I have used the instrument input on various interfaces, and the DI box.
 
But, I am wondering what y'all use to record piezo pickups? 
 
Especially what THE CRAIG used to create/adjust the piezo amp.
 
Yeah, I know this post should sorta be in the techniques forum. Sorta.
 
 
 

The Piezo Amp is intended for those who feed their acoustic guitar piezo pickup into an audio interface's high-impedance direct input. Most acoustics with piezos have an onboard preamp, but don't do the EQ and notching that the amp offers. Some do have onboard EQ, like tone controls, but personally I'd bypass those or set them to flat, and use the Piezo Amp instead.
 
As I work about 300 feet from "the ultimate lending library for guitar players," I tested the amp with over a dozen different acoustic guitars with piezos, including a non-Gibson (but don't tell anyone about that one, okay?). 
 
I originally designed the amp for my beloved J-45, but made it more versatile prior to creating the version for the Membership program.

Thank you for your response.
 
I have wondered about the in-guitar EQ and amp changing the impedance of the output.
 
Over the last five years, what interfaces, in general, have you used/tested that you found acceptable?
 
 
 
 
 

If the piezo system has a powered preamp then the tone controls in the preamp shouldn't affect the preamp's output impedance at all.

If the instrument is plugged into a high impedance interface/amp input or a high impedance DI box then any effect on impedance the preamp causes will be minimised. Though in my opinion and experience most piezo systems require so much tone shaping and dynamics control that any effect a minor impedance mismatch causes is likely to be the last thing to worry about.

YouDontHasToCallMeJohnson
I have wondered about the in-guitar EQ and amp changing the impedance of the output.

 
TLW's response nailed it, nothing to add to that.
 

Over the last five years, what interfaces, in general, have you used/tested that you found acceptable?

 
Frankly, I haven't found any that are unacceptable. I do pay particular attention to crosstalk specs, though. I think that affects the "soundstage" considerably. But it seems no interface has everything - perfect drivers, superior response, low crosstalk, etc. Here's are some subjective thumbnail descriptions...
 
RME: Top of the line, if you have the bucks.
Lynx: See RME.
MOTU: Excellent drivers for the FireWire interfaces (haven't tested their USB stuff much).
Focusrite: You can't go wrong. Solid all-around interfaces.
Avid: The MBox line used to suck, so it's unfortunate that the excellent 3rd generation versions adopted the same name.
PreSonus: If you live in a PreSonus-based world, go all the way. I wouldn't say they're ne plus ultra cork-sniffer audiophile gear, but they offer flexibility and low latency.
Roland: Solid specs, with useful features like auto-level and a pretty developed applet.
Mackie: The company never really seemed to get traction in the market but the hardware is solid.
TASCAM: I am currently using the US-4x4 because I love the class-A mic pres; they're neutral without being sterile. The 2x2 and 4x4 are basic interfaces, but that's because TASCAM put the "bill of materials" bucks into the mic pres.
 
All of these have direct inputs suitable for instruments with high-impedance outputs.
 

Thank you for your response. A good list of options.
 
Just purchased a Tascam 16x08 to replace the fried EMU for one of the audio workstations.