What's important with power supplies?
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TaffyGuy

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do you other amp builders get little pops when you power on and off the amp with the phones in?

its not *that* bad, but i try to have the phones out anyway while i change the power on/off. is there a simple fix for this? bigger bypass caps? somethign else? this lame ass amp i made just has 10nF bypass caps on the op amp becuase thats what was in the spec. i see you people use 1uF wima's and such.

also i've got 220uF elects on the batteries/battery eliminators (before i make a real power supply) and havn't bought any buffers yet. (any suggestions on cheap ones i guy buy a bunch of to experiment with? bb's?)

also, i stopped at the surplus store near me and found a bunch of 2.2uF wima's that are little red boxes (50v) marked radial. I'm still having a hell of a time learning the whole part crisis ordeal since this is my first taste in non-theoretical EE... do these count as the magic wima's that everyone uses?

crap the stupid thing is almost as long as it used to be. so i won't feel bad if you continue to ignore me
 
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TaffyGuy

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now that i'm thoroughly embarrassed... *bump*
 
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aos

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Pops/thumps are pretty common. Some people claim that if you use Elna Cerafines to bypass your power supply that the thumps go away. How much of thumps will be audible depends on the topology of the amplifier.

Those WIMAs you mention seem to be polyesther based on your description. They should be pretty decent for power bypass, but people claim they are not all that transparent when used to couple signal. They should still sound better than electrolytic capacitors, and if you get them at good price they certainly have their uses.
 
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TaffyGuy

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they were 75 cents each. the ones everyone uses are MKS2 or something? different material huh? i guess i just need to be patient and learn this stuff as it comes but its very frustrating, because i just got my whole electronics station as a birthday present and i really want to get started building more amps


perhaps i should start out not worrying about name brands so much, because i think i still have a long way to go before that's gunna be much of an issue. types are probably pretty important still though. 2.2uF sounds small to be used at the power supply stage... but i'm not thinking clearly right now... power bypass you mean the ones right next to the +/- on the amp. i have lots of studying to do *sigh* probably a better idea than wasting all of your time.

while i'm on a roll with stupid DIY questions...
which buff is cheap and does the job and who carrys it?
I have to order all the good AD amps direct from AD? it seemed to say i had to be an oem or something. maybe it will work if i just register...

tnx aos...
 
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ppl

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TaffyGuy> I don't think people intentionaly ignore a post but may in fact be like me and think that some posts are better answered by someone other than them self. so don't get disipointed. Regarding the Turn on thump Every solid state Amp i have ever used has a Thump and most Non DIY Amps have a relay on the Outputs to Time delay the Connection of the load for a few seconds.
 
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tangent

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Turn-on thumps (and -off thumps) can also depend on the op-amp. Some chips are noisier than others when coming up or down. The AD843, for example, which is sonically excellent, makes bit of noise coming up and is positively ugly sounding going down. Other chips can be almost silent in each direction.
 
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TaffyGuy

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ahh thanks i'm much less worried now
and sorry ppl i wasn't trying to fish for pity, just trying to be humble (becuase i know how obnoxious i am
)

i had to bump to get an answer on that quesiton because it can be a bit of a shocker when i've got etys shoved up my ear canal, and i didn't want to blow anything out (ety or ear)

just went to rat shack on the way home from work to get some more boards and such. perhaps i'll put together a little tiny classic cmoy out of boredom before i get off my ass and order some real parts...

hey another thing, whats that no-rubber-but-still-insulated hook-up wire that sijosae uses to make pretend traces for his board layouts? my dad was telling me about it but he's out camping with my mother so i'm all alone with no experts in the house... tell me if i get too loud.
 
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tangent

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If the turn-on thump is loud enough that you're worried about your ears, something may well be wrong. One thing to look at is DC offset on the amp's output. If it's more than about 20 mV, it can increase the loudness of the thumps. You're hearing the driver 'pop' when the DC voltage hits it and the driver just goes out in one direction and stays there.

