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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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scholzie posted:You can also build an overdrive stage by using a dual op-amp design. Use one opamp to amplify, and one to clip (or vice versa). Diode clipping can tend to be really tinny and gross, but red LEDs sound nice as clipping diodes (the color of the LED actually makes a difference!). Actually, diode clipping sounds pretty good, it's very common in overdrive and distortion pedals. Clipping an op-amp sounds pretty bad, op-amps are not designed to be operated this way and usually don't handle clipping very gracefully. If you look at the Bluesbreaker schematic again, you can see that the first stage amplifies the signal to usable level and acts as an input buffer. The second op-amp has 4 diodes in it's feedback loop, this is where the clipping takes place. The first gain stage is completely "clean", and in the newer version of the Bluesbreaker you can bypass the second stage for clean boost.
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Mar 21, 2008 23:19
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hobbesmaster posted:The problem is that your time is worth money, that black box is one less thing you have to design and implement. If you have never designed and implemented that black box or don't know how, then you really shouldn't be using it.
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Apr 18, 2008 22:50
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mtwieg posted:-Run all the leds in parallel. The simplest way to do this would be for one light, each led is in series with its own current limiting resistor, and all of these are supplied directly from my batteries and driven with one low side switch. This would be simple and cheap, but efficiency would be crap because I lose power over the resistors and the switch. Also variations in the Vf of leds will cause variation in brightness; how much, I'm not certain. You might not see a difference in brightness, but there will be a difference in current through each LED (current through a diode depends on the voltage across it), and Vf can also vary with temperature. If you have unstable current distribution you will eventually end up with one LED burning out before the others, and the remaining diode will then have to "share" even more current than before. e: gently caress, didn't read that you were giving each LED it's own resistor. Sorry. This probably won't be such a problem then.
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May 7, 2008 23:07
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catbread.jpg posted:stuff on C vs Asm This is a good point when talking about PCs, but compilers for MCUs are often pretty lovely. Also C cannot match hand-written assembly for writing small code, which is often a concern on MCUs.
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Sep 12, 2008 13:03
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I don't think you need to bother with AAP if you just want charging and line out.
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Dec 25, 2008 22:52
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Most op-amps use the same pin-outs, you can swap one out if you think the cheaper chips aren't up to scratch.
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Feb 3, 2009 16:44
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An inductive load would probably kill the MOSFET too.
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Mar 27, 2009 19:03
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Why does the NES need to copy the data out of flash and into SRAM? You could use a small microcontroller to look at the address lines and move data around as needed. This would probably be the same price as buying some logic gates if you want DIP chips. IIRC some larger NES games had special memory mapping chips to do just this.
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Jul 28, 2009 23:32
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Keebler posted:I did think about using a micro controller but I thought it would be more elegant to have the NES CPU do all the work (plus I know it's possible as someone else managed to pull it off). The mappers themselves are a whole other beast. Any game worth playing uses a mapper. The only ones that don't are Super Maro Brothers, Excite Bike and a handful of single screen arcade conversions (Burgertime, Joust, etc). I initially toyed around with using a micro controller to simulate the mappers through software emulation. Ultimately I decided to use a FPGA instead, mostly because my experience with them is very limited and I wanted to learn more. It also potentially could do away with some of the inaccuracies I hear exist with software emulation of the mappers. Cool, if you want to look into emulating mappers in an FPGA you should check this (http://tripoint.org/kevtris/Projects/console/) out and maybe contact the author.
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Jul 30, 2009 01:45
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Poopernickel posted:I'd recommend using your regular toaster oven. Get a separate toaster oven, eating soldery food will give you lots of cancer
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Aug 8, 2009 20:07
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obso posted:I would kill for a local electronics type store that wasn't RS. That's funny, there's a european distributor called RS that's really cool http://radionics.rs-online.com/web/ 
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Oct 29, 2009 19:44
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Delta-Wye posted:If you just need a differential signal 2 Schmitt triggers isn't the best design, you're assuming that both triggers behave identically. A single trigger with an inverted after it would be more reliable (apologies if I've completely misread what you need, I'm really in need of a coffee right now) e: also "Opamps for Everyone" is a good free design reference for this kind of stuff http://focus.ti.com/lit/an/slod006b/slod006b.pdf the wizards beard fucked around with this message at 13:27 on May 10, 2010 |
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May 10, 2010 13:22
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Slightly unusual case here: I want to measure outputs of VCOs in the regions of hundreds Mhz. I have access to a spectrum analyser that sweep up to 3Ghz, but unfortunately I don't have any high-frequency probes, just cheap passive oscilloscope probes (rated to ~100Mhz). My initial dirty solution was to loop the source signal from the analyser through the probe and back into the input to measure the frequency response of the probe. I can then weight any measurements using the probe responses. Can anyone convince me that this won't work?
