Sallen Key Low Pass Filter, bandpass filter

[bertus]

Hello,

and how do you set it to 0v again? : audio is a positive and negative going signal.
What do you mean with set it to 0V?

The VCC- can get a ground simbol.

Bertus

 

[Maglatron]

thought as much but it's always best to check and so back to the novice question what type of caps do I use in the buffer circuit

 

[Maglatron]

like so, correct so far???

 

[Maglatron]

sorry got mixed up

Hello,

and how do you set it to 0v again? : audio is a positive and negative going signal.
What do you mean with set it to 0V?

The VCC- can get a ground simbol.

Bertus

I said how do you set the 0v I meant the negative pin I didn't know what you call it of the op-amp but you answered it strait away with "the VCC- can get a ground symbol"

 

[Maglatron]

so you mentioned that

Hello,

Line level for consumer audio is about 0.9 Vpp:

Line level - Wikipedia

en.wikipedia.org

With a gain of 5 the peak would be about 0.45 X 5 = 2.25 Volts.

The VCC+ is 12 Volts, VCC- is 0 Volts. REF would be 6 Volts.

Bertus

what comes from the pre-amp that will be and gets amplified to then go on to the filters to then pass the signal on to the envelope detector to go on to the lm3914's you said that the gain of 5 would translate to 2.25v, I'm not seeing something!
maybe between the preamp and the filter is where you said that the amplifier would go is the ohhhh ok I think I get it there is 0.45v from the pre-amp and you amplify it to 2.25v yes? so the voltage peak to peak is 0.9v, is 0.45 from 0 to one of the peaks?
I think I might have that wrong this is the picture that I'm supposed to be seeing, ok so the peak to peak of the light blue is approximatly 0.9 and the vpk is the 0.45 its becoming clearer now

 

[bertus]

Hello,

It depends a bit on what level is coming from the preamp.
Try to get it in the range of the comercial line level, according the wiki page.

Bertus

 

[Maglatron]

ok its been a productive day I will be doing research into how to get the commertial line level will this preamp that you supplied a while back will it do the job

Hello,

It depends a bit on what level is coming from the preamp.
Try to get it in the range of the comercial line level, according the wiki page.

Bertus

 

[Maglatron]

Hello,

It depends a bit on what level is coming from the preamp.
Try to get it in the range of the comercial line level, according the wiki page.

Bertus

commercial as in consumer?

 

[bertus]

Hello,

Sorry, yes, a consumer level of 0.9 Vpp.

The given schematic can set the gain with the 100k potmeter between 1 and 21 times for the mic.

Bertus

 

[Maglatron]

cool

 

[Maglatron]

Hello
how do you measure for vpp?

 

[Maglatron]

Hello
I think I misunderstood the pre-amp needs to amplify the signal to 0.9 vpp and then need an amplifier to amplify to 2.25v vpk (0.45 x 5) why not just use the preamp to make it output the 2.25v vpk

 

[kellys_eye]

Just curious but how old are you?

 

[Maglatron]

32 years young, and you?

Just curious but how old are you?

 

[Maglatron]

what type of capacitors do I use for the buffer, I think for the 100nf the film caps that I have will do but what about the 10uF's? I'm ordering parts!

 

[Maglatron]

So heres the first filter but I don't think its working properly, I think I have to amplify the signal first! at the moment it flat lines at 6v so part of it works properly!

 

[Maglatron]

so that didn't work but the pre-amp works perfectly!! so that is progress!! the filter just stays at a flatline at 6v the filter is for 45Hz and it's a 45Hz signal so it should pass by rights

 

[bertus]

Hello,

Remove the shorts accross R3, R8 and R11

Bertus

 

[Maglatron]

I missed something the preamp power supply was not connected to the top rail so I fixed that, it's a better result spread more evenly! still not outputting on the filters though, should I amplifiy it less and use thee amplifier circuit, I'm going to try that

 

[Maglatron]

Top Man!! perfect!! so can I use the pre-amp as the main amp or would it be best the way you originally suggested with pre-amp and then amp and then filter??

Hello,

Remove the shorts accross R3, R8 and R11

Bertus