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Has anyone made a working Class D amplifier? Or have any experience with them? I know it is basically just an H Bridge switching at incredibly high frequencies. I am wondering because I have to come up with my senior design project ideas soon and was thinking of doing a Home Theater receiver. I could use Class AB in there but what is the fun in that? Class D is the future and it is loving awesome because of how much less power is required and how efficient they are, I really don't want to spend 20hours designing a massive toroid based PSU for a class AB circuit anyway. So does anyone have any experience in them? Hell is anyone actually working with audio a lot? I really want to learn more about it, i only have basic DSP knowledge, so effects and poo poo like that, and a moderate knowledge of low power amplifiers, I built a 50W class AB amp in lab once but that was a while ago. If we have any acoustics guys I would be so happy if you could just give a rundown of some cool stuff, like what goes into a good amplifier design and things that are more complex than just MAKE THE SIGNAL BIGGER. I say this because I see tons of schematics for amplifiers on the internet and they do things different than what I have learned, and there is a pretty common theme between the designs.
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Mar 2, 2008 20:45
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scholzie posted:.03 W / 1.5 V = 20mA, not 200mA. You can't divide a number by a number > 0 and get a bigger number than you started with. You'd need a 75Ω resistor. I think you mean "number > 1" 
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Mar 2, 2008 21:45
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ryanmfw posted:I think you mean "number > 1" Yes that is exactly what I meant oops.
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Mar 2, 2008 23:13
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I wanted to get a DSP to mess around with, i think they are freakin cool, outside of class but drat are they expensive. For a decent AD Blackfin on a test board it is $500 
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Mar 6, 2008 18:02
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Cuw posted:I wanted to get a DSP to mess around with, i think they are freakin cool, outside of class but drat are they expensive. For a decent AD Blackfin on a test board it is $500 Sound card = DSP (audio frequency only, of course)
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Mar 7, 2008 20:10
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This is the best video I've found so far for soldering surface mount stuff without really expensive soldering equipment like hot air guns. http://www.youtube.com/watch?v=3NN7UGWYmBY&feature=related
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Mar 9, 2008 00:08
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Maynardr6 posted:This is the best video I've found so far for soldering surface mount stuff without really expensive soldering equipment like hot air guns.
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Mar 9, 2008 00:40
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Sorry to bother everyone, but I have a question I need answered urgently to complete a project for a friend. I have 2 red LEDs 5mm 18volt 20mA 120mcd and 2 3volt CR2025 Lithium disc batteries and I need to know what resistor is needed between each LED and battery (they'll be completely separate circuits). Please PM, e-mail nthoms@gmail.com or reply to thread. Sorry to bust in with this trivial request; I had notations for the proper parts, but I don't know where they are and I don't have time to begin reading all of the posted texts to try to sift through just for this answer. The sifting can begin once I've calmed and made the proper circuits so I don't burn out my pretty LEDs. Thanks!
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Mar 15, 2008 02:49
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18V LEDs? Do you mean 1.8V?
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Mar 15, 2008 04:06
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Comrade Milton posted:
Well let me just do everything for you. How about you start by reading up about 10-15 posts ago where someone asked pretty much the same exact question. No one is going to grind through some stupid easy math and email you an answer, especially a question that's already been answered.
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Mar 15, 2008 06:18
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scholzie posted:Well let me just do everything for you. How about you start by reading up about 10-15 posts ago where someone asked pretty much the same exact question. No one is going to grind through some stupid easy math and email you an answer, especially a question that's already been answered. Well, if by "do everything" you mean by a lazy poo poo who'd rather write a paragraph of sarcastic, self-righteous, contemptuous poo poo rather than a one or two word answer to a simple question, then yes, you did everything. As promised, I've begun reading now that I have the time, but I ended up needing to call up a friend with a degree in EE, who informed me how easy a question it was to answer and did so quickly.
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Mar 15, 2008 19:09
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A quick question that I thought might be appropriate for this thread. I have an old 2nd generation ipod (20gig) that has the large firewire port on the top that i use in my car. I took apart the radio/cassette player and traced the cassette head audio pickups (not sure what they are called). I then attached a female 3.5mm jack to these lines. So basically a really cheap way of putting an auxiliary jack into a 10 year old radio and the sound is pretty good. The problem I am having is when the ipod is hooked up to the aux and also the car charged I get some sort of feedback from the ipod LCD screen (noise is in sync with the characters that are being update on the screen) that comes through the speakers. There is no feedback when I use a normal charger that is plugged into the mains (tested in the garage with an extension cord). So I am wondering if it is some sort of power filter (assuming thats the problem) that I could stick in between the ipod and car charger.
