[SOLVED] Bass Booster effect

I am programing a drum machine in Arduino with sequencer and everything and I am doing pretty well
I wanted to add some effects for it, and thought of a BASS BOOSTER so the bass drum could sound very fat and also a little distorted if the user wanted it (you can turn up the bass booster and lower the bass drum volume if it gets too loud).

I breadborded a circuit I found online:
http://circuit-diagram.hqew.net/Discrete-Bass-Booster-Circuit_4725.html

And it almost has the sound I am looking for, so it’s fine for starters. As you turn P1 and P2 it goes from NO SOUND to a PUNCHY BASS SOUND.
Now, I want the user to be able to go from a DRY sound (not filtered) to a BASSIER sound (filtered and distorted) and this booster circuit only outputs the filtered sound.

It’s not really what I wanted but I thought of using an op-amp as a mixer for the dry and wet output, the dry beeing always on and you can add bass by mixing the output as you turn a knob.

I then breadboarded this circuit:

and connected the dry output to one of the inputs and the wet output to another, but I am not getting both sounds at the same time, as you turn the P1 and P2 from the boost circuit it makes something strange: At one end you get full dry sound and at the other end you get the full wet sound, the weird thing is that at the middle point you get a VERY THIN sound, with no bass.

I also looked at “blender” circuits, but didn’t tried yet.
What do you think???

Thanks a lot!

PD: attached an mp3 sample so you can hear it, it’s a little quiet (doesn’t has the bass boost!)

hola clara2.mp3 (997 KB)

Hi, just looking at your two circuits, the first with the single transistor, inverts the waveform from input to output.

This means when you sum the outputs wet and dry, you expect to hear a combination, but because one output is inverted you get a cancelling effect when the inputs are at the same level. The resulting sound is basically the difference between the two inputs. You need to invert the wet sound to get it back in phase before inputting it to the mixer.

Hoping this helps.

Tom.... :)

YES! That was it, thanks for your time.

I modified a “blender” circuit so the RETURN op-amp is inverted and now the transition from one sound to the other sounds great!

Theres one more thing, as you can see the RETURN part has also been amplified a lot to give it more punch and also I put a capacitor there to lower the noise it makes.
The effect is very loud, I like it very distorted as it is, but would like to lower the volume a little, so I added the part circled in red to lower it, but no matter what resistor value I use, it’s useless. Doesn’t get lower.
Do you know how I can do this?

PD: I attached an mp3 sample, it’s starts without the effect and then it gets boosted

bblender mio.gif

low boost kick.mp3 (660 KB)

Hi, good hear you have got it sorted. The gain of the return amp is governed by the value of the 470k resistor between pin 13 and 14, making it 100k will give it a gain of 1. So decreasing the value of this resistor will drop the gain.

Tom...... :)

Yes, I know! the thing is that I like the sound as it is, that gain of 4 of so that now has (100k and 470K) it's making it distort, if I lower the gain it sounds cleaner. It's like on a guitar pedal you can lower the GAIN and you can lower the VOLUME, right? Well, I would like to lower the volume

TomGeorge: Hi, good hear you have got it sorted. The gain of the return amp is governed by the value of the 470k resistor between pin 13 and 14, making it 100k will give it a gain of 1. So decreasing the value of this resistor will drop the gain.

Tom...... :)

If these are normal op amps, the 470k resistor should have NO effect on gain.

If you want to decrease the overall sound level, but keep the current distortion level, just put a resistive voltage divider on the output.

Hi, okay so that op-amp is providing your distortion.

As Ninja says, put a potentiometer on the output of the op-amp, 50K would do the trick.

Tom...... :)

I was thinking about the potentiometer, the thing is that I don’t want to have another pot in order to save space.
So, the thing I did encircled in red, isn’t that the same as adding a fixed volume pot?

Pancra85: I was thinking about the potentiometer, the thing is that I don't want to have another pot in order to save space. So, the thing I did encircled in red, isn't that the same as adding a fixed volume pot?

No, because you only have one resistor. You need two to make a voltage divider.

Jiggy-Ninja:

Pancra85:
I was thinking about the potentiometer, the thing is that I don’t want to have another pot in order to save space.
So, the thing I did encircled in red, isn’t that the same as adding a fixed volume pot?

No, because you only have one resistor. You need two to make a voltage divider.

Ahhhh, yes, you are right!

Well, after tingling for several hours with some circuits I found online (mainly Bass Blender by Sean McLennan) I am happy with this effect.
the input goes to a low pass filter (top left) then gets boosted by two (top-right) and gets mixed with the original input.
I also recorded a bass and I think it could be a bass stompbox (or part of)

Bass Booster (Tarci) con bajo.mp3 (1.12 MB)