Adding filter to a INA217...

[amdx]

Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

> https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering,  I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.

                                      Mikek


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[Rick C]

On Saturday, February 19, 2022 at 1:08:38 PM UTC-5, amdx wrote:

Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering, I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.

Often filters are in front of significant gain stages to prevent overloading the state from out of band noise. A low pass filter only requires series resistors and capacitor between the inputs (after the filter) or to ground.. Across the input pair gives differential filtering. Capacitors to ground give common mode filtering. The series resistors give a voltage reduction when paired to the existing input resistors R1, R2, R3, R4 and R5.

What do you know about your noise? Do you have noise? I mean, do you know what you wish to prevent, details?

What is the gain of your amplifier? What is the level of your input signal? What is the level of the output signal? What is the signal source complex impedance? What is your load?

I\'m not sure what all the input circuit is for. I suspect this design uses more than one type of signal source. It would be nice to actually understand the details. It makes a difference.

--

Rick C.

- Get 1,000 miles of free Supercharging
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[Jan Panteltje]

On a sunny day (Sat, 19 Feb 2022 12:08:25 -0600) it happened amdx
<amdx@knology.net> wrote in <surbmr$aot$1@dont-email.me>:

Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering,  I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.

It is a mike preamp, leave it.
Add the bandpass on the output
You likely need an opamp for a decent bandpass filter.
How any RC stages depends on how steep your filter needs to be.
Plenty info on the net (google)
First hit for:
\'Bandpass filter calculator\'
http://www.learningaboutelectronics.com/Articles/Bandpass-filter-calculator.php

 

[whit3rd]

On Saturday, February 19, 2022 at 10:08:38 AM UTC-8, amdx wrote:

Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.
I would like a low pass filter on the input, but I don\'t want to add noise.
So, I may add it on the output. 300Hz to 3300Hz.

If I\'m reading the schematic right, you can either put a ferrite bead in
series with R6 , or a capacitor or R-C in parallel with it, for low-pass filtering.
Circa 1 uF shouldn\'t hurt the signal.

 

[John S]

On 2/19/2022 12:33 PM, Rick C wrote:

On Saturday, February 19, 2022 at 1:08:38 PM UTC-5, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering, I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.

Often filters are in front of significant gain stages to prevent overloading the state from out of band noise. A low pass filter only requires series resistors and capacitor between the inputs (after the filter) or to ground. Across the input pair gives differential filtering. Capacitors to ground give common mode filtering. The series resistors give a voltage reduction when paired to the existing input resistors R1, R2, R3, R4 and R5.

What do you know about your noise? Do you have noise? I mean, do you know what you wish to prevent, details?

What is the gain of your amplifier? What is the level of your input signal? What is the level of the output signal? What is the signal source complex impedance? What is your load?

I\'m not sure what all the input circuit is for. I suspect this design uses more than one type of signal source. It would be nice to actually understand the details. It makes a difference.

Where is R7?

 

[Lasse Langwadt Christensen]

lørdag den 19. februar 2022 kl. 20.23.37 UTC+1 skrev John S:

On 2/19/2022 12:33 PM, Rick C wrote:
On Saturday, February 19, 2022 at 1:08:38 PM UTC-5, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering, I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.

Often filters are in front of significant gain stages to prevent overloading the state from out of band noise. A low pass filter only requires series resistors and capacitor between the inputs (after the filter) or to ground. Across the input pair gives differential filtering. Capacitors to ground give common mode filtering. The series resistors give a voltage reduction when paired to the existing input resistors R1, R2, R3, R4 and R5.

What do you know about your noise? Do you have noise? I mean, do you know what you wish to prevent, details?

What is the gain of your amplifier? What is the level of your input signal? What is the level of the output signal? What is the signal source complex impedance? What is your load?

I\'m not sure what all the input circuit is for. I suspect this design uses more than one type of signal source. It would be nice to actually understand the details. It makes a difference.

Where is R7?

https://www.ti.com/lit/ds/symlink/ina217.pdf page 13

 

[whit3rd]

On Saturday, February 19, 2022 at 11:11:25 AM UTC-8, whit3rd wrote:

On Saturday, February 19, 2022 at 10:08:38 AM UTC-8, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.
I would like a low pass filter ...

If I\'m reading the schematic right, you can either put a ferrite bead in
series with R6 , or a capacitor or R-C in parallel with it, for low-pass filtering.

Oops; sign error. For low pass, you want capacitor in series with R6, or
inductor or L-R in parallel.

 

[amdx]

On 2/19/2022 12:33 PM, Rick C wrote:

On Saturday, February 19, 2022 at 1:08:38 PM UTC-5, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering, I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.
Often filters are in front of significant gain stages to prevent overloading the state from out of band noise. A low pass filter only requires series resistors and capacitor between the inputs (after the filter) or to ground. Across the input pair gives differential filtering. Capacitors to ground give common mode filtering. The series resistors give a voltage reduction when paired to the existing input resistors R1, R2, R3, R4 and R5.

