Re: Selling gear on the forum- is it allowed?
Thanks Jules, glad I checked.
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Re: Selling gear on the forum- is it allowed?
Hi Damian,
Unfortunately, selling items on the forum is not allowed. You can mention sites you find or sources of components etc. but not selling your own stuff. Best Regards,
Jules Ryckebusch?
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On Apr 27, 2025, at 11:35, damiandrohanphoto via groups.io <damiandrohanphoto@...> wrote:
? Hi all, I have a few mics I'm thinking of selling, is it allowed on the forum? Just said I'd ask in case of falling foul of moderation or etiquette, thanks, Damian
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Selling gear on the forum- is it allowed?
Hi all, I have a few mics I'm thinking of selling, is it allowed on the forum? Just said I'd ask in case of falling foul of moderation or etiquette, thanks, Damian
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Re: Troubleshooting OPA142 circuit for noise-cancelling aviation mic
On reflection, no I wouldn't omit C6; opamps like caps (C6, C7) right at the IC.
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Re: Troubleshooting OPA142 circuit for noise-cancelling aviation mic
I think I would omit C9 and C6. Ground is the reference to AC-couple to to the virtual ground; C9 is coupling to the +v rail, which I wouldn't want. And given the presence of C18, C10 is arguably redundant.
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I'd also consider a bit more filtering of the voltage fed to R1 and R2, like an RC of 470 ohm and 10uF.
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The FET-equipped electret capsules I usually mess with don't draw more than about 0.5 mA each, max.
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Re: Troubleshooting OPA142 circuit for noise-cancelling aviation mic
You may want to make R3 and R4 adjustable, if only to compensate the difference in sensitivity. You may find that the best noise rejection does not coincide with perfect balance.
Apart from that, I think the design is sound.
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Re: Troubleshooting OPA142 circuit for noise-cancelling aviation mic
Here's my latest design for the aviation mic based on the feedback.
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Things I wanted to fix:
- Actually be able to control gain properly
- Flat(ish) frequency response despite being a diff
- Prevent motor-boating / noise from bias power supply
Major changes are:
- Lowered working voltage to 5V supplied through a low current vreg to try to eliminate motor-boating problem
- Using an Instrumentation Amplifier (AD8220) instead of dual op-amps
- Using "normal" FET electrets (CMI-5247TF-K) to gain better RFI screening
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AD8220 data sheet is here:
C3/C4/C5 are AD8220 input RFI suppression, as advised in the AD8220 datasheet.
C6/C7/C9/C10 are AD8220 output RFI suppression, as advised in the AD8220 datasheet.
C8 prevents ringing, as advised in the AD8220 datasheet
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R5 sets the gain. At 2k2 this is approx 30x. The usage environment is the electret capsules will be in a mouthpiece a few cm away from the person speaking, so I am assuming an effective SPL of 85-100dB, so an electret capsule output of ~3-10mV RMS. The comm radio accepts 70mV-1000mV RMS, so 30x seemed sensible (90-300mV RMS). There's a pot that can trim it if someone has set the comm radios to max input sensitivity.
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As before the left side Mic Board sits inside brass mesh screening, mounted onto the end of a flexible gooseneck arm. The power/control board sits in a screened PCB enclosure mounted onto the headphones headband. I'm using a thin CNC coolant hose for the flexible gooseneck arm (works really well). Shielded 2-core Canford audio cable connects between the two boards.
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I'm aware that this is probably rather over-engineered for a simple active noise cancelling mic scenario, but I'm enjoying myself!
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Are there any glaring flaws with this design?
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Re: dynamic capsule suggestion for toms and kick drum?
I own two Chinese dynamic capsule supposedly for SM57 replacement. I will try to find the brand when I get back home.?
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Re: dynamic capsule suggestion for toms and kick drum?
Mic Sharf, maybe do you think about Xtuga?
I owned a long time ago an Audio Technica kit that was worth the money. Maybe Shure PGA56 can do the job, I never tried them.?
Best regards,
Aymeric LORION
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File /Dynamic cartridges data recap report 1a small font .pdf uploaded
#file-notice
The following items have been added to the Files area of the [email protected] group.
By: Richards <jrichards@...>
Description:
List of low cost dynamic cartridges - mostly acquired on eBay for less than $10 Us, a few cost less than $15 US. A true work in progress, I am working to summarize their relative merits. Maybe it will help somebody. James
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Re: capsule suggestion needed for loud environment recording
Yes! Parallel!!!!! Best Regards,
Jules Ryckebusch?
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On Apr 25, 2025, at 00:38, j.postma8 via groups.io <j.postma8@...> wrote:
? "What you want to do is put a small capacitor in series with the capsule."
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Typo? I guess you meant parallel.
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Jan
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Re: Troubleshooting OPA142 circuit for noise-cancelling aviation mic
I don't think there's any serious problem with the reference being a virual ground, as long as it's correctly decoupled to ground with a capacitor.
