# iMac Line in connection



## Roland Gama (Apr 19, 2008)

Has anyone been successful using REW with the 17"imac?
Though it has a line-in at the rear it supports only "sound studio" software.
Hope there are some imac users out there?


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## mrsollars (Apr 17, 2008)

i'm in the exact same boat......but a 24'' imac. 

thanks
matt


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## JohnM (Apr 11, 2006)

Can't think of a reason it shouldn't work. As long as you can select the line in and line/speaker out as the defaults in the Mac's system audio settings REW should be able to use them.


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## Roland Gama (Apr 19, 2008)

Hello John,
Tried for some time yesterday with the audio settings of the imac. All it says is that line out is not supported. I had faced this problem about a year back when I tried to get the TV audio signals in the imac and use it to feed a small 5.1 system.((Although the itunes, etc worked well.)
I phoned apple for support.
Reply: The line in works only if used with a software like "Sound Studio"
I installed sound studio and it worked but I could not use any controls of itunes eg. equalizer.
Sound Studio has a tab which you can tick and it sends the line in signal to line out straight through.

So yesterday as I said I tried using REW with sound studio support.
It works in as much as accepting the spl meter signals and spl calibration.
The rest does not work.ie. The sound card cant be calibrated.(It shows a very large dip below 100 Hertz.) The left channel cant be looped back.
The sweep works with all its function filters etc. However, accuracy is questionable.

Secondly I decided to purchase the DEQ2496 to use with REW. I found a calculator to convert BW to Q. Here is the link.http://www.sengpielaudio.com/calculator-bandwidth.htm
What do you think about it John?


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## Roland Gama (Apr 19, 2008)

Need further investigation on Griffin's iMic. It should work as you can set the line-in and line-out in the audio preferences.


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## JohnM (Apr 11, 2006)

Regarding the calculator, unfortunately Behringer are rather inconsistent in their definitions of bandwidth, y0u would need to connect the unit in a loopback and measure some filters at various bandwidth settings to see whether the DEQ corresponds to the FBQ2496 definitions, the DSP1124P or something else.


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## Guest (May 2, 2008)

Hi Roland,

I have a recent model iMac and will be starting to play around with REW soon. I'll let you know if I can figure out what the problem is. Have you tried using Apple's own GarageBand recording application which is bundled with most Macs?

Another possibility might be a free software program (we like those!) called Line-In which allows direct playthru from your input.

For reference, here are the stated specifications of the iMac's analog audio input/outputs. I believe they are the same as all other Macs, so there shouldn't be any model-specific limitation as far as I can see. 



> Line input
> 
> The analog line input operates independently from all other audio input ports and is always available. The line input supports recording at bit depths of 16, 20, or 24 bits per sample and at sample rates of 44.1 kHz, 48 kHz, or 96 kHz. Audio recorded from the line input is presented as a stereo data stream. The line input gain can be adjusted from -16 dB to +30 dB.
> 
> ...


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## Roland Gama (Apr 19, 2008)

Thanks Stretch.
The information is comprehensive. I have already downloaded Line-in and will give it a try.
Very few mac users this side of the globe-probably less than 1%. this too being very optimistic.

Do let us know how you progress.


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## Roland Gama (Apr 19, 2008)

Hello Stretch!!!

The Line- in free software worked. I sucessfully calibrated the imac's sound card. Flat as a straight line.
Feeling happy with the great achievement.Thanks a lot mate for saving my time and money had I purchased the "imic".
Will do some measuring tomorrow.


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## Guest (May 3, 2008)

Happy I could help. And thanks for saving me from banging my own head against the wall over this! Please let me know how you get on. Judging by previous posts, there's been some frustration from Mac users trying to get REW up and running, so if we can figure it out I'll write up a short primer and maybe the mods can sticky it for posterity.

PS: Are you running Leopard, or an earlier version of OS X? Apple just recently added support for Java SE 6, which may help matters. I seem to recall JohnM mentioning there were some issues with Midi communication on the Mac under SE 5.


