All Questions
61 questions
0
votes
1
answer
40
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 ...
- 55
0
votes
0
answers
39
views
Changed TL072 to OPA2134 - high shelf cut on highs
So I've changed TL072 op-amp to OPA2134 on ART Tube MP V3 preamp. Everything is working except it appears that high-shelf cut is being created (~9 dB at 10 kHz) (measured with pro audio interface ...
- 365
0
votes
2
answers
97
views
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 ...
- 2,200
1
vote
0
answers
102
views
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) ...
- 111
1
vote
2
answers
227
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 ...
2
votes
2
answers
126
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 ...
0
votes
1
answer
172
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 ...
- 91
0
votes
1
answer
119
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 ...
- 5
0
votes
1
answer
109
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 ...
2
votes
1
answer
143
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
279
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 ...
- 455
0
votes
1
answer
81
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 ...
- 131
3
votes
1
answer
3k
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 ...
- 41
1
vote
1
answer
62
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 ...
- 13
4
votes
4
answers
252
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 ...
- 63
2
votes
1
answer
639
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. ...
- 215
0
votes
0
answers
225
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,...
-3
votes
2
answers
382
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 ...
- 1
1
vote
2
answers
771
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 (...
- 687
17
votes
3
answers
4k
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 ...
- 1,603
0
votes
1
answer
195
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?
- 172
2
votes
0
answers
994
views
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 ...
- 21
-1
votes
3
answers
2k
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 ...
- 101
0
votes
0
answers
131
views
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 ...
0
votes
0
answers
69
views
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 ...
- 455
1
vote
1
answer
677
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 ...
- 181
1
vote
3
answers
1k
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 ...
- 21
0
votes
0
answers
203
views
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 ...
0
votes
0
answers
311
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 ...
- 1
3
votes
2
answers
1k
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 ...
- 41
0
votes
3
answers
242
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 ...
- 123
2
votes
2
answers
395
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 ...
- 455
1
vote
0
answers
326
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 ...
- 141
0
votes
1
answer
489
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 ...
- 1
1
vote
2
answers
321
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 ...
- 175
0
votes
1
answer
691
views
Is the SSM2019 an appropriate IC for a optical sound solar cell preamplifier?
I am restoring a 35mm film projectors from the 1930s, which at some point had a Kelmar optical sound head added onto it. The solar cell outputs a balanced signal through an XLR jack that is very weak (...
1
vote
2
answers
481
views
OP Amp as audio preamp - am I doing it right?
I have a design that uses an ATXMega32E5 for two audio sources. In one case, a timer output square wave (3.3v logic) goes through a low-pass filter to make beeps, and in the other case, a DAC channel ...
- 1,603
3
votes
3
answers
10k
views
Need some help building a TL072 preamp circuit
I have an early 70's Magnavox turntable/radio console that I want to be able to plug my smartphone into so that I can use it as an external speaker. I'm plugging into the Tape In input, which is an ...
- 161
0
votes
1
answer
164
views
Can I add an audio jack to a digital audio board?
Can I use the preamplified audio signal on an iphone only microphone (Tascam iM2) to add an audio jack?
There is already a USB 5V input which perhaps powers the preamp, and a volume control where I ...
- 949
2
votes
3
answers
687
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 ...
- 133
2
votes
0
answers
536
views
Dual antiphase electret mic preamp topology
I am currently trying to make a preamp for an electret mic pair, which are placed physically in antiphase. The main idea is to subtract one mic's signal from another and therefore boost the signal ...
- 1,177
0
votes
2
answers
596
views
MPC508AP as central IC on audio input selector board
I am working on audio preamp and for the input selector I've created following design:
Now, as you can see, I've chosen Texas Instrument's MPC508AP Analog Multiplexer for input switching IC. However, ...
- 601
1
vote
5
answers
2k
views
Op Amp - Specifications are given for unity gain, how to choose another gain?
TL081 datasheet gives the following specifications:
How can I find the open loop amplification?
I know that the relationship between the differential voltage amplification and the (closed or opened?) ...
- 11
1
vote
1
answer
188
views
HPF cut-off in microphone pre-amplifier
In the below circuit, do Rbias and R2 both affect the cut-off frequency? Or is it simply 1/2*pi*R2*C2
- 1,876
0
votes
2
answers
642
views
Some questions regarding input stage of audio signals to the pre-amplifier
I'm very new to audio circuits but for the sake of curiosity I want to simulate an approximate version of a circuit of an audio input along with a smartphone pre-amp stage in LTspice. I will have five ...
- 12.2k
0
votes
1
answer
833
views
Preamp for Magic Eye VU meter [closed]
I want to build a Magic Eye Tube VU. This tutorial http://www.antimath.info/electro/vu-meter-em84/ says:
If this circuit is used with a tube amplifier, the “IN” connection in the picture is ...
- 103
1
vote
1
answer
523
views
Converting single-ended line audio to differential, on single supply?
I built an audio amplifier based on TI's TAS5630 IC. This is a Class-D amp with multiple configurations. I'm using it as a 2-channel amp. The problem is that this configuration requires a differential ...
- 1,181
3
votes
2
answers
2k
views
Soft fade out circuit for turning off speakers
I have some loud speakers connected to an amplifier. The problem is when I turn the preamp off, it sends a loud POP noise through the speakers. The turn off of the amp is delayed by 1 or 2 seconds, ...
- 433
1
vote
0
answers
673
views
Replacing trim pots with potentiometers?
I have been looking at and considering building the following circuit from Beavis Audio Research. Their explanation of the circuit:
Around 1965, Marshall introduced a few amps built around an 18 ...
0
votes
2
answers
528
views
Designing of an audio amplifier using LM386 and a preamplifier
This is the circuit . But i am still getting acoustic howling. What can I do to prevent it dynamically. Also I want to increase the sensitivity to the extent that when I rub my fingers in front of the ...