Trouble with your microphone? Read this...

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w-u-2-o
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Trouble with your microphone? Read this...

Postby w-u-2-o » Tue Oct 03, 2017 1:42 pm

Nearly everyone who reports trouble with their microphone is doing one of the following things wrong:

1. They have not read the user guide and made the proper connections. The user guide has a lot of faults, but identifying the connections on the microphone connectors is not one of them. You must make those connections properly. You must use a "stereo" TRS (tip, ring, shield) connector, you cannot use a mono tip-shield connector. Read your user guide, really read it, and understand which wire goes where. If you are not capable of making a microphone cable yourself (something that is a little disturbing in an amateur radio operator, I must say ;) ), there are a number of people/sources who will be happy to sell you what you need.

2. Using a unmodified PC microphone with a TRS connector and a rear panel attached PTT switch. Sadly this will not work. The reason is because the rear panel PTT connector is in parallel with the RING terminal on the front panel microphone TRS connector. That means the RING terminal on the microphone TRS connector will be shorted to ground when the PTT switch attached to the rear panel is closed. And, since the RING terminal on a PC microphone is used for the mic bias and is in parallel with the TIP terminal inside the microphone then this will cause the microphone to be shorted out whenever the PTT switch is used. This is also why you can get this to work with spacebar or mouse PTT, but NOT an external PTT switch. The answer to this problem is to re-wire the PC mic to not use the RING terminal.

3. Not turning on mic bias for a condenser microphone. If it's a condenser microphone and it doesn't work, you must make sure the mic bias is turned on. The user guides do a less good job at discussing how to do this. If you are lucky enough to have a 200D or an 8000 (and soon the 7000), this is easy, you can do it from the setup window (Setup > General > Hardware Config). On other radios you must open it up and make sure a jumper is placed properly. The jumper is in place by default from the factory.

4. Not turning on mic boost for a dynamic microphone. If it's a dynamic microphone and it doesn't work, you must make sure of two things a) the mic bias is turned off (see Item 2 above) and b) that mic boost is turned on. While you can get away with failing at (a), failing at (b), not activating mic boost, which is done from the setup window (Setup > Transmit) , will cause it not to work.

5. Not getting all of the audio levels set correctly. You must be hitting 0dB ALC to get the best performance from the radio. See the two audio setup thread that are "stickied" at the top of this forum.
kb3bf
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Re: Trouble with your microphone? Read this...

Postby kb3bf » Sun Jan 17, 2021 2:41 am

Question:

I noticed there is permanent 3.3V bias on the Mike tip (front) even though Mike is set to DEFAULT, Bias is OFF, and PTT OFF.
(Thetis 2.8.11, 7000DLE)

Do i need to put a series cap when installing a dynamic mike?
Why is there a Bias on the tip?

tnx.
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w-u-2-o
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Re: Trouble with your microphone? Read this...

Postby w-u-2-o » Sun Jan 17, 2021 3:37 pm

I believe the mic default setting is "Tip". Please confirm that's what you are set to.

I also believe that the PTT "Off" setting is incorrectly labeled. Referring to the Orion MKII schematic, there are only two possible hardware states for PTT, Tip or Ring. Thus setting PTT to "Off" probably sets it to "Tip". And the PTT input is pulled up on the board to 3.3V.

Note that the mic bias voltage is 3/4 x 3.3V, or 2.475V.

Change your PTT setting to "On", your Mic to "Tip" (if it isn't already) and please report what you find on the tip and ring of the mic connector with both Bias on and off.

BTW, this is very interesting. It sounds like a bug that's been festering for a while and I'm surprised it took this long to find it. I would never notice myself because I only use VAC.

Thanks,

Scott
W4WMT
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Re: Trouble with your microphone? Read this...

Postby W4WMT » Sun Jan 17, 2021 5:03 pm

w-u-2-o wrote:Note that the mic bias voltage is 3/4 x 3.3V, or 2.475V.

Scott


I think that's just a bit of leakage current. With "Bias" turned off, a 1 meg resistor pulls it down to just a few mV.

73, Bryan
kb3bf
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Re: Trouble with your microphone? Read this...

Postby kb3bf » Sun Jan 17, 2021 5:23 pm

OK Scott, thanks for getting back to me.