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## Guest (May 3, 2008)

Also, could you possibly post your calibration graph, Roland? I spent a half hour today fiddling with the Audio Midi on the iMac and could not get a decent measurement, as you can see below.










I then hooked up an external audio interface I have with far better results.










So I'm very curious how you got the iMac's onboard audio set up in the end.

Thanks.


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## Guest (May 3, 2008)

Well I'll be a monkey's uncle. Came back, reset everything to defaults and immediately got a clean measurement on the internal sound card _without_ using the Line-In application. iMac is in red vs. external interface in black. Pleased, but puzzled. :scratch:










At any rate, here are the iMac audio settings that worked for me.

Input:










Output:










Time for a beer, I think.


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## Roland Gama (Apr 19, 2008)

Hello Stretch,
Some of my observation with REW are as follows:
When REW does not respond as you expect it to then quit it and restart. 
The comb filter like reading you have in the soundcard calibration is because you set the speed higher than 44.1Khz. John has mentioned this somewhere about macs.
The Line in freeware is always working unless you uninstall it.
Your last graph with the soundcard is similar to mine except than mine has greater peaks and dips before 20khz.
I feel you are in the right track. Have you done a soundcard calibration file?
(By the way, I am neither a computer geek nor an audio engineer but a dentist.)
I have printed the whole lot of help files and keep reading it during my spare time.
Yesterday I got to Impulse response.


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## Roland Gama (Apr 19, 2008)

Yes I am running leopard. Will check the java SE6.
Thanks!


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## htguy (May 14, 2008)

Hello. I am the guy that can't get the M-Audio firewire solo working properly on either an ibook g4 running 10.4.10, or an imac running 10.5.2. I preferred to use the ibook because I can put it in the room with the speakers. My imac is in the next room. If REW works on the imac, I'll just get some longer cables. I already have the radio shack analog meter. I noticed that the ports on the imac are 1/8". So, I need an adapter to go from the RCA port on the meter to the 1/8" port on the imac? Is there such a thing? Also, for the loopback for the soundcard calibration, I connect the two 1/8th ports with a cable? Thanks.


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## brucek (Apr 11, 2006)

> I need an adapter to go from the RCA port on the meter to the 1/8" port


From the REW Connections and Cabling thread, you require splitting out the stereo 1/8" (3.5mm) jack with one of these:










or you can use a ready made cable and use one RCA lead only:










brucek


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## htguy (May 14, 2008)

I am trying to use REW for the first time. I am using an imac, running 10.5.2. I connected a loop from the headphone jack out to the mic in. I also loaded the line in software. I did calibrations using the left and right channel. I have changed every setting I can and nothing gives a good calibration. They all come out very similar to this one. I must be missing one little thing that is causing the problem. Any suggestions? I would really like to get this working. Thanks


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## JohnM (Apr 11, 2006)

What did you use to connect the headphone out to the line in? If it is a 1/8 to 1/8 cable make sure it has stereo plugs each end. 

Line In is, as far as I can see, a monitoring application that allows the line input to be routed directly to the audio output. That is NOT what is needed for REW (or any other audio measurment application), I would not recommend installing Line In.

Are your audio device settings as shown in Stretch's post above?


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## htguy (May 14, 2008)

I am using 1/8" stereo plugs
I trashed Line In.
For the settings, instead of Built-in Input, and Built-in Output, I have Built-in Audio for both. I don't have Built-in 
Input or Built-in Output as options.
For Source, under Audio Output, instead of Headphone, I have Line Out. Headphone is not an option.
Under Audio Input, for the channel volume, I can only move the master. The slider for 1 and 2 are greyed out. 
Also, I have Audio Input and Audio Output showing on one screen. He has an Input not support, and an Output not support screen. Something is obviously really different with his setup.
How can I match his settings?


