| Joep Zonnebloem |
Hello,
I am a bass player, in the process of building a bass amplifier with class d modules (Zappulse 2.3SE). I have been following some of the class d threads here for some 3 months and I enjoy very much reading the various opinions and ideas of all those different people. I also, in my modest way, learn a lot of them, although I am far from a natural born technician. So far I have constructed a rather untidy (to say the least) kind of test version. I am rather ashamed to show it, considering some of the really beautiful designs of other people in other threads; the picture serves only to indicate in which stage and at what level I am presently. Sadly, it also demonstrates that I need a better camera :)
The sound of it, however, is beautiful; Lows and mid are deep and warm but fast responding and accurate; the highs and top-highs are crunchy, with only very simple and minimal equalization. It also has a nice, substantial and compact thump in the gut and a pleasant attack.
I feel rather presumptious to start a new topic just like that. My knowledge of electronics is kind of limited; I understand some of the behaviour of some common components in some simple circuits and I am aware of some of the topologies in class D and smps. So go learn, you would say. Well, I decided to accept my limitations and also accept the fact that I dont have enough time (ok, maybe also energy) to go as deep into it myself as would be neccessary to find real solutions. Still, I want to build that nice amplifier and there are a couple of aspects on building with the populare modules (like from Hypex, LCAudio, B&O) that I cannot find specific information on that matches my level and/or purposes. My hope is that other people out there may be in the same line, or at least are willing to contribute with their knowledge on the issue(s) below:
SMPS. (Oh, no, not again. yes, again, hear me out).
As I have understood, switched mode power supplies are much too noisy to be acceptable in a hifi configuration. Hiss, hum or crakle from the speakers can destroy any good music that needs some dynamics, and lets forget about recording altogether. However, I am not primarily interested in extremely low noise-levels. Any bass-stack, whether it be an Ampeg, SWR, Eden or even Aguilar or whatever, will produce some significant hiss and hum when you turn up the volume and listen close. Maybe a few, more or less dedicated, studio amplifiers will be very quiet, but then, in many cases those are not very good in live situations. So I am completely willing to accept some steady noise, as long as it does not follow the dynamics in my playing. One should think that this would loosen some of the restrictions on an smps design. I mean, I sense a tendency that certain specifications are to be matched by default, while I (and I hope more people) would happily give them up, to a certain extend, in return for suffucient power (talking in the range of 1000-2000W) and resistance to the phenomenon of power supply pumping. So that is my aim: A switched mode power supply that is powerfull and suitable for steady bass amplification and that not neccessarily has to be high-end. It would make the difference between a 3 or 4 unit high, 50cm (20) deep, 25 kg (50 pounds) 19 housing containing large toroids and a 2 unit high, 12 deep 15 to 20 pounds housing. This is very important when you have to carry around a 19 rack, possibly also containing a preamp, sound/effectsprocessor, BassPod or the likes.)
There have been some threads dealing with smps for class d: in the thread SMPS design for power amps (Class D in particular) ( http://www.diyaudio.com/forums/show...&threadid=41211 ), some very creative and skilled technicians (a.o. Bruno Putzeys, analogspiceman, .) have been discussing SMPS design on a high theoretical level. The real content of their postings was way byond my comprehension, but very interesting at the same time. The thread died at the end of november 2004.
In the thread about Icpower modules for PA applications, the issue emerges as well on a somewhat more human level. It seems a very complicated matter, e.g.: because of the limit that the smps design seems to impose on the capacitance of the output caps, the supply is in danger in case power supply pumping occurs. There are some smpss available, though, as many who have been around here may already know. One is the A and T labs smps ( http://www.a-and-t-labs.com/K6_Sw_Amp/index.htm ) of 1000W, designed to power some 2 x 300W or so class A/B amplifier. However, its design stems from 1995 and one may assume that new insights on the issue have evolved since then. Furthermore, it has small output caps and it seems to control only the output voltage rate and not the symmetry, which would make it defenseless against a pumping class D module. (thanks for the explanation, Ghemink, I hope I have understood it well). Other smpss for poweramplifiers are available at http://www.cadaudio.com . They are designed to work well with their own cadaudio modules and with the Icpower ones, which are fullbridged and do not suffer from power supply pumping. Sadly, mainly for this reason they also are not sold seperately.
There MUST be some design possible that would match my (and, again, hopefully others) requirements. This is illustrated, for example, by the fact that Hevos, a Dutch manufacturer of high quality bassgear, will be introducing a bass top this spring that has a tubedriven preamp and a (or more) UCD module(s) from Hypex (not coincidentally the company that Bruno Putzeys works for.), all together in a 2 unit high lightweight 19 housing. I mailed them in the hope to get some information about the setup, but understandably they would not go into details, as they told me in their friendly reply.
