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Homero - Thank you for the updates!?? 1. Is the charge amp being accomplished through the Op Amps??? 2. Is it possible to use a Jfet with a built in diode for the triode section?? Maybe something like the K596 Jfet? Jerry - Thank you for the input.? My train of thought was that a Jfet Op Amps may be used to replace the discrete Jfet in the triode mode.? My understanding is that Jfet Op Amps essentially have multiple Jfets?structures on one IC.? Is it not possible to use them in this way?? ? Thanks in advance!??
On Friday, May 6, 2022, 08:50:19 AM PDT, Homero Leal <homero.leal@...> wrote:
Thank you Jerry Lee and Henry, @Jerry Lee Marcel?I reduced the value of C8 to 1uf. Also there was an error on the C15 value, it should be 1000p instead of 0.1uf. @William Spragens?The additional RC filter after VR was added to a new PCB design and sent to PCBWay. Thank you! Here is version 1.1: Also a quick update, replacing 10V zener with two 5.1V zeners in series, seems to fix the problem with the LF noise, but VCC is reduced from 9.4V to 8.5V aprox. This should not be a problem, since AFAIK...? JFET drain voltage is not critical to get it working in triode mode. Waiting for the new PCB version with the additional RC filter. Will let you know how it?goes in a?few days. Kind regards! HL An additional RC filter would work, or simply adding a resistor between the BC549 and C14, and increasing C14 to push the RC time constant below audibility. The op-amps have good power supply noise rejection, but the FET has none. It needs pure DC. |
