Rane TTM56s into RME UFX ground issue?

[Chip Borton]

Hi All,

Just took delivery of a Rane TTM56s mixer and hooked it into
my RME UFX line inputs with an unbalanced cable and got a 60Hz
sound along with that hashy high frequency stuff.

This mixer replaced my old cheap mixer which is unbalanced all
the way through which was quiet as a mouse.

Since the TTM56s has both balanced and unbalanced outputs I
then tried using balanced cables and the noise went away.

I then tried using both the unbalanced cables into another
available input pair of the UFX and found that the unbalanced input
was quiet too.

So somehow having a balanced cable between the two makes everything
happy (even for the unbalanced pair).

Just for grins, I then tried a ground lifter on the Rane with
just the unbalanced cables into the audio interface, no noise.
Don't worry, the ground lifter is not staying, it was just a test.
The old mixer was only a two prong AC plug.

So, I have some grounding issue I was hoping you guys might
have some insight on. For the amount of dollars thing cost
and considering my old unbalanced cheapish mixer didn't have
any issues, it's a little annoying.

I have all equipment including computer and outboard gear
connected to the same AC circuit.

I guess my options are:

1: The Rane has a deign flaw and needs to be sent back.
2: The Rane is a dud from the factory and needs to be sent back.
3: Just use the balanced outputs and don't worry about it.
4: Find some other fix that would allow me to use unbalanced without noise.


Thanks,
Chip

[[email protected]]

>
> I guess my options are:
>
> 1: The Rane has a deign flaw and needs to be sent back.
> 2: The Rane is a dud from the factory and needs to be sent back.
> 3: Just use the balanced outputs and don't worry about it.
> 4: Find some other fix that would allow me to use unbalanced without noise.
>
>
> Thanks,
> Chip

somewhat ironic that your equipment issue is Rane, they have some excellent tutorials re the subject, here is just one, you can search for some others

http://www.rane.com/note110.html

It is hard to troubleshoot ground problems without being there, but it sounds like you have a classic ground loop. First thing is to verify that it is not just a bad cable. Next....Does the hum change if you move the route of the power cables and interconnect cables? It is possible that the ground loop made by these, even though it is a small area loop if they are plugged into the same AC source, the loop may be picking up the magnetic field from a power transformer in one of the pieces of gear. Try moving the cables around. If you can't break the loop, minimize it's area. Or as a test run a heavy ground strap betwen the chassis of the 2 units. The best fix is to break the loop using balanced signals (why don't you want to use these) or get a small audio transformer to put in the path.

Mark

[Scott Dorsey]

Chip Borton > wrote:
>
>So, I have some grounding issue I was hoping you guys might
>have some insight on. For the amount of dollars thing cost
>and considering my old unbalanced cheapish mixer didn't have
>any issues, it's a little annoying.

Kludge's First Law: Everything should have one and only one ground path
to everything else in the chain.

Kludge's Second Law: you can lift signal grounds with impunity, but never
safety grounds.

The consequence of the second law is that if you have an unbalanced output,
you can connect it into pins 2 and 3 of a balanced input.... now the two
devices do not share a common ground but the source device does not need
any additional electronics. This works only as long as the noise is within
the range of the input stage; if the noise causes the input stage to clip
then all bets are off. (This is why transformers are your friend... no
amount of common mode noise will make them clip.)

If you absolutely have to go from an unbalanced output to an unbalanced input,
an isolation transformer will allow you to do this without common grounds
between both sides. Edcor makes a decent cheap one, Jensen makes a much
better expensive one.

There is actually a very good discussion of this on the Rane website.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Frank Stearns]

(Scott Dorsey) writes:

snips

>Kludge's Second Law: you can lift signal grounds with impunity, but never
>safety grounds.

Heed this excellent (and life-protecting) advice.

I would only add that on the lifts for the signal grounds, an RF shunt is probably
good to have.

Per Jensen for this purpose I use a 100V 10nf cap in series with a 51 ohm 1/4w
resistor across the signal ground lift switch. When the switch is open, RF still has
a path to ground, but not bad ole ground loop currents. Retrofitted the splitter and
all the DIs with this 10+ years ago; never, ever had a problem. Even been in a few
venues where I was told there would be buzz issues; not so. (Even startled one PA
tech who wondered what kind of deal I'd made with the devil.)

Frank
Mobile Audio
--

[Dave Plowman (News)]

In article >,
Frank Stearns > wrote:
> >Kludge's Second Law: you can lift signal grounds with impunity, but
> >never safety grounds.

> Heed this excellent (and life-protecting) advice.

RCDs not universal?

--
*Why isn't there mouse-flavoured cat food?

