Do I need a Zbox with a MOTU 4pre?

[oldecuriosity]

Subject says it all . . . I'm assuming the answer is no since the 4pre has Hi-Z inputs, but since I rarely record electric guitar, I figured I would ask the experts first. Any advice/information would be much appreciated. Thanks in advance.

[Phil O]

I'm no expert, but my understanding is that the "guitar" inputs on the 4 pre are the appropriate input impedance for guitar (I mean, why else would they label them guitar right?) I don't know what's in the Zbox and it seems MOTU likes to keep the specs a mystery. It's a passive device which I'm guessing is transformer based. Anyway, I'm pretty sure the Zbox won't buy you anything over the 4pre.

Phil

[mikehalloran]

The Zbox is a DI but with some resistors and diodes to better emulate the "feel" of plugging into an amp — or that's the intent, anyway. Here's the SOS review:

https://www.soundonsound.com/reviews/mo ... -corrector

I notice that everyone charges list new and that used/demo/open box is only a few $ less.

I'd like it better if it had an XLR out in addition to the 1/4".

[Phil O]

Thanks for that link, Mike. You always come though!
Resistors and diodes, huh?
Not exactly a DI, and notice (according to the author of this article) that the instructions say to plug it into the high impedance input of your interface:"...but in the studio you'd plug it directly into the high-impedance instrument (not line) input of an audio interface." So if you don't have a high impedance input on your interface, you'll probably want a conventional DI.

There's also this:
"...which is designed to emulate the impedance of a dual-input amp (probably a Fender Twin)."
From a Fender Twin owner's manual:
Input 1, both channels: 1M ohms.
Input 2, both channels: 136k ohms.

And this:
"Measuring the input impedance of the ZBox while it's disconnected from the audio interface shows the high-impedance input to be in the order of 300kΩ and the low-impedance one about half that." He should have measured it connected. This will have some impact on the overall input impedance but without a schematic it's impossible to know how much. As for the Fender emulation, it looks like the low impedance input is close to Fender's Input 2, but the high impedance input seriously missed the mark.

"This is achieved using a network of resistors, but the design also includes a chain of diodes that goes some way towards simulating the way in which a valve-preamp stage reacts to signal level. The diodes are arranged so that they can't cause clipping at normal pickup output levels, so their effect is mainly on the input impedance, which will reduce as the input signal level increases." I'm guessing a tube guitar amp's input impedance shouldn't significantly change with input level if the circuit is designed well. I'm thinking the diodes are for effect and not meant as an emulation. (speculation on my part )

"There are no capacitors, as the guitar cable provides the necessary capacitance, but for use with a radio transmitter (where you don't have a long cable) a switchable cable-emulation capacitor would have made the impedance match more accurate." Canare GS-6 cable has a specified nominal capacitace of 160 pf/m. For a 15 foot cable that works out to be roughly 732 pf. A typical tone control on a guitar can introduce a capacitive load in the .047 microfarad range (depending on the pickup/controls configuration). That's about 64 times the cable's capacitance which means turning your tone control a small fraction of a turn will be equivalent to the effect of cable load. I don't think a switchable cable-emulation capacitor would do diddly squat.

So I think what I've gathered from this article is that first, the author isn't exactly an expert, and that the Zbox may be a good tone changer for those who like its sound, but it definitely does not qualify as a DI. My advice to the OP remains the same. Use the guitar input on your 4Pre...unless, of course, you like the tone of a Zbox.

Phil

[oldecuriosity]

Thanks, Phil and Mike . . . I've been following your posts for years, so always appreciate your advice.

Both of your replies mirror my gut sense - the Zbox isn't necessary with the 4pre, though it may improve the tone and overall "feel" while playing. The $40 price tag is low enough to give it a try, though when in doubt I prefer to add fewer things to the signal change not more. I'll continue to mull it over for another day or two . . .

Thanks again!

[mikehalloran]

If you don't think it makes much of an improvement, these usually sell on eBay for almost what they go for new. Catch and release won't cost much if you go that route.

[Phil O]

Catch and release. I like that. Yeah, thats's a good one. I'm gonna steal that phrase.