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Does anyone know if the audio PA for the 13 watt XTL5000 mobile radio is any different than the standard 7 watt audio PA? I do know that the HSN4031 speaker that comes with the standard 7 watt package is 8 ohms (measures 7.7 ohms), whereas the 13 watt option uses the HSN 4032 speaker, which is 4 ohms (measures 3.7 ohms).

BTW, I suspect the only difference MAY be the speaker (4 ohms vs/ 8 ohms), as the high level maintenance manual warns that with the 13 watt option, it has a "limited duty cycle." This is NOT stated with the standard 7 watt package. I can definitely imagine a PA final stage rated for 13 watts into a 4 ohm load, and rated at 7 watts into an 8 ohm load.

Then again, I can't see how they could justify the extra $'s for the high powered PA option if it merely involves a different impedance speaker, since I believe the cost of the HSN-4031A is very nearly identical to the cost of the HSN-4032A when purchased from Parts.

BTW, I can't seem to find any discussion of the actual PA circuitry in the high level maintenance manual, albeit I could have missed it. It appears to be totally silent on this issue, other than the cautionary note on the duty cycle limitation of the 13 watt option.

Thanks for any help on this!

Well, apologies for posting and not having an answer, but.... Just to let you know, you're not the first one to wonder the same thing. You articulated our thoughts very well and we, too, look forward to an informed response. Thanks for taking the time to ask the question.

The surprising thing to me is that the XTL 5000 Motorola high level maintenance manual does not cover any details whatsoever concerning the audio PA stage. If it did, it would take all of 10 seconds to get an answer to this question.

BTW, another odd thing about Motorola speakers: What is the difference, if any, between an HSN-6001C (I don't know what its wattage rating is) and an HSN-4032B (rated for 13 watts)? They both measure 3.2 ohms impedance, and the only difference I can find is that the word "Motorola" is blue in color on the 6001, and white in color on the 4032A. Also, the 6001 costs $111.00, while the 4032 is a "mere" $71.50. Go figure...

It is pretty clear that the only difference between 7 Watts and 13 Watts is the speaker.

The audio PA chip used in the XTL radio is capable of 22 Watts [TDA1519C].

Actually, there are two audio PA situations. If the XTL radio is used with a legacy W series head, the audio PA in the radio is used whereas the O5 head has its own audio PA[TAS5121]. That chip is capable of 100 Watts.

The test procedure in the service manual verifies that the radio has the capability of delivering 13 Watts across 3.2 ohms at less than 3% distortion.

Thanks for the outstanding clarification on this, xmo!

One last question on speakers:

What the heck is the difference between the 3.2 ohm HSN-6001C costing $111.30 (can't find its wattage rating) versus the 3.2 ohm HSN-4032B 13 watt speaker costing $71.50, a premium cost of almost 56%?

BTW, both of these speakers are of the non-waterproof variety.

HSN1006 is an amplified speaker requiring separate 12VDC.

The HSN-6001 is not a powered speaker.

xmo wrote:...the O5 head has its own audio PA[TAS5121]. That chip is capable of 100 Watts...

With the extremely limited amount of physical space availabe inside of an 05 CH to accomodate the heat sink on the internal 100 watt-capable PA chip, I gotta surmise that is why Motorola is so cautious with their "limited duty cycle" warning when running 13 watts (with a 3.2 ohm load). Even 13 watts sounds like a lot of heat to deal with inside of that little and very tightly packed plastic 05 control head box, not to mention all of the other sources of heat being generated by all of the other power hungy circuitry inside of that same little box.

I would guess that if one needs to have the receiver audio volume cranked up all day long, with constant receive chatter on a 24 x 7 basis (e.g., most patrol cop cars that don't have MDT's), the 05 CH mobile and/or desktop implementation using the 8 ohm speaker might be judicious thing to do. I say this in terms of not thermally stessing out the PA in the CH, let alone thermally stressing out the rest of the components inside the 05 (especially while inside of a 140 degree internal temp car parked in the Phoenix mid-day sun). Don't want to cause a premature chip failure inside of that pricey 05 head!

