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Re: What is the role of the capacitor in Simpl48 circuit?

 

Got it, thank you much.
Then, what should be the capacitor value to cut off audio at frequencies lower than 70Hz?
Thanks again.
Re: OPA1642 SPICE Models #dualopaalice

 

Hold on, did you also define the SUBCKT for OPA164x???? I presume you did since this is what TI provides.? But I want to make sure.

Basically, what you've done is to "call" two versions of the OPA164x subcircuit.? I used the word "call" in quotes since it's not a true procedure call.

Further, do you know that this model works in Gnu SPICE?? (I am presuming that's what KiCAD uses).





On Wed, Feb 5, 2025 at 8:42?PM matthew via <matthew=ragingbits.com@groups.io> wrote:
I'm having fun with variations on the OPA Alice circuit and would like to be able to model using SPICE in KiCAD. I found the model on TI's website but it doesn't have the correct subcircuit for a 1642, which has 8 pins. I modified that lib with the following:
?
```
* Added by matthew to model the 8-pin OPA1642AID
.SUBCKT OPA1642AID OUT_A IN-_A IN+_A VEE IN+_B IN-_B OUT_B VCC
XU1 IN+_A IN-_A VCC VEE OUT_A OPA164x
XU2 IN+_B IN-_B VCC VEE OUT_B OPA164x
.ENDS OPA1642AID
```
I then made sure that the pins match the symbol in my schematic, but when I tried to run an OP test, I got a bunch of warning and errors. Before I go down the path of trying to trouble-shoot all of this, does anyone have any experience with this who can offer any advice for modeling the OPA Alice circuit??

PS. I'm very new to electronics. I am a software engineer and have worked adjacent to and have even manage electrical engineers but this is not my area of expertise.
?
?
OPA1642 SPICE Models #dualopaalice

 

I'm having fun with variations on the OPA Alice circuit and would like to be able to model using SPICE in KiCAD. I found the model on TI's website but it doesn't have the correct subcircuit for a 1642, which has 8 pins. I modified that lib with the following:
?
```
* Added by matthew to model the 8-pin OPA1642AID
.SUBCKT OPA1642AID OUT_A IN-_A IN+_A VEE IN+_B IN-_B OUT_B VCC
XU1 IN+_A IN-_A VCC VEE OUT_A OPA164x
XU2 IN+_B IN-_B VCC VEE OUT_B OPA164x
.ENDS OPA1642AID
```
I then made sure that the pins match the symbol in my schematic, but when I tried to run an OP test, I got a bunch of warning and errors. Before I go down the path of trying to trouble-shoot all of this, does anyone have any experience with this who can offer any advice for modeling the OPA Alice circuit??

PS. I'm very new to electronics. I am a software engineer and have worked adjacent to and have even manage electrical engineers but this is not my area of expertise.
?
?
Re: What is the role of the capacitor in Simpl48 circuit?

 

In order to work, it takes disconnecting one of the internal 6.81k resistors inside the preamp, or to isolate it DC-wise, which is exactly what teh capacitor does.

Le 05/02/2025 à 13:34, renthomsen via groups.io a écrit?:
One resistor P48 electret mic
Re: What is the role of the capacitor in Simpl48 circuit?

 

A couple of years ago, Martin Kantola shared his simple P48 without a capacitor. Pure genius!
Do a search for:
?
One resistor P48 electret mic
?
Different pros and cons compared to SimpleP48.
Re: What is the role of the capacitor in Simpl48 circuit?

 

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Le 05/02/2025 à 07:31, Adam Jo5eph via groups.io a écrit?:
Dear All,
My questions are, In the simpl48 circuit, what is the role of the capacitor?
Tj=he role of the capacitor is to conduct AC signal whilst isolating DC.
What happens if it is not used?
Not used, as in "not there" or as in "replaced with a short"?
In the former case, very low signal, in the latter case, too low DC voltage on the capsule, so no signal.

What are the results at different values?
The capacitor acts as a high-pass filter, in conjunction with the mic preamp input impedance.
Small cap-> no bass.

Many thanks.
?
?

?

?
Re: What is the role of the capacitor in Simpl48 circuit?