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May 27, 2010 18:54
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Frequency and amplitude, but I'm not looking for incredible precision. I did some quick tests and the probes have a peak of a few dB around their rated maximum frequency and attenuate ~40dB in the 100s Mhz range but it varies across the spectrum. I think this will work.
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May 27, 2010 19:22
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ANIME AKBAR posted:Do you even need scope probes? Most spectrum analyzers expect a coax cable directly to your output, no probes involved. Yep, I need 'em to... probe the circuits? There are no handy BNC connectors, just a fairly tight PCB
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May 28, 2010 01:43
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ANIME AKBAR posted:Well you don't always need a scope probe to probe something. Generally with RF stuff you just put coax connectors on signals you want to use. Check out the datasheet for the analyzer. If the board is too tight for a connector, you could use a BNC to minnigrabbers or gator clips cable. You probably don't need anything terribly fancy for your application, as long as you don't mind a bit of distortion. But any coaxial cable is going to present a capacitive load. Going by back of the envelope stuff it looks like a probe should perform as well as a BNC/gator cable. I'll give it a shot, I'll have to try out the various probes at hand to see what will give the cleanest response.
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May 28, 2010 16:22
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Zuph posted:Although my anecdotal sample size is pretty small, I have never encountered an EE whose school offered an appropriate C course for Embedded programming. My school taught us C, the closest we got to embedded programming was implementing simple FIR filters on DSP chips. Still laid the groundwork though. We also learned a few assembly dialects through processor design courses.
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Jun 2, 2010 16:11
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There's no way to say if that's normal because there doesn't appear to be any scale on anything.
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Jan 20, 2011 16:17
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Please stop saying SCR rectfiers.
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Mar 20, 2011 23:58
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Couple of quick questions about DIY pcb manufacture. I'd like to start etching my own boards, hopefully double-sided SMD designs with either 0805 or 0603 minimum part footprints. I can't seem to find a comparison of various methods. I can handle building UV exposure boxes or bubble tanks but it's the chemical processes I'm worried about. I'm concerned about the environmental effects - I realise all methods will leave me with some copper sludge to dispose of but surely some are safer and less toxic than others? Is there a run-down anywhere of the various options with advantages/disadvantages?
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Mar 24, 2011 14:49
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Doing down to 0603 packages isn't too hard as long as you have a good light source, tweezers and some way of magnifying the work.
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Apr 15, 2011 16:24
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Seems as good as any.
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Apr 15, 2011 17:07
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Slanderer posted:The only reason anyone would use a LM741 in a "modern" design is because of one of the following: In fairness, you do also see them in some audio applications where specific distortion characteristics, limited bandwidths and slew rate effects are desired.
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Sep 15, 2011 15:57
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peepsalot posted:I just gotta say, these little chinese ebay Step down (buck, LM2596) and Step up (boost, LM2577) switching power supply modules are amazingly cheap and versatile. Have you used them? My experience buying this kind of stuff on eBay has varied from fantastic to awful...
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Mar 13, 2012 19:21
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ANIME AKBAR posted:I also got a pair of those smart LCR tweezers (the $300 ones, not the lovely chinese clones), and it's turned out to be a good purchase. It looses accuracy when you go below ~25pF/100nH, but it's still enough that I can easily identify unmarked SMD capacitors and inductors, which is the reason I got it. Keep in mind that's when I know that the components can only be a certain number of values (so if it says 980pF then I know it's a 1nF cap). I don't use it for actual quantitative measurements. For that I think you really do need a decent benchtop LCR. I bought the low-end Agilent Capacitance meter for work a while ago and I was able to get it with a set of SMD tweezers that can be used as meter probes. This might be a better option than smart tweezers if you already have a nice meter. http://uk.farnell.com/agilent-technologies/u1782a/smd-tweezers/dp/1710933
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Mar 23, 2012 19:20
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ANIME AKBAR posted:"oh, it's thermocouple effects." There is an internal Tektronix assembly document from the 60s floating around online that details the use of a certain type of solder with a lower Seebeck coefficient than the usual Lead-Tin when used with copper. They had to use dedicated irons with dedicated tips in a dedicated assembly area to prevent contamination. Crazy stuff. the wizards beard fucked around with this message at 00:16 on Jun 8, 2012 |
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Jun 8, 2012 00:03
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ANIME AKBAR posted:They're probably for an insertion detection switch, or redundant pins for +5V and ground. With pins that small they could be for strain relief, to stop the connector tearing off the board.
