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Sallen Key Low Pass Filter, bandpass filter

Maglatron

Jul 12, 2023
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I built the preamp today for the 12k i used a 10k and 2k in series and for the 27k I used a 22k and a 4.7k will that be sufficient I can swap it out if not when my other resistors come in the post!!?? I'm not wure which rating ie 12 24 I got because I got my mum to order them, they were off ebay, and I can't use ebay where I am!
 

Maglatron

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so will this leave the cap values the same? I've bought them now! I will write out the new list of resistors tomorrow because I'm knackerd right now, busy day:)
Hello,

Here is an example with E24 resistors for the 7000 Hz filter:
View attachment 62186
This will reduce the number of values for the resistors.

Bertus
 

Maglatron

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So I've written out all the resistor values, thanks for the tip about using the E24 series, very helpful! and the caps values stayed the same so I can still use the ones that I bought!
 
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Maglatron

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That will be absolutely fine. If it’s necessary.
Thank you for confirming think I have project time tonight making 12 filter boards 4 REF GND boards and 4 envelope detector boards and adding thee amp to the same board as the preamp won't get it all done tonight but I plan on making a small dent in the work, might not have chance yet but we'll see!! also making power supply board that has USB's sockets and 5 volt regulators and switches for the 12v on and 5volt on have a bit to do also the LM3914's have come so for 2 chips on each band I'm going to be using 32 of them!
 

bertus

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Nov 8, 2019
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Hello,

Strange that you do not have a 27K resistor.
It should even be in the E12 series.
Here is an overview wich values are in E12, E24, E48 and E96 series:
vishay_color_E_series_big.png
Bertus
 

Maglatron

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not sure if I made a mistake for the bufferREF circuit I didn't have the 500k resistor so the choices were 470k or 560k I went with 560k, can always swap out when the new resistor come and to bertus I think I've just misplaced them to be honest! will 560k be alright?
 

bertus

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Hello,

Where are the 500k resistors?
The REF circiut uses 2 10k resistors in the voltage divider.
There is a 500k resistor in the amplifier.
With the 500k resistor the gain is 5 times.
With a 560k resistor the gain is 5.6 times.
With a 470k resistor the gain is 4.7 times.

Bertus
 

Maglatron

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oh shit sorry I thought it said 4.99k got mixed up and I mixed it up with 500k it's R4
1702842895799.png
 

bertus

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Hello,

A 4.7 k will be fine for R4.
The value should be about the parallel value of the voltage divider resistors.

Bertus
 

Maglatron

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4.7 good to go, going on it later for 30 mins and was going to build the amp would the 560 k suffice for that or could I use the 470k or shall I just wait untill the new resistor pack comes and use the 510k?
 

bertus

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Hello,

Just see how the amplifier behaves. As said that resistor sets the gain.

Bertus
 
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