Comments on: Everything You Ever Wanted To Know About Impedance (But Were Afraid To Ask)

By: djsinistral

djsinistral — Fri, 14 Aug 2009 22:01:14 +0000

“A DI box converts the low-impedance signal to a high-impedance and balances (grounds) the signal. It can then be plugged into a high-impedance input such as a mic preamp.”

I think you’ve got high and low the wrong way around.

By: Faizan

Faizan — Sun, 01 Mar 2009 10:47:34 +0000

I don’t get it. Instruments, mics and devices should have their impedances match, and the impedance never sums up like the speakers in series?

By: Mark Garrison

Mark Garrison — Sat, 31 Jan 2009 19:06:43 +0000

The 8 ohm rating on your guitar amp is a rating of the minimum load that should be applied to it, not its output. A would advise against plugging the amplifier’s output into anything other than speakers.

By: technosinner

technosinner — Fri, 30 Jan 2009 20:46:39 +0000

Extraordinary post!
A question: What about plugging amps to input devices throught the speaker output? Most guitar amps are 8ohm outputs to the cabs. Would plugging straight from there to an input device which is balanced be considered low to low?

By: Mark Garrison

Mark Garrison — Fri, 30 Jan 2009 04:18:05 +0000

The only reason not to use an active DI is that they require power. Most can run on phantom power, so it’s not a big deal, but if you’re running one on a battery it can be problematic if it runs out in the middle of a good take, or worse, the middle of a live performance. Other than that, active is a safe choice.

By: m4rkei

m4rkei — Wed, 28 Jan 2009 04:24:24 +0000

Is there any rules of thumb when choosing active over passive. is it advisable to always use active when you can?

By: Mark

Mark — Sun, 25 Jan 2009 03:04:13 +0000

An active DI will give you a bit more signal level, so it’s a good choice when you’re having trouble getting a hot enough signal.

By: m4rkei

m4rkei — Fri, 23 Jan 2009 02:55:33 +0000

Great article. Thanks a lot Mark. I do have one more question that I didnt see covered in the article. When would it be advisable to use Active DI opposed to Passive DI?

Thanks!

By: Mark Garrison

Mark Garrison — Tue, 20 Jan 2009 18:00:08 +0000

Thanks for the comments.

Clay: Yes, you are correct. Though, with modern equipment this is much less of an issue than it once was, to the point that most recording engineers I know don’t put that much thought into impedance matching. I chose to simplify for the sake of making the article accessible.

Gushchin: Plugging a high-impedance output directly into a low-impedance input will compromise signal level and tone. Over a long cable problems with interference can be an issue on a high-impedance line as well.

By: Gushchin Dmitry

Gushchin Dmitry — Tue, 20 Jan 2009 06:49:19 +0000

Mark, thank you for the clarification!

What are the drawbacks of connecting high impedance device in the low-impedance input?