Questions tagged [audio]

Questions about designing electronics for measuring, processing, and amplifying audio signals.

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17
votes
5answers
62k views

Simple Audio amplifier Using Transistors

I would like to build a simple audio amplifier using transistors. I know there are IC designs specifically for the task. But i want to use transistors so i can learn how to use them for amplification. ...
4
votes
2answers
4k views

What Voltage/Current Levels Can I Send Into the Microphone Input on a Mobile Phone?

I have a device that is sending 9600baud using only Tx, Rx, and Gnd. I am not sure, but I think the voltage is either the 3v or 5v level. I want to receive that serial data on my mobile phone. I ...
3
votes
3answers
2k views

How do I make this LED flasher more sensitive?

I'm making a circuit which will change brightness level of an LED in tune with music. So far, this is producing some results, but I'm not very satisfied with it: If it matters, the forward voltage of ...
4
votes
2answers
5k views

Digital input to mobile phone headset port?

This seems to be a common smartphone project, but I haven't seen circuit diagrams with explanations. What filter network (or resistor network, or other buffering circuitry) should be used to connect ...
0
votes
2answers
513 views

Connect IPOD audio output to old rotary telephone

I hope you could help me. I want to connect the audio output of an IPOD to an old rotary telephone. The telephone is not connected to the telephone line, it's just a fancy design thing I would like to ...
8
votes
2answers
1k views

Using the audio input port as a voltmeter

I'm a physics undergraduate currently studying electromagnetism. I have no experience at all with playing with electronics. I'm trying to see the effect of a changing magnetic field on a closed ...
5
votes
2answers
853 views

Not able to get ac97 audio output from Atlys board

I am trying to get audio output from Atlys board (uses LM4550 audio codec). I got the ac97_controller.v core file which generates the serial o/p for the codec. It takes slots as inputs and puts them ...
6
votes
2answers
6k views

Multiple Ultrasonic Rangefinder Question

I've been doing some research on ultrasonic range finders as sensors for robotics. I've seen them being attached to servos and pivoted to effectively "look" in front of the robot and make sure the ...
4
votes
2answers
236 views

Handling audio (from mic to headphones)

Right, I'm new to electronics, but this is what want to know: What do I need to take a mic input, and output it to some ear phones (standard jack, can be mono). I want to build a motorcycle intercom, ...
10
votes
1answer
3k views

Reducing noise in audio circuit (optical pickup + op amp)

I am building an optical pickup using a photodiode connected to a LM741 op-amp. My circuit is similar to this one: Except that I've added a passive high-pass filter after the output of the op-amp, to ...
1
vote
3answers
9k views

Tiny speakers, used in headphones - what are these called?

After having searched Mouser and a general search for "tiny speaker", "small speaker", "headphone speaker", and not having found what I am looking for, wanted to see if someone here can help me find ...
0
votes
3answers
1k views

Any way to identify “directionality” of electret microphones?

Picked up a handful of electret microphones from a local component store, and store owner claims them to be generic. He calls all components generic for which there is no data-sheet or specific part ...
6
votes
4answers
11k views

Avoiding echo/feedback on speaker-phones, how?

Even a $20 mobile phone with a speakerphone has no problems of feedback. While I understand that companies like Mediatek have use crazy volumes to bring down mobile chipset prices so low, but reading ...
7
votes
3answers
23k views

How to make my own volume control for headphones?

I have headphones that don't have volume control built in on the cable, so I thought why wouldn't I try to make one? However, I don't know where to start. Is it enough to just use a logarithmic ...
3
votes
1answer
447 views

Good way to pick up voices in a small room for speech recognition

I've written an app that's pseudo-intelligent and responds to voice commands. I'd like it to be able to pick up my speech from anywhere (initially just one room, but possibly many later on). At ...
1
vote
1answer
309 views

How is it possible to feed the output signal back to input using a TRRS connector

I want to be able to "play" the output signal back to the device (in my case an XPERIA X10 which i think uses a standard TRRS plug) so that everything that is output by the device comes back to it. ...
3
votes
5answers
5k views

Why are audio transformers required?

I was looking at simple AM radio schematics and came across this one: As you can see it has an audio transformer. I'm still attempting to grasp the concept of impedance and such, so can someone ...
1
vote
2answers
164 views

Will this setup create much audio interference for me?