So, concluding this too long story: that is what its about. A practical SMPS. I would be happy to see some postings containing info that could help me and possibly others. If not, ok, the thread will sink in the list and dissapear out of sight, big deal. But i think its woth a try. And if, lets try to stick to the topic. I must admit that I myself posted some messages here and there in the past that were more or less off-topic, or not helpful or relevant at all. Im still a little uncertain in my forum-manners (maybe demonstrated by the novel-length of this message..? Sorry)
Besides the SMPS, any ideas on preamping the class D amp would also be highly appreciated. But the main issue will stay smps.
Though its high time to end this introduction, still a few words about myself:
I have been playing bass on (semi-) professional level from the late 70s till the early 90s. I played jazz, fusion, rock, blues and aside from that basically anything that would get me some mony, on fretted/unfretted electric bass and upright bass. Sometimes it was good for a living, sometimes not nearly close. I was a studier, practiced a lot and yet did not reach the level I had in mind. On the contrary, eventually I did not know anymore how to play a normal, functional bassline and in 1990 I decided to try and find a decent job, in which I succeeded. Presently, I am a database consultant (like many flipped musicians, philosophers, sociologists, teachers and the likes) and I like what I am doing. Recently, I started playing again, motivated by a small gig I had been asked for and I noticed how much I missed the feeling and how much a musician I am in my heart. I am also less blocked by ambition and I like searching for good basslines now, played with a good sound.
I am, and have always been, a great admiror of the late Jaco Pastorius.
Electronics: I am pretty comfortable as long as Ohms law and some other basic formulas are applicable in simple equations. Byond that, I tend to get heavily lost. My most creative idea so far was a power supply without transformer, i.e. using rectified and buffered mains AC without any galvanic isolation. In Holland, we use 230V rms, which would render some 320V DC on the rail. The Zappulse in my testamp uses +/- 80V (so, 160V). In some kind of symmetrical setup my supply could power 2 modules. After some rethinking I began to suspect that it would probably mean the surest one way ticked to heaven, where I could serve as a human 320V capacitor for Jacos bass rig
Best regards, Joep |
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|
| ghemink |
| quote: | Originally posted by Joep Zonnebloem
Hello,
I am a bass player, in the process of building a bass amplifier with class d modules (Zappulse 2.3SE). I have been following some of the class d threads here for some 3 months and I enjoy very much reading the various opinions and ideas of all those different people. I also, in my modest way, learn a lot of them, although I am far from a natural born technician. So far I have constructed a rather untidy (to say the least) kind of test version. I am rather ashamed to show it, considering some of the really beautiful designs of other people in other threads; the picture serves only to indicate in which stage and at what level I am presently. Sadly, it also demonstrates that I need a better camera :)
The sound of it, however, is beautiful; Lows and mid are deep and warm but fast responding and accurate; the highs and top-highs are crunchy, with only very simple and minimal equalization. It also has a nice, substantial and compact thump in the gut and a pleasant attack.
I feel rather presumptious to start a new topic just like that. My knowledge of electronics is kind of limited; I understand some of the behaviour of some common components in some simple circuits and I am aware of some of the topologies in class D and smps. So go learn, you would say. Well, I decided to accept my limitations and also accept the fact that I dont have enough time (ok, maybe also energyE to go as deep into it myself as would be neccessary to find real solutions. Still, I want to build that nice amplifier and there are a couple of aspects on building with the populare modules (like from Hypex, LCAudio, B&OE that I cannot find specific information on that matches my level and/or purposes. My hope is that other people out there may be in the same line, or at least are willing to contribute with their knowledge on the issue(s) below:
SMPS. (Oh, no, not againE yes, again, hear me out).
As I have understood, switched mode power supplies are much too noisy to be acceptable in a hifi configuration. Hiss, hum or crakle from the speakers can destroy any good music that needs some dynamics, and lets forget about recording altogether. However, I am not primarily interested in extremely low noise-levels. Any bass-stack, whether it be an Ampeg, SWR, Eden or even Aguilar or whatever, will produce some significant hiss and hum when you turn up the volume and listen close. Maybe a few, more or less dedicated, studio amplifiers will be very quiet, but then, in many cases those are not very good in live situations. So I am completely willing to accept some steady noise, as long as it does not follow the dynamics in my playing. One should think that this would loosen some of the restrictions on an smps design. I mean, I sense a tendency that certain specifications are to be matched by default, while I (and I hope more people) would happily give them up, to a certain extend, in return for suffucient power (talking in the range of 1000-2000W) and resistanceEto the phenomenon of power supply pumping. So that is my aim: A switched mode power supply that is powerfull and suitable for steady bass amplification and that not neccessarily has to be high-end. It would make the difference between a 3 or 4 unit high, 50cm (20E deep, 25 kg (50 pounds) 19Ehousing containing large toroids and a 2 unit high, 12Edeep 15 to 20 pounds housing. This is very important when you have to carry around a 19Erack, possibly also containing a preamp, sound/effectsprocessor, BassPod or the likes.)
