Sallen Key Low Pass Filter, bandpass filter

[Maglatron]

ok getting to it, printing out proto board on paper, and going to make the layout of the circuits, and will make a channel work, I am working on it, I will show results soon!! thanks and I appreciate that it's taking a long time, like I said before, I got side tracked into something else for a while

 

[Maglatron]

There's 'bugger all' to the basic design of the filter section that couldn't be actually, physically constructed (on protoboard or hardwired)

I disagree I think it's more than possible to build the circuits on proto board and that's what I'm doing, I'll get pictures! I misunderstood yes you know it can be constructed on proto!

 

[Maglatron]

so ok I think I asked this before can the reference ground circuits be enough for four entire filters or just four op-amps in each of the filters? thanks, I think it was last said that the reference ground circuits would be good for four entire filters but just clarifying

 

[Maglatron]

found it!!!

Hello,

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

Bertus

thanks

 

[Maglatron]

so I have all of the circuits designed on paper (pre-amp, amp, first filter, referance gnd, envelope detector, and the bar graph LED drivers) for one column and am going to make a start next chance probably tomorrow! I'll keep you guys updated! thanks

 

[Maglatron]

just to confirm, do I put a 100nf cap over the +VCC and -VCC of the TL074 chips? thanks

 

[Harald Kapp]

do I put a 100nf cap over the +VCC and -VCC of the TL074 chips?

I don't know. Do you?

Generally this is recommended practice.

 

[Maglatron]

I don't know. Do you?

Generally this is recommended practice.

I think that I do have to, I've got a whisp of a memory that says that it's the right thing to do but just checking. Will it harm it if I try without? thanks

 

[Maglatron]

what should the value of rx resistor be? thanks

 

[bertus]

hello,

have a look at the discussion from the posts 500 and on.
rx is made 1k and the pot is removed.
also a buffer was added.

bertus

 

[Maglatron]

yes I've designed in the buffer aswell, after the envelope detector but before the rx resistor using the 4th op-amp out of the four in one TL074, the other 3 for the filter, got it remove the pot and use 1k resistor after the buffer thanks for pointing me to the right post!

 

[Maglatron]

so I can't seem to find where it says to mitigate the pot also in doing so, do I still put the REF in where the pot is removed or delete that too? thanks literally last question I'm working on it later today!!

 

[Harald Kapp]

literally last question

I have strong doubts about that

 

[Maglatron]

I have it all designed now, for the first column, on paper, just got to port it over to the proto board and get it soldered up and so I have the (pre-amp, amp, filter No1, envelope detector, buffer, REF gnd circuits and the LM3914 bar graph display drivers)

 

[Maglatron]

Hello,

Disconnect REF from R24.

Bertus

found it!!! so now I just have to crack on with it

 

[danadak]

just to confirm, do I put a 100nf cap over the +VCC and -VCC of the TL074 chips? thanks

Page 36 of

https://www.ti.com/lit/ds/symlink/tl074.pdf?ts=1710167213287&ref_url=https%253A%252F%252Fwww.mouser.com%252F

 

[Maglatron]

thanks you, turns out I do use a bypass capacitor 100nF cheers!

 

[Maglatron]

Pre-amp now on the main board! take pics when I can

 

[Maglatron]

So now I have done the pre-amp, amp and a reference ground for the amp and a couple of the filters. going to build the filter next, step by step slowly slowly

 

[Maglatron]

I must say it's looking awfully wirey I thought that I could make traces with the solder spots but it's not that easy they the solder blobs seem to like to stick in spots of two it's hard to join three in a row but the connections are made so hoping for the best! I'll take photos