My META42 parts list. Advice needed.
Jun 28, 2002 at 12:50 AM Post #16 of 31
Quote:

If you buy AA batteries in bulk, they're about 90 cents apiece -- you'd only have to buy 34 of them before a $30 power supply paid for itself!


And as the batteries drain, performance goes down, as well. With a reg. psu, performance is constant.
Quote:

Remember, we're dealing with a guy here who's complaining about spending $30 on a power supply.


Who, me?
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I don't ever recall bitching about spending $30 for a psu. I've built psu's costing way more than that.
 
Jun 28, 2002 at 12:59 AM Post #17 of 31
Ok fine, I'll spend more money on the PSU. He's talking about me btw puppyslugg
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Looking at the Digi-Key catalog I only see 5V and 12V under the W08XXX series.

Shouldn't I be using a 24V one? Elpac # W2412-760

Tangent, does my part list look ok? List remains the same as my initial post but the capacitor has been changed to 330uF 25V 12.5mm (4X).

Elpac's DC jack size is 2.5 X 5.5 right?
 
Jun 28, 2002 at 1:06 AM Post #18 of 31
Sorry for confusing you two, fyelow and pslugg. You newbies all look alike.
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(Runs and ducks....)

Quote:

Looking at the Digi-Key catalog I only see 5V and 12V under the W08XXX series.


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Sigh.

Quoting my previous message: "...Elpac's WM series. (Not to be confused with the MW series or the W series.) "

I would also suggest searching simply for "Elpac WM", because not all of the interesting items begin with "WM08".

Quote:

List remains the same as my initial post but the capacitor has been changed to 330uF 25V 12.5mm (4X).


I use those capacitors myself -- they're great little things. My other favorite of the ones I pointed out are the 1000uF/25V ones, for times when you can afford the extra part height. (30mm!)

Quote:

Elpac's DC jack size is 2.5 X 5.5 right?


Yes.
 
Jun 28, 2002 at 1:22 AM Post #19 of 31
Quote:

Sorry for confusing you two, fyelow and pslugg. You newbies all look alike. (Runs and ducks....)


Thanks. I feel much better now. For a moment there, I thought I was going need to talk to my psychiatrist.
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Jun 28, 2002 at 2:31 AM Post #20 of 31
Haha sorry Tangent but you have to put up with my stupidity
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I searched the entire Digi Key this time and I can't find a WM080.

Did a search on Newark and came up with this
Elpac WM080-1950-760
External Regulated Power Supply, Wallmount, Single Output, 24 volt at 0.33 Amp, 1.57 inch Length x 2.18 inch Width x 3.21 inch Height

This will do right?

EDIT: Newark doesn't sell the 330 uF Cap I need!
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Jun 28, 2002 at 2:54 AM Post #21 of 31
Quote:

I searched the entire Digi Key this time and I can't find a WM080.


As I said, these three distributors each have different subsets of the line. In other words, no one distributor has all Elpac WM series models, as far as I can tell. '80s can be had from Newark and Allied.

The Newark part you found is the right one, fyelow.

But, don't just stick with the '80 because I said so. Get the datasheet from http://elpac.com and see if there's a supply that would suit your needs better. For the AD8610, for example, a 24V supply is awfully close to the chip's limits. You might well want to go down to 15V, or maybe even 10 or 12V. On the other hand, since the Elpacs are tightly regulated (i.e. they won't go over 24VDC until the input voltage goes over 132VAC), you may feel safe at 24V with this chip and this power supply. You'll have to make that decision on your own.

Quote:

Newark doesn't sell the 330 uF Cap I need!


Newark has a pretty weak selection of high-quality, small-size caps. They have some low-quality stuff, and some really good stuff (i.e. Orange Drops), but nothing in the middle of the road. For a portable amp like this with limited space, it's best to get caps at DigiKey or Mouser -- they've got reasonable selections of good-quality parts with compact footprints. If footprint wasn't a concern, I'd say go with Orange Drops and Cerafines and other exotica -- but they just don't have reasonable capacitances that fit this board.
 