There have been some threads dealing with smps for class d: in the thread SMPS design for power amps (Class D in particular)E( http://www.diyaudio.com/forums/show...&threadid=41211 ), some very creative and skilled technicians (a.o. Bruno Putzeys, analogspiceman, E) have been discussing SMPS design on a high theoretical level. The real content of their postings was way byond my comprehension, but very interesting at the same time. The thread diedEat the end of november 2004.
In the thread about Icpower modules for PA applications, the issue emerges as well on a somewhat more human level. It seems a very complicated matter, e.g.: because of the limit that the smps design seems to impose on the capacitance of the output caps, the supply is in danger in case power supply pumping occurs. There are some smpss available, though, as many who have been around here may already know. One is the A and T labs smps ( http://www.a-and-t-labs.com/K6_Sw_Amp/index.htm ) of 1000W, designed to power some 2 x 300W or so class A/B amplifier. However, its design stems from 1995 and one may assume that new insights on the issue have evolved since then. Furthermore, it has small output caps and it seems to control only the output voltage rate and not the symmetry, which would make it defenseless against a pumping class D module. (thanks for the explanation, Ghemink, I hope I have understood it well). Other smpss for poweramplifiers are available at http://www.cadaudio.com . They are designed to work well with their own cadaudio modules and with the Icpower ones, which are fullbridged and do not suffer from power supply pumping. Sadly, mainly for this reason they also are not sold seperately.
There MUST be some design possible that would match my (and, again, hopefully others) requirements. This is illustrated, for example, by the fact that Hevos, a Dutch manufacturer of high quality bassgear, will be introducing a bass top this spring that has a tubedriven preamp and a (or more) UCD module(s) from Hypex (not coincidentally the company that Bruno Putzeys works forE), all together in a 2 unit high lightweight 19Ehousing. I mailed them in the hope to get some information about the setup, but understandably they would not go into details, as they told me in their friendly reply.
So, concluding this too long story: that is what its about. A practicalESMPS. I would be happy to see some postings containing info that could help me and possibly others. If not, ok, the thread will sink in the list and dissapear out of sight, big deal. But i think its woth a try. And if, lets try to stick to the topic. I must admit that I myself posted some messages here and there in the past that were more or less off-topic, or not helpful or relevant at all. Im still a little uncertain in my forum-manners (maybe demonstrated by the novel-length of this message..? SorryE
Besides the SMPS, any ideas on preamping the class D amp would also be highly appreciated. But the main issue will stay smps.
Though its high time to end this introduction, still a few words about myself:
I have been playing bass on (semi-) professional level from the late 70s till the early 90s. I played jazz, fusion, rock, blues and aside from that basically anything that would get me some mony, on fretted/unfretted electric bass and upright bass. Sometimes it was good for a living, sometimes not nearly close. I was a studierE practiced a lot and yet did not reach the level I had in mind. On the contrary, eventually I did not know anymore how to play a normal, functional bassline and in 1990 I decided to try and find a decent job, in which I succeeded. Presently, I am a database consultant (like many flipped musicians, philosophers, sociologists, teachers and the likes) and I like what I am doing. Recently, I started playing again, motivated by a small gig I had been asked for and I noticed how much I missed the feeling and how much a musician I am in my heart. I am also less blocked by ambition and I like searching for good basslines now, played with a good sound.
I am, and have always been, a great admiror of the late Jaco Pastorius.
Electronics: I am pretty comfortable as long as Ohms law and some other basic formulas are applicable in simple equations. Byond that, I tend to get heavily lost. My most creative idea so far was a power supply without transformer, i.e. using rectified and buffered mains AC without any galvanic isolation. In Holland, we use 230V rms, which would render some 320V DC on the rail. The Zappulse in my testamp uses +/- 80V (so, 160V). In some kind of symmetrical setup my supply could power 2 modules. After some rethinking I began to suspect that it would probably mean the surest one way ticked to heaven, where I could serve as a human 320V capacitor for Jacos bass rigE
Best regards, Joep |
Hello Joep,
That was a long post, but interesting and quite well summarized. However, never, never try to power your amp directly from the AC mains. You will really electrocute yourself or others. Always use transformers between the mains and the power for the amps. Fortunately, you came to that conclusion yourself, this is really killing.
I think the best way to avoid problems with an SMPS is still to go for a bridged amp. I know, that increases the cost of the project, but you could buy almost two UcD400 modules for that 1 ZAPpulse that you have there. So hardly increased cost and guaranteed no power supply pumping.
I still don`t have my SMPS, it is delayed a bit because of not all components being in stock. After that I still have to build it in the small number of evening hours I have (my day-job takes a lot of my time :-), no I`m not a database consultant, I develop Flash memories)
Anyway, have fun with your project, have fun making music and stay alive and away from the mains without any transformers.
