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Cheap USB powered condenser microphone. Need advice on design.

Timothy Aguana All Messages By This Member #35851 Hello, I've drafted up a DIY design that I think could work to drive an electret capsule like the TSB-2555B through the use of a DC-DC converter () to derive a stepped up voltage from the 5V supply rail of a .? The generated voltage of the microphone is fed into an amplification circuit from the? Presented below is the proposed amplification scheme: Similar to the aforementioned OPA-Alice circuit, the amplifier to be used is planned to be the OPA1642. The USB soundcard to be integrated to the design utilizes a CM108 IC with an input range of 2.88 V pk-to-pk and a default input signal gain stage of 20dB (gain of 10). I am relatively new to the design of microphone circuitry and this design is heavily inspired the by videos and instructables from DIY Perkz and DJJules.? I would like to ask for advice regarding the design choices made and the validity/viability of the proposed design.
Mark Kahrs All Messages By This Member #36116 Here's a version of a USB powered Alice.? Comments welcome since my ability to make errors is well known. toggle quoted message Show quoted text On Fri, Nov 17, 2023 at 8:30?AM Timothy Aguana <lolnetian@...> wrote: Hello, I've drafted up a DIY design that I think could work to drive an electret capsule like the TSB-2555B through the use of a DC-DC converter () to derive a stepped up voltage from the 5V supply rail of a .? The generated voltage of the microphone is fed into an amplification circuit from the? Presented below is the proposed amplification scheme: Similar to the aforementioned OPA-Alice circuit, the amplifier to be used is planned to be the OPA1642. The USB soundcard to be integrated to the design utilizes a CM108 IC with an input range of 2.88 V pk-to-pk and a default input signal gain stage of 20dB (gain of 10). I am relatively new to the design of microphone circuitry and this design is heavily inspired the by videos and instructables from DIY Perkz and DJJules.? I would like to ask for advice regarding the design choices made and the validity/viability of the proposed design. newamp.pdf newamp.pdf
Jules Ryckebusch All Messages By This Member #36117 开云体育 That should work. You should make sure you have a ground plane and chest don’t know is how quiet the 5V to +\-15 chip you are using is ? Best Regards, Jules Ryckebusch? toggle quoted message Show quoted text On Feb 10, 2024, at 14:52, Mark Kahrs <mark.kahrs@...> wrote: ? Here's a version of a USB powered Alice.? Comments welcome since my ability to make errors is well known. On Fri, Nov 17, 2023 at 8:30?AM Timothy Aguana <lolnetian@...> wrote: Hello, I've drafted up a DIY design that I think could work to drive an electret capsule like the TSB-2555B through the use of a DC-DC converter () to derive a stepped up voltage from the 5V supply rail of a .? The generated voltage of the microphone is fed into an amplification circuit from the? Presented below is the proposed amplification scheme: <dummyfile.0.part> Similar to the aforementioned OPA-Alice circuit, the amplifier to be used is planned to be the OPA1642. The USB soundcard to be integrated to the design utilizes a CM108 IC with an input range of 2.88 V pk-to-pk and a default input signal gain stage of 20dB (gain of 10). I am relatively new to the design of microphone circuitry and this design is heavily inspired the by videos and instructables from DIY Perkz and DJJules.? I would like to ask for advice regarding the design choices made and the validity/viability of the proposed design. <newamp.pdf>
Dude All Messages By This Member #36118 May I inquire as to what the inductor, L1, is doing is this application? I have been trying to utilize USBc and lightning, for small electret capsules from iPhones and relatively recent ?smartphones, and having some troubles.? toggle quoted message Show quoted text On Sat, Feb 10, 2024 at 11:52?AM Mark Kahrs <mark.kahrs@...> wrote: Here's a version of a USB powered Alice.? Comments welcome since my ability to make errors is well known. On Fri, Nov 17, 2023 at 8:30?AM Timothy Aguana <lolnetian@...> wrote: Hello, I've drafted up a DIY design that I think could work to drive an electret capsule like the TSB-2555B through the use of a DC-DC converter () to derive a stepped up voltage from the 5V supply rail of a .? The generated voltage of the microphone is fed into an amplification circuit from the? Presented below is the proposed amplification scheme: Similar to the aforementioned OPA-Alice circuit, the amplifier to be used is planned to be the OPA1642. The USB soundcard to be integrated to the design utilizes a CM108 IC with an input range of 2.88 V pk-to-pk and a default input signal gain stage of 20dB (gain of 10). I am relatively new to the design of microphone circuitry and this design is heavily inspired the by videos and instructables from DIY Perkz and DJJules.? I would like to ask for advice regarding the design choices made and the validity/viability of the proposed design.
