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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Troubleshooting simple JFET preamplifier design

The circuit shown below (with actual measured values) simulates correctly in as much that it provides some gain. When I have built the circuit connected it to a signal generator using a 1mVp-p zero dc ...
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3 votes
3 answers
165 views

Single wire electrodynamic pickup preamplifier (transformerless ribbon mic)

I'm currently working on an experimental string musical instrument. It isn't my invention though. The source of inspiration called Dvina has an unusual pickup system. It senses the current induced in ...
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2 votes
2 answers
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Noise of low-frequency RC high pass filter preamplifier circuit with LT1028

I want to build a low-noise and low-frequency preamplifier with the first-stage opamp of type LT1028 offering an input-referred voltage noise density of about \$2~\mathrm{nV}/\sqrt{\mathrm{Hz}}\$ at \$...
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1 answer
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Transistored pre-amplifier

We have a transistorized preamplifier, which has a sinusoidal signal source as input. vi = VI sin(ωt). Being VCC >> VBE, VBE = 0,8V and the capacitors have infinite capacitancy. How can I ...
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3 votes
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What makes an op-amp good for electret microphone preamp vs other op-amps?

What makes an op-amp good for use in an electret microphone preamp vs other op-amps? Being JFET, current bias, voltage bias, etc? Does an op-amp that requires a negative voltage supply work better or ...
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2 votes
4 answers
266 views

What is the input impedance of this circuit?

Here is the relevant part of the schematic of the Befaco InAmp, a Eurorack preamp for line level and instrument level signals: I am trying to determine whether I can safely connect the AKG c1000S ...
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1 vote
2 answers
60 views

Input selectivity for a RF receiver pre-amp

In his answer to my question about common emitter amplifiers, @glen_geek commented that the RF receiver pre-amp I used as an example (shown in Figure 1) was "too simple" and that "any ...
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-3 votes
2 answers
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Preamp stage for audio amplifier using LM741CN clipping too early [duplicate]

I'm trying to build the preamp stage for an audio amplifier circuit using the LM741CN. I'm using a variable resistor for Rf so that I can vary the gain. What I'm finding is that when I have Rf set to ...
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1 vote
2 answers
205 views

Single-ended 3.3V guitar preamp circuit is clipping and offset

I'm designing an audio signal frontend to take an electric guitar analog output and deliver it to an ADC channel on a microcontroller. The µC/ADC are 3.3V devices (...
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18 votes
3 answers
3k views

Why does this op amp stop working after some time?

I have an audio streaming device I bought that has analog audio output that is way too low (it’s supposedly line level, and I’m not the only one who’s complained about this). I’ve been using this as ...
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1 answer
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simple NE5532 preamplifier circuit troubleshooting - sound disappears at upper end of gain potentiometer

I'm a bit lost trying to solve an issue I'm having with the attached microphone preamp circuit. If anyone recognizes what this problem is, I'd be very grateful for any help - thanks so much in any ...
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1 vote
4 answers
299 views

Is signal from electret microphone capsule (with FET) inverted?

Can I assume that the signal from an electret microphone capsule is inverted due to common source configuration of jfet? I would like to have non-inverted signal on my sound's card line input. Then I ...
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1 answer
58 views

Expected voltage on external gain resistor pre-amp

I want to build an amplifier with digitally controlled gain, using the THAT1510 pre-amp IC. The IC provides two pins to set the gain, using resistors. I want to switch between resistors with analog ...
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0 votes
1 answer
56 views

lowering output level of a phono preamp

I built a RIAA phono preamp that works great from these schematics: But the output level seems a bit too high. What would be the best way to lower it?
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FM receiver With LM386 - Need a Preamplifier

I am building a hoppy FM Receiver and I created the Preamplifier stage 1 and linked it with the LM386 Stage and it goes OK but The output sound from the Speaker is weak so I tried to do some ...
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2 votes
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Active low pass filter built around an LM386

I have some theoretical electronics knowledge from uni, but when it comes to applying it in practice, things can get a little bit complicated. I've built simple stomp box, basically a piezo transducer ...
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0 votes
3 answers
347 views

Op amp introduces phase shift at high audio frequencies

Context: I am trying to design a solid-state microphone preamp using dedicated audio op amps (ex: API 2520). Goals: flat ≈60-66dB of gain from 20Hz to 20Khz Limit changes in phase shift as much as ...
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3 votes
4 answers
551 views

LM358 Electret microphone preamp

I am trying to make an electret mic preamp with lm358. here are the pspice simulation results. I measured the voltage of the pins and the values ​​were simulated exactly like the sample. I tried with ...
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1 answer
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LTspice simulation of microphone preamp

Can someone help an idiot understand why this plot has dual traces? The node is between C2 and R7. I have replaced an electret microphone with an AC source. I don't know how accurate this is, so any ...
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Using diy lm386 preamp on standard commercial amp?

