Power supply
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Watchdog

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How does a regulated power supply differ from your average wall wart?

I realize that with a wall wart the voltage can fluctuate significantly and there are also issues with power not being clean either, especially if you live somewhere like New York or California in the last couple of years with brown outs and rolling blackouts.

How does a regulated power supply work and how does it provide a more stable/better source of power?

Is it worthwhile to build a home version of the META42 and then build a regulated power supply to go with it? I realize this is question can really be a matter of personal opinion and that I will likely get some people saying yes and some no, but I'm more interested in the number of yes and no and the reasons why.

I already have an older version of the Little from Headroom and I'm kind of curious as to how much better the META 42 is.

I built both an amplifier and equalizer from scratch in high school electronics so given that circuit boards are available to be purchased as well as a parts list supplied, etc.... I think I can build the META with a little patience.
 
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jasong

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Watchdog

Some wall warts are more average than others. For instance, the Radio Shack 15-30 volt supply that Tangent mentions on his Meta42 site has fairly good regulation and half decent filtering for around $25. You can spend a lot more money on a better PS kit various places on the web, and you can duplicate the designs easily (Wellbourne labs publishes the schematic and board layout and parts list for it's PS-1, for instance), but cost starts to figure in.

I guess I am saying there are options in between a cheap, cruddy wall wart and the full-on Didden/Jung regulator I lust for.

And I can heartily recommend the Meta42 as good project, with great support not only from Warren, but also on the forums.

Jason
 
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tangent

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Quote:

How does a regulated power supply differ from your average wall wart?


I've answered that question (and a few you didn't ask) here: http://tangentsoft.net/audio/opamp-ps.html

Quote:

Is it worthwhile to build a home version of the META42 and then build a regulated power supply to go with it?


Personally, I've only used off-the-shelf supplies. If you want to build a power supply, though, go for it!

I should point out that power quality does matter with the META42. If you have a significant amount of noise on the power rails, it can couple into the amp's output in audible amounts. If your wall-powered META42 has noise that goes away when you use a battery for power, your wall power supply may have too much noise. (I say "may" because there are other things that could be going on if noise goes away when you change to battery power.)
 
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Watchdog

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I think I will go with off the shelf supplies then.

Tangent thanks for the info, it was really useful. I read the article on power and your reference to batteries. Since batteries start out as DC power, does that solve some of our problems with ripple? There's no need for the bridge rectifier with DC, correct?

I recall back in the 80's Mission made an amplifier that used a rechargeable battery and you UNPLUGGED it when you wanted to listen to music. I suppose that reduced the noise? When you were done, then you plugged it back in to recharge the battery.

I'm guessing that power supplies are good enough now to make that kind of system not worth the effort?

I also recall a Linn Audio rep talking about their power amps and how they were really efficient. I think they use switching power supplies and I was amazed at how much power they could put out for their size.
 
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PinkFloyd

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I am using the standard 12V AC 500ma "wallwart" that came supplied with the musical fidelity X- Can V2.

I have heard great reports about the MF X-PSU but can't manage to source one in the UK at the present time.

The UK specifications of the X-PSU are:

Input: AC 230V 50hz
Output: AC 12V 20 VA

Now here is my question:

I have a Toroidal Transformer rated at the following:

Input: AC 230V 50hZ
Output: AC 12V 50 VA

Its "VA" is 50VA compared to the X-PSU's 20VA which shouldn't prove to be a problem or should it??

There is no need for a rectifier or capacitors as the power supply is AC to AC and therefore doesn't need these components to convert to DC.

So... taking all this into consideration will it just be a case of me connecting the toroidals inputs to the mains and running a connector to the X-Can from the toroidals 12v output ?

I will probably be connecting an off off switch to the power supply and maybe an LED that will light when the power is on.

Is there anything "obvious" that I have missed out here and are there any other components I should be configuring into the Toroidal?

My only slight concern was the higher VA rating of my transformer (compared to the X-PSU) but surely it's better having "too much" current on tap rather than not enough?

Your comments will be very much appreciated.
 
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tangent

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A perfect power supply is called a "voltage source", meaning that it puts out a particular voltage level no matter what the load is. Naturally, there is no such thing as a perfect voltage source, but batteries come fairly close.

If the load is high (50 mA or more, for your average alkaline), batteries can do various bad things, which get worse as the load goes up. At the extreme, an alkaline battery will heat up, drop in voltage, and may eventually start leaking.