Scott Helmke All Messages By This Member #36119 I think you've got C1 in there backwards - positive voltage from U1 output? -Scott toggle quoted message Show quoted text On 2/10/24 13:52, Mark Kahrs wrote: Here's a version of a USB powered Alice.? Comments welcome since my ability to make errors is well known. On Fri, Nov 17, 2023 at 8:30?AM Timothy Aguana <lolnetian@...> wrote: Hello, I've drafted up a DIY design that I think could work to drive an electret capsule like the TSB-2555B through the use of a DC-DC converter (IEB0105S12 <>) to derive a stepped up voltage from the 5V supply rail of a USB soundcard <>. The generated voltage of the microphone is fed into an amplification circuit from the OPA-Alice circuit. <> Presented below is the proposed amplification scheme: Similar to the aforementioned OPA-Alice circuit, the amplifier to be used is planned to be the OPA1642. The USB soundcard to be integrated to the design utilizes a CM108 IC with an input range of 2.88 V pk-to-pk and a default input signal gain stage of 20dB (gain of 10). I am relatively new to the design of microphone circuitry and this design is heavily inspired the by videos and instructables from DIY Perkz and DJJules. I would like to ask for advice regarding the design choices made and the validity/viability of the proposed design. -- ---- Scott Helmke ---- scott@... ---- (734) 604-9340 ---- "I have ceased distinguishing between the religious and the secular, for everything is holy" - Joe Henry
Jerry Lee Marcel All Messages By This Member #36120 开云体育 L1, with associated capacitors is an EMI filter that both prevents interference/noise coming from the USB connection to pollute the mic circuit AND to prevent oscillation residues from the switching converter to pollute the USB port. Le 11/02/2024 à 04:28, Dude a écrit?: toggle quoted message Show quoted text May I inquire as to what the inductor, L1, is doing is this application? I have been trying to utilize USBc and lightning, for small electret capsules from iPhones and relatively recent ?smartphones, and having some troubles.? On Sat, Feb 10, 2024 at 11:52?AM Mark Kahrs <mark.kahrs@...> wrote: Here's a version of a USB powered Alice.? Comments welcome since my ability to make errors is well known. On Fri, Nov 17, 2023 at 8:30?AM Timothy Aguana <lolnetian@...> wrote: Hello, I've drafted up a DIY design that I think could work to drive an electret capsule like the TSB-2555B through the use of a DC-DC converter () to derive a stepped up voltage from the 5V supply rail of a .? The generated voltage of the microphone is fed into an amplification circuit from the? Presented below is the proposed amplification scheme: Similar to the aforementioned OPA-Alice circuit, the amplifier to be used is planned to be the OPA1642. The USB soundcard to be integrated to the design utilizes a CM108 IC with an input range of 2.88 V pk-to-pk and a default input signal gain stage of 20dB (gain of 10). I am relatively new to the design of microphone circuitry and this design is heavily inspired the by videos and instructables from DIY Perkz and DJJules.? I would like to ask for advice regarding the design choices made and the validity/viability of the proposed design.