Best regards
Gertjan |
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| analogspiceman |
| quote: | Originally posted by Joep Zonnebloem
As I have understood, switched mode power supplies are much too noisy to be acceptable in a hifi configuration. |
Hi Joep,
A power factor corrected switched mode power supply is almost just like a low performance class d amplifier running in reverse. Kind of like a bad sub amp really - it only needs to poorly produce one low frequency (that of the net at a few percent distortion). That, plus it needs to provide galvanic isolation. If a class d amp can do this quietly while handling the music power peaks, a power supply that can do the same should be only a little bit larger and more expensive the class d amp (because it needs nearly an equivalent amount of stuff plus a high frequency isolation transformer).
There simply has not been a large enough market to support the slightly different, but not more difficult design-wise needs of a SMPS for class d amps. The recent flood of high performance, low cost class d amps will soon change this situation, IMO.
What's different about SMPS for class d?
Like the d amps themselves, SMPS's for class d need a high peak to average capability. IMO, they also should have power factor correction with a lot of energy storage (needed to suppress audio line flicker). And they should be designed for very low common mode output noise. This last performance feature would not be especially difficult to do, but it usually not required by the typical SMPS customer so it is not provided.
Regards -- analogspiceman
PS: The unisolated Euro mains can easily be lethal and is much too dangerous for the average DIYer to be fooling around with. |
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| analogspiceman |
| quote: | Originally posted by analogspiceman
Like the d amps themselves, SMPS's for class d need a high peak to average capability. IMO, they also should have power factor correction with a lot of energy storage (needed to suppress audio line flicker). |
Whoops,:o it's one or the other - there's no need for high peak to average capability in the SMPS if there is enough dc link energy storage to supply the audio peaks to the output (i.e. suppress audio line flicker). |
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| Joep Zonnebloem |
| quote: | Originally posted by ghemink
Hello Joep,
That was a long post, but interesting and quite well summarized. However, never, never try to power your amp directly from the AC mains. You will really electrocute yourself or others. Always use transformers between the mains and the power for the amps. Fortunately, you came to that conclusion yourself, this is really killing.
I think the best way to avoid problems with an SMPS is still to go for a bridged amp. I know, that increases the cost of the project, but you could buy almost two UcD400 modules for that 1 ZAPpulse that you have there. So hardly increased cost and guaranteed no power supply pumping.
I still don`t have my SMPS, it is delayed a bit because of not all components being in stock. After that I still have to build it in the small number of evening hours I have (my day-job takes a lot of my time :-), no I`m not a database consultant, I develop Flash memories)
Anyway, have fun with your project, have fun making music and stay alive and away from the mains without any transformers.
Best regards
Gertjan |
Hi Gertjan,
I already have experienced some interesting phenomena with Mains AC the last few weeks, like 4 resistors expelling very rapidly 4 very neat and identical little feathers of smoke, in a split second, completely synchronously. That was a fascinating sight. On another occasion I found, also in a split second, one pen of my multimeter welded to a copperwire after a very loud pang that made my ears hiss for some time. You can imagine I have gotten a little (lot) more cautious now.. Thanks for the concern, anyway :)
As for the power supply pumping: how bad will it be? Who has some experience with this? I dont read a lot on it, apart from the theoretical possibility. I have not been able yet to test my amp at its full power. I could try it in my living room, but, depending on the mood my neighbour is in, the effect on my health could eventually be as disastrous as fooling around with AC mains carelessly :) . So I bought 5 100W lightbulbs with fittings and I am going to connect them in parallel and then the lot in series with a little 8 Ohm speaker (to give me some acoustic feedback) to my output and then try to apply maximum power (in steps, using a regulator) I realize its not a perfect dummyload, but it may serve my purpose, i.e. investigating the tendency to power supply pumping with a +/- 80V supply at full power in 4 Ohms. I will report here on this little test.
Success in assembling the PS! Im very curious for the eventual result.
Best regards, Joep
| quote: | Originally posted by analogspiceman
There simply has not been a large enough market to support the slightly different, but not more difficult design-wise needs of a SMPS for class d amps. The recent flood of high performance, low cost class d amps will soon change this situation, IMO.
What's different about SMPS for class d?
Like the d amps themselves, SMPS's for class d need a high peak to average capability. IMO, they also should have power factor correction with a lot of energy storage (needed to suppress audio line flicker). And they should be designed for very low common mode output noise. This last performance feature would not be especially difficult to do, but it usually not required by the typical SMPS customer so it is not provided.
Regards -- analogspiceman
PS: The unisolated Euro mains can easily be lethal and is much too dangerous for the average DIYer to be fooling around with. |
Hi analogspiceman,
I feel honoured by your posting. As I said earlier, I have been reading your discussions with a.o. Bruno and admire the ease with which you people are able to understand and analyse these complex matters. Its encouraging to read your comment about the expected availability of suitable SMPS in the future.
