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Post by JohnH on Feb 5, 2024 16:00:08 GMT -5
I looked through the links above, but didn't see specific data on piezo capacitance and preamp input impedance. But the ghost summing board does indeed seem to join them all In parallel, so they could add up to a substantial C value. So I reckon you could test with various resistors from preamp piezo input to ground. Maybe a (500k ?) pot to start with, so you can adjust ahead of deciding on a fixed value?
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Post by JohnH on Feb 5, 2024 14:44:09 GMT -5
I'm also thinking if input impedance. I had similar issues with my (very different) home-brew build that you linked to above. The piezos react to pressure that they sense, and if they are feeding a very high impedance, their frequency response is huge, down to very low sub-bass frequencies. With my one, I was expecting to need the preamp to be high impedance, but this gave me crazily low frequency response. It worked fine for all the actual string vibration, but pressing on the bridge could create a huge almost dc pulse that blocked out all sound for a second or two by maxing out the input. I needed to decrease the resistor that set my preamp input impedance, so there was enough signal draw to bleed off these unwanted low frequencies and dc transients. My piezo was a buzzer element, same theory as a commercial piezo pickup but quite different value, with a high capacitance. I needed an input imoedance decreased to 150k, and then it solved this completely with no change to sound. The C of the piezo znd the 150k R gave me a roll off below about 50hZ and was fine for stopping the piexo getting swamped by low pulses. I dont know if your issue is the same. I'm surprised that a commercial unit would have this issue unless the preamp is not part of the family. If there is a similar issue, it would be good to find out the capacitance of the piezos in order to judge the input impedance needed. EDIT: I see finn has also homed in on his idea!
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Post by JohnH on Feb 2, 2024 19:26:21 GMT -5
hi kitwnSo Im picking up that you are British? and like me, live down in Oz? I remember those Philips kits, my friend had one. I got by with actual bits of wood as a breadboard, with nails and solder. And then I got a T-Dec plug-in board that you could push components into, and sat upstairs making bizarre and very noisy devices out of transistors and other parts bought as bulk packs. My mother blamed me for any interference picked up on our TV. I got as far as making a working 8-bit computer in 1977 (SC/MP chip), that you could program in machine code. It had 0.25k of RAM and drove a graphics card with 1k into an old TV. I wrote a shooting game where cruise missiles ('>' symbols) would fly across the screen getting lower and lower, and you fired at them to try to shoot them down with '^' symbols and if you hit one it would explode with a satisfying '*' symbol. The score would increment. But if you kept missing, the missile got lower and lower until it dived down steeply and blew you up with a mushroom cloud of *'s !. At that point development had to be put on hold due to no more RAM. Then I thought, I'm sick of this, there's never gonna be any future in it, and I went off to study structural engineering. Apparently Bill Gates came to a different conclusion in his garage.
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Post by JohnH on Jan 31, 2024 16:42:48 GMT -5
I've noticed a puzzling side issue with this thread. What should the equation really look like? On a new Windows laptop running Edge, it looks like this (screenshot): On a Samsung S22 running Android, it looks like this: (ignore size difference, just a due to different screenshot parameters between phone and laptop)
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Post by JohnH on Jan 31, 2024 7:31:34 GMT -5
This reminds me of circuits that we rigged up in science lessons at high school, age about 12, out of switches, light-bulbs and a battery.
It taught us computer science AND electrical engineering.
Plus, we learnt either that we wanted to be technical nerds, OR the type who hated such boring details and would grow up to make a lot more $ by employing us.
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Post by JohnH on Jan 30, 2024 16:23:56 GMT -5
I think that trying to get a clear single meter reading of inductance on a pickup is subject to some plus or minus depending how its done. This is because any equivalent circuit that properly captures its real response will not be a single simple inductance, but it will be more complex. That being said, it's still a really useful parameter if done consistently.
But it may not correspond exactly to L values back calculated from bode plots, and its not necessarily a reflection on either method.
One shift that happens, when assessing a real pickup with eddy effects and damping with bode plots, is a result of integrating. The integration definitely is the best way to present results because it evens out the curve, and where there are no particular effects happening, gives a flat response.
But the act of integrating effectively rotates the curve by 6dB per octave. So if the response is a real one with a rounded peak, it's rotating the top of the hill! So the place that was just before the peak pre-integration, is now at the peak, and its a slightly lower frequency. If there was a perfectly undamped peak of very high Q, as predicted for LC resonance by the simple equation, the peak is so sharp that this shift doesn't occur.
Also as noted before, any damping does tend to reduce the frequency of the maximum response in a resonant system.