Timothy Aguana All Messages By This Member #36121 Ah yes, I noticed and corrected the capacitor polarity issue on the breadboard implementation. However, I ran into some trouble getting an actual output out with these c-media usb interface chips (the cm108 is especially bad). So I moved on to using a cheap soundcard commonly available through aliexpress and maybe local vendors which utilizes the cm6206 (blue 5.1 soundcard from aliexpress) audio interface chip. Turns out these chips are designed to take in mic level inputs so the second amplification stage may be completely unnecessary in the original design. The non-faraday caged audio output seems promising but the AC mains hum is prominently present in the output after inspection through an Audacity spectrogram. I'll provide more updates as soon as I get a proper soldering station to wire up a perfboard implementation. As for the +/- 15V the supply voltage was basically DC (from oscilloscope readings) after being filtered by some bypass capacitors and low pass filters. I will definitely add a ground plane in the final PCB implementation. Best regards, Timothy Aguana
Henry Spragens All Messages By This Member #36126 When I looked into "USB Soundcards" I found they are based on chips that combine an op-amp mic preamp, A to D converter, and USB interface with power drawn from USB. The converters were 16 bits at 41 or 48 KHz. Fidelity was sacrificed for low cost and minimum external parts count. Performance ranged from acceptable for video chat, to really awful. I didn't experiment further, since even the cheapest XLR input interfaces offer better audio.
Timothy Aguana All Messages By This Member #37008 Hello, ? To provided an update to this DIY project, I've made an initial implementation with mixed results: The amplification scheme does work and the quality of the microphone output was good. However, due to poor trace layout and bad choice in microphone body termination (XLR instead of USB-B) high pitched digital noise comes through either from cross talk between the power rails and output audio signal, poor A/D converter performance and ad-hoc modifications to the input port of the soundboard. This digital noise was also observed to increase in loudness as the resistance of the potentiometer (and therefore the gain) increases which leads me to believe that cross-talk is the main issue with the design. I've since made improvements to the trace layout and added decoupling capacitors to the rails of the converter and the OPA1642 to help alleviate the noise issue present in the audible signal. ? I would like to ask if anyone has any idea on the what the internals of the USB-B version of the BM800 looks like? Particularly the connection of the USB-B port to the on-board PCB. I've tried scouring the internet for these details but information regarding this is scarce.
Jules Ryckebusch All Messages By This Member #37010 开云体育 Welcome to mixed signal design. There are a lot of challenges to this. The opa1642 needs Well filtered supplies but also the high impedance side of things need to be well shielded from the digital noise generated by the USB side of things. I have not checked out the usb version of a bm800. I suspect it works but probably doesn’t have a good S/N ratio ? Best Regards, Jules Ryckebusch? toggle quoted message Show quoted text On Nov 12, 2024, at 20:01, Timothy Aguana via groups.io <lolnetian@...> wrote: ? Hello, ? To provided an update to this DIY project, I've made an initial implementation with mixed results: The amplification scheme does work and the quality of the microphone output was good. However, due to poor trace layout and bad choice in microphone body termination (XLR instead of USB-B) high pitched digital noise comes through either from cross talk between the power rails and output audio signal, poor A/D converter performance and ad-hoc modifications to the input port of the soundboard. This digital noise was also observed to increase in loudness as the resistance of the potentiometer (and therefore the gain) increases which leads me to believe that cross-talk is the main issue with the design. I've since made improvements to the trace layout and added decoupling capacitors to the rails of the converter and the OPA1642 to help alleviate the noise issue present in the audible signal. ? I would like to ask if anyone has any idea on the what the internals of the USB-B version of the BM800 looks like? Particularly the connection of the USB-B port to the on-board PCB. I've tried scouring the internet for these details but information regarding this is scarce.
Henry Spragens All Messages By This Member #37011 I did a tear-down of a $14 USB mic here: This particular example was much better than I expected, especially for the price.

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