kendellrt Posted June 26, 2007 Posted June 26, 2007 I saved money building my own. I could never have purchased commercially what I have built for the price I spent on this rig. I don't think he can say the same.Even after reading this worklog of a DIY amp for the n00b, I could still never do it. I even have a degree in electronics with experience at the component level! Please don't blow yourself up! Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted June 26, 2007 Posted June 26, 2007 (edited) I saved money building my own. I could never have purchased commercially what I have built for the price I spent on this rig. I don't think he can say the same. Please don't blow yourself up! Oh, sorry. I mis-interpreted. You don't see the point to what I am doing All I will say is that it is not all about the money [for me]. If you don't understand that I would suggest, and I ask kindly, that you just completely ignore this thread. Edited June 26, 2007 by markiemrboo Share this post Link to post Share on other sites More sharing options...
Silverfox Posted June 26, 2007 Posted June 26, 2007 I saved money building my own. I could never have purchased commercially what I have built for the price I spent on this rig. I don't think he can say the same.Even after reading this worklog of a DIY amp for the n00b, I could still never do it. I even have a degree in electronics with experience at the component level! Please don't blow yourself up! You have a degree in electronics...but can't do this stuff? Are you s***ting me? Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted July 6, 2007 Posted July 6, 2007 I have updated the power button code... again. I was a bit slow in thinking, but yesterday I figured that instead of blinking a few times upon power on / off, I could actually make the power LED fade in and out by using PWM. I think it looks pretty cool. The video is deliberately dark so you can see the fade a bit better. http://youtube.com/watch?v=_qNGWH46OYQ The wood has been cut height wise and also sanded. Hopefully I will manage to get all of the panels cut out from these lengths of wood today, at some point! Share this post Link to post Share on other sites More sharing options...
Andrewr05 Posted July 6, 2007 Posted July 6, 2007 I have updated the power button code... again. I was a bit slow in thinking, but yesterday I figured that instead of blinking a few times upon power on / off, I could actually make the power LED fade in and out by using PWM. I think it looks pretty cool. The video is deliberately dark so you can see the fade a bit better. Looks good, but how about making the fade last a bit longer? I guess its "your" amp so its up to you, but I just thought it would look better with a slightly longer fade in fade out... Share this post Link to post Share on other sites More sharing options...
suchuwato Posted July 6, 2007 Posted July 6, 2007 Frickin' sweet. You though about getting a little circuit together that'll pulse it with a beat... that would be cool Share this post Link to post Share on other sites More sharing options...
jammin Posted July 6, 2007 Posted July 6, 2007 (edited) Frickin' sweet. You though about getting a little circuit together that'll pulse it with a beat... that would be cheesy There, fixed. Edited July 6, 2007 by jammin Share this post Link to post Share on other sites More sharing options...
suchuwato Posted July 6, 2007 Posted July 6, 2007 Frickin' sweet. You though about getting a little circuit together that'll pulse it with a beat... that would be cool laugh.gif Hey, that'd be neat... I think varying the intensity according to the audio pressure would be a good idea. You could even have it change colour when it's clipping or something. Yeah, that's not a bad idea Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted July 6, 2007 Posted July 6, 2007 I originally had the fade longer, though not intentionally. Code bugs It annoyed me a bit! Varying the intensity might be possible, but I doubt it's something I will be doing to be honest. Perhaps a VU meter one of these days. Changing the colour in the event of clipping is a big no no unfortunately, as the LED in the switch is green, and green only That would be a job for a separate LED really! Share this post Link to post Share on other sites More sharing options...
