Why am I getting only half the mix?

[daveperryaudio.com]

Hi

 

This is my first post.

 

When playing audio from CD or ipod through our theatres PA I sometimes only get half of the mix. Most of the time I get the full mix fine but on occasion a company will bring in a CD and a track on it wont sound right. I don't know what the variable is.

 

We have a mono system in house, I can hear you screaming "WHY?!" already. Not my choice.

 

The CD player outputs as stereo RCA's to a mono Jack inserted into a L/Mono channel on our desk.

 

Should the mono jack sum the stereo signal before it gets to the console or is the summing done inside the console itself.

 

Hope I can get some answers.

 

Thank You

[MarkPAman]

Have a look at this thread from earlier this week. I think your problem is caused by the same thing.

 

e2a Actually, on re reading your post it's not quite the same thing causing it.

[Bobbsy]

If a mix hasn't be checked for mono compatibility, simply summing the signal can result in some cancellation.

 

Or, if one of your two leads is wired backwards, this could cause cancellation of anything panned centrally.

 

Bob

[pete10uk]

Hi there and welcome.

 

The CD needs both parts of the Stereo signal putting in to the desk. I presume that someone has made a mono lead because you are short of inputs on the mixer. Some sources will sound worse than others but it isnt the correct way of doing things. Someone with more knowledge than me will tell you the technical stuff but I would use one of these TX-J2 Unbalanced Input Transformer - Unbalanced stereo inputs to summed balanced mono output Available form CANFORD AUDIO, 0191-4150044, http://www.canford.co.uk or something similar.

 

 

 

Hope this helps

[p.k.roberts]

Just to be clear, when you say you are only getting half of the mix, do you mean that you are only hearing either the left or right output of the source, or that you are losing certain elements of the mix (particularly perhaps those panned separately and quite a bit of the bass)?

[jameskerr87]

The problem is most likely the cable.

Could be wired out of phase in the Jack plug?

Are you sure it is a MONO Jack?

 

Have you got a balance knob on the CD player? with the CD player balance all the way left you could just use 1 RCA to Jack cable from the left output.

Have you any spare channels on the desk? Get 2 RCA to Jacks made up, this will give you a bit more flexibility for when you get a click track through one day.

 

 

You are using a Lmono input, is there a Rmono input on the same channel, if so just get 2 RCA to Jacks and let the mixer sum the signals, this is what your mixer is for you know like mixing stuff..

[daveperryaudio.com]

Thank you for the replies. To clarify there is a stereo channel on the desk however the 2 RCA outs of the CD player are wired to a mono jack. I believe that it is likely to be the wiring of the jack which is causing the problem. However I have no idea why they don't use two individual cables and let the mixer sum it.

 

Playing some tracks through the CD player maybe missing one side of the mix I.e the left side. However playing the same track from an ipod going to a mono input sounds fine.

 

Should a left and right RCA wired to a single mono jack going into a mono input produce the same result as two single RCA to mono jack leads going into a L & R stereo input and letting the mixer sum the signal?

 

If so then maybe I need to rewire the jack.

[jameskerr87]

That would be a better option, it with provide you with a bit more flexibility and it should work just fine unless the reason the mono jack was made is because the right input channel on the desk is faulty, but its well worth giving it a go.

 

CD OUT L -> RCA --------->Jack-> Stereo L input

CD OUT R-> RCA ---------->Jack-> Stereo R Input

[paulears]

People are trying to get you to give a few clues, but you've not quite described the important bit. We're also not quite sure your current level of understanding - so we're having difficulty pitching the answer. I'll assume you don't know what I'm about to say - so if you do, please don't be offended.

 

There are things that make sorting this one difficult because you've decided something is missing - the most likely fault condition that we're all hinting at is that the cable you have is miss wired. A test meter will sort this one. If the centre of the two phonos are electrically linked together AND connected to the tip of the two circuit jack, and the shield of the phonos is connected to the sleeve of the jack, then this is a properly wired 'mono' lead. Your description of something 'missing' could be the left or the right not being there. Depending on how the tracks are mixed, this can be very obvious, or almost unnoticeable. For instance, early Beatles recordings when stereo was still a novelty often would have the lead vocal centre - but bass would be totally from one side, and the guitar the other - so losing one removes something critical from the music. Big Band stuff recorded in the seventies had saxes one side and the trumpets the other - so when they went 'doo wop, wop' - it kind of ping-ponged from speaker to speaker. Even weirder if your dad took his new stereo with two speakers as meaning one speaker went into the front room, and the other into the back! Very odd.

 

Losing a channel like this is quite rare. Sometimes, a lead could be laying around that has the two phonos one end wired to a 3 circuit jack - often wrongly described as a 'stereo' cable. Some mixers with unbalanced inputs use 3 circuit jack sockets for their line inputs, and as the guitar type 2 circuit jack might be replaced by a 3 circuit one, wired to a single source - using the tip and the ring connection works fine. However if the lead you have has a 3 circuit jack wired to the phonos, in the same way we wire headphones - one channel to tip, one channel to ring and the shields all wired to the sleeve - this one causes a very, very common problem. The mixer ignores the sleeve connection and what you will hear are the parts of the recording that are left or right ONLY. Anything recorded exactly the same in the left and right channel cancels out and the recording sounds very odd. Vocals, which are usually panned dead centre vanish, but the backing vocals that are panned left and right are still there. Sometimes the vocal gets cancelled but leaves behind a phantom echo of itself - because the mono send on the recording mixer was sent to a stereo processor - so there are differences in the reverb, and we hear them. This is also the reason why those karaoke cheap vocal removers often don't work too well. It's easy to remove the central image, but no every track has a dead central vocal and no reverb - which is what perfect cancellation requires.

 

So describing how something sounds 'wierd' is tricky. You could have a poorly wired cable and you really are missing the left or the right - or you could be getting the centre image removed - this cable would pass a test, because it's not faulty - but when plugged into some mixers the screen connection on the sleeve of the plug is not connected.

 

You have one of these combinations - but which one, we don't know.

 

If you knew all that - sorry, but I wasn't sure.

Paul