Audio Frequency Detection - Page 2 - Electronic Circuits Projects Diagrams Free

synthius · 27th April 2008, 02:12 AM

check this out: Peak Frequency detector

http://www.electro-tech-online.com/e...ecuencies.html

bananasiong · 27th April 2008, 03:33 AM

Hi,
If I'm not mistaken you're cascading two sets of S&K with the Q factor of 0.7071 each, so the result will be Bessel response (Q factor of 0.5). So the roll off is not -24 dB/oct (-80 dB /dec) anymore. For 4th order Butterworth filter with -80 dB/dec roll off, it should be designed according to the polynormial:
(s2 + 0.7654s + 1)(s2 + 1.8478s + 1)
(from Wiki)

synthius · 27th April 2008, 03:42 AM

It is a linkwitz-riley configuration (4th order) which is 24dB/octave/.

bananasiong · 27th April 2008, 03:55 AM

Oh I see

I've got to do lots more reading

audioguru · 27th April 2008, 11:32 AM

The resulting Bessel filter is down -6dB at the cutoff frequency. It eventually reaches 24dB/octave but its cutoff is not sharp.

This type of filter is used in a Linkwitz-Riley speaker crossover network because a highpass and a lowpass add together perfectly (unlike a Butterworth type).

transistance · 29th April 2008, 01:07 PM

how about this bandpass filter? its supposed to allow 60Hz-340Hz. I was playing around with FilterLab. I am not too experienced with multi-stage filters but i think this is a butterworth filter. The only problem is i can not rebuild the circuit, cause i forgot the attenuation values i used. Nonetheless, i think it should work fine with x10-x20 gain preamp.

Ohh and i noticed that i have to be very precise with R values when building multi-stage filters. Correct observation?

Do you think this filter will solve my problem?

COMMENT ON EPE PIC-A-TUNER:
That is some hardcore assembly, i can not follow where they are actually digitally filtering the non-fundamental frequencies.

NOISE REDUCTION:
I'm planning to wrap all my audio carriers with aluminum wire mesh (mosquito screens - i dunno if thats what its called but you kno what i mean). That should help?

NOTE:
I'm using TL084 for opamps and LM386 for preamp.

Thanks in advance,
transistance

transistance · 25th June 2008, 02:30 PM

http://www.schickt.de/data/gimmick/t...K_sch_0.73.pdf

Here is the schematic of a what seems to be a fairly nice digital guitar tuner. Unfortunately the project owner only has the .hex file shared, I was wondering what the use of that comparator was? can anyone share some ideas? Could I use this circuit up to only a certain node before the comparator to achieve my fundamental frequency filtering? Or is the comparator there to capture the first fundamental of the polyphony?

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27th April 2008, 02:12 AM	(permalink)
synthius	check this out: Peak Frequency detector http://www.electro-tech-online.com/e...ecuencies.html

27th April 2008, 03:33 AM	(permalink)
bananasiong	Hi, If I'm not mistaken you're cascading two sets of S&K with the Q factor of 0.7071 each, so the result will be Bessel response (Q factor of 0.5). So the roll off is not -24 dB/oct (-80 dB /dec) anymore. For 4th order Butterworth filter with -80 dB/dec roll off, it should be designed according to the polynormial: (s2 + 0.7654s + 1)(s2 + 1.8478s + 1) (from Wiki) __________________ Superman returns..

27th April 2008, 03:42 AM	(permalink)
synthius	It is a linkwitz-riley configuration (4th order) which is 24dB/octave/.

27th April 2008, 03:55 AM	(permalink)
bananasiong	Oh I see I've got to do lots more reading __________________ Superman returns..

27th April 2008, 11:32 AM	(permalink)
audioguru	The resulting Bessel filter is down -6dB at the cutoff frequency. It eventually reaches 24dB/octave but its cutoff is not sharp. This type of filter is used in a Linkwitz-Riley speaker crossover network because a highpass and a lowpass add together perfectly (unlike a Butterworth type). __________________ Uncle $crooge

25th June 2008, 02:30 PM	(permalink)
transistance	http://www.schickt.de/data/gimmick/t...K_sch_0.73.pdf Here is the schematic of a what seems to be a fairly nice digital guitar tuner. Unfortunately the project owner only has the .hex file shared, I was wondering what the use of that comparator was? can anyone share some ideas? Could I use this circuit up to only a certain node before the comparator to achieve my fundamental frequency filtering? Or is the comparator there to capture the first fundamental of the polyphony?