Microphone Bias

yack9
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Joined: Sat Jun 24, 2017 7:24 pm

Microphone Bias

Postby yack9 » Sun Dec 31, 2017 2:32 am

Does anybody know what the Anan 200D bias voltage and current ratings are?
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w-u-2-o
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Re: Microphone Bias

Postby w-u-2-o » Sun Dec 31, 2017 4:30 pm

Wait, let me type "bias" into the forum search box.

Searching...searching...hmmm, fifth citation down:

https://apache-labs.com/community/viewtopic.php?f=12&t=2612&p=4075&hilit=bias#p4075

It also happens to be the first sticky thread in this sub-forum.

Search is your friend ;)

73,

Scott
yack9
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Re: Microphone Bias

Postby yack9 » Sun Dec 31, 2017 6:52 pm

I did a search and didn't get that in my results. So sorry to have bothered you.
yack9
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Joined: Sat Jun 24, 2017 7:24 pm

Re: Microphone Bias

Postby yack9 » Sun Dec 31, 2017 6:57 pm

I'm only seeing 2.5vdc I'd ask if that was in normal range, but I'm sure if I do a search.......
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w-u-2-o
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Re: Microphone Bias

Postby w-u-2-o » Sun Dec 31, 2017 8:49 pm

2.5VDC seems low. I'll measure mine here later and see if it's the same.
yack9
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Joined: Sat Jun 24, 2017 7:24 pm

Re: Microphone Bias

Postby yack9 » Sun Dec 31, 2017 8:59 pm

With a different cable, I get 3.2vdc. Trying to make sure there isn't something physically wrong with my radio. I normally use a dynamic mic and was considering trying a condenser mic. I leave the bias switched off with the dynamic mic and had never measured the voltage before, which is why I was curious as to if there was a voltage range considered normal. The users guide simply states "small voltage". I had not seen 5vdc specified before your reply. I understand it's a holiday weekend. No big hurry. Thank you.

73, Scott n8umw.
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w-u-2-o
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Re: Microphone Bias

Postby w-u-2-o » Sun Dec 31, 2017 9:23 pm

I just checked the data sheet and schematics again. It looks like I have an error in my other post, which I'll go back and correct.

The data sheet, on Page 1-5, says that the mic bias voltage is 3/4 AVDD nominal. On the schematic, AVDD is 3.3VDC. So that would make the mic bias voltage approx. 2.5VDC, which is exactly what you are measuring.

Note also that this is delivered to the MIC via a 3.3K series resistor. If you meter is not sufficiently high impedance you might see a little voltage drop there, but that seems unlikely.

So it looks like your radio is OK.

73,

Scott
yack9
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Joined: Sat Jun 24, 2017 7:24 pm

Re: Microphone Bias

Postby yack9 » Mon Jan 01, 2018 3:39 am

Very good. I guess I wonder why it didn't specify in the users manual. That makes me feel better as I've had no issues the year and a half I have owned this radio. I do appreciate the help. I did my original search using "microphone bias" in the search string. I didn't see the other post come up. I am currently running an Audio Technica ATR-1500, which does sound very good on the radio. I may research and try a condenser computer mic of good quality.

Thanks and Happy New Year
73, Scott, N8UMW
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w-u-2-o
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Re: Microphone Bias

Postby w-u-2-o » Mon Jan 01, 2018 2:46 pm

The user guides are written by volunteers and are, unfortunately, neither complete nor correct in all respects. Plus, the open source software and firmware changes rapidly and the user guides are not updated to match. I've thought about tackling something myself, but with over 40 pages of setup screens before you even get to the main console, it would be a real labor of love! With good participation, this forum will ultimately hold much of that information.

The good news is that with the unparalleled audio processing capabilities of PowerSDR mRX, matched only by those using external rack or DAW processing, you can make any microphone element that costs more than $5 sound good. Do be sure to take a look at this thread if you haven't already, and watch Rob's excellent video.

If you want to get close to the pinnacle, take a look at this thread. It does ramble on a bit, but the bottom line is that there are a number of outstanding, large diameter, condenser microphones in the under $100 category, including the B1 and the MXL990, among others. With a very inexpensive external mixer to get enough bias voltage to run them, they, combined with PowerSDR, can make you sound like a million bucks for a lot less than the traditional Heil-do-your-EQ-in-the-mic approach.

73,

Scott
yack9
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Joined: Sat Jun 24, 2017 7:24 pm

Re: Microphone Bias

Postby yack9 » Tue Jan 02, 2018 3:16 am

I had RF issues with the audio chain the last time I tried a studio condenser. I'm on a second floor with a ground run that may be a resonant length on ten meters. I did make some changes since then and can now run an amp without some of the strange results that I was getting. I should try that setup again and see if those issues are gone. That mic sounded extremely good on the 200D. I have the plain, no effects version of the ART tube studio preamp and Rode NT1 mic. Never had any RF issues with it on my other SDR. I'll let tou know how it turns out.

73 from the other Scott
n8umw.
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w-u-2-o
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Re: Microphone Bias

Postby w-u-2-o » Tue Jan 02, 2018 12:59 pm

Oh, you've got some fabulous stuff there! It would be a real shame not to use that! If you haven't seen Rob's guide on how best to attach a professional, line level, balanced audio output to your unbalanced line input, do take a quick look. Using a transformer is definitely the best way. You can buy those pre-made, of course (so-called "hum eliminators" and whatnot).

I also have a second story shack (studio, really), with a second story ground run. I'm grounded and bonded to a fare thee well, including all computers, network equipment, etc. Just one snap on ferrite next to each XLR microphone connector, that's it. At 500W I have no problems, but my antennas are not too close to the house. If you're problem is only on 10M, just add an extra meter or two of ground wire ;)

73!

Scott

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