How to do a pre shootout, need advice.

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matta

Well-known member
Joined
Jan 11, 2005
Messages
1,640
Location
Cape Town, South Africa
Guys,

I?m needing some help here.

On the 29th of August I will be getting together with some engineers to do a
?shoot out? with some mic pres we pooled together. We have confirmed a couple
details and secured some good converters (a DAC1 and Apogee), will be using a
Rode NT200 in Omni as a test mic (this mic is quite popular in
semi-pro/home studio?s here in SA) going direct to a DAW.

A couple pres confirmed include: Mackie VLZ, Behringer Ultragain, Focusrite
Green, Millennia HV-3, Telefunken V672 and my own DIY Peter C Greens. I am
hoping to also include some Avalon and Summit pieces. If possible I?ll try
and make the recordings available to those who are interested.

It was suggested by one of the engineers to use pink noise to set the the
gain stages of all the pre?s prior to the session, which I think is a good
calibration test, agree?

The stumbling block right now is the consistency of the tracks being recorded.
In order to do a proper A/B we need the source to be spilt into each pre and
record that output direct.

Now where I need help is what is the best way to do this? How do I use a
single mic and then spilt it?s output into the various pres? I thought of
just making a cable splitter but then thought this will/would run into
impedance issues? Any advice?

Thanks

Matt
 
A good quality mic splitter (or a few) would be handy.

These are just transfomers with multiple primaries / secondaries.

Lundahl makes the transformers for a splitter - I have a couple of them.


You are correct about the impedance issue - you can't just use a Y-cable!

If you can't get a splitter, another (not so good) alternative is to use a matched pair of condensers, position them very carefully and record them together into two different preamps - this only allows you to compare two though.
 
I would not split the microphone signal since this isn´t the realworld load for the pres. I´d suggest to record something on CD and replay it via speaker to every mike-pre combination. This way you have always the exact same source (sound, volume, phrasing,..) for all your pres.

I´m really hot for this shootout. Great idea
:thumb:

Jens
 
[quote author="matta"]It was suggested by one of the engineers to use pink noise to set the the gain stages of all the pre?s prior to the session, which I think is a good calibration test, agree?[/quote]

Not really. Pink noise fluctuates in level enough that you really can't get closer than a 1dB match between preamps, and for an honest shootout that's not close enough -- 0.1dB is more like it.

What I've done is to set up a microphone in a room with a speaker and play 440Hz tone through the speaker. Then I get out -- go into the room where the preamps are, and switch the mic cable from one preamp to the other while watching the screen of the computer for level. I use a DAW program with a numeric readout for maximum level, n-track studio.

The reason you need to be in a different room is that your body moving around the room will change the level of the signal at the microphone slightly. Not an issue for real music, but it plays hob with test tones.

Then there's the issue of repeatability. Anyone in your crowd own a Yamaha Reproducing Piano? If not, I'd find a couple of musicians who are capable of playing things over and over again with very little change between takes. Studio session people, for example. Maybe a drummer and an acoustic guitarist?

I would not try doing a split; as other posters have suggested, this provides unnatural loading for the microphone, an extra transformer to color the sound through both preamps, and the possibility of interactions between the different preamp inputs.

One other possibility: play back a DI'd electric guitar track through an amplifier, several times. The drawback, of course, is that there will be no low or very high frequencies, and those are places where preamps differ a lot. But it'll tell you something about the mids.

Peace,
Paul
 
Hey Guys,

Thanks for all your comments and feedback. I've def. learnt alot and hope to
be able to put it into practise at the shootout.

Rodabod: I think the transformers are out in this case as I don't have the
resources to go out and get some right now, plus they might color things a
bit.

Jensenmann: I like the idea of the speaker and mic, less setup-time required
and produces consistent results, prob the not the MOST accurate way of doing
it but I think one that will allow for a more than reasonable test.

Pstamler, thanks for the heads up on the pink noise. This is all quite new
to me and it was just suggested so I am most grateful for your alternative.

On a side, N-track studio brings back memories for me! It was my first DAW,
using an old SoundBlaster, a crappy old Ross mixer I got at a boot sale
(noisy and dusty as heck) and my first REAL mic, an AKG C3000, those bits
started it all.

I'll be playing acoustic guitar and can faithfully repeat a line so I'm not
as worried with guitar. The issue is the vocals, a slight difference in
timbre can alter the results.

I have thought of a possible solution and thank might be to come up with a
guitar line and vocal to go on top of it, along with a female harmony part
and then track them prior to the shootout and put them onto a CD and load
them into the DAW and play those tracks though a speaker, recording the
output, but having calibrated them with the 440Hz tone.

Thanks again, any more comments would be much appreciated.

Cheers

Matt
 
[quote author="pstamler"]Then there's the issue of repeatability. Anyone in your crowd own a Yamaha Reproducing Piano? Peace,
Paul[/quote]

Poul this is excellent advice..we have use the yamaha Diskclavir very often..work very well for this..*S*

Kind regards

Peter
 
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