Home Theater Forum and Systems banner

1 - 9 of 9 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter #1
Running Xd in 2.2 setup. I'm not sure about the settings with the output from the macbook pro. I have a PS Audio GCP-200 preamp balanced outputs to the NHT XdA amp.

So where does the line out (headphone) from the laptop go into the "processor?"

I tried to use the RCA input on the XdA and got this error message after setup when I tried to start taking measurements:

"Output level on the left reference input is very low. -71.7db FS, check that the loopback connection is in place and the left/right connections are not swapped."

I had set the left (with overall speakers) as the calibration test. The "right" line out from the two into one headphone output then went to just the one right into the XdA.

The instructions do not show this and the Xd example does not show connections just user photo and you can's see any connections.

Any help appreciated.
 

·
Registered
Joined
·
7,514 Posts
Assuming the Macbook has a line-out and a line-in port, you must start by calibrating the soundcard.

Connect a single loopback cable from the right line-out to the right line-in of the Macbook. The left channel will not be used at all for REW.

Create and save your soundcard calibration file so that REW is pointing to it. Then remove the loopback cable.

Now you will connect that calibrated right line-out channel of the Macbook to a CD or AUX input of your preamplifier and you will plug your SPL meter into the right line-in channel of the Macbook and run Check Levels, then run Calibrate, then run Measure.

brucek
 

·
Registered
Joined
·
5 Posts
Discussion Starter #3
Assuming the Macbook has a line-out and a line-in port, you must start by calibrating the soundcard.

Connect a single loopback cable from the right line-out to the right line-in of the Macbook. The left channel will not be used at all for REW.

Create and save your soundcard calibration file so that REW is pointing to it. Then remove the loopback cable.

Now you will connect that calibrated right line-out channel of the Macbook to a CD or AUX input of your preamplifier and you will plug your SPL meter into the right line-in channel of the Macbook and run Check Levels, then run Calibrate, then run Measure.

brucek
Thanks for your kind response. Had done the soundcard calibration and it came out great. Did the other setups but keep getting error messages on levels too low -49dbf and then another error message saying there is clipping.

So contradictory and confusing.

Will have to start all over and try again later. Maybe something is wrong with the cable from the Ratshack meter to the macbook pro but the calibration was easily within one of accuracy at 79db.

This ain't that easy. But thanks for the help. At least I have the connections right.
 

·
Registered
Joined
·
7,514 Posts
Did the other setups but keep getting error messages on levels too low -49dbf
If you did the soundcard cal and the line-in VU level was fine, but when you run Check Levels with the SPL meter connected it doesn't give you decent input levels, then the meter or cable or adapter is bad. If the line-in jack is stereo, I presume you are using an appropriate stereo to mono adapter to connect the SPL meter?

As a test, plug the SPL meter with its RCA cable directly into your preamps AUX input and sing. It's a mic, if it works......

brucek
 

·
Registered
Joined
·
5 Posts
Discussion Starter #5
Thanks for the additional insight. I'm going to examine each of these items. The levels with the SPL calibration actually looked fine and in line. But then the next step the levels have been coming up as far too short.

Will check on the quality of these connections again and the hardware too. Thank you again!
 

·
Registered
Joined
·
7,514 Posts
The levels with the SPL calibration actually looked fine and in line. But then the next step the levels have been coming up as far too short.
Ahh, key information. If the input VU level is fine when running the Check Levels routine and not fine when running a Measure, the reason is that the bandwidth of the Check Level pink noise and the Measured bandwidth are much different.

The Check Levels routine uses a band limited pink noise, either selectable subwoofer cal (30Hz-80Hz) or Speaker cal (500Hz-2000Hz). You must select the one that represent the range you are measuring. So, if you are measuring a sub from 0-200Hz, don't use the speaker cal or vise-versa...

brucek
 

·
Registered
Joined
·
5 Posts
Discussion Starter #7 (Edited)
Thanks again for the help and the notation on these numbers. Would never have knew that. Not in the documentation I can see.

Anyway, I did that but now I'm not clear on these three meters. The first one comes in right around 12 but I'm not sure what the other two are and where they are suppose to be when you click to lock in the check.

So I'm still getting the "low level" number -39 or something and followed by a clipping error which seems contradictory from the naive perspective.

Doing this with the RatShack meter on a tripod at 75db.

(Thought I had conquered this, but nope.)

It appears this will have to wait again. Appreciate the assistance.
 

·
Registered
Joined
·
7,514 Posts
The first one comes in right around 12 but I'm not sure what the other two are and where they are suppose to be when you click to lock in the check.
The "first" one, marked OUT is the RMS output level.

The "other two" are the left and right channel RMS input level. The right channel is to be set to ~-12dB using the Input Volume thumbwheel.

The red lines are the peak levels.

See the REW HELP files

Check Levels soundcard calibrate.jpg

brucek
 

·
Registered
Joined
·
5 Posts
Discussion Starter #9 (Edited)
Thanks for the point and graphic on this. That's where the the things have been going awry.
Think I'm going to replace the hardware for the input from the Rat Shack meter. Although the SPL is coming in accurately, I don't get the proper levels on the far right measurement at all. The (right) measure is always fluctuating far lower than what is needed.

So I'll get another part and start from scratch again.

Thanks much for all your assistance to a newbie in the audio measurement arena.

Since I don't have much room for moving around the system, I'm not that concerned. And having added a second bass module to the Xd system, it's been a real eye opener how much better the system can be.

Related equipment:

Lavry DA10 DAC
PS Audio GCP-200 Preamp
PS Audio Power Premier
Grand Prix Audio Monaco
 
1 - 9 of 9 Posts
Top