Re: Rode NT1-A requires 3 minutes warm-up time
On Wed, Oct 30, 2024 at 12:18 PM, Arjay1949 wrote:
Take the measurement across the 2 capsule wires, where they are soldered to the PCB.? One terminal will be connected to ground, the other will be the output of the voltage multiplier low pass filter - which is the point we are interested in.
If that is where the problem lies, that DC voltage reading will be much lower when the mic is switched? first switched on, and will rise to about 50V when the mic? starts to work correctly.?
The voltage between ground and the voltage multiplier output itself will be the 'green circle' reading, and that will probably remain the same - at 68.7v - under both operational states.? (working and not).??
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Hi! I'm back in town and did the measurement.
Across the two capsule wires it's 10.2V when the microphone is working.?
To check the voltage when the mic is not working, I have to wait until tomorrow morning. Then it usually doesn't work and needs the warm-up time.?
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Re: Rode NT1-A requires 3 minutes warm-up time
On Wed, Oct 30, 2024 at 02:53 AM, Heinz wrote:
Another question would be when the measurement should be carried out.
You should make the measurement both when it works and when it doesn't work. If the voltage is not correct when the mic doesn't work, that would mean that the culprit is the bias generator. If the voltage is corect both when the mic worlks and when it doesn't, then the problem would lie elsewhere.
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Re: Rode NT1-A requires 3 minutes warm-up time
Take the measurement across the 2 capsule wires, where they are soldered to the PCB.? One terminal will be connected to ground, the other will be the output of the voltage multiplier low pass filter - which is the point we are interested in.
If that is where the problem lies, that DC voltage reading will be much lower when the mic is switched? first switched on, and will rise to about 50V when the mic? starts to work correctly.?
The voltage between ground and the voltage multiplier output itself will be the 'green circle' reading, and that will probably remain the same - at 68.7v - under both operational states.? (working and not).??
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On Wed, Oct 30, 2024 at 01:53 AM, Heinz wrote:
On Wed, Oct 30, 2024 at 08:23 AM, Arjay1949 wrote:
What voltage at the actual capsule termination itself?...
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Just to avoid any misunderstandings. Could you please be more specific. Where exactly should the measurement be taken?
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Another question would be when the measurement should be carried out. When the problem occurs, during the warm-up phase (this morning it took around 15 minutes...) or when the microphone is working?
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Many thanks!
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Heinz
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Re: Rode NT1-A requires 3 minutes warm-up time
On Wed, Oct 30, 2024 at 08:23 AM, Arjay1949 wrote:
What voltage at the actual capsule termination itself?...
?
Just to avoid any misunderstandings. Could you please be more specific. Where exactly should the measurement be taken?
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Another question would be when the measurement should be carried out. When the problem occurs, during the warm-up phase (this morning it took around 15 minutes...) or when the microphone is working?
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Many thanks!
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Heinz
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Re: Rode NT1-A requires 3 minutes warm-up time
On Tue, Oct 29, 2024 at 01:56 PM, Heinz wrote:
.... Green circle test pad: 68.7 ...
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What voltage at the actual capsule termination itself?...
With a DMM that has an impdedance of c.10M - which is typical- then you you still measure something around 50v across the capsule...
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Re: Rode NT1-A requires 3 minutes warm-up time
On Tue, Oct 29, 2024 at 03:25 PM, @jp8 wrote:
I'd first make sure the CMOS oscillator gets powered. Connect the DMM ground lead to the NT1-A chassis. Press the red probe on the gold-plated test pad next to the IC, marked with a red circle in attached picture and turn phantom power on. With the body open, it will pick up a lot of hum. Do not output the signal of the preamp to an amp and speakers. You should measure approximately 15V. Then measure on the other test pad, marked with a green circle. Here, you should measure something like 60 to 73V, depending on your DMM input impedance.
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Hi Jan! Here you will find the measurements.
Red circle test pad: 15.2
Green circle test pad: 68.7
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@Arjay1949
Thanks also for your explanations!
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Re: Cheap electrets that go up to 40kHz?
The EM258 has a very useful ouptut at 40KHz.? ?At 80Khz it's almost nothing -- although it will still register something, just above the noise!
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MEMS microphone capsules like those listed here: ? ?have a much better ultrasonic response.
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On Mon, Oct 28, 2024 at 11:51 PM, Jonas Gruska wrote:
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Primo EM258 goes up to 80 kHz.
On Oct 29, 2024, at 08:45, cx b via groups.io <clistburnham@...> wrote:
Hi all -
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Any recommendations for cheap-ish electret elements that go up to 40kHz?
