how to reduce the ac voltage? from a mix signal?

Suppose that there is a mix signal (with 60vdc+110vrms). now i want to completely block the dc component (OBVIOUSLY I NEED A CAPACITOR BUT)what should be the specifications* of the capacitor. and if i want to reduce the the dc component to 15v then what should be the specification of the capacitor. ALSO            i need the complete calculation/procedure required to find each of the value of the capacitor. *by specification i mean 1- capacitance 2- voltage rating 3- type (ceramic/electrolytic etc)

Question by UmerJavaid   |  last reply


How to combine 2 audio signals from HDMI

As I've known so far there aren't receivers that mix audio.I want to mix 2 HDMI sources, lets say 1 is a PS4 and second is Xbox One, how would I mix them in 7.1? Mix the 2 audio sources into 1, is there a way of doing that? What is the simplest way.I know that there are stereo mixers, but haven't heard of a HDMI one.What is the simplest way of mixing both signals?I think it might have something to do with modulating the signals, but I dont specifically know how modulators work.

Topic by MatanY2   |  last reply


how to combile outouts ? Answered

Hello, i made a LittleGem and a LittleGemMK2 .But i only have one speaker, is there a way to make speaker play 2 signal from 2 input at a time ?? Thanks ! sorry for my bad English.

Question by login721   |  last reply


Feeding samick guitar signal and mp3 into guitar input of samick amplifier.?

Hi, My wife is an amateur musician she has a samick amp with two inputs mic, and guitar, we are trying to input a mix of sounds into the guitar input. I have tried a connection from the headphone socket of mp3 player, in a double adaptor config with guitar, this is not ideal, due to the  unbalanced signals, and there is a loud hum.  What can I do short of buying another amp. Also I don't know what the impedances are but suspect the mp3 player is 8-16, and the amp input much higher. I am wondering whether a simple mixer might help, but I don't know how impedance might affect this, or whether it would actually work. Thanks for any comment

Question by valter2au   |  last reply


Do I need to invert phase a second time? Answered

I'm building a guitar pedal and I am inverting phase with the initial buffer (TL072). I am then splitting the signal into two parts, dry (no effect) and wet (effect). Each of these will be output as separate channels (left and right) and not mixed back to mono. I plan to send each channel through its own 386 amplifier chip to boost it to a level suitable for headphones. So, what I am wondering, is, should I use the 386 to invert the phase a second time back to normal? Or should I use an op amp at unity gain to do that before I send it to the 386? Or does it not matter if I am not mixing the two signals back to mono?

Question by randofo   |  last reply


Active mixer and 180 degrees out of phase question? Answered

Hello , i want to make a simple active mixer to place in front of the power amp. I read some documents about active op-amp mixer.And they said : "Any signal entering the inverting input of the op-amp will appear at the output but it will be 180 degrees out of phase.If the output of the first op-amp were recombined with one of the other signals at a later stage it would cancel out rather than mix. So we have to re-invert the phase with yet another op-amp." and the schematic should like figure 1 to re-invert the signal . But if i use the the mixer to direct feed input of power amp , can i use the schematic like figure 2(w/o re-invert the signal) ??? Thanks in advance! Sorry for my bad English!

Question by login721   |  last reply


tech noob question on stereo jack

Can I have a silly technical question for which I would have known the answer if I only paid more attention at school? how is possible that stereo headphones, ie 2 speaker circuits use only 3 cables? I understand the "ground" is the one that both speakers,ie left and right have in common but how come it doesnt bother the signals which go to the speakers? doesnt the left signal get mixed up with the right signal? and why is it called "ground" when it's not actually connected to the ground, like for example lightning conductor is? I've read through the wikipedia article about TRS several times but still can't understand it. thanks for answer, I promis I won't forget it this time :)

Topic by tap   |  last reply


Will he think I'm a creepy international stalker?!

There's a guy I like, and we have a weird chemistry, but I don't know what's going on with us if anything. Will he freak out if I send him a text message saying I miss him? (I'm currently in a different country)

Question by    |  last reply


how to reduce noises of engine from bus amplifier system?

Hi all, I am designing an amplifier system for a bus which is serving all passengers like DAEWOO BUS at a time. this system is working good in normal case. but when driver accelerates, the sound of engine is mixed up with audio signal and causes a noise. I don't know how to remove this noises from my amplifier system. One thing to know that a common amplifier TV, and  mp3 player is used to amplify audio signals and next individual passenger will be served his headphone/ handsfree as individual headphone jack adjacent to his seat. Also all headphone with all seats are connected in parallel. I will be thankful if someone help me out in this problem.

