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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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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Preamp for Magic Eye VU meter [closed]
I want to build a Magic Eye Tube VU. This tutorial http://www.antimath.info/electro/vu-meter-em84/ says:
If this circuit is used with a tube amplifier, the “IN” connection in the picture is ...
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Converting single-ended line audio to differential, on single supply?
I built an audio amplifier based on TI's TAS5630 IC. This is a Class-D amp with multiple configurations. I'm using it as a 2-channel amp. The problem is that this configuration requires a differential ...
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Soft fade out circuit for turning off speakers
I have some loud speakers connected to an amplifier. The problem is when I turn the preamp off, it sends a loud POP noise through the speakers. The turn off of the amp is delayed by 1 or 2 seconds, ...
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phono preamp hum - ground loop?
I've built a simple 2 stage active/passive phono preamp. Everything in terms of amplification/frequency response/lack of distortion works fine - just as it was designed. The only thing is that hum can ...
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Piezo transducer preamp and AGC/compressor
I've been suggested this circuit as a good low-noise high gain piezoelectric transducer preamp (used to pick up really faint sounds in water).
It is nice because it includes a high pass filter (yet ...
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Using Microphone preamplifier IC Max4468
I am designing microphone preamplifier using MAX4468 (datasheet), but the reference diagram shows output from microphone (microphone input) going to both inverting and non-inverting terminals of the ...
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Replacing trim pots with potentiometers?
I have been looking at and considering building the following circuit from Beavis Audio Research. Their explanation of the circuit:
Around 1965, Marshall introduced a few amps built around an 18 ...
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Pre-amplifier to drive LM324 Op-Amps
I want use Electret microphone Pre-amplifier described in TI document, with Color light organ. Will the output level of this pre-amp enough to drive LM324 Op-Amps on Color organ? Input signal goes to ...
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Common Emitter Amplifier Problem (Incredibly lower Gain than input, and Distorted)
I'm trying to create a common emitter amplifier to power a medium sized 8 ohm speaker as a learning experience using one NPN transistor specifically the PN2222A.
Here's the design schematic in ...
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(LM2902N based) Variable gain for a Instrumentation amplifier
I'm trying to build a Instrumentation amplifier that would do a 10uV -> 10mV amplification. The motivation is to measure uA ...
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How To Eliminate Amplifier Squeal When PreAmp Power is Turned Off
I have a bass guitar that has a built-in pre amp, which is switched ON whenever the cable is plugged into the bass. I typically use the bass all day, and leave the amp on and the bass plugged in - ...
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Designing of an audio amplifier using LM386 and a preamplifier
This is the circuit . But i am still getting acoustic howling. What can I do to prevent it dynamically. Also I want to increase the sensitivity to the extent that when I rub my fingers in front of the ...
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Does audio OP-AMP circuit needs output capacitors?
I saw schematics with and without output capacitors. So in the end - do you really need capacitors in the output?
I am using OPA2134 operational amplifier. I plan to use it both as headphone and ...
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Single double triode vacuum tube for headphone amp at high voltages
I'm planning to build a single double triode vacuum tube as I have seen many schematics even though most of them are low voltage (20-40v). However I didn't seem to find a high voltage single double ...
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How do you know if a vacuum tube is going to suffer from AC hum or not?
I know that technically there is little difference between AC or DC heating of the tube - if it gives proper voltage everything is fine... Except the hum:
I have read in various sources that some ...
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How can I create a microphone preamp with a variable slew rate? [closed]
How can I create a microphone preamp with a variable slew rate that is dialed in with a button and have a wide range from very slow to very fast?
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Feeding 2 stage discrete pre-amp to LM386 to add gain
I need about 20 V/V or so of additional gain for a pre-amp I am making which currently consists of two transistors and is shown below. I was wondering if I can simply feed the output of the transistor ...
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Running preamp tube filament on 5v?
Is it safe and not harmful to run a preamp tube filaments at 5v? The tube is ECC85. I built a tube preamp in a DIY portable guitar amp. It's very similar to Matsumins valvecaster with a few slight ...
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How to 'simulate' an input device?
I made a diy guitar amplifier with two seperate amplifiers. When potentiometer is raised something strange and annoying begins - various whispers, noises and reacts really strange. HOWEVER this never ...
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Is there any real world difference in upgrading TL071 to OPA314?
I have a DIY made guitar amp in which there is a TL071 preamp section. I read various opinions about how upgrading op amp improves that sound and how it doesn't do anything really... I'm quite ...
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Single supply differential balanced preamp
I'm trying to build a single supply balanced preamp for an electret mic. To further complicate matters, I'd like to impedance balance the mic output to take full advantage of the preamp's noise ...
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Mic preamp, fixing noise and gain issues
I'm trying to fix a preamp (made by a colleague) that's noisy and somehow not amplifying enough. I should say right away that this project is pushing the edge of my electronics knowledge so I have a ...
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sallen key butterworth interfacing with arduino Due
I am using this stethoscope circuit
I want to give TL072 butterworth filter output to Arduino Due ADC which input is max 3.3 but the supply of the mentioned circuit is split +9-0-(-9) volts. How can ...
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Noise on mic preamp plus aux mixer
Very new to audio hardware so please bear with me :) What I wanted to do was make a simple unit that takes a mic input, mixes it with audio playing from the headphone jack of an iPod/iPad/etc and ...
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ESD protection for OpAmp inputs and outputs
The following circuit is a preamplifier that we are currently using. In real practice, we do not have the photodiode connecting with OpAmp directly on board. Instead, the photodiode is connected with ...
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