<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body><div><div style="font-family: Calibri,sans-serif; font-size: 11pt;">Everybody loves the 303..<br><br>Good post..<br><br>Paul<br>London<br>www.punkdisco.co.uk</div></div><div dir="ltr"><hr><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">From: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;"><a href="mailto:kmkennedy@gmail.com">Kylee Kennedy</a></span><br><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">Sent: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;">21/10/2015 01:21</span><br><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">To: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;"><a href="mailto:rburnett@richieburnett.co.uk">Richie Burnett</a></span><br><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">Cc: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;"><a href="mailto:Synth-diy@dropmix.xs4all.nl">synth-diy</a></span><br><span style="font-family: Calibri,sans-serif; font-size: 11pt; font-weight: bold;">Subject: </span><span style="font-family: Calibri,sans-serif; font-size: 11pt;">Re: [sdiy] Roland TB-303 filter responses graphed</span><br><br></div>Love the 303! Thanks for posting the info.<div>Kylee<br><br>On Tuesday, October 20, 2015, Richie Burnett <<a href="mailto:rburnett@richieburnett.co.uk">rburnett@richieburnett.co.uk</a>> wrote:<br><blockquote class="gmail_quote" style="margin: 0px 0px 0px 0.8ex; padding-left: 1ex; border-left-color: rgb(204, 204, 204); border-left-width: 1px; border-left-style: solid;">For anyone interested, this graph shows the response of a real TB-303 filter set at full resonance for a range of cutoff frequencies:<br>
<br>
<a href="http://www.richieburnett.co.uk/temp/303vcf.gif" target="_blank">http://www.richieburnett.co.uk/temp/303vcf.gif</a><br>
<br>
There are lots of theoretical responses, mathematical transfer functions, and simulation results on the net, but i've never seen any real measured responses before.<br>
<br>
These responses were generated at the same drive level that the sawtooth VCO drives the filter in the TB-303. (The shape changes if the drive level is changed.)<br>
<br>
Notice how the resonance is much stronger at higher frequencies, and runs out of steam at low cutoff frequencies. The little peaks and dips to the right of the normal resonant peaks, are due to harmonic distortion in the filter and the VCA that follows it in the TB-303. Also notice how the actual resonant peak of the TB-303 has a steeper slope on the right side, than the left side when the Q is high. This "lop-sided" resonance is another artefact of the filter's non-linearity and occurs naturally in mechanical resonators as "hardening".<br>
<br>
<a href="http://www.zainea.com/lowresonances.htm" target="_blank">http://www.zainea.com/lowresonances.htm</a><br>
<br>
Hopefully this is interesting to some TB-303 scrutinisers.<br>
<br>
-Richie, <br>
_______________________________________________<br>
Synth-diy mailing list<br>
<a>Synth-diy@dropmix.xs4all.nl</a><br>
<a href="http://dropmix.xs4all.nl/mailman/listinfo/synth-diy" target="_blank">http://dropmix.xs4all.nl/mailman/listinfo/synth-diy</a><br>
</blockquote></div>
</body></html>