Question by abdulrazzaq   |  last reply


Passive mixers, I don't undertand why the resistor/capacitor

Hi, when I was young, our teacher show us a passive mixer, each input had only one green capacitor in series for each input, it was not electrolytic but ceramic or polyester, it sounded so good for just being there 1 simple component per channel. Now taking a look at google, can see that the most passive mixers, uses resistors to isolate sources, with values since 10k to even 100K. Other schematics shows a resistor and capacitor in series (see image below) what does that capacitor? and why some schematics only has a simple resistor? is it easy to calculate its ohm value?. Is it better using this configuration supposing that the source is weak (coming from cellphone 3.5 mini jack or RCA) and this mixer targets the signals to a pre amp? So I need to from weak sources like iphone, dvd, any RCA output, etc... anybody know whats the best to use in this case? Thanks so much. Should I put a resistor as minimum as possible? I undertstand that a resistor there, in the input, will reduce the volume input, and I dont want to do that, so can I simple connect everything direct? or the resistor isolates the inputs, otherwise it will sound ugly? I am very confused, why the resistor? why I have seen resistors from some ohms to 2km and even a lot more, 50k, 100k. I want to mix two weak sources, as a signal coming from a walkman and cd player, or cell phone, etc, so whats the law for not reduce signal intensity and mix everything well? all channels will come in into a pre amp IC.

Topic by destrip   |  last reply


Wiring 2 pots together?

Ok, so I am in the hobby of hobby grade rc. I am currently working on modding a ps2 racing wheel and foot pedals to work with a spare 2.4ghz remote I have for my cars. I got the steering wired up fine and it works good. Now for the somewhat tricky part. The foot pedals each have a potentiometer in them. They share ground and power, and have separate signal outputs. I have the right one wired in for the throttle just fine. On my micro car it was easy enough, just switch the throttle reverse switch and push the pedal and it goes in reverse. But most escs wont calibrate to that. How would I go about wiring them together? essentially I want to turn 2 pots into one big pot. So when I push the right one down it sends the signal for forward. When I take off the right one and push the left one down, it signals reverse. I could bring my micro controller into the mix, but I really dont want to for something that seems so simple. Plus it is on a serb right now. Any help?  Thanks

Question by TOCO   |  last reply


Arduino Uno Synth project - Audio output questions

Hi! I am developing a synth/sampler project based on the Arduino Uno r3. This is my first electronics project ever and because of that reason I have some questions which I can't find a definite answer for on internet. The synth has two function. It has a tone generator using the ToneAC library. With code I have mimicked LFO and VCO functions, using potmeters I can adjust the frequency and LFO speed realtime. The other function is that I can trigger samples stored on a SD card using the TMRpcm library. The device will be used in nightclubs on high end soundsystems and PA. I am afraid I will damage the equipment with my device because I do not send a pure audio (AC?) signal. Currently the flow is like this: PWM output (pin 9, 10) -> voltage divider to 2.5v -> RC Low Pass Filter 15Khz -> LM386 amp with volume control -> mono jack output -> mixing desk -> amplifier -> speakers (the TMRpcm and ToneAC library share the same pin (9), I have fixed this by disabling the TMRpcm when the ToneAC is playing and vice versa. The mono jack is wired as follow. pin 9 goes to plus side of mono jack output, pin 10 to negative side. The TMRpcm pin 9 also needs to go to plus side of mono jack output, and mono jack negative needs to go to ground. Because I disable the ToneAC at that time I consider port 10 grounded because it not generating any sound so there is no signal/voltage running out of it, aka the IO pin is set to LOW) I am hoping that using the voltage divider I am within range of the Audio Line levels of a default mixers Line-IN (like Pioneer, Behringer, etc). The RC Low Pass Filter is used to filter of inaudible frequencies and clean up the sound a bit, the LM386 audio amp is used to amplify the signal and (hopefully) make it a real audio signal. The lowest frequency you can play with the synth is 100hz and the highest frequency is 3100hz. Because I lack a lot of knowledge in this field and because I do not own a oscilloscoop I can't say for sure if my output signal is harmful for the equipment and was hoping to get some guidance on my project on this forum.

Topic by erik404 


Tracing Plastic Water Pipe Underground.

Earlier today, while removing tree stumps, on of my crew struck water. The theme song for the Beverly Hillbillies came up. "when up from the ground came a bubbling crude! ...oil, that is... " except it was water, and we went scrambling to find the water shutoff. Lawn Sprinkler systems usually have plastic pipe a few inches underground.  No metal.   :.   Can't find it with metal detector. Potential Options: AC wires can be tracked through walls by the electromagnetic flux around them. Stud sensors today also have a circuit for AC wiring. Could something like that be used?  Although city water has some minerals in it, does it have enough to conduct electricity well enough for an electric pulse sensor? If the water in the system was temporarily made salty enough for an EM signal to be traced, would it mess up the lawn once you dumped that salty h2o? Whata bout conductivity of a fertilizer mix? Medical scans- barium- mildly radioactive. mmmm.... yeah. right. Chemical sniffers- sniff out those semi-soft pipes? Like dogs sniffing out contraband in the airport... Use water flow to carry a fine wire through the pipe, then track an EM signal in that wire. sonic imaging (or at least detection- like the stud sensor) ground penetrating radar... That's all I can think of.  Every option I can think of has issues. Is there any precedent for something that works in this situation?

