xx Band Audio Equaliser

[Flunze]

Hello guys. I want to create a 20 Band EQ for my 900Watt MOSFET Power Amplifier. The only Circuit, that seems possible to me is just crap, cause it would need as many OpAmps as Band's. Just a preview:


I am searching for an alternative, that would not need additional 20 OpAmps - max. 1 OpAmp per channel would be nice.

Is it possible, to split the Audio Signal into 20 Circuits with Resistors, eq them all and than bring them back together?

Just a simple Idea, how it propably could work:



Would that have any effect? Maybe, the Output Level would drop by the Ammount of resistors, so for 2 Equal Resistors, I should amplify it by a gain of 3. Would that propably work?

[poptones]

You're on the right track. http://www.geofex.com/article_folders/eqs/paramet.htm

[Flunze]

Thanks for reply.

Eek, that is very confusing. The first schematic is a simple EQ and the text says, you can add as many bands as you want, by adding filter sections. But I don't realy get, what part of the whole Circuit is the Filter section.

There are 2 10k Pots - well, do I get it right, I have to add this Parts with the Pots all parallel like in the Picture? o.O

And the text says "...up to 31" - does it mean, it will not work with more than 31 Filters? o.O

Will take a look at it tomorrow after work or maybe after waking up.

Thanks so far. I hope, I'll get it done. ^^

[Flunze]

I will do the Version with 1 OpAmp per channel. The only problem there, what OP-Amp can be used best? I want to try some Surface mount stuff, to test my new soldering iron.

I'd love, if you can tell me about a good SMD OpAmp, that has a good quality and is not to difficult to wire up. It also should not cost so much. I mean, the TDA2822M is a Hi-Fi OpAmp - or let's just say, it more is like High-End quality, but how to find something with enought inputs, so I do not need 300 OpAmps, cause they only handle 2 channels?

Can't wait, to do some SMD soldering work. <3
Well, I get money in 1 month... Will have to wait, but I can plan all yet.


Edit:
What about the "TLC 274 CD SMD"?

[poptones]

A 16 band eq would need 4 quad opamp per channel, that's not bad. Why not use the tl084? It's ubiquitous, lower in noise, high impedance, and characterized for both noise and distortion performance.

[Flunze]

Totally love it!!! Only 34 €-Cents. That's awesome. So I can set up stuff like in the first picture, right? Than I later will make a Plan and also a PCB Layout.

But for now... Eek. My Job is calling. 8,5 Hours and I'll be back.

[LEECH666]

You probably already know this page: http://sound.westhost.com/project75.htm

I recently built that equalizer, and it works. I got a little bit of hum in my system but that might be related to my routing / construction. Have to investigate some more when I have the time.

[Flunze]

So, that first 8 Channels are ready designed. It is just a placement idea, it will be changed later. Would something like that be working? The connections are all ready. 8 Channels... 22 to go. I will use a stereo type for the last 2 channels, to not waste any mm of place. Well, how do you guys like this design?





Any Ideas, how to set up the rest, without some ugly cable jumpers? I am thinking of SMD Board jumpers, like I saw them in radios. They would match to a good worked out design - better than any Cable crap.

So what do I need?
-Feedback to the Picture
-An operational amp just for 2 Channels, that matches my TL084's.

[LEECH666]

With only that picture it will be hard to get any kind of help. Use more than one color so that we can see what we are looking at. And include a schematic that matches the design.

This way it's really hard to tell what we are looking at.

The TL 082 is the matching dual op amp to the TL 084.

[Flunze]

How do you like it? The holes are for the Potentiometer Connectors.

Just a very, very, very important question: The scematic wants 100k Pots, but they are expensive in germany. Will something like 10 k work as well?

Also: Do you know, how to get cheap sliding potentiometer? I don't want to use rotating Pots, cause for an EQ it realy would suck a lot. Well, slide potentiometer means a price of between 1.25 to 5 bucks each...

For 32 Bands it is very expensive...


Edit!!!
http://de.mouser.com/ProductDetail/Bourns/PDV20-31M-105A/?qs=sGAEpiMZZMtC25l1F4XBU9NbBl2k%2fHPfMGDbVqHWfl4%3d
What about that? Is this worth it? I mean, 32 Cents is as cheap as possible. It only holds up a few milliwatts, but that is OK, cause I don't want to put it into low resistance, right?

[LEECH666]

Here is my implementation of a 10-Band Equializer + Preamp. It has some silly design faults, but overall it does work.

Sorry I don't know of any supplier of cheap sliding potentiometers. I used round ones, even tho they do suck.

LP0008A = PSU
LP0008B = Preamp + some EQ parts
LP0008C = Filter bank / array

Still in the process of building the Preamp/Equalizer. Fucking metal working sucks if you don't have the right tools (drill press, etc).

[Flunze]

Well, how do you like the Pots I linked in my post? And how do you like my design as a single sided Board? I will change it a bit, but it is almost the final placement.

Most important question to answer: Will any Pot, that has NOT 100k work as well? For example, is my Link with 1000k pots ok? They are not produced any more, so they are only 32 cents per piece. I could live with that price.

[LEECH666]

Not sure. Why don't you sent Rod Elliot an email. He is the guy who came up with the circuit.

I would test it with 10K pots, but I don't have any 10K Pots lying around.

The pot you linked has a resistance of 1M, just so you know.

PDV20-31M-105A = 1M
PDV20-31M-104A = 100K
PDV20-31M-103A = 10K

Florian