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Low frequencies missing when connecting one soundcards output to anothers input Audio Interfaces
Old 29th July 2015
  #1
Here for the gear
 

Low frequencies missing when connecting one soundcards output to anothers input

TLDR: when I connect the output of one TASCAM US-122 mkII to the input of another, all low frequencies disappear. Do I need an amp in my setup?


Long version:

Hi all!

I hope someone here can help me with this, because nobody I know seems to know how to fix this...

For at least 15 years I've been trying to get an affortable midi-synced double DAW setup working. I did it before in the past and the results of two people jamming on the same track have always been surprising and interesting. But system upgrades ruined the old setup and I never got it working properly again.

Because of the latest system upgrade I now have two proper DAWs. I decided to give it another shot and I've managed to get MIDI sync through LAN working again. But connecting the output of the regular soundcard of the old pc to the line-in of the TASCAM US-122 mkII soundcard on my primary DAW produces a heavily distorted sound.

In an attempt to solve this I bought another mkII and when I use this (from RCA pin-jacks to a regular jack which is then converted to a 1/4" jack) the distortion is gone. Unfortunately I now seem to be missing all low frequencies... (there appears to be some odd ducking as well, but that could be the sidechaining in the track I used for testing, I did not check that yet).

When I directly connect the output of the source to a portable speaker the sound is fine. The inputs are working correctly too, I tested that by switching the mkII's. I checked the levels in the mkII's manual and they should be ok:

LINE OUT
Nominal output level -10dBV
Maximum output level +6dBV

LINE IN
Nominal input level -40dBu to +4dBu
Maximum input level +20dBu

Directly routing the input to the speakers makes no difference, so the problem is not in the software. The only other thing I could find in the manual was a remark about analog record player input requiring a "phono amp".

Is it possible that I need to add a preamp in between? Will any amp, like a guitar amp or a mic amp fix this? I can borrow a guitar amp from a friend to test that, but I'm not sure if they are meant to be used that way... Or could it be that I simply need to get a proper cable instead of the cheap old thing I used to test this?

Any hints are welcome!!!
Old 29th July 2015
  #2
Lives for gear
Quote:
Originally Posted by DrSiemer View Post
TLDR: ... (from RCA pin-jacks to a regular jack which is then converted to a 1/4" jack) the distortion is gone. Unfortunately I now seem to be missing all low frequencies...
I can't quite follow your description because I'm not familiar with these specific products. However, the classic "missing all low frequencies" symptom has a fairly common root cause:

Usually, the problem stems from a headphone output (1/8-inch or 1/4-inch) or an equivalent unbalanced stereo line out being run into a mono balanced input. The stereo output has plenty of signal strength, but the mono balanced input sees the unbalanced stereo tip and ring of the headphone output and does its normal analog algebra on those pins. The result is that you hear the net out-of-phase leftovers which is a thin, bass-less rendition of the original.

See if this theory matches your situation well enough to help you move forward on your diagnosis.

This stuff happens all the time when people attempt to plug their mobile phone or iPad output into a mixer channel.
Old 29th July 2015
  #3
Here for the gear
 

Thanks, I think you are right! The output is described as an "Unbalanced stereo line output" and the input in indeed a mono balanced input. The weird out-of-phase sound is probably caused by trying to send the unbalanced stereo output through a balanced mono input.

So the most likely solution is to simply get two separate RCA to (mono) 1/4" jack cables?
Like this one: Devine VA3015 2x jack male - 2x RCA male 1.5 meter (sorry, Dutch site, this type of cable is not very common it appears!)
Old 29th July 2015
  #4
Lives for gear
We're many steps closer to a satisfactory solution.

Starting from an unbalanced stereo output, a cable known as an insert cable will allow you to take that output and send it to two mono inputs. Your task will be to get the sizing adapters on the TRS end of the insert cable so you can plug that into the stereo output. Then on the twin-tailed end, you'll have to ensure you have the right flavor (RCA, or TS) directly or via adapters to plug into the destination mono inputs.

Use this handy cable finder function at the Sweetwater site to determine your needs. It's in English, as that's the only language in which I am literate.

Cable Finder | Sweetwater.com
Old 30th July 2015
  #5
Here for the gear
 

Well, my output is not a single stereo output but two separate RCA outputs (a left and right) so the cable finder confirmed for me that I need to get the cable I linked to. I'm pretty sure cables like that will have a mono jack on the other end, that will not confuse the sound cards input. It will be here on Monday, so I might finally have a proper double DAW setup running next week! :D

I will let you know how it works out, thanks for you help!
Old 5th August 2015
  #6
Here for the gear
 

The new cables work!!! Thanks again for your help, I finally have a proper double DAW setup ^_^
Right now I'm still using rtpMidi to sync the systems via LAN, which seems to work very well, but I might upgrade this to using an actual midi cable now that I have two proper sound cards.

Here's a short video of it, I'll post a more in-depth demonstration when I have made some actual songs with it
https://www.youtube.com/watch?v=MBA_bBmrR6c
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