I leave the technical challenges of designing filters to people who, ulike me, have some idea of what they are doing. But why have a bandpass -especially one covering a large frequency range - covering a range up to 20khz? And for guitar? Seems to me that lot of that territory (in the presence range for guitar and beyond) would be better handled with a highpass; keep your parametric bandpass filter to a lower and more restricted range, and it will be both more effective and easier to execute. Or is this for some other application? Most grateful for your time, jatalahd! And I am sorry for this delay.If I rightly computed this with your above equations, for your proposed circuit I get fmax = 2340Hz and fmin = 97Hz.
BYOC Fuzz Face. BYOC-Reverb 2. BYOC-Mouse (Rat clone) BYOC-C2 Chorus. BYOC-Parametric EQ. BYOC-Bass Chorus. Boss-RC30 Loop Station. Moog Analog Phaser Studio Drum Set: 1970s Rogers R360 3 Piece Kit (12, 16 and 20 inch shells) 1960s Gretsch 22x14 bass drum. 1960s Rogers 13' Tom. SNARES: Ludwig Hammered Black Beauty Snare (14x6) Ludwig Hammered. It depends on what you want to do. The Parametric Eq that me, Chub and Mark day used served two purposes. We used the Furman Pq3 which is a boost and EQ in one. We used to use them before the amp as a boost/tone shaper. If you want to shape your tone and boost your amp Id use it before your amp.
Do you confirm? Did you not put R10 and R16 (from BYOC circuit)? Are these 220kΩ?With these equations for BYOC circuit I now get that fmin = 33Hz.but still fmax = 312Hz instead 333Hz (as they claim).What are the equations for that variable Q? How should your above equation include RpQ to get Qmin and Qmax?And for said 'stability' should C4, C2, C3, R7 be kept? Or where should those 'here and there' resistors certainly be?Do you know how to adapt those boost/cut equations for VR1 of BYOC circuit?Commercially is this so laborious?
Is not all this solved already? Are these equations such trade secret?If I am to ignore all these equations, transcribe this BYOC circuit to SPICE or other (EasyEDA, which could then convert this to PCB?) and change resistors here and there till I attain my needs, how shall I do this?
What resistors must I change (hence my quest for these equations.)? In your circuit resistors are 'all' of 10kΩ, BYOC has many of 5.1kΩ and some of 1.6kΩ (that affecting Q included). Should all these of equal value be kept of equal value?
Damien Douxchamps already notes R15=R17, C5=C6, R10=R16 (adapted to BYOC circuit, which does not have equivalent resistors to Damien's R13 and R15), but what of others?(Pardon my ignorance.). I cannot help with EasyEDA. I would suggest taking BYOC circuit as base point. If you decide to change 5k1 resistor, change all 5k1 resistors to same value (whatever it is). You need to note that R9/R8 sets the gain for the filter, so you need to adjust that to your needs or keep it the same ratio 3:1. If you change R10, you set also R16 to same value. If you change VR3b, change also VR3a to same value, note that in your build you need a dual-ganged pot to turn VR3a/b simultaneously.Hopefully all is clear now.
Much much obliged, jatalahd, for your time and help. And may this help others.I want this EQ to have around:Band one: 50Hz.
By significant I mean that the Q seems to change rapidly only at small resistance values and it might be difficult to tune with 10k pot if you want for example Q=11 or Q=12 when Qmax = 15 at 220 and Q = 10 with 350. Also When handling small resistances, then there might be some other 'hidden small resistance' in the circuit, for example op-amp output impedance that sum up with the other small resistances, or the pot might not turn to 0, it might have some remainder resistance. It is sometimes hard to get exactly the value you want.
This is why I don't like to use very small resistors in a circuit. Moving on with these values. Are these resistors and capacitors apt?
What should be my criterion for Watts, Voltage and tolerance?8.2kΩ270Ω4.7kΩ2.7κΩ220Ω3.9kΩ10nF1nFFor frequency I want to use guitar potentiometers separated from board. Are these apt? Should I use linear for smooth response?For Q and Boost/Cut I want to use trimpotentiometers fixed on board. Are these apt? As more turns they allow, so more smoothness I get? Particularly with such high Q?Or would these of 1 turn be enough?
For the resistors, 0.25W will be ok, but I mostly use 0.5W or 0.6W just because there's not really much difference in price. Metal film for lower noise.For voltage ratings - well, what supply have you got?
Use the next voltage rating up from that. For most stuff, 50V is fine for caps, and for 9V-powered pedals 25V rated caps are fine too.One thing to note about State-variable filters is that they won't achieve high resonance without good matching between the stages (or you'll need a lot more gain to compensate, anyway).
So I wouldn't recommend the +/-20% ceramic caps. The +/-5% C0G caps are much better, but filter applications like this are one place where tighter tolerances.do. actually make a difference. I've even used 1% caps (rare, but there are some) for synthesiser filters, since the filter is such a key part of the sound for a synth. This part on LTSpiceProduces thisWhich by itself seems to attain my needs.without those parts at input (R1-R4, C1, IC1a) and output (R45-49, C17-18).I even preferred to increase C4 from 0.1μF to 10μF, which almost keeps 0dB (-0.49dB) just before first band (with 0.1μF it decreased to -1.78dB just before first band).But little difference C4 and C9 make.
And truly without C2-4 and C7-9Perfect symmetry is attained. What to do about these capacitors?What do you, experts, opine? Will this work? What must it still have for stability and input/output impedance?