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ben23

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Everything posted by ben23

  1. would the KEMO #M40 pre-amplifier module be ok to amplify a guitar output to line level so i can play my guitar thru a normal amplifier when I dont have access to a proper guitar amp. here is the link for it: http://www.jaycar.com.au/productView.asp?ID=AA0220&CATID=&keywords=amplifier&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID= and this is how i figured i should wire it, the guitar input being a 1/4" jack and the outputs being dual RCA's
  2. yeah a transistor type of switch would be good but i too have no idea how to make one, a transistor switch is a solid state relay basically. rating wouldnt need to be anything high, as the start up current is only momentary and very small (<200mA)
  3. yeah theres nuthing on the 5V rails, ill have to try that, i have a little 12v pilot light, ill measure the resistance and see if it will be ok, that way i can see if the PSU is on as well. there is an orange "power good" wire, should i ground that or power that or anything, maybe so the PSU thinks the "power's good" or is that so the MB knows that the power's stable if i used the 12+ and 12- rails instead of 12+ and ground would it get more power?
  4. ok first your going to need it to work like this phone rings - relay closes - computer starts up you hang up - relay opens - computer keeps on running to turn off phone rings - relay closes - computer begins to shut down (as long as you have configured the Power settings in Control Panel to do so) you hang up - relay opens - computer proceeds to shut down you observe to see whether you can access the computer anymore, if you cant, your successful, if you can, you need to ring, and let it ring until you lose connection, which will do the same thing as holding the button on the front of the c
  5. i have a old 220w computer psu, so old that its an AT, and was built in '94, im using it to power my 12w x 2 amp that usually is in my school bag with the speakers, but im sick of charging the battery all the time at home, so i rigged it up to this PSU, but i measured the voltage between 12v+ and ground, and i only had about 10.5, dropping to 10.4 when pushing it. with no load its at 10.6 should i just get a new PSU? or is there something I can do btw i hooked up the fan to the 12v supply but it couldnt be drawing that much, its only an 80mm fan. its a regulated switching supply (well i assum
  6. i actually recommend a 3PDT, so that way you can switch the grounds and isolate the other inputs ground to avoid interference and/or ground loops.
  7. basically PMPO is bullshit RMS is what u should be looking at
  8. yeah i think ive just had bad luck with the PSU's, that 5+5+3.3 sounds pretty good actually, nice work Ante, cos that gives 13.3 like u said, but its not voltage that worries me, admittedly, it wasnt a 300w now i think of it, it was actually a small mini-ATX 80w power supply, with 2.7A on the 12v rail, and it was a cheap CD/tuner how many amps can u pull with the 5+5+3.3 setup safely? would a 300w psu be enough to power a small BOSS CD/Radio head unit, that is probably about 4 x 35w - obviously theoretically it could run 2, but im making room for heat dissipation and that so yeah, was thinkin
  9. to put it simply, there needs to be a point of 0 volts i.e the neutral wire
  10. ok first of all, how much does the amplifier draw in amps (the fuse rating is a good indicator of what it is) or check how many watts the amp it is. then divide the wattage by 12, you will get the amperage draw (this would obviously be at maximum volume) second of all, once you have found that, u will need to see how many amps you can draw from the 12 volt rails of your power supply. the equation 600/12 = 50A would not be right, as that 600w counts for the 5 and 3.3 volt rails, which will not be used here. on most PSU's there is a label which will tell you the amperage of the 12v rails, and a
  11. what about using a hall-effect device, that could work, the ones used in car ignition systems
  12. yer that was my first idea but i dont want the added weight of a battery and inverter, rather just have the engine, induction motor (alternator) and capacitor bank and have it wired to a standard power point