I have a small intercom-like device that has been siting around. It looks something like this. I suppose that inside is just a basic elect-mic and a button. Also i have an power amp which i used to ...
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0 votes
3 answers
374 views

How can I remove noise in my preamplifier circuit? [closed]

I need a low noise microphone preamplifier for my Arduino. I used a battery and standard wire but I had noise in my circuit. I need gain 20-20kHz. Can you help me with the schematic?
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Signal routing to power amp LM1876 based on TS5A22362 SPDT

Has anyone ever used the TI's TS5A22362 CI to route audio? I though of implementing the circuit below on which I intend to use the same supply voltage to switch between normally closed and normally ...
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0 answers
46 views

Additional gain with in-amp for nanovolt-scale pre-amp

Currently I'm designing a pre-amp for detecting nanovolt-scale(~100nV, <1kHz) signal for experiment. I need a final gain to be around ~100000. Since the magnitude of the signal is extremely small, ...
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0 votes
1 answer
83 views

What can cause voltage irregularities across an IC chip?

This is the preamp section of a channel of a tape deck for which one channel is working and one is not. Swapping all the components between the channels does not affect which channel is working ...
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2 votes
1 answer
82 views

Tube amplifier preamplifier

I received this little two tube preamp http://www.gikfun.com/electronic-diy-kits-c-7/6j1-tube-preamplifier-board-20-stereo-multiple-diy-kit-p-730.html It comes with 9 470uF caps. The symbol on the ...
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0 votes
1 answer
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Grounding adviseable on tube pre-amp powered by a 9VAC power brick?

I have an ART Tube MP pre-amp that is powered by a compact but rather heavy power "brick" that delivers 9V AC @ 1A. I use the pre-amp with a large-diaphragm microphone that gets its 48V ...
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1 vote
1 answer
283 views

TL072 opamp clipping problem

I'm trying to drive a TPA6120 headphone amplifier with TL072. I use single 24VDC supply with a TLE2426 virtual ground. The TL072 works well and puts out around 21Vp-p sine wave. But as soon as I ...
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1 answer
164 views

Small signal analysis of BJT dynamic microphone preamplifier

I am trying to do a small signal analysis for the following circuit I did not have any experience with BJT so I am having a hard time to analyze the circuit. From research, I know Q1 is common base ...
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2 votes
1 answer
112 views

Small signal analysis of dynamic microphone preamplifier circuit

I am trying to do a small signal analysis for a dynamic microphone preamplifier circuit. The original circuit is using BJT but I did not have much experiences with BJT, so I switched all BJT to MOSFET....
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1 vote
3 answers
229 views

Grounding a chassis with two prong plug

So I kinda shot myself in the foot by purchasing a two prong wall wart to power an audio preamplifier that I designed. I forgot to consider the fact that I should ground my chassis to the earth ...
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0 answers
214 views

High quality, low-noise, pre-amp circuit for condenser microphone (with phantom power)?

EDIT Suggestions so far, and reference to another question indicate that a discrete FET based input stage, perhaps followed by a particular low-noise IC for a second stage, might be a good approach. ...
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-2 votes
1 answer
90 views

Calibration of response of electronics : LTSpice [closed]

I would like to calibrate my electronics. Row signal is something like pulse-A, width is 40nsec. When I input this signal to preamplifier, output is something like pulse-B. I would like to calibrate ...
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0 answers
66 views

Pre-amplifier gain issues

I built a 2.1 subwoofer circuit. The schematic is below. The problem is the sound is low volume. It should be louder than this. I want to confirm the coupling capacitor values are ok in every ...
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0 votes
1 answer
129 views

Electret microphone and FET pre-amp

My question is about designing a microphone pre-amplifier that uses an electret microphone. I saw a video of Doug Ford on the EEVBlog, in which he shows some pre-amplifiers for microphones. My ...
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0 votes
3 answers
79 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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2 votes
3 answers
2k views

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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0 answers
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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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2 votes
1 answer
163 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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0 votes
1 answer
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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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0 votes
0 answers
146 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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1 vote
3 answers
339 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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2 votes
2 answers
631 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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-1 votes
3 answers
188 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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0 votes
1 answer
115 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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2 answers
72 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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14 votes
1 answer
321 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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4 votes
2 answers
286 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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1 vote
1 answer
250 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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0 votes
3 answers
172 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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533 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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