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need help with audio mixer? Answered

Hello . im going to make this mixer circuit.Im not sure if it work fine or not.Can you please check it for me ? Thank! In this schematic, i use R1=R2=47k Ohms , can i use a lower value like 10k or 4.7k ? http://i247.photobucket.com/albums/gg132/chipmapple/mymixer.gif

Question by login721    |  last reply


opamp voltage bias question.? Answered

Hello. i have a question about voltage bias.In some schematic of opamp use single power source , they use R1=R2 to make voltage bias (please see the example bellow) . But the value of R1 and R2 in other schematic i found are diffirent (R1=R2=100k or R1=R2=47k ,.... etc) How did they effect the circuit ? Thanks for advance ! sorry for my bad English .

Question by login721    |  last reply


Help on a divide and blend circuit - wet and dry - tl072

Hello,i want to build a "divide and blend" circuit with one potentiometer to blend between a dry and wet signal, the source will only be audio and the wet signal will be a clone of the MS-20 filter.my knowledge of electronic is almost zero... so i looked on different circuits and tried to adapt to what i want, but i need you guys to confirm if what i've designed works? do you see any problem? to you have any suggestions? thank you very much

Question by FilipeB21    |  last reply


for audio buffer :TL072,BC107B,2SC1815 , which is lower noise ? Answered

Hello . I going to make a guitar pedal.In original schematic ,they use BC107B for audio buffer.But i dont have any BC107B in stock, so i decide to use TL072 or 2SC1815 to make audio buffer.But which is lower noise ? Thanks! sorry for my bad English.

Question by login721    |  last reply


I need a sub for a TL082 IC

I am trying to build a bass specific 3 band  equalizer, and the only schematic i found uses a TL082 IC, would a TL072 work as a sub? if not what chips would?

Question by fatfoohy    |  last reply


How do I power a spectrum analyser?

I want to make an audio spectrum analyser using 8 lm3915 IC chips and 4 TL072 chips with a TL071 amp for the TL072 chips. The TL072 chips will be wired into bandpass filters of different frequencies, which will output into the individual LM3915 chips. These ICs will be wired as VU meters. The outputs will be these LEDs: http://www.rapidonline.com/Electronic-Components/5mm-Round-Diffused-LEDs-with-Integral-Resistor-518908 I would also like to add a feature of adding a feature where when the ambient light is lowered, more lights turn on using another LM3915 chip. Another feature I would like to add is an amplifier and I want the spectrum analyser to respond to background music via a microphone and a pre-amp. The circuit I am going to use is: http://stavebnice.postreh.com/picture/PT041_schem_v.gif Finally, I would like to ask If this is plausible and what power supply should I use? It must be able cope with the power demands of these features. The power supply has to be from rapid electronics, because my school can only buy from rapid. Also, I would like to know what power amplifier I should use (25w, 30w, etc). Thanks! (I don't want to use microcontrollers, because I want to make my spectrum analyser look cool by showing the electronics (microcontrollers look simple) :)

Question by knektek    |  last reply


How to pick best battery for amplifier?

Hello, I ordered this amplifier and I need to pick best battery for this amplifier. Would be great to power it for at least 3-4 hours on maximum volume (200W rms subwoofer and 2x50W rms speakers). I need lightweight battery and powerful battery, size does not matter, budget is low so nothing overpriced I do not want.

Topic by RobertasP4    |  last reply


How to pick best battery for amplifier? Answered

Hello, I ordered this amplifier and I need to pick best battery for this amplifier. Would be great to power it for at least 3-4 hours on maximum volume (200W rms subwoofer and 2x50W rms speakers). I need lightweight battery and powerful battery, size does not matter, budget is low so nothing overpriced I do not want.

Question by RobertasP4    |  last reply


What type of mixer should i use (diffirent type input)? Answered

Hello . I want to make a op-amp mixer with 2 inputs. Input 1 : mono signal from mp3 player. Input 2 : mono signal from overdrive pedal. (please see the image bellow ) I have op-amp : tl072 and ne5532 and i need the pedal use single power supply. and the schematic of the pedal i use is show bellow. thanks for advance ! p/s: sorry for my bad english.