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Mar 16, 2008 02:14
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Comrade Milton posted:Well, if by "do everything" you mean by a lazy poo poo who'd rather write a paragraph of sarcastic, self-righteous, contemptuous poo poo rather than a one or two word answer to a simple question, then yes, you did everything. Your own loving question was answered a few posts ago. All you have to do is change the voltage and do the same calculation which was laid out in plain, easy to understand terms. So, yes, nearly everything was done and made out for you. Stop being a lazy pile of poo poo and read a thread before posting in it. In the time you took to post and reply to whine about how mean I am, you could have read the solution already. (Yes, I realize I could have also just answered you, but I'm trying to make a point, dammit!  )I don't, nor does anyone else in this thread, feel like giving away answers like we're some sort of nerd calculation factory. If you want to learn something, which I naively assumed was the point of the thread, then try to learn something. If you want someone to give you answers, pay them. Sorry for the derail, but that really pisses me off. Has anyone been playing with guitar effects lately? I built a Marshall Blues Breakers clone on my breadboard (I got the schematic from General Guitar Gadgets) and it's pretty slick - probably one of the better crunchy overdrives I've made. What's I'm really looking to do is build a headphone amp with a switchable distortion channel that can fit completely in something like an altoids can. Maybe make a little kit out of it once I get everything right.
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Mar 16, 2008 06:37
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clone posted:A quick question that I thought might be appropriate for this thread. It's probably because the normal charger doesn't suffer from current droop when the LCD changes. Car chargers have notoriously small wire and high-resistance connections which definitely limit current delivered. I bet a medium-sized filter cap in line with the positive supply wire would help a lot. Cleaning out your cigarette lighter and the terminals of the car charger will probably also help.
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Mar 16, 2008 17:51
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scholzie posted:Your own loving question was answered a few posts ago...Stop being a lazy pile of poo poo and read a thread before posting in it...which I naively assumed was the point of the thread, then try to learn something. As I said and am doing, I am using this thread to learn; I simply needed a relatively simple question answered quickly and I didn't know how to calculate the solution. Sorry if I missed the post, but you're not going to get more people interested in hobbyist electronics if you're a douche. Unless you're looking to make this happen, I'd suggest you stop being a cocksucker. Last post of mine that'll be derailing.
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Mar 16, 2008 18:58
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Comrade Milton posted:Unless you're looking to make this happen, I'd suggest you stop being a cocksucker. My whole reason for getting pissed off is that electronics (hobby or otherwise) isn't something you just pick up by asking people for answers (or as someone earlier mentioned, switching parts out until they stop getting hot). It takes hard work to learn and understand this stuff, and many, many people in this thread have spent 4 or more years of their life learning this stuff. So, it kind of trivializes all that work when someone asks for an answer without trying to figure it out himself. A simple Google search for "LED resistor" brings up hundreds of calculators and you would have had an answer even faster than posting here in the first place. I admit that I could have been nicer about it at the start, but to me it looked like you were looking for fast answers and not having to put anything into it. Especially because you asked people to go out of their way to email you. That, coupled with having a really bad day made me go kind of Patrick Bateman. So, for what it's worth, I apologize for being a dick about it.
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Mar 17, 2008 04:13
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Comrade Milton posted:Sorry to bother everyone, but I have a question I need answered urgently to complete a project for a friend. Sorry to say, but it's impossible to directly power 18V LEDs with 3V batteries. EDIT: quote:I didn't know how to calculate the solution. Of course, given your information, I get (3 - 18) / 20mA = -750 ohms. Good luck finding that component! Delta-Wye fucked around with this message at 19:24 on Mar 18, 2008 |
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Mar 18, 2008 19:17
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Delta-Wye posted:Sorry to say, but it's impossible to directly power 18V LEDs with 3V batteries. Don't be so condescending man, he made a typo. Your reds, ambers and yellows are generally 1.8 - 2.4V, it's pretty obvious what he meant
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Mar 19, 2008 00:32
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Jdohyeah posted:Don't be so condescending man, he made a typo. Your reds, ambers and yellows are generally 1.8 - 2.4V, it's pretty obvious what he meant It's not the typo - it's the fact he's DEMANDED we help him (and HOW DARE WE QUESTION IT) and he can't even be bothered to copy down the values correctly.
