5-Band Fully Parametric EQ

[gigimarga]

I'm back in town but with limited email access at home.  please feel free to post any build reports or comments as you work through it.  I wish I could have verified it already but I've just been so busy with school.

gigimarga, I don't have any notes on Cap values for guitar unfortunately, however the math is very simple and comes directly from an RG article.  http://geofex.com/article_folders/eqs/paramet.htm

It's in the section around the 3rd schematic from the top.  Basically you fiddle with values until you get the range that you want.  I used an excel file, but I'm not sure where It is at the moment.  I found that a bit of overlap of each one works best.

Thank you aziltz!
I have a big problem with it: at any settings, I hear a high frequency whistle (it's not boxed yet)!!
I used ICL7660 instead of MAX1044 and NE5532 for op-amps...can these substitutions to be a problem?

[aziltz]

I really don't know about the MAX1044 substitutes, I haven't used the MAX with this circuit yet, but the 5532s should be fine.

[gigimarga]

I really don't know about the MAX1044 substitutes, I haven't used the MAX with this circuit yet, but the 5532s should be fine.

Thx!

[aziltz]

Thank you aziltz!
I have a big problem with it: at any settings, I hear a high frequency whistle (it's not boxed yet)!!
I used ICL7660 instead of MAX1044 and NE5532 for op-amps...can these substitutions to be a problem?

gigimarga, did you get this problem sorted out?  I haven't yet had time to build and verify this layout, and I'm wondering if others have.

[gigimarga]

Thank you aziltz!
I have a big problem with it: at any settings, I hear a high frequency whistle (it's not boxed yet)!!
I used ICL7660 instead of MAX1044 and NE5532 for op-amps...can these substitutions to be a problem?

gigimarga, did you get this problem sorted out?  I haven't yet had time to build and verify this layout, and I'm wondering if others have.

The layout it's OK, but I can't solve the problem...I was (and still I am) very busy at my job, so I have no time for DIYing

Thank you very much!

[aziltz]

Would anyone be interested in attempting to verify this board and project for me?  In exchange, I would provide you with an etched board of this layout.

[aziltz]

Would anyone be interested in attempting to verify this board and project for me?  In exchange, I would provide you with an etched board of this layout.

any takers for some co-labor-ation?

[jkokura]

I would Austin, but I gots no money for parts...

I need a restock on caps (100+ bucksish), and I have no pots for it.

Jacob

[Taylor]

I've had a board for a while, haven't had time to build it up, but I'll see if I can get it done tonight or tomorrow. I won't need an etched board, so if I manage to get it done you can just donate a buck or 2 to the charity of your choice in my honor. 

Anything I'm supposed to be looking out for? Have you not built this up at all?

[aziltz]

thanks for the gesture taylor.  I have not had a chance to build myself one in its entirety.  The same EQ bands have been built in prior iterations, but the 18v power supply is a new addition, but also a borrowed design from previous work.  I guess I'm just wondering if there's any really minor issues with the layout, since I will not have a chance to build it for some time.

[Taylor]

Didn't get too far with it yet, but quick thoughts:

I felt the pads were a little too small. Teeny pads like this are ok on plated boards, because the solder just wants to slick onto those pads, but for home-etched stuff I find pads this size a little difficult to solder to.

C1, I think from memory, the input cap which sits below the leftmost opamp, doesn't have enough room. The 1uf box film caps I have are about .24" thick. I always allow this amount of space for non-polar caps that are bigger than about .33uf in value.

I personally don't object to the .3" size for resistors, and I prefer it for cramming more stuff in less space, but I did get some complaints about that on some of my boards. For me, it was necessary and I'll keep doing it in order to get big circuits in tiny boards, but I just thought I'd throw it out these in case it's not something you've thought about. It requires a little more attention to lead forming when populating the board.

Probably more comments to come...

[aziltz]

thanks for those suggestions Taylor.  I had already started on another revision of the layout before my computer ate my files somehow.  I can't find it anywhere unfortunately.

So it looks like I'll be starting over.  I'm going to keep the 18v Charge Pump, but add an optional 9v and voltage divider Vreft so it can be built with either supply.  I'm also going to add a Buffered Output and get rid of the shelf/roll-off trimmer.

I haven't quite decided if Q controls should go on top or not.  I'm a little torn there.

[MojoFilter]

when this pcb is ready i'm definitely going to have to get at least 2

what i would like to see on it would be the option to have pots for freq, q, and cut/boost for each band, including the shelves, on the outside; i don't care if they're board mounted. also, input and output gain controls would be nice to help with any extreme cutting or boosting that may happen. i like the charge pump. what would a buffered output help with? i'm not against it, just curious

to be fair, i did major in studio production and i'd be running a wide variety of sounds through it as often as i'd use it for guitar, so i'd like more flexibility than most. i don't know anything about pcb design, so i may be asking too much, but i'd love something this flexible in a stompbox format that i can build myself.

[elbandito]

Just wanted to bump this topic up in the hopes that somebody got around to working on this further and *hopefully* verifying it. I've been looking around for a layout for a ParaEQ and this seems to be the one with the most potential. Thanks for the work you guys have already done on this... I look forward to building one myself.

[aziltz]

Ah, sorry I had to put this project aside.  I would like to pick it back up sometime soon.  The most current design still needs some work though.  Not sure when I will have more time for it.

[roseblood11]

I have a big problem with it: at any settings, I hear a high frequency whistle (it's not boxed yet)!!
I used ICL7660 instead of MAX1044 and NE5532 for op-amps...can these substitutions to be a problem?

The MAX1044 and the ILC7660S (not the version without an "S") have a boost function that raises the oscillator frequency above the audio band. Pins 1 and 8 have to be connected.

[sault]

I figured I would plug the online gyrator calculator I threw together a little while ago.

http://awasteofsalt.com/gyrator/


While I wrote it to help me figure out how to tweak a Metal Zone, it works for this type of thing as well. Hoping at some point to update it a little... tighten up some code, make it play better with non-guitar pedal applications... at some point, perhaps.  =)




Sault

[dledbet1]

I realize this is a pretty old post, but i'd be interested in learning what it would take this circuit and run balanced input to and from the circuit, to be used on any general audio I'd like to route through it from a console.