Tagged Questions

2
votes
2answers
101 views

Bipolar Op Amp w/ Near Zero Offset?

My understanding is that if source resistance is low, a bipolar op amp has 10dB less noise than a JFET. I prefer the JFET op amps because the input offset is so low that you can eliminate coupling ...
8
votes
3answers
425 views

Audio Amplifier Op amp

I'm trying to design a circuit in which a microcontroller produces a signal and then using an amplifier drives an 8ohm speaker. I've so far used LM386, but it cannot go above 1W, which turned out to ...
4
votes
2answers
774 views

How to connect mic on arduino, with opamp?

I'm trying to connect a contact mic to an arduino. My knowledge in electronics is sparse, so please bear with me. I got a couple of lm833n audio dual opamps, which I'd like to put to use. I'm still ...
5
votes
2answers
327 views

Heartbeat amplifier

I found a video on youtube where the author amplified a heartbeat and his cat purring (link). We were able to replicate the circuit with some changes, but I made a mistake and got 8 ohm, 0.25 W ...
1
vote
3answers
264 views

Routing +12V and -12V for audio opamps?

I have 4 opamps which need +12 V and -12 V supply voltage. I have 2-layer PCB and want to keep it that way; the bottom layer is dedicated for GND of course. To keep noise/EMI as low as possible, +12V ...
2
votes
1answer
168 views

Circuit review: Impedance bridging for microphones

I have a pair of specialist condenser mics with a nominal output impedance of 3.6k Ohm that I would like to interface with mic preamps with nominal input impedance of 2.2k Ohm. Does this impedance ...
2
votes
1answer
715 views

Mic preamp: Inverting or non-inverting op-amp configuration?

What are the relative merits of using inverting/non-inverting op-amp configurations for a microphone preamp? While searching for microphone preamp schematics based on op-amps, I have found both ...
8
votes
4answers
309 views

Connecting an 80's style computer cassette to an FPGA

I'm re-implementing a 1980's Microbee computer on an FPGA (see here: http://www.toptensoftware.com/fpgabee) and trying to figure out how to do the cassette port. Here's the schematics for the original ...
1
vote
1answer
523 views

Simple and powerful audio amplifier around BA4558?

I have two BA4558 ICs from an old home stereo. I tested them with simple negative feedback circuit for each channel and with power supply of +/- 6V. The speakers I used are most likely with 8 ohm ...
6
votes
1answer
669 views

Reducing noise in audio circuit (optical pickup + op amp)

I am building an optical pickup using a photodiode connected to a LM741 op-amp. My circuit is similar to this one: Except that I've added a passive high-pass filter after the output of the op-amp, ...
9
votes
2answers
864 views

Twin-T Active Notch Filter Analysis

Could anyone give me a hint in analyzing the Twin-T Active Notch Filter? I tried a delta-star transform, followed by nodal analysis, but ended up with conflicting equations. For an example, look at ...
2
votes
2answers
928 views

Simple VU meter with Lm3915

I'm making a VU meter with an LM3915 and I would like to be able to plug my computers audio output into the LM3915 directly and get it to register. I've been searching the internet for a design but ...
3
votes
2answers
894 views

How to make LED bar graphs to measure intensity

I'm working with this design. I would like to make those LEDs into LED bar graphs that will show the intensity. For example, I want a song with a loud base to make the bar graph shoot up to the top. ...
1
vote
2answers
632 views

Can I replace MC33204P with one of these other op amps?

I'm working to make this schematic and I was wondering if it is possible to swap out the MC33204p with either LM348N or LM339AN. And if you could let me know why swapping them would still work I'd be ...
1
vote
2answers
456 views

How can I best amplify a signal from my headphone jack to operate a relay 3-32VDC?

I'm working with the following op-amps: LM308AN LM358P UA741CP I want to make a small box that will control the power to any string of christmas lights based off of music that is playing. I would ...
2
votes
2answers
116 views

How Would I Nomalize Cable TV Volume Between Commercials and Programming

I have had it with commercials on cable TV being a lot louder than the program I happen to be watching. I have also had the reverse where the program switches scenes and you cannot make out what the ...
0
votes
2answers
173 views

troubleshooting GEOFEX guitar effect panner

I'm building a circuit that allows me to blend a guitar effect in and out, based on >this< (page 2, bottom circuit). I have, however, replaced the 10k pot and the 15k and 51k resistors with 100k, ...
7
votes
2answers
521 views

Which op-amp for audio?

I understand that the NE5532 is an evergreen in audio applications. Which other op-amps would you consider for preamp, filter and other high fidelity audio applications?
7
votes
2answers
2k views

Audio delay using discrete components

I would like to make a circuit that causes an audio delay using discrete components. I know I can do small phase shifts using an opamp, but I am looking for something in the millisecond or second ...
5
votes
2answers
921 views

Tiny, cheap audio buffer with mute?

I need to buffer an audio signal (feeding into a variable input impedance), and make it mutable with a digital control. The best thing I can think of is an op-amp (maybe TS971? 3×2 mm SOT23) feeding ...