This might be a dumb question. But I am confused so here goes..
I have a Lightspeed Zulu 2 headset, and it has options for to be used in a 'mono' mode as well as the 'stereo' mode. (This called DIP switch, and factory default is to have this in the 'mono' mode).
So if I plug in the Zulu headset with factory setting ('mono' mode), will the fuse in GMA 240 blow? How can I find out without damaging my 800$ unit!!!
Ashish
Hello Ashish,
This is not a dumb question at all. Let us make it very clear.
A stereo headset is safe to use with the GMA240 no matter how any switch is set!
The stereo/mono switch on the headset OR the optionally installed stereo/mono switch shown in the diagram below may be set to any position
with a stereo headset and there is no risk of blowing the internal fuse.
The mono/stereo switch in your Zulu does not switch the ring to ground, it connects the ring and tip so a mono audio signal supplied to the tip can be heard in both channels on a stereo headset.
The design of the stereo phone jack used on each stereo headset provides isolation between the tip and ring and can never short either to the sleeve (ground) shown in this diagram.
As suggested in the installation manual and by others here, it is not typically easy to blow this fuse.
For example, I have a GMA240 running on a bench with XM music fed into Music Input 2 from a Garmin portable. The music volume on the portable is set to 3/4 scale (quite high). The Music 2 input is selected on the GMA240. The headphone jacks are wired for stereo and there is no mono/stereo switch in the jack circuit. I have a multimeter monitoring the input current (which is flowing through the internal 1 amp protection fuse).
With the music turned to a normal listening volume and a Zulu stereo headset plugged in, the current is 0.22 amps. If I turn the music volume up to an almost unbearable volume using the music volume knob on the GMA240, the currrent is still 0.22 amps.
Now, if I return the music volume to a normal listening level and put a grounding clip between the ring and sleeve to ground (short) the right audio output channel to simulate a mono headset jack being inserted, the current only increases slightly to 0.23 amps. Still no problem with ever blowing the 1 amp internal fuse.
Now, with the right output channel still shorted to ground, I increase the music volume (again using the music volume control on the GMA240) to that almost unbearable level, the current increases to 0.35 amps. Still no problem with ever blowing the 1 amp internal fuse.
Now, with everything still shorted, I remove the headsets to protect my ears and crank the music volume up to the point where I worry that my headset might be damaged, the current increases to roughly 0.60 amps maximum. Still lots of margin and no blown fuse after several seconds of operation at a level that I would never select.
With multiple headsets plugged in and shorting the right audio channel to ground, and the music volume turned up high, you could indeed reach a point where the 1 amp internal fuse is blown. The GMA340 has a 4 amp internal fuse to protect the power supply, and we are not sure one of those has ever blown.
The GMA240 installation manual requires that power be supplied to the GMA240 through a 1 amp external circuit breaker or fuse. One of the many options we are considering is simply increasing the size of the internal fuse from 1 amp to something large enough that it will never blow before the external 1 amp protection is tripped in the event that any headsets are improperly shorting the right audio channel to ground and a very high volume is being used.
In summary, with your stereo headsets, wire your phono jacks for stereo and don't worry about anything. Nothing you can do with switches can cause a problem.
Thanks,
Steve
P.S. If you experience a problem with your GMA240, please call us and let us work with you.