I'll be installing a ipod adapter kit in my 2004 honda accord, and on the device that connects to my stereo, it includes stereo outputs - red/white - that i can connect with a stereo to 3.5mm cable to ...
1
vote
4answers
16k views

what is the color code of cables in earphones?

What I see after stripping the cable is this: copper-red and yellow on right channel green and stripped red-gren on left Whose are for ground and whose for signal ? (edit: I'm asking this for ep-...
-5
votes
2answers
206 views

Regarding negative feedback [closed]

What happens if we give some resistance directly to the input signal instead of giving some part of output resistance back (i.e., negative feedback) ?
0
votes
2answers
213 views

Cheap visual indicator for a PA loudspeaker line

I have a PA system which is outputting at most 200Vrms AC peak, around 100Vrms AC nominal, from the transformer. The current is around 4Arms. Since the system is comprised of 12 output transformers, ...
0
votes
2answers
4k views

Cleaning up noisy audio signal

Can you give a circuit that would clean up noisy audio signal? Basically, I have created a square wave from a software (Real Time Analyzer) at certain frequency to the audio jack port of the computer....
2
votes
2answers
773 views

Circuit to exaggerate differences in current

Basically what I am after is some sort of a circuit which will amplify higher voltage signals, but possibly dampen lower voltage signals, in order to make a wider separation between high and low ...
2
votes
1answer
3k views

Help with PTT circuit for icom radio

I'm trying to set up an APRS station using an old icom HT. Receiving is fine, but I'm having some trouble with the transmission side. When I connect all my parts together, the transmit light ...
2
votes
3answers
2k views

Simple, passive way to remove high frequency interference from low power audio

I have used the innards of a Korg Mini-KAOSS Pad to add some amusing effects to one of my electric guitars, but in order to do this I had to remove the original input connectors and wire my pickups ...
2
votes
2answers
215 views

Low voltage 2 channel stereo analog switch

I am looking for a ultra low voltage 2 ch stereo analog switch. I have two headphone audio sources that I need to switch between. It is very important that the chip can run of a 1.2v rechargeable cell ...
5
votes
2answers
3k views

Reducing noise in elementary audio circuit

I wish to hook up the line-out from a digital piano to a surplus 4 ohm 15w speaker unit. I bought a simple Amplifier module and connected it up. My plan was to roughly assemble the circuit and, if it ...
3
votes
5answers
15k views

How to create a simple audioplayer-device for a single soundeffect

How can you create an audio player device which can play a single sound effect when a button is pressed? A button and the speaker should not be the problem, but the tricky part is, what I have to do ...
2
votes
4answers
200 views

What kind of chip can a person download sound from PC into

What kind of chip or device can you use to download 1 minute of music or sound from your PC into it and this same chip or device will sound what you downloaded into it when connected to a small micro ...
6
votes
1answer
6k views

How do I shield my pc-speakers from mobile interference? [closed]

I have a budget (not cheap :P) pc-speaker set from Logitech (2.1) at home which are extremely sensitive to cellsignal interference. My iPhone is about 1m from any part of the set - including the ...
5
votes
1answer
6k views

Is there any way to feed a signal (line-in) into a mobile phone?

My first post here, so please point out if I say anything silly. I'm working on an audio application for mobile phones. At this point in time I'm trying to measure audio latency of a mobile device by ...
12
votes
3answers
8k views

Audio Amplifier PCB Design Tips

I am going to design a stereo audio amplifier with TDA2030A. This is going to be an amplifier that is going to be powered from 27.6V DC and 12W per channel. Is there any sources that I can learn PCB ...
1
vote
3answers
3k views

Broken headset, repaired, but microphone doesn't work on computer, does work on phone

I have a headset for my desktop computer. It's an analog device with two 3.5mm jacks, one for the headset, one for the microphone. It also has inline volume and microphone toggling. By wire was ...
1
vote
1answer
8k views

Audio: 2 Speakers * 200 Watt versus 1 Speaker * 400 Watt?

What is the difference between 1 speaker of 400 watt and 2 speakers of 200 watt? All the speakers are 12 inch. Of course, I know the difference is mono/stereo. But I want to play in a little band ...
10
votes
2answers
10k views

How do those 3.5mm stereo to mono adapters work?