What do you know about your noise?

 Not really, I just want low noise and high gain. What is high gain, I
don\'t know yet, I\'m building a big ear.

I have experimented with an amp that has a gain of 3500 and could hear
the clock ticking and every car that went by.

I wrapped the mic in foam and put it in a lead pipe. I didn\'t hear those
things but I did hear hiss. I swapped the mic for resistors

but no longer remember what value my ears said had the equal noise.

Do you have noise?
Sure, but I can\'t quantify it.
I mean, do you know what you wish to prevent, details?

 Because of the high gain, noise is also amplified. I have been told
that the mic I have chose is noisy, but for now it\'s what I have.

AOM5024

> https://www.puiaudio.com/media/SpecSheet/AOM-5024L-HD-R.pdf
I\'m simply trying to make a low noise audio amplifier. It is probably
all over kill if I make decent filters to roll off both ends.

 But, that is OK.

What is the gain of your amplifier?
 Probably an adjustable max of 4000 voltage gain.
What is the level of your input signal?
  mic input, other than that, I don\'t know the max of that.
What is the level of the output signal?
Output to drive headphones.
What is the signal source complex impedance? What is your load?
I\'m not sure what all the input circuit is for. I suspect this design uses more than one type of signal source. It would be nice to actually understand the details. It makes a difference.

Here is my proposed circuit,

https://www.dropbox.com/s/4b8bn9fu5r0wkk2/INA217%20with%20filters%20DB.jpg?dl=0
 Just wondering if I can get some filtering in the Gain resistor circuit.

                    Mike



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[amdx]

On 2/19/2022 1:23 PM, John S wrote:

On 2/19/2022 12:33 PM, Rick C wrote:
On Saturday, February 19, 2022 at 1:08:38 PM UTC-5, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0

Yes, I\'m aware I can reduce the input caps to cause High pass
filtering,  I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.

Often filters are in front of significant gain stages to prevent
overloading the state from out of band noise.  A low pass filter only
requires series resistors and capacitor between the inputs (after the
filter) or to ground.  Across the input pair gives differential
filtering.  Capacitors to ground give common mode filtering.  The
series resistors give a voltage reduction when paired to the existing
input resistors R1, R2, R3, R4 and R5.

What do you know about your noise?  Do you have noise?  I mean, do
you know what you wish to prevent, details?

What is the gain of your amplifier?  What is the level of your input
signal?  What is the level of the output signal?  What is the signal
source complex impedance?  What is your load?

I\'m not sure what all the input circuit is for.  I suspect this
design uses more than one type of signal source.  It would be nice to
actually understand the details.  It makes a difference.


Where is R7?

Do you mean the output load?

https://www.dropbox.com/s/4b8bn9fu5r0wkk2/INA217%20with%20filters%20DB.jpg?dl=0

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[amdx]

On 2/19/2022 2:11 PM, whit3rd wrote:

On Saturday, February 19, 2022 at 11:11:25 AM UTC-8, whit3rd wrote:
On Saturday, February 19, 2022 at 10:08:38 AM UTC-8, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.
I would like a low pass filter ...
If I\'m reading the schematic right, you can either put a ferrite bead in
series with R6 , or a capacitor or R-C in parallel with it, for low-pass filtering.
Oops; sign error. For low pass, you want capacitor in series with R6, or
inductor or L-R in parallel.

https://www.dropbox.com/s/4b8bn9fu5r0wkk2/INA217%20with%20filters%20DB.jpg?dl=0
                                  Mikek

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[amdx]

On 2/19/2022 12:49 PM, Jan Panteltje wrote:

On a sunny day (Sat, 19 Feb 2022 12:08:25 -0600) it happened amdx
amdx@knology.net> wrote in <surbmr$aot$1@dont-email.me>:

Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering,  I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.
It is a mike preamp, leave it.
Add the bandpass on the output
You likely need an opamp for a decent bandpass filter.
How any RC stages depends on how steep your filter needs to be.
Plenty info on the net (google)
First hit for:
\'Bandpass filter calculator\'
http://www.learningaboutelectronics.com/Articles/Bandpass-filter-calculator.php

 Thanks Jan, for now, I\'m just going to use simple RC filters that I
can construct on the PCB I bought.

There may come a time when I can see if a good bandpass filter helps any.

 The PCB.