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Re: dynamic capsule suggestion for toms and kick drum?
try this
Gesendet: Freitag, 25. April 2025 um 12:43
Von: "Muninn via groups.io" <ninmiso@...>
Betreff: Re: [MicBuilders] dynamic capsule suggestion for toms and kick drum?
i dont have them with me, no. also i don't really remember the chinese brand, the kick drum seem a little bit similar to a beta 52 and tom ones are similar to some audix mics.?
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Re: Troubleshooting OPA142 circuit for noise-cancelling aviation mic
Yeah it would make more sense to ground via mic input jack sleeve, though I think in the comm radio the mic sleeve and headphone sleeve are commoned together anyway.
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I went for FETless electrets and OPA1642 because I had the parts already, and needing to keep things within the current limits. I'm seeing bias voltage sag at 12mA, so ideally want under 10mA.
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I wanted to use an op-amp because of the desire for diff mode to reject the background noise. My concern was that FET-electrets would each draw about 2mA, then I'd need the op-amp on top. So the thinking was just use Jules' trick of fusing the FET stage with the op-amp by using an OPA164x.
Screening-wise, the OPA is right up next to the capsule, on a small PCB encased in grounded brass-mesh. The previous version's RF problems seemed to be due to the cable entry. The sleeve connection in the combined headphone/mic cable was not reliable because I'd fudged a headphone/mic splitter along the cable length owing to lack of space in the main PCB enclosure. This latest version has a shielded 3D printed enclosure with enough space so is meant to fix that.?
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After Jerry's comments RE: flat inputs, I have looked at Instrumentation Amplifiers, but the sticking point with those is the need for a low impedance reference voltage, which my virtual ground via a potential divider is not.
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Re: dynamic capsule suggestion for toms and kick drum?
i dont have them with me, no. also i don't really remember the chinese brand, the kick drum seem a little bit similar to a beta 52 and tom ones are similar to some audix mics.?
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Re: dynamic capsule suggestion for toms and kick drum?
Do you have pictures of the bodies? --
Gesendet mit der WEB.DE Mail App
Am 25.04.25, 11:54 schrieb "Muninn via " <ninmiso=@>:
hi there, a friend of mine gifted me a very bad cheap drum microphone kit. needless to say, it sound as bad as it can be. never heard something like that.
anyway, mic bodies are quite sturdy and heavy, i'm thinking about changing capsules to the kick drum mic and toms.
can you suggest me some good dynamic capsules for that?
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Re: capsule suggestion needed for loud environment recording
On Thu, Apr 24, 2025 at 08:04 PM, Jules Ryckebusch wrote:
What you want to do is put a small capacitor in series with the capsule. Think of it this way: the capsule itself is a capacitor. If you put the same value capacitor in series with it, the signal developed on the microphone drops in half.
Sorry to contradict you, but it's absolutely untrue. Putting a capacitor in series with the capsule changes the -3dB LF response. Since the typcal +3dB point is about 10 Hz for an SDC, it would result in identical output in the audio range. Incidentally, it would also increase noise by 6dB.
The three most common ways for decreasing sensitivity are:
- Decreasing the bias voltage
- Adding a capacitor in parallels with the capsule
- Adding a NFB capacitor, for a so-called "charge amp"
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dynamic capsule suggestion for toms and kick drum?
hi there, a friend of mine gifted me a very bad cheap drum microphone kit. needless to say, it sound as bad as it can be. never heard something like that.
anyway, mic bodies are quite sturdy and heavy, i'm thinking about changing capsules to the kick drum mic and toms.
can you suggest me some good dynamic capsules for that?
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Re: capsule suggestion needed for loud environment recording
"What you want to do is put a small capacitor in series with the capsule."
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Typo? I guess you meant parallel.
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Jan
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Re: capsule suggestion needed for loud environment recording
What you want to do is put a small capacitor in series with the capsule. Think of it this way: the capsule itself is a capacitor. If you put the same value capacitor in series with it, the signal developed on the microphone drops in half. That corresponds to a 6dB drop in output. To make an 18 dB pad, you want the capacitance added to be 3X the capsule capacitance. ?LDC¡¯s are around 60-80 pF ?SDC¡¯s are 25-47pF ? Best Regards,
Jules Ryckebusch?
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On Apr 24, 2025, at 10:24, kandoit7 via groups.io <kandoit7@...> wrote:
? On Wed, Mar 19, 2025 at 09:19 AM, Jules Ryckebusch wrote:
If you go straight to a condenser without built in FET you can pad it with a capacitor. I¡¯ve used the 2555B with a 220pF capacitor as a drum mic.
Hello, Jules Ryckebusch.
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I have a question about this part.
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16mm ECM with no built-in Fet, as you said
If you reinforce the capacitor, can you withstand high SPL?
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How should I search for a connection method or related knowledge?
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Please give me some advice.
Thank you.
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Kandoit7.
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Moyzmo
Mic Scharf
Muninn