Loop Back Test

Hi there i have been using a Tascam USB soundcard and there seems to be some kind of delays/alignment with audio tracks issues, does anyone have the instructions on how to perform a loopback test i downloaded a cubase loopback test from a link but there are no instructions with it ,could somebody print them on this thread please ,thanks .

Connect a line output of the tascam directly to a line input with a cable.
Make sure direct monitoring is disabled or turned down for the record channel and set that channel input to the one you connected the cable.
If you want to play on the safe side you might disconnect both speakers and turn down the headphone output first…easy to create a feedback loop here.
Hit record and let it play past the click which will be recorded onto the new record track.
Set ruler to samples, zoom right in and see how many samples between the two clicks.

Thanks Grim for your reply .the test has come back ,the tascam is 35 samples in front .i knew it wasn`t sounding right . how do i sort it out please ,thanks.

Enter 35 into Record shift on VST Audio System page…or -35.

But 35 samples is not so much…I’d be surprised if that makes the difference between it sounding right or not.

As Grim suggests, 35 samples is less than a millisecond…I too would be surprised if that was causing the audible difference you’re hearing.

At a sample rate of 44,1 KHz…

44100/35 = 1260

1 second = 1000ms

1000/1260 = 0,79ms delay.

Absolutely no chance you can ever hear a difference with that.

thanks for your replies,i have been recording an acoustic guitar on to two seperate mono tracks at the same time ,one direct and the other miced up and the stereo image seems much bigger than it should be when the two tracks are panned oppisite ,i noticed also that when i split the audio with snap on that it wouldn`t necesserily snap back exactly to a grid line ,it would sometimes leave a very small gap when i try sit them together it all seems a bit random at the moment.
yes i here what your saying about the 35 samples but i will give it a try anyway. thanks

You wouldn’t expect the direct and miked signals to be in perfect alignment as they’re different distances from the strings/soundboard of the guitar.

it is an electro acoustic and direct means coming out of the jack socket on the guitar and the other signal is a mic just placed in front of the guitar.Of course they will not sound the same and i dont want them to sound the same thats why i do it . but the signals seems too delayed. maybe i will put up a sound shot.

It’s not that they don’t sound the same. It’s that the sound arrives at the mic later. You should calculate how long it takes sound to travel the distance from its source to the mic.

But as Grim says above, this probably is something else.

Are you asking about the 35 sample difference in the signals or a longer delay that you can hear? Or something else?

As steve pointed out above I was wasn’t saying they wouldn’t sound the same I was saying there would be a delay. A quick calculation, assuming your mic is about 30cm from the guitar and you’re using 44.1 kHz,33 gives almost exactly the 35 sample delay you’re talking about. This won’t be heard as a delay but it might cause some phasing effects.

i fine tuned the loopback test and it does fluctuate a bit ,i have settled at 47 samples ,i think it is probably to do with the Tascam USB interface,people have said in the past that USB conected soundcards can be a bit unstable ,i never had these problems with an E-MU PCI conected soundcard but i did have issues with an E-MU USB soundcard.

Not sure which Tascam interface you have but I’ve had no problems with the US1800, been using it as my main interface for years. Never had an issue with any USB interfaces actually and I have four different ones across various computers. I think reported issues with USB interfaces were from the very earliest ones.

  1. Any miced instrument will arrive later than a DI from your guitar

  2. You can simply zoom into the track a little and use the NUDGE function in Cubase(You can set your quantize value and have snap turned on or do it by sight to move the other track so it lines up with the other.

  3. What is your buffer setting for your audio interface set to?

thanks for your reply ,yes i know there would be a slight difference between direct and miced but the delay difference i am getting at the moment sounds a bit exagerated,i have done this type of recording before with a pci sound card and there was never this same type of delay .yes i know about nudging one of the tracks to line them up , by the way the tascam usb soundcard is set at 256 samples. thanks

i have the us 16x08 and the us 2x2 .on this particular recording i was using the 2x2 . have you done this type of recording with DI and miced acoustic guitar, i mean i do quite like the effect of the delay but i know that it isn`t how it sound realy .

I would use 2 microphones.
Sometimes I use them together with a DI signal that I fade in as Mid signal, just for a little focus and body.

Yes, have recorded this way but not often…I don’t care for the sound from the guitar’s inbuilt pick-up much so if I’ve wanted to mix sounds i tend to use two mics as peakae suggested. I don’t remember having any issues…may have a try and investigate if i get a moment as it has me interested.

Zoom in on the 2 waveforms of this recording and you can see exactly how much delay there is. If everything is correct the mic signal should only be a ms or 2 behind the DI. (1ms per foot distance mic to guitar)
The loopback delay you measured has nothing to do with this as it would affect both of those tracks by the same amount.

the audio in my project produces hit points so i assume this is where impact with sound is made and i can see the hitpoint lines clearly, the direct signal is .005 ms in front of the miced signal the mic was approx 12 inches in front of the strings .even so it does sound like it is approx 5 feet away in the headphones… when i first looked at the two signals they looked to start at the same point i had to really zoom in to see a difference .this is the recording i made on saturday before doing the loop test and re calibrating the record shift so ill do another direct and mic test tommorow now that its calibrated for that soundcard . thanks for your interest Grim