Dave Plowman London SW
To e-mail, change noise into sound.

[Don Pearce[_3_]]

On Wed, 18 Feb 2015 19:28:48 +0100, Mike Rivers >
wrote:

>On 2/18/2015 2:42 PM, Chip Borton wrote:
>> Just took delivery of a Rane TTM56s mixer and hooked it into
>> my RME UFX line inputs with an unbalanced cable and got a 60Hz
>> sound along with that hashy high frequency stuff.
>
>A couple of assumptions:
>
>1 - the interface is connected to a computer
>2 - the computer is connected to the Internet
>3 - the Internet connection is via TV cable
>
>1+2+3=6-ty cycle hum and lots of hash

I don't quite get 3. There is no TV involved in the Internet as far as
I know.
The Internet connections is via twisted Cat 6.

d

[[email protected]]

..
> >
> >A couple of assumptions:
> >
> >1 - the interface is connected to a computer
> >2 - the computer is connected to the Internet
> >3 - the Internet connection is via TV cable
> >
> >1+2+3=6-ty cycle hum and lots of hash
>
> I don't quite get 3. There is no TV involved in the Internet as far as
> I know.
> The Internet connections is via twisted Cat 6.
>
> d

cable modem?

Mark

[Scott Dorsey]

Dave Plowman (News) > wrote:
>In article >,
> Frank Stearns > wrote:
>> >Kludge's Second Law: you can lift signal grounds with impunity, but
>> >never safety grounds.
>
>> Heed this excellent (and life-protecting) advice.
>
>RCDs not universal?

No. And to be honest, it's nice to have an RF system ground too, and PE
provides that to some extent.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers[_2_]]

On 2/18/2015 9:23 PM, wrote:
> cable modem?

That's what I was referring to, but I don't think the device is actually
a modem, people just call it one. Cable TV grounds are notorious for
being noisy, and that could get through to the mixer via the interface
ground.

When using a balanced connection, noise on the cable shield gets induced
into the two signal conductors pretty much equally, but since they're
going into inverting and non-inverting inputs, the induced noise nearly
cancels. But with an unbalanced connection, noise on the ground gets
coupled right to the hot signal lead and acts like another signal.

--
For a good time, visit http://mikeriversaudio.wordpress.com

[JackA]

On Wednesday, February 18, 2015 at 4:45:50 PM UTC-5, Mike Rivers wrote:
> On 2/18/2015 9:23 PM, wrote:
> > cable modem?
>
> That's what I was referring to, but I don't think the device is actually
> a modem, people just call it one. Cable TV grounds are notorious for
> being noisy, and that could get through to the mixer via the interface
> ground.
>
> When using a balanced connection, noise on the cable shield gets induced
> into the two signal conductors pretty much equally, but since they're
> going into inverting and non-inverting inputs, the induced noise nearly
> cancels. But with an unbalanced connection, noise on the ground gets
> coupled right to the hot signal lead and acts like another signal.

Oh, you mean like with 300 ohm balanced twin-lead??

That was the good old days of decent TV transmissions, before this digital crap that has one too many glitches. Even HD Radio, now they are begging FCC for greater transmitting power. Well thought out, huh?

Jack
>
> --
> For a good time, visit http://mikeriversaudio.wordpress.com

[Dave Plowman (News)]

In article >,
Scott Dorsey > wrote:
> Dave Plowman (News) > wrote:
> >In article >,
> > Frank Stearns > wrote:
> >> >Kludge's Second Law: you can lift signal grounds with impunity, but
> >> >never safety grounds.
> >
> >> Heed this excellent (and life-protecting) advice.
> >
> >RCDs not universal?

> No. And to be honest, it's nice to have an RF system ground too, and PE
> provides that to some extent.

Thing is if you sell equipment with unbalanced in/outs which share the
signal ground with the mains safety earth, you're going to get a hum loop
if they are connected to another using the same idea. Even if you daisy
chained two identical ones.

--
*Yes, I am an agent of Satan, but my duties are largely ceremonial

Dave Plowman London SW
To e-mail, change noise into sound.

[Scott Dorsey]

Dave Plowman (News) > wrote:
>In article >,
> Scott Dorsey > wrote:
>> Dave Plowman (News) > wrote:
>> >In article >,
>> > Frank Stearns > wrote:
>> >> >Kludge's Second Law: you can lift signal grounds with impunity, but
>> >> >never safety grounds.
>> >
>> >> Heed this excellent (and life-protecting) advice.
>> >
>> >RCDs not universal?
>
>> No. And to be honest, it's nice to have an RF system ground too, and PE
>> provides that to some extent.
>
>Thing is if you sell equipment with unbalanced in/outs which share the
>signal ground with the mains safety earth, you're going to get a hum loop
>if they are connected to another using the same idea. Even if you daisy
>chained two identical ones.

