Active Pickups Anyone?...

[Mike Sulzer]

If you think that it is imposible to modulate sound of pickup with coil winding, then it is your personal opinion and it is wrong.
Especially for you we made some measurements of first that came to hand coil 6500 NT 43AWG with 500pf and without.
Measurements were on active probe with in MOSFET Cig - 2.1 pf with gigantic Rin.
And just for matching we gave you coil with 5000 NT 42AWG here Machine vs handmade winding, some tests with interesting results please take a look.
Take a note that with air coil 5000 NT have RP - 8.300 kHz. We also have a a coil with RP - 25.85 with the same number of turns in this thread.
Can take a any bet that it is possible to make a coil with 43AWG 6500NT with the same RP, that the same coil + сap 500pf.

If I understand you last sentence, you are claiming that a 5,000 turn coil can have a resonance at 25.85 KHz or 8.3 KHz depending on how you wind it. These appear to be standard bobibns, and so the inductances would not be very different, and therefore it must be the capacitances that are different. Since the resonant frequency varies with the square root of cpacitance, the capacitances are in the ratio (25.85/8.3)^2 = 11.79. So you are claiming that you can vary the coil capacitance nearly a factor of twelve depending on how you wind the coil. I find that very hard to believe.

[MrCandy]

Some thougts on actual thread
"Artificially" modulated AFC with preamp will allways sound wose than "naturally" modulated.
Blame Q factor for that

[MrCandy]

Not it is not. There is no way you can wind enough wire on a standard bobbin so that it will have the save resonant frequency directly into a pre amp as when operated into a guitar cable. You need at least about 500 pf. You have to add some.

If you think that it is imposible to modulate sound of pickup with coil winding, then it is your personal opinion and it is wrong.
Especially for you we made some measurements of first that came to hand coil 6500 NT 43AWG with 500pf and without.
Measurements were on active probe with in MOSFET Cig - 2.1 pf with gigantic Rin.
And just for matching we gave you coil with 5000 NT 42AWG here Machine vs handmade winding, some tests with interesting results please take a look.
Take a note that with air coil 5000 NT have RP - 8.300 kHz. We also have a a coil with RP - 25.85 with the same number of turns in this thread.
Can take a any bet that it is possible to make a coil with 43AWG 6500NT with the same RP, that the same coil + сap 500pf.

[Wired]

I'm not chasing a flat response. Not chasing any particular response, really. Just wondering if there's any winders out there who might be interested in a micro pre that is tweakable so they can experiment with active p'ups. Another tool that helps them chase the response that their customers might be looking for...

[Mike Sulzer]

Mike, there's a popular bass preamp from a company called Audere Audio that features both resistive and capacitive loading switches. The idea is to simulate a passive tone when you want it. They offer a low, mid and high Z mode. The low Z mode is loaded with a cap, and the high Z mode is the straight buffered tone. The mid Z mode has a lower input impedance using resistors.

So that's what he's also doing here.

I see; that's good information. But that brings up the issue that what you want to do for a guitar and a bass could be different; probably are.

if you look here:Audere Audio Technical Details about Impedance in Electric Guitars, you see that the high Z setting has a resonance just under 4 KHz as they have it configured. It seems that this is achieved by loading with a capacitor. It would be very low for a pickup by itself, and in the section called "Adding Capacitance", they explain that you can switch in more or less C to move the resonance to where you want it. This is exactly what I was talking about above, and not what Wired said he is doing.

So the "High Z" mode is like a cable to a standard tube amp input, but you can switch the cable capacitance, and the resonant peak is higher in amplitiude than in a normal passive situation because there are no controls providing additional load.

The MID Z mode damps the resonant peak. The response rolls off smoothly, down about 3 db at 4 KHz. The claim is that this is what the normal pot loads do. I do not think that this is always true, maybe not typically so.

The LOW Z mode provides a lower impedance load, although the details are not given. This tends to emphasize the bass, probably because of the pickup inductance. There is an additional claim which I find hard to believe. They are claiming that a pickup can extract enough energy from the strings (with a low Z load) to damp them more quickly and to stop interactions between the strings. I think that the coupling between the string and the pickup is way to weak for this to happen. Also, somehow this is supposed to be like having an individual coil for each string. This makes no sense.

[David Schwab]

Mike, there's a popular bass preamp from a company called Audere Audio that features both resistive and capacitive loading switches. The idea is to simulate a passive tone when you want it. They offer a low, mid and high Z mode. The low Z mode is loaded with a cap, and the high Z mode is the straight buffered tone. The mid Z mode has a lower input impedance using resistors.

So that's what he's also doing here.

