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? Morning all,
I’m on the hunt for some piezo tubes and came across this supplier:
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They seem to have a wide range of sizes and thicknesses available and I wondered what the theory is behind the dimensions of the tube for hydrophone purposes.?
Is bigger and thinner always going to be better?
Any insights gratefully received,?
Jack
Morning all,
I’m on the hunt for some piezo tubes and came across this supplier:
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They seem to have a wide range of sizes and thicknesses available and I wondered what the theory is behind the dimensions of the tube for hydrophone purposes.?
Is bigger and thinner always going to be better?
Any insights gratefully received,?
Jack
Stuart Green's - Earth Magnetometer Project
Today I stumbled upon an interesting project that might also be of interest to some mic builders.
It appears that Stuart recently detected a rare sine wave in the magnetosphere, during one of the strongest geomagnetic storms in the current solar cycle.
The following article contains lots of useful information about his DIY methods (IMHO). I dropped it to Heinz_Files.: ...Earth Magnetometer Project...?A interesting video on the topic:
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Re: Cheap USB powered condenser microphone. Need advice on design.
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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Re: Cheap USB powered condenser microphone. Need advice on design.
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?
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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.
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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.
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Re: Active noise cancelling for microphones in noisy environments - techniques?
Hi,
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This is a pretty late reply but I'll share what little knowledge I have in the field of speech enhancement. I apologize in advance if the information posted here is technically wrong or misleading as I have spent only a short amount of time on a research project concerning this topic.
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In the case of single channel and considering the scenarios described above:
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There are a plethora of methods in the current research space but the core concept has always been to use statistical methods to find a transformation such that the input mixture (noisy signal) can be segregated into either the speech waveform, noise waveform or both. This transformation can be done through a variety of methods such as: Linear systems, spectrogram based neural networks, end-to-end time-domain synthesis (Probably the one with the largest interest at the moment due to the advances in GEN-AI and computing resources) and more. In the case of Low-SNR speech enhancement most of the methods outlined above perform much better at cancelling out stationary/ergodic processes such as those found in aircraft noise (mostly mechanical with low variance in observed noise over time) compared to babble noise as the probability density function of speech from multiple speakers tend to be the same.
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Multi-channel:
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Multi-channel methods are an extension of single channel methods with the introduction of other signal sources and necessitating phase alignment with reference to the position of the source signal (speaker's voice). This method allows for 'pre-enhancement' of the incoming mixture through the subtraction of the phase aligned input signals. The 'pre-enhanced' signal can then be forwarded to the developed transformation scheme to further enhance the noisy mixture. Research that has focused on the use of multi-channel methods were found to perform better with even lower SNR speech signals especially for babble noise. Alternatively the incoming signals can be forwarded to the enhancement scheme to also derive the enhanced speech signal.
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A well-known approach to start from would be the Wiener filter due to its simplicity to implement and mature research based around it. This filter applies linear power coefficients to the observed mixture to enhance the signal without modifying the phase. For optimal enhancement the?optimal power spectral densities of both the noise and speech must be known and forwarded to the filter. Deriving these optimal coefficients can be done through the method of codebooks, linear systems and neural networks.
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Both of the methods proposed above can be implemented in 'real-time' it just depends on how fast your processing hardware is to perform the enhancement once the speech signal is received.
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Once again I must apologize if I have posted technically incorrect information here. I hope that the information contained in this reply is of some use.
?
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Re: Cheap USB powered condenser microphone. Need advice on design.
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.
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Thanks a lot! Found it on Mouser.ca since I'm in Canada, same part number!
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Re: Rode NT1-A requires 3 minutes warm-up time
When I connected the NT1-a to the audio interface today and turned on phantom power, it worked right away. I feel like the microphone is gradually working and sounding better since we started narrowing down the problem. For the past few days, when I'm not using the NT1-a, I've been storing it in a zip lock bag together with the silica pads. In addition, the environmental conditions have changed. It is no longer hot and humid and temperatures have dropped to between 8°C and 17.1°C (46,4°F and 62,6°F). Since the NT1-a seems to be very sensitive to humidity, this could also have a positive effect. All in all, I am very happy with this result and would like to thank you for your contributions and tips! I have learned a lot about dealing with used and non-functioning microphones and hope that this thread was also interesting for other mic builders. I like the fact that the NT1-a has very low self-noise and will experiment with it in the field. MANY THANKS!
