FF800 & Stereo Headphone Sends

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Profile picture for user soapfloats
Submitted by soapfloats on Sat, 01/28/2012 - 23:45

This is a problem I've been troublesooting for some time.
I'm trying to get sends that contain stereo mixes.
Sometimes the clients get one ear, which can be remedied by plugging any balanced cable in part-way. But it's not stereo.
There's been a host of other issues, most of which I've solved.

The mixes of the FF800/TotalMix are routed to Analog Outs 1+2, 3+4, 5+6, 7+8, and 9+10.
I use 1+2 for CR monitors, and the remaining pairs for headphone mixes.

My signal chain:
FF800 > Patchbay > snake returns > HP amp > Headphones

Seems the issue is in the cabling.
To the best of my knowledge, I am using balanced TRS cables and balanced connections, w/ one exception:
The Y cable I am using to combine the paired outputs on the FF800 to one cable that feeds the patchbay.
In fact, the signal chain could be reduced to: FF800 analog outs > Y cable > snake return.
I'm currently using Hosa Y cables that I believe to be (2x) TRS Male to (1x) TRS Female.
Again, all cabling/connectors beyond that point are TRS.

Any ideas?

Are you sure you are not confusing balanced signals with unbalanced stereo feeds? The FF800 outputs (except for the headphone jack on the front panel) are each mono TRS balanced.

The correct cabling will depend on what you are using for a headphone amplifier. If it takes balanced inputs, you need separate TRS balanced feeds for the L and R signals. No Y-cable involved.

If it has unbalanced L and R jack inputs, you need either specially-wired TRS-TS cables (once for each of L and R), or else a pair of insert cables, using the tip (send) TS plug and leaving the ring (return) plug disconnected. Again, no Y-cable.

I've never seen one of these, but if your HP amps have a single stereo TRS input jack, you will have to wire a special cable or use the pair of insert cables into a 2xTS - TRS adaptor.

In terms of using a snake, I would not try to send a stereo HP feed over a single XLR circuit. Aim to preserve the balance and minimize cross-talk by using two snake circuits.

I would think your problem is in the "Y' cable as well.
The balanced outputs on the FF800 are T (+) R (-) S (shield).
The actual mono signal is only on the Tip & Ring....the shield is not carrying any signal.
The stereo inputs on the HP amp are also TRS but they are Tip Left(+) Ring Right(+) and the Sleeve is common Left & Right (-). There is no shield.
So you need a "Y' cable that commons both the Ring sides (-) from each of the two output cables connected to the Sleeve of the HP amp input with the Tip being (+L) from one cable and Ring being (+R) from the other cable.
You would dead end the shields from each of the FF800 output cables at the HP amp input end.

I don't think that is a standard "Y" cable.

You should run the 4 pairs of FF800 headphone feeds out to the HP amp and then terminate them at the HP amp with your breakout stereo cables. I'm assuming the HP amp has four stereo inputs??
But if you do it that way your running balanced lines all the way out to the HP amp.
Be sure to insulate the dead end shields!
Stuff like ths would be easier to draw a wiring diagram! :cool:

djmukilteo, post: 383663 wrote: The stereo inputs on the HP amp are also TRS but they are Tip Left(+) Ring Right(+) and the Sleeve is common Left & Right (-). There is no shield.
So you need a "Y' cable that commons both the Ring sides (-) from each of the two output cables connected to the Sleeve of the HP amp input with the Tip being (+L) from one cable and Ring being (+R) from the other cable.
You would dead end the shields from each of the FF800 output cables at the HP amp input end.

Sorry, but that's incorrect advice. The outputs (tip or ring) from any of the rear FF800 jacks should not be commoned with the signals from another output. If an unbalanced stereo pair of signals is required, you can take the tip signals from two outputs along with the sleeves, but you must in that case leave the rings unconnected.

Until we know the model of HP amp and hence what input connections it has, we can't really say much more.

This is true in some gear that has pseudo-balanced or "impedance balanced" outputs. In this case, all the signal is carried on the +ve connection and the -ve connection is grounded via a resistor at the transmitting end only.

In gear that has true differential outputs (in which category the FF800 belongs), the -ve outputs carry the same signal as the +ve outputs, but in inverted polarity. Connecting the ring terminals of two different outputs together short-circuits the -ve signals. This is unlikely to do any permanent damage, but is not recommended for reasons of both heat dissipation and excessive circulating current.

The headphone amp is a Rane HC 6S. While it has a master stereo input, each channel has a single unbalanced stereo input as well.
These are the inputs I am using.

Let me refine my questions now:

1. How to sum the mono outputs of the FF800 into a single stereo cable? Again, I'm trying to make sure the signal remains stereo all the way to the HP amp.