[Mike Sulzer]

No, I was talking about Z loading.

Z means impedance, a complex number describing the effect of Rs, Ls, and Cs connected in a circuit.

You seem to be attempting to achieve a flat frequency response. That goal is at odds with one important factor that sets the tone of an electric guitar (passive pickups): the resonance caused by the pickup inductance and cable capacitance (in parallel with the smaller pickup capacitance). Pickups differ as to the height of the resonant peak, with humbuckers a bit lower than many single coils (although taking the cover off a humbucker tends to increase the height of the peak a bit).

By the way, electric guitars already have a way to load the pickups: the tone control. As you turn down the tone control pot from ten, the major effect is changing the resistive loading on the resonant circuit. This is because the impedance of the capacitor in the range of the resonance is a lot less than the pot value. As the pot gets closer to zero, the capacitor becomes important, but the initial effect is just resistive loading.

If you load the pickup as you suggest, the major effect is to eliminate the brighter tones by loading the resonant circuit. These are then no longer available since you have reduced the range of the tone control.

[Wired]

No, I was talking about Z loading. The idea of low or medium input Z preamps is that then the pot values, cable capicitance etc doesn't enter into the equasion. So you get the "loaded" sound no matter how long your cable is, or what the input Z of your amp or effect pedals are or where the vol pot is wound to etc. Most guitarists only hear a treble roll off when Hi Z passive coils are loaded by pots and leads, but there's more than that going on. Bass amps have a much broader freq response, especially if they have a Hi Freq horn driver.

eg. Series/parallel. If you hi Z buffer both settings, and match their gain, the difference in tone is much less than a passive series/para switch. Because the series setting is higher Z and is loaded more by the pots and cable. Also a switch in loudness is often percieved as a tonal difference. I had a bass I used to direct record with so I had a push-pull that did nothing but add 8db of gain. A friend borrowed the bass and when he discovered the switch, he never played without it on. Turning up the amp gain would have exactly the same effect, but he swore that it was different. I think this was because he was used to hearing it switched in and out, if you know what I mean...

Guys would be welcome to put a cap, or any filter arrangement they wish on the input of my pre, should they want to experiment in that way.

[Mike Sulzer]

About pre input capacitance I can say that it must be minimal and it is better to not touch it, you can model frequency response with coil winding
and it is better that way.

Not it is not. There is no way you can wind enough wire on a standard bobbin so that it will have the save resonant frequency directly into a pre amp as when operated into a guitar cable. You need at least about 500 pf. You have to add some.

[MrCandy]

Not sure what you mean, but if you are saying that a good passive pickup sounds good with any load, I am not convinced.

The idea was that pickup with well selected frequency response when it was made will sound better than pickup with failure frequency response
under equal conditions(cable capacitance).
About pre input capacitance I can say that it must be minimal and it is better to not touch it, you can model frequency response with coil winding
and it is better that way.
We have already given an example of bad pickup sound modeling with the help of preamp and Rin dances in previous post

[Mike Sulzer]

That it is and I agree, but if pickup have failure frequency response originally nothing will help to make it sound.
For example if pickup have good attack characteristic originally(easy cut out of flageolets), than pickup will be fine with any load.(flageolets will sound as they sound with any load)
We can take EMG81, it seems that everything is fine, but we can rarely make the flageolets happen anyway

Not sure what you mean, but if you are saying that a good passive pickup sounds good with any load, I am not convinced.

[MrCandy]

You mean variable capacitor loading? It is the cable capacitance that matters in a passive setup.

That it is and I agree, but if pickup have failure frequency response originally nothing will help to make it sound.
For example if pickup have good attack characteristic originally(easy cut out of flageolets), than pickup will be fine with any load.(flageolets will sound as they sound with any load)
We can take EMG81, it seems that everything is fine, but we can rarely make the flageolets happen anyway

[Mike Sulzer]

Some people like the loaded sound of pickups. That's why my pre would have an adjustable input Z.

You mean variable capacitor loading? It is the cable capacitance that matters in a passive setup.

[Wired]

Anyway, I think we are getting off topic.

Really just wanted to see if any winders out there were interested in producing active pickups but didn't have the electronics knowledge to follow through... Active/passive, and series/parallel switching and cable capacitance and loading etc are interesting topics, but not really what this particular pre would be aimed at...

[Wired]

the problem with most pots from electronics stores is that they only have 6mm of thread. Fine for scratch plates, but not long enough for most through-face guitars. Also PCB pins can be a bit of a PITA compared to eyelets to solder to.

Some people like the loaded sound of pickups. That's why my pre would have an adjustable input Z.