Direct Box (DI) - Active or Passive?

Live sound reinforcement, running PA's and general amplifier/amplification questions and discussion.
Post Reply
User avatar
slejhamer
Guitarnoise Addict
Posts: 3351
Joined: November 14th, 2004, 6:08 am
Location: Out to lunch
Contact:

Direct Box (DI) - Active or Passive?

Post by slejhamer » February 21st, 2010, 5:45 pm

What are the pros/cons of active and passive DI boxes?

If connecting an acoustic/electric guitar to a mixer or PA, would you use active or passive?

What if connecting the line-out from an electric guitar amp?

Why are DI boxes with Jensen transformers so much more expensive?
"Everybody got to elevate from the norm."

gnease
Musically Insane
Posts: 5523
Joined: March 2nd, 2004, 10:38 am

Re: Direct Box (DI) - Active or Passive?

Post by gnease » February 23rd, 2010, 7:24 am

transformers cost more than the simplet electronics required for a basic DI -- especially good-performing, wideband audio transformer. I don't have an opinion on the Jensen transformer (no experience), but will mention that designs with transformers have two very big advantages: elimination of potential ground loops and shock hazards. should also mention that active designs can have transformers.

ground loop issues aside, pluses for active DIs are better impedance transformations (higher to guitar, esp important for passive pups) and the availability of EQ and modeling. some active DIs also include cab and mic emulation in order to sound more "live" in recording. this was a feature Line6 started with the POD products (pricey).

I would go for an active with a transformer.
-=tension & release=-

User avatar
slejhamer
Guitarnoise Addict
Posts: 3351
Joined: November 14th, 2004, 6:08 am
Location: Out to lunch
Contact:

Re: Direct Box (DI) - Active or Passive?

Post by slejhamer » February 23rd, 2010, 11:42 am

gnease wrote:designs with transformers have two very big advantages: elimination of potential ground loops and shock hazards. should also mention that active designs can have transformers.

...

I would go for an active with a transformer.

Thanks man. I'm looking at the Radial Pro48 (active), which seems to offer the best of both worlds. Quote from the manual:
Passive boxes have the advantage of providing isolation over typical DIs, which can reduce ground hum
and noise in systems. The Pro48 features an isolation transformer in the power supply to address this problem.
I was actually thinking about that one or its passive cousin, the ProDI, when I made the original post, so that helped steer me along the right path. 8)
"Everybody got to elevate from the norm."

User avatar
slejhamer
Guitarnoise Addict
Posts: 3351
Joined: November 14th, 2004, 6:08 am
Location: Out to lunch
Contact:

Re: Direct Box (DI) - Active or Passive?

Post by slejhamer » February 24th, 2010, 4:07 am

Wow, I just found out about another feature that some have - the ability to accept a speaker-level input.

So, the DBX DB12 for example, which is active with a transformer, can be put between the amp and speaker of a modeling amp and then run direct to a recorder or PA. With a parallel throughput, there's no additional load on the amp so it won't overheat; only the speaker is loading it. I read that someone on Talkbass has used one of these hooked up to their megawatt Ampeg bass amps, using the speaker out, with no problems. Very impressive!
"Everybody got to elevate from the norm."

gnease
Musically Insane
Posts: 5523
Joined: March 2nd, 2004, 10:38 am

Re: Direct Box (DI) - Active or Passive?

Post by gnease » February 24th, 2010, 9:11 am

electrically, a speaker tap (parallel connex) is actually a pretty simple and low cost feature to implement. a good idea that I'm surprised isn't more common.
-=tension & release=-

Post Reply