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Mar 19, 2008 04:03
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I've successfully made the Little Gem amp, since plans were readily available on various websites, and the circuitry was pretty simple. The main part of the circuit was the LM386, which is an audio amplifier. Here's the little gem site: http://www.runoffgroove.com/littlegem.html Now, while I can follow instructions fairly well, and I have a novice understanding of how to read datasheets, I don't quite get why the little gem works. The reason why I'm asking is because I've been scavenging parts from some broken audio equipment, and one of the ICs I pulled was a KA4558 -- a dual op-amp. I get the wiring -- I see where the audio input connects, and where the power connects, and where to ground the chip. But wiring nothing but the chip, the power, a speaker, and the input-jack for a guitar just makes the speaker buzz when I play through it. I know that I need capacitors and resistors somewhere in the circuit, and I could try to mimic what I see in the LM386 circuit, but that won't help me understand what's going on. Any explanation would be helpful. I'd like to see what I can do with this KA4558, just for the sake of experimentation.
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Mar 19, 2008 07:02
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jovial_cynic posted:I've successfully made the Little Gem amp, since plans were readily available on various websites, and the circuitry was pretty simple. The main part of the circuit was the LM386, which is an audio amplifier. With opamps, it's all about the transfer function - that is, how the voltage out relates to the voltage in and is expressed as a formula. Opamps do nothing really by themselves, you've got to use resistors and caps to adjust voltages around the opamp which generates a gain. It's hard to describe without getting into math, have a look at the first page of this document for some examples: http://www.national.com/an/AN/AN-31.pdf Looking at the non-inverting amplifier there, if you wanted the output voltage to be 20 times the input voltage, you'd let (R1 + R2)/R1 = 20, pick one resistor value and solve for the other. That's probably the most basic example you'll find. Once you start introducing caps and inductors you'll get differential equations and imaginary numbers, better to just believe that they work unless you want to teach yourself a bunch of math
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Mar 19, 2008 08:04
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Not sure if this deserves its own thread, but it's an electronics question, so I'm trying it here first. After having two CD head units stolen out of my car, I have decided to add an AUX input jack to my why-the-gently caress-would-anybody-even-want-one stock AM/FM radio. It's an ancient brick, and all the tutorials I can find either are for newer ones with a certain microprocessor, or patching into a tape player. Some of them mention in passing that "you could just connect it to the volume pot," but my volume pot has a lot of pins and no labels, so I don't know what would go where. So the question is, what's the best way to go about attaching a headphone plug to this thing? Oh, and to make it interesting, I can't get to the back of the (rather primitive-looking) circuit board -- it's heavily soldered to the case at six different points, with bent-over pins under the solder. That poo poo is not coming apart. I've got the plug all made up on a length of wire, a partially-disassembled Ford E4AF radio out of an '84 Crown Vic, and a soldering iron (and some solder, of course). What do I do? Edit: Here's what I've got to work with, electronics-wise. Maybe the place to connect the thing will jump right out at you. If not, enjoy the old-school electronics porn. (Click for huge.)  This one is vertical, attached to the back of the faceplate. Those little hooks at the bottom go into a row of holes on the other board to connect the two, and that white wire coming off the top left corner solders to the case. That's the tuner wheel on the left.  The main board. Front at bottom of picture. Shafts, each normally holding two nested knobs, are: volume/power switch (volume down 'til it clicks)/something else on the left, and tuner(not shown: little hot-pink splined shaft that interfaces with the gear in the above pic)/something else on the right. As for level of electronics expertise, I have a multimeter and (mostly) know how to use it, and I just got a cheap soldering iron and spent all day yesterday sticking bits of wire together just because I can, and can name most of the components in those pictures, though taken as a whole they confuse and terrify me. I'm fairly good at working on electrical systems that don't have all those little fiddly bits (e.g. house wiring, or under the hood of an old car). Chillbro Baggins fucked around with this message at 14:21 on Mar 19, 2008 |
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Mar 19, 2008 13:32
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Bad Angus! Bad!