 

The capacitor blocks the 48V to your mic. The 48V via pin 3 is limited to a safe voltage by the resistor. Smaller values will make a 6dB/octave HP filter in the audio range. Mostly nor desired.
What is the role of the capacitor in Simpl48 circuit?

 

Dear All,
My questions are, In the simpl48 circuit, what is the role of the capacitor? What happens if it is not used? What are the results at different values?
Many thanks.
?
?

?

?
Re: Microphone Output Impedance

 

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Le 04/02/2025 à 00:06, Chris Caudle via groups.io a écrit?:
On Wed, Dec 18, 2024 at 08:02 AM, kandoit7 wrote:
In the case of measuring condenser microphone impedance using voltage drop
Try this method shown in a Jensen Tranformer app-note:
This method is valid for unbalanced loads, but not for all types of balanced loads..
?
That will work for an active output microphone if you measure the impedance of pin 2 reference to pin 1, and separately pin 3 referenced to pin 1, and add the results together.
This is true only if the outputs are non-floating, which is the case of the typical Schoeps arrangement, or impedance-balanced circuits.
Some circuits need to be measured differentially.
For a transformer output microphone you would use pin 3 as the reference pin for the signal generator, and connect the measurement resistor to pin 2.

That is correct for a xfmr output, but electronically balanced circuits may not be suitale for having one of their legs grounded.

That's why I recommended the OP to use a fully floating measurement system.

?
-- Chris C
Re: Microphone Output Impedance

 

On Wed, Dec 18, 2024 at 08:02 AM, kandoit7 wrote:
In the case of measuring condenser microphone impedance using voltage drop
Try this method shown in a Jensen Tranformer app-note:
?
That will work for an active output microphone if you measure the impedance of pin 2 reference to pin 1, and separately pin 3 referenced to pin 1, and add the results together.
For a transformer output microphone you would use pin 3 as the reference pin for the signal generator, and connect the measurement resistor to pin 2.
?
-- Chris C
Re: Microphone Output Impedance

 

"Earthworks Homepage's M23R Spec :
OUTPUT IMPEDANCE ? ?65Ω balanced (between pins 2 & 3)"
?
That means exactly what it states, that the output signal is taken between pins 2 and 3, and the impedance of that signal is 65 Ohms.? Very likely not a transformer output, so an active output would have common mode impedances of 32.5 Ohms from pin 2 referenced to pin 1, and also from pin 3 referenced to pin 1, but for a transformer coupled output there would be no galvanic connection between either pin 2 or 3 and pin 1, so it would not make sense to discuss the impedance of pin 2 separately from pin 3, except in the context of parasitic capacitance and how that affects high frequency common mode impedance.
?
-- Chris C

?
Re: Microphone output impedance

 

Thanks Jerry, I thought it was 1K. I worked in Marketing for a decade... Medical Devices. And there was the FDA... ;-)

Jules



On Sun, Feb 2, 2025 at 10:07?AM Jerry Lee Marcel via <jerryleemarcel=sfr.fr@groups.io> wrote:


Le 02/02/2025 à 19:54, Jules Ryckebusch via a écrit?:
Question for the group on this. What is the?correct frequency to measure the output impedance? I am assuming referenced to 1Khz.
In the absence of a comment saying different, impedances are measured at 1kHz.
Or should?it be 20hz to 20Khz?
Some manufacturers indicate that impedance may vary over the audio range.
What do manufacturers spec?
Anything the mktg dept deems valuable.
Seriously, some manufacturers specs are laughable.
I checked DPA's site and they just list a value.
I've found that, although their designers are excellent, their technical communication is far from being as good.



--
Best Regards,

Jules Ryckebusch

214 399 0931




--
Best Regards,

Jules Ryckebusch

214 399 0931
Re: Microphone output impedance

 

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Le 02/02/2025 à 19:54, Jules Ryckebusch via groups.io a écrit?:
Question for the group on this. What is the?correct frequency to measure the output impedance? I am assuming referenced to 1Khz.
In the absence of a comment saying different, impedances are measured at 1kHz.
Or should?it be 20hz to 20Khz?
Some manufacturers indicate that impedance may vary over the audio range.
What do manufacturers spec?
Anything the mktg dept deems valuable.
Seriously, some manufacturers specs are laughable.
I checked DPA's site and they just list a value.
I've found that, although their designers are excellent, their technical communication is far from being as good.