2. Do I then use TRS cabling for the chain beyond this sum point?

Unfortunately for now, I must use the snake returns for the HP sends. I am unwilling to use 2 channels, as I occasionally need more than 4 HP cues.
I am using two snakes currently: A 16/4 that carries most, if not all the XLR inputs, and a 12/4 that rarely gets used, except in cases where I need to bring in 16+ channels of microphones.
So for now, Boswell, I can use the 2nd snake for primary HP sends to reduce crosstalk.
Since the returns on the snake(s) are balanced 1/4" connections, I would prefer to run all-balanced, or only revert to unbalanced at the cabling between the snake(s) and the amp.

It's clear I'm still getting a better understanding of balanced/unbalanced/stereo...
Again, any help clarifying is much appreciated.!

Tying the negative side or even the shield merely unbalances the circuit.
You could just as easily use TS jacks on the FF outputs if you like and still be able to common both negative outputs to drive the stereo input at the HP end.
A hookup of that Wye is in the HC6 Rane manual

The Rane HC6 headphone amplifier has balanced master inputs with L and R on separate jacks but also individual input jacks for each channel. With the default jumpering, these channel jacks are (unbalanced) stereo, but can be selected as balanced mono by jumper change.

Given that the line outputs of the FF800 are servo balanced, you could take each output via a single balanced return circuit of the snake and then use standard TRS-2xTS insert cables to route a pair of outputs to a stereo (channel) input of the HP amp. There is no combining of signals with this method, and the headphones will reproduce whatever stereo field you present on the pair of FF800 outputs. It's important to maintain the sleeve grounds throughout - don't disconnect them.

Apologies to djmukilteo, as I misunderstood part of what he was saying.

No apologies necessary Boswell, I was wrong!
I think I'm confused the way soapfloats is routing this stuff.
From what I understand soapfloat is routing balanced from FF to the patchbay.
The "Y" cable is connected at the patchbay....two balanced TRS jacks (each FF X+Y) and the single common TRS end patched into the HC6 stereo input feed that runs out via the snake (all TRS) to the HP amp.
So the Y" at the patchbay has to combine the (X+Y) channel pairs correctly at that point.
The HOSA "Y' cable just parallel's each pin together 2 TRS jacks to 1 TRS jack..pin for pin.
The "stereo" feed on the patchbay is not balanced...it is "stereo" which is two unbalanced paths.
So...the "Y" cable at the patchbay needs to common Ring & Sleeve of each channel pair to the Sleeve of the single jack and the Tip's of each channel pair (i.e. X+Y) one to Tip (L) and one to Ring (R) of the HP feed. The snake would then be sending unbalanced "stereo" feeds from there to the HP amp.
I don't think there's any other way to do that. There shouldn't be any noise in those lines out to the HP amp if they're not too long like 50 feet or something. It might be a bonus if the snake had an overall shield on it...
My error was not connecting the shields which will need to be connected together with the Ring sides.
If that makes any sense at all?!?! LOL
If I was right there looking at it I would just wire it up without even thinkng about it, but trying to write it out like this longhand is hard to do!?!
Again I don't think there is a "Y" type cable that does this...but it wouldn't surprise me if someone makes such an animal...it would be fairly easy to rewire the HOSA cable correctly though. You'd just have to cut it apart and make it look like the Rane manual diagram.
I don't think you would need to do the "balanced mono jumper" on the Rane because then you'd end up with no stereo at the Rane inputs. That jumper only makes the input jacks "balanced mono".
But I do know studios use mono headphone feeds rather than stereo, but I don't know if soapfloats wants mono.

Another approach would be to run the snake balanced all the way out to the HP amp.
The you can use the standard TRS patch cables at the patch bay (8 TRS-TRS).
Then build a breakout box to plug the snake into at the HP amp end.
Doing it that way would keep everything balanced all the way out to the HP amp!
Inside the box wire 8 TRS jacks point to point to "stereo unbalanced" TRS pigtail cables coming out of the box that plug directly into the HP amp inputs (TRS male plugs).
You could cut up 2 of your HOSA "Y" cables and use those or just build some custom length pigtail with TRS plugs on the end.
You could also wire 4 TRS jacks on the HP amp side and then use TRS patch cords from the breakout box to the HP amps inputs.
Of course that ends up adding more connection points!
The best thing would be an adapter block that had 2 TRS jacks to a TRS "stereo" plug and get 4 of those.
I think the breakout box method would be my choice with the 4 stereo pigtais!
You could also cut the snake ends but that would muck up the snake for any other use!

