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Christian 16th June 2003 10:34 PM

DIY Equalizer, but really simple

Do any of u have plans for a equalizer one can put in the signal way before the power amp?

I plan to build an amp with an equalizer integrated. I already have a volume control, and I'm pretty sure I can figure out a balance pot, but the bass and treble-control poses more problems.

It needen't be a complicated design, just bass an treble-control would be sufficient, as long as it's easy to build.

I have been looking on this chip
It is a 7 band equ, but it seems too complicated for my brain :)

Best Regards

Jan Dupont 17th June 2003 10:06 AM


I donīt think that you will find anything more simpel than this circuit. In the datasheet you got the components and values for a working system.

A simpel bass and treble control (that donīt destroy to much of the sound) would have the same no. of components.....

Christian 17th June 2003 10:48 AM

2 Attachment(s)
Ok, so I'll go with this circuit.
But I still don't understand two things.

1. Does one have to use all the seven bands, or does it work ok if you just hook 2 band upp and leave 5 floating?

2. What is that amplifier circuit in the diagram(arrow)? and do you really need it. I can't find that circuit M5218 anywhere!! Can I use something else maybe or just skip it?

Rarkov 17th June 2003 11:04 AM

That is an opamp in a unity gain configuration (an input buffer). It is there for stability. I personally wouldn't leave it out, but the Opamp (M5218) could be substituted for a better sounding one (such as an Analogue Devices / Burr Brown item)

I do not believe you could leave the bands floating as they seem to be set frequencies. The bands are far too narrow for just bass/treble. You could leave the central 5 set at 'zero' but I'm not sure it'd sound as you might expect!

Hope this helps,

theChris 17th June 2003 11:27 PM

see in the preamp section. circuts for this.
Figure 2- Input Buffer and Tone Controls

Matttcattt 18th June 2003 05:12 PM

i dont think you can leave them floating... i would use two 50k resistors in series instead of the pots of the controls you want to leave out, and connect the lead from the capacitor to the center of the two resitors (see picture).

Matttcattt 18th June 2003 05:14 PM

2 Attachment(s)

Christian 18th June 2003 06:05 PM


Thanks for the great answers!! I'll do as you say and use resistors as substitute for the the pots.

Now there's only one thing in this schematic that is troubling me, the op-amp. I can't get that specific component, but if you'd know about some other op-amp, preferbly from this list :

it would be great cause then I could get started building!:))
Or, the very simplest thing for me to do would be to entirely leave it out, even though the results probably wouldn't be that great:(

Best Regards,

Jan Dupont 19th June 2003 08:17 PM

This is a standard op amp...
You can use almost any op amp that you have or can (or can get).
Take a look at this (also from ELFA):

This LF356 is either new or high-end, but it is used in many audio applications, and one of my personal favorites...

Happy building;)

peranders 20th June 2003 06:24 AM

You can infact use not all seven bands. Each band consist only of a emitter follower and I don't see why you only just exlude 5 of the bands but then I think make a traditional tone control is better (sounding).

LF356 is an ancient opamp, works though but somewhat noisy.

If you deside to make a traditional tone control, use an OPA134 OPA2134.

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