Topic by Toga_Dan   |  last reply


I need help designing a portable powered audio mixer.

 As the title states I need some help in designing a mixer that I am going to use for home recording and on stage to EQ my drum kit. I feel I will be able to actually build the thing and have a rough idea of a schematic but my depth of knowledge ends when it comes to powering the mixer and exactly what parts I will need in terms of resistors, pots and power supply. The unit will act as a pre-amp, mixer and EQ. I want a total of 12 inputs and 5 outputs.  This breaks done as... 1 headphone out 3 Grouped outputs  1 Main output Each channel will have 1 bass, 1 treble, 1 volume and a selector to chose whether the signal is routed to the grouped output or the all-out output. I could really do with some help designing this. Thanks in advance! el Ginjo,,

Topic by el Ginjo,, 


convert any CRT TV or monitor into a vector (XY) monitor?

NOTE: I since found a couple links that might shed some light on the question... From HackIt: New uses for old CRT monitors http://hackaday.com/2008/02/25/hackit-new-uses-for-old-crt-monitors/ It would be very hard to do, but it is possible a CRT could be converted to a vector monitor. Perfect for playing Asteroids, perhaps under MAME. You would have to replace all the control circuits, probably with an FPGA and three ADCs (x/y/intensity). Posted at 8:58 am on Feb 25th, 2008 by MoJo Television and PC monitor experiments http://www.educypedia.be/electronics/televisionexperiments.htm old cga/vga monitor to oscilloscope ? http://www.edaboard.com/ftopic57853.html The inquiry: Maybe I am over-simplifying but I was reading one of those examples of hacking into a CRT's horizontal & vertical yoke controls to sync to music:     http://geektechnique.org/projectlab/707/how-to-make-mac-se30-audio-visualizers and had the idea that it should be possible to create a DIY XY monitor (vector display like on an oscilloscope, Vectrex, Asteroids, etc.) for an Arduino or other uC, MAME or Vectrex emulator, from any TV or CRT, once you have hacked into the electron gun's yokes. My understanding being: Raster display: the horizontal yoke (an electromagnet) sweeps the electron gun from left to right turning on the beam wherever there's a "pixel" at that line (which lights up the phosphor at that point making it visible), then it starts over at the next line (vertical yoke moves down) and draws the next line, and so on, Vector display: instead of rendering a moving image frame-by-frame using top to bottom/left to right scanning, shapes are drawn directly to the screen by positioning the horizontal & vertical yokes at the starting point, the beam turns on, and the yokes repoint to the end point, thus "drawing" the line inbetween the 2 points (I would assume this is for straight lines, not sure if circles or arcs are possible?) then the beam turns off, and the yokes get re-positioned to the next line's starting point. I'm not sure what turns the beam on & off or what kind of timing might be involved, obviously that needs to be controlled somehow. Or for color, where instead of a single white (or green, amber, etc) phosphor exists per pixel, there are multiple (red, green, blue) per pixel, and the beam hits each one at varying strengths (or for a varying length of time?) to 'mix" the primaries to the desired color? I'm not sure how that gets handled in a color vector monitor, but I would assume it's something similar to raster? So if we can hack into a CRT's X/Y yokes and move them around with an audio signal, can we control the yokes more deliberately from a microcontroller to plot specific shapes or text, hence a vector display? For those audio/TV hacks, what is the audio signal doing to the yokes that causes them to move? Whatever it is - voltage, resistance, etc - this is what our device would have to control. Possible proof of concept version: make a device to control the yokes' position etch-a-sketch style with a couple of potentiometers, and turn on the beam with a switch or button. If you see a dot of light moving across the screen then it works. I am thinking the controller might need to be "calibrated" for the individual CRT? (Maybe build some kind of calibration mode into the device.) You might dedicate a microcontroller to driving the display - it could receive text or vector shape coordinates via serial, store the shapes to draw in its own memory, and persist or refresh the image independently, freeing up processing power for whatever device it's displaying for. Another idea would be maybe add some kind of way to read light pen's coordinates, thus making the CRT an input device that can be read from the microcontroller or PC (the Vectrex had a light pen right?)  [This would be a cool mod for the Arduino composite TVout as well.] So is this idea possible without a ridiculous amount of work & parts?  I may be dead wrong about how this stuff works (I'm sure that if this was possible, someone would have done it by now?) but figured it can't hurt** to put the idea out there. I have visions of 4-player vector Arduino pong, Asteroids, Tempest, PDP-1 Spacewar!, vector NES Duck Hunt, a vector etch-a-sketch or lightpen drawing or animation program, or vector Atari Video Music. Possibly an open source color vector games system. Or just a vector display system for any Arduino or microcontroller project, made from any TV. **WARNING: maybe it CAN hurt... Evidently hacking into any CRT can be deadly, you have to discharge the CRT and capacitors properly or you can get killed. So please be careful. This definitely is NOT for kids to try at home.

Question by apple-o   |  last reply