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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 the maximum dBu I can send into a microphone input in this schematic?

The schematic below is from the Icom 9700 radio service manual (page 80). I would like to feed this input from a mixer board's ALT-3/4 outputs, and I want to avoid blowing the TS462 microphone preamp ...
KJ7LNW's user avatar
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1 vote
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Can an audio isolation transformer between a preamplifier and an amplifier cause the amplifier's fuse to blow? [closed]

I'm building a microphone preamplifier. I was having problems with hum (intermittent ground hum when touching the case) and decided to try adding an audio isolation transformer (600 ohm : 600 ohm) ...
steev's user avatar
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1 vote
1 answer
96 views

How can the microphone senstivity be improved? It works for only a few centimeters

I am using an electret microphone with the preamplifier circuit attached below. The problem is that the microphone works only when I speak very closely to the microphone. If I speak from a distance, ...
Google Pandey's user avatar
2 votes
2 answers
130 views

Excessive DC offset in high-speed opamp amplifier circuit

Background A while ago I got my dad's old Musical Fidelity A1 MKI integrated amplifier from the early 80s (I believe). I found a blog that featured a lot of interesting information about this ...
jonatan.wilund's user avatar
1 vote
2 answers
209 views

Trying to record from DIY op-amp results in seldom pops and clicks

I have a 741-based audio amplifier PCB here from the 70s: When I tried to test it, I powered it with a 24V battery (I tried 12V as well with no difference,) then I shorted pins 15-19, connected the ...
Matilda Bentefor's user avatar
3 votes
3 answers
510 views

Voltage Buffer Vs Impedance matching

I am designing an Amplifier circuit for the microphone. For this, I am using a buffer in between two stages for isolation and I am confused between 2 circuits. I know, in voltage buffer circuits, the ...
ishankhowal's user avatar
0 votes
1 answer
65 views

Output-Z (electret) higher than Input-Z (preamp)

What happens if an electret microphone capsule (JFET in catridge) is connected to a preamp with considerably lower input impedance than the capsule's output impedance itself? ECM output Z: 2.2K Preamp ...
Domingo's user avatar
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1 answer
139 views

Understanding this MM/MC discrete phono stage

I am challenging myself at understanding my integrated amp's MM/MC phono stage; The amp is a Rega Elicit mk. I. It is a somewhat complex design and as a hobbyist I'm out of my league. The circuit ...
Joe's user avatar
  • 199
2 votes
2 answers
105 views

Something about the impedances of charge amplifiers

it is my understanding that due to the effect of virtual grounding, the input impedance of a charge amplifier is basically zero. If that's the case, then is there any reason to even worry about the ...
Smitty Flufferson's user avatar
1 vote
3 answers
332 views

Extremely Noisy Preamp Circuit on Breadboard (EDIT: Oscillation?)

I built a simple circuit (included below) on a breadboard and have been having some trouble with noise. Generally speaking, I get what seems like random noise averaging at about 1.5Vpp. Otherwise, I'm ...
Eli Y's user avatar
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1 vote
2 answers
140 views

Why am I getting this distortion in this circuit?

Can someone explain to me why I am getting this distortion for the following circuit? Input is a pure square wave. It happens at any input frequency or voltage. I was thinking the output would be a ...
Eli Y's user avatar
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1 vote
1 answer
48 views

No Output for Preamp circuit in TINA

Is this a spice problem or a design(me) problem? The rails are producing the expected 9 and -9 volts, but nothing is coming through on the output. I haven't ever done op amps without a bias voltage ...
Eli Y's user avatar
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0 votes
1 answer
135 views

Suggestions for Improving this Pre-amp Circuit

I made this preamp circuit for a dynamic mic and am mostly happy with it, but I'd love to get suggestions on how to make it a little better. I'd like it to have as little coloration as possible, and ...
Eli Y's user avatar
  • 91
0 votes
1 answer
68 views

Why Am I Not Getting my Expected Output in this basic Op-Amp Circuit?