Do you mean with high peak to average capability that the supply should be able to deliver high peaks, above its normal operational current? And with a lot of energy storage (needed to suppress audio line flicker) that it should have large caps on the output to flatten the switching noise? Then Im starting to get the picture. Sorry for my ignorance, Im still learning
As for the AC mains adventures, see my reply to Ghemink above. In the mean time I have learned to always check and double check whether the apparatus is disconnected from the mains and will always discharge the caps with a lightbulb before touching anything. My proposed powersupply was only mentioned to illustrate my even greater ignorance some time ago
Best regards, Joep
PS, of course I read your correction on the peak to average capability... |
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| Joep Zonnebloem |
| quote: | Originally posted by Joep Zonnebloem
....... So I bought 5 100W lightbulbs with fittings and I am going to connect them in parallel and then the lot in series with a little 8 Ohm speaker (to give me some acoustic feedback) to my output and then try to apply maximum power (in steps, using a regulator) ......
|
Hm... On second thought I'd better give this concept some more thought.... It may kill my little testspeaker
@Analogspiceman: Are you still developping (theoretically or practically) any SMPS for audio, like you did with Bruno at the time? In that case, do you already have some sort of design that could be tested? I would be very happy to do that! (being VERY carefull on the mains, of course ;) )
Best regards, Joep |
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| Yves Smolders |
Joep,
You think your test-setup is ugly?
Behold my test setup... My girlfriend is lovingly reffering to it as "Het Gedrocht" :D
Essentially it's a hacked old integrated amp. Just need to put the speaker terminals on the back plate so I can close it up. All electronics in the amp are disconnected, and can be repaired when I move to the real project (budget, budget...)
Yes, the top lid of the icecream box is on the part list... :angel: |
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| Yves Smolders |
And finally...
It looks worse on photo than real life... really... I'm serious :D |
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| Joep Zonnebloem |
| quote: | Originally posted by Yves Smolders
Joep,
You think your test-setup is ugly?
Behold my test setup... My girlfriend is lovingly reffering to it as "Het Gedrocht" :D
...........................
|
Well, at least it looks like an amplifier and not like a containership :)
It's pretty crowded in that box... |
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| ghemink |
| quote: | Originally posted by Joep Zonnebloem
Hm... On second thought I'd better give this concept some more thought.... It may kill my little testspeaker
@Analogspiceman: Are you still developping (theoretically or practically) any SMPS for audio, like you did with Bruno at the time? In that case, do you already have some sort of design that could be tested? I would be very happy to do that! (being VERY carefull on the mains, of course ;) )
Best regards, Joep |
Hello Joep,
You should put the 8Ohm speaker in parallel with the lightbulbs and connect a resistance in series with the little speaker if you want to protect it. |
|
|
| ghemink |
| quote: | Originally posted by Joep Zonnebloem
Hi Gertjan,
I already have experienced some interesting phenomena with Mains AC the last few weeks, like 4 resistors expelling very rapidly 4 very neat and identical little feathers of smoke, in a split second, completely synchronously. That was a fascinating sight. On another occasion I found, also in a split second, one pen of my multimeter welded to a copperwire after a very loud pangEthat made my ears hiss for some time. You can imagine I have gotten a little (lot) more cautious now.. Thanks for the concern, anyway :)
As for the power supply pumping: how bad will it be? Who has some experience with this? I dont read a lot on it, apart from the theoretical possibility. I have not been able yet to test my amp at its full power. I could try it in my living room, but, depending on the mood my neighbour is in, the effect on my health could eventually be as disastrous as fooling around with AC mains carelessly :) . So I bought 5 100W lightbulbs with fittings and I am going to connect them in parallel and then the lot in series with a little 8 Ohm speaker (to give me some acoustic feedback) to my output and then try to apply maximum power (in steps, using a regulator) I realize its not a perfect dummyload, but it may serve my purpose, i.e. investigating the tendency to power supply pumping with a +/- 80V supply at full power in 4 Ohms. I will report here on this little test.
Success in assembling the PS! Im very curious for the eventual result.
Best regards, Joep
Hi analogspiceman,
I feel honoured by your posting. As I said earlier, I have been reading your discussions with a.o. Bruno and admire the ease with which you people are able to understand and analyse these complex matters. Its encouraging to read your comment about the expected availability of suitable SMPS in the future.
Do you mean with high peak to average capabilityEthat the supply should be able to deliver high peaks, above its normal operational current? And with a lot of energy storage (needed to suppress audio line flicker)Ethat it should have large caps on the output to flatten the switching noise? Then Im starting to get the picture. Sorry for my ignorance, Im still learningE
As for the AC mains adventures, see my reply to Ghemink above. In the mean time I have learned to always check and double check whether the apparatus is disconnected from the mains and will always discharge the caps with a lightbulb before touching anything. My proposed powersupply was only mentioned to illustrate my even greater ignorance some time agoE
Best regards, Joep
PS, of course I read your correction on the peak to average capability... |
So powersupply pumping would be worst at low frequencies and impedances. So a 20Hz signal at high power maybe the worst test signal.
