[Elecraft] [KX3] New Product: SPX3 External Speaker

[Robert Morris]

Hi Don, 

Thanks for your feedback. I'm hoping one volume knob will do the job for
everyone else too. Plus, if the KX3 puts out enough signal for the PC,
then you don't really want an amplifier in the signal path. 

I want to be sure about the channel which needs to go to the sound card.
Are you saying the left channel from the KX3 is the one the computer
needs, or are you saying the computer needs the signal to be present on
the left channel of its input? If it's the latter, then that is already
how the SPX3 is wired. 

For the first prototype, the stereo output of the KX3 goes into the SPX3
input port, then is split. The left channel goes to the amplifier, and
the right goes to the left channel of the output port. Will that do the
job, or does the computer really need the signal which originated from
the left channel of the KX3? I don't see in the KX3 manual where it
specifies which channel the digital mode signal is output. I had assumed
it would be on both left and right channels. 

Thanks and 73,
Robert (AG6ZZ)

On 2018-04-15 21:24, Don Wilhelm wrote:

> Robert,
> 
> You will need to provide a means of connecting the KX2/KX3 PHONES output to a soundcard for the use of digital modes.
> 
> The KXSPA should connect to the left channel since that is the channel that is normally used by soundcard digital.
> 
> I think that means you would want to provide a knob controlled gain control on your active speaker so the sound level to the speakers can be controlled without disturbing the level to the soundcard being used for digital modes.
> 
> 73,
> Don W3FPR
> 
> On 4/15/2018 11:40 PM, Robert Morris wrote: 
> 
>> First of all, I want to say thanks to everyone for all the great feedback I've been getting on the speaker. Here's are some requested features:
>> 
>> 1. One stereo channel to speaker driver and another channel to output jack (already in first prototype)
>> 
>> 2. 12V input (planned is 9-15V, like the KX3)
>> 
>> 3. Separate powered (active) and unpowered (passive) speakers
>> The reasons I've gotten for this is that it would save on the weight of and inconvenience of charging a second battery
>> 
>> 4. Separate volume controls for the internal speaker driver and the output jack
>> The reason I've gotten for this is that a computer will need the volume set separately from the speaker.
>> Some have stated the computer's software can adjust the gain on the input, and that there only needs to be one volume control for the speaker driver. I'll need consensus on this from the digital mode folks.
>> 
>> 5. USB power output
>> This would be convenient for those who wish to use their speakers as phone chargers.
>> 
>> Things to consider:
>> 
>> A. Making two different speakers substantially increases manufacturing costs for the most expensive part; the enclosure. Since most folks will be fine with just one speaker, then the lower production numbers of the passive speaker would make its per unit cost much higher than the active one. However, folks would expect a lower price on the passive one. So, I'd have to sell them as pairs to justify manufacturing the passive ones, which would mean a higher cost to consumers who only want the active one. It would also increase the cost to those who want both because of the two different enclosures instead of just one enclosure twice.
>> 
>> B. The one issue which would force making both an active and a passive speaker is the need stated by some respondents that the active one would require a second volume control for the output to the computer for digital modes. It would be expensive and time consuming for me to try every digital mode software on every operating system, so I need confirmation whether this is truly necessary.
>> 
>> C. If a second volume control is not truly necessary, then that simplifies things tremendously. I'll wait for consensus on this before going into why.
>> 
>> D. A USB power output port is beyond the scope of the speaker's intended utility. Also, it would draw down the battery at the cost of significantly limiting how long the speaker could be used before needing a recharge. Furthermore, the extra hole and port would increase the cost while reducing ingress protection. Lastly, there's not much room in the small enclosure to accomodate nonessential items.
>> 
>> Thanks and 73,
>> Robert (AG6ZZ)
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