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Jdohyeah posted:With opamps, it's all about the transfer function - that is, how the voltage out relates to the voltage in and is expressed as a formula. Opamps do nothing really by themselves, you've got to use resistors and caps to adjust voltages around the opamp which generates a gain. It's hard to describe without getting into math, have a look at the first page of this document for some examples: Ah, cool. That link was very helpful, and now that I have a better understanding of the language to use when researching this stuff, I'm having better results finding things on google. I appreciate the help.
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Mar 19, 2008 16:41
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Delivery McGee posted:Some of them mention in passing that "you could just connect it to the volume pot," but my volume pot has a lot of pins and no labels, so I don't know what would go where. How many is a lot? Its probably still your best bet, so you should consider using continuity on your multimeter to see if you can work out where they go (if its a combined power switch, for instance, I suspect one goes to the 12V bus on your car, one to the 12V bus on the unit, etc). If you can narrow it down to a few pins (2 or 3) I think it could be figured out.
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Mar 19, 2008 21:44
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Here's how the volume pot most likely is set up: You have 2 connections for the on off switch, and 3 for the left channel and 3 for the right. On each channel, you should have a pin that is ground, a pin that comes from the source, and one that is the attenuated output. With an ohmeter attach lead to ground, and probe around the other pins until you find the terminal that is changing it's resistance to ground when you turn the volume knob. It should approach 0 ohms when you're turning the volume knob left/down. This is the output to the amp. When you find this pin, leave the test lead on it, and take the lead off ground and put it on the other pins, and find the one that approaches 0 ohms when you turn the knob to the right. THAT pin is the input. If you can find them both, you've found the inputs to your amp 
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Mar 20, 2008 02:21
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Delta-Wye posted:It's not the typo - it's the fact he's DEMANDED we help him (and HOW DARE WE QUESTION IT) and he can't even be bothered to copy down the values correctly. I didn't demand, I asked. My typo was a period. In short: get hosed. (USER WAS PUT ON PROBATION FOR THIS POST)
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Mar 20, 2008 03:52
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Delta-Wye posted:How many is a lot? UserNotFound posted:Here's how the volume pot most likely is set up: Edit: poked at it with the meter. First pin is ground, second pin is the output to amp, third pin is open, fourth pin is the input. Now what do I do with them? Chillbro Baggins fucked around with this message at 04:58 on Mar 20, 2008 |
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Mar 20, 2008 04:27
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Delivery McGee posted:Looking at the little wheels turning through the slots in the body, it appears that there are eight on the volume part (in two sets of four), two on the power-switch part, and six (in two sets of three) on the other part that I forget what it does. Should be able to solder leads to the input ones and see what happens. Can't imagine it would hurt anything to try, at any rate. Might want to clip/unsolder the connection eventually so that your radio doesn't get mixed in. You could mount a switch (which would be pimp) to select between radio and aux. Was thinking about this today - would it be appropriate to include bypass capacitors to prevent any DC bias thats present from affecting whatever he's plugging in? This is the sorta thing I'd experiment with (I missed taking EE 272 - Hacking consumer electronics ) and just see if it works.quote:I didn't demand, I asked. My typo was a period. In short: get hosed.  Let me be more specific. You didn't come into this thread saying "hey guys, I'm unclear about X, could you explain it?" but instead you came in saying "hey, I need to do this thing but I'm too lazy to type in 'LED resistor current calculator' into Google (btw, the whole first page is pretty relevant) and read. I found this thread, but am again too lazy to read. Please do the work for me, because I am too lazy, document it, and email it to me where it will do no one else any good. kthxbye". It would have taken you LESS time to do a google search then type up your post asking for the result to be given to you. The fact that there is an obvious typo, plus the rest of the post, made the whole thing reek of self-centered absorption. You didn't miss a period, by the way, you missed a decimal point, which had a significant change to the values you had given. While it is pedagogical for me to not simply put it back in, these kind of mistakes are pretty obvious and should have been caught with a little bit of proofreading (but I guess you were too lazy...) I gave you the answer you required, as you asked, I just gave you some poo poo along with it. If you really want to tell me to 'get hosed' cause I wasn't nice about doing your work, go right ahead, but it certainly doesn't make me feel BAD about giving you poo poo - quite the opposite really. Delta-Wye fucked around with this message at 10:21 on Mar 20, 2008 |
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Mar 20, 2008 10:08
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Delta-Wye posted:Might want to clip/unsolder the connection eventually so that your radio doesn't get mixed in. You could mount a switch (which would be pimp) to select between radio and aux. Now, to figure out which is left and which is right.
