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[Solved] Weryfikacja i optymalizacja schematu mikrofonu zasilanego z baterii 9V – PDF

gafregafre 843 11
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  • #1 21564209
    gafregafre
    Level 3  
    Posts: 9
    Dzień dobry,
    poszukuję doświadczonego elektronika, który mógłby sprawdzić i zoptymalizować schemat połączenia mikrofonu. Projekt dotyczy prostego układu zasilanego z baterii 9V, stosowanego w urządzeniu audio.

    Posiadam plik PDF ze schematem oraz dane techniczne mikrofonu.
    Potrzebuję pomocy w zakresie:

    weryfikacji poprawności układu,

    ewentualnej optymalizacji (szumy, pasmo, impedancje),

    przygotowania poprawionej wersji schematu.

    Preferowany kontakt mailowy lub przez forum.
    Z góry dziękuję za pomoc!
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  • #2 21564519
    yogi009
    Level 43  
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    And where is this scheme?
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  • #3 21571880
    _jta_
    Electronics specialist  
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    Microphone data (e.g. sensitivity characteristics) could also be useful.
  • #4 21572107
    yogi009
    Level 43  
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    Fellow Author with little interest in the subject...
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  • #5 21574785
    gafregafre
    Level 3  
    Posts: 9
    Weryfikacja i optymalizacja schematu mikrofonu zasilanego z baterii 9V – PDF

    Dodano po 1 [minuty]:

    I apologize for missing your posts. I've attached the schematic above.

    Dodano po 38 [sekundy]:

    I apologize for missing your posts. I've attached the schematic above.
  • #6 21575061
    yogi009
    Level 43  
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    Resistors R1-R5 - this is where the electret microphones are powered. Have you specified the type of microphone?
  • #7 21575081
    viayner
    Level 43  
    Posts: 10551
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    Hello,
    elaborate, what is the circuit to be, on what components and what is the application?
    So far I can see that you have some microphone cartridges, presumably with their own preamp, fed from 9 volts, further this is all summed up and fed to the gain with an operational amplifier, which I guess is supposed to "do" the compressor, because this is how it has a corrected feedback loop. You're using a relatively good operational amplifier, but it's not clear what the microphones are.
    It's hard to judge how the whole thing will perform without knowing the details.
    Regards
  • #8 21576403
    gafregafre
    Level 3  
    Posts: 9
    yogi009 wrote:
    Resistors R1-R5 - this is where the electret microphones are powered. Have you specified the type of microphone?

    The type of microphone I use is the Primo EM301. Yes, the power is supplied through resistors 1-5

    Dodano po 37 [minuty]:

    >>21576403
    Hello,

    Thank you for your message.
    You are correct - I currently have a circuit that uses electret condenser microphones. These are highly sensitive, three-wire capsules with built-in FET preamplifiers. They are powered by a 9-volt battery (PP3) through a simple resistive bias network. Each capsule is decoupled using capacitors and mixed passively.
    The mixed signal is then fed to an op-amp stage based on an OPA2134 operational amplifier. The op-amp stage also includes a feedback loop intended to act as a soft compressor, although in practice this part of the design works unreliably - most likely due to incorrect component values or topology.
    My main goals are:
    Power from a 9-volt battery;
    Maintain low-noise performance.
    The current circuit does not work as expected. I am looking for someone who can revise or redesign it properly.
  • #9 21576881
    viayner
    Level 43  
    Posts: 10551
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    Hello,
    describe exactly what is not working as expected.
    What does this "noise" consist of? Are we talking about network noise? This is more likely to be due to installation errors or lack of shielding.
    Regards
  • #10 21577286
    yogi009
    Level 43  
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    I'd have a look at the topology, especially pay attention to the real and virtual ground. I think an audio generator (any, could be a simple 1kHz) and an oscilloscope should tell you the reason for the trouble. I'm assuming that with this quality of content in your project description, you are able to do the correct shielding of the module and wiring. Write more about the length of the wires connecting the microphone module to the preamp module.
  • #11 21577456
    CYRUS2
    Level 43  
    Posts: 17639
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    gafregafre wrote:
    .
    I have a PDF file with the schematic and technical data of the microphone.
    The file will not do anything.
    You need to work on a prototype.
    gafregafre wrote:
    I need help with: possible optimisation (noise, bandwidth, impedances)
    No expected figures.
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  • #12 21650573
    gafregafre
    Level 3  
    Posts: 9
    I found the person on this site who solved my problem. Thank you all.
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Topic summary

