to test it..TDA8938-Zerodeadtime Class-D Power Comparator
-Zero deadtime ( <10nS, just less then rise(fall) time)
- Stereo half-bridge (2 x SE) or mono full-bridge (1xBTL) application
- Standby mode
- High efficiency
- Operating voltage from +/- 7.5 V to +/- 30 V
- Low quiescent current
- Low noise, low offset
- High output power
- Short-circuit proof across the load
- Diagnostic output
- Thermal-, current- and voltage protections
-tRESP-100nS
-rise(fall) time output voltage-20nS
-DBS27P-package
Seems it coming soon.
Merry Christmass!
Ivan.
Hi Charles,
I think that good developed math models, basically used for motor control, today can be successful to improvement class D amps (smart example- mueta), because this tasks is very similar and, actually, different just at the speed. Semiconductors progress gives us easy possibility to test it..TDA8938-Zerodeadtime Class-D Power Comparator
-Zero deadtime ( <10nS, just less then rise(fall) time)
- Stereo half-bridge (2 x SE) or mono full-bridge (1xBTL) application
- Standby mode
- High efficiency
- Operating voltage from +/- 7.5 V to +/- 30 V
- Low quiescent current
- Low noise, low offset
- High output power
- Short-circuit proof across the load
- Diagnostic output
- Thermal-, current- and voltage protections
-tRESP-100nS
-rise(fall) time output voltage-20nS
-DBS27P-package
Seems it coming soon.
Merry Christmass!
Ivan.
The manufacturer of this IC is Philips semiconductors, but seems it's a still future product. IMHO it's just a dream for any class D research- no need more comparator, voltage shifter, driver & mosfets..just turn ON 8938!
<BTW: What are the THD and noise figures of your amp ? Were you able to measure them at all (I know that they may be of second importance for subwoofer applications) ? >
Are you mean 8938? I not have any experiense with it so far. I currently not able to measuring THD at >5Khz with enough precision by using PC sound card, but other method(so hard & just RMS of THD+NOISE, at 100hz it's have no so bad correlation with sound card results ) for it also is exist/able - proportional&phase in/out compensation .
Regards
Ivan.
<BTW: What are the THD and noise figures of your amp ? Were you able to measure them at all (I know that they may be of second importance for subwoofer applications) ? >
Are you mean 8938? I not have any experiense with it so far. I currently not able to measuring THD at >5Khz with enough precision by using PC sound card, but other method(so hard & just RMS of THD+NOISE, at 100hz it's have no so bad correlation with sound card results ) for it also is exist/able - proportional&phase in/out compensation .
Regards
Ivan.
hi.
>A WEB-search for TDA8938 returned no answer>
and a search at philips didnt either
did anybody say vaporware??
i suggest that the discussion focus a bit more on things that do actually exist.....
it seems to me that often there is more focus on published specs than sound quality , does everybody here believe there is a close relation between these??
in my mind it would be interesting to have unbiased tests and comparisons of different pwm amplifiers , comparing the better ones to good "normal" amplifiers, if anybody has ideas for these let me hear from you.
best regards and merry christmas -
karsten madsen - www.cadaudio.dk
>A WEB-search for TDA8938 returned no answer>
and a search at philips didnt either
did anybody say vaporware??
i suggest that the discussion focus a bit more on things that do actually exist.....
it seems to me that often there is more focus on published specs than sound quality , does everybody here believe there is a close relation between these??
in my mind it would be interesting to have unbiased tests and comparisons of different pwm amplifiers , comparing the better ones to good "normal" amplifiers, if anybody has ideas for these let me hear from you.
best regards and merry christmas -
karsten madsen - www.cadaudio.dk
Well....
Sometimes there is, sometimes there isnt .......
As already mentioned, we listened to music with the class-d amp that I once developed and it sounded nice and detailed (despite of having a THD of 0.44%, mainly consisting of k2, and a faint HF hiss).
BUT:
We only listened to one channel AND we didn't make any comparisons to other amps. And I can't claim to be unbiased either ......
As far as data goes: That's the only thing you can compare when you see aproduct on paper only. One just can't buy all available class-d amp modules in order to find out how they actually sound like !!
Ivan:
I meant your own amploiD design of course !
Regards
Charles
<did anybody say vaporware??
<i suggest that the discussion focus a bit more on things that do actually exist.....
I'm sorry, Karsten you are right... (but I can dream, that poste will be working well and i'll try "vaporware" at the next week yet?)
