can anyone please enlighten on 'impedance matching ' signal path?

[bobster]

hi guys-
i was wondering if anyone could explain in simplish terms what i could do to impedance match my gear...
i have some old school pedals and some new and they dont always seem to be working right together with volume drops and wahs sounding weird etc...........
is there some way to measure impedance [ i have a simple dmm ] e.g. via pedal jacks and is there something i can do to make sure everything is going at optimum to ensure best tone a la eric johnson for example ? im wondering if boss pedals in between stuff as buffers or something of that ilk may help? even some info as to what this concept all means would be cool
i mainly use in this order a  fuzz face neg grnd / 70s small stone / carl marting hot drive mains powered / boss dimension c / boss dm-2 delay or boss dd2 delay and a rangemaster pos grnd . [ very occasionally i put a whammy in front of the lot ]

any elucidation on the above would be most wilkommen !
thanks - bob

[demonstar]

I'm not really sure this is what your after but hey mentioning it does no harm...

"What is impedance? And why does it do those terrible things?" from geofex.
If that was what your after theres a great analogy of impedance in the archives here are about big man and small door.

is there some way to measure impedance [ i have a simple dmm ]

If you search i believe this has been discussed on the forum before several times. I can't remember (thats bad when I only read it this morning  ) but there is a way of measuring impedance using a standard multimeter and turning the pot to half way and measuring the resistance. Something along those lines.

Sorry thats very vague I don't fully understand this area myself yet. I'm barely hanging on!

Just as a footnote, If anyone that comes into this thread could explain in various different pedals which components set the input impedance that would be great. maybe a PM so I don't side track the thread?

[R.G.]

i was wondering if anyone could explain in simplish terms what i could do to impedance match  my gear...

I'll try, but the first thing to do is ... don't!

Impedance matching is something that you only want to do for maximum POWER transfer, like with AC power lines or radio signals. You want maximum signal voltage transfer, not maximum power transfer. Here's the difference.

Imagine you have a garden hose and a variable nozzle. For water, pressure is like voltage. Flow rate (as in gallons per minute) is like current flow. Power is the product of pressure times flow. If you have the variable nozzle turned all the way off the hose has maximum pressure in it. If you open it just a crack, the water spurts out in very fine, but very fast sprays. That's high pressure transfer of the water. As you open it more, you get smaller, but still significant pressure and a lot more flow, the single-stream spray you use for maximum force or distance. That's maximum power transfer. As you open the nozzle more, or even unscrew it off the end of the hose, the flow rate goes up but the pressure drops. That's maximum current transfer.

In voltage based signals - and guitar electronics is this kind of thing - you want to transfer the maximum signal voltage. That necessarily implies that you want whatever gets the signal voltage to eat up only a negligible amount of signal current. We define resistance as the ratio of volts to amps, so we want a high resistance input - many volts per amp; generally about a million volts per ampere (1 megohm) is good. With resistances that high, almost all the signal voltage gets into whatever we're feeding.

Impedance matching implies the most power - voltage times current - gets transferred. This is important in radio, but not audio. You want an impedance mismatch, but mismatched the right way, so almost no signal current flows.

That simplifies down to wanting low impedance (that is, lots of current can come out without changing the output voltage much) and high input impedance ( lots of volts come in, but almost no current gets eaten). That makes for the best possible signal voltage transfer.

i have some old school pedals and some new and they dont always seem to be working right together with volume drops and wahs sounding weird etc...........i mainly use in this order a  fuzz face neg grnd / 70s small stone / carl marting hot drive mains powered / boss dimension c / boss dm-2 delay or boss dd2 delay and a rangemaster pos grnd . [ very occasionally i put a whammy in front of the lot ]

Old fuzz faces have low input impedance. They seem to work well this way, it's part of the sound. The small stone is moderate input impedance and the FF is a high-ish output impedance. You're probably losing some signal there, especially since the SS is not a true bypass or buffered bypass unless it's been modified. I don't know about the Carl Martin, but the Boss stuff is probably good - high input, low output impedances.The rangemaster is moderate to low input impedance, low output impedance.

is there some way to measure impedance [ i have a simple dmm ] e.g. via pedal jacks and is there something i can do to make sure everything is going at optimum to ensure best tone a la eric johnson for example ? im wondering if boss pedals in between stuff as buffers or something of that ilk may help? even some info as to what this concept all means would be cool

The simplest way to measure impedance is to put a variable-resistance pot in front of the pedal, put in a signal small enough not to be distorted at the output, and measure the resistance on the pot that makes the output signal half as big as it was when the resistor was zero. The value of the resistor is then equal to the input impedance. That's hard to do with fuzzes, easier with non-distortion pedals.

[aron]

Check out the DIY FAQ in impedance. I was collecting info on this:

http://www.diystompboxes.com/wiki/index.php?title=DIY_FAQ#MEASUREMENTS

[bobster]

thanks very much for the detailed explanations guys , very informative....

will not sweat the impedance issue and maybe try a few different combinations and let my ears be the judge!
cheers - rob