Tinyurl,

https://tinyurl.com/2m6f3dcf

https://www.ebay.com/itm/321599109184?_trkparms=amclksrc%3DITM%26aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D611021ebebe54267a7a59b3edfb151ca%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D321599109184%26itm%3D321599109184%26pmt%3D0%26noa%3D1%26pg%3D2380057%26brand%3DUnbranded&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Ab51cfa85-91c6-11ec-ad78-267cb896afc4%7Cparentrq%3A13c783f417f0a7650d5e6a6afffb638c%7Ciid%3A1

                                 Mikek



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[Phil Allison]

amdx is an incorrigible IDIOT wrote:

==========================

Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

** Yaaawnnnn......

To hear or record very faint sounds, you need two things:

1. A special ( read expensive) low noise microphone.

2. A *VERY* quite indoor environment.

You have neither.



....... Phil

 

[amdx]

On 2/19/2022 3:15 PM, Phil Allison wrote:

amdx is an incorrigible IDIOT wrote:

==========================
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.
** Yaaawnnnn......

To hear or record very faint sounds, you need two things:

1. A special ( read expensive) low noise microphone.

2. A *VERY* quite indoor environment.

You have neither.



...... Phil


Yep, it will never work, so don\'t follow this thread.

                          Mikek


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[Phil Allison]

amdx is an incorrigible FUCKING IDIOT wrote:
=======================================
<

Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

** Yaaawnnnn......

To hear or record very faint sounds, you need two things:

1. A special ( read expensive) low noise microphone.

2. A *VERY* quite indoor environment.

You have neither.


Yep, it will never work,

** So kindly FUCK OFF.

> so don\'t follow this thread.

** DROP dead you TROLLING wog POS.



..... love, Phil

 

[Lasse Langwadt Christensen]

lørdag den 19. februar 2022 kl. 19.33.21 UTC+1 skrev gnuarm.del...@gmail.com:

On Saturday, February 19, 2022 at 1:08:38 PM UTC-5, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering, I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.
Often filters are in front of significant gain stages to prevent overloading the state from out of band noise. A low pass filter only requires series resistors and capacitor between the inputs (after the filter) or to ground. Across the input pair gives differential filtering. Capacitors to ground give common mode filtering. The series resistors give a voltage reduction when paired to the existing input resistors R1, R2, R3, R4 and R5.

What do you know about your noise? Do you have noise? I mean, do you know what you wish to prevent, details?

What is the gain of your amplifier? What is the level of your input signal? What is the level of the output signal? What is the signal source complex impedance? What is your load?

I\'m not sure what all the input circuit is for. I suspect this design uses more than one type of signal source. It would be nice to actually understand the details. It makes a difference.

balanced, XLR, phantom power, should be big hint that it is a microphone pre amplifier

 

[Phil Allison]

lang...@fonz.dk wrote:
==================

What do you know about your noise? Do you have noise? I mean, do you know what you wish to prevent, details?

What is the gain of your amplifier? What is the level of your input signal?
What is the level of the output signal?
What is the signal source complex impedance? What is your load?

I\'m not sure what all the input circuit is for. I suspect this design uses more than one type of signal source. It would be nice to actually understand the details. It makes a difference.

balanced, XLR, phantom power, should be big hint that it is a microphone pre amplifier


** LOL - ain\'t Rick C a hoot ??

Pin up boy for the Dunning Kruger Effect.



....... Phil

 

[Rick C]

On Saturday, February 19, 2022 at 3:11:21 PM UTC-5, whit3rd wrote:

On Saturday, February 19, 2022 at 11:11:25 AM UTC-8, whit3rd wrote:
On Saturday, February 19, 2022 at 10:08:38 AM UTC-8, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.
I would like a low pass filter ...
If I\'m reading the schematic right, you can either put a ferrite bead in
series with R6 , or a capacitor or R-C in parallel with it, for low-pass filtering.
Oops; sign error. For low pass, you want capacitor in series with R6, or
inductor or L-R in parallel.

I\'m not sure that is going to do what you want. A series cap on R6 will produce less gain at the low end. Higher impedance in the reference leg of the negative feedback reduces gain to a minimum of 1. Parallel or serial is not the issue, both produce a higher impedance at low frequencies and so a lower gain. The problem is this leg is not the place to use a cap to create a low pass filter. Even a high pass filter at this point has the limitation of having 0dB as the floor, so not such a good filter. To make a low pass filter, the cap needs to be across the feedback resistor which is not accessible.

Consider this. If you could create a useful filter in this configuration, they would include it in the app notes in the data sheet I am sure.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

 

[Rick C]

On Saturday, February 19, 2022 at 3:40:29 PM UTC-5, amdx wrote:

On 2/19/2022 12:33 PM, Rick C wrote:
On Saturday, February 19, 2022 at 1:08:38 PM UTC-5, amdx wrote:
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.