On the wire, I've seen sijosae use a few different kinds. Mostly he uses insulated wire that looks like 30 gauge magnet or wire-wrapping wire. You can get it everywhere, even Radio Shack. His most recent project -- the surface-mount CMoy -- seems to use uninsulated wire, but it may be clear-lacquered wire. The only place I know of to get lacquered wire is for some high-dollar stuff. (Percy Audio) There are probably better places to get it if you're just looking for generic wire.
 
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TaffyGuy

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yeah i thought it might be magnet wire. ever use that? does the flux burn off the insulation just right at points of contact? or perhaps i have to get just the right kind so it works right... oh well, i layed out a closer-to-spec cmoy light night i'll probably just solder together with crappy plastic covered rat shack hookup and stripped crappy rat shack hookup and perhaps after some experience i'll know what i need better.

really need to make that damn parts order.

oh one question about the cmoy. it says to use 220uF 25V elect. for the power stage, and i have a couple 220uF that are 35V and funny shaped, and i have a couple 10V that are tiny. they're never gunna exceed 10V, so why not use the tiny ones? hard to get this all straight. i was thinking of putting the little 220's in a row with some 22's and 2.2's sort of like in the meta power stage. to be honest i don't know what this even does, since theoretically it just adds more capacatance... and i remember my dad saying that in that configuration the magnitudes should drop by 10x to avoid distortion from cross inductance or something, as a critique of you're default values in the meta (470u 470u 4.7u...)

i guess if nothing else i can always experiment.
 
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aeberbach

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TaffyGuy: I have bought wire from handmade electronics in the past - hndme.com. He sells among other things silver wire and teflon spaghetti to cover it. Very nice to work with, and the teflon won't melt as you solder.
 
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taffyguy,

those smaller caps in the META42 are meant to be placed as close to the opamp power pins as possible. also, i believe typically those capacitors should be types meant for high frequency use
 
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jarthel

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there are recent discussion in diyaudio.com and in headwize.com about power supplies. You might get some ideas from those threads. In diyaudio.com, the thread is in "digital" section and titled "improved LM317". There's only 1 section in headwize.com about DIY so you won't miss it.

Here are the things I found important in a power supply during my time when I was researching the net and building my amp:

1. Design is very important. For a good design but not so much hassle, try Kevin Gilmore PSU for Pure Class A. It can be found it headwize. There are other supplies designs like Jung but they are harder (to me anyway) to make it seems by just looking at the schematics.
2. I also think in a power supply the important thing is to keep those transformers away from the amp circuitry as it'll introduce alot of humming.
3. Grounding is also important. From an article I say, it said the best place to tap for ground is after the capacitor after rectifier bridges. I think this article assumes you are using dual supply. Star grounding is the best grounding scheme out there is seems based on my readings.

I'm also assuming you're not making a portable amp.


But some of what I said like star grounding applies to portables too.

Jayel
 
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TaffyGuy

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yikes okay thanks, i frequent headwize but diyaudio is a new one to me... basically i'm trying to grasp the basics and hopefully understand the logic behind the distortion and noise control... and for now i am sticking with small amp designs. my thread title is a bit misleading, as i did a lot of editing to make my initial question legible. for now i'm trying to go along with the accepted norms for ps and other, and not worry about specifics until i can experiment and start to hear differences.

well for the sake of practice (since for some reason i have a fear of making digikey orders and have no buffers or good parts) i've been putting together a classic cmoy with 1 9V (my first ugly amp was thrown together with dual 9v power supply... people here don't like either but whatever.. i'll figure it out later) so anyway i'm just trying to get practice soldering and with layout and hookup and with different protoboards and such. its coming out rather nice looking, used some random cheap MFD caps in the signal which seemed like a bad idea, but of all the brand name this and that, none of those seemed to be the input caps so again, whatever, i'll experiment. also from my first order i've got some opa2134's and i think they're rather easy to please, so no biggy.

i got some of that magnet wire and it can be a pain in the ass to use, but i'm getting the hang of it and it helps imensely in hooking up a neat layout... although taking forever to finish (couldnt do it last night)

also i went to my crappy little store thats on the way home from work and found a bunch of elna 1000uF 16V and 100uF 25V which are both rather small, but due to "buzz" i bought a bunch of each. so are these the magical cerafines? heh.

that was long, as usual. hope you made it. tnx for help.

hey tangent, those pcbs of yours would sure make this easier, you expecting them soon??
 
