TAS2563: Pilot Tone Amplitude and Presence

Hi Oren,

The pilot tone is used by the smart amp device to measure near-DC IV-sense from the speaker. This is the mechanism to measure the Re parameter in real time from the speaker.
Frequency and amplitude of this pilot tone are adjustable, although there are some limitations to keep it functional.

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan,

Can you please provide guidance on whether an adjustment is necessary to set it to -40 dB (?) and how to do it?  The default pilot tone amplitude is high enough to be noticeable (it modulates the tone) and its presence seems to be related to tuning, i.e., it's not present with a new "default" PPC3 project.

Thanks, O.R.

Hi Ivan,

Following up on my question...  The -40 dB pilot tone level is mentioned in Table 6.5 "Electrical Characteristics" relative to a 1 W output, which works out to ~28 mV.  Is the pilot tone level supposed to be fixed at ~28 mV or does it vary relative to audio level and/or frequency?  I measured ~126 mV.

Thanks, O.R.

Oren,

The amplitude of the pilot tone should be 187mV. I'll double check what would be the minimum amplitude required for the pilot tone to work properly.
Pilot tone should be triggered by the audio input content, you mean the tone is observed even if not playing audio?

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan,

No, the pilot tone is present only when the audio exceeds a level threshold and only with certain frequency content.

Thanks, O.R.

Hi Oren,

Then I think the operation is correct, your measured value is close to the expected one, and the pilot tone should be enabled only when playing audio.

Would 16Hz still cause intermodulation on your audio content? This is the lower frequency we can set the pilot tone. That is adjusted in some hidden settings, I can do that on your PPC3 file and send it back through the shared folder.

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan,

- Can you please comment about the "-40 dB pilot tone" relative to 1 W mentioned in the spec.?  The ~126 mV I measured is higher than that but the level is fixed when it's present.  My concern is that it's much higher than -40 dB relative to our audio levels.  Is it an issue?

- Is 16 Hz pilot tone behavior (i.e., active depending on audio content) and level the same as when it's 60 Hz?  Does the protection algorithm work in the same way with a "non-standard" pilot tone frequency?

- We would like to try 16 Hz so can you please provide instructions in the shared folder on how to change the pilot tone frequency in an existing PPC3 project file?  We are in the process of making other changes so ideally we would be able to go back and forth.

Thanks, O.R.

Hi Oren,

• Should not be an issue, usually speaker should not be too responsive at such low frequencies.
• 16Hz would be same behavior and protection works the same way, the level is not changed either.
• I'll share more details as soon as possible, I'm currently working on several other projects so this may be tomorrow during the day.

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan, have you been able to look into this?  Thanks, O.R.

Hi Oren,

I uploaded the latest ppc3 files I had for each speaker char to a new directory on the same shared drive link. Pilot tone should be set to 16Hz now; we have to do this change internally so if you need to change the pilot tone frequency on any other ppc3 file please share it and I'll send it back modified.

Best regards,
-Ivan Salazar
Applications Engineer

Hi Ivan, the new directory isn't showing up in the shared folder on our end.  I asked the FAE to verify our access code.  Thanks, O.R.

Oren,

Should be available now, sorry I was not uploading to the correct folder.

Best regards,
-Ivan Salazar
Applications Engineer

I see it now.  Thanks, O.R.

Hi Ivan, is there a way for us to change the pilot tone frequency ourselves?  What does it involve?  Thanks, O.R.

Hi Oren,

It requires a hidden setting which would need a password to enable. Unfortunately this is not something we can share directly with customers.

Best regards,
-Ivan Salazar
Applications Engineer