Tone Deft wrote:Timur - that link totally backs up what you've been saying. I'd still like to sit down and figure it out from a techie standpoint.
Yep, that link is right on the spot on what I learned about these things. I thought impedance bridging is common knowledge among technies.
The important sentence is right at the beginning:
Impedance (Z) is the resistance of a circuit to alternating current, such as an audio signal. Technically, impedance is the total opposition (including resistance and reactance) that a circuit has to passing alternating current.
A high impedance circuit tends to have high voltage and low current. A low impedance circuit tends to have relatively low voltage and high current.
For audio we usually want high voltage (signal strength) and low current because the audio-signal is voltage-encoded. So don't need/want the current coming from the guitar pickups, but only the changing voltages: voltage-level = audio-level, voltage-frequency = audio-frequency. With lower voltage levels we need more amplification and with more amplification we will hear more noise which is generated by flowing currents (electrons running through resistance).
There is one paragraph about cable-length as well:
A low-Z mic can be used with hundreds of feet of cable without picking up hum or losing high frequencies. A medium-Z mic cable is limited to about 40 feet without losses. A high-Z mic will lose highs and pick up hum if the cable exceeds about 10 feet.This high-frequency loss depends on the capacitance of the cable as well as the mic impedance.
Guitars are usually high-Z, so anything exceeding 10 feet aka 3m can redule the quality of the signal. Because of that special low-capacity cables are offered for guitars, though often their price is quite high. In fact the plugs on the cables have a capacity of their own, but with length the cable becomes the dominating factor.
There is one thing worth emphasizing when plugging guitars/bass into a line-input, which I didn't know or just forgot about myself:
But if you connect a high-Z source to a low-Z load, you might get distortion or altered response. For example, suppose you connect an electric bass guitar (a high-Z device) into an XLR-type mic input (a low-Z load). The low frequencies in the signal will roll off, so the bass will sound thin.
We want the bass guitar to be loaded by a high impedance, and we want the mic input to be fed by a low-impedance signal. A direct box or impedance-matching adapter does this.
So while the combination of pickups and cable can form a low-pass filter the wrong combination of impedances seem to form a high-pass filter. Who would have thought that you need to know so much tech stuff for such a simple thing as plugging a guitar into a computer?!
Simple answer remains: Use a HI-Z input or DI-Box/guitar-preamp and use a good cable (doesn't have to cost a fortune though, mine costs about 21 Euro/30$ and there are less expensive ones which are still good enough for most applications.
anyway, props for being on point the whole time and being cool. where did you learn all this? reading as a music geek or did you have some good work experiences?
My pleasure. I learned most of this from reading as a music geek, alot from various internet-sources, but some of these things are mentioned in manuals for mixers and audio-interfaces as well. I used to work for a company that both worked for television and had a big music-studio where I learned some of the basics as well (like impedance matching for maximum power transfer). Besides that I always was kind of interested in electronics and also learned quite alot in school (phsyics and chemistry lessons mainly). I really don't know much about electric-circuits anymore, though. So don't ask me about the schematics of a low/high-pass filter, I once learned it, but have forgotten these things now because I don't need them.
btw I pronounce your name like 'Timmy' in South Park. TIMUR!!
Hehe, my little sister uses to call my "Timmeeeey" exactly the way it's pronouced in south-park sometimes. But the correct pronounciation is more like "Timoore" or "Tim Moore".
