Mic levels, instrument levels, preamps

Eleanor Fudd

Eleanor Fudd

Member
I have just acquired a combination mic preamp-compressor. Radial PreComp™ Channel Strip
I also ordered a mic preamp-EQ combo. Radial PreMax™ Channel Strip
The Pre/EQ unit has a switch to change the impedance to instrument level, but the Pre/Comp does not. Would a passive or active Direct Box take DI guitar level to the correct level for feeding the thing through the preamp without instrument level? Or, to put it in more general terms, can an instrument be fed into a mic preamp if the level is adjusted first?
Thanks for advice on this.
 
You're correct in that a DI box would be go between a guitar and a mic preamp.
I read that 1/4" inputs allow direct patching to the compressor, bypassing the preamp, so it seems that you could just put one unit in front of the other.

Instrument - into pre/eq - into comp bypassing pre.
 
Steenamaroo said:
You're correct in that a DI box would be go between a guitar and a mic preamp.
I read that 1/4" inputs allow direct patching to the compressor, bypassing the preamp, so it seems that you could just put one unit in front of the other.

Instrument - into pre/eq - into comp bypassing pre.
Click to expand...

Thanks, you make a good point. So, I could go to the Babyface mic input, compressed and preamped, or the BF instrument input, compressed: yes? That will be interesting to hear if there is an audible difference.
 
The baby face is your audio interface?
Whether you want to use microphone or instrument input, these devices (in your OP) would go in front of your interface, connecting to a line input.

Microphone or Instrument - Rack devices - line out to interface.
As the pre/eq has the instrument or mic input options, I'd put it first and use its line output to feed the next device's line input.

Microphone or instrument - XLR or 1/4" - Pre-eq - 1/4" - Compressor - 1/4" interface.

So the signal levels are either
instrument-line-line
or
mic-line-line.

I don't know the gear first hand but it looks like you could do that.
 
Steenamaroo said:
The baby face is your audio interface?
Whether you want to use microphone or instrument input, these devices (in your OP) would go in front of your interface, connecting to a line input.

Microphone or Instrument - Rack devices - line out to interface.
As the pre/eq has the instrument or mic input options, I'd put it first and use its line output to feed the next device's line input.

Microphone or instrument - XLR or 1/4" - Pre-eq - 1/4" - Compressor - 1/4" interface.

So the signal levels are either
instrument-line-line
or
mic-line-line.

I don't know the gear first hand but it looks like you could do that.
Click to expand...


I've posed the question badly. The Big Deal here for me is the understanding that one can run an instrument through a mic preamp simply by using a DI box to change the signal level. The preamp might not be designed for instrument sound, but one could experiment with any mic pre and a DI. As for my two modules, I'll experiment and see whether EQ-Comp or Comp-EQ gives better results.
 
I may have phrased the answer equally badly.

If you simply want an instrument input to go through your comp, your current gear offers a solution.
If you want to experiment with running an instrument through various mic preamps, a DI box is the solution.
 
You are correct- a DI is an impedance matching device to bring an instrument into a microphone level pre-amp.
 
Eleanor Fudd said:
I've posed the question badly. The Big Deal here for me is the understanding that one can run an instrument through a mic preamp simply by using a DI box to change the signal level. The preamp might not be designed for instrument sound, but one could experiment with any mic pre and a DI. As for my two modules, I'll experiment and see whether EQ-Comp or Comp-EQ gives better results.
Click to expand...

Err? Yes! There are two basic types of DI* box. Active and passive. The first, (aymex) requires power, battery, phantom or both. They have a very high input impedance of 1,000,000 Ohms which is the received wisdom load for passive guitars (it actually doesn't matter THAT much).The output impedance is generally low, sub 150 Ohms and balanced, usually, but not always by an audio transformer.

Passive types simply use a transformer and since 10:1 is about the highest practical ratio, these will rarely present much more than 150-200,000 (150-200k) Ohms to the guitar, seems low but again, rarely matters.

Both types almost always have a 'loop out' jack that can feed an amplifier whilst the signal also goes to the mic pre amp via an XLR connector. It is vital that both types have an 'earth/ground list' switch (but see 'Orchid') They both have pros and conns: Actives CAN be overloaded but not likely with a passive guitar. The cheaper versions (mention no names but it starts with B!) can be noisy.
Passive are very unlikely to be overloaded, cannot introduce noise (but both types can pickup hum) obviously 'quality' depends upon the transformer but then some folks like the 'grunge' of the very cheap ones!

*That is MY definition of a "DI box" High Z in, low Z, balanced out with about a 20dB attenuation. Other 1:1 types should, IMO be dubbed "isolation" boxes. Orchid Electronics are a UK company that make some very high quality DI, iso and re-amp kit at keen prices. They also do not fit GL switches but avoid ground loops in another, clever way.

Dave.
 
My general recommendation is an active di for passive pickups, because it won't load down the pickups and change the sound.

Some people use passive DIs with passive pickups with good results, but it really depends on the electronics in the specific guitar and the sound you expect to get.

If your guitar or bass have active pickups, it doesn't matter whether you use an active or passive di.
 
Farview said:
If your guitar or bass have active pickups, it doesn't matter whether you use an active or passive di.
Click to expand...
If you have active pickups, you don't need a DI. Plug it into a Line input and go. If for some reason you really want to run it through a mic pre, use a TS>XLR cable and plug into the mic input. If it's too loud for that, it's because it has its own preamp and doesn't need another. You can either turn the guitar or the preamp down, but if you didn't want distortion, why would you do this anyway?
 
ashcat_lt said:
If you have active pickups, you don't need a DI. Plug it into a Line input and go. If for some reason you really want to run it through a mic pre, use a TS>XLR cable and plug into the mic input. If it's too loud for that, it's because it has its own preamp and doesn't need another. You can either turn the guitar or the preamp down, but if you didn't want distortion, why would you do this anyway?
Click to expand...

This is true. A passive DI will lower the signal level, if it needs to be lowered.
 
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