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Jul 22, 2012 20:01
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peepsalot posted:Has anyone messed with winding their own transformers? I've had this idea for a while of making a sort of "binary" variac. Instead of a wiper, there would be multiple output windings(maybe multiple input as well) with turns in powers of two, and some relays or something could dynamically reconfigure to provide various outputs levels. The low turn windings could be done in extra heavy gauge, and higher turns could be lighter gauge to give optimal power output over all voltage ranges. Do things like this already exist, is there a name for them? These type of transformers exist, but are expensive. They are used in benchtop linear power supplies. Different taps can be selected to provide different input voltages for the regulator depending on the desired output voltage, reducing the amount of power dissipated as heat in the pass devices. On some of the nicer Agilent power supplies you can hear the relays clicking as you turn the output voltage all the way up.
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Jan 4, 2013 03:17
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Parallel Paraplegic posted:Anyone have any tips or tricks for cutting perfboard? I tried to score it pretty deeply (first one side then both sides) and snap it in half on the edge of a table and it just flexed a little and refused to budge. I finally wound up using pliers to crack it off (which was very visceral and snapped in a weirdly disturbing way, like how I'd imagine spines would snap A little late, but I've had great luck with scoring both sides and then sticking it in a vice and bending until it snaps. I've also done this with copper-clad FR4, as long as you are reasonable accurate with scoring both sides in the same place it doesn't take much effort.
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Jan 21, 2013 17:21
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), and while it did crack right on the score I had made, half of the piece I was cracking off twisted and broke apart. I managed to save enough to still put my circuit on but it wasted more than I'd like since I had to throw some away. Do I need to score it even more (I think I scored it pretty drat deep but I could be misjudging) or should I just invest in a good Dremel tool? Any other ideas I missed?
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There's a really simple analysis tool that Bob Pease used to recommend - re-draw the circuit. That short wire looks odd but if you re-draw the circuit as a collection of parts joined together at nodes it becomes a lot easier to understand.
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Jan 27, 2013 14:38
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RS mostly, Farnell if I have to. I'll also use Mouser but it has to be a larger order to get the free shipping. IMO RS are usually a little cheaper, they have a warehouse near me and they charge 4euro for courier delivery.
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Aug 9, 2013 16:05
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This may not be correct for your setup but I've found it's nearly always much easier to leave them on the metal strip they come attached to until [i]after[\i] you crimp.
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Nov 6, 2013 22:15
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FWIW I bought a "Huakko" 936 on eBay and the iron was junk - the nut/thread securing the tip was stripped. I ended up buying another clone hand-piece (marked as Hakko 907) for about $7usd and swapped the connectors and now I'm happy with it. I got a nice iron for reasonably cheap but the fact that I needed a soldering iron to use my new soldering iron is kind of ridiculous. Also, check the mains wiring on anything you buy from China. Mine was OK but I ended up adding some insulation to a couple of exposed solder joints that worried me.
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Nov 27, 2013 16:54
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Base Emitter posted:Yes, you need an AC supply. DC won't work here. AC supplies are a lot less common unfortunately. 1.5A might be an overestimate and a 1300mA supply might work, but it'll be better to use the right supply. For cases like this I just order a transformer and put it in a small box. A 12V transformer rated at ~20VA shouldnt cost too much.
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Jan 25, 2015 23:08
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Buffis posted:Soldering IC's in DCK packages is the most bullshit. Are you doing reflow? A cheap hot air station and a syringe of paste can be had for ~60 euro and will do them in a few seconds (assuming you are not connecting small packages to enormous planes)
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Jul 8, 2015 17:37
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UberVexer posted:Not sure about the Bassman, but it's common to use the third pair of pins as a switch, with the ring. Most amps will use a switching jack to connect the input to ground, muting it until a cable is inserted.
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Oct 26, 2015 14:40
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asdf32 posted:More specifically, as large as a TO-220, so not a tiny surface mount one (size is the most important thing with heat). From memory I think I think it's around 30C/W for a 3-pin TO-220 to air. Going more conservative is probably better though
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Nov 17, 2015 10:09
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asdf32 posted:I don't think so. Double checking the highest wattage TO-220 mosfets on digikey turns up a bunch of 60C's IIRC it was on an appnote comparing different packages, I think free standing. A quick google doesn't turn it up though so I could be wrong. In these cases I would usually leave a pretty huge safety margin and then get some measurements of the outside of the package once it's built. e: found a local copy and google brought up the original http://cds.linear.com/docs/en/packaging/Linear_Technology_Thermal_Resistance_Table.pdf the wizards beard fucked around with this message at 09:22 on Nov 19, 2015 |
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Nov 19, 2015 09:18
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