Questions tagged [audio]

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

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64 views

Identify components in an audio circuit schematic

In the attached image you can see a circuit part of a commercial audio amplifier. I'm trying to determine what kind of component is R-CH and what role it plays in ...
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46 views

ESP-07S / ESP8266 I2S audio interface with audio codec IC (audio input + output mono)

I have never dealt with digital audio interface like I2S. I want to use ESP-07S / ESP8266 audio interfaces as digital audio I/O (for mic + speaker). ESP-07 has two I2S interfaces: 3-wire audio input ...
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47 views

BJT reverse base-emitter voltage 1 Volts?

Using the multimeter diode setting in a powered down circuit, on the TR6 transistor (BC548), the forward B-E and B-C voltages are ~0.7 V, reverse B-C is OL but reverse B-E is 1.08V. Does this mean the ...
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53 views

Speaker and player on same 5V charger crackles but not with two separate chargers

I am using a Samsung mobile phone connected to an external speaker (connected via a standard audio cable with jack connectors). Audio is playing fine when I use two Samsung-branded 5V-DC chargers, ...
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1answer
63 views

Measuring BJT voltages in circuit?

Using a multimeter's diode setting I see that both the base-emitter and base-collector voltages of a transistor in a powered down circuit are 0.67Vm, while reversing the probes shows OL. Voltage ...
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1answer
66 views

Sony TA-1630 baffling me [closed]

I'm new to this forum. I have a TA-1630 that is truly baffling me. I know that some of you have had experience of this amplifier or a similar model, and wondering if you can offer some experience/...
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2answers
52 views

Protecting an ADC from negative voltage: Is it better use diodes OR to offset voltage?

I'm working on a simple guitar amplifier and reader with Arduino. The Arduino will use this input to find the amplitude and frequency of the input signal. I'm getting confused about how the ADC ...
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1answer
58 views

How can I calculate low and high frequency in my circuit?

How can I calculate low and high frequency in my circuit? I have used an 8-ohm speaker.
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1answer
43 views

Protect MOSFET gates in audio amplifier

I've made an amplifier from a circuit I found on the internet (below, link). I made it more or less exactly as described (same components, big heat sinks) and it seems to work great (can run at a loud ...
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1answer
87 views

Cathode bypass capacitor value in a Fender 5F1 Champ-style amplifier

I am building a 5F1 Champ-style amplifier and I am wondering about what value of capacitor to strap to the cathode resistor? I have seen suggestions of 22 uF and 25 uF and I am not sure what value I ...
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51 views

Characterising an Audio Isolation Transformer

Rummaging around the junkbox in an effort to find a 600:600 ohm audio isolation transformer, I found a possible candidate rescued from a store closure some time back. It's basically a cheap, low ...
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19 views

Accelerometer signal to audio signal

I have a accelerometer (ILS - MPU9250) and a woojer vest. The woojer vest is a device that shakes based on audio input. (simple line in with jack) What I would like to do, is to put this ...
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428 views

My BJT audio amplifier circuit isn't working as expected

I am trying to design an audio amplifier circuit using BJTs. These are the requirements of the circuit: Input signal: 50-100 mV (It's the output of my iphone's microphone) 2 W - 4 ohms speaker There ...
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1answer
89 views

Wien Bridge Oscillator using OpAmp(LM386) works in simulation, but doesn't work in Breadboard?

This is a simulation of the circuit in multisim. It is a Wien bridge oscillator circuit, tuned at 1844Hz. I am mostly interested in generating sound of that frequency. It seems to work here in ...
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1answer
109 views

Trying to control vintage amplifier (TEAC A-H500) with Raspberry Pi - what's the communication protocol? 8-bit bus?

I'm trying to control my vintage amplifier from Raspberry Pi - I want to create a nice little Spotify streamer that on playback start will automatically turn on the amplifier and set the input ...
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37 views

Common ground for subwoofer-out

I have a Sony Sony DSX-A110u which is a car stereo having 4*55W Speaker out and a Sub-woofer out. The subwoofer-out port it a female RCA jack. which looks like this - I am using the sub-woofer out ...
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2answers
106 views

Is a 2N3906 an appropriate replacement for a BC158(B) in audio amp circuit?