Everything after the FF800 outputs is a single cable.
Whether I'm using a patchbay, or connecting directly to the headphone amp, I want the conversion of two mono outputs to a single stereo?/balanced? to happen immediately after the FF800, and before anything else.

Barring confusion on the connections on my patchbay, snake(s), and HP amp (of which I'm pretty sure I know and have correct), the more I'm convinced that whatever the solution, it must occur between the FF800 and the patchbay.

Unless I'm mistaken, this is what I am looking for. And I think I already have the answer?

Basically, I'm trying to take Analog Outs 3-8 (3 pair) + 9/10 (no problems here) and turn them into 3 single + 1 single stereo feed to provide 4 sends.
If I'm going to use the addt'l snake returns, I want them to be available for a 5th, 6th (unlikely more) headphone feed.

And we've been rocking mono for awhile. To provide better cue mixes, we'd like to have stereo feeds available.
The only other solution I've encountered is Link's self-built distribution system (or something like it), and that's just not in the budget right now.

Well, Soapfloats, I think you have two options, depending on how many snake returns you want to use. Consider non-patchbay routes first.

The first method is as I outlined earlier and uses one balanced snake return for each FF800 output, so 8 returns for 4 stereo headphones. This is relatively easy to wire: TRS-TRS cables at the sending end and standard TRS-2xTS insert cables at the HP amp end. The rings of each return get grounded at the remote end by using the TS plugs on the insert cables.

The second method uses the balanced snake returns as a stereo pair. It uses only 4 return channels for 4 stereo headphones, and would be better confined to your second snake. All you would have to do is exchange the TRS-TRS and insert cables from the first method. So you use the TS plugs of the insert cables into each pair of FF800 outputs and its TRS plug into the snake. At the HP amp end, you use a TRS-TRS lead to go from the snake return to the HP amp stereo channel input.

The second method saves 4 snake returns at the expense of running the whole path from the FF800 to the HP amp unbalanced, but this should not matter if the returns are the only usage of the second snake.

Now consider how the patchbay could come into this. If it's a balanced patchbay, then it simply goes in the loop at the point of driving the snake return, and the patchbay jacks become either balanced mono or unbalanced stereo depending on whether you adopt method 1 or 2 above. It would need 8 patchbay jack fields for method 1 and 4 for method 2. An unbalanced patchbay could be used, but it upsets both of the two methods. It would mean running 8 TS jack cables from the FF800 outputs to the patchbay and then using the TS jacks of the insert leads on the patchbay output going to the TRS snake sends.

There is a small variation needed for all the methods when connecting to the FF800 channel 9/10 output, as this is already a TRS jack. You would use an insert cable for method 1 and for unbalanced patchbay and a TRS-TRS cable for method 2 and for balanced patchbay.

No Y-cables!

Wow...I'm completely confused now!
Maybe a wiring diagram of what your trying to do would be in order....
I thought you wanted 4 stereo headphone feeds from the FF800 into the HC6 inputs 1-4?
3/4, 5/6, 7/8, 9/10.
When you say "returns" are you talking about the unbalanced stereo outs off the back (or front) of HC6 back to your patchbay?
Unless you have a headphone amp with separate L and R balanced inputs the only way to send 2 FF800 outputs balanced to the HC6 is to use the 2 Master inputs. The other 6 inputs are unbalanced stereo. The outputs are the same. Also if you use the master inputs and jack into any of the 1-6 inputs you lift the Master input feed from that channel.

My reading was that he wanted to use the individual stereo unbalanced inputs for every HP amp channel. This would switch out any signal coming in via the balanced master inputs. Doing it this way makes everything in the HP monitoring system symmetrical apart from the FF800 9/10 outputs being on a single unbalanced TRS jack and not a balanced jack for each.

I'm also reading snake "returns" in the conventional studio sense of being the channels that run from the control room to the studio. I don't see the need to route anything from the HP amp outputs back to the CR.

OK...."returns" seemed like a confusing wording as headphone feeds are always sends no matter which way they're going...at least in my experience.

So....FF800 outs >>>PB>>>HC6>>>snake out to live room>>>artist phones...right?

All outputs of FF800 should be on the PB (3 thru 10)
All inputs and outputs of HC6 should be on the PB (1-6in/1-6out and the master L/R in)
Snake end in the CR should be on the PB (1-12 or 16)

i would have everything come to the PB (all TRS balanced) and then use the special wired "Y' cable to make the unbalanced "stereo" patch to the TRS of any snake poistion. That way if you wanted to use the FF800, HC6 or the snake(s) differently they would all be available at the PB and everything is standard balanced TRS. Using a switchable or normalized PB would be handy. And you might want to label the HC6 1-6 ins and outs "stereo 1-6"
So FF800 3/4, 5/6 or 7/8 plug in your "Y" cables and patch them to any HC6 in (1-6)
Patch any HC6 out 1-6 straight into a snake channel.
If you want 9 and 10 separate patch those straight to a snake channel (or they could go directly into the master L/R inputs on the HC6) or anywhere else for that matter.

