Using Edirol UA-1EX with REW

**jaypeecee** · **05-20-08, 11:09 AM**

Hi Folks,

I have installed REW on my laptop (running Win XP Pro SP3). As my laptop does not have line in / line out connectors, I am considering the use of an Edirol UA-1EX. Would that work OK? Does anyone have any specific tips when using the UA-1EX with REW?

Many thanks.

JPC

**JohnM** · **05-20-08, 05:54 PM**

Should be OK. The input monitor dip switch would need to be set to off, input dip set to analog, sample rate dip set to 48kHz.

**jaypeecee** · **08-21-08, 12:54 PM**

Normal service has been resumed after a period of inactivity caused by a faulty laptop! That's why there's been a long interval between my original post and now.

As the UA-1EX has a powered microphone input, is it not possible to use a suitable electret mic plugged into the UA-1EX in order to take measurements? I have an electret mic that is flat to within 0.5dB from 20Hz to 20kHz. As I understand it, sound measurements with REW are normally made with an SPL meter taking the signal from the meter's line out - is that correct? Is there no provision for using a microphone other than the one in the SPL meter?

Sorry if I'm asking a silly question but I'm a complete beginner as far as REW is concerned.

Any replies would be greatly appreciated.

**brucek** · **08-21-08, 01:43 PM**

Quote:

Is there no provision for using a microphone other than the one in the SPL meter?

Yes, as indicated in the REW Help files, any microphone may be used as long as you have a calibration file that must be loaded to render the microphone flat.

Soundcard line-in jacks expect line-level signals, and as such, electret condenser microphones such as the Behringer ECM8000 (that we do supply a calibration file for) must use a preamp to boost the signal to line-level.

Some soundcards have an internal preamp with phantom voltage that can be used in lieu of an external preamp. I believe the UA-1EX is only equipped to operate inexpensive 'computer type' electret microphone that require low voltage (~3v) to operate. Not sutable for a measurement mic such as an ECM8000.

brucek

**vmaharaj** · **08-22-08, 07:47 AM**

Hi,
Yes there are no problems to using the Edirol as a USB soundcard. I have one and it works fine. Just take John's recommendations and you are good to go. Remember to calibrate the soundcard...

**jaypeecee** · **08-22-08, 08:55 AM**

Hi Guys,

Thanks for the replies. Regarding the use of an electret mic with the UA-1EX, I was going to make my own mic using the Panasonic WM-61A mic capsule. I seem to remember that the UA-1EX provides 3.3V dc to 'powered mics'. Obviously, I need to study the REW Help file to see if it's possible to produce a calibration file for my home-made mic. Incidentally, the Behringer ECM8000 uses an electret capsule as the sensing element.

**brucek** · **08-22-08, 09:17 AM**

Quote:

I need to study the REW Help file to see if it's possible to produce a calibration file for my home-made mic. Incidentally, the Behringer ECM8000 uses an electret capsule as the sensing element.

It's quite simple to make a calibration file for REW if you have the data for your mic. Even a graph is enough to create the file. I can certainly help you with it, if you need.

The ECM8000, along with many measurement mics use an electret capsule, but that's not all they consist of. The higher phantom voltage for these measurement mics is for the electronics. See the schematic below of the ECM8000... The ECM is quite inexpensive.

brucek

**jaypeecee** · **08-25-08, 08:07 AM**

brucek,

Thanks for offering to help with the calibration file. I may well take up your offer when I get to that stage. I'm progressing a little slowly at the moment as I'm trying to do too many things at once!

**jaypeecee** · **08-25-08, 09:54 AM**

brucek,

You've got me thinking about the ECM8000. Looking at the schematic, I presume that the ECM8000 connector has 4 pins - XLR1, 2 and 3 plus a separate pin for the phantom power supply. Is it supplied with a suitable lead? I'm also trying to work out how I would connect the ECM8000 to the Edirol UA-1EX. The ECM8000 output appears to be balanced but the line in on the UA-1EX is via a RCA phono connector.

It also occurred to me that, if I were to use the Panasonic WM-61A capsule, I may be able to produce a calibration file based on its frequency response. However, this would not take into account the frequency response of the mic preamp inside the UA-1EX and, unfortunately, I don't have any data on this preamp. Furthermore, this preamp would not be included when I calibrate the sound card as this uses the line in/line out RCA phono connectors.

I would welcome your assistance.

**brucek** · **08-25-08, 10:19 AM**

Quote:

I presume that the ECM8000 connector has 4 pins - XLR1, 2 and 3 plus a separate pin for the phantom power supply. Is it supplied with a suitable lead?

No, the 48volts power supply connects to pins 2 and 3. It's DC and so doesn't interfere with the AC signal (that's why they call it phantom)....

Quote:

I'm also trying to work out how I would connect the ECM8000 to the Edirol UA-1EX.

