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.
223 questions
5 votes
5 answers
1k views
How is the 4.5V delivered in this charge amplifier circuit?
So I have found this circuit from this website: https://sound-au.com/project202.htm As you can see in the picture there is the 9V battery powering the omp amps, but for the +4.5V, how is that ...
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3 votes
2 answers
361 views
Why is there negative voltage in this preamp circuit
I found this pre-amp circuit for a guitar pedal (i think) and I am struggling with the negative voltage. With my limited knowledge most guitar pedals these days (including all of mine) use a 0v to +...
- 169
1 vote
1 answer
109 views
Combining differential high-pass Sallen-Key filter and differential amplifier into one op-amp stage?
This is a follow up of this question. I'm building a low-noise differential preamp for measuring PSU output noise with an oscilloscope. The design currently has three functional stages: Differential ...
- 2,558
2 votes
2 answers
115 views
Preamp PCB Layout Review: Risk of Shorts or Traces Too Close?
I’m designing the PCB for an audio preamplifier and would like to check if my layout is safe and won’t cause shorts. Some details: ±15 V DC traces, 1 mm wide, spaced 1 mm apart. Signal traces spaced ...
0 votes
0 answers
68 views
Pre amplifier and related circuits
I’ve attached a schematic for a call station system I designed. It includes two preamp options, though only one will be assembled at a time. The input comes directly from a gooseneck microphone with ...
- 9
0 votes
0 answers
84 views
The frequency attenuates too much at 2kHz in this preamplifier input transformer
I ran a sweep and measured the transformer output in this pre-amplifier circuit. It seems that at 2kHz, the frequency attenuation starts increasing linearly until 20kHz. It is not a small attenuation. ...
- 81
5 votes
3 answers
681 views
Balanced/Unbalanced Line Input in a Microphone Pre-Amp
I have following schematic, which is the input section of an audio mixing channel. While the balanced microphone signal goes through a transformer to the THAT1512 audio amplifier, i have also a ...
- 81
0 votes
0 answers
88 views
preamplifier circuit for a piezo contact mic?
I'm working on a project where I'm using a piezoelectric sensor to capture vibrations from a solid surface (like a contact mic). The signal I get is very weak and noisy when connected directly to an ...
6 votes
3 answers
449 views
Correct sequencing for plate voltage and filament bias in a 12AU7 tube power supply
I'm designing a power supply for a JJ Electronics 12AU7 triode and need clarification on the proper power-up sequence to maximize tube lifespan. Power Supply Details: Plate Voltage (B+): Transformer: ...
- 325
1 vote
1 answer
230 views
Review a copied Lownoise preamp (<1 nV/√Hz) Market-level designs rare
Circuit inspired by Herzlich Willkommen. from https://www.beis.de/Elektronik/LNPA60dB/LNPA60dB-en.html This preamp has 1–2.5 nV/√Hz input-referred noise, but it’s incredibly hard to find market-level ...
6 votes
3 answers
566 views
What is the proper value and location of capacitors on a guitar preamp?
The preamp and tuner on my guitar died, so I decided to make a new one myself. For the moment I am focused on the preamp. This is my preamp design (Scroll Down For Revised, Possibly Functional Version)...
- 207
2 votes
2 answers
317 views
Unwanted filtering in OpAmp Audio Circuit
I'm designing an amplifier circuit with two op-amp stages using the TLV2322 for a microphone preamp, which will feed an ADC. The microphone has a maximum expected amplitude of 20mV, and my goal is to ...
- 31
0 votes
0 answers
198 views
Low noise Hydrophone Preamplifier Circuit
I am currently developing a low noise preamp for a new piezo sensor that should be used as a hydrophone. Since I am actually from the signal processing domain the topic was quite hard to get into for ...
- 1
1 vote
0 answers
103 views
Amplifying a nanovolt sine wave signal from frequency range of 1 Hz to 30 kHz
I am having very duanting task of extracting faint sound wave that my piezo disc captures and creates output in nanavolts from 1 Hz to 30 kHz. Piezo is not that great in sensitivity, and I cannot ...
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0 votes
1 answer
84 views
Adding volume control between equalizer and power amp
I want to built an Equalizer preamp for my power amplifier(stk4141 II).The equalizer is "Rod Elliott (ESP)-Eight Band Sub-Woofer Graphic Equaliser".This circuit has input and output buffer ...
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