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Old 20th June 2009, 08:00 PM   #1
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Default Output regulator after torodial transformer?

Hi there, i am currently working on an amp project using the nx150-2 modules from class-d.com and got a little lost in the powering stuff. I read that its best to put some elkos after the volt outpot of the transformer but i found no good circuits - has anybody a hint about a good circuit that gives me high qulity dc? Or is it even necessary? (sorry for the bad english - technical things are heard for me as native german speaking guy

any hints and expirience welcome!
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Old 20th June 2009, 09:47 PM   #2
Minion is offline Minion  Canada
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well you are going to need more than caps after the transformer to make a proper well filtered DC power supply ....

The transformer puts out AC , so you are going to need a Diode Bridge rectifier to make that DC ,
the DC after the bridge rectifier will have a Lot of what is called "Ripple" it sort of means that the DC will pulsate and won"t be steady , to solve that they put large Capacitors after the Rectifier from the power rails to ground , these store a charge so that the DC is more steady and has less ripple .....

Yours modules need a dual rail PSU of about +/-50V DC .....

Here is a DC Power supply project and schematic ...

http://sound.westhost.com/project04.htm


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Old 21st June 2009, 11:11 AM   #3
AndrewT is offline AndrewT  Scotland
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do not fit a regulator between the PSU (power supply unit consisting of transformer+rectifier+smoothing capacitors) and the power amplifier.
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Old 21st June 2009, 11:33 AM   #4
SY is offline SY  United States
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I moved this thread to Power Supply Design.
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Old 24th June 2009, 10:50 PM   #5
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thanks for the link - that looks interesting. Another general question (sorry, got no clear answer out of the search) - do i need stabilized power for a class a/b amp? And are there any other circuites or modules flying around that give me high quality and 50v out of the box? that whole powering stuff seems even more complicated than the amps themself!
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Old 24th June 2009, 11:12 PM   #6
Minion is offline Minion  Canada
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Generally you don"t need a regulated PSU for a Power amp ....

What you need is a Power transformer of a Voltage that when rectified into DC is close to +/-50v ...I"d say a center Tapped 35v,0v,35v 360Va Power transformer Per channel , Then you would need a Bridge rectifier to convert DC , I suggest a 20A bridge , you are then going to need some power supply capacitors , I would say 4 10,000uF 63V capacitors , 2 per power supply rail ......

You might be better off looking for a Power supply kit like this :

http://chipamp.com/supply.shtml

But with Higher Voltage Capacitors ....
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Old 25th June 2009, 04:24 AM   #7
star882 is offline star882  United States
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Regulated supplies will improve the performance, but are not strictly required. They can allow for "dynamic supply voltage" that increases efficiency at low volumes.
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Old 25th June 2009, 10:03 AM   #8
AndrewT is offline AndrewT  Scotland
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Hi,
regulated supplies may improve the performance.
Regulated supplies combined with a power amplifier require more design skill and debugging skill than a power amplifier alone from a conventional PSU.
If there is an interaction between the active PSU and the active P amp then any tendency towards instability may be exacerbated.
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Old 25th June 2009, 10:53 AM   #9
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That power supply from chipaudio.com looks really interesting - it has a blue led and a reasonable price! - can someone point me in the right direction what i should change exactly here for 50v outputs (i guess just bigger caps right - somethin else?).

Also the stabilized power thing still bugs me - i often read that unstabilized power is more "natural" for amp demands in general (more power at peak times), on the other hand you say that its good for low volumes that i will often listen to - do you think i should try it with stabilized power? Would it be simple to stabilize the kit from chipaudio and how?

Darn - so many questions! Btw - does anybody know a book or something on electronics especially with diy hifi in mind?
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Old 25th June 2009, 01:46 PM   #10
star882 is offline star882  United States
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Yes, designing a good regulated power supply is not exactly an easy task. However, it is better since it greatly reduces supply voltage variations. And in practice, instability is not an issue with sufficient filtering.
Here's an example of an amplifier (very efficient hybrid digital) with a regulated power supply:
http://ecorenovator.org/forum/applia...ome-audio.html

If you look carefully, you'll notice a 5uH inductor and 4700uF capacitor acting as a filter. At each amplifier chipset, further filtering is provided by 10uF film capacitors, 220uF electrolytics, and 1uF tantalums. (Also note that the power feed for the power stages and the modulators are separate.) The two channels are not synchronized with each other or the power supply but no detectable interference is noted. (That amplifier was presented at a university engineering show and I was impressed to say the least.)

Note that while modern hybrid digitals and pure digitals do not gain much efficiency from dynamic supply voltage, some pure digitals (most notably TI PurePath) use dynamic supply voltage to maintain high resolution at all volumes.
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