"...Even 13 watts sounds like a lot of heat to deal with inside of that little and very tightly packed plastic 05 control head ..."
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Maybe not as much of a heat issue as you would think based on conventional [linear] experience. The TAS5121 is a digital amplifier capable of over 90% efficiency into 4 ohms!

The TI datasheet says: "Because of the efficiency of the TAS5121, heatsinks are smaller than those required for linear amplifiers of equivalent performance."

Great point, xmo. Nevertheless, the fact that Motorola is going out of its way to overtly caution in its maintenance manual the "limited duty cycle" associated with 13 watt operation, as opposed to no such warning for operation at 7.5 watts, demonstrates that they have an issue with heat dissipation of the PA. Again, I would think applications involving industrial strength duty cycles, such as Police cars and the like (which are probably 75% of 05 CH applications), may not be wise to deploy the 3.2 ohm speaker.

I believe that warning has existed since the analog Spectra days & only refers to the 22-watt PA...not the O5 head PA. The info looks to have been cut & pasted with no further clarification.

Perfect, and I think we've put this issue to bed! I can drive on running 13 watts to my heart's delight!

Thanks for all of the help, guys!

xmo wrote:...there are two audio PA situations. If the XTL radio is used with a legacy W series head, the audio PA in the radio is used whereas the O5 head has its own audio PA[TAS5121]. That chip is capable of 100 Watts.

Hi. xmo!

I have noticed while driving around with the 03 HHCH (connected to an XTL5000) and experiencing rapid deep signal fades, that the speaker audio seems to almost sound like a snap, or sometimes makes a ""clanking" sort of sound, when shutting off/squelching on weak signal fades. However, this is not the case while using the 05 CH under these same signal conditions. BTW, the squelch setting was at factory default.

We tried this with two diffferent 03's and 05's, and we were using current model XTL5000 radios.

I'm wondering if you have noted this odd audio behavior with the 03 during rapid fade conditions (not picket fencing, though)? Is it possible that this has something to do with the PA in the 05 CH, as opposed to using the XTL's internal PA with the 03? I'm wondering if it might have something to do with the COMBINATION of an XTL5000 radio and an 03 HHCH, as it seems like if it was just the PA in the XTL, this would have been noticed by many.

BTW, I am pretty sure this is not a particular radio and/or CH hardware anomoly. We tried out 2 different XTL radios, and 2 sets of 03 and 05 CH's, and two different HLN-4032 13 watt speakers. The behavior was the same with both radios(and both speakers) and both sets of heads (e.g.,audio clanking sound on rapid squelch turn on with 03, but not 05, during deep rapid signal fade conditions).

The only reason I bring this up is that this audio "snapping/clanking" behavior is so annoying that I plan to change from an 03 to an 05 CH in my personal car, as it really bothers me.

ASTROMODAT, are you able to post an audio sample of what this sounds like? You might be able to simulate it on a service monitor by varying the RF level on a given test frequency.

Although your issue sounds like it may be a hardware problem (audio PA gate/cap charging times, etc.), Moto is able to work on audio anomalies at the firmware level. Point-in-case is the ASTRO Spectra Plus "static burst" sound (sounds like a digital click) at the beginning/end of CAI secure RX. One of Moto's largest users of AS+ secure radios (Jacksonville PD) complained like crazy to Moto about this, and it was resolved in firmware 14.

Perhaps Moto may be able to correct the problem you describe by tweaking the DSP firmware so as to eliminate it -- if it's not a hardware problem, of course.

As far as hardware, I don't think this is the issue, unless I am experiencing a profound coincidence,. We have now tried this set-up with 3 different XTL5000's (2 were 50 watt, and one was 100 watt), all conventional, and 3 different HHCH 03 's. Guess we'll just have to live with it.