Power Supplys for Fools

  • Thread starter Thread starter Tremaine
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Tremaine

Tremaine

Chancellor of the EOPA
High guys.
I've been researching op amp's and effect pedals, but im having a hard time finding any beginner info on power supplys.
i got a bunch of junk lying around, ie: wall warts and transformers, but i dont know how to figure out what i need to power my imaginary mic amp and pedals. So a little guidence and maybe some links would shut me up so you all can get onto more important things.
also i would like to know how to test the transformers, i got a dmm with PNP NPN sockets, someone told me thats what there for?...
Thanks for your time.
Peace World
Tremaine
 
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The sockets are for testing transistors. Personally, I find them pretty useless.

You might want to start with the classic book by Craig Anderton called 'Electronic Projects For Musicians.' It's been around for a long time, but does a great job of covering the basics.
 
the amount of current you'll need is determined by the circuit you design... you need more detailed background in this before you tackle designing a pre or anything else for that matter... that anderton book would be a good start... or a beginners tech class at the local tinkertoy tech... (junior college)
 
Could you please post a picture of your "imaginary mic amp". :confused:
 
Acid..er.. LSD: thanks for the book, i bookmarked it, gunna get it soon, but im on 56k pulling 28k and the book is 45mb, must have lots of good pic;s, i'll Download it when i get the speed. thanks again dude, this is what i was looking for.
As for pic's, i got one i found on the net... but what i want to know, is how you find the sum of your power needs, is it all in the ic's or do you have to add in electrollic caps?
i understand i need a power supply with <for example> +15v -15v 0v. is this built into the transformer? or do i need to split it on the board? <witch probably wont be a board the first time, just a mass of wires.>
What i want to built, for a first attempt is a 2 channel mic mixer.
i got a 2072 chip, witch is a duel op amp, and better then a TL072,
from what i understand, i need onw other chip, to boost output and recover losses jjust before the out put, but this only need be a power amp right?
Heres my spec's , i looked at alot of mixer spec's and this one made me tingle the most. its got everything i need, and i wood like to built a big one someday, but for now a two channel mic mixer with stereo outputs.
So is it a good scamatic? worth trying? could i put a driffent op amp in each module? or a driffent module in each module slot?> or wood the power requirments make this unbareably difficult. did i ask enuff questions? can a person ask to many questions? what is the revelance of mixer design relative to human mortal existance and the imortality of the human spirit, and how many op amps does it take to reenact the great spider massacure?!?!
Thanks alot people of the world, no one else in my family <band> has the will, or the means, to figure out this circuit boarding, but i allied <all-eed, ollied> a pop can once, so that makes me qualified, or nomanated...
Peace World
Tremaine
 

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Whoa there, big guy...

What you have in that schematic is just the output section, where the outputs of the individual mic preamps are added together before beng sent on their way as a stereo signal.

Your initiative is impressive and to be applauded.

Back to power supplies for a second...

The transformer basically takes the electricity from the outlet which is at somewhere around 120 volts AC, and changes it into another voltage or voltages, but still AC. You need DC to power your circuits. The actual power supply section generally consists of a couple of functions, rectification (changing AC to DC) and regulation (assuring that the voltage stays stable).

Like I said, your initiative and willingness to learn seems impressive. Do a little more research on the basics and things will start making more sense.
 
Troll onward!

ok, so im not gunna stop trollin! "i like it." <in the words of my son>
i understand this is the output section of the mixer, does it look like it will work? is it worth my effort. i get how most of it works, i've been staring at a behringer i got off ebay for 2 weeks, mx1604a, that was broken, and magickally, with yous help, now it lives again, in full stereo.
i beleave i could chuck this thing together, with some time, that i got now, i just cant figure out the transformer thing.
i think i need a 15 volt power supply with 2 ins and three outs <over simplifyed i know> witch i have. an older tape deck with mic inputs should have something simular right, i got 3 half gutted.
im a artist, a song wrighter, and i was just trying to get people hooked with my story telling. and BTW, op amps do look like little spiders, admit it you guys play spider wars all the time.
Peace World
Tremaine
 
OK, for the 5% chance you aren't yanking our chains, sure DIP-8 and SOIC-8s look like spiders. But not all opamps are those packages, and only a small portion of chips in those packages are opamps.
 
See, i was right all along, well now that, that is solved i guess we can all move on.

tl07X family
Typical values of Basic Parameters:
Slew Rate: 13V per microsecond
Noise: 18 nanovolts per root Hertz
Rail Voltages: +/- 2V min, 15V max
Input offset: 2 mV
Input Resistance: 1 TeraOhm (! On a dry day!!)
Input current: 30 picoAmps
Voltage Gain: 100,000
Unity Gain-Bandwidth product: 3 MHz
Supply Current: 1.2 mA (071), 2.4 mA (072)
Output Load: not less than 2 kOhms

so thats the stats for the tl07X family
i read that "The 072 has the same performance as the 071, but the performance of the 074 is slightly poorer as a sacrifice for fitting so much into one pack."
So im looking at tl072's

now if i look at the sca-matic it dictates that i need, 4 op amps for the op put, plus 2 more <unbalanaced mic pre> or 6 <3 each, for balanced mic pres.>
so lets say unbalanced for now. so thats 6 op amps, < or is it two op amps, and 4 power amps?>
anyway, i assume that the +/- 2V rail voltage, times 6 and the amperage 2.4mA are the two numbers that affect the power supply.
So do i just add these together, without exceeding the 15V max?

+12V /-12V and 14.4mA <it cant be this simple>

is there other factors that effect the supply of power needed?

btw you can bend the spider legs to alter the spiders attack and defence stances.

Peace World
Tremaine
 
Such a silly thread . . .

You don't want to use those for a mic amp; their input noise is too high.
 
Tremaine said:
anyway, i assume that the +/- 2V rail voltage, times 6 and the amperage 2.4mA are the two numbers that affect the power supply.
So do i just add these together, without exceeding the 15V max?

+12V /-12V and 14.4mA <it cant be this simple>
Click to expand...
Using a +/-2V supply will give you a maximum output of slightly under 4V peak to peak (or around 1.5 RMS). Using a +/-
15V supply will give you a maximum output of around 30V peak to peak (around 23V RMS).

You need a power supply that will give you all of the voltages listed in the schematic if you want it to work like the one in the schematic.

You really need to do a LOT more research. Not on the specifics of the circuit in question, but on basic circuit operation, start with a focus on power supplies. Do a lot of reading on basic electronic theory.
 
LDS said:
Using a +/-2V supply will give you a maximum output of slightly under 4V peak to peak (or around 1.5 RMS). Using a +/-
15V supply will give you a maximum output of around 30V peak to peak (around 23V RMS).
Click to expand...

VRMS = (Vp-p / 2) / (2 ^ 0.5), so only 10VRMS from a 30V supply, and that's only if the device is rail-to-rail.
 
Spider Bite

So i looked up RMS on wikipedia, and yea, its over my head, i read it three times, and still couldnt rap my head around it, so your right.
im not happy about being defeated by robot spiders.
any items or magick spells, that may help me on my jurney, wood be greatly appreated.
/me packs his backpack in preperation of the long jurney.
Peace World
Tremaine

btw: whats a worthy op amp?
 
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