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Re: What is the role of the capacitor in Simpl48 circuit?
开云体育It sepends on the actual input impedance of the mic preamp. For a typical 2kohm input impedance, the capacitor should be
1.15uF for 70Hz cut-off. Much less efficient than any active high-pass filter in the
preamp. Le 06/02/2025 à 03:11, Adam Jo5eph via
groups.io a écrit?:
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Re: OPA1642 SPICE Models
#dualopaalice
On Wed, Feb 5, 2025 at 05:54 PM, Mark Kahrs wrote:
I literally took the .lib file provided by TI, which defines the SUBCKT and appended my SBCKT to it.
Yes. My intention was to account for all the pins with the parameters already defined in the .lib file. I am new to this, so I'm not sure that was the right way to go about it. I'm running with PSpice and LTSpice compatibility modes and it seems to be able to interpret everything correctly. Again, I'm very new to this. If it helps at all, the output looks like this: Note: Codel model file loading path is /home/matthew/workspace/Mic OPA/ Note: Compatibility modes selected: ps lt a Circuit: KiCad schematic Reducing trtol to 1 for xspice 'A' devices Doing analysis at TEMP = 27.000000 and TNOM = 27.000000 Using SPARSE 1.3 as Direct Linear Solver Note: Starting dynamic gmin stepping Warning: Dynamic gmin stepping failed Note: Starting true gmin stepping Warning: True gmin stepping failed Note: Starting source stepping Warning: source stepping failed Note: Transient op started Warning: singular matrix: ?check nodes xic1.xu1.n3294630 and c1:probe_int_n2#branch Warning: singular matrix: ?check nodes xic1.xu1.n2991579 and xic1.xu2.n2991581 Warning: singular matrix: ?check node xic1.xu1.n2991581 Warning: singular matrix: ?check nodes probe_int_probe_int_12v_c1_c1_2 and xic1.xu2.n2991579 Warning: singular matrix: ?check nodes xic1.xu1.n4619517 and xic1.xu2.n4619517 Warning: singular matrix: ?check nodes xic1.xu2.n3828449 and xic1.xu1.n2991581 Error: -4.91074e+150, -4.23671e+158 out of range for * in line bprobe_int_xic1power Error: -4.91074e+150, -4.23671e+158 out of range for * in line bprobe_int_xic1power Error: -4.91074e+150, -4.23671e+158 out of range for * in line bprobe_int_xic1power Error: -4.91074e+150, -4.23671e+158 out of range for * in line bprobe_int_xic1power Error: -4.91074e+150, -4.23671e+158 out of range for * ... ?
From there, it has a bunch of the same kind of errors, then some other lines and then eventually the unhelpful: doAnalyses: OP: ?Timestep too small; cause unrecorded. run simulation(s) aborted |
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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=[email protected]> wrote:
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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:
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```
* 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. ?
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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.
toggle quoted message
Show quoted text
Le 05/02/2025 à 13:34, renthomsen via groups.io a écrit?:
One resistor P48 electret mic |
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Re: What is the role of the capacitor in Simpl48 circuit?
开云体育
Le 05/02/2025 à 07:31, Adam Jo5eph via
groups.io a écrit?:
Tj=he role of the capacitor is to conduct AC signal whilst isolating DC. 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. The capacitor acts as a high-pass filter, in conjunction with the mic preamp input impedance. Small cap-> no bass.
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Re: Microphone Output Impedance
开云体育
Le 04/02/2025 à 00:06, Chris Caudle via
groups.io a écrit?:
This method is valid for unbalanced loads, but not for all types of balanced loads.. 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.
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.
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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:
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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 |
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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.
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-- Chris C
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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=[email protected]> wrote:
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Best Regards, Jules Ryckebusch 214 399 0931 |
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Re: Microphone output impedance
开云体育
Le 02/02/2025 à 19:54, Jules Ryckebusch
via groups.io a écrit?:
In the absence of a comment saying different, impedances are measured at 1kHz. Some manufacturers indicate that impedance may vary over the audio range. Anything the mktg dept deems valuable. Seriously, some manufacturers specs are laughable. I've found that, although their designers are excellent, their technical communication is far from being as good.
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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 |
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Zephyr / David Searle
I'm trying to get in touch with David Searle, aka Zephyr on MicBuilders.
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David, if you are still looking in occasionally, the email address I have for your no longer works.
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My old email address no longer works either :(? So please use this one to reply
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Richard Lee
aka
Ricardo
ricardo_lee@...
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Re: Microphone Output Impedance
Dear Jerry,?
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Thanks to your reply.
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Earthworks Homepage's M23R Spec :
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OUTPUT IMPEDANCE ? ?65Ω balanced (between pins 2 & 3)
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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.
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If so, 130 Ohm would be the output impedance, but I wonder if Earthworks is providing 65 Ohm.
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haha, Thanks to you, I am building up my knowledge.
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Best Regards,
Kandoit7 |
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Re: Microphone Output Impedance
开云体育It seems correct, indicating a mic impedance of about 130 ohms. Le 02/02/2025 à 06:25, kandoit7 via
groups.io a écrit?:
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Re: Microphone Output Impedance
Dear Jerry,
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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?
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This comes up because when I directly connected the M23R to the MR-PRO, the microphone’s impedance measurements showed imbalance.?
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Best Regards,? Kandoit7 |
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