I have done some simulations to see what happens, forgot about the results, but you can see it clearly happen at 20Hz depending on capacitor size.
Gertjan |
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| Joep Zonnebloem |
| quote: | Originally posted by ghemink
Hello Joep,
You should put the 8Ohm speaker in parallel with the lightbulbs and connect a resistance in series with the little speaker if you want to protect it. |
Hi GertJan,
That's what I had figured out in the meantime... Only, to simulate a load of say 600W, I need a lot of bulbs. One 100W bulb has a resistance of around 50 Ohm, so I would need some 12 bulbs in parallel to reach around 4 ohms. And their resistance might vary with their temperature. I am now looking for an alternative. There is a circuit on the Dutch site circuitsonline.net ( http://www.circuitsonline.net/circuits/view/90 ) for a dummyload up to 100W that would simulate speaker behaviour. Maybe you understand some Dutch (your name points in that direction :) ), so maybe you could take a look. But for 600W. IMO it would need modifying the value of R1 (with multiple resistors in parallel, I guess) which would make it not particularly cheap... Aside from that, I cannot tell whether this modification would influence the speaker-like behaviour of the circuit. If so, it would be a waste to go that way, because I am not capable (yet) of redesigning the whole thing with inductances etc.
I am now wandering around my house with my multimeter trying to find some domestic gear ( irons, percolators, heaters ...) whith the right impedance and sufficient power consumption. Any suggestions maybe?
| quote: |
..............
So powersupply pumping would be worst at low frequencies and impedances. So a 20Hz signal at high power maybe the worst test signal.
|
The lowest note (low E) on a regular bass is around 43 HZ. A fivestring bass (which I own but practically never use) has a low B of 31 HZ. Maybe, when you play massive chords (which I rarely do), "difference-ferquencies" (I don't know if this is the correct English word for it) could amount to significantly lower values, but then I doubt if they would be very prominent. ( EDIT Correction! They can be, if all strings are strummed together in some cases) I would think 20HZ is a typically (home-)theater surround sound frequency. So anyway, i think it's worth to try testing it.
Thanks for the input! Regards, Joep |
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| ghemink |
| quote: | Originally posted by Joep Zonnebloem
Hi GertJan,
That's what I had figured out in the meantime... Only, to simulate a load of say 600W, I need a lot of bulbs. One 100W bulb has a resistance of around 50 Ohm, so I would need some 12 bulbs in parallel to reach around 4 ohms. And their resistance might vary with their temperature. I am now looking for an alternative. There is a circuit on the Dutch site circuitsonline.net ( http://www.circuitsonline.net/circuits/view/90 ) for a dummyload up to 100W that would simulate speaker behaviour. Maybe you understand some Dutch (your name points in that direction :) ), so maybe you could take a look. But for 600W. IMO it would need modifying the value of R1 (with multiple resistors in parallel, I guess) which would make it not particularly cheap... Aside from that, I cannot tell whether this modification would influence the speaker-like behaviour of the circuit. If so, it would be a waste to go that way, because I am not capable (yet) of redesigning the whole thing with inductances etc.
I am now wandering around my house with my multimeter trying to find some domestic gear ( irons, percolators, heaters ...) whith the right impedance and sufficient power consumption. Any suggestions maybe?
The lowest note (low E) on a regular bass is around 43 HZ. A fivestring bass (which I own but practically never use) has a low B of 31 HZ. Maybe, when you play massive chords (which I rarely do), "difference-ferquencies" (I don't know if this is the correct English word for it) could amount to significantly lower values, but then I doubt if they would be very prominent. ( EDIT Correction! They can be, if all strings are strummed together in some cases) I would think 20HZ is a typically (home-)theater surround sound frequency. So anyway, i think it's worth to try testing it.
Thanks for the input! Regards, Joep |
Yes, I'm from Holland, just happen to live and work in Japan. Dus we kunnen gewoon in het NLs mailen.
Those light bulbs seem to be quite interesting loads to me. They are cheap, give visual feedback and you can put any number in parallel to get any load that you want. Plan to use them for power supply testing as well. I have made some dummy loads with resistors, but you need many resistors to share the power, I will try lamps. I would not bother too much to try to simulate a load that resembles a speaker, every speaker is different anyway.
Groeten
Gertjan |
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| Joep Zonnebloem |
| quote: | Originally posted by ghemink
Yes, I'm from Holland, just happen to live and work in Japan. Dus we kunnen gewoon in het NLs mailen.
Those light bulbs seem to be quite interesting loads to me. They are cheap, give visual feedback and you can put any number in parallel to get any load that you want. Plan to use them for power supply testing as well. I have made some dummy loads with resistors, but you need many resistors to share the power, I will try lamps. I would not bother too much to try to simulate a load that resembles a speaker, every speaker is different anyway.