The average META42 draws only 20-30 mA; I've hit 50 mA before, but only with hungry op-amps and stacked EL2002s. So, batteries are quite close to ideal as far as META42s go. The only thing keeping a battery from being an ideal voltage source at low current levels is that it has a nonzero output impedance, which means that changing current demands will cause its voltage level to fluctuate. Thus, you can still get ripple from a battery, but it's induced ripple based on the music, which isn't as bad a problem as wall power supply ripple. Filtering this induced ripple out is one of the jobs the C2-C4 capacitors perform.
 
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PinkFloyd

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If anyone can help it would be appreciated.

I am going to build a 240 V AC - 12V AC power supply using a toroidal transformer. Would it be beneficial to use a IEC 950 compliant fused inlet filter??

If so, given the explanation below, which would be the best Amp rating to use.. the toroidal outputs 12v 50VA:

A range of fused IEC inlet filters which offer good performance for both common mode and differential mode interference. Available in ywo current ratings 2 Amps and 4 Amps. All filters meet the overvoltage category II of IEC 664 and comply with IEC 950. Typical applications include digital equipment, measuring instruments, monitors and display units. UL, CSA and TUV approved.
Code Type
UT92 Fused IEC filter 2 amp
UT93 Fused IEC filter 4 amp




These prices are only a guide. For the latest prices and live stock availability please click buy button.
Code Description 1+ Price Inc VAT 1+ Ex VAT 10+ Ex VAT 25+ Ex VAT 50+ Ex VAT 100+ Ex VAT
UT92A IEC Fused Filter 2A special offer £2.99
UT93B IEC Fused Filter 4A special offer £2.99
UT94C IEC Fused Filter 6A Discontinued

I look forward to your comments

Cheers

Pinkie
 
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I'm intending to build a dual voltage power supply unit (yes, all the way from mains to +/- 16v) for my new souped up Proto42. Will be throwing in EL2009's next month.

Now, I need to check on one thing. I can't get hold of Linear Tech. chips in Singapore so my only options are National Semiconductor stuff (even then, not all models are available).

Considering that the EL2009's can go up to 1A each;
Do I need voltage regulators that will churn out more than 1.5A?
(Thus eradicating LM317/337 & 117/137 combi's)

This is sort of an overkill but it should be better than TLE2426 or resistor divider ladders w/ buffers since it won't get unbalanced.

The next question is:
Should I use this design:
http://sound.westhost.com/project44.htm

or should I use the Welbourne Labs PS-1 design?

The difference being that the Welbourne labs design uses 2 Bridge rectifiers and many more caps.
 
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The ESP and Welborne Labs designs are basically the same, though the Welborne Labs is more "tweaked out."
 
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The PS-1 uses more caps to reduce PS ripple (noise). I like that! I also like the use of bridge rectifiers. So I would go with the PS-1. It seems to be a better design. However, I just did a quick study of the Australian PS.

You should be able to get all the components you need for the PS-1 at Sim Lim Square in Singapore. And with some expert advice, you may be able to add capacitance to the PS-1 to make it a better PS!
 
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Dreamslacker,

Replacing the bridge diodes with schottky's would improve the supply.
 
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DeeJayBump

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Quote:

Originally posted by Watchdog
I recall back in the 80's Mission made an amplifier that used a rechargeable battery and you UNPLUGGED it when you wanted to listen to music. I suppose that reduced the noise? When you were done, then you plugged it back in to recharge the battery.


Jeff Rowland Design Group STILL makes audio products that are very highly regarded that are battery powered in the home. There might be other hi-end (read: thick brushed aluminum faceplates, heavy, pricy, etc.) audio manufacturers who do this; Jeff Rowland is the only one that springs to my mind at the moment, though.

I've never personally heard them, but IIRC, clean power as opposed to possibly suspect AC power is one of the reasons cited for the battery power options in their product literature.

www.jeffrowland.com/
 
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Dreamslacker

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Hmmm..

puppyslugg: Would that be Schottky diodes, barrier diodes or barrier rectifiers? They don't seem to take much voltage?

GUess I'll stick with the PS-1 design but I can't get Linear Tech. stuff locally. Shall have to settle for a LM317/337 combination, I guess.
 
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Dreamslacker

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Hey guys.. I've yet another question about the power supply. Would it do any good if I plugged in Nichicon Gold Tune 15,000uF (yes, 15,000 microfarads) capacitors after the bridge rectifier instead of 4,700uF capacitors?

How about 10,000uF Elna (generic Elna's) on the outputs as well?

I know it's kind of overkill but the capacitors are realatively affordable. I believe the Gold Tune won't run me more than US$20.00 for a pair. The Elna's are plugged out of old systems so they're 2nd hand but dirt cheap.
 
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