I thought that A = 1 + Rf/Ri for an op-amp non-inverting amplifier? With a 1mV input, I'm getting output voltages in the uVs...
Eli Y's user avatar
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0 votes
4 answers
121 views

Microphone pre-amplifier op-Amp outputs larger voltage when Mic RL is larger

I am following TI's pdf Non-inverting microphone pre-amplifier circuit with AOM-4544P-2-R microphone. I probe the circuit on the Vout after the op-amp, (not on the mic directly). I am playing around ...
Christianidis Vasilis's user avatar
0 votes
1 answer
103 views

Old Zener diode codes

I am trying to identify another Zener diode from a wem pa 100 pre amp, there is no spec on any of the various schematics I have seen, or to think of it there is never any on any WEM schematic for any ...
Paul's user avatar
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0 votes
3 answers
321 views

Bats ultrasounds detector with LM324

I have some questions about this small project, a device to detect bat ultrasounds and reproduce in a speaker. It's based in a post of the Element14 community, Episode 578. I have adapted it and I'm ...
Gos's user avatar
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0 votes
1 answer
67 views

Suggestion about drag and amplify pulse

Following picture is Photodiode I/V pre-amp of my circuit My target pulse from OPA356 output, which range is 15mVpp /130ns-width to ...
curlywei's user avatar
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0 votes
2 answers
121 views

How can a resonance circuit work as a current amplifier?

I have been working on current amplifiers for my RF circuit. I was thinking about pre-amplifying the current by a tank circuit. The input of the circuit is just a mp3 player, which has not much ...
user avatar
0 votes
1 answer
103 views

Is there a risk of a DIY pre amp damaging a microphone?

I'm looking for a preamplifier to use with an aquarian A1S hydrophone. This is an application where signal integrity is not very important and we're going to filter and do a fourier transform on the ...
Smitty Flufferson's user avatar
1 vote
1 answer
175 views

How does this microphone preamplifier work?

This preamplifier circuit is designed by Andy Collinson for dynamic microphones. I can't understand how it works. Why is the microphone input connected to the emitter of Q1 instead of the base? ...
ElectronSurf's user avatar
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0 votes
1 answer
65 views

Standards for measuring analog audio signal devices

I'm making a Analog Channel Strip for a project. I'm searching for standards that let me or give me an advice of how to measure Dynamic Range, THD and THD+N, SNR, Frequency Response and input/output ...
Zlmanuel87's user avatar
2 votes
1 answer
117 views

Combining a mono signal with a stereo signal

I'm creating a stage sound system I have already created a preamp for the microphone and led the connector through which I will feed the music. Now I need to mix music with a preamp. The problem is ...
Tristan Gorynia's user avatar
0 votes
2 answers
219 views

Non-inverting NE5532 with 1.56 gain not working

I made 4 preamp's for laptops and cellphones using 2 NE5532 IC's. The expected gain is 1.56 so, I used a 5.6K resistor as the feedback one and a 10K from the inverting input to a 47uF bipolar ...
Gabriel Santos's user avatar
0 votes
1 answer
66 views

Noise problem in preamp to digital processor

I'm building a guitar audio processor. I inherited this circuit from someone else's project. I am seeing a significant amount of noise on the input. I digitize the input using a 16b ADC and clip to ...
Jim M's user avatar
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6 votes
3 answers
1k views

What is the purpose of these passives in a microphone pre-amplifier circuit?

This is the typical application circuit of the MAX4466 "microphone preamplifier" op-amp. Are these resistors/capacitors purely for generating a bias voltage? If so, aren't there much simpler ...
laust0rm's user avatar
0 votes
0 answers
51 views

Building a MEMS Microphone Monitor System

While I've never used a breakout board when building an electret mic, I have used the small Spark Fun 09068 and Cinimark admp401 boards for MEMS mics. They seem to work with a 9v battery box I built ...
Adrianw's user avatar
0 votes
1 answer
317 views

Pre-amplifier for digital oscilloscope

I have an ATTEN ADS1062CML 60 MHz 2-channel digital oscilloscope and it has quite poor input sensitivity. My idea is to build a 2-channel low-noise pre-amplifier. I mostly need the oscilloscope for ...
CNCman's user avatar
  • 1
3 votes
1 answer
2k views

What is the difference between using transistors and op-amps in pre-amplifiers? [closed]