Boswell's "Method 2" most closely matches what I am actually trying to do.
Still a little confusion over proper cabling between FF800 outs and patchbay (it is balanced).
At that point, it's all unbalanced stereo as far as the HP sends are concerned.
It seems you suggest using insert cables?
Let's break that down into T, R, and S. Which two go into the FF800 outs and which one into the patchbay?
We tried this recently, but encountered a lot of white noise in the headphone signal. Perhaps I had the indvd'l insert plugs wrong?

DJ - it's FF800 > PB > Snake returns > HC 6 > artist cans.
The snake(s) carry all signals between the control room (patchbay) and live room.

It is electrically possible to run the unbalanced stereo pairs through a single field of the (balanced) patchbay as though they were a balanced mono channel. However, I think it would be better to run balanced cables from the FF800 outputs to the patchbay, thus using a patchbay field for each output. This gives you better flexibility in case you need to use the outputs for other purposes, and maintains the expected signal structure through the patchbay.

Your cabling would then be 6x TRS-TRS cables from the FF800 outputs to the patchbay inputs plus a TRS-2xTS insert cable to get a pair of unbalanced signals for channels 9/10, and then TRS-2xTS insert cables to go from each pair of patchbay outputs to the appropriate TRS jack socket on the snake. At the HP amp end, all you would need is TRS cables to run from the snake return jacks to the HP amp individual stereo channel inputs.

This arrangement keeps individual channel signals on the patchbay, but cheats the snake returns into thinking they are carrying balanced mono whereas in fact they would have unbalanced stereo. Your required cable count is 7x TRS-TRS cables and 5x TRS-2TS insert cables. Ground connections via the jack sleeves are preserved throughout.

Note that this scheme only works because of the servo-balancing of the FF800 outputs. You can ground the ring or tip of the TRS outputs and the full signal appears on the other with corresponding polarity. It would not work with the majority of electronic-output or non-transformer gear, so take care in connecting other pieces of equipment this way.

I'm assuming your using (2) 1/4" balanced TRS to 1/4" Stereo unbalanced like an "insert" cables?
The sleeve and "cold" of both the (2) 1/4" jacks have to be terminated to the sleeve of the 1/4" single jack and the hot of 1 to tip of the single jack and the hot of the other to ring of the single jack.
Maybe take a meter to your "Y' cable and make sure that's how it is wired. I believe an "Insert" cable is wired that way.
The (2) TRS 1/4" go to the FF800 one to 3 and one to 4 for example and the single 1/4" TRS goes into the stereo input of the HC6.
In your DAW and TotalMix any separate stereo headphone mix you want to make can be setup that way.

If however your using just a straight parallel "Y' cable both the (2) hots will be connected to tip of the single jack, both colds connected to ring of the singe jack and both sleeves connected to the sleeve of the single jack.....that would not be what you want! You would get some nasty signal mix and ground loop noise going on at the HC6.
Again I would run everything balanced from the FF800 through the snake out to the headphone amp and then stereo combine each pair of the snake with your stereo "insert" Y into the HC6 out in the room.
3/4>HC6in1, 5/6>HC6in2, 7/8>HC6in3 and 9/10>HC6in4.

If you use the master L/R inputs on the HC6 and 3 separate feeds you will defeat the 3 separate headphone mix paths, so you might as well use 9/10 as a 4th mix path. If you had all the HC6 inputs including the master inputs on a patchbay you would have the ability to send everybody a master mix by unjacking the separate inputs and patching the main mix to the master HC6 balanced L/R inputs, which would be handy for giving everybody out in the room a full CR mix on their cans. Just a convienence though and I was thinking you had the HC6, PB and FF800 all together a rack in the CR...
I hope that helps (not sure it is LOL)

Thanks fellas, you've both been a big help.

I think I'll follow Boswell's method:
2xTRS out of FF800 into patchbay, then a 2xTS>TRS cable into snake returns.
This will keep it @ 4 snake channels, and keep the returns on the extra, rarely used snake.

I'll consider running separate mono lines independent of the snake(s) in the future.
Soon we'll reclaim our 2nd smaller room from storage, so I'd like to still be able to use the patchbay.
It's rare when I need more than 4 cues, but often I am working both rooms, and it's nice to be able to patch "Mix 2" into the 2nd room.
Hopefully soon, we'll also have an additional 8 analog outs, in which case the patchbay won't be necessary at all.

Thanks again!