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tangent

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Quote:

i have a couple 220uF that are 35V and funny shaped, and i have a couple 10V that are tiny. they're never gunna exceed 10V, so why not use the tiny ones?


Your funny-shaped ones may not be electrolytic, but without a better adjective than that, I can't guess further. But yes, there's no advantage to using higher-voltage caps than you need. You pick the capacitance first, the construction and dielectric material stuff second, and the voltage tolerance last. Voltage tolerance is last because as long as it's higher than the actual voltage in your circuit, it will work.

On the cap paralleling thing, I've seen mentions of that sort of thing now and then, but I have yet to come across something definitive in a textbook. I'm not saying your dad is wrong, I'm saying that I don't have any theory to use to reason about what you're talking about. All I can tell you is that the capacitors in the META42 have different, independent purposes, so their values and compositions are different. They aren't chosen for any synergy beyond that limited purpose.

Quote:

does the flux burn off the insulation just right at points of contact?


Flux? What does it have to do with burning things?

If you've got the enameled type of magnet wire, the right way to get the insulation off is to use a solder pot, but those are expensive. The only other alternative is to scrape it off, which is difficult. Your iron won't be able to burn the enamel off easily, unless you have a really hot iron, and then you have other problems.

If you want thin wire with a minimum of heat-resistant insulation but still want to be able to get it off with wire strippers, I would suggest Teflon-coated or irradiated PVC-coated wire. Solder at reasonable temperatures won't melt either. Irradiated PVC is especially interesting -- you can think of it as "pre-shrunk" PVC. Regular PVC shrinks and bubbles when it's hot, but irradiated PVC will put up with a fair amount of heat, and it's a lot cheaper than Teflon. I use 24 ga. Alpha brand wire from Mouser. It's as thin as my 22 ga. Teflon-coated stuff, although to be fair, I would say that the Teflon-coated wire is probably closer to 24 ga in reality.

Quote:

those pcbs of yours would sure make this easier, you expecting them soon??


I have them now, but I'm not ready to start selling them yet because I still haven't built an amp on one yet. Until I'm sure it will work, I won't offer them to others. I have an amp half-completed now, and hope to finish it tonight.
 
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TaffyGuy

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thats sweet, i'm also finishing my second spare part amp tonight... dono if its gunna work or not (this one is without "adult" supervision
)

with the magnet wire, i got real thin stuff on recommendation, hopefully not too thin (28 gague), and at first it was a pain deal with because the insulation didnt just melt off when you heated it like i sort of semi-understood from my dad's story, but it's a hell of a lot handier than the plastic covered radio shack crap i bought in prep for my first attempt.

by funny shaped i meant its just the wrong size for what i'm doing... all tall and thin... where i see all the ones in the pics are short and fat so they'll fit in little cases. no matter, i'm using the tiny 220's cuz i'm only on 1 9V and i'll save the elnas which i can get more at 40 cents a pop so i guess thats good news...

i'm still confused as **** as far as the in signal caps go... would those be described as MFD or is that the kind that the wima's are, for high speed resivour only. or maybe they're both different kinds of MFD. anyway i finally made a digikey order, so at least i know i have the right types of stuff from that (used you're {tangent's} site, and have been studying it a lot) i'm still impatient and want to know everything about everything right now, but i guess i'm chuggin' along fast enough. if that magnet wire is crappy for the job, too bad i just bought 6 bucks of it, but no big deal.

(i asume MFD means metal(ized) film dialectric, so probably they're both different kinds of it)

oh and my equipment is fine, i think my dad got excited that i was getting into a productive hobby that we share interest in and went for broke on my birthday (regulated webber solder station, true RMS ProTek DMM that even hooks up to my computer, tools, etc)

yay marathon posting. i'll never stop!
 
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