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Mar 20, 2008 12:22
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And now for something completely different: I have an old Tektronix oscilloscope that uses plug-in units for the timebase and the other thing. It's missing the plug-ins, so it's basically a bigass case around a tiny CRT that can only show a dot. Is there anything fun I can do with it, or should I just start stripping it for parts?
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Mar 20, 2008 15:24
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Delivery McGee posted:I do have a toggle switch laying around unused. Not sure where I'd mount it, though, as it's pretty big. I wonder if I could repurpose the AM/FM switch, since I don't listen to AM radio. wouldn't you need a TPDT swtich for that? You have 3 channels that need switching, left, right, ground(Well ground might not need switching but left and right do). I would think a simple slide switch would work pretty well and would only cost a dollar or two at mouser.
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Mar 20, 2008 18:27
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Cuw posted:wouldn't you need a TPDT swtich for that? You have 3 channels that need switching, left, right, ground(Well ground might not need switching but left and right do). I would think a simple slide switch would work pretty well and would only cost a dollar or two at mouser. A DPDT switch would be required I think. The Am/FM switch hole may give him room to mount the replacement switch though.
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Mar 20, 2008 18:29
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I understand how the resistors relate to the gain on an op-amp circuit now. In terms of strictly amplifying the signal coming from an instrument pickup, is an increase in gain the minimum requirement to get the sound from the instrument to make something happen in the speakers? For instance, I've got this simple circuit diagram based on an op-amp:  The chip datasheet states that it can be powered with voltages as low as 6v, so I imagine I can run this off of a 9v battery. Is this circuit all that's necessary to make a mini guitar amp? I've seen op-amps used as the basis for a pre-amp, but I've never seen a simple op-amp based guitar amp, so I'm not sure. Am I missing something?
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Mar 20, 2008 18:35
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jovial_cynic posted:I understand how the resistors relate to the gain on an op-amp circuit now. In terms of strictly amplifying the signal coming from an instrument pickup, is an increase in gain the minimum requirement to get the sound from the instrument to make something happen in the speakers? There is the issue of impedance matching, which an op amp assists with because it has a large input resistance and a low output resistance (http://www.tape.com/resource/impedance.html is the first result I found that explains what I mean). Notice that the opamp uses a bipolar supply (+V and -V). If it takes voltages as low as +/- 6V, then you will not be able to power it with a 9V battery without some sort of charge pump. If it takes voltages as low as +/- 3V (not sure exactly what you meant by "low as 6v") you can power it from a 9V batter with a voltage divider (kinda ghetto, but the accepted solution for this task). The problem with a resistive voltage divider is that any change to the load affects the output voltage, and this effect is magnified as the resistance goes up (voltage accuracy is inversely porportional to power efficiency). For a battery powered device, this can be a big concern. A simple circuit like this would make a fine headphone amp, I think (haven't read the 4558 datasheets yet, but it should be fine). The big issue for a headphone amp is a bit of gain, coloring for the signal, and impedance matching, and I think that circuit can be made to do all of those things. Not sure if the gain is enough to create clipping, but another stage could be added to add distortion if it doesn't, for instance, but it would give at least good performance clean. However, I have some reservations if it would make a good guitar amp - it certainly isn't going to be driving a 4x12" marshall cab or anything anytime soon.
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Mar 20, 2008 19:28
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The increase in gain just gives you a larger copy of the voltage signal from the pickup. Putting that across a speaker won't necessarily make a sound, you need to be sure you can supply enough current as well. Op-amps designed for audio use can't usually source much current at the output. They usually have an internal voltage buffer as their last gain stage, instead of a current buffer, so they need an additional power output stage to source current to power a load (speaker). Op-amps can be used in pre-amps (they are used a lot in distortion and overdrive pedals) but they can't act as a power amp. If you wired that circuit to a speaker, you might get a very low power guitar amp, which might be too quite to be useful. Or you might pull too much current from the op-amp and fry it. If you added a power output stage using a transistor(s), you could have a small guitar amp, but then thing get even more complicated. This is why LM386 is so popular, it has all these stages in one chip.
