Input impedence required for hexaphonic pickups

jksuperstar

My idea is to break-out a hexaphonic pickup to 6 signals, put them into a 6-channel ADC, and get that info into a computer for processing. I already have a sound card I really like (Emu 1616m), so I'm just looking to expand on it.

So I've been looking at a few low-end converters, just something that does ADC conversion to ADAT lightpipe. Behringer ADA8000 for example. So, break out the 6 pickup signals, and send them into one of these devices. However, most have an input impedance of 100k at best. Not ideal for a pickup. Do the Roland GK-3 type pickups require a high impedance like 2.2M as seen on some gear? Or is 100 - 250K ok?

Not looking for tube tone or whatever (this is for bass), just clear reproduction of all available frequencies. Theory dictates the higher the impedance the better, but since that's not readily available, what's good enough?

DrJustice · Posted: Mon May 04, 2009 3:27 pm Post subject:

I have also been looking around info on the GK-3, but I can't really find anything about its innards. From a picture of the GK-KIT-GT3 here , it looks like there are opamp buffers for each string. The GK1 was buffered. I guess it stands to reason that there are line drivers in the 13-pin standard.

So probably a low'ish impedance...

DJ
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jksuperstar · Posted: Mon May 04, 2009 7:43 pm Post subject:

That would make life easier. I guess I'll just hook some spare wire to the 13-pin jack and see what happens on a few different inputs (high impedance Emu input, G2 line ins, etc.). I'll report back in a bit...

BobTheDog · Posted: Mon May 04, 2009 11:03 pm Post subject:

Well I am not sure about impedance but I do know the output levels are very low. You need a fair bit of amplification.

When I was using the 828mkii with pre-amps up full and the extra boost enabled I could get a pretty strong signal.

With the Konnekt48 the signals are pretty low and need amplification with software.

Also with the RMS pickups the dynamic range is much larger that normal pickups so a bit of compression helps, not sure about the GK in this respect.

Andy

jksuperstar · Posted: Tue May 05, 2009 6:03 am Post subject:

That's the exact problem I'm trying to avoid. With a microphone input, which is the lowest impedance, the signal will get lost quickly. When a signal is weak, like a guitar pickup, having a very high resistance means it doesn't take much current to get the signal higher. But there's this whole impedance matching game, so things get complicated quickly.

But, it sounds like it worked for you Wink

BobTheDog · Posted: Tue May 05, 2009 1:17 pm Post subject:

Also the RMC fanout box I have may well be amplifying the signal as it draws power either from the guitar or from a connected device like the VG99.