This can give you a nice fat bass but without a muddy distortion because it is located after the gain/overdrive stage.
The post-overdrive EQ shapes the sound after it has passed through the overdrive stage. This is useful if your organ has a weak bass response and you want more of a bass growl and grind or if you want more distortion from the organ treble frequencies. The pre-overdrive EQ affects the tonality of the signal going into the 12AX7 valve.
However I have disregarded the low gain cathode follower circuitry that Bob Schleicher's circuit uses and I have simply wired the EQ tone stack before the input grid and after the master volume control of the EQ/overdrive circuit.īoth stages of the 12AX7 valve are wired as simple cascaded gain stages. The passive bass and treble EQ's are Baxandall type EQ's and I have simply copied the bass and treble tone stack that Bob Schleicher displays on the schematics section of his website (see ), This circuit is reasonably simple in operation in that it uses one 12AX7 valve and a passive ’pre overdrive’ bass and treble tone stack EQ before the gain/overdrive stage and also a passive ‘post overdrive’ bass and treble tone stack EQ after the overdrive stage.īoth EQ's can be independently activated or bypassed with a 2-pole / 2-position ( DPDT ) switch. Switching off the passive pre overdrive EQ The quality of the overdrive tone is very good and it does sound similar to an overdriven Leslie 122 or a Leslie147 etc valve amplifier depending on the settings of the EQ controls. This circuit connects between the wiper of the preamplifier Tone Control potentiometer and the input grid of the output valve which is a 6SN7 on the AO10 preamp and a 12BH7 in the AO28 preamp, and it uses a 12AX7 valve to create the overdrive effect. I think that it might also be adaptable for the earlier era console organs such as the Model a, B, BC, BV, CV, D, E etc but I have not tried this out either. It might also work in the M, M2, M3, M100 series, L100 series, Porta B etc organs but I have not tried this out. This 12AX7 based EQ / overdrive circuit is designed for the Hammond tone wheel console organs that have valve preamplifiers such as the B2, C2, RT2, B3, C3, RT3, A100 series, D150 series etc. Kon's 12AX7 based EQ & Overdrive circuit for Hammond Organs
0 kommentar(er)