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Mar 20, 2008 19:38
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Delta-Wye posted:However, I have some reservations if it would make a good guitar amp - it certainly isn't going to be driving a 4x12" marshall cab or anything anytime soon. I wasn't thinking anything big like that. I built the LM386-based Little Gem amp as a practice amp for my mandolin and electric violin. I just like the idea of pocket-sized travel amps. the wizards beard posted:If you wired that circuit to a speaker, you might get a very low power guitar amp, which might be too quite to be useful. Or you might pull too much current from the op-amp and fry it. If you added a power output stage using a transistor(s), you could have a small guitar amp, but then thing get even more complicated. This is why LM386 is so popular, it has all these stages in one chip. Ah... that makes sense, too. I've been wondering all this time what made the LM386 work as a small guitar amp. Thanks.
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Mar 20, 2008 19:49
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Delta-Wye posted:You didn't miss a period, by the way, you missed a decimal point, which had a significant change to the values you had given. While it is pedagogical for me to not simply put it back in, these kind of mistakes are pretty obvious and should have been caught with a little bit of proofreading (but I guess you were too lazy...) Not too lazy. In a hurry! QUICK! I NEED BLUE LEDS STAT. On the issue of travel guitar amps: I really, really like the TL072/82. They have a little more meatiness in the mid-rages and the FETs do a pretty good job of reacting to input signal spikes (smoother, like a solid-state tube). Last LM386 amp I built was a little tinny sounding, even after adding an active low pass filter. Also, as Delta-Wye said, a 9V won't supply a bi-polar 6V source without a charge pump. The LM386 should be more than happy with a +/- 4.5V supply though, and making a bi-polar supply is as simple as adding 2 resistors and 2 capacitors into the circuit (just 2 resistors would do it, but in a circuit where signals are involved you want to use caps to keep the voltages stable WRT the common lead).
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Mar 20, 2008 21:40
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scholzie posted:Not too lazy. In a hurry! QUICK! I NEED BLUE LEDS STAT. Regarding the v6 source, you guys are speaking a little over my head. All I know is that by looking at this page, it says "Supply Min = 6 Volt; Supply Max = 36 Volt". And when I look at the LM386 cover sheet, it says that the chip has a "Wide Supply voltage range: 4V-12V" And knowing that the LM386 can be powered by a 9v, I assume that the meaning is similar -- any DC power supply between 6v and 36v (like a 9v battery) will work for the KA4558. Am I reading that incorrectly?
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Mar 20, 2008 21:51
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jovial_cynic posted:Regarding the v6 source, you guys are speaking a little over my head. All I know is that by looking at this page, it says "Supply Min = 6 Volt; Supply Max = 36 Volt". And when I look at the LM386 cover sheet, it says that the chip has a "Wide Supply voltage range: 4V-12V" And knowing that the LM386 can be powered by a 9v, I assume that the meaning is similar -- any DC power supply between 6v and 36v (like a 9v battery) will work for the KA4558. The thing about opamps is they need dual voltages, because they amplify signals that have both positive and negative voltage. Without positive and negative voltage (or differential voltage, such as from a voltage divider) the opamp just won't work at all. It will "do stuff" but not what you think it should be doing. With DC filter caps on the input and output, it won't do anything at all. I played around in spice with this for a bit and am convinced that opamps are magic.
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Mar 21, 2008 00:11
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Delta-Wye posted:You didn't come into this thread saying "hey guys, I'm unclear about X, could you explain it?" but instead you came in saying "hey, I need to do this thing but I'm too lazy to type in 'LED resistor current calculator' into Google (btw, the whole first page is pretty relevant) and read. I didn't even know how to phrase what I didn't know, so Google wasn't of much use. Delta-Wye posted:You didn't miss a period, by the way, you missed a decimal point You realize the two are the same thing, right? Small, identical dots? Just that one comes with grammar and the other with numeric values? I don't know if they teach anything except equations and being a smug prick at engineering school.
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Mar 21, 2008 02:10
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