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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3answers
38 views

phono preamp input stage - exotic design

I found a very exotic (at least for me) moving magnet input stage of a phono preamp. It's taken from an old cartridge measurement system from renown brand. I simply can't figure out the logic behind ...
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How to build a low noise MIC preamp

I want to be able to talk on the microphone of my Headset A and send that signal out to the earphones of my Headset B. Something similar to what I show you on the image below. For that purpose, I ...
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AV Receiver playing music using RCA Analog input (AUX) from Mobile 3.5 mm stereo source

I have a pioneer AV Receiver VSX-832-K with RCA AUX INPUT "input (Sensitive/Impendency ) 200mv/47K ohm" issue : when i am trying to play music from mobile using 3.5 mm headphone jack using ...
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25 views

Does the type of preamplifier used for a piezoelectric sensor change its physical resonant frequency?

Two common amplifier circuits used for piezoelectric sensors are voltage amplifiers and charge amplifiers (pictured respectively). With the charge amplifier, the sensor is shorted but this is not the ...
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1answer
35 views

Signal distortion in simulation of a current to voltage converter

I'm trying to simulate a current-to-voltage preamplifier as part of a circuit I'm building. The current signals I'm working with range from pico-amps to nano-amps. With a gain of \$10^8\$ ohms, a 50 ...
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37 views

How To Make A Two-Channel Audio Mixer?

I'd like to make a 2-channel audio mixer. I'll connect one of the entrances to my phone with an aux cord. I'm going to put my headphone mic on the other one. I'll also connect a potentiometer to both ...
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58 views

Panning between two active audio signals

I want to have a circuit that pans between both my active pickups. I have designed a simple summing opamp with a 50k center click potentiometer acting as a panner but even though it worked, when at ...
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123 views

Electret microphone preamp is buzzing , weird noise and cannot find a solution

I'm building an electret microphone pre-amp following this application note, the output of the preamp is connected to an LM386 and then to some headphones. So my pre-amp circuit looks like this, where ...
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160 views

How do I design preamplifier and amplifier (for a speaker) circuits from scratch? [closed]

I am 3rd year electronics student. I want to design a speaker from the circuit level. As this is my first time, I have no clear idea how to start and where to start. Can anyone please suggest to me ...
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1answer
58 views

Troubles with mic preamp for headphones with integrated microphone

I am designing a preamp intended to interface with a microphone in common headphones (e.g. apple earpods, or sony headphones with a microphone) which will then connect to my ADC's inputs. I've ...
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49 views

Pre-amp connection problem

I am trying to complete the circuit shown above. I am having trouble as the ground connection is not clear to me. Please help me to complete that circuit. And also tell me how to connect C5 ground ...
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266 views

Why is there a winding on a capacitor?

I just came across this tube RIAA preamp on which there is a coil on the input capacitor, can someone please explain what's the reason of such thing? The schematic and the actual circuit bellow. The ...
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106 views

Ultra low noise charge sensitive preamplifier

I developing charge sensitive preamplifier for radiation detector. This is a very sensitive device, the smallest amount of noise can completely ruin the signal. The schematic and the PCB you can see ...
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1answer
65 views

Cartridge loading in Rodec phono stage

I saw a very strange design of phono stage in Rodec MX180 consoles. 3 generations of those mixers (mk1, mk2 and mk3) have this phono preamp on board! They have an input filter with 1nF cap then 220 ...
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63 views

Sound through the earphone is also sent to the amplifier when using a jack splitter after a audio mixer

I implemented the following audio mixer circuit with just 2 input audio sources: http://www.theorycircuit.com/audio-mixer-circuit/ Both sounds got mixed properly. Then, at the end of that audio ...
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139 views

Ultra low noise power supply for pre-amp

I have designed the following power supply smoothing circuit for my turn table preamp. This will be powered by a 24V 'wall-wart' type adapter. I tried to combine a transistor/zenner diode voltage ...
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46 views

How to make a preamp that is ON when input is a MIC but OFF when a LINE level?

My question is very simple: Is there a way to create a "preamp" circuit that is automatically ON when there is a MIC connected (for example, a desktop PC microphone) but OFF when there is a LINE ...
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224 views

TL082 electret preamp and LM386 power amp

I have spent the last few days trying to prototype a TL082 electret mic preamp (based on this schematic). I swapped the TL071 in ...
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72 views

Need to identify this 3-pin Connector to a small amp. It's a Pre-Amp input

I could use the neighbouring 3.5mm stereo jack for sound input, but those connections are flimsy. It's a 3-pin connector, 10mm long, 6mm wide and 7mm high with alignment slots on all sides but the ...
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47 views

Safely connecting a preamp powered by a benchtop DC power supply to a power amp

I pulled the preamp out of a broken guitar combo amp. The preamp has positive, negative, and ground leads for powering it at +/-25V. I would like to power the preamp with a dual channel benchtop power ...
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59 views

Alternative ways to step up voltage?

I want to drive an EOM crystal at 20 MHz for phase modulation. I recently bought a step up RF transformer (1:4 turns ratio), but it's not working fine above 2 MHz. I tried winding a transformer myself ...
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78 views

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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Circuit to power a preamp for a dynamic mic powered by the mixer's phantom power

I really hope that someone will be able to help me out with this. I have looked just about everywhere and left this question up at three chat rooms. I want to build a preamp circuit for a low output ...
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1answer
376 views

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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1answer
73 views

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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93 views

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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1answer
46 views

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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2answers
142 views

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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239 views

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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69 views

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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1answer
182 views

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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173 views

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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157 views

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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1answer
420 views

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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2answers
134 views

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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1answer
652 views

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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76 views

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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2answers
456 views

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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175 views

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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2answers
393 views

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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1answer
287 views

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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166 views

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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284 views

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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3answers
254 views

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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481 views

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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456 views

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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686 views

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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1answer
67 views

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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1answer
143 views

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 ...