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Old 16th June 2003, 10:34 PM   #1
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Default DIY Equalizer, but really simple

Hi,

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 http://www.elfa.se/elfa/produkter/se/220740.htm
It is a 7 band equ, but it seems too complicated for my brain

Best Regards
/Chris
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Old 17th June 2003, 10:06 AM   #2
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Hi,

I don´t 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 don´t destroy to much of the sound) would have the same no. of components.....
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Old 17th June 2003, 10:48 AM   #3
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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?
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Old 17th June 2003, 11:04 AM   #4
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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)

Edit:
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,
Gaz
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Old 17th June 2003, 11:27 PM   #5
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see sound.westhost.com in the preamp section. circuts for this.

http://sound.westhost.com/project02.htm
Figure 2- Input Buffer and Tone Controls
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Old 18th June 2003, 05:12 PM   #6
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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).
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Old 18th June 2003, 05:14 PM   #7
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oops
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Old 18th June 2003, 06:05 PM   #8
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Hi,

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 :

http://www.elfa.se/elfa-bin/lt.pl?so...860019&1860063

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,
Chris
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Old 19th June 2003, 08:17 PM   #9
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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):
http://www.elfa.se/pdf/73/731/07312366.pdf

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

Happy building
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Old 20th June 2003, 06:24 AM   #10
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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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