Question by login721    |  last reply


Do I need to invert phase a second time? Answered

I'm building a guitar pedal and I am inverting phase with the initial buffer (TL072). I am then splitting the signal into two parts, dry (no effect) and wet (effect). Each of these will be output as separate channels (left and right) and not mixed back to mono. I plan to send each channel through its own 386 amplifier chip to boost it to a level suitable for headphones. So, what I am wondering, is, should I use the 386 to invert the phase a second time back to normal? Or should I use an op amp at unity gain to do that before I send it to the 386? Or does it not matter if I am not mixing the two signals back to mono?

Question by randofo    |  last reply


Noise in Amp from LED Strip & servo

Hi, I am working on a project in which TL072 is amplifying an audio signal which is going to speakers & arduino analog input. Amp is powered by a wall wart with 12V 2A output. The same 12V is also regulated to 5V and used to power an AVR. The AVR is being used to PWM, using a power transistor(TIP120), an LED strip taking 1A from the same 12V supply. There  1) Now the rapid switching of current for LED strip is messing up the amplifier output. It's working fine with LED Strip off but when using PWM, there is a high frequency noise in the amplifier output. I have a 0.1uF and 10uF caps near power inputs for both AVR and amplifier. This is probably due to insufficient decoupling. Can someone please help me make it better? 2) There is another independent source of noise I'm finding which I'm unable to explain. The audio is going into Arduino which is controlling a servo as well. As soon as the servo is connected, there is a constant loud noise in amplifier output. This remains even after powering the arduino and servo using seperate USB supply(only ground connected). I placed audio setup and servo data wire far apart since they may be interfering due to PWM used for servo, but it wasn't of any use. Since in both cases, amplifier is producing noise, I think my amplifier diagram might be at fault. If I remove the amplifier, the audio stream reaches arduino without any noise . Anybody got any ideas how to remove these 2 noises? Attached images: amplifier schematic, graph of audio input in Arduino analog pin. -Antzy

Topic by Antzy Carmasaic    |  last reply


Capturing Audio using ESP32

I'm building a modest wall of lights with an ESP32 and dozens of ws2812b leds and thought wouldn't it be cool to set it up as spectrum analyser. I was thinking of having bluetooth speakers with an aux out, pair them to my phone and hook the aux out to the ESP32 to analyse the audio and drive the leds. Of course, it's not that straight forward so I thought I'd break it down into smaller tasks - First off hooking up the aux cable to the ESP32Amanda’s explanation of her op amp circuit proved very useful as a starter for 10 but I'll need to make some changes .First off, I need to lose the 9 volt batteries. To do this I believe I can replace the TL072 dual op amp she used with a TLV2372 dual rail to rail op amp. (Keeping it dual just in case I go stereo) The rail to rail feature allows me to use my currently available 5 volt supply rather than needing a higher voltage from the batteries Dan also pointed out in the comments, that the circuit is an inverted amplifier rather than a non-inverted amplifier. I checked out op amp circuits on Wikipedia And It turns out he was right – good catch Dan He’s obviously very smart so I also went along with his other suggestion of strapping the opposing input to ground with a 10k resistor to reduce noise For this project I don’t wish to use a mic and will be replacing it with an aux in jack so there is no need to give it any power. The amplitude of the voltage will be about half that of Amanda’s microphone but we have the variable pot to crank up the amplitude. Finally I’ll be replacing the Arduino with an ESP32 to perform the sampling/analysis of the signal. It’s faster and has bags of IOT features but I’m concerned I’ll need to make yet more changes. The Arduino ADC pin has a range from 0 – 5 volts whereas the ESP32 has a range of 0 - 3.3 volts. Thankfully we have the variable pot to adjust the amplitude to say 1.5volts . And for the voltage divider we can take advantage of the 3.3volts provided by the ESP32 dev board so there is in fact no need to adjust the resistors as the 100k/100k split gives us the desired 1.65 offset voltage. That turned out to be a lot easier than I expected So the circuit now looks like this Well done for reading down this far! Let me know if you see anything I may have missed or perhaps direct me to a similar project where I can pick up more tips Thanks

Question by CharlesGoodwin65