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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2 answers
202 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 ...
0 votes
1 answer
341 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 ...
2 votes
2 answers
1k views

What makes a microphone preamplifier good or bad?

What are some of the factors that make a microphone preamp good or bad? Noise cancelling, reverb and other factors. I'm trying to build an electret microphone that will handle voice recognition from a ...
4 votes
3 answers
10k views

Transistor mic preamp

I built this mic preamp circuit for use with an electret mic. The mic I have is this PUI AOM4544 electret mic I have plugged this mic preamp circuit to my soundcard line in. But I think the gain is ...
1 vote
2 answers
609 views

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 ...
3 votes
3 answers
1k 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 ...
3 votes
3 answers
347 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 ...
0 votes
1 answer
57 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 ...
4 votes
4 answers
229 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 ...
0 votes
1 answer
103 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 ...
2 votes
2 answers
90 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 ...
1 vote
3 answers
233 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 ...
1 vote
2 answers
118 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 ...
1 vote
1 answer
45 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 ...
0 votes
1 answer
122 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 ...
0 votes
1 answer
62 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...
0 votes
4 answers
103 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 ...
0 votes
3 answers
233 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 ...
0 votes
1 answer
84 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 ...
0 votes
1 answer
89 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 ...
0 votes
1 answer
65 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 ...
0 votes
1 answer
98 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 ...
4 votes
5 answers
7k views

What is ALC on a preamp?

I have a preamp rescued from an old stereo: BA3308 It has a pin "ALC" and the data sheet keeps going on about how splendid this ALC is and how it has a built-in ALC diode and such. Nowhere does it ...
25 votes
7 answers
5k views

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, ...
0 votes
2 answers
225 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 ...
4 votes
1 answer
207 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 ...
1 vote
1 answer
157 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? ...
0 votes
1 answer
49 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 ...
2 votes
1 answer
101 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 ...
0 votes
2 answers
163 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 ...
0 votes
1 answer
61 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 ...
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 ...
0 votes
0 answers
47 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 ...
0 votes
1 answer
235 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 ...
3 votes
1 answer
1k 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 ...
1 vote
1 answer
54 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 ...
0 votes
2 answers
108 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? ...
1 vote
2 answers
158 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 ...
2 votes
1 answer
361 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. ...
0 votes
1 answer
502 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 ...
0 votes
0 answers
169 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,...
1 vote
2 answers
341 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) ...
0 votes
1 answer
122 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 ...
2 votes
2 answers
330 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 ...
0 votes
2 answers
101 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 ...
2 votes
2 answers
195 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 ...
3 votes
3 answers
311 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 ...
2 votes
2 answers
234 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 \$...
1 vote
1 answer
300 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 ...
6 votes
2 answers
2k 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 ...