markiemrboo Posted July 25, 2007 Posted July 25, 2007 (edited) I haven't posted here in a while as I have been uber busy, so seeing as I have just now completely killed myself on the trampoline I have decided to take a break and post a rather large update. In short, I dont think the previous board is ever going to make it in to full time use. Why, you ask? Well... the 'jumper wires' started to annoy me. I know... petty reason. It's just how I am some times By jumper wires I mean the PCB was actually separated in to three separate stages before, and I had wires linking them together: Power filtering Regulator Amp I also decided to change the design and have three LM3886's per channel in parallel, and ditched the regulator and have a simple supply! I have decided to do this in order to drive pretty much the nastiest of 4 ohm loads at moderate power. In parallel the current capability is increased, as it is split in to each chip, and I *think* distortion may be lower too, from what I gather. It is the current handling that I really cared about though. Each chip is capable of a minimum of 7 amps, 11 amps typical, before it's current limiting protection kicks in. I would possibly be better off going discrete, but frankly I just aint that far in to understanding yet and paralleling these chips looks pretty darn simple! Some rough figures are as follows: An 8 ohm resistive load would need only about 3.75A peak. In reality a speaker is not pure resistance and is reactive. Lets say I was to use an 8 ohm speaker which dips down to 4 ohms (probably not that uncommon these days), this would then be 7.5A peak (at 30v). This is already cutting it a bit close to the limits of the chip. But then... apparently a speaker can appear as an even harder load, of up to 35%, on fast transients (aka music), which would mean about 10.7A peak for 8 ohms! Now share this between three chips and even the worst case 10.7A is "only" 3.5A, which is a fair way off the current limits. Even with the worst case 4 ohm speaker you would be looking at about 6.6A peak per chip (21A in total) at 30v, which is still just under the limits for the absolute minimum spec for the current limits of the chips. I then had to consider the power supply, as this is sort of the limiting factor now. I feel that the LM338 regulated supply probably wouldn't cut it (12A peak / 5A continuous from what I remember), and trying to regulate now really did just seem like too much hassle for me to bother. I'm just going with a very simple split rail supply, and with a 25VAC transformer I get about 37VDC here, which gives about 3v of headroom if I want to aim for 30v output, as the chips can only swing to the rails minus ~4v. With enough capacitance on the supply, and a big enough transformer, I think it should still be able to achieve this. I probably don't have enough capacitance at 20,000uF per rail..., 40,000uF in total, but I am sure I will live for now I'm not 100% sure about the rectifiers yet. There is space for two 8A rectifiers in parallel on each PCB, but I might go with two 35A rectifiers and bridge the connections on the PCBs. Who knows The circuit was simple enough. Good old national has an app note about bridging / paralleling the chips. The next task was redesigning a PCB. This was a show stopper for a while, as trying to design it on a single sided PCB was a bit of a pain and I just wasn't happy with it. I went looking for other PCBs for ideas, and pretty much the only DIY site I found was a double sided PCB. I drew out the power and ground fills as he has done, then went about routing the rest on my own and it turned out really pretty dang easy I must say! A single channel with three LM3886's and the two large 10,000uF caps all fit on 100x100mm, which is the perfect size. The heatsink is 200mm long, so I can still fit both channels on the single heatsink. It gets better: I found some copper clad boards, double sided, on ebay which were.... 100x100mm! No cutting required! I really hate cutting PCB's down to size. DIYing a double sided board at home sounded like it might still be a bit of a chore, but turned out to be reasonably easy. First I cut out the artwork, which I had 'alignment holes' on whilst drawing, and poked pin holes through the center of all of the alignment holes on both sides. Then I placed them on top of each other, so that the black trace sides were facing each other. I then poked pins through some holes, through both sheets, so that they were aligned and taped them together at the edges. I used ordinary 'selotape', as with the glossy paper I use it didn't rip it to shreds when removing the tape. You can check the alignment by shining a light through and looking at the traces. I then lined the now-single-sheet up with the PCB and taped it to the PCB. Either side is fine here, and it doesn't even have to be clean copper at this point. Drill through the alignment holes, which will then drill through the PCB. You now have alignment holes on both sheets and the PCB! You can now untape it all, clean the copper and iron on one of the sides, using the alignment holes to make sure that the top and bottom sides match Once one side is stuck quite firmly, you can clean the other side and iron that side on, again using the alignment holes. At this point both sides should be stuck in place and you can iron properly / for longer (about 5/6 minutes) until the toner is properly transferred. I flipped the PCB over a couple of times, but I would think that the heat would transfer to the other side anyway. Etch as normal. I can't drill straight to save my life, and I originally didn't think of aligning the holes using the pins. I just tried to shine a bright light through and tape together, hoping they were reasonably aligned and that I didn't move one of the sides by accident.... and I also left the stuck paper on the board before etching so the etching didn't go so well and it has turned out a tiny bit patchy, but even still it turned out pretty good for a first attempt / "prototype" Not all of the components are mounted, and they are not soldered at the minute... but that's all for now Edited July 25, 2007 by markiemrboo Share this post Link to post Share on other sites More sharing options...
GrandTheft Llama Posted July 25, 2007 Posted July 25, 2007 (edited) I just stumbled on this thread and spent like 30 minutes reading lol, amazing stuff man that looks darn near professional keep it up Edited July 25, 2007 by GrandTheft Llama Share this post Link to post Share on other sites More sharing options...
Bleeble Posted July 25, 2007 Posted July 25, 2007 Very impressive. This just makes me feel stupid for not even attempting a CMOY amp. This amp is being used to power speakers, correct? Share this post Link to post Share on other sites More sharing options...
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