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JensRasmussen 4th June 2004 10:56 PM

Parametric EQ as mox sidekick

As some of you may know, I have been working on an adjustable EQ as a sidekick to the Active filter two boards. I think I have found a way to make a real parametric EQ, with completely separately adjustable Gain, Q and fc. If anybody is interested Im offering to create the artwork for this module also, and later there can be a group purchase.

Let me know what you think and what the options on the boards should be.



JensRasmussen 5th June 2004 08:55 AM

My main reason for wanting a real parametric EQ as opposed to the wery nice nodule posted by moamps is that I consider the mox board along this EQ board as tools when developing active filters for speakers.

The problem as I see it with moamps EQ, is that I think it is difficult to find out what parameters the EQ has. This in turn makes it impossible to recreate the EQ on a smaller board for the final filter.

I have been trained at at place where they use the DP226 digital filter, and here you just set your parameters listen, tweak listen some more, and when you are happy with the overall sound from the speakers, you build your analogue filter according to the specs from the digital prototype.

This way, the first analouge filter is pretty close to what you want

I want to make an analogue DP226 to make sure that there is an easy transfer from listening prototype to final filter.

That said, Im not an expert speaker builder Im a total newbie but I know signal processing and hope to get the Loudspeaker guys to help out when it comes to all the acoustical questions I have


netgeek 5th June 2004 04:39 PM

You are probably already very familiar with the common circuits out there (in fact it sounds like you already have designed something) - but the following may be of interest anyway (particularly the single stage shown as Figure 3):


Ed LaFontaine 5th June 2004 04:56 PM

The box gets bigger
I've subscribed to this thread and look forward to the development. Has the interface with mox or the "architecture" been determined yet? What are the variables we can influence?

I think I will want to incorporate both in one cabinet.

JensRasmussen 5th June 2004 10:15 PM


Thanks for the link, in fact the circuit I have made is very similar to the one found in figure 3.

I plan to make the EQ a module you can insert anywhere in the signal chain in your box of filters. The input will be gain, Feq and Q, all of witch will be 100% independent.

I hope to build a prototype on breadboard pretty soon when this is done Ill post results.

In the mean time, please keep the ideas coming, as Im not set on a design yet.


promitheus 5th June 2004 11:46 PM


its very interesting to have a parametric equalizer. I think all parameters like frequency, gain and q should be easy to set.
Would such a circuit work with the discrete opamp?

tiroth 8th June 2004 05:14 PM

Bump. As long as there is as much space around the opamp pads as is on Jen's MOX boards, the discrete opamp would fit.

As usual, I think there are probably a lot of interested people who have absolutely nothing to say on the issue at the moment. (me included!) So we'll all look forward to more details as the prototype gets hashed out--it is much easier to offer (hopefully constructive) criticism than to come up with a design.

JensRasmussen 8th June 2004 07:16 PM

Hi Tyler, and the rest of you :)

Im working on a proto single layer PCB to verify that everything is working as planned. I hope the have the layout ready in a few days, and post some measurements by the middle of next week.

But my speaker project is taking most of my spare time at the moment.

Ideas about configuration / schematics are still more than welcome


JensRasmussen 9th June 2004 11:12 AM

2 Attachment(s)

Here are some graphs of what I imagine the Q of the filter should be like. Please comment

Ignore the gain and freq, as these will be adjustable too


mwmkravchenko 16th June 2004 04:04 AM

How Goes it????
Is the circuit still in the works????


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