![]() Nerd shit: small polystyrene caps for the high freqs, yellow polycarbonate phillips caps and notice the giant silver Russian 10 uf film caps! no electrolytics in my filter! Measuring all the caps and re-calculating frequencies Most vintage capacitors have tolerance values of 5%, 10% 20% and i was using tons of vintage stuff from my stash, so i needed measure, especialy for a passive eq. If you don’t measure parts, or limit yourself to using an available brand of expensive -1% parts, the frequencies will vary from the calculated values and the spacing of the freqs can be weird, too far or bunched together. This is an advantage of home made electronics, because of parts tolerance it would be very expensive for a manufacturer to exactly match all units. I matched all the inductors values and cap to less than 1% and got all the frequencies i wanted spot on. It’s a long and tedious process but it’s way easier than it seems once you get the hang of it. Pretty much the same process for all the other eq’s. I had a 24 positions switch for the high band, compared to 5 frequencies on the original, so, alot more math, measuring etc. re-calculate freqs with the caps and inductors real world values.Measure shit loads of capacitors and paralleling them to get all the calculated values right.re-calculate all the frequencies with the tolerance of my inductor.measure the inductor for exact inductance values.Wind a multi-tap inductor with all the taps i needed.Calculated for all the in-between and extra frequencies i wanted to add.I re-calculated all the original Meq eq frequencies, inductance and capacitance.The way i did it to get all the frequencies right : I studied the circuit to understand the filter topology and then found some online calculators to help with the math. I am goin with the “solid state” version using Api 2520 discrete op-amp for make up-gain, so i won’t need the expensive interstage transformer as needed for the original tube version. The Filter circuit is a bit more complex than the EQP, Using 3 multi-tap inductors. So i started by studying the schematic of the filter circuit: (credit to Gyraf, Thanks man!) The first tube version has a make-up gain amp a little different than the EQP but the solid-state version is very similar, this is the one i wanted to clone. It’s a “passive” eq followed by make-up gain. It is basicaly a mid-range eq with low-mid boost, mid-cut and high mid boost. The MEQ-5 is a little less famous than the EQP-1a and probably a little rarer but selling for a little less than the EQP because it is less sought after. Here’s a pic of an original, tube version. See Part.1 for the intro and the eqp-1a cloneĪight, next up in my Pultec eq’s cloning saga, the MEQ-5 mid-range equaliser. Trio de Pultec from scratch Pt.2 – The MEQ-5 ![]()
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