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## JohnM (Apr 11, 2006)

Settings sound like they should be OK, post a screenshot to be certain. You can check the input and output work by connecting the output to your system and playing some music and connecting an SPL meter to the input and seeing if the input level changes when you speak into the SPL meter. If those work then the problem is with the loopback connection.


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## htguy (May 14, 2008)

Here is the screenshot. I tested the input and output, and they both work. Any help with the loopback? Maybe the "line-in" program helps somehow with this?


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## JohnM (Apr 11, 2006)

The Line In program creates an internal software loopback, it won't help in this case. The settings look OK and as the input and output are working that leaves either your loopback cable or the input and output selection in REW, which both need to be set to default.


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## htguy (May 14, 2008)

JohnM said:


> The Line In program creates an internal software loopback, it won't help in this case. The settings look OK and as the input and output are working that leaves either your loopback cable or the input and output selection in REW, which both need to be set to default.


I switched the cable, and still get the same problem. I have input and output selections in REW both set to default. I still get the bad calibration.:gah:


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## JohnM (Apr 11, 2006)

Try selecting 2-ch 16 bit instead of 2-ch 24 bit for the input and output format.

Are you able to get output from the REW signal generator through your system? i.e. connect the iMac output to your system and start the REW signal generator with Pink Noise selected, full range, level -20dBFS.


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## Guest (May 25, 2008)

I'm stumped. You seem to have all the right defaults set, although you are running a slightly earlier version of Audio Midi Setup than I am. 

I will say, John, that REW will _not_ work on my iMac without the Line In software loopback active. I have tested that several times.


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## htguy (May 14, 2008)

Changing to 16 bit did not help. I am getting output pink noise to my speakers.

Strech: What settings did you use for the Line-in program. I believe my imac is second gen. 1.8 ghz.


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## JohnM (Apr 11, 2006)

Stretch, doesn't that contradict what you found in post 12 above? The description of what Line In does is to create an internal loopback, that would be a bad thing.


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## JohnM (Apr 11, 2006)

David, how did you verify that the input works OK previously, where were you able to see input levels?


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## htguy (May 14, 2008)

JohnM said:


> David, how did you verify that the input works OK previously, where were you able to see input levels?


I could see the input meter move up. I also connected an external mic to REW and spoke into it. I could see the meter move as I spoke.


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## JohnM (Apr 11, 2006)

Is the input a line input or a mic input, or does it handle both? If the output works and the input works then all should be OK. Can you post a screenshot of the result of the soundcard cal with the vertical scale zoomed out enough to show the whole plot? Also include a screenshot of the scope tab after the soundcard measurement.


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## htguy (May 14, 2008)

JohnM said:


> Is the input a line input or a mic input, or does it handle both? If the output works and the input works then all should be OK. Can you post a screenshot of the result of the soundcard cal with the vertical scale zoomed out enough to show the whole plot? Also include a screenshot of the scope tab after the soundcard measurement.



The computer physically has one input port. I can select in Preferences; Sound, whether a mic or a line input is selected.
The measurement and the scope graphs are posted. I did not want to compress the scope graph too much, so I saved it as two graphs. Thanks, and happy Memorial Day.


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## JohnM (Apr 11, 2006)

Do you have is set as a line input? Looks like you are getting very severe clipping, it needs to be set as a line input.


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## playitbyearmusic (May 17, 2008)

Sup Room,
I'm having the same problem that "htguy" is having. I keep getting the same results he has on his screenshot above. I have a MOTU 828 MK1. I connect the Analog 1 out to the Analog 1 in. In my Audio/Midi preferences, "in" says MOTU 828 and my out says MOTU 828. MOTU audio setup has default stereo input as Analog 1 - 2 and default stereo output as Analog 1 - 2. After I do all the steps quoted in "Calibrating the Soundcard", i get a message that says "impulse response is not correct". Am I conneting my loopback right. I'm NOT gonna use the BFD. I was just gonna connect a Rane PE 15 parametric equalizer and smooth out frequencies plus/minus 6-9 db's. Does the EQ have to be connected while the soundcard calibration is taking place. Do I have the SPL meter connected while the soundcard calibration is taking place. Someone please explain to me how to setup my loopback connection. How can I get the output within -1 db for the soundcard calibration. I can't control the volume. Someone please help. 

