Joep Zonnebloem said:
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
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.wrenchone said:
...And that is precisely what I would be looking for...wrenchone said:
... 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.wrenchone said:
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/electronics/course/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
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/KitElettr/Hypex/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!
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/KitElettr/Hypex/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!
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.