Groeten
Gertjan |
I think I'll go for the bulbs and save on the costs by soldering them without fittings. Thanks, fellow Dutchman, long way from home :)
Regards, Joep |
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| Joep Zonnebloem |
| BTW, what will happen if you connect the SMPS to some really big capacitors? Wouldn't there be some way to do that? Would that be harmfull to the supply in case of large loadpeaks or something? |
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| destroyer X |
Including the Ice cream you told...i think things is running hundred percent.
Go ahead, do not let thread die.
Carlos |
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| ghemink |
| quote: | Originally posted by destroyer X
Including the Ice cream you told...i think things is running hundred percent.
Go ahead, do not let thread die.
Carlos |
I'm still waiting for the SMPS kits to arrive, will reply when I have them working, have also ordered some UcD400 modules to try out with that SMPS.
Gertjan |
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| ilimzn |
It may be worth Googling up the Sony TA-N88(B) power amp.
This is perhaps the grand-daddy of all decent class D amps, at 170WPC and 0.1% distortion.
It uses a SMPS for power.
And, it was first demoed in 1977, production started in 1978.
It uses VFETs in the output stage (2 P-N pairs per channel). These are NOT MOSFETs but power JFETs (therefore depletion devices), 200V/10A, VERY fast with only about 180pF gate capacitance, but they need about -50V to turn them off.
It is also a fully discrete design except for a high gain chip amp speciffically made for it wired as a 'compare with zero' comparator (today this could easily be replaced by a half-decent current feedback opamp or even one of the new ultrafast voltage feedback amps, or a fast comparator).
Interestingly, it uses a 4th order output filter, with air cored inductors.
I have the amp, and it's schematic - learned lots from it. |
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| wrenchone |
The real great-grandaddy of switching power amps was the Infinity power amp circa 1974. It was supposedly rated at 250W per channel, and used Solitron milspec bipolar output devices. It also used a switching power supply, which was its downfall. There was not enough capacitance on the output, so the amp had serious problems with pumping for sustained high power bass tones. This is the beast that got me interested in switching power supplies and amplifiers.
It would be a good idea to use simple iron in the power supply at first to get all the amplifier issues ironed out. Trying to develop both a switching amp and power supply at the same go is rather a large plate full. Also, disasters involving mains operated switching supplies tend to be pretty destructive, especially when there is a PFC involved, not to mention the safety issues. You will need to pay a lot of attention to EMI control, unless you want to be carrying around a broadband RF noise generator masquerading as a power amplifer.
The big problem with using a switching power supply to power an audio amp is the large dynamic range of the load current. Switching power supplies like to see a fairly steady load, and can lose regulation at light load unless you know the tricks to get around those problems. Also, switching power supplies will generally have a fairly limited bandwidth and can have trouble slewing fast enough to follow sudden load changes. Unless you have special equipment, it will be difficult to even measure the loop bandwidth and phase margin for a switcher.
The best approach may be an open loop type power supply that programs the duty cycle as a function of the input voltage. This will get you approximately the right output voltage and also enable ripple cancellation to get rid of the mains frequency ripple introduced by the PFC. Loop stability will not be an issue. Since you will be using large output capacitance to get around the bass pumping problem, you will have a fairly large energy reservoir on the output to take care of load transients. Use of swinging chokes in the output filters will allow one to regulate at low output current. What you would essentially have is a high frequency equivalent to a big chunk of iron. One more thing - if you are serious about developing a switching power supply, get your hands on a current probe. Otherwise, you'll be completely blind to a lot of the problems that can crop up.
There are successul professional amplifier designs out in the field that have solved the problems involved with using switching power supplies. QSC uses a switching power supply for their new professional power amplifiers. |
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| ghemink |
| quote: | Originally posted by Joep Zonnebloem
BTW, what will happen if you connect the SMPS to some really big capacitors? Wouldn't there be some way to do that? Would that be harmfull to the supply in case of large loadpeaks or something? |
Depending on the feedback network, the amp could become unstable. I will do measurements on the SMPS and may change the feedback network so that it can live with bigger caps (if it would be an issue for stability) or I may even try to add current feedback.
Will be an interesting project. Have to refresh my theory on feedback/stability etc from university age.
Gertjan |
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| Joep Zonnebloem |
| quote: | Originally posted by wrenchone
It would be a good idea to use simple iron in the power supply at first to get all the amplifier issues ironed out
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This is excactly my intention. As far as power and stabilty are concerned, the linear power supply I use now (big toroid, monster capacitors) should be an absolute reference.
| quote: | Originally posted by wrenchone
What you would essentially have is a high frequency equivalent to a big chunk of iron.
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...And that is precisely what I would be looking for...| quote: | Originally posted by wrenchone
There are successul professional amplifier designs out in the field that have solved the problems involved with using switching power supplies.
