Fully Parametric Tube EQ (with gyrators)

Posted on Feb 6, 2014

A fully parametric tube EQ and my best bet seems to be `merging` these two schematics into one so that i can get a tube-based gyrator section (with adjustable Q, Freq and Gain) and use ICs for the input and follower stages (going to use this on a home-built mixer so reducing number of tubes is the reason). I did this schematic in hopes of understanding things better. I basically

Fully Parametric Tube EQ (with gyrators)
Click here to download the full size of the above Circuit.

just replaced the transistor with the tube. I tried simulating it in a Spice program but didn`t work for me - i`ve never tried simulation before so probably a PBCAT issue (problem between chair and terminal). I am totally new to `designing` any circuits, so this schematic may have some laughable elements, but hey, gotta start somewhere. By the way - i hear that the Electro Harmonix Tube EQ pedal uses a "detuned Twin-T" type format, tho i don`t what parts of theirs are tube or IC (nor what they mean by `detuned`). my one question is about boost-cut. on the schem there`s a lone. 5meg pot connected to the grid of V2 that is unmarked (to the upper-left of V2). is this boost/cut for the bass section and secondly, where does a boost-cut pot go for the treble stage (i don`t see one) Since that`s a 2-channel, the treble channel need not be made in the first go-round, and the cathodyne could be made from the first triode and the EQ powered from the second, in the same envelope. That gives 1 mini tube socket per channel. When you mean the feedback loop of a cathodyne-do you mean a cathode follower-but I didnt think a cathode follower had a feedback loop am I being dumb-am I missing something I don`t have the ability to frame it into the original circuit, but a cathodyne is a phase inverter that pulls a non-inverted signal from the cathode, like a cathode follower, and an inverted signal from the anode, like a standard gain stage,...

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