I confirm that default mike is TIP.
bias is OFF
PTT is ON

YET there is still 3.24V present on TIP. I am reading this with a Fluke 87 multimeter.
On Ring, I see a decaying 3.24V reading that slowly over a minute or so goes to zero.

what's next? Use a capacitor for a dynamic mike?

tnx

Chris
kb3bf
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Re: Trouble with your microphone? Read this...

Postby kb3bf » Sun Jan 17, 2021 5:26 pm

I forgot to mention I upgraded to v.2.811 when I noticed this in the previous versions. Same result.
Maybe I should learn how to set up VAC like you do.
Chris
kb3bf
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Re: Trouble with your microphone? Read this...

Postby kb3bf » Sun Jan 17, 2021 5:38 pm

Never mind, I made a mistake sorry. I am reading the decaying 3.3V on TIP, not RING. I should have waited long enough to notice the decay.
At first it appears there is bias present.

I guess I can proceed with the dynamic mike installation and let the bias decay.
sorry for the confusion.
I will report back when everything is installed.

Chris
kb3bf
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Re: Trouble with your microphone? Read this...

Postby kb3bf » Mon Jan 18, 2021 2:20 am

now that I know to ignore a slowly decaying bias on Mic Tip (with Bias off), i installed a dynamic Shure 55S and a D104 with a Primo dynamic element.
Both seem to be working fine, except when monitoring (MON) with headphones i need to cut way back on the Mic Gain to prevent audio feedback.
I am using VOX.
docrix
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Re: Trouble with your microphone? Read this...

Postby docrix » Thu Sep 30, 2021 9:00 pm

2. Using a unmodified PC microphone with a TRS connector and a rear panel attached PTT switch. Sadly this will not work.


You've got to be kidding... My first attempt was with a condenser mic that had a mono plug. sadly this will also not work.. I use a footswitch for PTT to the rear panel. If I don't enable PTT it doesn't work. If I do enable PTT, the radio is immediately keyed since the mic plug has a shield where the ring would have been and it grounds the signal. So I put together another setup that works in most of the civilized world - using a standard PC configured condenser mic - and now it also doesn't work, apparently by design.

Is there a possible workaround to this other than coming up with a custom wired connector? It seems that not one but TWO industry standard configurations have been ruled out by the current implementation.

(Don't get me started on the reversed APP power connector!).

Rick
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w-u-2-o
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Re: Trouble with your microphone? Read this...

Postby w-u-2-o » Thu Sep 30, 2021 11:50 pm

Rick,

I didn't design it, I'm just reporting on how it is designed.

You have to work with what you have. It's really no worse than having to wire up an RJ type or DIN type mic connector.

If it were up to me, all radios would be provisioned with an XLR mic connector into a fully balanced mic preamp. Alas this is not the case.

However I do agree that the use of standard TRS connectors in odd ways (be careful about the speaker outputs, too) can be incredibly confusing. Hence this very topic.

73,

Scott
docrix
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Re: Trouble with your microphone? Read this...

Postby docrix » Fri Oct 01, 2021 2:31 am

Thanks, Scott - didn't mean to shoot the messenger!

I really appreciate your post - it explained what was frustrating me. It just kind of shocked me that such a sophisticated design (in most ways) could have such a configuration.

Since I never anticipate using the ring on the mic connector as PTT, I will likely just put a TRS plug on in place of my mono connector and leave the ring open.

I had previously wondered why Elecraft used a mono 3.5 mm jack for the rear panel mic connector on the K3 and K4 - now I know.

Thanks again for the very helpful info. Hopefully it can find its way into a manual some day. I am brand new to the PC-based SDR world and still trying to establish my 'go-to' sources for information. It seems to be spread out all over the place.

Rick
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Re: Trouble with your microphone? Read this...

Postby Trucker » Tue Jul 26, 2022 4:19 am

Scott, my apologies if this is posted in the wrong place. I just wanted to say thank you for all the information you provide. I was having low audio reported from a couple of contacts. I found a post by you in this sub forum about going into Windows Sound settings and making adjustments to the microphone there ( I am using a $20 special from Amazon ...........USB condenser microphone). I am running Windows 11 PRO and found the section in Settings that allowed upping the mic gain. That made a big difference. I did not realize that the microphone gain slider in Thetis had no effect when piping the audio into the pc and Thetis instead of connecting a microphone to the front of the radio.
Still learning the 8000DLE and all the settings. slowly!!!
James
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w-u-2-o
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Re: Trouble with your microphone? Read this...

Postby w-u-2-o » Tue Jul 26, 2022 9:30 am

Glad you got it sorted, James :)

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