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... Which is very encouraging indeed. It may be only a matter of time before high quality, reliable designs become available to the average diy'er.
As for the approach you propose: I think I get a basic outline picture of it. However, me being the audacious starter of this topic, you should know that, though I am determined to reach a knowledge level that will enable me to deal whith the issues involved effortlessly, my current theoretical knowledge is still not quite built up and it is very fragmentarily; to tell you the truth, at the moment I am still trying to understand the various behaviours of components in general circuits. To that end, I have studied sites like http://home.planet.nl/~heuve345/ele...rse/course.html and http://www.electronics-tutorials.com/ , but without any real technical background (just highschool physics and maths, a long time ago. And maybe even age has something to do with it :) ), I may understand the formula's and principles, but still find it hard to visualize and "internalize" them and be able to combine them creatively. I just bought some equipment, like a simple and old, but good oscilloscope (Philips PM3200, 15 Euro on an auction site!), a breadboard, assorted components etc. and built a simple regulated supply on a PCB (linear of course...) to power the board, to get some feeling for the electronical reality: maybe experimenting will increase my insight. My goal is not to design a suitable SMPS in time (though it is a very appealing daydream...), but to be able to make good choices for my amplification. And also, not in the least, because I find electronics more and more fascinating. And I discovered I just like fooling around with the soldering pen, etching PCB's etc.
I will start with building a "Roman Black" supply: http://www.romanblack.com/smps.htm . I have the feeling this is a clever guy who is, in his way, more or less trying to get to the essence of matters. I think playing a little whith his design could be good for the intuition. I have problems, though, finding suitable inductors at my local electronics store.
When I'm a little more at ease with the concepts, I plan to thouroughly study this: http://www-s.ti.com/sc/psheets/slup169/slup169.pdf , which I think seems a good introduction on high speed switching mosfet circuits.
You see, I have a long way to go and, at this point, I would not dare to try and say anything sensible about different approaches. Your ideas, however, superficially sound excactly right to me. It should be a very stable, indisturbable audio PSU whith the qualities of a 40 pounds linear supply. I don't think it has to be as lightweight as possible, nor should it be miniaturized to all extend. It should be just reasonably light and just reasonably small. I have understood that a lot of problems in stable SMPS design result directly from the high switching frequency, biassing etc. I don't know whether it makes any sense, but the possibility has come into my mind of an SMPS design with a relatively low, forced switching frequency of, say, 1KHz, enabling it to inherit some of simplicity and stability from a linear PSU design, using a transformer that would be larger than common SMPS transformers, but still small enough to be acceptable and at the same time enabling it to use large output capacitors. It does not even have to meet the efficiency standards of the state of the art-SMPS's either. But maybe I'm talking nonsense...
Joep |
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| Giaime |
Hello there! I'm also thinking of making a bass amp for a friend of mine with the Ucd400.
I have a few questions:
- How big should be the trasformer? 500VA? I'm planning on 35V secondaries...
- What psu capacitor value? 2x6800? or more?
- Should I bypass the rectifier module with caps (0.1uF 100V) to reduce noise? If yes, should I connect 2 of them from the AC in pins to the minus output pin?
- Should I use some kind of soft start circuit? I would like to avoid it...
- Any thoughts of getting the Ucd here in Italy? I found them at
http://www.audiokit.it/ITAENG/KitEl.../HypexProfi.htm
but it seems to be not so cheap... what about ordering them directly from the factory? Would the shipping cost be big?
And... are you using a preamp before the module? I bet you're using some not-diy one... maybe a basspod... I was planning to build an extremely simple pre on perfboard, just to use it without a pre, and put a "pwr amp in" to use with a dedicated pre...
Thanks in advance! |
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| destroyer X |
And studying this interesting subject.
You welcome ....this is our home, just another room.
regards,
Ciao
Carlo di Danesi |
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| Giaime |
Hello Carlos, glad to see you here too!
Thanks for the welcomes, I appreciate them much.
What about my questions? :D |
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| pburke |
| quote: | Originally posted by Yves Smolders
Joep,
You think your test-setup is ugly?
Behold my test setup... My girlfriend is lovingly reffering to it as "Het Gedrocht" :D
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can't be that ugly - you still HAVE a girl friend
;) |
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| ghemink |
| quote: | Originally posted by pburke
can't be that ugly - you still HAVE a girl friend
;) |
I moved all my experimental speakers and amps to my "home office", that room is smaller but it keeps my wife happy:-)
And actually the acoustics are pretty good, smaller room but better damped.
Best regards
Gertjan |
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| Giaime |
| Nobody Helps Me? :whazzat: :smash: |
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| phase_accurate |
PSU facts are dealt with within the UcD 400 thread. Also questions answered.
Jan-Peter of Hypex will be pleased to answer questions about direct delivery to Italy (and the cost generated) I assume.
Regards
Charles |
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