TECH: Signal loss between mixer and amps

[Luther Bell]

OK, here's my initial question. How much signal loss can a bad ground
cause?

Here's the background:
I am working on a proposal that I wrote up for a theater at a
college. I am rewiring their sound booth because everything was just
too crazy and random. I ripped everything out of the punch blocks and
then rewired it. I rearranged the patch bays, and I rearranged the
booth. Currently I have everything re-punched in the blocks and I
have everything hooked back up. I'm in the process of testing the
system to make sure everything works because we have a show in two
weeks. Almost everything works. My only problem is the signal loss.
I patch the CD player through to the mixer and try to run it through
the speakers. I end up getting 1/4 of the output that I should. It's
very quiet and muffled. I have tried troubleshooting and I can't
figure out what the main problem is. If there was a bad ground
somewhere, would/could that be the problem or is it something else? I
think that I'm just going to run a cable straight from the mixer outs
to the amps so that it works for this show and then I'm going to rip
it apart and try and fix the problem again, but I want to find the
answer. So if you think you can help, I'd love your opinion...Thanks
-Luther

[LeBaron & Alrich]

Luther Bell wrote:

> OK, here's my initial question. How much signal loss can a bad ground
> cause?

> Here's the background:
> I am working on a proposal that I wrote up for a theater at a
> college. I am rewiring their sound booth because everything was just
> too crazy and random. I ripped everything out of the punch blocks and
> then rewired it. I rearranged the patch bays, and I rearranged the
> booth. Currently I have everything re-punched in the blocks and I
> have everything hooked back up. I'm in the process of testing the
> system to make sure everything works because we have a show in two
> weeks. Almost everything works. My only problem is the signal loss.
> I patch the CD player through to the mixer and try to run it through
> the speakers. I end up getting 1/4 of the output that I should. It's
> very quiet and muffled. I have tried troubleshooting and I can't
> figure out what the main problem is. If there was a bad ground
> somewhere, would/could that be the problem or is it something else? I
> think that I'm just going to run a cable straight from the mixer outs
> to the amps so that it works for this show and then I'm going to rip
> it apart and try and fix the problem again, but I want to find the
> answer. So if you think you can help, I'd love your opinion...Thanks
> -Luther

Why do you think it's a bad ground? Have you followed the signal along
its route with a volt meter to see what's what where? It could be plenty
of things, and I don't see enough solid info in your comments to point
at something specific.

Is the output of the CD player known to be good? Is the mixer output
known to be good? Have you doublechecked, with a meter not with
eyeballs, all those wires you disconnected and then reconnected?

How can you "rip it apart and try and fix the problem again" if you
haven't found out what is the problem? Did this system function properly
before you ripped it apart? A bunch of cables can be arrayed in an
unattractive mess and still be effectively connected and perform the
intended functions.

You must follow step-by-step troubleshooting procedures to get at the
problem, and that precludes just ripping things apart.

--
hank alrich * secret mountain
audio recording * music production * sound reinforcement
"If laughter is the best medicine let's take a double dose"

[LeBaron & Alrich]

Luther Bell wrote:

> OK, here's my initial question. How much signal loss can a bad ground
> cause?

> Here's the background:
> I am working on a proposal that I wrote up for a theater at a
> college. I am rewiring their sound booth because everything was just
> too crazy and random. I ripped everything out of the punch blocks and
> then rewired it. I rearranged the patch bays, and I rearranged the
> booth. Currently I have everything re-punched in the blocks and I
> have everything hooked back up. I'm in the process of testing the
> system to make sure everything works because we have a show in two
> weeks. Almost everything works. My only problem is the signal loss.
> I patch the CD player through to the mixer and try to run it through
> the speakers. I end up getting 1/4 of the output that I should. It's
> very quiet and muffled. I have tried troubleshooting and I can't
> figure out what the main problem is. If there was a bad ground
> somewhere, would/could that be the problem or is it something else? I
> think that I'm just going to run a cable straight from the mixer outs
> to the amps so that it works for this show and then I'm going to rip
> it apart and try and fix the problem again, but I want to find the
> answer. So if you think you can help, I'd love your opinion...Thanks
> -Luther

Why do you think it's a bad ground? Have you followed the signal along
its route with a volt meter to see what's what where? It could be plenty
of things, and I don't see enough solid info in your comments to point
at something specific.

Is the output of the CD player known to be good? Is the mixer output
known to be good? Have you doublechecked, with a meter not with
eyeballs, all those wires you disconnected and then reconnected?

How can you "rip it apart and try and fix the problem again" if you
haven't found out what is the problem? Did this system function properly
before you ripped it apart? A bunch of cables can be arrayed in an
unattractive mess and still be effectively connected and perform the
intended functions.

You must follow step-by-step troubleshooting procedures to get at the
problem, and that precludes just ripping things apart.