I have a G4 733, 1.5 g, 10.4.11, Digital Performer 5.13, Reason 4.0.1, 
My monitors are KRK's V8's and I just purchased the V12 Subwoofer. 

Please help, PlayItByEar Music.


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## JohnM (Apr 11, 2006)

With 10.4 REW can only access the built-in input, you would have to connect to that.


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## Guest (May 26, 2008)

JohnM said:


> Stretch, doesn't that contradict what you found in post 12 above? The description of what Line In does is to create an internal loopback, that would be a bad thing.


Yes, John. I was unaware at the time that Line In was still running in the background on my machine, even though I did not have it open in an active window.


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## htguy (May 14, 2008)

JohnM said:


> Do you have is set as a line input? Looks like you are getting very severe clipping, it needs to be set as a line input.


Thanks for sticking with this problem. A lot of Mac owners appreciate it.
The audio input in midi setup is set to "line in." 
I don't know why there would be clipping. Before I do the soundcard calibration, I adjust the input volume to within 3 db of the output (on the meters), and the peak less than -1 db, per the instructions.
I realized something very odd tonight. When I bring the line input vol to zero, I still get an input signal to REW. This does not seem good. I put the screenshots showing the settings. The input signal is with the sound at zero.


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## JohnM (Apr 11, 2006)

That looks like it may be taking input from the mic. Does the same thing happen if REW is set to "default device" for the input rather than "built-in audio"? After making the change in REW close and restart REW.


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## playitbyearmusic (May 17, 2008)

Thanks for the response! Should I connect from Analog 1 - 2 or the main outs on the MOTU? When calibrating the MOTU, should I use the left or right out? Also, I would have to connect the SPL meter's out to a MOTU in (left or right?) and then connect the MOTU's out (left or right?) to the built in input, right? If possible, could u please provide me with specifics on how to make appropriate connections? Please take into account that I also have a Rane PE 15 parametric eq that I will be using instead of the BFD. Thanks in advance, PlayItByEar


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## brucek (Apr 11, 2006)

> please provide me with specifics on how to make appropriate connections?


I trust you've already read REW Cabling and Connection Basics and REW Help Files.

brucek


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## htguy (May 14, 2008)

JohnM said:


> That looks like it may be taking input from the mic. Does the same thing happen if REW is set to "default device" for the input rather than "built-in audio"? After making the change in REW close and restart REW.


Yes, the same thing happens. It also happens when I connect the M-audio firewire solo to the imac. I don't know why REW would be getting a signal from the internal mic if the internal mic is not selected in sound or in midi set up.


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## playitbyearmusic (May 17, 2008)

Hey brucek, thanks for the response! I've read it several times but still an airhead to it. To calibrate the MOTU 828 MK1, all I have to do is connect a cable from the MOTU 828 Analog 1 - 2 output (left only) to the MAC built in input? After calibration of the MOTU, what is the connection scheme for connecting subwoofer, SPL meter, Rane pe 15 EQ, etc to take measurements? Please forgive me. New to this whole room measuring process but I just purchased a KRK v12 s to go with the KRK V8's in my recording studio and the sub requires the room measuring process. I just want it done right.

Thanks in advance, PlayItByEar MUSIC!!


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## brucek (Apr 11, 2006)

> To calibrate the MOTU 828 MK1, all I have to do is connect a cable from the MOTU 828 Analog 1 - 2 output (left only) to the MAC built in input?


I suppose if line-in of the motu doesn't work normally, you may need to use the built in line-in of the computer.