I just thought, that it's good news to people which haven't enough time for soldering, but there is enough time for ideas creation, IMHO it's a basic DIY motivation in general.
Charles:
About amploiD 3L (use ir2111 with 650nS dead time, -90db noise )i already wrote here http://www.diyaudio.com/forums/showthread.php?postid=238331#post238331. (Full version at ir2110 about 0.003% THD.) Probably the PCB's 3.2-3.3L, shared in amploid.narod.ru, contain mistake- lines from driver to mosfets is long too much, because i can't stop myself in permanent improvement desires(11 versions of this PCB are exist), in result lost some tricks...typical DIYer. BCA topology is the best solution, without hard changing this PCB. Simplest improvement THD figures for 3L also exist, but it take some time for adjusting.
Best regards
Ivan.
<i suggest that the discussion focus a bit more on things that do actually exist.....
I'm sorry, Karsten you are right... (but I can dream, that poste will be working well and i'll try "vaporware" at the next week yet?)
I just thought, that it's good news to people which haven't enough time for soldering, but there is enough time for ideas creation, IMHO it's a basic DIY motivation in general.
Charles:
About amploiD 3L (use ir2111 with 650nS dead time, -90db noise )i already wrote here http://www.diyaudio.com/forums/showthread.php?postid=238331#post238331. (Full version at ir2110 about 0.003% THD.) Probably the PCB's 3.2-3.3L, shared in amploid.narod.ru, contain mistake- lines from driver to mosfets is long too much, because i can't stop myself in permanent improvement desires(11 versions of this PCB are exist), in result lost some tricks...typical DIYer. BCA topology is the best solution, without hard changing this PCB. Simplest improvement THD figures for 3L also exist, but it take some time for adjusting.
Best regards
Ivan.
Again off-topic..
Hi subwo1,
Actually i like PCB(with SMD parts especially), maybe because just so doing:
A) Print layer to film (cheapest Epson c40 by 3 pass (for paint density) have not any picture shifting)
B) Positiv 20 (made in Belgium, 200ml about $10) spraying to board.
C) 10 min. exposing under Ultraviolet lamp... etc.
D) Soldering.
E) Measurement.
F) If all is ok then(oh God please keep out my hands to any changes) order that to make 10 PCB's (2 layer, 110x110mm, no drilling) $1/PCB.
You have already soldered N-champ? BTW, you have understood how Microcap THD analyze? (see for example *:/MC7/DATA/tube_amp.cir). I begin use PSpice, and, (the contrary to my respect to people which recommended use it (as excellent)), i can't call PSpice convenient for me so far, but I'll continue certainly. (so wise man as Charles use it too
Best regards
Ivan.
Hi subwo1,
Actually i like PCB(with SMD parts especially), maybe because just so doing:
A) Print layer to film (cheapest Epson c40 by 3 pass (for paint density) have not any picture shifting)
B) Positiv 20 (made in Belgium, 200ml about $10) spraying to board.
C) 10 min. exposing under Ultraviolet lamp... etc.
D) Soldering.
E) Measurement.
F) If all is ok then(oh God please keep out my hands to any changes) order that to make 10 PCB's (2 layer, 110x110mm, no drilling) $1/PCB.
You have already soldered N-champ? BTW, you have understood how Microcap THD analyze? (see for example *:/MC7/DATA/tube_amp.cir). I begin use PSpice, and, (the contrary to my respect to people which recommended use it (as excellent)), i can't call PSpice convenient for me so far, but I'll continue certainly. (so wise man as Charles use it too
Best regards
Ivan.
Hi Ivan, did you forget etching? Do you use ferric chloride?
I think I hate PCB's because I am not trying to sell my idea for profit. I guess I want someone else to do all the work and make all the money also. I just want to do design research. I know parts layout on a PCB could qualify, but maybe I am just too lazy or something.
I have not tried to check distortion with MicroCap, but maybe should. I will try to check into it.
I have LT-spice which I think is like Pspice, but do not like it. It is just too hard for me. Pick your choice, either I am lazy or dumb.
Take Care
Etching would be after step C?
I think I hate PCB's because I am not trying to sell my idea for profit. I guess I want someone else to do all the work and make all the money also. I just want to do design research. I know parts layout on a PCB could qualify, but maybe I am just too lazy or something.
I have not tried to check distortion with MicroCap, but maybe should. I will try to check into it.
I have LT-spice which I think is like Pspice, but do not like it. It is just too hard for me. Pick your choice, either I am lazy or dumb.
Take Care
Hi
As usual the thread is jacked...