I have one of those 3.5mm Female Mini-phone mono to Mini-phone stereo which I was hoping to use for connecting the output of an MP3 player (stereo) to a pillow speaker (mono). But then it occurred to ...
3
votes
1answer
958 views

Data modulation over Bluetooth headset profile?

What kind of data modulation schemes might be suitable for sending data to/from a Bluetooth audio headset? e.g. What kind of data modulation would likely survive the audio compression schemes and ...
12
votes
2answers
7k views

Twin-T Active Notch Filter Analysis

Could anyone give me a hint in analyzing the Twin-T Active Notch Filter? I tried a delta-star transform, followed by nodal analysis, but ended up with conflicting equations. For an example, look at ...
1
vote
5answers
7k views

Differentiate between clapping and talking

I brought a clap activated switch project to practise my soldering. I realised clap activated was really sound activated. Is there a way I can get it to be able to tell the difference between me ...
1
vote
1answer
130 views

Typical (cell-phone quality) audio modules and formats

My question is twofold :-) What are typical audio modules that I can use in a lo-fi electrical application to playback some simple music (of about 1 minute)? Think of cellphone speaker quality. What ...
2
votes
2answers
2k views

How can I actuate a relay coil from a headphone jack's internal SPDT?

I want to plug my iPod which in turn supplies power to an external audio amp while sending iPod audio signal to same amp. Is it possible to wire an 1/8" (3.5mm, mini) stereo jack in such a way that ...
1
vote
1answer
6k views

How to wire sennheiser headphones to an iphone headphone cable

I have a pair of these (or something very similar) : The plug failed so I chopped it off and was hoping to wire it to a plug on a spare pair of iPhone headphones I had kicking around. Both sets of ...
3
votes
2answers
3k views

Simple VU meter with Lm3915

I'm making a VU meter with an LM3915 and I would like to be able to plug my computers audio output into the LM3915 directly and get it to register. I've been searching the internet for a design but ...
3
votes
2answers
444 views

Why is the LED attached to pin 10 on and how can I get it to turn off

Here is the schematic that I'm working with: http://www.circuitsonline.net/schakelingen/59/audio/led-vu-meter.html The LED attached to pin 10 is always on. Is there anyway I could get this so that ...
3
votes
1answer
7k views

How could you detect a microphone attached to a smartphone?

I've a circuit that makes sounds through an a standard audio jack (3.5mm) and I would like to connect it to a smartphone (let's say iPhone). When I connect it to an iPhone, it will be detected as ...
2
votes
2answers
1k views

Is there anything better that a SSR when working with audio signals?

I'm using the output of an op amp (LM308) with a low pass filter (R=4700Ohm C= .01 uF if that helps) to control a SSR (D2w203F) which is controlling a string of Christmas lights. I was wondering if ...
3
votes
2answers
4k views

How to make LED bar graphs to measure intensity

I'm working with this design. I would like to make those LEDs into LED bar graphs that will show the intensity. For example, I want a song with a loud base to make the bar graph shoot up to the top. ...
5
votes
3answers
10k views

Ground loop? Switch mode power supply noise

I have a single 12V supply powering a 12V class D audio amplifier (Tripath TA2020 based, model 'SMSL SA-36') (C) and a very cheap 12V to 5V 2A rated switch mode converter (A). The 5V is used to power ...
8
votes
3answers
3k views

HUGE capacitor recommended in datasheet for Audio Amp

I'm using the TPA3111 audio amplifier in a circuit of mine and I'm working on adding the appropriate capacitors. However, on page 18/19 of the datasheet TI recommends to use a 220mF capacitor on the ...
1
vote
2answers
2k views

Can I replace MC33204P with one of these other op amps?

I'm working to make this schematic and I was wondering if it is possible to swap out the MC33204p with either LM348N or LM339AN. And if you could let me know why swapping them would still work I'd be ...
3
votes
1answer
465 views

Binary Counter and an Oscillator for frequency generation

I'm interested in creating low frequencies using a high-frequency oscillator. For example - using a 12Mhz oscillator to create 1Khz, 2Khz waves. I've been said that using a Binary adder(oops) counter ...