Yes! And this is the kind of crap people deal with in the consumer world!
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers]

On Thursday, February 19, 2015 at 12:48:19 AM UTC+1, JackA wrote:

> Oh, you mean like with 300 ohm balanced twin-lead??

Oy! No, not even close.

--
For a good time, visit http://mikeriversaudio.wordpress.com

[Dave Plowman (News)]

In article >,
Scott Dorsey > wrote:
> >Thing is if you sell equipment with unbalanced in/outs which share the
> >signal ground with the mains safety earth, you're going to get a hum
> >loop if they are connected to another using the same idea. Even if you
> >daisy chained two identical ones.

> Yes! And this is the kind of crap people deal with in the consumer
> world!

There's an easy enough answer. In the UK there's a BS covering double
insulation. Whereby there is no requirement to connect a steel chassis to
mains ground. Alternately, you don't have a DC signal ground to mains
ground connection. Of course that needs a power supply where any fault
condition can't result in mains appearing on the signal ground.

This has been the case with pretty well all domestic equipment for many
many years. Of course a balanced connection is the other way - but this is
pretty much restricted to pro equipment in the UK.

--
*If all is not lost, where the hell is it?

Dave Plowman London SW
To e-mail, change noise into sound.

[Scott Dorsey]

Dave Plowman (News) > wrote:
>In article >,
> Scott Dorsey > wrote:
>> >Thing is if you sell equipment with unbalanced in/outs which share the
>> >signal ground with the mains safety earth, you're going to get a hum
>> >loop if they are connected to another using the same idea. Even if you
>> >daisy chained two identical ones.
>
>> Yes! And this is the kind of crap people deal with in the consumer
>> world!
>
>There's an easy enough answer. In the UK there's a BS covering double
>insulation. Whereby there is no requirement to connect a steel chassis to
>mains ground. Alternately, you don't have a DC signal ground to mains
>ground connection. Of course that needs a power supply where any fault
>condition can't result in mains appearing on the signal ground.

That solves part of the problem and it eliminates the largest ground loop,
but it doesn't eliminate all of them. Even if there is no PE connection
to anything, if you have left and right RCA cables between two components,
the two shields of the two cables are providing two ground paths between
them. Physically the loop area is very small, but it's nonzero. And the
more connections between components you get, the more this becomes a problem.

>This has been the case with pretty well all domestic equipment for many
>many years. Of course a balanced connection is the other way - but this is
>pretty much restricted to pro equipment in the UK.

The place where these issues become really catastrophic is with phono inputs.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Chip Borton]

On 2/18/2015 7:14 AM, wrote:

> somewhat ironic that your equipment issue is Rane, they have some excellent tutorials re the subject, here is just one, you can search for some others
>
> http://www.rane.com/note110.html
>
> It is hard to troubleshoot ground problems without being there, but it sounds like you have a classic ground loop. First thing is to verify that it is not just a bad cable. Next....Does the hum change if you move the route of the power cables and interconnect cables? It is possible that the ground loop made by these, even though it is a small area loop if they are plugged into the same AC source, the loop may be picking up the magnetic field from a power transformer in one of the pieces of gear. Try moving the cables around. If you can't break the loop, minimize it's area. Or as a test run a heavy ground strap betwen the chassis of the 2 units. The best fix is to break the loop using balanced signals (why don't you want to use these) or get a small audio transformer to put in the path.
>
> Mark
>
>
>

Ok, thanks Mark, Scott, Frank, Dave, Mike, Don for your deep and
insightful responses. I have looked at the Rane tech notes in the past
but did not think to revisit.

First of all sorry for the late response. I realized after I posted that
I did not think things all the way through. Technically speaking I had
ground loops galore that I did not think about. I have my main room
where I have most of my stuff plugged in but I also have a talent room
with headphone amps and a second HDMI monitor hooked up for ADR talent.
I had an amp hooked into a different AC circuit as well.

I also had my main room hooked up to the external cable for TV. I bought
new AC power cables to run into the talent room and disconnected the
broadband connection. I fixed all the ground loops I had and
disconnected the broadband.

Mark nailed it in his first sentence. I had a bad unbalanced RCA cable.
Replaced the cable and all was good.

Just as a test I put all my ground loops back the way they were and
everything was OK. I don't know how a simple RCA cable could be the
culprit but that's what it was all along.

Anyways, I am a happy camper, no noise and any future ground loop issues
should be fixed as well.

Thanks All.

