Inductors for Passive Guitars

[ChrisK]

Inductors for passive guitars. These are small signal audio coupling transformers. These are what Torres and others use for their mid-boost kits.

Mouser Triad small signal transformers

X_L= 2piFH

Inductive reactance = 2*3.14159*Frequency*Inductance (H).

Inductive reactance = Inductance
2*3.14159*Freq(Hz)

Assuming that the impedance (not resistance) is measured at 1 Khz, a 10K impedance transformer winding would have an inductance of 1.6 Henry.

A 15K impedance transformer winding would have an inductance of 2.4 Henry.

A 7K5 impedance transformer winding would have an inductance of 1.2 Henry.

Assuming that both windings are used, the possible inductance could be four times that of one center-tapped winding. (Inductance is proportional to the square of the turns ratio.) Conversely, using one-half of a center-tapped winding would result in an impedance of 1/4 of the full winding.

[pablogilberto]

Hello!

I'm interested with this mid boost mod for passive electronics.

I have 3 questions.
1. How do you wire the inductor?
2. How to choose inductor values?
3. Do you have updated link where I can purchase this?

Thank you!

[blademaster2]

I have used - in my own guitars - a 1000mH inductor to give a mid-cut in place of a traditional tone control (I sometimes call it a "fatness" control), but I have not tried it for mid-boost. This inductor was pretty costly because it was very small, but the older post on this thread identifies other devices that might be cheaper

As an alternative, for mid-boost I have a Hagstrom guitar that uses both a series capacitor and a shunt resistor (switchable on separate switches, and it has no tone control knob), which is simpler than using an inductor, although it might not give you as much boost as a second-order boost circuit could. Essentially you are using the inductance of the pickups themselves in conjunction with the capacitor/resistor.

[pablogilberto]

Can you share the diagram?

What are the capacitor and resistor values so I can try them?

Thank you!

[frets]

You buy a 1.5H audio signal transformer from Mouser. You clip the middle leg on the side that has a “P” on it. You clip all three of the legs on the other side.  Then you get an A500k pot, a .039 cap, a 1M resistor, a 270k resistor,a .0022 cap. You take the .039 and solder the 270k between its legs. You take the .0022 and solder the 1M resistor between its legs. You get your pot and solder the .039/270k combination on lug 1. You then solder the first leg of the audio signal transformer to the to the other leg of the .039/270k,then you ground the audio signal inductor to the pot using its other leg. You solder the .0022/1M combination to lug 3 of the pot. You ground that combination to the pot.  You take a black wire and solder that to the pot. You take a white wire and solder that to lug 2 of the pot. You run the white wire to the Volume Pot or to Jack hot.  You ground the black wire. You’re done. This is how mine looked. 

[frets]

[blademaster2]

Nov 15, 2019 3:33:26 GMT -5 pablogilberto said:

Can you share the diagram?

What are the capacitor and resistor values so I can try them?

Thank you!

The Hagstrom II schematic shows this. The resistor is 12kOhm (if I read the writing correctly) and the capacitor is 3000pF.

The "Mute" switch invokes the low-pass response and the "Tone" switch invokes the high-pass response. Personally I am not in love with the result when both are switched, but it does boost the mids (actually cuts the highs and lows to achieve a similar result).



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[Deleted]

PickUps.. Transformers and Inductors all the same line of stuff, the sort of Anti-Cap, where caps move Phase one way the Inductor moves it back.