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Muppet_Dog
04-22-2002, 05:32 PM
I have a HHB Radius 10 (4 preamp block) that I would like to use to just record keyboards. they just have XLR imputs on the back. Do I have to go out and buy 4 DIs to do this or can I just get an XLR to 1/4 cable and just run them stright in? I never quite understood the whole DI thing and what it does differnt to a signal.
Thanks for any info,
Mark

Kev
04-23-2002, 01:24 AM
When recording synths the DI pre-amp combination can be as creative as chosing a Mic.

Identify why you want to use the HHB as a pre-amp for your synths and this may help to work out if you want an adapter lead or a Transformer DI etc.

More ... just ask but in the mean time check this

http://www.jensen-transformers.com/apps_sc.html

and look for the Musical Instrument Application Schematics and General Interfacing Application Schematics and DI's etc...

Muppet_Dog
04-23-2002, 10:09 AM
Those are just the only thing I can use quickly. So I just need to know what the differanc is in DI or direct.

AE
04-23-2002, 04:18 PM
You may be able to get away with going direct from your keys into the mic pre, but if the output impedance of the instrument is high, you'll have to deal witth attenuation and frequency response degredation; depends upon the particular product.

Muppet_Dog
04-25-2002, 11:39 AM
where is the best place to learn about how signals work?

Kev
04-25-2002, 02:00 PM
Originally posted by Muppet_Dog:
where is the best place to learn about how signals work?<font size="2" face="Verdana, Arial">Signals or the Interfacing of signals??

strange.

A Pre-amp provide preamplification for a low level signal to a high or standard level say 0dB or +4db.

If your synth is at 0dB it could be argued you don't need the Pre-amp.

Many would still use a Pre-amp for a synth so the question is why? Is this the direction you want to go? I don't want to bore everyone. images/icons/frown.gif

AE
04-26-2002, 08:01 AM
There are a few texts you might want to read. Anything by John Eargle is good. The "Audio Engineering Handbook" (Benson) and "Handbook for Sound Engineers" (Ballou) have tons of info. I haven't seen new versions of these for several years so I can't tell you how current they are (would make a difference in the digital audio chapters but not so much for anything else). If you want more, consider some type of academic program. There are numerous options available; AES publishes a handbook of educational programs that covers most of them.

Mark Haliday
04-28-2002, 01:33 PM
A simple explanation :

Once upon a time (that time we are desperatly trying to mimick with preamps such as the radius 10), one only connected microphones to recording consoles.
And since Mics output very low levels, at low impedances, traditional recording consoles accordingly had (and still have in most cases) their inputs adapted to this, which means they have high gain and low impedance inputs. So has the Radius 10.
Trouble is keyboards usually output at least "-10 db" consumer line level (sometimes up to pro +4 levels) and it is safe to assume they will want impedances of at least 10 kOhms

That is what the Di was invented for : adapting impedance and level of various sources to a standard microphone imput

To avoid this, an increasing number of preamps have line inputs or at least "instrument" inputs.

Unfortunatly it is not the case of the Radius, so will have to find a proper impedance adapter, passive (transformer) or Active DI box.

I admit it may sound insane to attenuate a loud signal so as to allow the console to amplify it again, but that is the way it goes.

Personally I have decided to do away with all that, and I plug my keyboards straight into a AD8000 (on which I recalibrated the inputs to allow that)
888 is more of a problem since you have to open it to change the gain from the factory setting (+4 db ref level + 18 db headroom !!).

Rich Breen
04-29-2002, 09:24 AM
Originally posted by Muppet_Dog:
I have a HHB Radius 10 (4 preamp block) that I would like to use to just record keyboards. they just have XLR imputs on the back. Do I have to go out and buy 4 DIs to do this or can I just get an XLR to 1/4 cable and just run them stright in? I never quite understood the whole DI thing and what it does differnt to a signal.
Thanks for any info,
Mark<font size="2" face="Verdana, Arial">Mark - It's more than a straight level-interfacing issue: In order to keep noise figures low, the input impedance of most mic pres is quite low - in the case of the Radius around 2k - this is a less than ideal load for a typical synth to drive, which results in higher distortion figures and possibly compromised frequency response. A DI presents a high impedance to the instrument (synths typically should be presented with around 10kohms, while a passive electric gtr pickup may want something as high as a few MegOhms), and drives the mic pre at a more ideal level.

If you *do* run your keys straight into the mic pre at least be certain that phantom power is off! If not, you risk frying the output stage of your synths.

best,
rich

Craig Woolard
04-30-2002, 09:14 PM
Now, THAT is a REPLY!! Thank you for your time and expertise.

Craig

Rich Breen
05-01-2002, 09:08 AM
Originally posted by 24-bit:
Here's some Impedance info.:

Impedance is one of audio's more confusing concepts. To
clarify this topic, I'll present a few questions and answers
about impedance...<font size="2" face="Verdana, Arial">Readers should know this is pulled from Art Munson's Tape.com (http://www.tape.com) website, and was written by the very knowledgeable Bruce Bartlett.

From Tape.com's web site: "Bruce Bartlett is the author of "Practical Recording Techniques*
2nd Ed." published by Focal Press.
Copyrighted 2000 by Cassette House. May not be reproduced in whole or part without permission."

Best,
rich

slangification
05-01-2002, 01:20 PM
Originally posted by Muppet_Dog:
where is the best place to learn about how signals work?<font size="2" face="Verdana, Arial">I don't know if it's the best place, but here's a place: http://www.tangible-technology.com/basics.html

Kev
05-01-2002, 01:57 PM
Tangible-technology is Eddie Ciletti.

Eddie is a very cool guy and his site sould be standard reading to all. I could also include John Klett's site in that standard reading list.