Low Z guitar pickups need a buffer: Impedance question.

Hi. I want an active pickup that isn't made, so I've hired a guy to make some Low Z pickups for me which will be followed by a buffer of some sort. (active pickups in 2 stages)

I found this schematic - http://www.till.com/articles/GuitarPreamp/ - but I believe it's for standard High Z pickups with a DCR of ~10k.
My pickup guy advises that the DCR of the Low Z pickups he makes range from 5Ω - 50Ω.

Will the above schematic work if I find a more suitable R1 value? How do I determine that value?

Thanks in advance!

You need a circuit that's optimized for low Z sources. You can find ULN opamps that are quoted as 1.0 nV/square root Hz or less. they are expensive.
You may use a similar booster as the one here but you need a 2SK170 FET, and you will need to increase the gain, by putting an RC circuit across the source resistor.
But if the impedance is really as low as 5 ohms, there is no other solution than installing step-up transformers, similar to the ones used in HiFi for moving-coil phono cartridges - very expensive! That's what Les Paul did in is Recording model.

I used this general common base circuit for some low z (~50 and 80 ohms DCR) pickups I made, and it worked ok with a little tweaking of component values.

http://www3.telus.net/chemelec/Projects/Spkr-Mic/Spkr-mic.htm

I used the other circuit you posted using a 2SK170 FET for a piezo pickup.

Thanks for the replies guys - still a few noob questions if you don't mind...

I realize now I said "buffering amp" loosely without fully understanding what I was saying - am I looking for a VOLTAGE or CURRENT buffer?

abbey road..
1:If the pickups' impedances are high enough to accept a buffering amp, you advise an RC across the "source resistor" - are you referring to the pickup coil as the source resistor? If so, how do I determine the R&C values?

2:If the impedances are too low & I must use transformers, which transformers? I would assume it's secondary should have a DCR similar to a High Z pickup - 10Kish - so the impedance will look right to my guitar amp, no? If so, then what should I look for in a primary?

crazydoc..
That schematic looks pretty simple. The speaker coil is replaced with pickup coil, right? Then C1 is determined by my guitar amp?
1:Which component is adjusted based on my coil DCR? The 3M3? And I can just trim it to the specified 4.5V drop and that's it? Or am I missing something?
2:How do I determine a value for C1?

Really, thanks so much for the help, guys!

I think the central question is, why do you want a Low-Z PU and what do you want to do with it?

With that question in mind you should spec your PU according to your application and maybe need not any preamp or buffer electronics at all. Or if you do, you can spec your PU so the electronic part is easy and inexpensive.

A super-low-Z PU will be more problematic than a 200 ohm-ish PU or a medium-Z source. For instance, with a 200 ohm source you could use a mic step-up transformer for regular hi-Z output.