The gain of the op-amp is linear, regardless of the supply voltage. So, if you have a lower voltage supply you will push the op-amp into clipping sooner than you would with a higher voltage. In other words, the lower supply voltage will decrease the op-amp's clean headroom.
For example, if you have an op-amp set to a gain of 50, give it power supply of +/-4.5V (9V), and give it an input signal of +/-100mV, you should get an output signal of 100mV * 50 = 5V. However, since you only have 4.5V on the rail, the output will be clipped. Now if you have a second stage but this time you're putting +/-4.5V signal to the input, loads of clipping. Two stages with a gain of 50 each would be a total gain of 2500, which is pretty crazy. Go for it!
For example, if you have an op-amp set to a gain of 50, give it power supply of +/-4.5V (9V), and give it an input signal of +/-100mV, you should get an output signal of 100mV * 50 = 5V. However, since you only have 4.5V on the rail, the output will be clipped. Now if you have a second stage but this time you're putting +/-4.5V signal to the input, loads of clipping. Two stages with a gain of 50 each would be a total gain of 2500, which is pretty crazy. Go for it!
MXR Distortion Plus uses a non-inverting amp, but this shows how you can use the DC offset idea. Notice the voltage divider made with 1M resistors at the top, feeding the + input. I made several designs based on this one back in high school. This is actually a very good, very simple design to start from.
An externally hosted image should be here but it was not working when we last tested it.
Just do a google search for "MXR Distortion plus schematic" and you'll find it.
All you want to do is create a 4.5V DC offset for your input signal. So a 50% voltage divider using 100k or higher from the 9V rail, attach it at your op-amp signal input. Doesn't matter if you're using inverting or non-inverting, just offset the one that your input signal goes into. Don't forget about the DC blocking capacitors on input and output.
All you want to do is create a 4.5V DC offset for your input signal. So a 50% voltage divider using 100k or higher from the 9V rail, attach it at your op-amp signal input. Doesn't matter if you're using inverting or non-inverting, just offset the one that your input signal goes into. Don't forget about the DC blocking capacitors on input and output.
Generally speaking the first stage of a guitar preamp/pedal should be a "Non-inverting " stage ......
In a inverting curcuit (post 13) the input impedance (R in) is part of the gain equation so you will get varying gain depending on what guitar you are useing which isn"t desireable and forces you to use high value resistors in the feedback loop to get a lot of gain which introduces resistor noise .....
The first stage should allways be a high impedance non-inverting stage , after that you can use inverting stages because the output impedance of the first stage is constant and low , I find it best to keep the output the same phaze as the input.......
There are different ways to get different distortions sounds useing diodes , You can use different diodes and in different configurations in the feedback loop or on the output of the opamp , you can even use Mosfets as diodes and even tubes as diodes for distorion .....
Remember that the diodes will clip the voltage at a different voltage depending on the type of diode which can limit your output volume especially if useing germanium diodes ......
Generally speaking every guitar curcuit should use a Fet input opamp as opposed to a BJT opamp , fet opamps have a high input impedance which is needed for guitar ......
just trowing out random related info .....
Cheers
In a inverting curcuit (post 13) the input impedance (R in) is part of the gain equation so you will get varying gain depending on what guitar you are useing which isn"t desireable and forces you to use high value resistors in the feedback loop to get a lot of gain which introduces resistor noise .....
The first stage should allways be a high impedance non-inverting stage , after that you can use inverting stages because the output impedance of the first stage is constant and low , I find it best to keep the output the same phaze as the input.......
There are different ways to get different distortions sounds useing diodes , You can use different diodes and in different configurations in the feedback loop or on the output of the opamp , you can even use Mosfets as diodes and even tubes as diodes for distorion .....
Remember that the diodes will clip the voltage at a different voltage depending on the type of diode which can limit your output volume especially if useing germanium diodes ......
Generally speaking every guitar curcuit should use a Fet input opamp as opposed to a BJT opamp , fet opamps have a high input impedance which is needed for guitar ......
just trowing out random related info .....
Cheers
voltage divider bypass tonestack? EQ the clean sound?
mainly all the types of circuits i missed and best order ?
how can i add BASS boost. contour so forth,. ? what is the best way to introduce a relay into the input?? and connecting it to a female plug????? sound to plug relay.??
is a tuner a simple circuit to incorporate? tap tempo????
mainly all the types of circuits i missed and best order ?
how can i add BASS boost. contour so forth,. ? what is the best way to introduce a relay into the input?? and connecting it to a female plug????? sound to plug relay.??
is a tuner a simple circuit to incorporate? tap tempo????
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Wow, that's some serious scope creep. haha...
You have enough questions that I think it might be best for you to browse some examples. Check out Schematic Heaven to get ideas from other effect pedals.
You have enough questions that I think it might be best for you to browse some examples. Check out Schematic Heaven to get ideas from other effect pedals.
I used too used the MXR+ distortion circuit with one gain stage after it.
then after that I used precision full wave rectifier with a mix control.
I used 1n34 germanium diode cilpping diodes on the first two stages.
Other versions I used 1N914 's and led's, But I liked the 1n34's the best.
I don't know were my final schematic is at the moment otherwise I would post it.
Using a TL074 I also used one stage to drive a 4013 CMOS Dual D Flip Flop as an octave divider.
It was a killer little unit as it covered four octaves and it did a excellent job of not mis-triggering.
I first built it on a protoboard and plugged and played the coupling and feed back capacitors until I got the sound I was looking for.
it was very fussy with a rich tone and had a lot of gain.
Using the TL074 it was the opamp to use of the day and was nice and quiet compared to the more common LM324 as it had almost no hiss at all for the amount of gain that it had.
