A16 to luna

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JoPo
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A16 to luna

Post by JoPo » Sun Jun 03, 2018 8:08 am

Hi !

Since I want to be able to wire any input to any output of my audio mess, I bought several patch bays : Neutrik NYS-SPP-L1. When I patch an A16 output to one of its input, I can see a noise around -71db, which is correct and unhearable. But when I patch that A16 output to one of my Luna input, the noise is -51 , up to -50db ! And that is hearable and anoying because I'd like to use 2 Luna inputs for monitoring.

Does anyone have an idea of what could produce that noise ? All grounds are perfect. Maybe someone had a similar issue.

Thank you !
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Re: A16 to luna

Post by garyb » Sun Jun 03, 2018 10:05 am

that definitely seems like a grounding issue.
maybe a balanced/unbalanced issue. it might be fixed by floating the ground wire between A16 and Luna. make a cable with a trs on one end and a ts on the other. connect the trs tip +, ring - , and sleeve ground. connect the ts end tip+ and sleeve -. leave the ground disconnected on the ts side. connect the trs end to the A16 and the ts end to the Luna.

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Re: A16 to luna

Post by JoPo » Sun Jun 03, 2018 3:27 pm

Thank you, Gary !

But aren't grounds connected between each other via the audio cable, anyway ?

Hem..! Is there somewhere a picture of the cable you're suggesting me to do ? It's not really clear to me ! Don't forget that I'm a poor french guy. Do I understand well : "connect the ts end tip+ and sleeve -" tip and sleeve ... Together ?? :-?

Cables between A16 & patch bays are balanced but between Luna & patch bay, they aren't : I don't know how to make a balanced cable with RCA connection. To have a balanced cable, 2 wires + 1 shield are needed, 2 wires in a rca cable would be useless, no ?
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Re: A16 to luna

Post by garyb » Sun Jun 03, 2018 3:55 pm

"+" is positive, "-" is negative

yes, grounds are usually connected via the cable. that is a good way to have ground loops if the two devices(computer and A16) have different grounds or different grounding schemes.

the problem could be at the patch bay. when connecting balanced to unbalanced the ground usually goes to the negative leg of the audio circuit. this is the reason for balanced lines, to isolate the ground from the audio.

there are a lot of places that ground loops can happen in an audio system with several things plugged into the wall, especially if some are balanced and some are not. an isolation transformer is an alternate way to avoid these issues which often works. https://www.musictri.be/Categories/Behr ... 00/p/P0387

Rane wrote the bible on this a long time ago, but because of computers and everybody thinking they know what they are doing, these basic things that every studio owner/engineer was expected to know have become arcane. http://www.rane.com/note110.html examples 8 and 14 are pretty much what i suggested with number 18 being the same thing using trs to rca.

typically, balanced means a separate positive, negative and ground, while unbalanced means a separate positive and then ground and negative connected together.

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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 12:27 am

Oh ! The Rane link is exactly wht I'm looking for ! Thanks a lot !

So... Are those transformers passive ? Are they called also "DI boxes" ?

And another question : the Rane n°12 seems to be my case = balanced jack output to RCA (so, unbalanced) input ; if I make cables like shown, no transformer needed ? (I wouldn't like to have one transformer like that for 2 Luna inputs !)
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 6:30 am

Another vocabulary problem : are "sleeve" & "shield" synonymous when one is talking about cable ? (I guess they are...)

It's hard for me, poor french guy, to get it : sometimes sleeves seem to be an additionnal plastic (so, insulator) protection and somewhere else, obviously, "sleeve" & "shield" are synonymous !

Anyway, apparently, in the Rane bible, sleeve is shield !
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 7:34 am

I think I get it. Since the patchbay is balanced, the jack cables between the patchbay & the A16 are also balanced, there must be some signal on the balanced ring that arrive on the unbalanced jack. On an unbalanced jack, the ring is the ground shield. I like to understand why.
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 7:59 am

!! Sleeve is the cylinder around where you solder the wires, the component you always forget to put in the cable before to solder, so you must unsolder the cable ? :cry: :evil: What is the sleeve !?! :x :roll:
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 8:03 am

Ah no ! I've got it ! It's the longer part on a male jack !! Pfffff ! :D
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 8:17 am

Ok... Since I plug an unbalanced jack in the balanced patchbay, it's the same as I connect the sleeve and the ring, right ? Now, I'd like to know if the A16 outputs are cross-coupled or aren't... Grrrrgngn mmmmffffmmmffrrrrr. :( :roll:

By reading the A16 manual, I found a nice page (11-12) about how to connect balanced to unbalanced stuff ! Excellent ! I think I gonna do like explained there !

After several hours to study all those infos, I'm concluding that I must use a balanced male jack in the patchbay (so my RCA - jack cable is not good !), connect the RCA & jack tips, jack ring & RCA (called sleeve too ?) and if the A16 outputs are cross-coupled, the jack ring to the sleeve & the shield, if they aren't (Maybe, Gary, do you know that, the info is not in the manual), jack ring to RCA sleeve, jack sleeve to cable shield but NOT in the RCA side.
Is that correct (I gonna try on one luna input) ? Would I need a transformer anyway (I hope no !) ?