On a long but educational process repairing a vintage German stereo. I have identified a failed (shorted) PNP transistor in the power amp section. (Schematic with highlight is below.) The part on the ...
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2answers
83 views

MOSFET based audio switch generates thumping sound

I need to switch on and off an audio signal without clicking or thumping. I have tried the below circuit that I designed and simulated in LTspice, but it generates a thumping sound when I wire it up ...
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131 views

Audio: Digital Potentiometer is Noisy Compared to Analog Potentiometer

I am building an A/V switch that I would like to have a headphone output with adjustable volume, controlled by a microcontroller. As a test, I connected an audio source to a potentiometer (input to a, ...
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1answer
79 views

'true' balanced audio?

I was working on the below circuit, to create a balanced audio output. But have been told this creates a differential audio output, not a 'true' balanced audio output. "A true balanced output would ...
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39 views

PLL for Audio Frequency VCO using R divider

I'm attempting to design a PLL for an analog, audio frequency VCO, but I've run into a conceptual problem. I can't reasonably use a divider in the feedback path. My reference frequency would ...
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2answers
157 views

Trying to understand this Class D amp (using IR2113) circuit

I understand the concept of the Class D amp and this circuit, but in this particular case there is one part I just don't get. What I don't understand is how the low side of the signal should work at ...
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44 views

Mixing Symfonisk high/low-mid output channels

So i've been messing with this issue for a couple of months and it's just that my electronics knowledge isn't reaching far enough. I have a Symfonisk speaker by Ikea, which outputs a low and high/mid ...
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2answers
189 views

balanced to unbalanced audio switch

I have an audio source input, that I am putting through the circuit below to create a balanced audio signal. There will be one of these for each channel, left and right. I have been asked to provide ...
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1answer
52 views

Output voltage of Class B Amplifier with global negative feedback

For the following schematic on the non-inverting input is applied a sine wave. Shouldn't be the output on R19 0.9 out of the input voltage, by using a voltage divider between R31 and R19. From my ...
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1answer
74 views

A general purpose way to connect cellphone line out to a microcontroller ADC

I have looked at many questions with similar titles but cone cover my query. Question: How can I protect an STM32 Cortex M4 series ADC input when measuring the AUX output voltage from typical ...
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34 views

Summing Audio Channels

I’m trying to sum my car stereo output. Factory output has bass on one output and mid and tweeter on another output giving me 2 channels for left and 2 channels for right. Ideally I’d like to sum ...
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37 views

Building a voltage controlled Wien-bridge RC oscillator

Out of curiosity I'm trying to design an audio frequency range oscillator that would produce a pure sine wave. I'm working in simscape (simulink - matlab) and here is the design I produced : The idea ...
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1answer
29 views

Why signal coming out of a Constant K filter takes 0.5ms to stabilize?

I made a simulation of an audio amplifier with an input signal of 200 microVolts. The question is why my filter does not deliver the desired output, which operates between 512 Hz and 2048 Hz. From ...
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1answer
45 views

Add aux input to Audio Amplifier circuit

I have bought a ready Audio Amplifier using TDA7498 chip and now I need some AUX input other than default one. Is there any circuit for this? https://www.st.com/en/audio-ics/tda7498.html https://...
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3answers
184 views

Why are one channel's transistors in a power amp getting much hotter than the other's?

(Context: I don't have a background in e.e., but getting better at basic bench work.) I'm repairing/recapping an early 70s German integrated stereo. The power amp output section has four large ...
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3answers
67 views

DC Analysis of this common emitter circuit

I'm learning about transistor configurations (particularly in relation to audio circuits) and am having difficulty analysing this fairly straightforward common emitter stage from the Instrument input ...
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1answer
67 views

Electromagnetically shield guitar pedal

I've built a few guitar pedals using op-amps, transistors, etc. (with supporting resistors & capacitors of course), and I've generally 3D printed the housing for the components for custom designs. ...
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1answer
89 views

What does this transistor, parallel to the audio output load, do?

