Electret mic wiring

K5CG

I have a Koss SB45 (has an electret condeser mic). Can the mic be wired directly to the Foster connector (pin 2 bias to ring, pin 7 to sleeve, pin 8 to tip)? Or must I add the current limiting resistor reistor and DC blocking capacitor? I am NOT buying some adapter, I am building my own. I want to know how to do this myself.
Thanks

Bill -VA3WTB

hope someone around can help with this

[Deleted User]

What is to figure out. You wire it like a regular mic and turn on the mic bias in the SDR setup menu.

K5CG

I must be ignorant or something. What is a "regular mic"?

I have a Koss SB40 which has a dynamic element. Maybe that's a regular mic? Tip to pin 8, Sleeve to Pin 7. Simple enough.

I don't believe that's the same as wiring an electret element. Somebody must have done this with an electret headset on a Flex 6000 before. It's not rocket surgery. Maybe I'm wrong.

I started this new topic specific to the Koss SB-45 because I had revived an old Yamaha CM500 thread improperly and the answers I was getting there were all off the mark. So here I am with a new topic and I asked a pretty easy question expecting maybe a Yes or No answer. If it is "No", then it would deeply appreciate a correction to my proposal.

I'm sorry to appear snarky but the the lack of comprehension on this board; "What is to figure out" is just more of the same non-specific answers I was getting on the other topic.

Bill -VA3WTB

Ok so you need to find out if the mic needs bias or not. If it needs it just do as he said and turn it on in setup. If it does not need it then wire it up and keep bias off.

k3Tim

What Bill said...  Here is the info from the 6000 series Hardware Manual:

6.1.2 Supported Microphone Types The FLEX-6000 front microphone connector can support either a dynamic or an electret microphone.  This is an unbalanced nominal 600 ohm impedance input.  The electret bias voltage is not enabled by default, and must be enabled by SmartSDR.   

I read that as the radio supports Electret or dynamic (aka. Regular). 

Your question is totally valid as one wouldn't want to pop the front end on one of these puppies. I would take regular mic to mean one that 'generates" an output signal / voltage w/o requiring application of an excitation voltage / bias.  And no you didn't come of snarky. 

Good Luck with the project. I spent about 2 hours this weekend making a cable up. I learned I should purchase premade next time.  :-)

Tim

Bill -VA3WTB

Yes I think if you wire it up as Tim says without turning the bias on, see if it has good audio, if not then just turn it on, and you may need the 20db boost as well.

K5CG

I know the mic needs bias. I need to know if the radio blocks DC on the input (pin 7 and or 8) or do I need to put a capacitor in my adapter.

k3Tim

I do not see the cap requirement being mentioned in the manual  snipit above. Some rigs require it but looks as if te Flex 6k does not.  

If you want to test w/o hurting the radio you can turn bias on and check the voltage on pin 7 to pin 8.  Placing a 4k resistor across these and measuring the voltage drop will give you a way to compute the dropping resistor value (if any) in the rig.  A drop of 50% shows the external and internal internal resistor are the same.

If you put a blocking Cap in at 7 or 8 no voltage will appear at the Mic, or maybe I misunderstand?

Bill is 100% right about he +20dB, forgot about that.

With Regards,
Tim

K5CG

Thanks Tim. I know if I apply bias to the sleeve on the headset connector it will also be present on the tip (headed into mic+ pin 8). So I need to be sure that there is a blocking cap in line already in the rig or I can add one. I suppose I can measure resistance from pin 8 to pin 7 and pin 8 to ground and see if it is open, that would be a good indication that I can't hurt anything if I go without the cap.

I'll post the final diagram once I'm done. It might be **** simple but I'm being extra careful to hurt the radio.

Thanks

[Deleted User]

Sorry regular mic to me is a dynamic mic. I didn't read the whole thread before responding.I was referring to generic electret wiring and not the Koss . . .  Sorry about that

K9DUR

I have a Yamaha CM-500 headset which has an electret mic.  I simply wired tip & ring to pin 8 & sleeve to pin 7.  Then I turned on the bias in SmartSDR.  In the case of the Yamaha, you have to turn off the +20dB mic boost because the ,ic element is so hot..

73, Ray, K9DUR

K5CG

Thank you Ray!

It's funny that your reply was about the CM500, which is why I posted my original question in another topic related to that headset. Full circle.

WA2SQQ

If the mic has only a 2 conductor plug, as most do, than the capacitor is located within the mic. I have found this to be the case with most electret condenser mics. Enabling the bias supplies voltage. The internal cap blocks the DC.

K5CG

Nope. Three conductors; tip, ring and sleeve.
Sleeve is easy, mic -
Tip must be the mic +
The ring has to be for bias.
I think I have what I need to at least experiment and see how to get modulation (into a dummy load of course!).
The radio doesn't arrive until Friday.