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Thanks!
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Re: Rode NT1-A requires 3 minutes warm-up time
The meter will do the job, though you cannot accurately measure the capsule voltage like Arjay1949 already said. Capsule voltage will indeed be 73V, not 100V or more like I first said. That was based on my false assumption that it would have the same circuit as the NT5 that I have, which has something like 107V when measured with a 1GOhm meter. We could assume your meter is 10MOhm and? and make estimations of voltages to expect on certain nodes in the circuit.
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I'd first make sure the CMOS oscillator gets powered. Connect the DMM ground lead to the NT1-A chassis. Press the red probe on the gold-plated test pad next to the IC, marked with a red circle in attached picture and turn phantom power on. With the body open, it will pick up a lot of hum. Do not output the signal of the preamp to an amp and speakers. You should measure approximately 15V. Then measure on the other test pad, marked with a green circle. Here, you should measure something like 60 to 73V, depending on your DMM input impedance.
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Jan
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Re: Cheap electrets that go up to 40kHz?
Primo EM258 goes up to 80 kHz.
toggle quoted message
Show quoted text
On Oct 29, 2024, at 08:45, cx b via groups.io <clistburnham@...> wrote:
? Hi all -
Any recommendations for cheap-ish electret elements that go up to 40kHz?
Thanks!
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Cheap electrets that go up to 40kHz?
Hi all -
Any recommendations for cheap-ish electret elements that go up to 40kHz?
Thanks!
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Re: Rode NT1-A requires 3 minutes warm-up time
I have a? Rode NT1 which is very simlar to the NT1A in many respects. There only appear to be minor differences to the schematic linked to in post #2 of this thread.
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I've had it for about 7 year now, and last year the sensitivity dropped dramatically. Almost no output.
I was surpised to find that the polarisation voltage across that capsule was way lower than it should have been - even though the voltage multiplier was outputting the correct ouput voltage.
It's not easy to measure the actual polaristion voltage directly with any accuracy -- connecting a DMM will shunt the output filter 4M7 resistor, so that the 73v voltage generator output will measure more like 50v.? ?In my case it was a lot lower than that - more like 10v !?
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I desoldered the final output capacitor ( on the NT1 that is C8 - the large 0.1uF cap adjacent to the? actual capsule termination pad. )? Underneath was what looked like dust. Removed that, and cleaned underneath with iso prop alcohol. Resoldered, and was able to measure the voltage across that capacior as 45v? (should be around 50v for the NT1-A).
Mic has performed perfectly since.....?
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(The actual voltage figures are slightly lower for the NT1 - it used a 13v zener as opposed to the 15v of the NT1-A.
The figures I describe above refer to the expected NT1-A figures).
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Re: Rode NT1-A requires 3 minutes warm-up time
On Sun, Oct 27, 2024 at 05:06 PM, @jp8 wrote:
Found today. It seems I'm not the only one.?
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Re: Rode NT1-A requires 3 minutes warm-up time
On Sun, Oct 27, 2024 at 05:06 PM, @jp8 wrote:
If you have a multimeter and you're willing to spend some time on fault analysis,? I can guide you through the process. By doing this, you can at least exclude the capsule from being the culprit.
Hi Jan. Yeah, it's a pity but not too bad either. ?At least we were able to achieve partial success and I no longer have any interruptions during the recording process. That's really something!
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I'm busy this week. But there's no rush anyway. Please let me know when it suits you best.
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Many thanks!
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Heinz
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Re: Rode NT1-A requires 3 minutes warm-up time
On Sun, Oct 27, 2024 at 07:15 AM, Richards wrote:
While I am NOT an expert, it just sorta kinda almost seems it might perhaps possibly be a capacitor or two on the circuit board taking a long time to charge up - sorta like an old camera flash unit taking longer than normal to charge its thyrister so it can flash a full blast.
That's what I thought when I came across a pair of speakers from the 1970th that nobody wanted anymore and that were thrown at me because everyone knew that I like listening to sound and analogue equipment.
When I opened the speakers and saw the old crossovers, my first thought was, "Omg, how am I going to replace those ones?! They must have almost certainly dried out after occupying storage space for decades."
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The only thing I knew was that the speakers were from a Pioneer S-77M Turntable Stereo. I looked for technical information but couldn't find anything useful. So I tried to find information about these old metal caps and came across an interesting article that might also be of interest to some of you. The article was published in Italian by Emilio Ciardiello on the German site radiomuseum.org with the title ¡°Replacing Old Capacitors¡± and contains, in my humble opinion, a lot of useful information about (old) capacitors in general and error analysis tips. This may not be relevant to micbuilders and would probably be difficult to understand for someone unfamiliar with the subject matter, like me :-). Anyway, I dropped the English translation of the article to the files section. ?
