Power Supply Design - Off My Rocker? - Page 5 - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 1st January 2005, 08:02 PM   #41
diyAudio Member
 
Join Date: Aug 2004
Location: IL
So, my next question is should I just start experimenting with low level switching power supplies?

Reece
  Reply With Quote
Old 1st January 2005, 08:07 PM   #42
diyAudio Member
 
Join Date: Aug 2004
Location: IL
By the way, Happy New Years to all!

Reece
  Reply With Quote
Old 3rd January 2005, 12:23 AM   #43
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: USA
> should I just start experimenting with low level switching power supplies?

No.

If "Class A is like driving with the parking brake on", then switch-mode supplies are like doing watch-repair on a vibrating bed.

Switch-mode supplies are now common, almost mandatory, in VERY high power commercial sound. When you want a dozen 2 KW amps in a 48" road-rack, the weight savings pay for the much more complicated design. But gold-ear tests usually favor the meaty sound of conventional amps. Absent a compelling weight issue, and a clear path to a low-price low-ripple design, I would not go there.

Ordinary SMPS design won't work for Class-B audio. A common SMPS has a minimum output current: it can't drive its effective impedance high enough to control very small current. They can be pretty good: many PC power supplies can idle with just the load of their internal DC fan. But it is a design problem, and one not covered in cookbook design tools.

Watch surplus sales. Monster caps sometimes turn up at attractive prices.

If power noise-ripple is really a problem, go to a 2-stage filter. Once you get past the bare-minimum capacitance (say 1000uFd), even a very lame 2-stage gives better ripple rejection and much better rejection of ripple harmonics, with little effect on speech/music power.

Happy 2005!
  Reply With Quote
Old 3rd January 2005, 02:57 AM   #44
diyAudio Member
 
Join Date: Aug 2004
Location: Great White North, eh?
Send a message via ICQ to SupraGuy Send a message via Yahoo to SupraGuy
With all due respect...

While the information that I've garnered about SMPS does indicate that it's not something to be undertaken lightly by the average DIYer, for high power applications, it seems to be the only way to fly.

Weight and size issues aside, the general efficiency of a SMPS is hard to beat. As to minimum current issues, with most of the amplifiers that I've seen there is signifigant bias current, which will definitely require enough current to keep a SMPS stable.

For the "golden eared" -- I don't believe everything that they say. As far as I'm concerned, the power supply shouldn't provide anything to the amplifier's sound. If it does, it's defective and needs to be improved, or replaced with something that doesn't.
__________________
There are 10 types of people in the world. Those who understand binary, and those who don't.
  Reply With Quote
Old 3rd January 2005, 01:00 PM   #45
diyAudio Member
 
jackinnj's Avatar
 
Join Date: Apr 2002
Location: Llanddewi Brefi, NJ
Quote:
Originally posted by PRR
> should I just start experimenting with low level switching power supplies?

Ordinary SMPS design won't work for Class-B audio. A common SMPS has a minimum output current: it can't drive its effective impedance high enough to control very small current. They can be pretty good: many PC power supplies can idle with just the load of their internal DC fan. But it is a design problem, and one not covered in cookbook design tools.

If power noise-ripple is really a problem, go to a 2-stage filter. Once you get past the bare-minimum capacitance (say 1000uFd), even a very lame 2-stage gives better ripple rejection and much better rejection of ripple harmonics, with little effect on speech/music power.

Happy 2005!
A switched mode PS, if the output inductor is large enough, can tolerate a fairly low load -- it's all a matter of working the equations and then dealing with the cost and size of the inductor. To this end the DIYr should design the supply so that it burns some watts constantly -- the QEX article on a modded ATX supply would run 100ma min, 20 amps max -- and the output inductors were designed for this.

The other big problem I see for DIY SMPS design are the EMI or RFI problems --

Again, I suggest that DIYrs search on the Nat Semi website and search under Sanjaya Maniktala's name for articles on optimizing the magnetics in SMPS.
  Reply With Quote
Old 5th January 2005, 09:52 PM   #46
hermanv is offline hermanv  United States
diyAudio Member
 
Join Date: Apr 2004
Location: Northern California
An interesting series of posts and opinions.

The difference between a good power amp and a great power amp is in the details. Good power amps are availlable in the comercial market place for less money than the parts will cost you to build your own, so unless you just want experience or knowledge, why build just another good power amp. Just buy one.

Great power amps from commercial sources cost way more because they are built in low volumes and use more expensive parts (such as oversize filter capacitors even going so far as non-electrolytic capcitors for main storage) They may use a separate chassis for power they often use more regulation or choke input filters, they might be fully balanced end to end effectively doubling the number of parts, the list just goes on and on. They use a host of ideas to make little improvements that are all well down the diminishing returns curve and well up the increasing price and complexity curve.

Yes the basic schematic of an average power amp is not that big a deal but I believe you should be wary of people who tell you this is all simple and why bother with that complicated stuff. The complicated stuff is what makes the design special instead of ordinary. Like I said you can buy ordinary for not much money it will probably look pretty and be quite reliable and work fine. It just wont be a great power amp.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Power Supply Design Defbrett Tubes / Valves 28 10th October 2009 12:54 AM
I would like to design a power supply Kramerguy Power Supplies 9 14th January 2009 06:50 PM
48 VDC/10 A power supply looking for an Amp design Analog Addict Solid State 16 16th January 2008 11:39 AM
need help with a power supply design lochness Power Supplies 1 31st October 2007 06:12 PM
Power supply design LeakSt20 Parts 0 16th August 2005 04:06 PM


New To Site? Need Help?

All times are GMT. The time now is 09:29 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2