Headphone amp for the DL 1608

[Sting]

Our drummer purchased a behringer ha4700 headphone amp. They had a problem with noise running out of the aux sends on the DL.  I believe it is because this amp doesn't support balanced connectors on its aux inputs.  Am I wrong on this? If not what are you guys using for IEM?

[WK154]

The HA4700 on both direct in and aux is unbalanced (TRS stereo is the clue). The only balanced lines in and out are the mains. I had similar problems with a Yamaha mixer and HA4700 but managed to quiet it with the right cable hookup. Of hand I don't remember the solution it's been a while. The DL doesn't help this issue since it has a pin one problem. The right power supply for the DL and the cable that lowers the input noise may make this workable. Better to just return it and find a headphone amp with balanced inputs.

[Wynnd]

There's no phantom power on the Aux outputs.  For unbalanced runs, keep the cable short, consider a DI box in line.  Both of those should help.  (Maybe the DI box more than the cable.)  Balanced is a stronger signal and cleans up anything that the cable picks up.  That only works when both ends are balanced.  You might also want to carry the signal out balanced and put a matching transformer on the amp's input.  (Probably as good as a DI box.)

[WK154]

I'm guessing but if it's just for the drummer he would want something like the Behringer Powerplay P1. Just haven't seen anyone carry this. Two balanced inputs to headphones with pan and loudness control.

[walterw]

The DL doesn't help this issue since it has a pin one problem.

how do you mean?

[WK154]

The DL doesn't help this issue since it has a pin one problem.

how do you mean?

Injects equipment leakage currents into the signal.
http://cacophony.aspinock.com/index.php?topic=383.0

[Sting]

The HA4700 on both direct in and aux is unbalanced (TRS stereo is the clue). The only balanced lines in and out are the mains. I had similar problems with a Yamaha mixer and HA4700 but managed to quiet it with the right cable hookup. Of hand I don't remember the solution it's been a while. The DL doesn't help this issue since it has a pin one problem. The right power supply for the DL and the cable that lowers the input noise may make this workable. Better to just return it and find a headphone amp with balanced inputs.

This headphone amp is only being used to run a quiet monitor mix for practice sessions.   The problem is that all of the headphone amps that I have seen have stereo or unbalanced inputs.   They got by last time by running headphones directly from DL's aux sends but that's not the best solution IMO.  So a direct box or transformer- equipped cabling may be the fix...I don't know at this point.

[sam.spoons]

Transformers aren't needed, just make up some cables as follows, TRS to TRS with the ring (cold/-ve) left unconnected at the mixer end * and the tip and ring shorted at the headphone amp end (to send a single signal to both the left and right channels). These will supply a full line level signal to both sides of the stereo direct input for each headphone output and should (the concept works on my setup) be interference free.

If you're feeding a mono TS unbalanced input just fit a TS jack at the amp end.

* This works because the cold/-ve on the DL's aux outputs carries no signal. Counter-intuitive I know but it works, I tried leaving the ground unconnected but it didn't solve the noise issue.

The aux outputs are impedance balanced which means the cold is simply connected to earth by a resistor, this fulfils the need for both hot and cold to be the same impedance in a balanced system but gives a full signal between either the hot and cold or the hot and ground.

HTH

[Sting]

Transformers aren't needed, just make up some cables as follows, TRS to TRS with the ring (cold/-ve) left unconnected at the mixer end * and the tip and ring shorted at the headphone amp end (to send a single signal to both the left and right channels). These will supply a full line level signal to both sides of the stereo direct input for each headphone output and should (the concept works on my setup) be interference free.

If you're feeding a mono TS unbalanced input just fit a TS jack at the amp end.

* This works because the cold/-ve on the DL's aux outputs carries no signal. Counter-intuitive I know but it works, I tried leaving the ground unconnected but it didn't solve the noise issue.

The aux outputs are impedance balanced which means the cold is simply connected to earth by a resistor, this fulfils the need for both hot and cold to be the same impedance in a balanced system but gives a full signal between either the hot and cold or the hot and ground.  I guess your TS option leaves me a little confused. Sorry


HTH

Yes we are running mono unbalanced mixes from the DL aux sends to the headphone amp.  I will make up these cables.  Thank you

[sam.spoons]

Transformers aren't needed, just make up some cables as follows, TRS to TRS with the ring (cold/-ve) left unconnected at the mixer end * and the tip and ring shorted at the headphone amp end (to send a single signal to both the left and right channels). These will supply a full line level signal to both sides of the stereo direct input for each headphone output and should (the concept works on my setup) be interference free.

If you're feeding a mono TS unbalanced input just fit a TS jack at the amp end.

