Soundcraft FX-16 -- HELP!

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David W. Richardson

Chapelgrove Films
We have a sound setup for the gym at our church, and we're having an odd problem.

First, the basic details. We have a Soundcraft FX-16 mixer. Connected to it is a CD player. The CD player is connected to channel 16 on the mixer, using a cable with the two RCA plugs on one end and a stereo 1/4" phono plug on the other. This cable plugs into the "Line" input on the back of the mixer. The mixer outputs to an amplifier, which outputs to two speakers on the stage. However, the speaker setup is such that each speaker gets both channels, rather than trying to create a stereo sound experience.

So here's the problem. When both RCA plugs (white and red) are connected to the back of the CD player, the sound is awful. I can't really explain what I mean by 'awful', but muted and just not clear. But if we disconnect ONE of the plugs, then the sound is fine. That is, it SOUNDS fine. Both speakers get BOTH channels of audio from the CD, which is a bit odd considering only one channel is being output from the CD player. If I turn the balance control all the way to one side for that fader, the sound doesn't change -- both channels come out of both speakers. But if I turn the balance all the way to the other side, nothing comes out of either speaker. Keep it in the middle and both speakers output both channels of the CD.

The thing is, we occasionally use split-track CD's, where we have to be able to use the balance control to play only one channel of the CD, but to play it over both speakers. (Does that make sense?) As things stand now, we cannot do that.

I have tried using a different CD player -- same thing happens. I'm going to try using a different cable to see if that might be the problem. And I will try plugging it into a different input on the mixer. But if those things fail, does anyone have any other ideas?

Thanks in advance!
 
This is actually a simple problem. What is happening is that you are summing the CD to mono and that means out of phase sounds are canceling out and in phase sounds are doubling in volume. Obviously the CD was not mixed with mono compatibility in mind. Way back when ;~) when AM radio was the main place music got played people paid a lot of attention to mono compatibility because MA is mono (except for a hand full of experimental stations). Now that AM radio is all sports and politic talk and almost everybody is listening in stereo nobody bothers.

So first off either just use one channel, should be OK for most things, or bring each channel separately to the mixer. If you do the later you will still probably only use one channel since they would get summed at the amp, but you would at least be able to see which one sounded best. If you plan on playing a lot of music I would recommend setting it up so you can play stereo out the speakers because there really isn't a way to "fix" it so you can reliably play both channels summed to mono.
 
David,

You are sending a stereo line level signal into a mono balanced line input, hence the problem: the appearance of the TRS 1/4 jacks is identical, the wiring not.

When you remove one RCA plug from the CD player of course it will then work: unless your CD player has a mono selection on it (I have never seen one with this, but perhaps such a thing exists) then you cannot really be getting both channels (stereo) out from the CD player. I can't quite follow why you are getting the panning issue you then describe (a photo would have helped of your mixer settings...), but, as the solution to what you need to do is straightforward this doesn't matter.

The correct solution for independent control of the L and R CD channels is to have two RCA to mono (RCA) TS jack cables: use channel 15 for L and channel 16 for R.

Hope this helps,

Roland
 
Ah yes forgot that twist. So you are also inverting one channel.

So again your channel 16 is a mono channel, the CD player is sending two channels and you need to use 15&16 on the mixer.

It also sounds like the system is wired for stereo you are just not using it that way, so going to two channels may fix everything.

As to your weird panning issues?

One thing is that you are no panning between the two inputs because you are only using one input. So again you need to bring the two channels in as two channels. I think you are wrong about some of what you describe as in If indeed you are getting both channels out of just one channel of the CD player, it's broken. I suspect though you are just getting the one side.

You have to straighten out the inputs before really anything else. Some of the weirdness may just be because you have this signal because of the channels getting put as halves of a balanced signal and at some point they will get unbalanced and you will get weird cancelations. If the CD is actually mono they should cancel out completely. Not sure how or why a pan would affect that but it may be part of the weirdness.
 
Thanks for the info guys!

