user67474: I am trying to get a nice sounding varying PWM to DAC, and intend to use a Sallen Key as part of an active low pass filter.
I set the Fast PWM at a max of 255 (WGM1[0-3] = 5) and set/clear OC1A upon comparing with OCR1A (1<< COM1A1)
I also update the value of OCR1A in 64 distinct steps, changing those steps around 15'000 times a second to create a specific sinusoidal shape.
As the chip works at 16 Mega Hertz, does this mean that one cycle of PWM is 16'000'000/256= 62.5 Kilo Hertz? If not, what is its resolution
Thank you!

user67474: With the help of the comments, I decided to use variable PWM max values to match absolutely with the frequency. This resulted in a crispier sound that actually doesn't need the Sallen Key anymore.
For example, a low C natural, or 261.6Hz, updated 32 times for 8 full cycles of PWM give us, for a 16MHz chip, an period and amplitude of 238.
This means that having a prescaler of 8 (CS01), a period (OCR0A) AND a max potential duty cycle (ICR1) of 238, and going through 32 iterations of the sound sought for, I got the sound that I wanted and none of the wave groove that comes with a pulse duty cycle cut short.
Sure, it means less granularity when it comes to a Bb with a max duty cycle of 133, however it worked for me.

67474: <p>I am trying to get a nice sounding varying PWM to DAC, and intend to use a <a href="http://sim.okawa-denshi.jp/en/OPstool.php" rel="nofollow noreferrer">Sallen Key</a> as part of an active low pass filter.</p>
<p>I set the Fast PWM at a max of 255 (<a href="http://sculland.com/ATmega168/Interrupts-And-Timers/16-Bit-Timer-Setup/" rel="nofollow noreferrer">WGM1[0-3] = 5</a>) and set/clear OC1A upon comparing with OCR1A <code>(1&lt;&lt; COM1A1)</code></p>
<p>I also update the value of OCR1A in 64 distinct steps, changing those steps around 15'000 times a second to create a specific sinusoidal shape.</p>
<p>As the chip works at 16 Mega Hertz, does this mean that one cycle of PWM is <code>16'000'000/256=</code> 62.5 Kilo Hertz? If not, what is its resolution</p>
<p>Thank you!</p>
 67474: <p>With the help of the comments, I decided to use variable PWM max values to match absolutely with the frequency. This resulted in a crispier sound that <em>actually doesn't need the Sallen Key anymore</em>.</p>
<p>For example, a low C natural, or <code>261.6Hz</code>, updated <code>32</code> times for <code>8</code> full cycles of PWM give us, for a 16MHz chip, an period and amplitude of <code>238</code>.</p>
<p>This means that having a prescaler of <code>8</code> (<code>CS01</code>), a period (<code>OCR0A</code>) AND a max potential duty cycle (<code>ICR1</code>) of <code>238</code>, and going through 32 iterations of the sound sought for, I got the sound that I wanted and none of the wave groove that comes with a pulse duty cycle cut short.</p>
<p>Sure, it means less granularity when it comes to a Bb with a max duty cycle of 133, however it worked for me.</p>