Thanks
Danny

K9DUR

Danny, in the case of my Yamaha CM-500, it has a stereo plug with the mic element hot side connected to both the tip & ring & the cold side connected to the sleeve.  This caused a problem using a Heil adapter because it has a mono jack & would short out the mic element when I tried to use it.  -- 73, Ray, K9DUR

WA2SQQ

OK, so I made an adapter so I can use a cordless telephone headset - actually sounds very nice! You can get 5V off the 7P mic connector.

Jay Nation

Ray

Thanks, after several tries at building an adapter for PC mic/headsets, your post suggested one wiring option I hadn't discovered, the headset cord terminates with one 3.5mm TRS mic plug and one 3.5mm TRS headphone plug, just like most other PC gaming headsets. I never could get it adapted to the 8 pin Foster connector before.

I used a 3.5mm extension cable, chopped off the female end and about 3 inches of the cord.

I soldered the shield/braid to pin 7 twisted together and tinned the tip and ring wires and soldered them to pin 8.

Then I enabled bias in radio setup.

WOW, why didn't I think of that. Works great no hum/no noise, rich/hot mic audio. rivals or maybe beats my PR781 and SM58 in sound quality.

And the headset will still likely work without the adapter, with Maestro.

73, Jay - NO5J

Jay Nation

I forgot to specify which headset ...

Cyber Acoustics AC 960 Educational Grade Language Lab headset.

Durable, Comfortable, and Cheap.
Oh, and it has knobs!
BTW the mic is an electret.

Newegg ...

http://www.newegg.com/Product/Product.aspx?Item=9SIA1UH3H80958

Walmart ...

http://www.walmart.com/ip/Cyber-Acoustics-Educational-Series-Stereo-Headset-with-Boom-Mic-AC-960/14277830

BestBuy ...

http://www.bestbuy.com/site/cyber-acoustics-pro-grade-w-mic-headset-black/1307173831.p?id=mp1307173831&skuId=1307173831

73, Jay - NO5J

VE6KWA

FYI... the Yamaha CM500 appears to be made by Koss. The Koss SB40 looks identical and at least in Canada is almost half the cost.   Ordered one today.

K5CG

The SB40 does look the same as the CM500, but the SB40 has a dynamic mic. The SB45, although not the same physical form factor, is more like the CM500 (with an electret mic).

VE6KWA

Interesting... as you say the SB40 is advertised as a dynamic mic, which is fine with me. From what I can dig up, apparently the early CM500 also was dynamic and was changed to electret later.  I see many great reviews of both the SB40 and the SB45 from hams, so looking forward to trying one.

K5CG

I have both the SB40 and SB45. I started this topic to figure out how to wire the SB45 with the electret mic.  Unfortunately, due to the SB45's use of the ring section of the connector, the adapter for it can't also be used with the SB40 which has no ring (it's part of the sleeve), so each headset will need a dedicated adapter.

I suspect once I've got both headsets working, I will have to evaluate comfort and audio reports to try to determine the one that is best overall for long term use. Switching back and forth, and having to also change radio settings (bias and boost) each time, will eventually get old.

I'll post some pictures and diagrams here once I'm done.

Danny
K2DMS
Plano, TX

VE6KWA

Looking forward to your comparison. You could wire the two adapters into the same foster. I did that before with a 3.5mm and a 1/4" phono on the same pigtail. Made mic changes easy. 

EA4GLI

I am interested in the comparison as well. I have the Yamaha CM500 which is a very comfortable headset that gets a great punchy audio. At half the price, if the SB45 matches the Yamaha that will be a great buy.

The leatherette in the pads of my yamaha are starting to peal off and those are not replaceable and there is a connection failure in the mic from moving the boom up and down. I have a backup Yamaha CM500 back home and will probably get another one just in case. But being able to add the Koss to the repertoire will be great if it is a good performer.

I was also going to suggest something similar to what Ken suggested. Have a short patch cable for either one of the headsets that allows you to use the same adapter. 

I would also like to add that the Yamaha comes with a very long cable and adds a little box where you can add batteries so you can use it with equipment that doesn't provide bias. The biggest gripe with the Yamaha and a reason for me to consider the koss is that the Yamaha has 2 separate cables from each speaker and the Koss only the one from the boom side.

K5CG

"Have a short patch cable for either one of the headsets that allows you to use the same adapter."

I have lots of connectors

VE6KWA

Just a quick note for anyone looking at the Koss SB45. I see this model advertised with either  Standard 3.5mm plugs OR a single USB plug. The USB would be great for remote but obviously not to wire to the radio.

Jay Nation

I've moved on to the Koss SB45 headset.
I use the same pigtail adapter I made for the Cyber Acoustics AC 960.
The SB45's are more comfortable. They're a better fit for my **** Head!!!

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  73, Jay - NO5J