--
hank alrich * secret mountain
audio recording * music production * sound reinforcement
"If laughter is the best medicine let's take a double dose"

[Luther]

> Why do you think it's a bad ground? Have you followed the signal along
> its route with a volt meter to see what's what where? It could be plenty
> of things, and I don't see enough solid info in your comments to point
> at something specific.

I have no proof that it even has the chance of being a bad ground. That's
just where I'm starting. We've had problems with bad grounds there before
so I was just choosing that as a starting point.

> Is the output of the CD player known to be good? Is the mixer output
> known to be good? Have you double-checked, with a meter not with
> eyeballs, all those wires you disconnected and then reconnected?

The CD player is actually a DVD player that plays CDs. I know, I know. The
tech director bought it over the summer because our 5-disc CD player crapped
out the year before. I don't know why he bought a DVD player, but he won't
take it back because it works just fine (in his mind). And another
interesting development with the "CD player". I was playing a CD a couple
of days ago and the music started to speed up. It's happened twice at two
different times with two different cds. But the TD won't take it to get
fixed because we have a show in two weeks and he doesn't want to possibly
leave us with out a "cd player". The output of the mixer is also good. It
works just fine when I sire it straight into the amps.

> How can you "rip it apart and try and fix the problem again" if you
> haven't found out what is the problem? Did this system function properly
> before you ripped it apart? A bunch of cables can be arrayed in an
> unattractive mess and still be effectively connected and perform the
> intended functions.

The system functioned alright before I ripped it apart. I rewired the
system partly to fix the problems and partly because the system was put
together in a confusing way and my goal was to rearrange it into a
configuration that was easier and better to use. There was the initial
installation of the system and as equipment was purchased, the additions
were kind of just thrown on top of everything and after a while it had just
gotten worse and worse so my proposal was to clean everything up and fix the
problems in the process.

-Luther

"LeBaron & Alrich" > wrote in message
. ..
> Luther Bell wrote:
>
> > OK, here's my initial question. How much signal loss can a bad ground
> > cause?
>
> > Here's the background:
> > I am working on a proposal that I wrote up for a theater at a
> > college. I am rewiring their sound booth because everything was just
> > too crazy and random. I ripped everything out of the punch blocks and
> > then rewired it. I rearranged the patch bays, and I rearranged the
> > booth. Currently I have everything re-punched in the blocks and I
> > have everything hooked back up. I'm in the process of testing the
> > system to make sure everything works because we have a show in two
> > weeks. Almost everything works. My only problem is the signal loss.
> > I patch the CD player through to the mixer and try to run it through
> > the speakers. I end up getting 1/4 of the output that I should. It's
> > very quiet and muffled. I have tried troubleshooting and I can't
> > figure out what the main problem is. If there was a bad ground
> > somewhere, would/could that be the problem or is it something else? I
> > think that I'm just going to run a cable straight from the mixer outs
> > to the amps so that it works for this show and then I'm going to rip
> > it apart and try and fix the problem again, but I want to find the
> > answer. So if you think you can help, I'd love your opinion...Thanks
> > -Luther
>
> Why do you think it's a bad ground? Have you followed the signal along
> its route with a volt meter to see what's what where? It could be plenty
> of things, and I don't see enough solid info in your comments to point
> at something specific.
>
> Is the output of the CD player known to be good? Is the mixer output
> known to be good? Have you doublechecked, with a meter not with
> eyeballs, all those wires you disconnected and then reconnected?
>
> How can you "rip it apart and try and fix the problem again" if you
> haven't found out what is the problem? Did this system function properly
> before you ripped it apart? A bunch of cables can be arrayed in an
> unattractive mess and still be effectively connected and perform the
> intended functions.
>
> You must follow step-by-step troubleshooting procedures to get at the
> problem, and that precludes just ripping things apart.
>
> --
> hank alrich * secret mountain
> audio recording * music production * sound reinforcement
> "If laughter is the best medicine let's take a double dose"

[Richard Crowley]

"Luther" > wrote in message
...
> > Why do you think it's a bad ground? Have you followed the signal along
> > its route with a volt meter to see what's what where? It could be plenty
> > of things, and I don't see enough solid info in your comments to point
> > at something specific.
>
> I have no proof that it even has the chance of being a bad ground. That's
> just where I'm starting. We've had problems with bad grounds there before
> so I was just choosing that as a starting point.

Doesn't seem very productive to just choose a possible problem.
You are starting over and must troubleshoot as if it were a new
installataion (which it IS!)

>
> > Is the output of the CD player known to be good? Is the mixer output
> > known to be good? Have you double-checked, with a meter not with
> > eyeballs, all those wires you disconnected and then reconnected?
>
> The CD player is actually a DVD player that plays CDs.

Doesn't seem relevant that it is a DVD player and not a straight
CD player (unless you suspect some other interaction with video,
etc.) Does the player put out nominal output when you plug it in
so another system?

