Notch Filter Design

[ChocoHolic]

Take care with high Q active filters you might find quite high output voltages at the concerned OP amps. Here the concerned OP is the gyrator OP.
For this reason I have to step down the signal first, then notch it and amplify again in the end.
My OP amp choice: OPA2134
For budget solutions the TL072 would also work, but make about 3db more noise.
Forget all bipolar low noise OP amps here. Their input current noise multiplied with the source resistances of this circuit will end up in higher noise. You need a low noise FET-OP.

 

[ChocoHolic]

...

 

[ChocoHolic]

...C2 & C22... large film caps... hm, nice chance to use up lots of old mylar caps, which extracted from scraped TVs 15 years ago.

In order to avoid hum issues I paralleled them by the twisted wire aproach.

 

[ChocoHolic]

I decided to put the notch filters etc. into the same enclosure (reuse of my NAD, which was killed during my last move) with my Rookie amps.
This allows to use the terminals and all unused mechanics. Quite convinient

First the block diagram of the entire signal conditioning board.

 

[ChocoHolic]

....the final board..

 

[ChocoHolic]

....Ok...OK... it's quick'n dirty, but I was impatient.
Short interuption of my class D project in order to get proper bass NOW.
And frankly speaking, up to now these breadboard protos usually work pretty fine, even langer than 10 years of daily use.

 

[ChocoHolic]

My ears say: Yes, yes, yes... !


Arta says:

 

[Baldin]

Arta Measurements

Hi There

I'v finally got around to do some measurements.
We'll as I thought there is a lot to be done in my room if I wan't some better sound.

You can see my measurements of left side speaker (set to small) + subwoofer here .... not so pretty

 

[Baldin]

Here I have tuned the parametric equalizer to max Q and max cut at 70 Hz where there is a big room mode. Clear improvement, and easy to hear, but I need to do a lot more than can be done with electronics

From first measurenment to second, I moved the mic (as I did some other measurements) so the improvement might be somewhat bigger!

 

[Baldin]

Here is a near field measurement of the sub alone .... well that's kind of cool I think

 

[Baldin]

Here is a measurement of max boost and max Q ... well, the circuit actually works as simulated and intended

 

[ChocoHolic]

....yes, good bass is difficult. Very nice to see you on a similar path like myself

Your sub alone.... Yes, cool deep.
Is it a sealed design with LT? Theoretical roll off?
I have extended my sealed subs by LT down to a theoretical roll off at 12Hz.

 

[Baldin]

Yes it's a 12" Peerless XLS in a 19 l sealed box, with a LT to take it to 14,5 Hz Bessel.
I'm using my full bridge HIP4080 SODA of 400W to power it.
Still haven't got round to put it all into a nice looking enclosure though

 

[ChocoHolic]

Pretty nice!

I am playing with two 30 litre sadhara cubes.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=55880&highlight=

Up to now powering still with my old 8x150W monster, means 600W for each cube.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=36469&highlight=

How is this going on?
http://www.diyhifi.org/forums/viewtopic.php?f=22&t=1321&sid=e526f56d6c90a12a6f5d1f37075055e9

 

[Baldin]

Hi ChocoHolic

Nice amp and sub

Well I'm waiting for a new PCB for a new class-d amp based on IR2110. I have done a lot of work to minimize ESD ... we'll see how it works out

 

[ChocoHolic]

ESD or EMI ?
....proper layouting for high power class D is something that I still have to learn... ...one of the next steps in my own projects...

Hope your aproach will satisfy you!

 

[Baldin]

Sorry ... EMI .... yes, layout is one of the most important components in high freq high power circuits .... can't say I'm any good at it though