✨ The discussion concerns verification and optimization of a simple electret microphone circuit powered by a 9V battery, intended for audio applications. The microphone used is the Primo EM301, a three-wire electret condenser capsule with a built-in FET preamplifier. The circuit powers the microphones through resistors (R1-R5) and uses capacitors for decoupling. The mixed microphone signals feed into an operational amplifier stage based on the OPA2134, which includes a feedback loop designed to function as a soft compressor. However, the compressor stage is unreliable, likely due to incorrect component values or circuit topology. Key issues include noise performance, frequency response, and impedance matching. Suggestions focus on verifying the circuit topology, especially grounding schemes (real and virtual ground), ensuring proper shielding and wiring length, and using test equipment such as an audio generator and oscilloscope to diagnose noise sources. The author seeks a revised or optimized schematic to improve low-noise operation and reliable compressor function while maintaining 9V battery power supply.
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FAQ

TL;DR: Use a 1 kHz test tone and verify the virtual ground to fix a 9 V electret mic preamp; “audio generator…1kHz” is enough to reveal faults. [Elektroda, yogi009, post #21577286]

Why it matters: Fast checks isolate wiring, grounding, and bias issues before deep redesigns—ideal for DIYers optimizing 9 V microphone circuits.

Quick Facts

What problem does this FAQ solve and who is it for?

It helps hobbyists and audio tinkerers verify and optimize a 9 V electret microphone mixer/preamp from a shared forum project request. It focuses on schematic validation, noise, bandwidth, and impedance topics for a battery‑powered build. [Elektroda, gafregafre, post #21564209]

Where is the schematic/PDF mentioned in the thread?

The author later attached the schematic in the discussion after initial prompts from others. Look for the post where the attachment notice appears and follow that message’s link in the thread. [Elektroda, gafregafre, post #21574785]

What microphones are used in the design?

The build uses Primo EM301 electret condenser capsules. They are three‑wire, highly sensitive, and include a built‑in FET preamplifier, which requires correct biasing from the 9 V supply. [Elektroda, gafregafre, post #21576403]

How are the capsules powered and mixed?

Capsules receive bias from the 9 V battery through resistors, get AC‑decoupled with capacitors, and are passively mixed. The summed signal then feeds an OPA2134 op‑amp stage for gain and dynamics control. [Elektroda, gafregafre, post #21576403]

Why do I need the microphone datasheet to optimize noise and gain?

Capsule sensitivity and impedance guide bias resistor values and mixing losses. As one expert wrote, “Microphone data… could also be useful,” because it anchors realistic gain and noise targets. [Elektroda, jta, post #21571880]

How do I quickly diagnose noise or instability in this circuit?

Inject a 1 kHz sine from an audio generator and watch the output on an oscilloscope. Inspect real and virtual ground quality first; poor references cause many faults. “Audio generator…1kHz” exposes issues fast. [Elektroda, yogi009, post #21577286]

Could wiring or shielding be the reason for the hum?

Yes. The thread highlights installation mistakes and missing shielding as common causes of “network noise.” Verify enclosure shielding, cable routing, and ground continuity before changing parts. [Elektroda, viayner, post #21576881]

Is the OPA2134 a sensible op‑amp here?

Yes. A participant noted it as a relatively good audio op‑amp choice. If compression misbehaves, check the feedback network values and topology rather than blaming the op‑amp first. [Elektroda, viayner, post #21575081]

Do I need a prototype, or is a PDF enough to optimize?

Build and test a prototype. A file alone “will not do anything.” Measured behavior under load guides real improvements and validates noise and bandwidth changes. [Elektroda, CYRUS2, post #21577456]

What was the final status of the project?

The author reported success, stating they found help on the site and the problem was solved. That closes the loop for others following the thread. [Elektroda, gafregafre, post #21650573]

How long can the microphone leads be before issues appear?

Document and minimize lead length between capsules and the preamp module. The reviewer explicitly asked for wiring length details to troubleshoot grounding and stability. Shorter runs reduce pickup. [Elektroda, yogi009, post #21577286]

What if the compressor loop behaves unpredictably?

The author observed unreliable compression. Re‑evaluate the feedback network values and overall topology around the OPA2134 before swapping parts. Stability depends on correct component choices. [Elektroda, gafregafre, post #21576403]

How do I test this preamp in three quick steps?

  1. Feed a 1 kHz sine into one capsule and monitor output with a scope.
  2. Verify real and virtual ground voltages under signal load.
  3. Sweep gain and note compression onset versus schematic values. [Elektroda, yogi009, post #21577286]

What information should I share to get better help on forums?

Attach the schematic, name the microphone model, and include sensitivity data. Also describe exact symptoms and test setup. Experts asked for these specifics to diagnose effectively. [Elektroda, jta, post #21571880]

Are the capsules powered through specific resistors? Which ones?

Yes. The design biases electret microphones using resistors labeled R1–R5 that inject power to each capsule from the 9 V source. [Elektroda, yogi009, post #21575061]

What common mistake slows down progress in threads like this?

Posting without the schematic delays useful feedback. A participant asked for the missing “scheme,” which unlocked targeted advice once attached. [Elektroda, yogi009, post #21564519]
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