PA Chime Generator: Difference between revisions

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* In April, a BT8040N was extracted from an eBay-purchased InterM PA-1000BR amplifier. While functional - the sound wasn't quite right (more on this below).

* A Texas Instruments C2000 evaluation board was selected as the "brains" per familiarity in the designer's day job. Over the course of months, code was written to control the chime, microphone mute, button LED and a small LCD display via button trigger. The code functionality is described in more detail in a separate section.

* In August, a ~~BX4230K~~ came onto the market via eBay, extracted from an Inkel PA-9100RC (the exact model previously owned by Fairway). This chip sounds exactly right.

* In August, a BXA4230K came onto the market via eBay, extracted from an Inkel PA-9100RC (the exact model previously owned by Fairway). This chip sounds exactly right.

== Design ==

The preliminary schematic shown in March is mostly accurate. Modification include (but are not limited to):

* The addition of a C2000 microcontroller board (EVM), LCD, button and indicator LED (embedded in the button).

* The addition of a bandpass filter and DC biasing, as is present in the Inkel PA-9100RC (as originally mentioned in February).

* Power supplies to produce +5 V and +3.3 V for the analog and digital supplies, respectively.

When and if time permits, a final schematic will be produced to show the as-built hardware in its entirety.

== BT8040N versus BXA4230K ==

While these parts are pin-for-pin compatible, and seemingly listed as drop-in replacements, there is no doubt that the BXA4230K has a distinctly different sound than the BT8040N. The tone progression interval, pacing and decay (with external circuits) are very similar. The BX4230K, however, has lower fundamental tones, and additional harmonics and/or sustained tones. I don't have captured audio samples - but I can say that if you've heard the PA-9100RC chime, you won't be satisfied with the BT8040N. I wasn't.

== Future ==

The LCD display was primarily added to provide a visual level cue to the announcer. The PA microphone is very sensitive to proximity and volume; too far away or too quiet and the PA announcement isn't sufficiently audible. This seemed like a larger issue in 2020; as of 2021, though, the staff is doing quite well making clear announcements. The development semi-extensive code to add a graphical Vu meter (with louder/software cues) to the LCD seems unnecessary at this time.

The hardware is mostly ready for feeding the microphone signal into a low-passed ADC input for microphone monitoring when and if this feature is ever to be developed.

@@ Line 58: / Line 58: @@
 * In April, a BT8040N was extracted from an eBay-purchased InterM PA-1000BR amplifier.  While functional - the sound wasn't <i>quite right</i> (more on this below).
 * A Texas Instruments C2000 evaluation board was selected as the "brains" per familiarity in the designer's day job.  Over the course of months, code was written to control the chime, microphone mute, button LED and a small LCD display via button trigger.  The code functionality is described in more detail in a separate section.
-* In August, a BX4230K came onto the market via eBay, extracted from an Inkel PA-9100RC (the exact model previously owned by Fairway).  This chip <i>sounds exactly right</i>.
+* In August, a BXA4230K came onto the market via eBay, extracted from an Inkel PA-9100RC (the exact model previously owned by Fairway).  This chip <i>sounds exactly right</i>.
+== Design ==
+The preliminary schematic shown in March is mostly accurate.  Modification include (but are not limited to):
+* The addition of a C2000 microcontroller board (EVM), LCD, button and indicator LED (embedded in the button).
+* The addition of a bandpass filter and DC biasing, as is present in the Inkel PA-9100RC (as originally mentioned in February).
+* Power supplies to produce +5 V and +3.3 V for the analog and digital supplies, respectively.
+When and if time permits, a final schematic will be produced to show the as-built hardware in its entirety.
+== BT8040N versus BXA4230K ==
+While these parts are pin-for-pin compatible, and seemingly listed as drop-in replacements, there is no doubt that the BXA4230K has a distinctly different sound than the BT8040N.  The tone progression interval, pacing and decay (with external circuits) are very similar.  The BX4230K, however, has lower fundamental tones, and additional harmonics and/or sustained tones.  I don't have captured audio samples - but I can say that if you've heard the PA-9100RC chime, you won't be satisfied with the BT8040N.  I wasn't.
+== Future ==
+The LCD display was primarily added to provide a visual level cue to the announcer.  The PA microphone is very sensitive to proximity and volume; too far away or too quiet and the PA announcement isn't sufficiently audible.  This seemed like a larger issue in 2020; as of 2021, though, the staff is doing quite well making clear announcements.  The development semi-extensive code to add a graphical Vu meter (with louder/software cues) to the LCD seems unnecessary at this time.
+The hardware is mostly ready for feeding the microphone signal into a low-passed ADC input for microphone monitoring when and if this feature is ever to be developed.

PA Chime Generator: Difference between revisions

Matt Parnell (talk | contribs)