Page 1 of 1

How to record but not monitor

Posted: Tue Mar 31, 2015 7:42 am
by PsyTech
I'm trying to play audio from track 1, send it into the phone line (with my phone hybrid), and simultaneously record the phone line on track 2. The problem is I keep getting feedback. I guess what I need to do is record but not monitor recording.

Re: How to record but not monitor

Posted: Tue Mar 31, 2015 2:54 pm
by Oswald Schwander
If I unterstand you right you are looking for a setup to monitor track 2 but not track 1. Depends on your setup how you best do that.
Do you have a extra hardware output you can use for track 1 to phone, that is not part of your monitoring?

Oswald

Re: How to record but not monitor

Posted: Tue Mar 31, 2015 3:25 pm
by Fredo
Phones have always been a problem; reason why telephone Hybrids are used for recording phone conversations.
http://en.wikipedia.org/wiki/Telephone_hybrid

Sure you can get away with alternaive setups, but you'll always bump into the feedback problem.

Fredo

Re: How to record but not monitor

Posted: Tue Mar 31, 2015 6:24 pm
by Hugh
Hello,

As Fredo said it's an inherent problem with phone lines, by definition they loop back because they are a 2-wire circuit (both send and receive on the SAME wires) not a 4-wire circuit.
There are vastly different qualities of phone hybrids, we deal with them all the time. The passive units are terrible. The JK analog units are mediocre at best. We've had the best results with the Telos units and the Telex TIF units. They are both rentable.

Hugh

Re: How to record but not monitor

Posted: Tue Mar 31, 2015 9:12 pm
by PsyTech
Oswald Schwander wrote:If I unterstand you right you are looking for a setup to monitor track 2 but not track 1. Depends on your setup how you best do that.
Do you have a extra hardware output you can use for track 1 to phone, that is not part of your monitoring?

Oswald
I'm using an RME BabyFace.
As Fredo said it's an inherent problem with phone lines, by definition they loop back because they are a 2-wire circuit (both send and receive on the SAME wires) not a 4-wire circuit.
There are vastly different qualities of phone hybrids, we deal with them all the time. The passive units are terrible. The JK analog units are mediocre at best. We've had the best results with the Telos units and the Telex TIF units. They are both rentable.
I'm using a Gentner SPH-3A. I don't see how quality of hybrid has anything to do with this.

Seems like I need to play the track from another computer. It would be nice if I could do it all from one computer though.

Re: How to record but not monitor

Posted: Tue Mar 31, 2015 10:53 pm
by Oswald Schwander
I think now that what I told you is nonsens as there is no microphone involved
I'm trying to play audio from track 1, send it into the phone line
.....Even if both tracks would be monitored there would be no feedback (it would be just a mix between direct signal and proceessed signal).
That would mean it is a inherent problem with phone lines as Hugh and Fredo say...

Oswald

Re: How to record but not monitor

Posted: Wed Apr 01, 2015 6:15 am
by Hugh
Hello psytech,

I'll attempt to explain. Your initial post was short and much needed to be inferred. I'm guessing by your term "feedback" you mean too much of the outgoing audio being recorded on the incoming phone recording. If you actually mean acoustical or electrical feedback then your interface or software is not set up correctly. If instead you do mean too much outgoing audio on the recorded incoming call then it's a telephone hybrid issue.

When using phone hybrids the quality is everything - the quality of the nulling ability to cancel out the outgoing audio from the incoming. Phone lines are terribly nonlinear transmission lines so the nulling mechanism needs to be very good for adequate isolation. Your Gentner model uses a simple Wheatstone bridge to achieve the null and does not do a very good job. The Telos units and some other models of Gentner use a digital complex nulling dsp that listens to the outgoing and the incoming and alters multiple parameters to get a pretty good null.

If you need any assistance with understanding phone line applications let me know.

Hugh

Re: How to record but not monitor

Posted: Wed Apr 01, 2015 6:17 am
by PsyTech
Hugh wrote:Hello psytech,

I'll attempt to explain. Your initial post was short and much needed to be inferred. I'm guessing by your term "feedback" you mean too much of the outgoing audio being recorded on the incoming phone recording. If you actually mean acoustical or electrical feedback then your interface or software is not set up correctly. If instead you do mean too much outgoing audio on the recorded incoming call then it's a telephone hybrid issue.
Not a hybrid problem at all. I'm literally getting a nasty feedback loop when I record.

Unless there's some way of muting a channel or configuring a special output or something then I guess I'm gonna have to play the source from another computer.

Re: How to record but not monitor

Posted: Thu Apr 16, 2015 1:38 am
by PsyTech
Tried playing back from another computer but playback speed keeps deviating slightly over time. The only way is gonna be if I can record with Nuendo but not monitor the input sound that is being recorded. Otherwise it just feeds back into the phone line. Again, not a hybrid quality problem.

UPDATE: I figured out an obvious work around. I'll just rerecord my main source track WITH my phone line track. I'll record onto 2 tracks of cassette while playing the source from my computer. No need to worry about feedback doing it that way.