  13. first of all, make sure of these few things - you have a quality power supply - your power cables are in good condition and are plugged in tight - you have a RCD = residual current device (safety switch) or a GFCI for americans whether it be at the switchboard of your house or as a plug adaptor DO NOT LOOK PAST THESE DEVICES THEY SAVE LIVES. - you have a reputable surge protector, as excessive surge current passing through a computer will do more than fry it, it will create excessive heat that can start a fire - you keep the computer clean of dust and all fans are working - you have good venti
  14. now i know i have the system thats in my school bag (the 12w x2), but i need one thats smaller, i have a small amp pcb from a pair of multimedia speakers. it has the usual tone and vol control pots on it, but, its made to run on 12v AC from the mains transformer, but right after where the power leads solder to the pcb, there are 4 diodes and a capacitor, me thinks that is a rectifier circuit. i tried running 12v DC (using the SLA battery from my bag system) into the amp and it sounded ok, but a bit distorted, if i tapped into the pcb AFTER the rectifier, and determined the polarity, it shou
  15. yeah i know what you mean, im not too fussed on SQ, it just has to relatively clear, not distorted and loud. Car speakers dont have a specific enclosure requirement, as they are usually mounted in car doors. i would use the box i have but the way i have built the bottom has been built around the existing speakers, plus im going to make the next one from scratch i use it at school to play music at lunchtime and that (got told by one teacher never to bring it again haha, but the rest love it, so f*** her!!! thanks ben
  16. any idea where to get a large capacity induction motor, do dryers have large induction motors?, single phase aircon would have a beefy one, if it wasnt hermetically sealed with the compressor
  17. in reply to audioguru, you say that my amps deliver less than specified, it does have a bit of high volume distortion, but it is quite a bit louder than 2.2 watts could make. my estimate about 4 watts per channel, without being optimistic in regards to the amplifier u had, what kind of inputs and speaker outs did you use, i was going to use banana plugs but thought it would be stupid, plus this had to be a budget amp, so i just used speaker spring terminals and they work fine! im going to make a smaller box and use 5" 2 way 4ohm car speakers, so that way i save space by not having a seperate
  18. ok, this is how i think a 12v to 240v (or 120v for the US) ac inverter works 12 volts goes into amplification circuit (solid state, and a DC-AC rectification circuit (multivibrator?) amplified and rectified current is "forced" into 12 - 0 - 12 to 120 or 240 v step up conventional or toroidal transformer. correct me if im wrong
  19. heres the full specs Modules: KEMO #M32 12W ampl modules x 2 Pot: 10k linear double gang Input: stereo RCA Output: Speaker wire spring terminals Battery Voltage: 12 - 13.5v DC Batt max amps: 2.2Ah Speakers: 4 3/4" Sharp woofers and 2" Sharp tweeters Impedance: Woofers 8 ohm, Tweeters 6 ohm. Box: Particle board, used to be an old speaker box, used to house one of the woofers and one of the tweeters. Other box was destroyed! Soon to come 5" 4 ohm 2 way car speakers I will get a pic of the enclosure soon they are in the same box but there is a divider between the 2 sets, so that way they ar
  20. yep thats the ones, any ideas on how to up the output, mind u its pretty good the way it is
  21. how do I use a standard 240v single phase ac motor driven by a petrol engine to create 240vac between the active (hot) and neutral wires of the motor? if i got a 2400w motor and drove it at the appropriate speed would it push out the full 10 amps that it would normally draw. (maximum capacity of australian powerpoints in the house, except for 15a air con / specialty sockets) is there any components i need to make it work and is there anything i need to watch out for? thanks ben
  22. Hey ppl I'm ben and finally built my first proper amplifier, which is just built into a plastic jiffy box, with a 10k double gang pot for vol and runs off of a 2.2Ah 12V SLA battery, the amplifier modules im using are made by KEMO in germany, i picked them up for AU$23.95 each here, all up the whole thing costed AU$107.38 to build including SLA battery (AU$24.95) and charger ($19.95) i have it in my school bag along with a wooden box containing 2 x 4 3/4 inch woofers and 2 x 2inch tweeters, i just hook my mp3 player up to the amp. it has RCA inputs, speaker spring terminal outputs. it sounds
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