I think the best idea is to try putting the two CD outputs onto separate channels on the mixer. That's the way it's setup in the sanctuary, and even though we still output to mono and send to multiple speakers, we don't have any problems like what we're seeing in the gym.

Noiz2 -- We don't want stereo out to the speakers. When we do need to use a split-track CD and play only the left channel, that channel needs to go out through BOTH the speakers, not just the left one. So we have to have mono output running to both speakers.
 
David W. Richardson said:
So we have to have mono output running to both speakers.
Click to expand...
If you bring the L and R CD outputs into the mixer as separate channels (15 & 16), then you can pan wherever you want, hard left and right for stereo or centre (which, with the fader up for one of these channels only, will give you that single channel from the CD to both speakers as you want). It's not a question of trying it: it's the norm and the only way to do it!

Cheers,

Roland
 
Throwback said:
If you bring the L and R CD outputs into the mixer as separate channels (15 & 16), then you can pan wherever you want, hard left and right for stereo or centre (which, with the fader up for one of these channels only, will give you that single channel from the CD to both speakers as you want). It's not a question of trying it: it's the norm and the only way to do it!

Cheers,

Roland
Click to expand...

Agreed.

Now I'm looking at a cabling diagram in the FX-16 manual. It shows a CD player being connected to two RCA inputs which are labeled "RETURN" -- one is "L" and the other is "R". So it looks like that's the way I need to connect this deck. I just have to find out where the controls are for that input.

The manual refers to "Stereo Returns", which appears to be a section of knobs positioned above the two "SUB" faders -- which are red and positioned immediately to the left of the two red "MIX" faders.

The manual then 'explains' the Stereo Returns thusly: "Four balanced Stereo Returns are available for the outputs of effects units or other stereo sources and are mixed directly to the AUX or MIX/SUB busses at a level set by the respective controls. The left-hand control sets the level to a choice of AUX 1 or AUX 2 (AUX 3 or LEX FX in the case of RET 4), depending on the postion of the adjacent switch. The right-hand control sets the level to MIX or SUB depending on the position of the adjacent switch (it is effectively a rotary fader). If a mono source is used, plugging into the Left jack only automatically feeds the signal to both Left and Right."

If that were written in Chinese, it wouldn't be any less meaningless to me. Can anyone translate it into Novice for me?
 
Goodness. The solution I have given you is the correct one. You won't get independent control that you want of the two channels by using these various stereo inputs, hence why not suggested. There really is nothing else to discuss! R
 
You could use the aux. returns if you wanted to, you would just need RCA> 1/4" TS adapters or a 'custom' cable. The same if you wished to use two of the main input channels (line in).
 
Rick, with the fx16 stereo returns you have no independent control of the left and right channels, which is what the op wants. Cheers, Roland
 
Well the returns section seems to have separate controls for left and right channels. And as I said, the "RETURN" on the back has separate left and right inputs, so it would stand to reason there would be left and right controls.

Here's a newbie question: If all the inputs are mono inputs, then why does each fader have a balance (L-R) control on it? What's to balance if there's no stereo input?
 
Throwback said:
Goodness. The solution I have given you is the correct one. You won't get independent control that you want of the two channels by using these various stereo inputs, hence why not suggested. There really is nothing else to discuss! R
Click to expand...

First off, I don't tend to respond well to "just do what I tell you to do" posts. I do appreciate the informed advice, though.

Now, it's no longer a question of needing two inputs if I want to control two channels. I get that and it makes perfect sense. But now it's a question of whether to go into two separate 1/4" phono inputs on the fader channels, or to do as shown in the diagram in the manual and connect the CD player through the RCA "RETURN" left and right connectors?
 