What is the difference between using transistors and op-amps in the design of audio preamps? What are the advantages and disadvantages of using each? Based on my research, using op-amps is better as ...
Sayed Hashem's user avatar
1 vote
1 answer
56 views

Tube preamp overdrive question

Is it possible to add an overdrive gain pot (instead of just simply a bypass switch) to a preamp tube circuit? I am designing a new amplifier, and I want to include an overdrive/distortion option to ...
Mike Hale's user avatar
0 votes
2 answers
135 views

LNA and DC amplification

In a THz detector, it produces a DC output voltage proportional to the input signal intensity. I need high SNR. My doubts are: Can I use LNA as a preamplifier? Is DC amplification possible with LNA? ...
prashanth's user avatar
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4 votes
4 answers
239 views

Name and cause for phenomenon in microphone preamp output as seen on scope screen

What might cause 1 kHz sinusoidal signal to change such as seen on the screen? How is this phenomenon possibly called? I have quite a lot of hand microphones with built-in opamp preamp and electret ...
UIR's user avatar
  • 63
1 vote
2 answers
191 views

Why won't my pre-amp circuit enable my condenser microphone to work with my boombox?

I recently bought a boombox for my mother to play and record cassette tapes. I didn't realize at the time that the boom box did not have a built in microphone. I then bought a condenser microphone for ...
Nil's user avatar
  • 113
2 votes
1 answer
490 views

Building a dynamic microphone preamp

I'm looking to build a preamp for a dynamic microphone (SM57, rated at 150 Ω with -56 dBV/Pa). I've just finished a course in circuits and I'm having a bit of trouble approaching this design problem. ...
Andrew Li's user avatar
  • 215
0 votes
1 answer
774 views

Audio line-out to amplifier line-in matching impedance and voltage

I am an electronics hobbyist. After reading online my understanding is that an op-amp buffer or JFET pre-amp can be used to match a medium (lower) input impedance with a high output impedance. In my ...
technofreaks's user avatar
0 votes
0 answers
197 views

LM386 as pre-amplifier for electret capsule

Although I know the LM386 is intended as a power audio amplifier, I wish to know if it can be used as a pre-amplifier for an electret microphone capsule, as I intend to use it for that purpose. If yes,...
Awais Mushtaq's user avatar
1 vote
2 answers
449 views

Input voltage noise (RTI) calculation for preamplifier

I would like to obtain the RMS Input Voltage Noise (RTI) of the AD8428 preamplifier for the following setup range of 0.1 Hz to 150 Hz with 1st order lowpass filter, koeff = 1.57 ---> BW(bandwidth) ...
NNN123's user avatar
  • 103
0 votes
1 answer
143 views

Reasons for subharmonic mains noise in preamplifier

I have a preamplifier based on an OPA1611 that I wanted to characterize. The amplifier is in a fully enclosed and earthed metal chassis, which has an AC-DC converter in it. The mains cabling goes ...
tobalt's user avatar
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0 votes
2 answers
103 views

How does the transient protection in this AC-coupled preamplifier work?

I'd like to build a preamplifier for measuring the noise of very quiet linear regulators using a baseband spectrum analyzer. I found this page, which presents a few designs for this and looks ...
MattHusz's user avatar
  • 1,053
2 votes
2 answers
224 views

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 ...
user avatar
3 votes
3 answers
324 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 ...
e_asphyx's user avatar
  • 613
2 votes
2 answers
283 views

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 \$...
Charly's user avatar
  • 752
1 vote
1 answer
315 views

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 ...
Pacoco's user avatar
  • 13
4 votes
1 answer
236 views

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 ...
Radu's user avatar
  • 51
2 votes
4 answers
449 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 ...
Jaap Joris Vens's user avatar
1 vote
2 answers
345 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 ...
kene02's user avatar
  • 538
-3 votes
2 answers
349 views

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 ...
hasin's user avatar
  • 1
1 vote
2 answers
644 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 (...
pion's user avatar
  • 460
17 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 ...
nsayer's user avatar
  • 1,593
0 votes
1 answer
2k views

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 ...
otivlasc's user avatar

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