And why integrate? If the bode plot is raw with a frequency sweep of constant magnitude, it tends to rise. Integrating it flattens it out for neutral responses. This actually matches well with real strings. In a theoretical perfectly balanced string set, all of equal tension when tuned, the added moving metal in the lower strings compensates for less induction at lower frequency and we get about the same magnitude of response by plucking each string, (then subject to all the interesting quirks that we are investigating)
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Post by JohnH on Jan 29, 2024 17:00:58 GMT -5
Easy!
that is the number 35, as written on a 1940's Underwood travel typewriter that was used during the whole career of a retired war correspondent until he stepped on something that went 'click' 'boom!', and after that he had to slow down a bit.
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Post by JohnH on Jan 29, 2024 3:38:56 GMT -5
Yes in general, for most resonant systems be they electrical, mechanical, accoustic, or the mood swings of an adolescent tree-frog, the addition of damping slightly reduces the frequency of the maximum signal. We can measure this and it comes through in the tests and in analysis models that include such damping.
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Post by JohnH on Jan 21, 2024 21:05:49 GMT -5
A couple of temporary flying leads to connect where a tone control would go, taken outside the guitar, then you can attach various R and C combinations, (maybe the R is a pot), to find out what suits you. Then you can hardwire your choice inside the guitar.
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Post by JohnH on Jan 7, 2024 1:44:51 GMT -5
Hi Spike, from what you describe, I'd say it's probablg doing as expected in position 2. In this setting it would work like a standard Les Paul or similar. If you don't want full volume, then the variations and mixes happen when you turn down a bit, you can hopefully get more of one pickup than the other if you wish. And if turned down, then the tones should start to act seperately. But at full volume, both tones act on both, as on an LP. Also, if you turn one pickup to zero in position 2, it shunts the other as well. But you wouldn't really do that, if you want just one pickup, set it with the switch.
So my guess is it's as intended, and these effects are what happens with 2V2T systems. LP players work with it. There are wirings that try to address these issues, but they have more adverse effects on tone in an attempt to solve problems that aren't really too bad.
Does that sound like what's happening?
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Post by JohnH on Jan 6, 2024 17:12:17 GMT -5
Thanks yes, I'll check it out. J
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Post by JohnH on Jan 6, 2024 15:56:18 GMT -5
Im sorry Im having trouble reading that, its a bit blurry and my vision is already blurry. Its doesn't look like what I drew and I'm not seeing any output in position 3?
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Post by JohnH on Jan 4, 2024 15:32:18 GMT -5
Can you please confirm which diagram you have now? is it the very first on this thread?
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Post by JohnH on Jan 4, 2024 14:55:22 GMT -5
It looks like you're close ( I haven't checked the diagram though). Have you thought about a Fender S1 switch pot instead of a normal pp switch? It's a four pole switch on a pot and the extra two poles might let you get those phased settings. Obviously, it fits in a Strat too.
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Post by JohnH on Jan 3, 2024 15:50:48 GMT -5
This is an aside, but thought I'd post about resonant peaks and why we aren't seeing them clearly: When we plot pickup tests to give bode-plot sweep responses such as in tests by Antigua or ms, we see the electrical response of the pickups, on it's own or together with a load representing the guitar wiring, based on a consistent frequency input induced by a coil. There is no effect of the actual string vibration, nor of the acoustic performance of the speaker. These tests are very insightful and usually show a smooth curve with a treble peak. We can also generate plots like this by analysis. But such a loaded test on a PAF usually gives just a very subtle peak, and with a real signal induced by strings, the peak is masked. GuitarFreak is a spreadsheet loaded with pickup models derived from Antigua's physical tests, and it matches them pretty well using 6 components to represent each pickup, plus the guitar wiring. It also has the math built in to address string vibration, pickup width, position, and vibration harmonics. Here are plots based on a classic '57 with 500k pots, and the low capacitance cable discussd above. The top blue dashed curve is the electrical response with this load, approximately as would be derived from a bode-plot sweep. You can see a slight peak, but it's very subtle. A higher cable capacitance will bring a stronger peak. The red jagged line represents an analysis of the real signal output from the guitar, based on strumming across all the strings. I've set it to be with open strings, starting with low E. This spiky line is comparable to the real frequency plots from the tests, except for: 1. the real playing generates hundreds of harmonics, hence very finely-spiked lines. My red plot does 30 harmonics of each string, but to plot them it shifts them each to the nearest semitone (to save data points), so the curve is somewhat cruder and more blocky, but has about the right trend. 2. GF doesn't include the speaker response, which adds a further shaping and fall-off after about 4kHz (actually, I could add that to GF, it's not too hard!) So now comparing; the red curve is falling off after the last strong peak just above 3Khz. If you look at the real plots posted above, you can kind of see a similar thing, with peaks dropping away after about that frequency, but there's some interpretation needed. Anyway, I hope that is a bit interesting at least!
