Calibration of my sound card Tascam US-2x2

4441 Views 4 Replies 2 Participants Last post by satbox, Jul 21, 2018

satbox

Discussion Starter · Jul 19, 2018

Hello,

I'm new REW user and want to use a Tascam US-2x2 sound card (connected to my MacBook pro via USB). I need some advice/confirmation regarding cables...

-Loopback cable in order to calibrate the sound card: what I understand is that I have to connect the IN 1 to the LINE OUT 1 (or LINE OUT 2?). LINE OUT of this device is balanced. I thought I would use one cable like this: 6.3mm(1/4") stereo TRS-jack to 6.3mm(1/4") stereo TRS-jack OR XLR to 6.3mm(1/4") stereo TRS-jack. Is it correct? What is the best? (after, during measurements, my mic will be connect to IN 1 via an XLR)

-Connection to my amp: during measurements, the sound card will be connected to my amplifier (standard hi-fi integrated amplifier). What I understand is that I have to connect the LINE OUT 1 (or LINE OUT 2?) of the sound card to the line in R and L of my amplifier. I thought I would use one cable like this: 6.3mm(1/4") stereo TRS-jack to 2xRCA. Is it correct?

Thank you for your help!

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Wayne A. Pflughaupt

· #2 · Jul 19, 2018

Most USB devices these days have ruler-flat frequency response, so no soundcard calibration is required, unless you need it for a timing reference. If that’s the case, just use a TS (mono) 1/4" cable between the input and output. The TRS cable you’re considering won’t work because the 1/4" input is unbalanced. Neither will the XLR to TRS, because it’s typically not a good idea to loopback via a mic preamp.

What I understand is that I have to connect the LINE OUT 1 (or LINE OUT 2?) of the sound card to the line in R and L of my amplifier. I thought I would use one cable like this: 6.3mm(1/4") stereo TRS-jack to 2xRCA. Is it correct?

The TASCAM’s outputs are balanced mono, not stereo, so don’t use that cable. You want a TS 1/4” to dual RCA cable. It doesn’t matter if you use #1 or #2.

Hope this helps.

Regards,
Wayne

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satbox

Discussion Starter · #3 · Jul 20, 2018

Thank you for your help!!!

wayne a. Pflughaupt said:
most usb devices these days have ruler-flat frequency response, so no soundcard calibration is required, unless you need it for a timing reference. If that’s the case, just use a ts (mono) 1/4" cable between the input and output. The trs cable you’re considering won’t work because the 1/4" input is unbalanced. Neither will the xlr to trs, because it’s typically not a good idea to loopback via a mic preamp.

So, when I calibrate the sound card, I have to set the switch "MIC/LINE INST" of the input to "INST"?

the tascam’s outputs are balanced mono, not stereo, so don’t use that cable. You want a ts 1/4” to dual rca cable. It doesn’t matter if you use #1 or #2.

Sorry for my ignorance but, in the us-2x2 specifications, it is specified that the line out is "6.3mm(1/4")TRS-jack(T：HOT, R：COLD, S：GND), BALANCED". So, why to use a TS to dual rca Y cable and not a TRS to dual rca Y cable?

Thank you!

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Wayne A. Pflughaupt

· #4 · Jul 21, 2018

satbox said:
So, when I calibrate the sound card, I have to set the switch "MIC/LINE INST" of the input to "INST"?

Yes.

satbox;1610532 said:
Sorry for my ignorance but, in the us-2x2 specifications, it is specified that the line out is "6.3mm(1/4")TRS-jack(T：HOT, R：COLD, S：GND), BALANCED". So, why to use a TS to dual rca Y cable and not a TRS to dual rca Y cable?

Because it’s not made for this purpose. The TRS to dual RCA is a splitter for stereo headphones, where T = Left side [+], and R = Right side [+] and S = signal [-].

The signal coming out of the TASCAM is not stereo. It’s balanced mono, where T = [+]; R = [-]; and S = [ground]. ( “HOT” and “COLD” is the same thing as signal [+] and [-] ).

Perhaps some pictures will better illustrate, but first you have to understand the difference between a balanced and unbalanced signal.

To simply things for the purpose of this discussion, with an unbalanced signal, the [-] is carried by the shield connection. This is why cables and connectors carrying unbalanced signals have two connection points (TS).

By contrast, a balanced signal separates the signal [-] from the cable’s shield (or ground) connection. This is why cables and connectors carrying balanced signals have three connection points (TRS).

To illustrate, the picture below is a female TRS jack, identical in function to what’s in your TASCAM. When a male TRS plug is inserted into the jack, the two tabs make contact with the plug’s Tip and Ring. The Sleeve connection is made through the body of the jack. (Side note: A female TS jack only has one of the tabs.)

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Here’s a picture of the male plug inserted into the female jack, showing the tabs (although this one is TS and only has one tab).

So: What happens, signal-wise, when the male TRS plug is inserted into the female TRS jack? In the picture below, the purple represents the TRS jack. The tabs send the signal [+] to the plug’s Tip, and the signal [-]to the plug’s Ring. The signal [-] is fully isolated from the Sleeve connection (to which the shield of the cable will be connected). So we have a balanced signal path.

Well and good. So what happens when we insert a male TS plug into that same TRS jack? As you can see below, the tab with the signal [-] is now connected to the Sleeve. Thus we now have an unbalanced signal, where the Tip carries the signal [+], and the shield carries the signal [-]. So basically, any balanced TRS jack can be converted to an unbalanced signal with a TS plug.

Now: What do we get using your TRS to dual RCA headphone splitter? As the picture below shows, the right side of the RCA splitter will get the Ring [-] signal, and the left side will get the Tip [+] signal. So plugging the two RCAs into your stereo, you’ll get no sound, because neither side is getting both the [+] and [-] needed to complete the signal.