> The output of the mixer is also good. It
> works just fine when I sire it straight into the amps.

Good, you are doing step-by-step troubleshooting.
It would almost seem like you have found the problem.

Does the system work properly through the mixer with
OTHER inputs (other than the CD/DVD player?) That
would seem like the key piece of data at this point. It
would establish whether it is really the wiring between
the mixer and the amps, or something else.

[Arny Krueger]

"Luther Bell" > wrote in message
om

> OK, here's my initial question. How much signal loss can a bad ground
> cause?

Some or none, depending on the bad ground.

> Here's the background:

> I am working on a proposal that I wrote up for a theater at a
> college. I am rewiring their sound booth because everything was just
> too crazy and random. I ripped everything out of the punch blocks and
> then rewired it. I rearranged the patch bays, and I rearranged the
> booth.


> Currently I have everything re-punched in the blocks and I
> have everything hooked back up.

That was probably a mistake. IME the best way to work through non-trivial
wiring projects is to proceed incrementally. Wire up a few things, see if
they work, wire up a few more things like what you just wired up, see if it
works, etc.

>I'm in the process of testing the
> system to make sure everything works because we have a show in two
> weeks. Almost everything works. My only problem is the signal loss.

I wouldn't call that *working*. What does work?

> I patch the CD player through to the mixer and try to run it through
> the speakers. I end up getting 1/4 of the output that I should. It's
> very quiet and muffled.

So what happens if you plug a mic into a mic input on the mixer and talk
into it?

>I have tried troubleshooting and I can't
> figure out what the main problem is. If there was a bad ground
> somewhere, would/could that be the problem or is it something else?

Bad grounds usually have symptoms along the lines of hum and noise.

> I think that I'm just going to run a cable straight from the mixer outs
> to the amps so that it works for this show and then I'm going to rip
> it apart and try and fix the problem again, but I want to find the
> answer.

I can understand routing console input wiring through a patch panel better
than routing monitor amp wiring through it.

Does your board have a headphone jack? How does it work?

>So if you think you can help, I'd love your opinion...Thanks

Your comments about DVD versus CD players seem to be misguided. The general
problem is called interfacing consumer audio gear to an audio production
mixer, and its the same for consumer DVD players, consumer CD players,
consumer cassette players, you name it. If anything CD & DVD players are
among the consumer audio devices with higher level outputs than average. At
the level of problems you are working with right now, the audio output of a
DVD player is indistinguishable from the audio output of a CD player.

[LeBaron & Alrich]

Luther > wrote:

> The output of the mixer is also good. It
> works just fine when I sire it straight into the amps.

How do you make that good connection? Is it via a completely separate
line that is independent of the patchbay, or is it via another set of
patchbay connections?

How about the rest of the patchbay? Are all of the other
interconnections working properly?

A thought: are you trying to run a -10 dB signal dowhn a long unbalanced
line into a balanced +4 dB input?

How about this: what is the amp? What is the mixer? How far from the
mixer and patchbay is the amplifier input?

--
ha

[P Stamler]

Questions to ask:

If you run any other source through the mixer, does it give a decent level on
the mixer's own meters? And does it then give decent level from the
amp/speakers?

If the answers to those questions are Yes and No respectively, then the problem
is the connection between the mixer and the amplifier. If so, the next question
would be, is this a balanced system (3-wire connection)? If so, it's possible
that one leg of the balanced connection is out, either shorted to ground or
open, which could give you a 6dB drop in level at the amplifier, assuming
electronically-balanced outputs on the mixer rather than transformer-balanced
and floating.

On the other hand, if you get great mixer and amplifier levels with any other
signal, but crummy levels with the DVD player, then it either is inherently too
low-level for this application, or not working properly. So...what kind of
outputs are on the DVD player? RCA connectors? And to what inputs on the mixer
are you connecting them?

And while we're at it, how about some brand names and model numbers, for the
mixer, DVD and amp?

Peace,
Paul

[P Stamler]

Questions to ask:

If you run any other source through the mixer, does it give a decent level on
the mixer's own meters? And does it then give decent level from the
amp/speakers?

If the answers to those questions are Yes and No respectively, then the problem
is the connection between the mixer and the amplifier. If so, the next question
would be, is this a balanced system (3-wire connection)? If so, it's possible
that one leg of the balanced connection is out, either shorted to ground or
open, which could give you a 6dB drop in level at the amplifier, assuming
electronically-balanced outputs on the mixer rather than transformer-balanced
and floating.

On the other hand, if you get great mixer and amplifier levels with any other
signal, but crummy levels with the DVD player, then it either is inherently too
low-level for this application, or not working properly. So...what kind of
outputs are on the DVD player? RCA connectors? And to what inputs on the mixer
are you connecting them?

And while we're at it, how about some brand names and model numbers, for the
mixer, DVD and amp?

Peace,
Paul