"If all the inputs are mono inputs, then why does each fader have a balance (L-R) control on it? What's to balance if there's no stereo input?"
- Probably so they can be used as mono. They are just another input (w/o the mic pre) and other niceties of the main channel strips. When I first started mixing night-club bands, (early 70's) I always used a main channels for FX returns, because they had the linear fader, more/better EQ and I could send FX to the stage monitors (pre-fader send) for insecure singers. FWIW, I had a Accutronics spring reverb and a Multivox MX-312 Multi-Echo which was similar (but more versatile with the eight selectable PB heads) than the renowned Roland Space Echo. Both used a 1/4" tape loop.
 
The RCA input/return usually don't offer any control besides volume. If you want to control the channels individually, just do as you're told ;)

Putting them on their own separate channels gives to the ability to control gain, EQ, sends, pan and volume for each of the L and R channel. It's really the only way if you want flexibility.
 
Okay, so what they're using is definitely wrong. They're plugging a 1/4" stereo phono plug into a mono jack. I can definitely see that as the problem.

So what they need is two cables, each with a single male RCA plug on one end and a single male 1/4" mono phono plug on the other. Then connect them to two separate line inputs on the mixer, and use the faders to control balance, if needed.

At this point we really don't need the ability to control EQ, sends, etc., but that could easily change in the future, so we might as well configure the system now to be able to do that.

We'll have to order the cables from Amazon, but that's no biggie. Then we should be good to go.

Thanks for the help, guys! It was ALL greatly appreciated!
 
David W. Richardson said:
Here's a newbie question: If all the inputs are mono inputs, then why does each fader have a balance (L-R) control on it? What's to balance if there's no stereo input?
Click to expand...

The balance control affects where the signal gets sent: to the left output, to the right output, or to some combination. In your situation, you could feed the left signal from the CD player to input 15, and turn the balance all the way to the left; the right CD signal could go to input 16, with the balance cranked to the right. Then you would have a stereo output. Or you could put both balance controls at center and you would have a mono mix of the stereo source.

Some mixers have phase buttons on the inputs (I haven't looked for the manual for yours, so I don't know if it does). That can be handy if, for example, the speakers are wired wrong (and you're sending a stereo signal to them): flip the phase on one of the input channels and it undoes the flipped phase on the speaker. If you're doing a mono mix, however, flipping the phase would make it sound very strange. So if you're still hearing bad sound after rearranging the wiring to the mixer board, try setting it up for stereo output and see if the phase switch improves the sound. If it does, then you should look at the speaker wiring.
 
Just use two rca to ts cables into two channels as Roland suggests. Pan the left channel hard right, and the right channel hard left, and you will get the same signal (mono) to both speakers.

Analog mixer decks allow you to do all kinds of nifty things. It really gets confusing when the manufacturer makes digital changes and does not document them, but it sound like yours are purely analog.
 
David W. Richardson said:
Noiz2 -- We don't want stereo out to the speakers. When we do need to use a split-track CD and play only the left channel, that channel needs to go out through BOTH the speakers, not just the left one. So we have to have mono output running to both speakers.
Click to expand...

It's not necessarily and either Or situation. IF your amp and speakers are set up so they can play stereo then all you have to do is pan the track you want center and it will play out of both speakers in mono. Anytime you sum stereo recordings to mono you run the risk of really weird things happening. Most of Elton John's albums (up to 80's anyway) have the main vocal out of phase and summing say Yellow Brick Road will give you a "Karaoke" version with out his voice.

You can do whatever you want but if you play commercial CD's summed to mono you will run into problems.
 
iain.bason said:
Yes, but make sure that the RCA plug is TS (tip-sleeve) rather than TRS (tip-ring-sleeve). In other words, it should be a mono plug.
Click to expand...

This is actually confusing. There is only one type of RCA plug, you are confusing an RCA plug with a phono plug.

RCA plugs are what you see on the backs of most consumer receivers and CD players,and composite video connectors on consumer gear. They are only unbalanced. Phono plugs are the ones that come with a variety of configurations in 1/8" and 1/4" diameters.
A TRS phono plug is what is typically seen for unbalanced stereo, as in headphones and most consumer 1/8" connections. Mono versions will have just a Tip and the Sleeve. Some other versions have multiple rings.
 
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