Circuit shown here.

https://www.dropbox.com/s/wjixn4jq464i1fj/INA217%20Gain%20control.jpg?dl=0
Yes, I\'m aware I can reduce the input caps to cause High pass
filtering, I would like a low pass filter

on the input, but I don\'t want to add noise. So, I may add it on the
output. 300Hz to 3300Hz.
Often filters are in front of significant gain stages to prevent overloading the state from out of band noise. A low pass filter only requires series resistors and capacitor between the inputs (after the filter) or to ground. Across the input pair gives differential filtering. Capacitors to ground give common mode filtering. The series resistors give a voltage reduction when paired to the existing input resistors R1, R2, R3, R4 and R5.

What do you know about your noise?
Not really, I just want low noise and high gain. What is high gain, I
don\'t know yet, I\'m building a big ear.

I have experimented with an amp that has a gain of 3500 and could hear
the clock ticking and every car that went by.

I wrapped the mic in foam and put it in a lead pipe. I didn\'t hear those
things but I did hear hiss. I swapped the mic for resistors

but no longer remember what value my ears said had the equal noise.

Do you have noise?
Sure, but I can\'t quantify it.
I mean, do you know what you wish to prevent, details?
Because of the high gain, noise is also amplified. I have been told
that the mic I have chose is noisy, but for now it\'s what I have.

AOM5024

https://www.puiaudio.com/media/SpecSheet/AOM-5024L-HD-R.pdf
I\'m simply trying to make a low noise audio amplifier. It is probably
all over kill if I make decent filters to roll off both ends.

But, that is OK.

Ok, you want something to filter noise, but don\'t know what. You don\'t know anything about your noise. At least you know something about the mic. But it sounds like your mic is actually pretty good, producing about the same noise as a resistor. How much better do you think it\'s going to get?

The only advantage a filter will do is remove noise outside your passband which is not a lot. 300-3000 Hz vs 20-20,000, so about 1/3rd the noise?

What is the gain of your amplifier?
Probably an adjustable max of 4000 voltage gain.
What is the level of your input signal?
mic input, other than that, I don\'t know the max of that.
What is the level of the output signal?
Output to drive headphones.
What is the signal source complex impedance? What is your load?
I\'m not sure what all the input circuit is for. I suspect this design uses more than one type of signal source. It would be nice to actually understand the details. It makes a difference.

I think the 48V option is for a mic that needs a high DC bias. If you are using an electret mic, you probably can simplify the circuit a lot. For one thing, you don\'t need differential inputs. Makes the filtering simpler. Use a battery for the electret bias to avoid any added noise on the input.

Here is my proposed circuit,

https://www.dropbox.com/s/4b8bn9fu5r0wkk2/INA217%20with%20filters%20DB.jpg?dl=0
Just wondering if I can get some filtering in the Gain resistor circuit.

If you mean RG, no. Well, the answer is yes, but it will be high pass which you don\'t need.

Remove C2. Don\'t short it, disconnect it entirely. It is doing nothing. The output filter can be 1k and 47 nF/150 nF, slightly more convenient numbers, but whatever. The R4/R5 value loads the mic which is now a much higher input impedance reducing the gain. Maybe instead of using a 14k resistor to 15V, use a divider pair with a lower parallel resistance and a 3V reference. Then R4/R5 aren\'t so much a problem. Or increase the values of R4/R5. I\'m not sure if they have recommended values for some reason. Check the amp data sheet. Input bias is usually a factor, but your design is AC so maybe not important.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

 

[Phil Allison]

gnuarm.del...@gmail.com wrote:

============================

Ok, you want something to filter noise, but don\'t know what.
You don\'t know anything about your noise.
At least you know something about the mic.
But it sounds like your mic is actually pretty good,
producing about the same noise as a resistor.

** ROTFL - resistors actually don\'t make good microphones.

The pin-up boy has just gone to page 3, in the nude.


..... Phil

 

[Rick C]

On Saturday, February 19, 2022 at 4:15:52 PM UTC-5, palli...@gmail.com wrote:

amdx is an incorrigible IDIOT wrote:

=========================
Is there a way to add a simple RC filter in the gain control circuit
(fixed gain) of a INA217 audio amp.
** Yaaawnnnn......

To hear or record very faint sounds, you need two things:

1. A special ( read expensive) low noise microphone.

2. A *VERY* quite indoor environment.

You have neither.

Or a better microphone assembly. I\'ve never done it, but I\'ve read about shotgun mics. I think each element needs it\'s own amplifier, but read up on it, maybe they combine them all into one amp. Or maybe it uses an acoustic coupling of the tubes into a single element. I think it makes the mic less important since the acoustics boost the signal quite a bit.

https://sound.stackexchange.com/questions/281/really-weird-diy-shotgun-mic-old-yes-but-i-just-found-it-again

The OP\'s setup would only need a 2 foot tube to reach 300 Hz so rather smaller than shown.

A parabolic reflector also can greatly improve the sensitivity of the mic.

I\'m talking to the OP, not the resident noise maker, so Phil can keep his comments to himself. It\'s not like anyone cares what he says. He is also frequently wrong.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209