I looked up what a Op-Amp does, but I think I am not quite ready to understand all of this, so I just wannted to ask you how to use an Op-Amp to get -/+12dB gain on my Audio Signal. A easy explaination/ circuit whould help me a lot. I wannt to gain my Audio Signal form my Pc. I want my selfbuild graphic eq to have a gain that is controlled by a Potentiometer. The Ic I used (LA3600) has an Op-Amp already build in.

I am kinda new to electronics and just doing it as a hobby .

 

Below is the LTspice simulation of a circuit using a low-noise audio op amp that gives a ±12dB gain adjustment range by pot U2.
The simulation shows the gain for 0%, 50%, and 100% pot rotation.

 

Why don't you use the parts values and pcb shown on the datasheet of the LA3600? It has maximum boost of +8dB to +12dB and a maximum cut of -8dB to -12dB at each of its 5 frequency bands.

 

Why don't you use the parts values and pcb shown on the datasheet of the LA3600? It has maximum boost of +8dB to +12dB and a maximum cut of -8dB to -12dB at each of its 5 frequency bands.

I just wanted to do exactly that.

 

Cheap speakers must have a horrible frequency response to need +12dB or -12dB of equalization.
The speakers I built have a very smooth and flat frequency response and only small woofers need only some bass boost.

+12dB is 16 times the power (!) which can destroy a tweeter or ruin your hearing.

 

So what whould you recommend me to do when I want to use this with headphones?
I don't think 16 the Power whould be so healthy for headphones? Should I go for +/-6dB?

 

This whould be my schematic. I won't use 20 pots but 10 stereo sliders 2 for every bands (left and right). I am thinking about not getting an other gain pot because I chould just use all the sliders a a gain. What are your thoughts about it? Maybe any suggestions to improve the design?

 

I chould just use all the sliders a a gain.

That likely will not give a flat frequency response with some humps between the set frequencies, but it may not be noticeable in the audio.

You might just be able to use a dual audio pot to reduce the gain, as the max (0dB) gain may be sufficient.

 

That likely will not give a flat frequency response with some humps between the set frequencies, but it may not be noticeable in the audio.

You might just be able to use a dual audio pot to reduce the gain, as the max (0dB) gain may be sufficient.

I if I understand you correctly I should just put a dual pot on the end and use it as just negative gain?

 

Hello,

In the datasheet there is a sample circuit with the frequency response:






As you can see, there are dips in the frequency response when the gain is max or min.

Bertus

 

I if I understand you correctly I should just put a dual pot on the end and use it as just negative gain?

Yes, unless you really need more gain.

 

Hello,

In the datasheet there is a sample circuit with the frequency response:

View attachment 177110

View attachment 177111


As you can see, there are dips in the frequency response when the gain is max or min.

Bertus

I use 5 Bands more so do you think it wouldn't be so extreme? The spectrum what I equalize will be wider, isn't it like this?

 

How will you measure the frequency response of your speakers, headphones or hearing? Do you want a flat frequency response?
Or do you want to adjust the equalization so that a band sounds closer with a brighter sound or is farther with a duller sound?
Or do you want to make the sound different to what is recorded (more or less level at certain frequencies)?

 

It is just a "for fun and education" project I want simply use it with my headphones and without spending a lot of money get a certain thing that does exacly the thing I want, just a eq that can equalize certain frequencys and sounds decent.

I have got a other question. If I power it with micro usb and then a boot conveter to 12v, will it make a diffrence if I power it with just 5v. And how does the noise look like? Is it just depending on my usb adapter?

 

It is just a "for fun and education" project I want simply use it with my headphones and without spending a lot of money get a certain thing that does exacly the thing I want, just a eq that can equalize certain frequencys and sounds decent.

Fiddling randomly with an audio equalizer without seeing the original and the new frequency response graphs on an oscilloscope is useless and can cause damage to your headphones and to your hearing (deafness).

I have got a other question. If I power it with micro usb and then a boot conveter to 12v, will it make a diffrence if I power it with just 5v. And how does the noise look like? Is it just depending on my usb adapter?

I guess you did not see the datasheet for the LA3600. It says the recommended supply is 8V and a graph shows that it barely works with only 5V. If you boost frequency levels then you need to turn down the levels of the input so that the LA3600 output does not cause severe clipping distortion.

The LA3600 cannot drive most headphones but it can drive an audio amplifier or a headphones amplifier.

Noise could be high frequency hiss, mid frequency buzz or low frequency hum or any combination.

 

So you are saying I should just bumb it?
If so do you have a idea how I can realize this (different IC and so on)? Or is it just undoable?

 

For speakers you need an audio power amplifier that produces as much power as you want. For headphones then you need a headphones amplifier. If your speakers or headphones have a horrible frequency response then fiddle with an equalizer that might make better sounds.

 

For speakers you need an audio power amplifier that produces as much power as you want. For headphones then you need a headphones amplifier. If your speakers or headphones have a horrible frequency response then fiddle with an equalizer that might make better sounds.

I don't need a Amplifier I want to build a eq.

 

I don't need a Amplifier I want to build a eq.

The EQ circuit cannot drive headphones, instead it drives a headphones amplifier which drives the headphones. The datasheet of the LA3600 shows it driving a 10 thousand ohms load. Your headphones are probably 32 ohms.

 

The EQ circuit cannot drive headphones, instead it drives a headphones amplifier which drives the headphones. The datasheet of the LA3600 shows it driving a 10 thousand ohms load. Your headphones are probably 32 ohms.

Couldn't I just decrease the amplification? My Headphones got 18 Ohms.