LC40

Graphic Equalizer

While this equalizer is very unique, it is similar in filter topology to the graphic EQ's of the early 1970's. IC gyrators are employed and the circuit has an inherently Proportional Q.

Besides the physical appearance, the only difference between the LC25 and the LC40 are the frequencies.

The biggest difference between the LC40 and most other graphic equalizers are the stepped controls. Exact recall is a must in the modern day of recording and mixing. Other similar equalizers may have fine resolution from 0dB to +/-4dB, but from that point to max cut/boost things get out of hand quickly and near impossible to repeat. By going stepped, I had the opportunity to add a -15dB cut which is a fantastic bonus!

The audio path of the LC40 is extremely unique. I have chosen to use the coveted EA2622 mic input transformer as the receiver. The EA2622 is essentially setup in the same way as line mode on the VP28. The EA2622 is buffered from the remaining circuitry by a DTO5 discrete opamp. Five bands of gyrators "hang" between each of the swinging inputs of a dual LME49720 opamp. The output stage is a socketed 2520 style discrete opamp followed by a 2503 style output transformer wired 1:3.

A 2-position toggle operates a hard-wire relay bypass. This relay bypass has a shunt jumper connected to the Pin-6 DC bus so any adjacent LC25's or LC40's can be bypassed by activating the toggle on only one unit. BYP = bypass and ACT = active.

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