|
Post by antigua on Oct 26, 2020 23:18:54 GMT -5
One major difference between the P90 and the typical Strat pickup is that eddy currents make the P90 inductance and resistance vary considerably with frequency in the region around 3kHz but the Strat pickup not so much.
That makes sense, since the real resistive load is independent of frequency, and I can see how that would be useful. Are the pickup components approximating the frequency dependent effects of eddy currents? I've had P-90 like pickups in Strats, such as the Seymour Duncan "StraBro 90", and I've always felt it was thick and dark of a sound, for a Strat.
|
|
|
Post by aquin43 on Oct 27, 2020 4:49:14 GMT -5
One major difference between the P90 and the typical Strat pickup is that eddy currents make the P90 inductance and resistance vary considerably with frequency in the region around 3kHz but the Strat pickup not so much. That makes sense, since the real resistive load is independent of frequency, and I can see how that would be useful. Are the pickup components approximating the frequency dependent effects of eddy currents? I've had P-90 like pickups in Strats, such as the Seymour Duncan "StraBro 90", and I've always felt it was thick and dark of a sound, for a Strat. Yes, the models match the pickup impedances by including the eddy current coupling to the coil: I tried this mod and got results that were close to the modelled ones. The way the bandwidth is retained as the volume is turned down is quite noticeable.
|
|
papasteack
Rookie Solder Flinger
Posts: 5
Likes: 1
|
Post by papasteack on Feb 1, 2021 10:48:51 GMT -5
Hi, I really like all this stuff, maybe a bit too much, so if i'm wrong, i'll be really happy to discuss, and sorry for my poor english Fluence is a active pickup, but not the same way as emg or seymour's. From what i've seen, Fluence take the whole humbucker output, and eq it (i don't manage to find again the link of the patent). Emg and seymour uses differential amplifiers typology : conventional differential op amp, or with current source differential amplifier bjt pair + op amp. Each coil of humbucker has one leg to ground. So that loading isn't anymore linked between coil. The resultant slopes can be the sum of both coil loaded slope, something between each coil loaded slope (still affected by their phase). To deal with that, they loose some noise nulling contrary to fluence due to phase mismatch. The point is (for me) that one coil can be set flat, while the other can be set peaky (and so higher order low pass slope). Here a image from a forum talking about fishman eq shaping. Modern active humbucker "dual slope" low pass is somewhat reaveling. It's all about slopes, peaks, and sums. The resultant differential sum concept is fun to play with. With one leg to ground, each coil is more independant. Don't know if it's a good thing, but it seems a pleasing idea. Doing so, the more high in frequency, the more one coil is attenuated, the more you got a single coil sound, and the more phase mismatch between coils you get (think comb filtering). Single/humbucker sum/amount is variable with frequency. There's a blackout preamp schematic on the web coming from a russian forum. I wasn't really confident about it, until i looked at seymour BMP-1 preamp pcb, and realizing now that the major change from the russian supposed blackout schematic is the lack of imbalance between coils inputs. I'll play with the bmp-1. I've already changed the op amp for a opa1692, and bypassed with muse cap the output caps. It halved preamp distortion doing so from 0,2 to 0,1 %. I plan to do a complex wiring, allowing balance, mixing coils of neck/bridge for differential amp, allowing phase change, pull-push load change, and using onboard mini-relay because i didn't managed to find 6pdt on/on/on switch. So, it will take some time before i could share results... I just discovered the awesome threads discussed here not long ago. You're doing a really nice job. Thanks for sharing.
|
|
|
Post by antigua on Feb 1, 2021 23:44:08 GMT -5
Hi, I really like all this stuff, maybe a bit too much, so if i'm wrong, i'll be really happy to discuss, and sorry for my poor english Fluence is a active pickup, but not the same way as emg or seymour's. From what i've seen, Fluence take the whole humbucker output, and eq it (i don't manage to find again the link of the patent). Emg and seymour uses differential amplifiers typology : conventional differential op amp, or with current source differential amplifier bjt pair + op amp. Each coil of humbucker has one leg to ground. So that loading isn't anymore linked between coil. The resultant slopes can be the sum of both coil loaded slope, something between each coil loaded slope (still affected by their phase). There's a site called "electrosmash" with a very detailed analysis of EMG pickups, and basically it's parallel coils with one of the coils having a series cap that attenuates the low end for that particular coil. From what I know about pickups in general, there's not real good reason to do that, the inventor of the EMG must have thought it sounded better than way, but that's an arbitrary judgement. Back in the early 80's, vintage was not revered like it is now, so they were happy to deviate further from the 50's sound, but these days that sort of design decision is a liability, and you can see how Fishman exploits the fact to boast that their futuristic pickup sounds like a vintage pickup.
|
|
papasteack
Rookie Solder Flinger
Posts: 5
Likes: 1
|
Post by papasteack on Feb 2, 2021 5:35:59 GMT -5
Yeah, i know electrosmash and others source pretty well, since around 10 years, and so i'm a bit suprised of your judgement, since Electrosmash site explain it really well, and show curves. Those are parallel coil, but it's not the usual parallel coil source (coil + it load). Differential amp isolate loading of each coil. Doing so, each coil can be "equed" by loading, and so differential amp act as a suming both coil with their umbalanced loading. Small mismatch response by equing is shown on electrosmash site. Even if i don't like how EMG did it, i like the topology. The preamp on it own add a lot of global EQ, they've gone too far for my tastes. And most people miss the fact that LM4250 on it own at low current setting slew limit response with gain, and so act as a very bad low pass (asymetrical slew rate increasing with input). I like the idea of keeping high, and still getting a little low freq resonnance. How can you get the kind of two step low pass curve in purple in my last post with a usual loaded passive humbucker ? A bit extreme example would be summing a flat curve and a high Q 4nd order low pass slope : There's still a nice resonnance, but without the fast low pass slope, and it would only keep somewhat single coil sound for highs. One can get the resonnance without it higher order low pass effect. Even if i understand that it may not be your target, it seems me it offer something unusual to tweak. I prefer somewhat seymour application in blackouts : link . 75k (150k//150k) load on left coil Vs 150k on right coil (the 680n cap load on left coil is a error, it must be 680p// I don't overlook the coils values from this shematic). I find this shematic interesting, for what it is.
|
|
|
Post by trantalocked on Feb 20, 2023 9:22:44 GMT -5
I was thinking for a while of how a pickup's resonant peak works with harmonics and the tone we perceive and the idea I came up with is that due to how we hear based on the relativity between frequencies, we hear the middle string 8th harmonics more forward on a P90, and the upper string 8th harmonics more forward on a Strat pickup. The open string 8th harmonic peak is usually located right above the middle of the bridge pickup and that was one of the key things that added up in my mind for how important it is. As a result of the Strat's 4kHz resonant peak being relatively higher than its 2kHz level - which is still very high - the P90 will actually have more audible 8th harmonic forwardness at 2kHz than the Strat, but the Strat conversely gets more 8th harmonic forwardness at 4kHz. With many EMGs, there is more of a focus on the 8th harmonic specifically for the bottom string due to the 600Hz response peak.
Anyway, that was more of an inductive reasoning thing since it was peculiar that I've read that Gibson chose the original P90 as optimal for electric guitar, and there had to have been a reason for choosing that 2.2kHz resonant frequency. All I could guess is the 8th harmonic peak, being near the bridge pickup for the most used frets and still at a high enough amplitude compared to the fundamental to be clearly audible, provides some extra air and bravado when amplified higher.
|
|