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I purchased mine from Mfr. Part No. T520B107M010ATE070
Good morning David,
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I just discovered the same issue! I use my Sanken COS-11D and Countryman EMW using the Rode Wireless GO II on my Zoom F4 with great results.?
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However, I tried pluging directly into Rode VXLR + on my Zoom and on my studio mixer, and I get about 10db static noise compared to the Wireless GO II.?
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I tried 2 different VXLR+ with the same results.?
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Where did you get your 100uF tantalum capacitor?
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Thanks
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Good morning David,
?
I just discovered the same issue! I use my Sanken COS-11D and Countryman EMW using the Rode Wireless GO II on my Zoom F4 with great results.?
?
However, I tried pluging directly into Rode VXLR + on my Zoom and on my studio mixer, and I get about 10db static noise compared to the Wireless GO II.?
?
I tried 2 different VXLR+ with the same results.?
?
Where did you get your 100uF tantalum capacitor?
?
Thanks
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Re: Rode NT1-A requires 3 minutes warm-up time
On Wed, Nov 6, 2024 at 08:21 PM, Jerry Lee Marcel wrote:
This seems correct.
What about when the mic doesn't work?
Hi Jerry. Here are the results from today but I'm not sure if I was fast enough to measure all points before the mic started working. At some points I had to wait until the value on the scale settled. I'll try again tomorrow.
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A=6.58
B=8.42
C=1.30
D=0.63
E=8.24
F=16.32
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Do you know about a possibility maybe, to force the non-functional state? For example discharging all caps with a resistor (or one-by-one, to find the faulty slow charging one?) instead of waiting one day until the warm-up error occurs again? I'm just wondering.
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Re: Rode NT1-A requires 3 minutes warm-up time
Yes, that should work well - especially with the large number of gel packs toss in the bag after the washing machine. Yes, fine business. :-)
The capsule should be fine - they work well - BUT you may need to pay attention to the bias voltage level ... ask the experts whether the cheaper Chinese capsules can run at the higher voltage produced by RODE boards. Otherwise OK.
And, I have used various edge terminated capsules from Chinese vendors on eBay.com with satisfying results -but I realize your mileage may vary - check the voltage levels in any case.
Just my take. James
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Re: Rode NT1-A requires 3 minutes warm-up time
Many thanks Jerry!
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It was a bit hard to read, that's why I wanna make sure I measured the right points.
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I will measure the non-functioning state tomorrow at about the same time and send you the results.
?
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Re: Rode NT1-A requires 3 minutes warm-up time
This seems correct.
What about when the mic doen't work?
Le 06/11/2024 à 11:29, Heinz a écrit?:
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Show quoted text
On Wed, Nov 6, 2024 at 06:31 PM, Jerry Lee Marcel wrote:
Can you read the voltages on the various points?
Here you will find the results (mic working state):
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A=5.04
B=7.64
C=1.16
D=0.55
E=7.50
F=15.36
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Re: Rode NT1-A requires 3 minutes warm-up time
On Wed, Nov 6, 2024 at 06:31 PM, Jerry Lee Marcel wrote:
Can you read the voltages on the various points?
Here you will find the results (mic working state):
?
A=5.04
B=7.64
C=1.16
D=0.55
E=7.50
F=15.36
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Re: Rode NT1-A requires 3 minutes warm-up time
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Re: Rode NT1-A requires 3 minutes warm-up time
On Thu, Oct 31, 2024 at 07:45 PM, Jerry Lee Marcel wrote:
Can you check the various voltages circled in red in both cases?
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Hi Jerry. I measured various voltages on the circuit board in the working state (with reference to ground) but I'm sure I missed some. Can you circle the points on the circuit board that I missed?
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I apologize for the triple post. For some reason the pictures got messed up...
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Re: Rode NT1-A requires 3 minutes warm-up time
Having a spare capsule around is handy. A K47 copy isn’t acoustically like the original capsule, but it will work with the R?de flat-response circuit and is a popular upgrade. Edge terminated capsules have a large area around the outside of the capsule where moisture or fingerprints can cause leakage between the diaphragm clamping ring and the backplate. This is usually wrapped with insulating tape, but it is still more likely to leak than the insulating ring (the part of the diaphragm not covered by gold) around the edge of a center terminated capsule.
If you become interested in building mics, you will naturally accumulate capsules and circuit boards as you upgrade and experiment.
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Timothy Aguana
David Walton