Pickup coils from multi-layer PC boards

[Hugh Evans]

Yeah, it's unfortunate that more descriptive units are rarely used. At the same time, one can only imagine the confusion proper Bode plots could create despite providing a true representation of how the system will function. I've had good luck describing the state variable filters in my design as a circuit that shapes a pickup's response in the same manner as changing the number of windings, strength of the magnet, and values of pots and capacitors. That makes much more sense to most players than saying "it allows for independent control of gain, resonant frequency, and Q."

[bbsailor]

Even with without cable loads it makes sense to wind for lower impedance, and I plan to start with something on the order of 1K DC as that should send the resonant peak well beyond the audible range for humans and provide a flat response through the useful range. This should allow for a good match to the pre-amp/filter circuit without using transformers. I want the end user to choose what response curves they want to use rather than forcing them to start with some arbitrary traditional tone first. Why stop with what is already available when there are some wonderful tones available in the spectrum most players have never been able to experience?

Hugh,

Winding to 1K assumes you are using the same gauge wire as was typically used on high-Z pickups normally AWG 42. This keeps the winds very close to the core magnetic field where the output is more linear with each additional turn adding about the same output compared to fatter coils where the outer winds only add between .5 to .6 the voltage of the inner turns. The impedance scales as the square of the turns ratios, So if you normally have a pickup with 8K DCR of AWG 42 then 1K of AWG 42 is about 1/8 the number of turns but the impedance ratio is 1/64 so the pot values should be 64 times lower to reflect similar loading on the 1K ohm coil. The capacitance values scale the same also but increase by 64X to have the same effect. The ear is the final test. 500K pots scale to 500/64 or 7.8K (not a standard value) but 10K should be close enough. With these 1K pickups you may want to try a little thicker wire like AWG 40 or 38 to listen to effect on the lower frequency range. I would experiment with a tap at 750 ohms and 1 K ohm and listen for the best balance. Also, try one pickup coil using Litz wire with strands in the AWG 42 to 44 range to see if you can hear any additional high frequency details. I have some Litz that is 40/44 or 40 strands of AWG 44 that is .019" diameter and equivalent to AWG 28. If I wound a very tight humbucker bobbin, I might get almost 150 turns on the coil or about 5 ohms. Two of these bobbins in series would match a Shure mike matching transformer A95 series very well but the output would only be equal to about 3600 turns of a pickup. 150 + 150 X 12 (TR of transformer). As it has lower turns it will have a better S/N ratio and could use a little extra amp gain without picking up too much noise. Mount the A95 transformer at the amp to get the full benefit of this pickup.

When using your 1K ohm pickups you can always use the 10K to 20K line input on a mic mixer then feed the mixer output into your guitar amp. If the mixer has a mid frequency control, you can dial up the sound you like and adjust the gain of the mid boost to sort or match your favorite high-z pickups styles.

Post your results so we can all learn more about stepping into the lower Z pickup area.

Joseph Rogowski

[Mike Sulzer]

Yeah, it's unfortunate that more descriptive units are rarely used. At the same time, one can only imagine the confusion proper Bode plots could create despite providing a true representation of how the system will function. I've had good luck describing the state variable filters in my design as a circuit that shapes a pickup's response in the same manner as changing the number of windings, strength of the magnet, and values of pots and capacitors. That makes much more sense to most players than saying "it allows for independent control of gain, resonant frequency, and Q."

One way is to describe the impedance by the value of the pots used in the guitar. So the standard humbucker control is 500K. For example, reduce this to 50K, and use about sqrt(10) number of turns, using wire with about 3 times the cross section of #42. (Or wind on three windings of #42, each with 1/3 the number of turns of the original and put them in parallel.) For the original resonant frequency, load the circuit with 9 times the cable capacitance, and now the sensitivity to change in cable capacitance is quite small. (The Q will be close to the original because of the change in the wire.) If you want flat response, leave out the capacitance, and experiment with some additional resistive load. For all but the most demanding applications, there is still plenty of signal to give good SNR with a tube amp, and you can always use a low noise SS preamp with a low gain for the best SNR.

[David Schwab]

Without any other changes, these are tonally on the bright side, but players over the decades dealt with this primarily by using extremely long cables rather than RC networks to darken their tone. This practice is well documented for Hendrix, Clapton, and SRV to name a few. Later, the "hot" pickups were introduced to create darker tones while sending out a stronger signal to help push input tubes into overdrive. However, this came at the cost of flexibility: a bright pickup can be manipulated to take on a darker character, but going in the opposite direction is questionable at best. Musicians and pickup makers, in my opinion, should have started to re-evaluate their approach by sometime in the 90s.

Actually players used a bright tone back then. And then they used treble boosters too. The long cables were just because they wanted long cables. There was no wireless back then. Same with coiled cords. We used them because they were available and looked cool. The fact that they rolled off some high end wasn't even thought about for the most part. You can see that because just about everyone used one, including me, and I liked a bright sound. So not everyone used them because they sounded a certain way. In fact I'd go so far as to say that they fell out of favor because of their tone. This was also about the time that people were taking the covers off of humbuckers to brighten them up.

The over wound pickups were to over drive the amps, since there weren't many distortion pedals used back then. The fact that over wound pickups are darker (which is debatable, since the Dimarzio Super Distortion and Lawrence L-500 is pretty bright) is just a side affect which kind of worked to the advantage of an over driven tone.

This whole dark humbucker thing is a more recent fad IMO. Sure, they are fuller sounding than single coils, but not by a whole lot.

But I agree with the rest of your post. I actually used to enjoy the EMG guitar pickups I used at one point. They got all the usual tones, and you could turn down your volume without the usual mud. What I don't like about them is the lack of coil switching, etc.

Personally I like to make loud, but bright, humbuckers for guitar. But I also like the alnico II type of tone for neck pickups, and some of my bright pickups (or they get too edgy).