The subject of the thread is: Class A/ A-B vs. D.
Completely non commercial, but very interesting discussion about YOUR opinion on one vs. the other.
But but but .......now it is starting to be a commercial for the usual 'i-start-with-one-pcb-on-my kitchen-table-then-after-a-few-weeks-you-can-buy-my-pcb-which-is-much-much-better" people.
Ivan: why don't you start your own: "Buy Ivan's PWM amp" thread?
As usual the thread is jacked...
The subject of the thread is: Class A/ A-B vs. D.
Completely non commercial, but very interesting discussion about YOUR opinion on one vs. the other.
But but but .......now it is starting to be a commercial for the usual 'i-start-with-one-pcb-on-my kitchen-table-then-after-a-few-weeks-you-can-buy-my-pcb-which-is-much-much-better" people.
Ivan: why don't you start your own: "Buy Ivan's PWM amp" thread?
It would seem that class d amps which take the feedback from after the output filter (Icepower, Mueta, Philips UCD& SODA, Spectron) have much lower distortion figures, and better specs all the way around, than those that take the feedback from before the filter (Tripath, zap pulse, and others).
I really haven´t enough knowledge about these amps to fully understand what is really hapening but..
I think Lars mentioned that he had tried post-filter feedback with not much of a diffrence in THD in the Zapulse... or was it someone else?
Seems like feedback after the filter is the way to go for bass and midrange applications without doubt. And as I said earlier, class A amp for the tweets until the PWM amps are fast enough to handle the 1k-20k range without compromise.
/Peter
I think Lars mentioned that he had tried post-filter feedback with not much of a diffrence in THD in the Zapulse... or was it someone else?
Seems like feedback after the filter is the way to go for bass and midrange applications without doubt. And as I said earlier, class A amp for the tweets until the PWM amps are fast enough to handle the 1k-20k range without compromise.
/Peter
hi.
pan i think you should hear some of the better pwm amps
im sure feedback after the output filter is way to go for all pwm amps , perhaps in some it doesnt give much improvement but i think this is due to other factors.
sorry if im repeating myself but i think that usable opinions about class-d ctr. class a or a/b is only valid from those who has a reasonable background to talk from , meaning those who have actually heard some of the better types from both camps , right?
my personal feeling is that this is perhaps 1-2 guys here at most
im gettting a little bored with the usual hear-say and the usual talk about good static thd specs, i have heard and compared boards with good (published) specs and the good specs didnt help much re. sound quality.
happy new year to all.
karsten madsen - www.cadaudio.dk
ps. the easiest way to get low thd numbers is simply to lie and imho this is also used quite often.....
pan i think you should hear some of the better pwm amps
im sure feedback after the output filter is way to go for all pwm amps , perhaps in some it doesnt give much improvement but i think this is due to other factors.
sorry if im repeating myself but i think that usable opinions about class-d ctr. class a or a/b is only valid from those who has a reasonable background to talk from , meaning those who have actually heard some of the better types from both camps , right?
my personal feeling is that this is perhaps 1-2 guys here at most
im gettting a little bored with the usual hear-say and the usual talk about good static thd specs, i have heard and compared boards with good (published) specs and the good specs didnt help much re. sound quality.
happy new year to all.
karsten madsen - www.cadaudio.dk
ps. the easiest way to get low thd numbers is simply to lie and imho this is also used quite often.....
.... or to measuere them in a very favourable way !!!!!
I had the opportunity to listen to the TacT millennium and the Sharp SM-SX100.
One interesting feature was their low-end punch, despite their quite moderate output power specs. And both were nice and easy on the ears (at least on mines, someone else might not like them at all). BTW: both of these don't have the lowest THD specs of all available class-d amps and both take feedback from the switching stage.
I also had the opportinity to take part in a 2+2+2 demo (someone once invented the expression "cinema for the blind" which that one in fact was !!!!) using the Dynaudio Air series active studio monitors. These use class-d amps throughout and they sounded nice as well. I don't have any details on these amps other than the hint that they are made by the Danish company TC electronics (not to be mistaken with the American woofer manufacturer).
The low THD specs of the ICE-power modules are gained by very high NFB factors which they achieve with their multiple feedback loop topology. I don't know how they actually sound so far. Even though there is a B&O dealer quite close to my workplace, where one could listen to the two larger Beolab models, that are both using ICE-power modules, I was way too lazy so far to go there and have a listen. Maybe it is just because I have the opinion that this (once cool) company has migrated to a "toy manufacturer".
Regards
Charles
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