10-07-2013 Post does not mapped to Knowledge Tree skushino Seattle, WA Posts 93 Joined on 07-07-2004 Post #: 21 Post ID: 20136 Reply to: 4076 High-Pass Filter Help fiogf49gjkf0d Romy, would you explain / help me better understand how you implemented the HP filter in Melquiades? The schematic shows a series cap after the first tube stage (C3 and C4 in the schematic).  I think these are the first-order HP filters, correct? Question - what is the procedure used to determine the cap values? My basic understanding is that the knee of the filter is a function of the cap value and input impedance of the following stage.  I'm getting lost on determining the input impedance of the following stage.  I have a hunch I'm overly complicating things. My goal is to HP my ML2s around 60 Hz. Thanks.

10-07-2013 Post does not mapped to Knowledge Tree Romy the Cat Boston, MA Posts 10,155 Joined on 05-28-2004 Post #: 22 Post ID: 20137 Reply to: 20136 Very easy. fiogf49gjkf0d HP means high-passing, right? In Melquiades I do it by changing the coupling cap between the stages. You can do the same in ML2. To unsolder the cap from ML2 is pain in ass but you might juts clip one of the lead and solder another smaller cap next to the big one. To know the cap value you need to know the input impedance of the ML2 second stage and then juts run a first older filter against the fixed impedance. I think ML2 has fix bias and it have to be very easy to find out what would it be. "I wish I could score everything for horns." - Richard Wagner. "Our writing equipment takes part in the forming of our thoughts." - Friedrich Nietzsche