--
Best Regards,

Jules Ryckebusch

214 399 0931
Microphone output impedance

 

Question for the group on this. What is the?correct frequency to measure the output impedance? I am assuming referenced to 1Khz. Or should?it be 20hz to 20Khz? What do manufacturers spec? I checked DPA's site and they just list a value.



--
Best Regards,

Jules Ryckebusch

214 399 0931
Zephyr / David Searle

 

I'm trying to get in touch with David Searle, aka Zephyr on MicBuilders.
?
David, if you are still looking in occasionally, the email address I have for your no longer works.
?
My old email address no longer works either :(? So please use this one to reply
?
Richard Lee
aka
Ricardo
ricardo_lee@...
?
Re: Microphone Output Impedance

 

Dear Jerry,?
?
Thanks to your reply.
?
Earthworks Homepage's M23R Spec :
?
OUTPUT IMPEDANCE ? ?65Ω balanced (between pins 2 & 3)
?
This is the specification provided on the website.

What I mean here is not the Symmetric impedance between Pin 2 and Pin 3?
I think R1 + R2 = Symmetric impedance.
?
If so, 130 Ohm would be the output impedance, but I wonder if Earthworks is providing 65 Ohm.
?
haha, Thanks to you, I am building up my knowledge.
?
Best Regards,
Kandoit7
Re: Microphone Output Impedance

 

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It seems correct, indicating a mic impedance of about 130 ohms.

Le 02/02/2025 à 06:25, kandoit7 via groups.io a écrit?:

Dear Jerry,
?
I’m still getting similar results.
R1 : 66 Ohm
R2 : 65 Ohm

Here’s my question:
I’m using a single potentiometer to control both channels (R1 and R2), meaning adjusting it changes both values to nearly the same resistance.
?
Should I instead use separate potentiometers for R1 and R2 to adjust them independently?
?
This comes up because when I directly connected the M23R to the MR-PRO, the microphone’s impedance measurements showed imbalance.?
?
Best Regards,?
Kandoit7
Re: Microphone Output Impedance

 

Dear Jerry,
?
I’m still getting similar results.
R1 : 66 Ohm
R2 : 65 Ohm

Here’s my question:
I’m using a single potentiometer to control both channels (R1 and R2), meaning adjusting it changes both values to nearly the same resistance.
?
Should I instead use separate potentiometers for R1 and R2 to adjust them independently?
?
This comes up because when I directly connected the M23R to the MR-PRO, the microphone’s impedance measurements showed imbalance.?
?
Best Regards,?
Kandoit7
TSB2590 alternative?

 

Hello there,
I was looking to buy some TSB/JLI-2590 Capsules but couldnt find any to ship here to germany with reasonable shipping costs. Micboosters charges 17 pounds for shipping and I paid over 30 euros for import tax the last time i bought from them. JLI charges over 50 bucks (wth...) so theyre out of the question too.?

I then came across listings for 2501 and 2502 capsules on ebay. The 2502s look like the 2590 but without the pcb and the 2501 look exactly like the tsb2590. Its a bit sketchy as all the pictures of them on every website are exactly the same. I found a listing on aliexpress for 11 bucks per capsule and i payed about 5 bucks for shipping.: so I ordered a few.

Im still a bit sketched out because I couldnt find anything about them on the Internet except for these listings. Has anyone ever heard of these capsules? Are they a clone of the 2590s? The Measurements look to be about the same between them. Any feedback would be appreciated.
Re: Microphone Output Impedance

 

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Le 25/01/2025 à 01:16, kandoit7 via groups.io a écrit?:
?
Actually
?
MR-PRO ->? potentiometer? ->? ?Mic? -> Preamp
Pin 1? ? ? ?->? ? ? ? ? ?GND? ? ? ? ? ->? ?GND -> GND
Pin 2? ? ? ?->? ? ? ? ? ? ?R1? ? ? ? ? ? ->
Pin 3? ? ? ?->? ? ? ? ? ? ?R2? ? ? ? ? ? ->
?
?
MR-PRO Pin 1 connect GND.
?
Should I disconnect pin 1 of the MR-PRO?
Yes.
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