trying to wire/calibrate w/ recording studio equipment

Hello REW-ers,

I'm trying to set up REW. I want to make a calibration file for my soundcard (and simultaneously my preamp, keep reading). My setup is a bit different as I'm a recording studio but it's the same basic parts.

My setup:
Mac Pro quad 2.66 running 10.4.8
Lynx Aurora 16 converters ("soundcard"), it's the rack mount, NOT any of the computer cards.. it runs to the HD card
www.lynxstudio.com/product_detail.asp?i=1
Digidesign ProTools HD card in the actual tower
API 3124 mic pre
Avenson Omni mic

I have tried several things and cannot figure out how to wire this up to get any usable results. Issues:

-When calibrating the "soundcard", shouldn't I run it through the mic pre too since that has color as well? Or should the preamp be part of the "mic" calibration?

-Calibration for the mic is another step, correct?

-I tried running the "right" channel (#2) of the converter (soundcard) output into the "right" channel (#2) of the mic preamp (which is wired back to #2, the "right" input on the converter/soundcard) but only got a 'very low signal' warning, meaning it's wired wrong I think.

-Can I use the omni mic I've got (www.avensonaudio.com/sto2.php) or is an SPL meter necessary? Or both needed?

-Also, my converters run up to 192KHz but REW only lets 44.1/48 (actually only 44.1 for me, the other's grayed out). Does it make a noticeable difference in the accuracy?

Some basic possible wiring diagrams might answer all my questions. I just haven't found any that quite pertain to my gear.

Stephen Hudson
501.412.7115
www.thebusyboxstudio.com

PS. any time I can get it to work, it gives me a very scratchy graph that looks like the feedback loop here:
http://www.hometheatershack.com/room...tml#calmeasure
except it's not so even, it seems more like a "smiley" w/ the lowest part at 70Hz. Guess that could be the pre's color.
(wired through my mic pre, originally because I wanted to capture that color which I now guess belongs w/ the "mic" calibration... but later because I don't have a 1/4" to XLR adapter handy).

I have no clue why I'd be getting a feedback loop. The monitoring outputs should not be outputting anything coming into the input section. There is no where to change any setting for that though, least not that I know of.

[Wayne A. Pflughaupt]

I have tried several things and cannot figure out how to wire this up to get any usable results. Issues:

-When calibrating the "soundcard", shouldn't I run it through the mic pre too since that has color as well? Or should the preamp be part of the "mic" calibration?

-I tried running the "right" channel (#2) of the converter (soundcard) output into the "right" channel (#2) of the mic preamp (which is wired back to #2, the "right" input on the converter/soundcard) but only got a 'very low signal' warning, meaning it's wired wrong I think.

As noted in our REW Cabling and Connection Basics stickie thread, REW requires a sound card with a line in and line out connection. Mic inputs do not work because the signal level is too low - as you found out. Is there a 1/4" TRS input? If you use that with a unbalanced TS plug, the signal may be automatically boosted to compensate. I know a lot of mixing consoles are like this.

-Calibration for the mic is another step, correct?

Nope. REW cannot calibrate mics. You have to load a separate calibration file for the mic into the program. It's easy enough to create one, but you need to have a manufacturer's frequency response graph as a reference.

Some basic possible wiring diagrams might answer all my questions. I just haven't found any that quite pertain to my gear.

The link provided above has connection diagrams. You'll have to use whatever connections you have availible to conform the connections REW requires.

-Also, my converters run up to 192KHz but REW only lets 44.1/48 (actually only 44.1 for me, the other's grayed out). Does it make a noticeable difference in the accuracy?

Doesn't matter, since REW does its work using analog signals, generated from the line out of the sound card, through the sound system, and measured by the mic, back into the sound card.

Hope this helps.

Regards,
Wayne

Wayne,

I used a balanced 1/4" feed into the line in of the API pre (switched to line of course) so it's not a mic/line issue. And the mic pre shows plenty on the meters. Must be something wrong w/ the input routing in the software (?).

mic calibration:
Not too worried about it with this mic I guess. It's only off above 10K which isn't what I'm concerned with... http://www.avensonaudio.com/sto2.php

soundcard/preamp calibration:
So there's no calibration for the mic pre either (usually a behringer mixer for most right?) ? If that's working fine on a behringer I'm sure the API will do the trick .

44.1-192KHz
Yes, it's analog when it's outside the computer but it starts as digital at a certain sample rate and the measurement info is recorded in digital when it comes back in the computer. Guessing it's not a vital difference though.

katy, tx?
How far is that from Dallas?

Stephen Hudson
www.thebusyboxstudio.com

[brucek]

Mac Pro quad 2.66 running 10.4.8

REW requires OS 10.5 to operate properly. Version 10.4 will not work.

10.5 allows REW and other Java apps to access the inputs of an external sound card when it has been set as the default in the Sound preferences. In 10.4 the outputs of external sound cards can be accessed but the inputs cannot.

brucek

[brucek]

When calibrating the "soundcard", shouldn't I run it through the mic pre too since that has color as well? Or should the preamp be part of the "mic" calibration?

Normally, if using a mic preamp, you include the preamp in the soundcard calibration routine to offset its 'color' using the line-in and line-out ports and not including the mic stage of the unit. The mic stage will not effect the overall accuracy of the REW measurements enough to take concern.

brucek

brucek,

Excellent! I figured that pre should be accounted for. It's top end but it's famous for it's... color of course.

Always great to get the right missing details on a problem and I think I'll be fine once I get to leopard. Thanks!

stephen