I agree you can get the original volume and gain back on the amp if needed. So you wire the coils in parallel (which gives a good low impedance output), and then use R’s and C’s to tune the new brighter response, back down to the same tone as for series wiring, or other tonalities in between and beyond? A side effect is apparently less sensitivity to cable capacitance. OK, I think I get what you are doing now. I'll add some further comments in a couple of days (curry night tomorrow!) You can see what's going on, but it's time for bed. R_tone=1k, R_Vol1=0.01k, R_Vol2=550k, C_res=1.5nF, R_Q=6.8kįull Volume/Full Tone - with higher main resonance I changed R_Q=6.8k on all the sims below because I thought the Q was to high with R_Q=0.01kįull Volume: R_Vol1=0.01k, R_Vol2=550k, C_res=1.5nF, R_Q=6.8k In each of the simulations below I have given the component values that were changed.Īs per original netlist posted earlier with R_Q=0.01k I would really appreciate any comments and a sanity check!Īpologies first, MacSpice doesn't seem to do multiple plots, if anyone knows how to, please let me know. Setting R_Q to zero yields a Q of 13db, which is aggressive. Choosing a value for R_Q is just a guess. I have only performed model analysis on MacSpice, so there may be some variations in practice Many of the circuit values have been estimated, since manufacturers rarely provide characterisation data for pickups. However, I believe this can be compensated by turning up the pre-amp without introducing significant amp noise. Connecting the coils in series results reduced output compared to the parallel configuration, but I do not believe it is halved, I believe it is dependent on power transfer characteristics (a bit too complex for me to work out). When the tone control is close to zero, a new resonance is formed from L_hb and (C_res + C_hb + C_tone). As the tone control pot is reduced, the resonance of L_hb and C_tone attenuates the resonance of L_hb and (C_res + C_hb). C_tone is increased by a factor of four, since L_hb is reduced by a factor of four. R_mix also provides further isolation of C_cable from L_hb which reduces its influence on the prime resonant frequency. Since R_mix feeds into the R_amp (~ 1M), the signal loss is relatively small (< 1db). R_mix, provides some mixing function when selecting both neck and bridge pickups. Since series wiring reduces the pickup resistance, the Q factor is increased, R_Q is used to reduce the Q factor. This means the resonant frequency is quite stable over all vol pot levels. As the volume pot is reduced the resonance of L_hb and C_cable is attenuated by the resonance characteristic of L_hb and C_hb+C_res. At Vol pot = 10, L_hb and (C_hb +C_res) define the prime resonant frequency (see R_mix info). * plot the magnitude of the voltage at node 7 vs frequency * dispose of any 'save' statements from previous runs *Load Capacitor and Resistor - to define resonant freq. Coli capacitance is multiplied by four - in practice the multiplier is 2~3 times the series resistance is roughly divided by four the inductance is roughly divided by four LCR combinations with a low resonant frequency attenuate higher frequency resonance of other LCR combinations.Ģ) HB Parallel Coils (compared to series coils) When R is high there is little resonance (low Q). Each mode of resonance is defined by a particular LCR combination which defines the resonant frequency and the Q factor. With multiple capacitors there are multiple modes of resonance. My approach is to think of the humbucker inductance as making a resonant circuit with the all the surrounding components, up to and including the cable and amp impedance. A second characteristic sound created when tone pot set to zero, which is user definable.įirst some background ideas triggered by the fine work of JohnH, thread ref: A better treble bleed circuit. Some provision for centre position volume mixing is available The characteristic sound is preserved at nearly all vol pot levels - treble bleed is not needed. L_hb, C_res and R_Q act like a an equaliser giving good control of the characteristic sound - experiment with C_res values first, then R_Q values. Simplifies setting the characteristic guitar sound. I am planning to use these ideas on my Vintage V100 and would appreciate any comments/criticism/improvements from the forum. I am submitting some ideas about the circuit design for a humbucker coils configured in parallel.
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