Headset mic connections

VE7ATJ_Don

I have a Steelseries V3 PC-Gamer headset which has a single 4-pin phone plug at the end (REar, LEar, Mic, Gnd).  Can I build an adapter to plug this into the 8-pin Foster on the 6500?  The diagram for the Foster shows Mic+ and Mic-.  Can I ground Mic-?  or do I need some sort of isolating capacitor from Mic- to ground?

Thanks for your help.

Michael Coslo

Yup, you can make an adapter. You'll need to find out if your mic is dynamic or electret in order to set it up correctly.

There shouldn't be a need for  a cap to ground at all. 

Ken - NM9P

They don't usually recommend connecting Mic- to the regular ground, because it unbalances the pseudo-balanced mic input on the front connector.  This has caused RF feedback problems in some stations. 

The issue for you is that the LH/RH headphone connection uses the same ground that your microphone uses.  So you will need to connect everything to chassis ground or your headphones won't work. 

Your options regarding the microphone are either:

1) leave mic- open and hope it will work against the chassis ground.

2) put a suitable capacitor from mic- to chassis ground on the connector to channel audio from mic- to ground which will give an audio path from mic- to ground, but won't unbalance the DC voltages at the pin.

3) Connect mic- to Ground and hope you don't have RF feedback problems

When building your adaptor, you might leave a connection to allow having the capacitor in or out, or shorting Mic- to ground and see which way it works best.

The other question.. if this is an electret mic that needs the bias turned on, will it receive proper voltage between Mic+ and Chassis ground?

I haven't experimented with any of these options.  Perhaps some others will clarify which one of the three are best.

Ken - NM9P

Tim - W4TME

Excellent suggestions and recommendations.

VE7ATJ_Don

Thanks guys. BTW, this is a dynamic mic -- sorry forgot to mention that. I'll give it a go and let you know how it works out!

WA2SQQ

I actually made an adapter box with both 2.5mm and 3.5mm female jacks. These accommodate just about any mobile headset used on cordless and mobile devices. For Standard 2.5mm Cellphone Headsets, also called Universal Headsets.
tip = microphone
ring = speaker
sleeve = ground

Note the Microphone is a electret condenser microphone so it will need bias voltage. To simplify matters i added the cap externally. wiring is simple I get the voltage from the mic plug on the Flex 6500. Feed the voltage to a 4,7K resistor. The other side of the resistor is connected to the + of  a capacitor, I used 47 uf . The junction of the resistor and capacitor gets connected to the Mic+ of the headset. Headset Mic ground gets connected to mic ground on Flex mic connector. An external PTT can be wired to the mic plug or the PTT connection on the rear of he 6500. I've tried several headsets - you'd be amazed how good some sound, one of my best purchased at my local "dollar store". EQ to your desired specification!

VE7ATJ_Don

Thanks WA2SQQ -- that's perfect.  I'll give it a try.

I have most of the rest of the adapter working (headset, etc.) but the mike wasn't working, so I'm guessing I'll have to do the 'bias' you are talking about here.  I wonder tho, wouldn't turning on the 'bias' setting on the radio setup dialogue do the same thing?  (I haven't tried it yet, but I will and let you know the results.)

Thanks again for all your help.

Don VE7ATJ

VE7ATJ_Don

Are you sure it's a 47uf capacitor?  Not a .47?  47uf seems like a lot of capacitance for audio levels....

WA2SQQ

I used 47 but I don't think the value is that critical you can certainly use a smaller value

VE7ATJ_Don

Well, a 'happy news' update. The mic in the headset is indeed an electret, so I do need to feed it some bias.  The great thing is that it is easily accomplished by simply selecting the 'bias' option on the phone tab of the Radio Settings dialogue!  -- so no need for wiring of capacitors and resistors from the 5v source on the mic jack. Everything appears to be working, with the mic centre pin connected to mic+ on the connector, and ground/shield going to ground.  (No connection at all to the mic- on the connector.)

I'll run this configuration for a couple of qso's and get some voice quality reports, and we'll see if we need to do more tweaking, or if there is any hum, etc.  (I can't hear any on the MON function, and I can't see any on the level meter when I'm speaking, so maybe it's all good!)

This is such an amazing radio!

Thanks again for everyone's help.

Don VE7ATJ