Are TCI pickups tuned on the guitar?

[Chip Burns]

I've heard rumors that TCI pickups are tuned to the guitar their installed in. Is that true? Seems like a pretty expensive process if they are.

 

[Warmart]

Everything I've heard has said they are tuned for the guitar model.

 

[Alnus Rubra]

My understanding and it’s fairly rudimentary, is that TCI is a process, not the actual pickup. The pickup is TCI tuned.

There are others that will explain this far better than me, I’m just a “wood junkie”!

 

[Warmart]

I’m just a “wood junkie”!

TWSS!

 

[Alnus Rubra]

TWSS!

D’oh! Forgot that means something different with you!

 

[Mozzi]

The way I understand it, which could be totally wrong, is that each Pickup, Resistor and Pot values are 'known' and by picking the 'right Caps value to go with the right Pot(s) and Pickup to get the 'exact' capacitance and resistance thy 'want'. As we know, even if two pickups are wired 'exactly' the same, there is a difference. A 500k pot for example can vary by 10%.

Instead of just picking the 'next' set of electronics to be installed 'randomly', they are being a lot more selective over what electronics get assembled together to get a more 'consistent' result. For example, if a Pickup is a little bit 'brighter' than usual, they can use a 'lower' value pot (maybe 460k) to 'tune' the tone...

I could be wrong in what the TCI Process involves and to me, the only thing that makes sense is to know exactly what values all these different Electronic components have and by 'choosing' the right combination, you have more 'control' over the outcome.

 

[Em7]

Instead of just picking the 'next' set of electronics to be installed 'randomly', they are being a lot more selective over what electronics get assembled together to get a more 'consistent' result. For example, if a Pickup is a little bit 'brighter' than usual, they can use a 'lower' value pot (maybe 460k) to 'tune' the tone...

The pot resistance in a guitar circuit does not actually make a pickup brighter or darker. What it does is affect the q-factor of the circuit. The q-factor defines the sharpness of the resonant peak. Q-factor is the ratio of inductive reactance (XL) to resistance (R).

Q = XL / R

As R goes up, Q goes down, resulting in a more even frequency response.

Most guitarists confuse a pickup's output with its DC resistance, but that is not how a pickup works. In fact, DC resistance is a poor measure of a pickup's output. What matters is the inductance and self-capacitance of the coil(s) as well as the strength and shape of the magnetic field. Inductance is a factor of the number of turns of wire on a pickup bobbin. Self-capacitance is a function of the number of turns and how the wire is laid down on the bobbin. There are two ways to increase the output of a pickup. The first way to increase output is to use a permanent magnet with a stronger magnetic field (i.e., a magnet with a higher gauss rating). That is why pickup manufacturers eventually switch over to using ceramic instead of alnico when attempting to boost pickup output. Ceramic magnets are available with higher gauss ratings than alinico magnets and unlike alnico magnets, ceramic magnets do not lose strength over time. The second way to increase output is to put more turns of wire on the bobbin. In order to do that with a stock bobbin, the pickup designer has to resort to using thinner wire. Thinner wire has a higher per foot DC resistance rating than thicker wire. That is the only clue DC resistance gives one when attempting to determine the output of a pickup. Higher DC resistance usually means more turns of wire, but more turns of wire also means more resistance per foot of wire due to the physical limitations of stock pickup bobbins.

Now, you have probably heard about wire with magical insulation. There is nothing magical about a wire's insulation other than its thickness. A wire's overall thickness is important when attempting to wind a higher output pickup with lower self-capacitance. A buzzword in the pickup industry is "scatter winding." Scatter winding is little more than imprecisely wound coils. A scatter-wound pickup bobbin usually has a lower self-capacitance than a perfectly wound bobbin. That is due to the fact that individual turns on the bobbin are farther apart (i.e., there is more air in a scatter-wound bobbin). A pickup with a lower self-capacitance usually has a higher resonant peak than a pickup with the same number of turns, but higher self-capacitance. The resonant peak is the frequency at which a pickup is loudest. It is easier to get more wire on bobbin that is perfectly wound by a machine than one that is scatter wound by hand or pseudo-scatter wound by a machine. However, perfect winding equals more self-capacitance, which equals lower resonant frequency (i.e., a darker sounding pickup).