> what is the connection scheme for connecting subwoofer, SPL meter, Rane pe 15 EQ, etc to take measurements?


The sub and Rane have no connection with REW. They are connected to your system as they would normally be hooked up to use your system.

Your computer and REW software running on it are simply a tool to generate a signal to feed into your system, just as a CD player would be hooked into your system. An SPL meter is connected to the computer to read the level of that signal.

brucek


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## JohnM (Apr 11, 2006)

David, could you use the "Generate Debug file" option on the soundcard settings and either email the file to me or attach it in a reply.


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## htguy (May 14, 2008)

The debug file is attached.


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## playitbyearmusic (May 17, 2008)

Okay brucek, I'm back. The Mac 733 MHz doesn't support nor have an built in input. It only has and supports output. Now what can I do to calibrate the MOTU 828 MK1. 
I was informed that with 10.4, REW can only access the built-in input on the mac but it doesn't have one. 

Please help.

PlayItByEar MUSIC!!


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## Roland Gama (Apr 19, 2008)

Agree with you Stretch.


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## JohnM (Apr 11, 2006)

Thanks for the file David. Could you run another cal sweep and post the scope plot, but zoomed in on the initial part so that it fills the screen width i.e. I'd like to see more detail on the section below. After that can't hurt to try the Line In software that Stretch and Roland have had success with.


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## brucek (Apr 11, 2006)

> Now what can I do to calibrate the MOTU 828 MK1


I don't think you can use REW, since you have no input...

brucek


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## htguy (May 14, 2008)

JohnM said:


> Thanks for the file David. Could you run another cal sweep and post the scope plot, but zoomed in on the initial part so that it fills the screen width i.e. I'd like to see more detail on the section below. After that can't hurt to try the Line In software that Stretch and Roland have had success with.


John: Below is the zoomed in part of the scope plot. I hope it is the section you want. I will email you the measurement data to what I believe is your hotmail address. If you don't get it, PM me a better email address to use. I will play with the line in program tonight. Thanks

Strech: For the sound calibration, what exactly do you have plugged into the computer? Standard 1/8th inch stereo jacks?


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## JohnM (Apr 11, 2006)

Thanks David. I got the measurement data also. That plot shows what I suspected, and it will not be easily correctible. The data from the line input is massively overscaled, repeatedly wrapping around - it is likely that the byte ordering of the audio samples is wrong and the samples are being fed to REW as big-endian rather than little-endian, even though REW requests a little-endian input stream and the soundcard debug data shows little-endian as supported. I suspect this problem may afflict many of the PowerPC-based Macs. I can look at modifying REW to process big-endian data in a future build, but short-term there is nothing I can do to correct that problem. The Line In application may help, as it provides an additional software buffering layer in the audio data path which may corrrectly pass data to REW in the requested format.


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## htguy (May 14, 2008)

JohnM said:


> Thanks David. I got the measurement data also. That plot shows what I suspected, and it will not be easily correctible. The data from the line input is massively overscaled, repeatedly wrapping around - it is likely that the byte ordering of the audio samples is wrong and the samples are being fed to REW as big-endian rather than little-endian, even though REW requests a little-endian input stream and the soundcard debug data shows little-endian as supported. I suspect this problem may afflict many of the PowerPC-based Macs. I can look at modifying REW to process big-endian data in a future build, but short-term there is nothing I can do to correct that problem. The Line In application may help, as it provides an additional software buffering layer in the audio data path which may corrrectly pass data to REW in the requested format.


I am not that computer savy, so I realy don't understand the technical parts of your answer. Your answer is probably why REW would not work on my ibook g4 using the M-Audio Firewire Solo, as that computer is not an intel based machine. I wonder if the users who got REW to work on an imac have intel based imacs? Of course, if I had an intel based imac I could run windows anyway! If you can get REW running for non-intel based macs, that would be fantastic.	I’ll play with the line-in program, and if I get it to work I’ll post my settings.
Thanks for your work on this.
David


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