<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">On Mar 11, 2006, at 11:19 AM, <<A href="mailto:scottnoanh@peoplepc.com"><FONT class="Apple-style-span" color="#2300EE">scottnoanh@peoplepc.com</FONT></A>> wrote:</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><FONT class="Apple-style-span" color="#2100DD">The higher value of capacitance always brought a certain amount of pitch</FONT></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><FONT class="Apple-style-span" color="#2100DD">bend on the lower end of the sweep.</FONT><FONT class="Apple-style-span" color="#2100DD"> </FONT><FONT class="Apple-style-span" color="#2100DD">I started wondering if that was</FONT></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><FONT class="Apple-style-span" color="#2100DD">because, as the VTL5C3/2 goes higher in resistance, the tolerance of</FONT></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><FONT class="Apple-style-span" color="#2100DD">resistance begins to vary more greatly from device to device.</FONT><FONT class="Apple-style-span" color="#2100DD"> </FONT><FONT class="Apple-style-span" color="#2100DD">Taking that</FONT></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><FONT class="Apple-style-span" color="#2100DD">into account, along with a suggestion from a list member, I lowered the LDR</FONT></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><FONT class="Apple-style-span" color="#2100DD">parallel resistance from 1.5M to 1M, and that seems to have improved things</FONT></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><FONT class="Apple-style-span" color="#2100DD">on the lower end quite a bit.</FONT></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">With both phasers and flangers, there is always more apparent pitch bend at the low end of the modulation. This becomes more apparent at faster modulation rates. Adding lots of juicy regeneration/feedback seems to make this worse, unfortunately. You can always minimize this unwanted pitch shifting by reducing the overall modulation depth, but where's the fun in that? We all love deeeeeeep phasing and flanging modulation.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">There are two ways that I can think of to keep the modulation fat and deep, but reduce the unwanted pitch bending:</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">1. Use an LFO that changes its frequency (and hence, its shape) as it goes through its cycle. Craig Anderton famously did this on his PAIA Hyperflange design. He used a CEM3340 VCO for his LFO, and he fed a little bit of the LFO's triangle wave output back into the 3340's modulation CV input, so that the LFO would speed up during the triangles peak, then slow down at the low part of its cycle. He had a special name for this type of LFO -- a "hyper-triangle", or something like that. The end result was that you could use much greater modulation depths on the flanger, because the relative LFO speeds were better matched for the high and low frequency ranges of the flanger's comb-filtering. Another way of describing this is that the modulation intentionally moves more slowly while it is working on the frequency range that provides the most dramatic "action" -- which is very useful with a deep, resonant flange effect, especially at very sloooooooow LFO rates. I'm sure that this method would work just as well with a phaser. One possible down side to this method is that the up and down modulation sound will have a kind of lop-sided quality to it -- this may or may not sound good at certain LFO rates.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">2. Create an LFO scheme that would allow your modulation depth to change as the LFO goes up and down. That could be done by using the raw triangle LFO itself to modulate a VCA/attenuator (such as a LM3080). Run the LFO's output through the VCA, which would, in turn, output a triangle wave whose amplitude varies in direct proportion to its relative phase (that is, higher amplitude when the wave is peaking, and lower amplitude when the wave is low). Use this self-amplitude-modulated LFO to modulate your phaser. This should also help minimize the pitch-shifting, still allowing fairly deep apparent modulation depths. The effect would be similar to Anderton's idea, but with a more triangular overall modulation shape, which might sound less lop-sided at certain LFO rates (particularly at faster rates).</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">I have tried neither of these methods using actual LFO's, but I have simulated their effects by manually adjusting LFO speed and depth while the LFO cycles, and both methods seem to work pretty well. My apologies if I have described the actual electronic methods used not so accurately -- please refer to the <A href="http://ampage.org/hammer/files/Hyperflange.PDF"><FONT class="Apple-style-span" color="#2300EE">Craig Anderton Hyperflange schematic</FONT></A> for better details.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Michael B.</DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR></DIV><DIV style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font: normal normal normal 12px/normal Helvetica; min-height: 14px; "><BR class="khtml-block-placeholder"></DIV></BODY></HTML>