The Forum » Music, Audio, Video, MP3 > Mixer and VU Meter
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Throwing together an idea for a two channel mixer for my PS3 - Headphone audio out on the ps3 only carries voice chat, so I'm looking to mix the PS3 output with the TV game audio. The headphones I'm lookign at come with a USB adaptor for the PS3, so everything's just 3.5mm stereo jacks. For the looks, I've built a VU (audio level) meter in as well for both left and right audio (design from Jaycar's Short Circuits book). Just wondering if anyone could spot any flaws in the overall design before I build it - I'm don't have much experience with audio. From the diagram, JP8 and JP9, and JP11 and JP12 are headers out to dual-gang 10K log potentiometers. JP1 leads to the power supply and switch (Pin 1 is 0V, Pin 2 9V, Pins 3 and 4 to switch). JP7 and JP10 are the audio inputs from the TV and PS3 respectively. JP6 is the headset output. JP4 and JP5 is just for the microphone because the leads on the headset won't be long enough, so an extension plugs into the unit to connect to the USB adaptor. Thanks guys Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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I'd prefer to stick with chassis-mount sockets. It means I can design the board to be as small as possible, which shaves off manufacturing costs. The current PCB will fit nicely inside a UB5 Jiffy Box, which isn't the most professional finish but it's hard to find good cases for a cheap price.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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I just tried fitting the PCB into a UB5 case and managed to find a few issues. Mainly, that 9V batteries take up a lot of space. So currently I'm trying to deide between a 9V standard (PP3) battery and a larger case, or running from an alternate supply - 6 AAA or AAAA cells or three CR2032 cells. I'm leaning towards the button cells, because AAA holders are about 1mm too long and wide, and AAAA are too hard and too expensive to source. CR2032 cells, while expensive, are readily available and very compact - only 4mm high + PCB thickness. EDIT: On second thoughs, I might make use of the parts forum for once. Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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The mixer section is completely unpowered because it doesn't have an amplifier, so the only thing the battery would be used for is the dancing displays. So at most, 20 LED's. And a coupel fo IC's to control them. Now I know 20 LED's is going to draw a bit of current, but I doubt it's going to drain a set of coin cells that fast. 9V batteries aren't known for their longevity in intensive devices anyway, that's why theres an explicit note in the Picaxe Manual not to regulate them down to 5V and to use three AAA batteries instead. However, how hard would it be to solder up and heatshrink together those AAA NiMH rechargeables from Jaycar with the solder tabs? How hard would that be to charge?============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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Yes, there is the option for a peak mode, and it's even built in already. Its clearer in the schematic, there's a jumper on each IC going to the supply. When it's bridged, the system operates in bar mode. When left floating it operates in dot mode. In hindsight, I could have designed it with only one jumper to control both channels. The original design was powered by a PP3 battery (typical 9V), which of course had half the current draw as it was mono. Reading the chips (LM3914/3915/3916, all esentially the same, 3915 is logarithmic though so best for audio level) datasheet, it appears to run on any voltage between 3V and 18V, and regulates the LED voltage and current to about 1.3V and 10mA. So no external current limiting resistors are necessary, with standard leds at least, and these values are stated across the entire 3-18V supply range. HOWEVER as the circuit was designed to run on 9V, the input circuitry (and especially the voltage dividers) may not function properly at a lower voltage. Or it might be fine, as it may be a reference to the supply as a ratio rather than a fixed voltage. Some breadboarding may be necessary... Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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Okay, found http://www.instructables.com/id/Battery-Powered-Portable-VU-Meter/. The interesting thing in the link is the discussion about battery voltage. The circuit is designed for 12V (four CR2032 cells, 3V each) but because he's forced them into two holders, and people don't always read, a few people have made the same circuit using only two cells putting out 6V... without any issues at all. The author even commented and said it would operate at 5V. So i'm guessing about 4 AAA NiMH batteries would probably do the job nicely, and if I need to change the resistor values on the pcb later to improve the output, well, thats not a problem because I only use part designations on the silkscreen to save space. Also, measuring up the UB5 case for vertical space, I get 25mm. 10mm is required for the potentiometers, probably 8-10mm for the PCB; with skill I might be able to have them cross over a little. So that leaves 5 to 8mm for the battery and it's case, which will be lid mounted (because the screw covers make good rubber feet, and they come with the case). I think AA's are out. AAA, probably fine. What is annoying is the debate over which chip to use. The LM3914, LM3915 and LM3916 all have the same pinout, but 3914 is linear, 3915 logarithmic, and 3916 monolithic (which looks like it's nonlinear, but a different curve to logartihmic). At about $8 a chip through NZ suppliers (and who wants to wait for international shipping for prototyping) that's not economically friendly. Futurelec across the ditch has them for about $3 each though, plus whatever ludicrious shipping charges they add on. Also, updated PCB, with the aforementioned hindsight considered. Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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Log Pot's are a must, thats for sure. Lithium Ion batteries would be sweet, if they put out enough voltage, and if they were easy to charge. Most Li -ion's for phones are around the 4V mark though and I don't really want to use two. I always test my PCB's on cardboard beforehand if I'm using parts for which I haven't previously checked the footprint for. This one doesn't really have any odd parts though, so other than checking the board size for mounting (the notches out of the corner are there to accomodate the standoffs built into the case for the lid), i probably won't bother. I will breadboard the circuit to test it because I want to order a PCB, not an expensive green coaster. I can probably do without the second capacitor (they're in parallel anyway), I only included two because that what the circuit spec called for. Might put in an order at futurlec for some parts. Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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I'm a Uni student, so a two week wait for futurelec (I've put in an order) isn't a big deal because I've always got an assignment or test to work on. In terms of shipping, this is what e14 states: "element14 offers free shipping for all orders placed via this website and for all orders placed via any other method over the value of $75.00." Now, can someone who's done an e14 order UNDER $75 tell me if they got charged for shipping, or if that only applies to non-web orders? My last order from them was over $75, so I got free shipping regardless. If it's free for all web orders, that's a really good setup.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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Awesome, thanks. Will keepthat in mind. Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.============================================================
Tom -------------- Need a hand? Flick me a message at nitronic755@gmail.com; I'm happy to help.
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