Originally Posted by
JBasham
Par for the course with this intercom. Glad you got yours working again. I am dithering around with a DIY breakout box that will allow me to connect standard ear buds and a budget lavaliere mic to the Chatterbox amplifier, so I don't need their headset hardware any more.
I finally got around to breadboarding some stuff on this.
The new Tandem Pro headsets have TRRS tips instead of 5-pin DIN. The static mic impedance for the new headsets is a little over 1k ohms, whereas the mics on the old 5-pin DIN headsets are more like 30 ohms flat. So you can't plug a new headset into an old communicator, even though the mnfr. sells a conversion cord. The mic on the new headset will be really, really loud in the ear of the person using the old headset.
I tried paralleling a 5k ohm potentiometer with the hot side and ground of the mic wires on the new headset. It seems to work well. I broke out the mic voltage line and the ground line, and connected the wiper end of the pot to the mic voltage line and one end of the pot resistor track to the ground line. Then I passed the mic voltage and ground signal back to the input feed on the Chatterbox. When I turn the pot knob to decrease the resistance, the pot resistance in parallel with the mic resistance drops the total impedance down to a level the old 5-pin Chatterbox can handle just fine.
Also, I made a breakout box so I can try using a $4 lapel mic and regular earbuds to feed into the Tandem/Chatterbox intercom unit and I won't need their headsets any more. I put two 3.5mm stereo input jacks on it, one for the mic and one for the earbuds. I put a 1k pot in series with the earbuds hot signal feed over to a TRRS jack. (Ran the ground over to the TRRS jack ground, 'natch.) And I wired a 5k pot parallel to the microphone hot and ground feeds over to the TRRS jack. The Chatterbox/Tandem amp connects to the breakout box through the TRRS jack. It seems to work well. Most earbuds are in the 16-30 ohm range so they match up well with the other guy using the Chatterbox/Tandem headset. The 1K series pot lets me adjust my earbud volume independently of the other guy who is using the volume on the Chatterbox/Tandem amp. And the parallel pot on the lapel mic is only necessary if I'm connecting with a guy using an old Chatterbox headset. If he's using a new one, the impedance on cheap lapel mics seems to be about 1k ohms, same as the new Tandem Pro headset mics.
Oh yeah, if you're trying to do this, the Tandem Pro headset pinout is Sleeve = Ground, Ring 2 = Mic , Ring 1= Ear, and Tip = Other ear. If you're using their boom mic headset instead of the helmet headset, the first ring isn't connected to anything -- it only has one ear speaker and that's on the tip.
The headset pinout for the Chatterbox 5-pin DIN units is available via Google Images.
I'll track test them next chance I get and I'll report back.
Last edited by JBasham; 03-26-2018 at 10:19 AM.
If God meant for man to motor-swap LS engines into track cars, He wouldn't have created Corvettes.
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