How hard would it be to make an eq pedal?

[DazH]

I'd really like to try making a "simple" bass/middle/treble/volume control effects pedal to play around with - I find slider switch ones just a pain in the arse to manipulate.

if I bought a little enclosure - 4 pots, a battery clip, led & bezel & a couple of mono jacks & a switch - would it be plausible for a total novice like me to make something of it?

I'd like to learn more about electronics & figured it might be a nice relatively cheap way to do so.

I'm guessing it would be mostly playing around with capacitors to see what rolls of the right amount of bass/treble or whatever?

Any amp builders/techs - i'd love to hear from you, i'm guessing it's the same theory.

Daz.

 

[ImmortalSix]

Re: How hard would it be to make an eq pedal?

Here's a schematic for a 6-Band Graphic EQ

http://www.generalguitargadgets.com/pdf/ggg_eq6b_instruct.pdf

I know you're looking for a 3-Band Parametric EQ, but you could get a great starting point here

Link to all documents related to the instructions

 

[Rich_S]

Re: How hard would it be to make an eq pedal?

Sounds like you only want three bands, but with fixed frequency centers, unlike the parametric. Building it shouldn't be too hard - you're basically looking for a TMB tone stack similar to that in any guitar amp.

The problem is, TMB tonestacks lose a lot of signal, so you need a buffer/booster stage before, and probably a buffer after to prevent tonesuck. So, it just got more complicated.

I considered building just such a pedal for my mag-pickup acoustic about a year ago. Then I found this:

http://guitars.musiciansfriend.com/product/Dean-Markley-DME3-Outboard-Preamp?sku=180090

It's a well-built pedal, on par with MXR or better. For 80 bucks, designing and building one doesn't seem worth it.

P.S. Also try out the BYOC Tri Boost. Depending on your needs, it might do the trick.

 

[DazH]

Re: How hard would it be to make an eq pedal?

Thanks mate, most of it is beyond me but i'l see what I can make of it. I'm only used to passive electronics in guitars. I'm guessing I could make a passive pedal? I could roll off & cut frequences but I wouldnt be able to add/boost frequencies or volume.

Edit: Cheers Rich - you're right, there are likely some excellent ones on the market, I just fancied playing around with one myself, purely from a hobby point of view.

 

[cream123]

Re: How hard would it be to make an eq pedal?

this might be slightly on the tougher side. its not too bad tho


http://runoffgroove.com/mreq.html

 

[cream123]

Re: How hard would it be to make an eq pedal?

this might be more of what you are looking for:

http://runoffgroove.com/tonemender.html

 

[DazH]

Re: How hard would it be to make an eq pedal?

Thanks cream, that's more complicated than I need but i'm sure if I sit down and concentrate I could pull out the bits I need.

 

[cream123]

Re: How hard would it be to make an eq pedal?

yeah, those are really good ones. altho they have a few extra pieces here and there, i think you could do it if you just sat down and worked with it

 

[NoOnesFang13]

Re: How hard would it be to make an eq pedal?

this might be more of what you are looking for:

http://runoffgroove.com/tonemender.html

well lets see if i have the parts laying round, this thing is freaking cool.

 

[NoOnesFang13]

Re: How hard would it be to make an eq pedal?

sweet i found an op-amp from a crate bass amp i took apart, i will report back

 

[DazH]

Re: How hard would it be to make an eq pedal?

I'm having trouble figuring out these true bypass 3pdt switches - how do they work exactly? they have 9 tags - I think it goes:

is that right?

Edit: The red lines being the live connections to each other & the blank squares not working at all. Or do they not connect to each other at all (i.e individual)? or connect in a different way?

 

[ratherdashing]

Re: How hard would it be to make an eq pedal?

I'm having trouble figuring out these true bypass 3pdt switches - how do they work exactly? they have 9 tags - I think it goes:

is that right?

Edit: The red lines being the live connections to each other & the blank squares not working at all. Or do they not connect to each other at all (i.e individual)? or connect in a different way?

Yes, you have it pretty much right. The center poles are connected to either the bottom or top poles depending on what position the switch is in.

 

[NoOnesFang13]

Re: How hard would it be to make an eq pedal?

what value pots should i use? for this pedal that is
http://runoffgroove.com/tonemender.html

 

[playas]

Re: How hard would it be to make an eq pedal?

what value pots should i use? for this pedal that is
http://runoffgroove.com/tonemender.html

According to the circuit diagram and the link at the bottom, they should be:
Treble 500K linear taper
Middle 100K Audio or Log taper
Bass 500K Audio or Log taper
Level 500K Audio or Log taper

...assuming the web site is US based which it appears to be.

http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=174&Itemid=44

 

[DazH]

Re: How hard would it be to make an eq pedal?

