True balanced output?

[Casey_Pittman]

Came upon and interesting issue. I was trying to troubleshoot a piece of equipment yesterday and was sending a 1k tone out of the bus outs of the console to the input of an eq with a balanced input. And later from the AUX outs. But it seems that I'm only getting the signal on the hot pin and not both the hot and cold.

I am using a signal probe to check this.

Now I know I should be getting signal on the cold as well because I can use a tascam usb interface and everything works fine.

The manual states that the Bus and the AUX outs are balanced but I'm not seeing it. Has anyone else had this issue? Did I misread or not read the correct information concerning the Bus and Aux outs?

BTW I'm on V3 software.

Any thoughts, comments are welcome.

Thanks,

-Casey

[High C Double G]

I wired my DB25 in a balanced way but never checked it. Always assumed it was a balanced output.

[Casey_Pittman]

Can you or anyone else check to make sure I'm right? I'm just sending a tone from Cubase to the d8b then assigning it to all bus outputs and aux outs. I've got a DIY signal tracer and I can hear the tone on the hot pin but not the cold on any of the outputs.



Thanks,

-Casey

[anyhorizon]

From that diagram, if using a guitar lead, you'd be tying one side to ground. Dunno, the diagram is unclear. Anyway, the outputs and inputs are differential which although referred to as balanced, is a little different. CMR is still active though.

Peter

[Casey_Pittman]

Peter,

The one I made doesn't have the female jack it uses the lead from the cap to sniff the signal and yes i do connect the alligator clip to the sleeve. So I probe the tip and ring separately from each other and every time I get the same result. Signal on tip(hot) no signal on ring(cold).

I don't know. I get the differential thing but shouldn't there still be signal on the cold pin? Or do I not get the differential thing at all?

-Casey

[anyhorizon]

Casey, I know you're pretty cluey but I'm not clear on your MO so I'd better wait until you offer more info or I can digest the above better. I have no idea what the cap is for. It's unnecessary for signal checking.

Peter

[Casey_Pittman]

Peter,

I think the cap may be for voltage protection so you don't nail anything in the path afterwards.

But here goes,

Set up cubase tone generator to 1k @ -15dbfs send to output 1(ch 25 on d8b). Assign the channel to all buses and aux sends and remove from LR. Make sure to set the channel fader to unity. As well as the bus out faders. This is a good time to see if your bus meters show the same amount of signal as the return channel(25). If it doesn't then that's a different problem in my opinion.

For the signal probe. Take a guitar cable cut off one end connect the shield to some alligator clips, and use the other wire as your probe point, viola signal probe.

Plug signal probe into channel 1 and set gain to unity(or whatever shows you signal, this part is not critical right now).

Now, connect alligator clip to the sleeve of the balanced output. Then touch the probe to the Tip(hot) of the balanced cable. You should hear the 1k tone on channel 1.
Then, touch the probe to the Ring(cold) of the balanced cable. You should hear the 1K tone on channel 1.

It is at this point that I get no signal from the Ring(cold) on either the bus or aux outputs.

Also if it were balanced I should be able to plug any of those out puts into a line in and set the channel gain to unity and get the exact level that I'm sending back in right? Well, not in this case. Because I'm losing half of a balanced signal.

If you see a flaw in my method please point it out or if something wasn't explained well enough I can try to do that better as well. Maybe a youtube video could help.

Please some one else try this and tell me what you find.

-Casey

[csp]

Casey,

Like Peter I am a bit confused, but a guitar lead is not balanced, to get a balanced signal to pass through a lead it must be (in simple terms) a stereo lead --- that is the plugs at each end have to be Tip-Ring-Sleeve.

If you wish you can plug an unbalanced signal into one of the console's input using (say) a guitar lead from any mono source, now from within the console it will be converted into a balanced output (where a balanced output is available).

Therefore, I would think that if you plugged a stereo (TRS) plug into the Aux outputs then you would get a signal on both the tip and ring and if you could look at both of these signals on a dual trace CRO, then you would find that at any point in time, the tip would be showing a positive signal while the ring would be showing an identical negative signal --- the sleeve would have to be connected to the earth on both CRO inputs (or the common earth if it has one).

By the way, you can generally use a balanced output in unbalanced mode if you use either a mono jack or a stereo jack with the ring connector (negative/cold feed) joined to the sleeve (earth) along with the earth lead, because the mono jack effecvtively joins the ring and sleeve (as a result of the sleeve being much longer and therefore covering the part on a stereo jack where the ring would be), but it is always a good practice to come out of a balanced output in balanced mode (ie use a TRS jack) and run a balanced cable for the length of the cable and then do the balanced to unbalanced conversion at the end where the mono jack is to be used, in other words, do not use a mono guitar lead for the entire run. Just ensure that the lead going to the tip of the TRS jack goes to the Tip of the mono jack, otherwise it will work but it will be out of phase.

I hope that the above gives you a better idea of the situation, sorry I can't draw the cables to show you in pictorial form.

David

[Casey_Pittman]

The signal probe does not have to balanced. All you are doing with it is touching the now exposed wire from the end that was cut to the source(cable) that has audio passing through it. And since you have plugged in this signal probe to an amplification source like a gtr amp or another channel on the d8b you will see the signal pop up on the meters or produce the tone that is passing through the cable. You do not have to touch both the tip and ring at the same time. At no point does the fact that the signal probe is not balanced come into play or matter.

Here's a couple videos I found on youtube that describes what I'm doing. Mind you he's doing this with a blues jr. but the method is the same.





I'll make a video showing what I'm doing later this week. Would be nice if frank or someone that had their hands in the design could pop in and say yes or no on the matter of true balanced output on the Bus and AUX's.

-Casey

[anyhorizon]

That stuff is irrelevant. Are you using a TRS or a TS connector at the output? Your diagrams indicate TS. How could that possibly work? If you wanted to check the "cold" of the signal, you would have to pull the jack out of the d8b to it's first click (ie, only half inserted), then measure at the end of the cable as per your OP.

Peter