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Post by JohnH on Jan 2, 2024 14:58:12 GMT -5
On the tone controls, as frets noted, they are 'Greasebucket' circuits. You can read about these on our Tone Controls section. The net result of the two caps and resistor is virtually identical to that of a single smaller cap of about 0.017uF, with the extra resistor in series. What this does is to make the tone range stop just short of the usual minimum setting where you suddenly get a big 'honking' tone. It's like a tone knob that goes down to 1 instead of 0. So if these tones are a place where you like to go, the GB circuit may make them easier to set.
I had these on my Am Special Strat, but changed to a normal tone circuit. I quite like that 'tone at 0' sound, with some fuzz.
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Post by JohnH on Jan 1, 2024 15:43:14 GMT -5
Here's the plots as before this time covering the range 1000 to 5000 Hz: Not sure what can be deduced there! But, if we're looking at pickups with L in the range 4.2H to 5.4H, with capacitance of 214pF (cable) plus allow 100pF (windings) plus allow 100pF (amp input and general guitar wiring), then we are looking for treble resonance in the 'ball park' range 3400Hz to 3800Hz. This is quite a bit higher than usual for humbuckers in this inductance range. Â I am wondering if preferences might be different with a higher capacitance cable, giving a somewhat thicker (and more common) sound. That's a good point, and sometimes having very low capacitance throws the natural resonance up past the point where guitar strings and guitar speakers are most effective, so a bit more capacitance might make an apparently brighter final sound. But the recordings sound great anyway, its just that the cable can be a significant variable. I used to put buffers in my guitars, untill I figured out that they sounded better with a good normal cable.
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Post by JohnH on Dec 31, 2023 15:38:49 GMT -5
Here's the plots as before this time covering the range 1000 to 5000 Hz: Not sure what can be deduced there! But, if we're looking at pickups with L in the range 4.2H to 5.4H, with capacitance of 214pF (cable) plus allow 100pF (windings) plus allow 100pF (amp input and general guitar wiring), then we are looking for treble resonance in the 'ball park' range 3400Hz to 3800Hz.
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Post by JohnH on Dec 31, 2023 6:11:24 GMT -5
Nice looking guitar!
I'll plot out those charts to pick up 1000 to 5000hz, to see if it reveals anything about the resonant peaks. It's a lot about the cable capacitance in this case. How long is the cable?
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Post by JohnH on Dec 29, 2023 23:09:42 GMT -5
Thanks for posting those, so I did some stuff: I brought all the clean clips into Audacity, and put them each to a separate track. One thing I noticed is how well synced they all the were, All 5 together played perfectly in time, like 5 players together. Then I took the first 3 sec riff of each one and put them end-to-end to get a quick side-by side 1, 2, 3, 4, 5 comparison. So my impression was, all of a similar family of tones, with 1 and 2 being very similar, 3 being a bit lighter in tone and 4 being a bit thicker. 5 was also thicker but not as much as 4. Does that impression correspond with anything IRL? Then I got some frequency plots: 5 traces, focussing on 100 to 2000 hz, key at the bottom: On this kind of plot, just look at the peaks, since that's where the notes and harmonics are. The ones where I heard the greatest difference, 3 and 4, are the green and orange traces. So will you now reveal what you have there?
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Post by JohnH on Dec 29, 2023 15:08:40 GMT -5
Lots of reasons to have a good cable, but for tone, I think decent quality and don't make it too long works fine. If you can work with a reasonable 10' cable, its already got a 2x advantage in low capacitance and low noise compared to a much more exotic 20' cable. Of course if for stage reasons you need a long cable, then that's all different, but you can still go 10' to the pedal board, then provided there's a buffer there, go as long as you like from there back to the amp.
On the video, yes its a very nice recording, and does a great job of clearly conveying the amps. I see the mic is central, which might often bring up a very bright tone, but we don't know what post-EQ is applied or if any room mics are in play?.
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Post by JohnH on Dec 29, 2023 14:56:17 GMT -5
I think they all sound very good, but its hard for me to notice a difference in the pickups because the tones seem to be dominated by the amp overdrive and its all in about the same range of drive. That may well be the tone that most would wish to get with these pickups, but a crystal clean, or at most a slightly break-up tone with some chords and picking and different dynamic levels might reveal more.
