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Started by Loudthud, April 17, 2015, 05:54:14 PM
Quote from: Loudthud on February 18, 2017, 04:37:26 PMAs a general guideline I would say you want a JFET with an Idss roughly between 2mA and 10mA. The 2N3819 should work fine. If Idss is higher, the pot becomes very touchy, you might need a 10 turn trim pot. This all depends on the resistances in the feedback network. Lower impedances work with higher Idss parts. Just keep the ratio of the resistors the same.
Quote from: tarahall on March 11, 2017, 09:28:38 PMAre the gate voltages for the 2n5462 (+3.3) & mpf102 (-2. the optimum for your circuit or are they just indicative of the voltages you needed to set for the specific devices you used? I'm curious as we all know how varied the tolerances and ratings of JFETs of the same type can be.
Quote from: tarahall on March 11, 2017, 09:28:38 PMI have tried adding your JFET idea to Rod Elliots's Project 27 preamp (mentioned elsewhere on these forums) and the results are certainly encouraging although I had to adjust the gain of the first 2 OPAmp stages upward. It made the preamp brighter with less mid-range wool and a crispness and bite one expects from a typical Fender front-end.
Quote from: Loudthud on March 12, 2017, 03:18:02 AMIIRC Rod's preamp used a Baxandall tone control network. The Fender type network will certainly sound different.
Quote from: Ironsinthefire on July 21, 2017, 05:01:55 PMLoudthud,Given the difficulty of finding appropriate P-channel FETs nowadays
Quote from: Ironsinthefire on July 21, 2017, 05:01:55 PMGiven the difficulty of finding appropriate P-channel FETs nowadays, would preceding the first stage with an inverting, unity gain buffer and switching the FET to an N-channel work?