If it works, I've got 32 cables to modify ! Luna outputs to a16 inputs have the same issue, I guess. But there is much less noise in that direction.
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Re: A16 to luna

Post by garyb » Mon Jun 04, 2018 9:16 am

the three parts of a balanced phone jack are called tip(the rip), ring(the thinner section behind the tip) and sleeve(the longer section behind the ring).

no, a direct box is for converting a high impedance signal like an unbalanced signal from a synth, to a low impedance balanced connection, like on a microphone preamp. the purpose of this is because hiZ lines can go about 20feet maximum before signal degradation(18'6" actually). loZ can travel hundreds of feet before losing signal.

the transformer involved here, is a balancing or isolation transformer. it is so that the integrity of the ground is kept without the two systems actually touching each other, since a transformer is made of windings of wire and signal flow can be "induced" by putting two windings next to each other. no, it's not absolutely needed, but it's the quick fix. the other link was an example of this type of transformer.

don't worry about the direction. just use the wiring example and have the proper ends on each side. the method of killing ground loops via "floating" the ground via wiring may or may not work. it usually does. this way, the signal is transmitted, but the shield or ground which protects the signal from interference from external noise and radiation will be present the length of the wire, but it won't connect the two systems. when different grounding systems are used and then connected together, the hum of the electricity itself can be made to travel along the audio path, which is a disaster.

no, you don't have 32 cables to modify/make. just the two that go to the Luna inputs.

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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 9:49 am

I've got 2 Luna's ! At least for the 16 inputs, no ?

The fist try is a disaster ! (the connection I said in tmy last message, the n°18 in rane's) It's even worst ! Should I try by connecting the jack ring to the shield ?
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Re: A16 to luna

Post by garyb » Mon Jun 04, 2018 11:22 am

no. the ADAT i/o would not be affected by this.

the cable you make will be used oppositely to the example. if it did not work, then you need to try another solution after you verify that you made the connection properly. connecting ring to shield is EXACTLY the same as using an unbalanced cable.

you have noisy inputs on the ADAT i/o? if so, then the problem is happening before the Luna.

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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 11:34 am

Well.... Must notice that it doesn't work at all on my system ! I believe I should install some transformer... Pfffff...

there is no ADAT, the A16 is connected to the Xite via z-link.
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 11:36 am

I have no idea of what to try next !
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 12:23 pm

The strange thing is that by connecting directly an A16 output to a Luna input with a simple unbalaced cable, the noise is still loud. Frpm -50db, it goes to -54db which is still too bad.
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Re: A16 to luna

Post by garyb » Mon Jun 04, 2018 12:38 pm

JoPo wrote:
Mon Jun 04, 2018 11:34 am
Well.... Must notice that it doesn't work at all on my system ! I believe I should install some transformer... Pfffff...

there is no ADAT, the A16 is connected to the Xite via z-link.
what about the 16 inputs into your two Luna cards that you were talking about making cable for?!!! your XITE is not involved.

di you know how to solder correctly? i am not being nasty or mean, i just ask because you don't seem familiar with these things.

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Re: A16 to luna

Post by garyb » Mon Jun 04, 2018 12:44 pm

JoPo wrote:
Mon Jun 04, 2018 12:23 pm
The strange thing is that by connecting directly an A16 output to a Luna input with a simple unbalanced cable, the noise is still loud. Frpm -50db, it goes to -54db which is still too bad.
not strange AT ALL. this is exactly what i was pointing to.

sure, you can try a hum suppressor(transformer). the easiest cheapest one is the Behringer i linked to. that is simply something that you should own, anyway.

this problem is not even necessarily related to your cards. if the wiring in the house or studio you are in isn't grounded properly, you'll have all kinds of problems. if the computer that the Luna cards are in is not grounded properly, that will be problems. what is the normal level of noise when any other device is connected to the Luna inputs? there is no sense in simply running in circles... :)

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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 1:11 pm

garyb wrote:
Mon Jun 04, 2018 12:38 pm
what about the 16 inputs into your two Luna cards that you were talking about making cable for?!!! your XITE is not involved.

di you know how to solder correctly? i am not being nasty or mean, i just ask because you don't seem familiar with these things.
I'm not familiar with all that audio interconnection mess ! But with soldering, there is no problem !
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Re: A16 to luna

Post by JoPo » Mon Jun 04, 2018 1:20 pm

garyb wrote:
Mon Jun 04, 2018 12:44 pm
not strange AT ALL. this is exactly what i was pointing to.

sure, you can try a hum suppressor(transformer). the easiest cheapest one is the Behringer i linked to. that is simply something that you should own, anyway.

this problem is not even necessarily related to your cards. if the wiring in the house or studio you are in isn't grounded properly, you'll have all kinds of problems. if the computer that the Luna cards are in is not grounded properly, that will be problems. what is the normal level of noise when any other device is connected to the Luna inputs? there is no sense in simply running in circles... :)
Well. The ground in my house is fine. I've got an electric car which would refuse to charge if the ground is not absolutely perfect. All my audio mess is connected to the ground with all chassis. I checked that 100 times. Only the lunas have some noise at their inputs but it became louder by connecting them to the A16 output.
By reading the luna specs, they have unbalanced I/O. (Which is obvious with RCA sockets)

Does the behringer box work is both direction ?
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