As I mentioned in my posts above - I believe the UA-1EX is only equipped to operate inexpensive 'computer type' electret microphone that require low voltage (~3v) to operate. Not suitable for a measurement mic such as an ECM8000..
To use the ECM8000, you would require a proper microphone preamp that brings the level up to a line-level that the soundcard can handle. The output of the preamp would be either balanced or unbalanced depending on the connector type used...

See this thread on connections.. half way down the page is the connection info for the ECM...

brucek

**jaypeecee** · **09-02-08, 09:37 AM**

Quote:

JohnM wrote:

Should be OK. The input monitor dip switch would need to be set to off, input dip set to analog, sample rate dip set to 48kHz.

John,

I just noticed that the input monitor dip switch does not have an 'off' position - the two positions are 'on' and 'auto' so I guess I select the 'auto' position. What say you?

JPC

**JohnM** · **09-02-08, 12:20 PM**

Yes, use "Auto"

**jaypeecee** · **09-05-08, 11:46 AM**

Well, I've obviously done something wrong. I set the Edirol UA-1EX as input and output device. Then, set REW to measure from 15Hz to 20kHz. When I checked the levels, it said they were low but gave me the option of running a measurement so I did. The resulting graph was a straight line but went from -30dB at 15Hz to +30dB at 20kHz. From this brief description, can anyone shed any light on what I might be doing wrong? Incidentally, the UA-1EX has an 'Advanced Driver' switch, which the instructions advise normally leaving 'ON' and that's what I did. As I understand it, the advanced driver enables 96kHz sample rate, which I'm not using.

Any suggestions would be greatly appreciated.

**JohnM** · **09-05-08, 12:05 PM**

Most likely a connection problem. The graph you described sounds like cross talk picked up on an unconnected channel, when you checked levels did anything register on either input? If something did register, was it on the input REW has been set to capture from?

**jaypeecee** · **09-05-08, 03:16 PM**

John,

Many thanks for your reply. You were spot on with your diagnosis. The lead that I was using from RCA phono out to RCA phono in on the UA-1EX was defective. Isn't it annoying when something like that is the cause of the problem?

Anyway, I now appear to be back in business.

Thanks again.

**jaypeecee** · **09-29-08, 01:57 PM**

Hi Folks,

Well, I'm making slow progress. I used the right channel of the UA-1EX to run a frequency response measurement from 15Hz to 22kHz. In the REW Help, it says "Having obtained a measurement it needs to be saved as a calibration file. Press the Make Cal button in the Soundcard Settings" but this button is greyed out immediately after running a measurement so I am unable to create a calibration file.

Regarding the "Use Left Channel as calibration reference", it goes on to say that "the left channel signal must be looped back from output to input". I presume this simply means that the left output must be connected to the left input. Should I use the left channel to produce the calibration file?

I also ran a left channel frequency response measurement, which proved to be almost identical to the right channel - consistently 0.5dB lower from 15Hz to 17.4kHz and converging at 22kHz.

All comments would be greatly appreciated.

**brucek** · **09-29-08, 03:20 PM**

Quote:

In the REW Help, it says "Having obtained a measurement it needs to be saved as a calibration file. Press the Make Cal button in the Soundcard Settings" but this button is greyed out immediately after running a measurement so I am unable to create a calibration file.

Since you have no control over the range of frequencies to measure when running a soundcard calibration routine, it indicates to me you didn't press the correct Measure button as shown below...

Name: soundcard cal Measure.jpg
Views: 123
Size: 58.8 KB

Quote:

Regarding the "Use Left Channel as calibration reference", it goes on to say that "the left channel signal must be looped back from output to input". I presume this simply means that the left output must be connected to the left input. Should I use the left channel to produce the calibration file?

No, you don't produce a calibration file if you're using the "Use Left Channel as calibration reference" method (rather than the Soundcard calibration method). The optional "Use Left Channel as calibration reference" uses a permanent looped cable on the left channel at all times and a calibration file isn't used.

I wouldn't recommend using the "Use Left Channel as calibration reference" method. It's easier to use the Soundcard calibration file method.
This means you don't check the "Use Left Channel as calibration reference" box and you don't ever use the left channel.
You temporarily connect a loopback cable on the right channel and create a calibration file once and store it.
Then the loopback is removed and the right channel is used for measuring.

brucek

**jaypeecee** · **09-30-08, 10:01 AM**

BruceK,

Many thanks for your help. I'm now on the right tracks. I now need a calibration file for the Radio Shack 33-2050 analog SPL meter. Is there such a thing and where might I get it from? I'm sure I've seen one somewhere on the web but my memory fails me.

Any suggestions?

JPC

**brucek** · **09-30-08, 01:58 PM**

See the REW Information page to find the cal file.

brucek

**jaypeecee** · **10-02-08, 09:48 AM**

Thanks, Bruce.......JPC

Advertisement