The following takeaways were relevant to me at that time:
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1.? Capacitance meter and insulation meter are usually required to trace faulty capacitors.? To this day I do not own either of these.
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2. The substitution of properly working parts with more or less similar components is useless, may impair the operation of the equipment and may also result in additional failures. Original components, when still good, are stable and not subjected to infant mortality.
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3.? When first handling any old equipment it is advisable to perform some preliminary operations before replacing components. After a good cleaning, a visual inspection returns a first list of damaged parts, as hardened rubber cables or cracked capacitors that must be replaced before power-up. As a general rule, if the equipment was stored for a long while, six months or more, regardless of its previous operative conditions, a soft wake-up procedure should be run to allow reforming of electrolytic capacitors and of selenium rectifiers, if any. It is advisable to run equipment at about half voltage for half an hour, monitoring B+ voltage and watching for fluid losses from electrolytic capacitors, for overheat of components, hum and other alarming conditions.
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So I removed and checked the speaker drivers for any defects (there were none...). (I replaced the aged and smelling needle felt inside the speaker housing...).
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Checked and replaced any faulty or loose connections (there were some...).? And connected the speakers in series to the amplifier, ?as a soft wake-up procedure to allow the reforming of the capacitors,? when switching it on and using it for the first time.
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That was three years ago and the effort was worth it. To this day, I really appreciate the lovely sound of these aged speakers. Of course, I will never know whether the gentle wake-up procedure made a difference, but to my understanding this approach made sense. After so many years, the old crossovers in the speakers still work perfectly.
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Many thanks!
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Heinz
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@Richards
You are absolutely right. Repairing the NT1-a could quickly become expensive, especially since I do not have the original purchase receipt.
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Re: Rode NT1-A requires 3 minutes warm-up time
Hmm, what a bummer! Could very well be the polarization voltage oscillator or voltage multiplier circuit following that oscillator that are not working. That's the 14-pin IC and surrounding parts on the board. My first suspect was C20, for which R?de has used an SMT film cap that was notorious for cracking. But C20 is a through-hole (wired) part on this board. A next likely, and not uncommon issue, is a cracked SMT capacitor in said oscillator circuit. But those cracks are in most cases microscopic and only visible by cutting the part and watching under an electron microscope. If you have a multimeter and you're willing to spend some time on fault analysis,? I can guide you through the process. By doing this, you can at least exclude the capsule from being the cullprit.
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Suppose you send in the mike to R?de for repair, I assume they will not do a repair at component level but simply do a board swap. Like others already mentioned, this is probably not economical. Ask for a quote before sending in the mike.
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Good luck!
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Jan
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Re: Rode NT1-A requires 3 minutes warm-up time
My gut feeling tells me that it could be a defective capacitor. But that's pure speculation.
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That is my Wild Alex Guess, as well. While I am NOT an expert, it just sorta kinda almost seems it might perhaps possibly be a capacitor or two on the circuit board taking a long time to charge up - sorta like an old camera flash unit taking longer than normal to charge its thyrister so it can flash a full blast.
But then, sending it to RODE for service makes sense only if the repair bill, coupled with the cost of shipping AND the initial cost of acquisition is a comparative bargain versus the cost of a new one under warranty or another model you might prefer over the long haul.
Just saying - I am NOT being critical in any way. The same sort of economic considerations apply in other hobbies, such as the comparative cost to restore an old MG or Triumph sports car often exceeds its restored resale value, or the cost to restore an ancient fountain pen relative to its restored resale value, and so forth.
Good luck. James
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Re: Rode NT1-A requires 3 minutes warm-up time
On Sat, Oct 26, 2024 at 06:48 AM, Richard Lee wrote:
I think the muck on your PCB coupled with humidity, was making the polarizing voltage generator wonky.? After 3 min. the warmth of the electronics dried the stuff enough for it to work again.? The polarizing voltage has some serious decoupling to remove any noise in the generator.
After yesterday's long-term recording test, I have good news and bad news.
The good news is that there were no unexpected interruptions during the entire recording process. The bad news is that the 3 minutes warm-up phenomenon occurred again this morning.
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The technical data of the NT1-a include:
Acoustic Principle: Externally polarized 25mm (1¡±) condenser
Features: True Condenser (externally biased)?
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From a beginner's point of view, I would like to properly understand what "True Condenser (externally biased)" means. Which might be boring for the pros.
