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Sallen Key Low Pass Filter, bandpass filter

bertus

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Hello,

I found the failure. In the 7000 Hz filter R12 was 43 Ohms in stead of 43K.
Now R13 can be adjusted to 820K and I get a peak of 7.4 Volts for the 7000 Hz filter:
Plot 7000 Hz corrected.png
The green line is the output of the preamp.
I have also attached the wav file I used.

Bertus
 

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  • 7000Hz_B.wav.txt
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Maglatron

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Gosh!! So is the preamp and amp ready to build now? Just running sims now, so sorry for the mess around! top guy!
 
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Maglatron

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so, I went to build some of the pre-amp and realised that I have 0 non polarized capacitors except the ones for this filter part and they were for the 16000Hz version and do not go above 0.1uf whereas I need the 10uf! did not do much soldered in a socket for the op-amp chip and stuck some leads to a mic nothing to get jolly about is it posible to use electrolytic I read on the internet that sometimes you can!! what are your thoughts the circuits are all working as expected now in spice thank you so much!1702574200344.png
 
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Maglatron

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I'm going to purchase some bits from mouser BAT43's and need at least 4 x 10uf, make that 6 with the buffer REF GND circuit and I need 4 of those so thats 12 so I'll probably get 15-20 10uf! I want to build up a little bit of a list first though because the postage is relativly high!!
 

bertus

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Hello,

Any 16 Volts electrolitic or tantal capacitors will do.
In the amplifier there is not much voltage on the capacitors.
For the powersupply of 12 Volts and the ref voltage, the 16 volts capacitors will do.

Bertus
 

Maglatron

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ok I have the electrolytics 16v im not certain of which way to orient some of them the can you annotate this pictures please for the 4 caps and the 2 in the buffer I'm pretty sure I can guess but need to make certain thank you!! no I'm taking out C18! and putting the mic in there!1702578488628.png1702578457083.png
 
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Maglatron

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Ok cool, I will build the pre-amp and the amplifier when I next get chance, and will upload a picture of it so you can see some progress that you helped me with thanks again for your efforts in helping you have been invaluable to this part of my project, cheers
 

Maglatron

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hello, I've printed out loads of strip board and am arranging the components so far I'v used one TL074 quad op-amp to make the preamp two buffer REF circuits and the first of the envelope detectors , my question is this just to clarify a buffer can be ok for 4 entire filters asin band 1 2 3 and 4 or is it just good for 4 opamps in the singular filters if you get what I am saying? thanks!! also ordered the BAT43's and my caps have come for the 45Hz to 7000Hz filters so now I am all set just got to find the time to build getting there slowly slowly!
 
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bertus

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Hello,

Do you use sockets for the chips?
Wich type of sockets do you use?
ic-socket-contact-types.gif
The turned pin contact version is much more reliable.

Bertus
 

Maglatron

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ok will bear in mind when I purchase more! No I have the dual leaf ones atm so yeah about the buffer REF, four op-amps or four entire filters?
 

bertus

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Hello,

I have the idea that one REF amp can drive 4 complete filters.

Bertus
 

Maglatron

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Ok cool that's good thanks you will resume disigning the strip board schematic when I have the motivation, soon I hope! So made a start on the filters now it's pretty plain sailing much easier that the preamp
 
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Maglatron

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Anyone know where to get E96 assortment of every resistor in the range?
 

bertus

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Hello,

The largest kit I found has 130 values:
The value list:
1 ohm1.2 ohm1.5 ohm1.8 ohm
2 ohm2.2 ohm2.4 ohm2.7 ohm
3 ohm3.3 ohm 3.6 ohm3.9 ohm
4.3 ohm4.7 ohm5.1 ohm5.6 ohm
6.2 ohm6.8 ohm7.5 ohm8.2 ohm 9.1 ohm
10 ohm12 ohm15 ohm18 ohm
20 ohm22 ohm24 ohm27 ohm
30 ohm 33 ohm36 ohm39 ohm
43 ohm47 ohm51 ohm56 ohm
62 ohm68 ohm75 ohm 82 ohm91 ohm
100 ohm120 ohm150 ohm180 ohm
200 ohm220 ohm240 ohm270 ohm
300 ohm330 ohm360 ohm390 ohm
430 ohm470 ohm510 ohm560 ohm
620 ohm680 ohm 750 ohm820 ohm910 ohm
1k ohm1.2k ohm1.5k ohm1.8k ohm
2k ohm2.2k ohm2.4k ohm 2.7k ohm
3k ohm3.3k ohm3.6k ohm3.9k ohm
4.3k ohm4.7k ohm5.1k ohm5.6k ohm
6.2k ohm 6.8k ohm7.5k ohm8.2k ohm9.1k ohm
10k ohm12k ohm15k ohm18k ohm
20k ohm22k ohm 24k ohm27k ohm
30k ohm33k ohm36k ohm39k ohm
43k ohm47k ohm51k ohm56k ohm
62k ohm68k ohm75k ohm82k ohm91k ohm
100k ohm120k ohm150k ohm180k ohm
200k ohm 220k ohm240k ohm270k ohm
300k ohm330k ohm360k ohm390k ohm
430k ohm470k ohm510k ohm560k ohm
620k ohm680k ohm750k ohm820k ohm910k ohm
1M ohm1.5M ohm2M ohm3M ohm


You can probably simplify the values by choosing the E24 in the tool, as I did in my simulation.

An other kit is at mouser:
This one will cost you much more.
The content is on the first page of the attached PDF.

Bertus
 

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  • LR Series Kit Lists.pdf
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Maglatron

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I think you are reffering to this I don't understand it I see the page you posted is the LR0204

1702744009926.png
 

Maglatron

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nice one thanks, I just realised I have some on order! from ebay
so you know here there are some arbitrary numbers do I just round them to the nearest whole number of resistor that is in the kit of resistors or sholud I mix the values to arrive at the correct values??? intuition tells me to mix!1702744446667.png
 
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bertus

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Hello,

Here is an example with E24 resistors for the 7000 Hz filter:
7000Hz E24 filter.png
This will reduce the number of values for the resistors.

Bertus
 
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