Jun 28, 2002 at 3:19 AM Post #22 of 31
Hey Tangent I found another one that I think might work.

It's a Desktop power supply.

Elpac FW1824-760-NC
24V DC 0.75A
I have to purchase the cord seperately but that isn't a problem. I believe the jack size is correct as well.
Datasheet

Cheaper too, $21 at Digikey and $6 for the cord.

EDIT: I'm using the OPA637s so 24V should be well in spec.

EDIT: Scratch that, min order 25 pieces!

Im debating whether I can get away with something lower, like 12V or something.
 
Jun 28, 2002 at 3:33 AM Post #23 of 31
Antique Electronic Supply sells Solen Fast caps, AuriCaps, and Hovland MusiCaps, all would be quite boutique for C1L & R. I got a pair of the 1uF Solens and they fit the board SOOOOO nice. The AuriCaps don't fit the board but they have long leads....

Alas, poor fyleow, you are learning the most painful lesson of DIY - no one place has it all! The above site has a lackluster selection of electrolytics and their resistors start at 1/2W.
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Why can't one place have it all?
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There is an alternative though - leave stuff out! It saves you time and $ and gives you a future project at the same time!

You can probably live without C1L & R as well as the C4's and C5's (provided you are not using a mischievious opamp). Some of the resistors arent needed as well. Once you get your resistor values settled check the Shack - they sell 1% metal films too.

When the dust settles and you have the thing working, then start replacing and adding parts. If for no other reason than that you can see what difference things make.

ok,
erix

p.s. I like the 3-12V power supply from the Shack. It's moderatley well regulated, comes with a tip of your choice so you can figure it out in the store, and costs $15. Sure it puts out 15V at a light load - consider it a gift.
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Jun 28, 2002 at 4:01 AM Post #25 of 31
Yea Erix I am feeling the pain! What do you mean by mischievious opamp btw?

How about his Phiphong power supply?
522-PSA-21R-240

Stats:
24V DC 0.83 A
With Loadsense technology! (whatever the heck that means)
It says Regulation +/- 1% and +/- 2%
Ripple is 240 mV

This sounds in line with the Elpac stats, will it do as well as the Elpac (please say it will i'm tired of looking!)

On another note Phiphong likes to call some of their stuff "Linear Eliminator" does that means it's a regulated linear PSU?
 
Jun 28, 2002 at 4:18 AM Post #26 of 31
The voltage and current rating should be adequate. Though tangent may not agree with the voltage rating. I believe he thinks it may on the edge when powering ad8610/20's.

Who sells this unit? How much?
 
Jun 28, 2002 at 10:30 AM Post #28 of 31
The Elpac FW1824 and indeed, most switching power supplies are totally unusable for the META42 because one of the two outputs are tied to AC ground. This causes the virtual ground to be dragged to negative rail and shorted, wrecking your amp. Always test your power supply to make sure neither side is tied to AC ground before using it with a META42 or any other circuit that uses a virtual ground.
 
Jun 28, 2002 at 10:56 AM Post #29 of 31
Morsel's right, although it only applies to 3-prong power supplies, because of the way some audio components handle case and signal grounding. The Radio Shack switchers use two-prong plugs, for what it's worth; the one I use (RS 273-1668) doesn't seem to have this problem. On testing it, I get megohms of resistance from one end of the power supply to the other -- I guess that's good enough....

Linear regulated and unregulated power supplies don't have this problem because the transformer isolates the DC from the house's ground setup.

One way to avoid this issue with switchers is to get a dual-voltage model, because then you have a "real" ground, which can connect to the house's ground without problem.
 
Jun 28, 2002 at 12:10 PM Post #30 of 31
I use 10 volt caps on all my battery powered Amps. this because the rated capacitence of electrolytics go down if operated at lower than there Rated Working voltage. A 220uF cap may have only 100 uf if operated at half its rated working voltage that is why it is called working voltage. to solve the wall wart problem Put a low cost 3 term regulator IC like the LM-7818CT I use one of these and put an LED from the Gnd term of the reg IC to the Oposing supply rail so as the nominal 17.5 volts output of the reg is about 19 volts.
 

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