Questions tagged [preamp]
A preamp takes in very weak DC voltages or audio or RF signals and amplifies them enough to be used by a more conventional amplifier. Input may be in microvolts and output maybe 1 volt RMS or peak. They are often specific to amplify DC, LF/audio, RF or microwave bands. No preamp can cover DC to microwave bands and have good parameters at both DC and RF without software offset and gain correction.
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Choosing an OpAmp for MEMS mic preamp stage
I am trying to create an updated version of a mems mic board, like this one from sparkfun. They use an INMP401 mems mic (which is not recommended for new designs) and an OPA344 for the preamp stage (...
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12AX7 Valve Overdrive/Distortion Effect Pedal
I'm following the schematic below using the recommendations plus a couple of extra LEDs. With the footswitch in the enabled position, I'm not getting any sound. In the bypass position, the input and ...
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Help identifying a photodiode pre-amp PCB
Recently I found this PCB in a electronics junk bin. It's said that it's a photodiode preamp, but I was not able to find the datasheet or any information about the board.
Since the PCB looks neatly ...
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Impedance match Fishman guitar pre-amp to IRIG2HD
I'm looking for some help in understanding impedance matching. I'm hoping one or more of you technically savvy electronics folks will jump in and give me a simple circuit recommendation.
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Car microphone; very low signal
I would like to use a car microphone for bluetooth communication.
The mic is a BMW one: 84316938762.
The wiring diagram (TIS) marks the mic's two connectors for the pin 1 and 2: TIS (X18507).
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Op-Amp output voltage exceeds the power rail voltage (in simulation)
I'm designing a RIAA pre-amplifier based on the 2 op-amps from an NE5532 package. It seems that something is wrong, because the output of the 2nd stage is giving a 400V output which is way above the ...
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Simple 12V preamp circuit before speaker
In my apartment building, we have an intercom system with one central unit and multiple terminals, one per apartment. Unfortunately, after some unknown tweaks done a couple of years ago to the central ...
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Guitar to iPhone JFET pre-amp circuit issue
I am following this tutorial to build a simple JFET pre-amp to connect a guitar to an iphone.
This is the schematic:
I have soldered the components as per the schematic directly onto the 1/4" mono ...
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Designing 2-stage BJT CE class-A voltage pre-amplifier with specified goals and without global NFB
BJT CE Class-A Voltage Pre-Amplifier
Suppose a design requirement limits the selection choices to the following class-A BJT common emitter stage topologies. No global NFB is permitted. Only local NFB ...
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Op amp circuit with two capacitors
Based on an electronics lecture, we are dealing now with the preamplifier circuit for a detector. The figure is shown below.
Actual I am having the problem to understand the center operational ...
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How to measure the output impedance of a valve preamp?
I was trying to measure the output impedance of a DIY preamp for the past couple of days without any luck. Each time, I got to the same result of around 3K3 ohm, which is unbelievably low.
This is ...
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What's the point in a preamp?
I'm talking in the context of guitar amps, but I assume that this question is relevant for any type of audio amplifier.
Very often in amplifier schematics I see two stages of amplification -- first, ...
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Attempting an audio pre-amplifier circuit with falstad.com
I'm new to electronics and discovered the falstad.com simulator. I wanted to model this audio pre-amplifier circuit:
So I went into falstad and drew this:
My pre-amplifier circuit on falstad
The ...
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SparkFun Sound Detector Circuit Analysis
I would like to request some help in analyzing the op-amp circuit used by SparkFun here. I'm particularly interested in the pre-amplifier portion of this design.
The write-up included by SparkFun ...
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How to find feedback resistor value?
I want to implement typical guitar preamp scheme, like following:
I see, that it will have input impendance =2.2M...
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Preamp Ground Loop Problem
I have built the blue circuit above for my microphone but the one of the problems I'm facing is that when I connect it to my laptop's audio input, it creates a humming sound. My assumption is there is ...
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Troubleshooting TL071 to TA8207 100 Hertz hum
I worked out to build a pre-amplifier connected to a power driver in a single setups(a pcb). Problem arises when it's powered up. here are a few questions.
Setup has a TL071CP as preamp with a unity ...
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Does somebody have a schematic for a stereo electret condenser microphone?
I’m trying to use a Cmoy headphone amp (built around an OPA2227P chip) as a hard-wired in-ear-monitor.
I bought a stereo electret condenser microphone from Jaycar this afternoon, but I can’t get any ...
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Modern piezo microphone impedance-matching circuit
I want to record sound with a piezo transducer. I am connecting it to my sound card's input which has a good mic pre-amp. The levels are quite good and the sound seems quite clear but there's a lack ...
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MEMS microphone gain calculation for MCU ADC
I've got a Knowles SPH1642HT5H-1 (pdf link) analog MEMS microphone that I'm planning to connect to one of the ADC inputs on an STM32. I've done what I think are the correct calculations to determine ...
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Built a electret preamp but poor low frequency response
I have built this preamp using the TL071 IC.
It works, but it does have a bad low frequency response. If I plug the mic directly to my PC i can hear low frequencies much better. I don't have any ...
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Help with design a mic preamp with opamps for PGA and ADC
I want to sample an audio source using an electret microphone and analyze the spectrum of it with a uC. I'm interested in the 100Hz-2.5kHz range, so I calculate with these values when I tried to ...
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Guitar preamp problems
I built the following preamp to use with guitars
Basically the idea is to keep it on a single rail so that I can use it off the same battery with this power amp
https://www.eleccircuit.com/bridge-...
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Best microphone picking up sound within a small room?
I've tried several Electret Condenser Microphones as input to a generic USB audio sound card:
MO064202-4
MO064402-4
MO064402-5
All mics work great at close range (about 1 or 2 inches). However, none ...
