Stompbox output impedance?

[therecordingart]

I'm considering building this solid state amp:

http://store.qkits.com/moreinfo.cfm/FK660

I'd like to switch between a clean preamp and a Dr. Boogey or similar. My concern is the output impedance of the stompbox and the 15k input impedance of the amp circuit. 

How do I measure the output impedance of my stompbox circuits? Am I just over thinking this or am I setting myself up for some significant signal loss?

[R.G.]

Output impedance of pedals varies a lot. Some are quite low, others are high-ish. The high ones tend to be the ones which have a 100K or higher volume pot on the output, which makes the source impedance as much as 25K. But most will drive a 15K input with no significant losses.

[twabelljr]

From Craig Anderton's "Projects For Guitarists" on measuring amplifier or some other device's input impedance: "If the impedance is under 100k, I'd strongly recommend adding a preamp or buffer board between your guitar and amp or effect to eliminate dulling and signal loss." You've got it covered with the preamp. Sorry nothing on measuring output impedance, but it sounds like you will be fine.  












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[PRR]

Guitar-cord gear can be over 50K but usually under 500mV, often closer to 100mV (0.1V).

Driving 15K 1V inputs is just a step too far.

Even in HI-FI work, such a power amp would be preceded by a gain of 10 >100K "line amp" to ensure accepting "any" signal source. Such "hi-fi preamps" were usually tarted-up with tone controls and specialized phono preamps, but I have used a opamp and 9V battery.

For guitar with many/various pickups and processing, you might instead use switchable gain=30 gain=3 booster. At 30 you can play direct from axe or from weak pedals. Gain=3 won't have to be turned WAY down with hot sources.

Use 100K-250K Audio taper pot in front of this booster.