It had a good tone and I rarely used it through any eq.
jer
then after that I used precision full wave rectifier with a mix control.
I used 1n34 germanium diode cilpping diodes on the first two stages.
Other versions I used 1N914 's and led's, But I liked the 1n34's the best.
I don't know were my final schematic is at the moment otherwise I would post it.
Using a TL074 I also used one stage to drive a 4013 CMOS Dual D Flip Flop as an octave divider.
It was a killer little unit as it covered four octaves and it did a excellent job of not mis-triggering.
I first built it on a protoboard and plugged and played the coupling and feed back capacitors until I got the sound I was looking for.
it was very fussy with a rich tone and had a lot of gain.
Using the TL074 it was the opamp to use of the day and was nice and quiet compared to the more common LM324 as it had almost no hiss at all for the amount of gain that it had.
It had a good tone and I rarely used it through any eq.
jer
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ya i kinda hit you with too many at one time; im in ITT and they dont explain how it works like you do. You should think about a lesson channel on youtube. the opamp is doing almost all the work in mxr. is that how the analog pedal industry .. opamps.
Is it smart to run a JFET into a op amp? what does this do ?
Is it smart to run a JFET into a op amp? what does this do ?
Sorry, I didn't mean to skate away from your questions, I just wanted you to see all those schematics if you hadn't already. There are lots of good ideas to be found and blended to get what you want.
Definitely op-amps are the most popular device for simplicity and flexibility. You can do whatever you want. You can buffer with JFETs, BJT's, whatever. As Minion pointed out (I totally forgot about this point, been in tube land lately) you need to be aware of input impedance. You don't want to create any terribly mismatches. You could even buffer with an op-amp and drive a JFET for the overdrive sound. I've seen a few pedals like that on Schematic Heaven.
Definitely op-amps are the most popular device for simplicity and flexibility. You can do whatever you want. You can buffer with JFETs, BJT's, whatever. As Minion pointed out (I totally forgot about this point, been in tube land lately) you need to be aware of input impedance. You don't want to create any terribly mismatches. You could even buffer with an op-amp and drive a JFET for the overdrive sound. I've seen a few pedals like that on Schematic Heaven.
That is a good start for the layout. You can introduce clipping at stage 1/stage 2 either in feedback loop (like tube screamer) or right after the op amp output decoupling cap (like MXR, DOD, etc...) Your input buffer should stay relatively clean and introduce a bit of boost to drive subsequent stages. If you get into hard clipping too early in the stages, you lose sonic detail. Red LEDs give a nice crunch, I like the older inefficient types, they have a softer edged clip. Subjective opinion (!)
This is an interesting point. Like I said earlier I never really played around much with diodes, just had some germaniums lying around and they sounded good to me. I wonder about slower/faster LEDs, or infrared LEDs.
Damn you guys, you're going to get me back onto the pedal design boat instead of the tube amp design boat that I've been riding this year. hahaha...
Oh yes I know exactly what you mean! I did a thread here on a distortion pedal build, and ended up using a DIP switch with various clipping elements..that way I could ''taste test'' them in all different combos. Even from one playing style to another I had my different personal preferences. But I like the layout of a prebuffer/stage 1 / eq/stage 2 and post filter..as that give quite a lot of flexibility from my experience. I had built a clean boost/buffer pedal which I always run in front of the overdrive and it fattens everything up nicely.
It certainly helps to be able to evaluate different tones. Freeminimika is developing the circuit for a certain signature tone, so there needs to be a bit of tuning of filter values, gains and clipping methods. I read some online rumours which might be cool to try:
For a ''darker'' tone on the MXR type circuit, you could try piggybacked 741s, literally stacked pin for pin on each. I think it shifts the corner frequency of the hi pass pre-emphasis, adds some power and complexity to the op amp gain circuit.. it is only a few additional cents to build it like that. Or with TL07x could work the same.
For a ''darker'' tone on the MXR type circuit, you could try piggybacked 741s, literally stacked pin for pin on each. I think it shifts the corner frequency of the hi pass pre-emphasis, adds some power and complexity to the op amp gain circuit.. it is only a few additional cents to build it like that. Or with TL07x could work the same.
From a player point of view, I shoulda checked out nu-metal sound a bit more. I still think your layout is good. you need to look at scooping out mids after the buffer pre stage. Your low E to low A strings need to be crunchy, tight and hard clipped. A lot of symetric clipping going on down there. Little softer in the mids so the EQ scoop should lessen the clipping effect in later stages. But you need to look at a serious bottom end boost cause that is where it is going on. highs are clipped but more even harmonics, asymetric clipped. Doozerdave, talking about multi stage, that is how you do it. Introduce the right amount of overdrive clipping in the different stages with the right tone shaping.
I would have a look at Thor (runoffgroove.com) and it has the bass boost circuit. From the sound clips I heard, it sounds like what you are going for , but maybe a generation of metal before. Some minor tweeks, maybe play with that and tune the EQ to taste. Or use as a basis for your own sound.
I will say this respectfully, yes a high gain clipping circuit is in order but no matter what style you play: if you clip ''across the board'' you will get a one dimensional sound, basically a square wave. Where you place the EQ and pre or de-emphasis will matter a lot to the sound you are after.
I would have a look at Thor (runoffgroove.com) and it has the bass boost circuit. From the sound clips I heard, it sounds like what you are going for , but maybe a generation of metal before. Some minor tweeks, maybe play with that and tune the EQ to taste. Or use as a basis for your own sound.
I will say this respectfully, yes a high gain clipping circuit is in order but no matter what style you play: if you clip ''across the board'' you will get a one dimensional sound, basically a square wave. Where you place the EQ and pre or de-emphasis will matter a lot to the sound you are after.
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