sickindian
Well-known member
I always been wondering how that works can anyone explain that here please?
Thanks
Thanks
- Thread starter sickindian
- Start date
beej
Moderator
Long post, I'd written bits about this before so just put it together. You have to consider that everything in your signal path contributes to the sound you're hearing.
Background
A guitar pickup is an "LCR" circuit. It has inductance (L), capacitance (C) and resistance (R). All three of these electrical properties help define it's sound. Change one property and you'll affect the output frequencies. For example, adding more resistance will shift the loudest frequencies of the pickup upward, causing the output to be more trebly, etc. Increasing the inductance will shrink the window of frequencies passed by the pickup, causing more of a midrangey sound, etc. Using a longer cable will add capacitance, decreasing highs in your signal.
The signals in passive guitar signals are what we call "high impedance".
Impedance
It's tough to explain impedance without getting too technical. Basically, it represents the relationship between voltage and current which a device is capable of accepting or delivering. For our purposes, it's just math. Every component adds together to affect the outcome, but not exactly in the way you'd think. For example, resistors in parallel add together like so:
1/Rtotal = 1/R1 + 1/R2 ... etc.
(Note that capacitance and inductance affect your signal too, it's just easier to talk about resistance for the purpose of discussion.)
Practical example- if you have one pot on your guitar (500k) and you wire up another one (500k), that formula tells you that the total resistance is 250k. By the same principle, if you wire up a small resistance in parallel it's going to drastically reduce your overall resistance (we'd call this "signal loading", it would suck highs from your signal), and if you wire up a huge resistor- 1 Meg (1,000,000) or so, it won't affect the total resistance much.
That's why the input impedance of guitar amplifiers is really high (you can think of it mostly as resistance). That way, they don't load your signal and affect your tone.
Loading your signal can be a useful tool. For example, Jimi Hendrix would use different length cords when recording, depending on the sound he wanted to get. Using a long cord with a lot of capacitance helps tame the brightness of single coils and give them more mids, exactly what you'd want for distorted guitar sounds. But you want those highs for clean playing, so a shorter cord would have less of an effect. Nowadays we can buy low capacitance cable if we're concerned about long cable runs. Or we can use a buffer.
Volume Pedals
Given all of this, you can work out the effect of a volume pedal in your signal path. A volume pedal is just like another pot in your guitar, one lug is wired to your signal, the other to ground (providing the 25k or 250k resistance). The middle wiper is adjustable and feeds the signal to your amp. (So no matter how you set your volume pedal, your guitar sees the 25k or 250k load in parallel.)
Adding resistances (like above), you can see that putting a 25k pedal in parallel with your passive signal is going to dramatically affect the impedance. Whereas the 250k pedal won't so much; it's more like another volume pot in your guitar. The net effect in both cases is to shift the the frequencies from your p'ups downward, giving you less highs.
With active p'ups or in an FX loop (where you're dealing with low impedances), the 25k pot doesn't have as dramatic effect.
So there ya go
Background
A guitar pickup is an "LCR" circuit. It has inductance (L), capacitance (C) and resistance (R). All three of these electrical properties help define it's sound. Change one property and you'll affect the output frequencies. For example, adding more resistance will shift the loudest frequencies of the pickup upward, causing the output to be more trebly, etc. Increasing the inductance will shrink the window of frequencies passed by the pickup, causing more of a midrangey sound, etc. Using a longer cable will add capacitance, decreasing highs in your signal.
The signals in passive guitar signals are what we call "high impedance".
Impedance
It's tough to explain impedance without getting too technical. Basically, it represents the relationship between voltage and current which a device is capable of accepting or delivering. For our purposes, it's just math. Every component adds together to affect the outcome, but not exactly in the way you'd think. For example, resistors in parallel add together like so:
1/Rtotal = 1/R1 + 1/R2 ... etc.
(Note that capacitance and inductance affect your signal too, it's just easier to talk about resistance for the purpose of discussion.)
Practical example- if you have one pot on your guitar (500k) and you wire up another one (500k), that formula tells you that the total resistance is 250k. By the same principle, if you wire up a small resistance in parallel it's going to drastically reduce your overall resistance (we'd call this "signal loading", it would suck highs from your signal), and if you wire up a huge resistor- 1 Meg (1,000,000) or so, it won't affect the total resistance much.
That's why the input impedance of guitar amplifiers is really high (you can think of it mostly as resistance). That way, they don't load your signal and affect your tone.
Loading your signal can be a useful tool. For example, Jimi Hendrix would use different length cords when recording, depending on the sound he wanted to get. Using a long cord with a lot of capacitance helps tame the brightness of single coils and give them more mids, exactly what you'd want for distorted guitar sounds. But you want those highs for clean playing, so a shorter cord would have less of an effect. Nowadays we can buy low capacitance cable if we're concerned about long cable runs. Or we can use a buffer.
Volume Pedals
Given all of this, you can work out the effect of a volume pedal in your signal path. A volume pedal is just like another pot in your guitar, one lug is wired to your signal, the other to ground (providing the 25k or 250k resistance). The middle wiper is adjustable and feeds the signal to your amp. (So no matter how you set your volume pedal, your guitar sees the 25k or 250k load in parallel.)
Adding resistances (like above), you can see that putting a 25k pedal in parallel with your passive signal is going to dramatically affect the impedance. Whereas the 250k pedal won't so much; it's more like another volume pot in your guitar. The net effect in both cases is to shift the the frequencies from your p'ups downward, giving you less highs.
With active p'ups or in an FX loop (where you're dealing with low impedances), the 25k pot doesn't have as dramatic effect.
So there ya go
sickindian
Well-known member
You just fried my brain!I'm pretty sure that i will read this quite few times before i will understand what i am lookin' for.
Basically im trying to connect either Ernie Ball VP JNR or Boss FV500L to my signal router and i dont know which one shall i pick and i think that in UK Boss is more practical due to strictly mechanical parts as i heard that the string from EB pedals breaks and you need to reset the pedal.
Do i need to treat piezo somehow different?
Thanks
Basically im trying to connect either Ernie Ball VP JNR or Boss FV500L to my signal router and i dont know which one shall i pick and i think that in UK Boss is more practical due to strictly mechanical parts as i heard that the string from EB pedals breaks and you need to reset the pedal.
Do i need to treat piezo somehow different?
Thanks
Last edited:
beej
Moderator
Ah, sorry. Thought it was more of a general question.
Quick answer, if your signal is active (after a buffered pedal, in an fx loop, or the piezo or blended output of your guitar) you use the 25k pedal. If you're using it after the passive output of your guitar, then use the 250k version.
Re durability- the EB pedals have been the standard for years. You hear about very few problems with them, and they're easy to repair. But there are a lot of different makes out there, whatever works for you.
Quick answer, if your signal is active (after a buffered pedal, in an fx loop, or the piezo or blended output of your guitar) you use the 25k pedal. If you're using it after the passive output of your guitar, then use the 250k version.
Re durability- the EB pedals have been the standard for years. You hear about very few problems with them, and they're easy to repair. But there are a lot of different makes out there, whatever works for you.
Slingy
Well-known member
It's also good to know that a volume pedal before the amp will clean up the sound like the pot on your guitar when you turn it down, but if you want to retain full output sound when using the pedal(I like this method), then you need to put it in the effects loop where it works more like a master volume.
sickindian
Well-known member
Thanks for the answers guys they're really helpfull.