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Phono preamp, one channel doesn't work
I have built a stereo preamp using this circuit (taken from here Hi-Fi Phono Preamp Rod Elliott - ESP), but for some reason I can't get the right channel to work at all while the left one plays.
Now ...
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What is simpliest possible guitar active preamp design
I want to build guitar active preamp inside my bass guitar. It has 2 humbacker pickups (3.4kOhm DC resistance each) for 2 lower and for 2 upper strings, and i want to preamplify each with a separate ...
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Output Impedance of a Pre-amplifier
This is an AC equivalent circuit of a pre-amplifier. I already derived the formula for input impedance (Zi) but I'm having trouble getting the formula for output impedance (Zo). I can't find a way to ...
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Figuring out the AC equivalent circuit(re model) of a Pre-Amplifier and Tone Control Circuit
I need help figuring out the AC equivalent circuit of this preamplifier circuit. I'm quite familiar with all the simple BJT configurations but this is my first configuring such a relatively ...
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Working of the LM-358 - microphone circuit
I had this task of converting the output of a microphone's voltage (data-sheet link attached) to a range of 0-5V, as this is the range required for the input to an ADC chip.
While I know that op amps ...
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NPN Transistor Pre-Amp Circuit - How do I calculate gain and voltage output?
I am calculating the voltage output of the below circuit. The output I have calculated varies by 0.1 of a volt compared with the simulation I created using multisim, but I am not certain this is ...
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Vintage Oscilloscope Preamp Whitepaper
Sometime early 90s I came across a whitepaper published by an oscilloscope manufacturer that described a custom preamp IC they had developed for their scopes. Does anyone know of this article?
The ...
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Pre-amplifier biased to one-half of power source
There is a schematic of an pre-amplifier that use one-half of voltage source output biasing (T1 emitter is one-half of V1). How the resistive network was calculated to allow one-half output Q-point?
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Is the SSM2019 an appropriate IC for a optical sound solar cell preamplifier?
I am restoring a 35mm film projectors from the 1930s, which at some point had a Kelmar optical sound head added onto it. The solar cell outputs a balanced signal through an XLR jack that is very weak (...
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OP Amp as audio preamp - am I doing it right?
I have a design that uses an ATXMega32E5 for two audio sources. In one case, a timer output square wave (3.3v logic) goes through a low-pass filter to make beeps, and in the other case, a DAC channel ...
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Need some help building a TL072 preamp circuit
I have an early 70's Magnavox turntable/radio console that I want to be able to plug my smartphone into so that I can use it as an external speaker. I'm plugging into the Tape In input, which is an ...
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piezo stereo preamp
I have found several projects on piezo preamps but I cant find anything that can run 2 piezo inputs to make it stereo and uses potentiometer to control volume gain etc.
What I found is "Collin’s Lab: ...
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Can I add an audio jack to a digital audio board?
Can I use the preamplified audio signal on an iphone only microphone (Tascam iM2) to add an audio jack?
There is already a USB 5V input which perhaps powers the preamp, and a volume control where I ...
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Why is my microphone circuit not working?
I'm trying to make a simple microphone/speaker circuit with a PreAmp and an Op-Amp. Currently, the speaker just outputs a high ...
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Troubleshooting noisy FET buffer for contact mic
I'm trying to follow the schematic on this page to create a preamp/impedance matcher for a balanced piezo contact mic. I've reproduced the schematic below.
I've built it on a breadboard and I'm ...
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How to test the input impedance of a Microphone Preamp?
How would someone test the input impedance of a microphone preamp? I have all the necessary equipment i.e. oscilloscope and multi-meters but I'm struggling to find information on the topic.
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Dual antiphase electret mic preamp topology
I am currently trying to make a preamp for an electret mic pair, which are placed physically in antiphase. The main idea is to subtract one mic's signal from another and therefore boost the signal ...
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What is the best preamplifier circuit for electret condenser microphone?
I have one old German directional dynamic microphone "SEL BST 205-1" and I remove everything inside it and pack 2 condenser microphones from mobile phones "Nokia 5130".
Like preamp I use this ...
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How can I attach an analog to digital converter to a guitar
I want to modify an electric guitar to add an ADC and microcontroller to drive some LEDs for fancy effects that follow music.
Since typical output levels of pickups are about 100mV, I was thinking of ...
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MPC508AP as central IC on audio input selector board
I am working on audio preamp and for the input selector I've created following design:
Now, as you can see, I've chosen Texas Instrument's MPC508AP Analog Multiplexer for input switching IC. However, ...
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Op Amp - Specifications are given for unity gain, how to choose another gain?
TL081 datasheet gives the following specifications:
How can I find the open loop amplification?
I know that the relationship between the differential voltage amplification and the (closed or opened?) ...
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Analog front end electronics
I am currently working on a project that involves designing some front end electronics that shape the charge pulse from a solid state detector (effectively a current source - I1 on the diagram). Our ...
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Reduce power consumption for AN7316 amplifier
I have a pre-amplifier with AN7316 from a tape recorder. Currently it draws 24mA from a very small 12V battery (I think it is an A23).
The IC has two parts: a "play" amplifier and a "rec" amplifier. ...
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HPF cut-off in microphone pre-amplifier
In the below circuit, do Rbias and R2 both affect the cut-off frequency? Or is it simply 1/2*pi*R2*C2
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Some questions regarding input stage of audio signals to the pre-amplifier
I'm very new to audio circuits but for the sake of curiosity I want to simulate an approximate version of a circuit of an audio input along with a smartphone pre-amp stage in LTspice. I will have five ...
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How does a preamplifier improve the Signal-to-Noise Ratio (SNR)?
I'm trying to understand how a preamplifier works.
Is the noise not amplified the same amount as the signal?
If so, how is that done in the preamplifier?
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