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Shure describes it this way:
There are two types of condenser microphones: a permanently biased condenser, usually called an electret condenser, and an externally biased condenser, usually called a true condenser. These days, when people say "condenser microphone", they usually mean, "electret condenser microphone". Probably ninety-five percent of the condenser microphones on the market are the electret type.
The electret has a charged backplate that is created when the microphone is manufactured. A true condenser, on the other hand, continuously requires an external charge. This external charge may come in the form of any external box attached to the microphone, or it may come from the electronics built into the housing of the microphone. To put it simply, true condenser microphones have active electronics that need an external power source.? The basics are that it is a positive voltage (Phantom Power from 12 volts to 48 volts DC) that runs on pins 2 and 3 in an XLR cable. The word phantom is used because the power source is essentially invisible, running through the same cord that the audio signal flows through (Source: sageaudio).?
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Jules Ryckebusch described it very well this way. That voltage charges the mic capsule, which is a capacitor or ¡°condenser¡± in 1930¡¯s speak.
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According to a Sound on Sound condenser mic life discussion:
A DC-biased capacitor mic should go on forever. There is no inherent deterioration process in the capsule itself. Dirt on the diaphragm (or a very high humidity environment) will cause temporary charge leakage that will reduce the output level and lead to hissing and/or 'frying' noises, but that can be cleaned and performance fully restored by a skilled technician.
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On the other hand, an electret mic can lose the internal stored charge over time and that will also reduce output level and increase noise. Early electret mics (from the 70s and 80s) are much worse for this than modern designs which are vastly improved and can expect a life of 50 years or more.
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If a true condenser sounds dull it could be a contaminated diaphragm -- especially if it has been used a lot on close vocals without a pop screen, or in a smokey environment -- or it could conceivably be because the diaphragm has stretched if used in front of very loud sources (especially kick drums). Alternatively, it could be caused by deteriorating components -- especially aging capacitors -- in the impedance converter electronics.
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In case of the NT1-a I can't say how it was treated. The capsule doesn¡¯t sound dull or noisy at all, as soon as it is operational. So, I¡¯m tempted to conclude that a component in the impedance converter electronics seems to have deteriorated which results in the slow magnetizing process of the diaphragm. My gut feeling tells me that it could be a defective capacitor. But that's pure speculation.
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Since the NT1-a is a 2018 model and my electronic circuit troubleshooting skills are not sufficient to determine the root cause, I should send it to Rode for maintenance.
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If anyone has any other ideas, I would be happy to carry out further error analysis. But I'm afraid I'll definitely need detailed instructions.
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Otherwise I will send it to Rode next week.
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Many thanks to all of you!
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Have a nice weekend.
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Heinz
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Re: Rode NT1-A requires 3 minutes warm-up time
In da 80s, I didn't like ANY of the conformal coatings for the HiZ part of any PCB.? Modern stuff might be OK but I have no experience. Supposedly you can solder through this stuff: ...I got some for a project but didn't actually end up using it (for other reasons). -c
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Re: Rode NT1-A requires 3 minutes warm-up time
I've tried - the finest small soft artist's brush, distilled water, the slightest touch with wet bristles near parallel to the diaphragm -? the answer, for most of us mortals, is... no. Gold comes off. And from your photos, the capsule doesn't look that bad for its age, nor do I think it's the capsule that would cause the problem you're observing.
I would use a blower brush (for camera lenses) and VERY GENTLY remove any loose stuff.? I would NOT USE ANY LIQUID or ANY HIGH PRESSURE AIR.
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Yes, you might remove some Gold but actually the capsule will work fine with a bit of Gold missing :)? The real danger is your liquid moving yuck behind the diaphragm.? Then the mike will be forever / intermittently noisy. :(
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I think Josephson or one of the other commercial mike makers said you DON'T TRY CLEANING CAPSULES UNLESS YOU CAN REPLACE THE CAPSULE IF IT ALL GOES TO SHIT.? I second this as an ex commercial mike maker.
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From your description, I don't think you have a dirty capsule.? This would be VERY NOISY long before it stops working.
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I think the muck on your PCB coupled with humidity, was making the polarizing voltage generator wonky.? After 3 min. the warmth of the electronics dried the stuff enough for it to work again.? The polarizing voltage has some serious decoupling to remove any noise in the generator.
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In da 80s, I didn't like ANY of the conformal coatings for the HiZ part of any PCB.? Modern stuff might be OK but I have no experience.
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Re: Rode NT1-A requires 3 minutes warm-up time
Happy to help, no problem! Nice to hear it seems the mic is working properly now!?
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Enjoy your purchase.
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Jan
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