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Post by JohnH on Dec 26, 2023 14:17:30 GMT -5
hi georgegtyThanks for posting and welcome to GN2! The October 2020 is the latest I have. Everything is intended to be as hum-cancelling as possible, ie humbuckers and any full two-coil or four-coil combinations both in and out of phase. Obviously single-coil or three-coil mixes can't be, or if you mix a coil from each pickup but one is reduced volume. There are no dead settings. One area where various JP schemes vary is in how the series mode works. With JHJP as drawn, you pull the series switch, and the the main toggle is completely bypassed, ie it goes to series on all three positions. This is so you can preset a standard tone on the toggle and then move in or out of series mode with just one switch move. The other key difference is that in series mode, the two sets of volume and tone controls are still active, and they act only on their respective pickups. This gives a huge range of tones with much clearer variation than parallel mixing. eg Try a neck single with a bit of bridge humbucker with treble muted, added in series. If you'd like to try it, the first job is to confirm your pickup relative magnetic polarities and applicable wire colours.
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Post by JohnH on Dec 23, 2023 15:56:15 GMT -5
...but on 'Boutique' construction, I can definitely appreciate the skill and care of a builder constructing a hand-wired circuit. I know how difficult it is and therefore how beautiful it can be when you see something done right. It's often such a shame that this work is hidden to all except those that can open the case. (Or lift off the pick guard to see a guitar harness made by frets!)
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Post by JohnH on Dec 23, 2023 15:36:08 GMT -5
Good design, good construction and high-quality parts are the key. I'm always sceptical of most NOS mojo of old components. But I can believe in great old valves, maybe a special transistor or diode, but not an old capacitor etc. I'm not a collector, but I do have one 'collection' of pedals that sruck a chord with me for the care and engineering that went into them. It's the Digitech 'Hardwire' range, which ran from about mid 2000's, for a decade or so. These are mass produced, but engineered with incredible care, super robustness and thoughtful features. The drive pedals are analogue and the modulations are digital. But these are seriously pro quality and never got the attention they deserve. You can still buy most of them used, for several hundred each (more than when new). I bought a full set, new, as their prices dropped at close-out. I have them all mounted on my home board so they are safe and ready to do what they do! (There's also a couple of other favourites there, a Boss OD3, a modded Guv'nor II and a germanium fuzz.)
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Post by JohnH on Dec 21, 2023 14:17:59 GMT -5
hi Spike
I'm glad that worked, so even if you'll move on to a different scheme you were able to learn from trying it. Plus it might help you figure out the next one.
Neck-on and its variants are about the simplest Strat mods that you can do, so also maybe the most useful. It's all about getting the missing two basic combos that you can't get on the 5-way switch, being Bridge and Neck in parallel, or all three.
That doesn't include other varmints such as phase or series wiring, but that's another story.
But for what the neck-on does, there are three basic ways to wire it. They give the same overall set of sounds but operate differently:
1. You can force the neck to be on when you pull the switch. The switch connects the hot neck lead to the volume pot, or the wire that leads to it. That's neck-on.
2. Same as above, but using the bridge, for 'Bridge on'
3. Put the switch between the hot Bridge and hot Neck wires. Now, whenever you select N you get N+B, and the same if you select B you also get N+B.
The only real differences are in how you use the switches, particularly what you can do with just one move. Option 1 is ideal if you want to sit on the B pickup and quickly thicken it to B+N. But if you are already at N, then pulling Neck-on makes no difference and youd have to aldo move the 5-way. So then option 2 might be preffered.
Option 3 could be good, but you get the same tones at position 1 as 5 with switch pulled.
All will get all three, in positions 2 or 4 or both depending which option.
Maybe the current new wiring will let you decide what is more useful? At least with any of these, if you keep the switch pushed in, its still standard.
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Post by JohnH on Dec 19, 2023 14:45:45 GMT -5
I'm glad that's getting better! The pot cases and the switch are good if they are grounded to the shielding, by contact is ok, but its not part of the main signal. It'd work either way, but maybe better noise control.
If yoh prefer to ground the cases that's ok too. The push-pull probably has a lug for this at the top of the switch.
(It's a very old diagram, one of the first I ever drew)
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Post by JohnH on Dec 18, 2023 5:02:14 GMT -5
Thanks for posting the diagram
It looks to me like it would work. But one thing you could check on your switch is which are the common pole lugs. Your sketch has them top left and lower right, which might be right but sometimes the two sides can be half a step offset, or flipped. So worth checking.
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Post by JohnH on Dec 17, 2023 14:21:01 GMT -5
Thanks yes I did see this. Also, can you please describe what happens in each setting?. So far there's no info for us to help you
J
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Post by JohnH on Dec 16, 2023 16:44:13 GMT -5
Thanks for linking my old design. It's one that combines my favourite options from HSS, with no fluff. On the blending, it does both series and parallel blending of neck single and a bridge coil.
It should be checked just for QA, since I haven't actually built it to date.
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