Chip

[Scott Dorsey]

Chip Borton > wrote:
>
>First of all sorry for the late response. I realized after I posted that
>I did not think things all the way through. Technically speaking I had
>ground loops galore that I did not think about. I have my main room
>where I have most of my stuff plugged in but I also have a talent room
>with headphone amps and a second HDMI monitor hooked up for ADR talent.
>I had an amp hooked into a different AC circuit as well.

This is all fine as long as you have your signal grounds lifted so that
there is only one ground path from one thing to another. Ground lift
adaptors are not a big deal and for a permanent install you can always
cut the connection inside the cable and mark the cable.

>I also had my main room hooked up to the external cable for TV. I bought
>new AC power cables to run into the talent room and disconnected the
>broadband connection. I fixed all the ground loops I had and
>disconnected the broadband.

The broadband connection is fine if it's ethernet because unshielded
ethernet carries no ground. It is one hell of an ingenious design and
specifically designed to avoid having to worry about ground connections.
Everything is transformer-isolated! It's great.

The TV cable connection is an evil source of massive ground noise, but
that noise should be stopping at your cable modem if the only connection
out of the cable modem is ethernet (which it should be).

>Mark nailed it in his first sentence. I had a bad unbalanced RCA cable.
>Replaced the cable and all was good.

THIS is likely to be the opposite of a ground loop! Something is not
grounded when it needs to be, because the shield on the cable is broken
when it should not have been.

>Just as a test I put all my ground loops back the way they were and
>everything was OK. I don't know how a simple RCA cable could be the
>culprit but that's what it was all along.

First rule: everything gets one and only one ground path to everything else.
Never two, and never zero.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Mike Rivers[_2_]]

On 3/23/2015 11:47 AM, Scott Dorsey wrote:
> The broadband connection is fine if it's ethernet because unshielded
> ethernet carries no ground. It is one hell of an ingenious design and
> specifically designed to avoid having to worry about ground connections.

But there's shielded Ethernet cable - I forget which CAT designation it
is. Someone might be using it as a "premium" cable. And, design specs
notwithstanding, it's not uncommon for a noise problem to go away when
the Ethernet cable is unplugged from the computer.

--
For a good time, visit http://mikeriversaudio.wordpress.com

[mark lewis[_2_]]

On Mon, 23 Mar 2015, Mike Rivers wrote to All:

MR> On 3/23/2015 11:47 AM, Scott Dorsey wrote:
> The broadband connection is fine if it's ethernet because unshielded
> ethernet carries no ground. It is one hell of an ingenious design and
> specifically designed to avoid having to worry about ground connections.

MR> But there's shielded Ethernet cable - I forget which CAT
MR> designation it is.

it is all... regular ""ethernet cable"" is UTP, Unshielded Twisted Pair... shielded is STP, Shielded Twisted Pair... you can get STP CAT-5e and UTP CAT-5e... or CAT-6 or CAT-3 or etc... the only difference is the shield so look for STP instead of UTP if y
)\/(ark
a networking guy

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| Standard disclaimer: The views of this user are strictly his own.

[jason]

On 23 Mar 2015 14:00:18 -0400 "Scott Dorsey" > wrote in
article >
>
And you can often telescope the shield on one end to
> prevent ground loops.....
> --scott

Slightly OT .. during the summer of 1968, I was in college and stayed on
campus for the summer with a job building electronic gizmos for
experimentalists in the bio and psych departments. I spent my evenings
rebuilding our campus radio station; we had a smallish grant for new
consoles and other gear (Ampex tape decks - finally!). There were two
control rooms, A and B (naturally). I found some telco "christmas tree"
contact blocks and some surplus 1/4" patch panels. I hooked up everything
between A & B with shielded twisted pair and grounded both ends... You
can guess what happened when I turned everything on the first time :-(

Fortunately, it didn't take very long to snip half the grounds.

Jason

[Mike Rivers[_2_]]

On 3/23/2015 9:40 PM, Jason wrote:
.. during the summer of 1968, . . . I spent my evenings
> rebuilding our campus radio station; we had a smallish grant for new
> consoles and other gear (Ampex tape decks - finally!). There were two
> control rooms, A and B (naturally). I found some telco "christmas tree"
> contact blocks and some surplus 1/4" patch panels. I hooked up everything
> between A & B with shielded twisted pair and grounded both ends... You
> can guess what happened when I turned everything on the first time :-(

In 1968, that was the popular solution. Today, things are quiet enough
and the EMI environment has become enough more polluted so that noise
creeps in through the hole you make by breaking the continuous
end-to-end shield. Today, you use balanced connections and fix Pin 1
problems in order to get rid of objectionable hum.

--
For a good time, visit http://mikeriversaudio.wordpress.com