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Preamp/DI Questions Multi-Channel Preamps
Old 6th September 2007
  #1
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Preamp/DI Questions

In addition to tradition instruments, I use a sampler, sound modules & drum machines. I'm OK for now with pres for instruments/mics. But for the sampler, sound modules & drum machines...

I know how subjective these things are, but generally, are good DI units better than the line & Hi Z inputs on preamps? I'm working with a Focusrite 428, ART Digital MPA & BLA modded 002 Rack, if that helps. Would I do better with DI units like the REDDI, AU 610, Avalon U5, ect?

Secondly, do the line & Hi Z inputs take advantage of the same "circuitry" as the mic inputs on preamps, generally? Or are those inputs sort of like DI add-ons?
Old 6th September 2007
  #2
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Most mic pre/DIs, the DI input by-passes the input transformer. ( if it's transformer based). Some DI input on pres sound good, some don't. I don't know if the 428 DI passes thru transformers or not. For instance, I like the sound of the DI on the OSA L-3, but I like the sound of my WhirlWind HotBox DI ( solid state) into the mic pre input of the L-3 better. The Ditto DI I have ( transformer/tubes), seems to make the signal " too big" due to the "big" Lundhal input transformer in the L-3! The HotBox makes it just right..( IMHO)..Good luck....
Old 6th September 2007
  #3
Dan
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the DI on the 428 bypasses the input tranny, and goes directly into the op-amp. It sounds pretty clean, and good. It really depends on what you're going for, but it's typically a small change, and depends on how your gear reacts to different input impedances.
Old 7th September 2007
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Thanks fellas!

Quote:
Originally Posted by Dan View Post
the DI on the 428 bypasses the input tranny, and goes directly into the op-amp.
To clarify, when you say DI, are you referring to just the Hi Z inputs or the line inputs as well?

Quote:
Originally Posted by Dan View Post
It sounds pretty clean, and good. It really depends on what you're going for, but it's typically a small change, and depends on how your gear reacts to different input impedances.
Yeah, they sound good to me, but I'm only comparing them to a Digimax LT I had and pre-modded 002 Rack.




While I have some attention, I have a few other questions.

Is there anything inherently wrong with going through 2 DIs? For example: Marshall JMP-1 or SansAmp RBI->line input on 428->002 Rack input. Sounds decent to my untrained ear, but I'm wondering if I'm introducing problems of some sort going through 2 DIs.

Lastly, can DI units accept balanced inputs? I want to try the REDDI, but I'd want to also have the tonal options of the RBI. The output on the RBI(and the REDDI I believe) is balanced. Would there be a problem going into the unbalanced input of the other? Is a balanced to unbalanced cable the solution?
Old 10th September 2007
  #5
Dan
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a standard "DI box" is basically a transformer that takes a high impedance input (always unbalanced, and typically referred to "instrument level") , and converts it to a low impedance mic level signal. "DI" stands for Direct Injection

My understanding is that this is taken from most equipment running at high impedance internally, but having a transformer stage on the input (and output) to interface with other equipment. It provides balancing, and buffers the amplifying stage from different impedances it might see from all the different equipment it might be connected to. The "Direct Inject" bypasses this transformer stage, and goes directly to the amplifying stage. Not all "DI" inputs are true DI inputs though. something to be aware of.

So it's a little confusing to call a "DI box" by it's name, because you're not actually direct injecting, but it does perform a similar function to a "DI input." (as far as accepting hi impedance outputs.)


The REDDI muddies the water even further by being named a "DI" but I believe it also has an amplifier in it, and a line level out. I've only come across it in passing, so I'm not sure.

I'm not a guitarist, and am not familiar with the JMP-1, or the Sans-amp box. I use the plug for sans-amp. If I remember correctly , JMP-1 is a pre-amp, and I think the Sans-Amp is also. If they have instrument outs, I guess you could use them both, or if 1 has a line in, you would put that second. In the former example example you might be raising your noise floor some. If they don't have instrument outs, and you're hooking a line level out to an instrument input, it's not working as designed.
Old 10th September 2007
  #6
Dan
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huh, instrument level... the red headed step child of audio. Why can't they just put transformers on guitars?
Old 11th September 2007
  #7
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Thanks Dan!
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