I understand the need to change between audio/log & linear pot tapers to change the way the wiper shunts whatever signal to ground but what's the idea behind choosing different value pots i.e 100k / 500k?

What should I be thinking about when choosing the pot value for say treble/middle or bass & why? what affect will it have? - I always thought they just increased treble as you raised the value.

 

[DazH]

Re: How hard would it be to make an eq pedal?

Still havent figured out the answer to the above question. Also, how does the 9v input and battery connection work?

Do you connect the positive of the battery clip, to the positive of the 9v psu input? - if you connected a battery & then a 9v psu - would this mean 18v was going through the circuit? or does that make it parallel & equal 9v again?

Daz.

 

[Gr8Scott]

Re: How hard would it be to make an eq pedal?

I don't understand your question DazH. You use what they have listed if you want the range they suggest for this effect. If you want more range, buy larger valued pots. If you want less range, buy smaller valued pots. It makes the most sense to buy the values that they suggest IMHO if you don't already have them.

 

[DazH]

Re: How hard would it be to make an eq pedal?

i'm just mucking around trying to make my own basic pedals so I can understand what's going on is all. I'm not following the previous examples currently. All I need to know is what you're describing as range, I guess.

I assume the higher value the pot, the "wider" the scope & more precise the tone change is. Like a 250k pot will give you [tone1 - tone2 - tone3] turning the pot from one end to the other - whereas 500k doubles the scope & gives you [tone1 - tone1.5 - etc] but this could make it more difficult to dial in since they turn the same amount of real world distance?

I've probably got that wrong on all accounts though, heh.

 

[cream123]

Re: How hard would it be to make an eq pedal?

I understand the need to change between audio/log & linear pot tapers to change the way the wiper shunts whatever signal to ground but what's the idea behind choosing different value pots i.e 100k / 500k?

What should I be thinking about when choosing the pot value for say treble/middle or bass & why? what affect will it have? - I always thought they just increased treble as you raised the value.

the main reson is how much range you will have. also some values just don't change much past a certain point. it gets to a point where its not usable anymore.

Still havent figured out the answer to the above question. Also, how does the 9v input and battery connection work?

Do you connect the positive of the battery clip, to the positive of the 9v psu input? - if you connected a battery & then a 9v psu - would this mean 18v was going through the circuit? or does that make it parallel & equal 9v again?

Daz.

what you have to do to get the full 18v is attach the positive of the adapter to the negative of the battery. then the batteries positive is 18v+ and the adaptors - is gnd.

or you could attach the ground between the positive of the adapter and the - of the battery to get a ground. and then you have 18v + and 18v-, giving you 36v as your voltage swing...meaning more headroom before distortion. however this technique will only work with op amps and other linear devices, not transistors. just a heads up.

the second par is if you are using op amps and a decent starter for how to get - and + voltages. read more if you are using op amps. becausee if you are using op-amps, thats the way to go on clean boost stuff like this.

you could also just use two batteries.

 

[cream123]

Re: How hard would it be to make an eq pedal?

i'm just mucking around trying to make my own basic pedals so I can understand what's going on is all. I'm not following the previous examples currently. All I need to know is what you're describing as range, I guess.

I assume the higher value the pot, the "wider" the scope & more precise the tone change is. Like a 250k pot will give you [tone1 - tone2 - tone3] turning the pot from one end to the other - whereas 500k doubles the scope & gives you [tone1 - tone1.5 - etc] but this could make it more difficult to dial in since they turn the same amount of real world distance?

I've probably got that wrong on all accounts though, heh.

ok so lets look at a voltage divider first. diagram 1

ok so if you look at the schematic and the equation together, you will see that there are two resistors, R1 and R2. and there is an output between them. now if you have a value of 10 for R1 and a value of 20 for R2 and a value of 9v for Vin


so lets plug stuff in
Vout = R2/(R1+R2)*Vin

Vout = 20/(10+20)* 9v

Vout = 6v

ok so what did we notice there?
there is a ration of 2:3 if you have those values. so the answer was two thirds of the value of 9v....6v

ok so lets try 10 and 10 and 9

10/(10+10) * 9 = 4.5 right?

so what am i getting at? in volume controls, the wiper is your out, the Vin is one of the outside lugs, and the gnd is the other outside lug.

so if you have 1M ohm pot vs a 500k ohm pot, what happens? well you get more range of values, but you also get less precision. you can also install a trimpot in there of a large value like 1M or something, (find the value with this page and using the equations on the high and low pass stages.) and then throw in a smaller value pot to adjust it to your liking.

a bit long winded....but do you get the idea.

oh and you could just use the big muff pi tonestack modified for bass and treble controls and throw a gain stage infront of and after it with as little distortion as possible....

i might throw a schematic up later if you'd like