* This works because the cold/-ve on the DL's aux outputs carries no signal. Counter-intuitive I know but it works, I tried leaving the ground unconnected but it didn't solve the noise issue.

The aux outputs are impedance balanced which means the cold is simply connected to earth by a resistor, this fulfils the need for both hot and cold to be the same impedance in a balanced system but gives a full signal between either the hot and cold or the hot and ground.  I guess your TS option leaves me a little confused. Sorry


HTH

Yes we are running mono unbalanced mixes from the DL aux sends to the headphone amp.  I will make up these cables.  Just to be clear, how is the TS wired?  The hot from tip and cold from mixer end soldered to tip of TS?

No for this you are sending a mono unbalanced source to a stereo unbalanced input (the direct inputs on the HA4700) so you need TRS at both ends but wired differently (they probably won't work at all if plugged in the wrong way round so mark them or use different coloured plugs on each end).

Anyway, to make them use cable with a single conductor and screen and TRS jacks at both ends. Connect the screen to the sleeve at both ends, the centre conductor to the tip only at the mixer end (leaving the ring unconnected, very important) and to both tip and ring at the headphone amp end. The result is that the signal is the difference between Hot and Ground and is fed to both sides of the stereo direct inputs on the headphone amp.

[Sting]

Got it...thanks

[Jerrylee]

Just do what I have been doing since I have owned the dl1608 with zero issues. Get the headphone adapter that converts a mono signal to stereo and plug it right into the dl. My drummer has done this hundreds of times. Works great and no extra gear needed. I have done a lot of rehearsals as well where the entire band would plug right in to their own aux. The aux sends are just as hot as the headphone send itself. People here are going to say not to do this because the auxes are no meant to bee used like this. Greg might give some technical reason. Ignore them all. It works and has been overly tested.

[sam.spoons]

I have just set up my DL1608 and HA4400 to try this. The noise is still there even with the cable I describe above but much reduced compared to a TS-TS cable (It completely cured the problem with my AER Custom 60's unbalanced line input). I've tried various combinations (half an hour sweating over a hot soldering iron :-) but with my ACS T3 IEM's nothing completely removes the problem and the custom cable is as good or better than anything else.

Jerry's option will work as it doesn't introduce another amp with an unbalanced input into the system (headphones straight out of the aux using a suitable adapter). There are theoretical reasons why not to do it but I can't remember if Mackie (Beno, back in the good old days) had any advice on the advisability of plugging headphones into the auxs and as JL says, lots of people have done it without harm to the DL.

[WK154]

OK here's the tech side of this. The aux outputs are more than likely NJR 4580 which amongst other uses are recommended for headphone amp applications. I didn't take the analog section apart in my autopsy but judging from rest of what's in the DL and used in the C1604VLZ (where I have schematics) they're 4580's. Since you will be driving two impedance's in parallel (stereo) your best off with higher impedance headphones (50 ohms + which would be a 25+ ohm load on the 4580) less load on the aux output. You could also only drive one side of the headphone. Some talent likes to feel their keeping track of everything. The residual noise is of course pin one related if it's bothersome go for the power supply solution. The one thing that the Powerplay P1 has that's not in these solutions is a signal limiter. Set up your compressor as a limiter for some safety. Best to let everyone control their own levels (Myfader). One other thing headphones have no chassis leakage hence no noise currents. Another example in audio of less is more.

[Harpman]

I have just set up my DL1608 and HA4400 to try this. The noise is still there even with the cable I describe above but much reduced compared to a TS-TS cable (It completely cured the problem with my AER Custom 60's unbalanced line input). I've tried various combinations (half an hour sweating over a hot soldering iron :-) but with my ACS T3 IEM's nothing completely removes the problem and the custom cable is as good or better than anything else.

Jerry's option will work as it doesn't introduce another amp with an unbalanced input into the system (headphones straight out of the aux using a suitable adapter). There are theoretical reasons why not to do it but I can't remember if Mackie (Beno, back in the good old days) had any advice on the advisability of plugging headphones into the auxs and as JL says, lots of people have done it without harm to the DL.

I picked these up at Radio Shack. Part #274-348 (1/4" mono male to 1/8" stereo female) as a "suitable adapter". They also sell a 1/4" mono male to 1/4" stereo female as well.  They work quite nicely:
https://www.dropbox.com/s/pfjcxz0w0owe6rs/2013-12-30%2009.46.22.jpg

In my particular application, I already have 1/4" to 1/4" mono cables so all I need to do is add a 3" barrel 1/4" female to 1/4" female connector, plug in the adapter and then the IEM's  That way the musician can disconnect rather quickly.