I'm reverse-engineering the analog frontend of an SPDIF-to-analog converter. I'd like to increase its output level before feeding the audio (AUX) input of a Bluetooth speaker, which seems to amplify ...
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1answer
70 views

Channel separation on a 3.5mm audio jack

I read an article regarding the removal of the 3.5mm audio jacks on phones. It quoted this: ...
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2answers
84 views

Simple stereo audio mixer power supply

I am trying to build myself a very simple audio mixer that can take 3 line-level inputs and create a single output for a set of powered PC speakers. I found a schematic online (here) which I have ...
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0answers
25 views

Troubleshooting adding a bluetooth receiver to my intercom system

I have a Nutone IMA 4406 intercom system with several intercoms throughout the house. I am interested in wiring a Bluetooth receiver to its Auxillary line in connection so that I can stream music ...
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1answer
127 views

Trigger PTT on Baofeng UV-5R with Arduino

A current project of mine is to have the Arduino Uno play an audio file off an SD card module. The audio file would come out of the Arduino and into a Baofeng UV-5R handheld transceiver. The first ...
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1answer
35 views

Some doubs regarding AC/negative voltages in an audio signal

I know that audio signals are AC signals (negative/positive voltage). Assume a typical Fuzz (guitar pedal) effect circuit below. It seems signals stay between 0 and 9 V (9V is the power/battery ...
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3answers
85 views

Connecting 2 1W speakers

I am trying to connect together 2 1W speakers and mount them inside some ear defenders. I am a complete novice and am following an instructable tutorial. The tutorial is a bit light on the basics and ...
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1answer
89 views

Attenuating mid-supply biased audio signal before AC coupled audio amplifier

The context here is simple volume control of a DAC generated audio signal with a potentiometer before an audio amplifier stage in a single supply, battery powered system. Is there any advantage to ...
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1answer
30 views

Stopping overvoltage with Solar on Lithium ion tool batteries for an audio application

I am using two Lithium ion tool batteries (18V) to get a 36 V line. When fully charged it is greater then 40V. As they are tool batteries, undervoltage protection is already built in. I want to be ...
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1answer
66 views

Why is my low pass filter attenuating everything so much?

I have a car stereo with low level outputs from an RCA connector. I wired one channel into a simple RC LPF, then into a TPA3116-based amplifier (this one), then to a single 4 ohm woofer. Using a ...
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2answers
93 views

Transistor substitution guidelines? (and the BC147A)

I'm in the US and fixing a vintage German integrated amp which has a crackle static issue I've isolated to a transistor in the preamp section. The transistor is specified in the schematic (below) as a ...
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1answer
31 views

how to use Aux Output Signal to light an LED

I have an Aux signal that I need to power a flashing light. I know the Aux signal itself does not have the power supply to do this. That's fine Because I can get power from somewhere else. My question ...
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1answer
36 views

Problem with custom USB microphone

I developed a MEMS microphone based audio capturing device and transfer that audio via USB to the PC. I used Audacity opensource software to test my working and found the audio plays well when ...
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1answer
48 views

Is the 3.5mm jack somehow connected to the phone's transceiver?

I could not find a clear answer to that and it's driving me nuts, because I have a microphone, which when connected to my phone via 3.5mm jack picks up a sort of buzz, as if from wireless inteference. ...
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1answer
69 views

Why is a square wave used for audio power calculations?

I am trying to read this datasheet (NXP TDF8546 Class AB Power Amplifier). On page 12, the power calculations are mentioned as Po(max): RL = 4 Ohm, Vp = 14.4V, Vi = 2 V RMS Square wave As far as I ...
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1answer
135 views

Is this TL072 stereo opamp circuit functional? Can it be used for LM833 too?

I modified opamp circuit a little bit and I hope it will work. I am not EE, so any advice is welcome. Can this schematic be used with LM833? And if i could, do I need to change values of some ...
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1answer
151 views

Multiple inputs for 5.1 audio system [closed]

this is my first post here and I hope I chose the right SE site. I have a Logitech X-530 5.1 audio system, which is very old and supports input using 3 3.5mm jacks for Front, Rear and Sub (I suppose, ...

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