Jumbo Sunshade - Ezine

 
DI's and Cabinet Simulation
 

It's great that amp modelers give us the easy option of running direct to the board for gigging and recording, but it's also very easy to go direct with an actual tube amplifier.

There are a few ways to do this, but the most popular with gigging musicians is to use a direct box that features cabinet simulation (aka "cab/speaker modeling" or "emulation").

What is cabinet modeling?  Generally speaking: speaker/cabinet simulation is nothing more than a filter that introduces an EQ curve approximating the voicing of a speaker cabinet.

The specifics of any particular setup would depend on what options that amplifier provides, and, how the player feels about them sonically (they all sound different; it's just a matter of personal preference).  For amps that don't have a preamp out (FX Send) or poweramp out (usually called Line Out), then the only option is putting the DI in-line with the Speaker Output, which is pretty much how most people do it regardless.

Here's what that rig looks like:

With this setup, the DI taps the amplifier's speaker output and that is where caution must be exercised.  There is a difference between a standard DI that features cabinet-modeling, and a DI that is also a "dummy load".  As with most tube amps, if you fire that thing up without a load (speakers) on the poweramp side, you're running the risk of a costly repair.  [Preamplifiers don't require any such load.]
Most people using this setup would have to make sure that the tube amplifier and the speaker cabinet are both connected to the DI before powering up.

Really, the biggest advantage here is that you don't have to setup a microphone on your cabinet for the front-of-house mix.  Your stage volume is still directly tied to your FOH volume; meaning that when you turn your amp up or down for the stage mix, you're also affecting your level in the mains (just like with a mic'd cabinet).

Three very popular DI's featuring cabinet simulation with various options are:

Behringer GI100 - $35

Hughes & Kettner RED BOX Classic - $120

 

 

Palmer PDI-09 - $179

 

Last year i borrowed a GI100 to use for a few live gigs and i thought it was just fine for the blues/rock material.  There was a slight hiss but i doubt anyone other than me noticed it.

 

Adjusting stage volume without affecting FOH volume:
For amplifiers that feature a Preamp Out (FX Send), this can be sent to the DI, which means any adjustment to your amp's Master Volume will have no affect on the rig's FOH volume.

[I do have some studio experience with sending the preamps of various high-end guitar heads (VHT, Bogner, Soldano, etc.) to various high-end DI's.  This never sounded better than using the amp's own poweramp section.  I mention it though because those preamps all sounded way different from one another and so live results would also vary.]

 

Eliminating the speaker cabinet altogether:
Again this depends on what the amp itself is capable of.  With my unmodified 70's Fender it can't be done.  But with my 90's VHT i have two options:
1. Preamp Out - send the signal from the preamp to the DI while also muting the poweramp.
2. Poweramp Out - this amp can be powered up without a speaker cabinet plugged in (no plug in the output = output shut down).  Even with the speaker outputs shut down, the Line Out (poweramp out) remains active.  [This amp is about 15 years old and so i would have to assume that other similar amplifiers have similar features.]

There is a third way to eliminate the cabinet which involves the use of a DI that also incorporates a "dummy load" for your tube amplifier.  It's kindof expensive and it's also outside the scope of this limited document, but i will say that it's cool as hell *and* you can use it with just about ANY amplifier from your 1978 Marshall JMP to your brand-spankin'-new Fuchs ODS.  [check out the Palmer PGA-04 and the Groove Tubes SEII]

 

Using a cabinet-simulating DI with a standalone preamp:
If you've got a stand-alone FX/preamp that you like then you're in luck because all the options are on the table for you on the stage and in the studio.

1. You can send the preamp directly into the DI and then use the lo-Z out for stage and/or recording (this method does limit your on-stage monitor options depending on how many Auxes your mixer has).  Obviously here you've eliminated your speaker cabinet.
2. You can take the DI's parallel out and send it to a power amp and speaker cabinet for your stage mix (or recording).
3. When using a power amp and speaker cabinet, you can also tap the poweramp's speaker output just like most other people do.

About two years ago i saw a guy using a Tech 21 rackmount preamp and a Behringer GI100.  His sound was pretty good.
Last year i heard a guy doing Robin Trower and Frank Marino covers: he was getting incredible tone with the GI100, an Art Tube MP, and an early 80's ADA MP-1!

 

Cabinet modeling versus speaker distortion:

For the DI's i mentioned above; cabinet simulation is not made to replicate the nature of a speaker's own distortion.  Many guitar speakers are specifically made to break up with higher volume.  Some players who are just getting into this might not understand how integral that whole low-wattage Celestion 4x12 cabinet thing is to a guitar rig's sound.

 

Any questions?...

* How realistic is speaker simulation; does it really sound like an actual speaker?
* Does a cabinet model sound as good as a real speaker cabinet?
* What's better; the cab sim in an amp modeler, or the cab sim in a DI?
* What's better for recording; a cab sim or a real cabinet?

Depending on the gear and the player, results will always vary.  I didn't have a chance to plug my borrowed Behringer GI100 DI into a mixer in the studio; but for the three gigs i used it live, it sounded "real" enough for me.  On one night, two of my guitar player friends kept forgetting i was using it.

Any cabinet might sound better or worse to different musicians depending on their tastes, their gear, and their style.
In the 20-something years that i've been doing this live and in the studio, i have heard speaker cabinets that sounded worse than the speaker sims in the Line 6 POD and the Behringer V-Amp.
I could easily imagine a situation where a speaker-simulating DI might sound 'better' (for whatever reason) through a PA than a microphone in front of a real speaker.

I can't directly compare the Behringer GI100's cabinet modeling to the Behringer V-Amp's cab modeling because with the GI100 i was using an actual amplifier and so the tone was completely different than what i'm used to either with the V-Amp/DI or with the VHT/microphone setups.
Clearly there is an operational advantage to using a DI versus using an amp modeler (speaking specifically about the V-Amp, POD, POD XT and POD X3 here).

For recording:
For me personally the decision to use a speaker/cab sim over using a real speaker/cab only happens when i'm pressed for time or being lazy and only when i'm also already using the amp modeler.  To my ears speaker modeling leaves much to be desired in comparison to real speakers (in a studio), let alone the way real speakers react to certain amps at high volume.
But i'm not arrogant or unrealistic though: i have heard many many reamped recordings that sounded as good as or better than recordings where the most expensive amps, microphones and rackmount gear were involved.
[Any producers, recording or mastering engineers who happen to read this will immediately start to blame each other.]
I mean i would certainly not discourage anyone from using a cabinet-modeling DI to record direct versus putting a mic in front of a cabinet.

 

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