Where the value of the volume pot comes into play is by lowering the q-factor of the circuit. As mentioned earlier, q-factor goes down as resistance with respect to inductance goes up. What happens is the frequency response of a pickup flattens out as the size of the volume pot is increased. In essence, the pickup does not get brighter, it gets less bassy because the resonant peak has been lowered, which widens the frequency response, making it sound brighter.

With that said, has anyone ever wondered why a Strat quacks in positions two and four? It is due to the fact that Strat pickups have a high resonant peak and inductances add in parallel while resistances divide, which means that the q-factor increases, resulting in an sharper resonant peak around which the frequency response drops off at an even faster rate.

In a nutshell, that is why TCI is called TCI, which stands for Tuned Capacitance and Inductance. The only time that resistance comes into play when tuning a pickup is adjusting the q-factor of the circuit.

 

[Alnus Rubra]

See I told you there are a lot of people here far cleverer than me!

 

[bodia]

See I told you there are a lot of people here far cleverer than me!

You and me both, brother!

 

[Chip Burns]

Thanks for the thorough explanation Em7.

From what I'm reading here is seems that TCI produces more REPEATABLE pickup performance by making the self-capacitance (C) and inductive reactance (I) more consistent from pickup to pickup using the TCI process.

But given Em7's equation:

Q = XL / R

TCI does not attempt to address variations in winding resistance.

Perhaps 58/15 LT pickups manufactured before the introduction of TCI (2020) might have the same performance as post-TCI pickups but its a crap shoot.

Any comments about my opinion?

 

[Black Plaid]

I would expect that, with a machine doing the winding, they can get very consistent results, but I suppose that really depends on the machine. And the machine that makes the parts that go into the pickup, like the wire and the magnets.

My read on TCI is that now they can tune a particular model of pickup to what they *want* it to be without having to guess as to how to make it get there. They have some equation that predicts the results, and can solve for the result they want instead of having to experiment.

Perhaps one day someone will take the time to empirically test a sample of TCI equipped guitars to determine what the variance actually looks like.

 

[Em7]

In reality, all well-made pickups are tuned to a point. Resistance is a function of wire gauge and turns of wire. A winding machine will place an exact number of turns on a bobbin every time. Modern fully-automatic winding machines will precisely wind many different patterns. The variable piece of the equation is the wire. Wire is drawn through a die to size it to gauge. Over time, the die wears, which means that the wire at the end of a run may be slightly larger in diameter than it was at the beginning of the process. Thicker wire has a lower per foot resistance. I do not know what tolerances PRS has set for its suppliers, but one thing is for certain that Paul and company did not get where they are today without setting tolerances for wire gauge and insulation thickness.

 

[Deleted member 5962]

I was going to post a must simpler version of what EM7 said. But now I don't need too. So why am I posting at all? Not sure.

Actually, the simplest version of what Paul said was that they basically have a resonance that they prefer as "ideal" for a given pickup and guitar, so they measure the pickup and then "tune" it to that resonance, with the other parts. So if pickup A is a little below that, they tune it up a bit. Pickup B is a bit above that, they tune it down a bit. The goal being to replicate a particular resonance that they prefer, rather than having them all come out differently and just installing them that way.

He went on to say that they do all come out different, and over the years there were always a few "magic guitars" that had these killer pickups in them that just sounded phenomenal, and if you measured them vs. the same guitar model that didn't sound as good, you'd find the differences in the "same" model of pickups. So you find the great ones, and can replicate those over and over with this process.

 

[Chip Burns]

So it sounds like the TCI process makes more *repeatable* pickups, and those pickups are modeled after what PRS considers its "best" or "most desirable" output.

 

[RickP]

I find dipping my pickups in snake oil makes them all sound the same.

*ducks*

 

[Chip Burns]

The obvious question is, what kind of snake?

 

[RickP]

The obvious question is, what kind of snake?

Edit: BTW, just playing with you boys. I’m sure Paul knows what he’s doing.

 

[Alnus Rubra]

Edit: BTW, just playing with you boys. I’m sure Paul knows what he’s doing.

If he lurks on here, PRSh will be spitting like a Python!

 

[Deleted member 5962]

The obvious question is, what kind of snake?

I was thinking the obvious question was "how do you get the oil out of the snake?"

 

[Alnus Rubra]

I was thinking the obvious question was "how do you get the oil out of the snake?"

Is that like the opposite of Popes in a Volkswagen?