IEM, 3.5 and 6.35 jacks - Only get left ear when plugged fully in

Question

I am using a vocal and guitar processor in one. The headphone out is not loud enough so I am using a small amplifier (for 4 sets of headphones).

Problem is, I only get a left ear unless I remove the 3.5mm jack slightly, and then I get stereo.

This is the set-up order:

• FX............................Processor: 3.5mm stereo out
• Cable 1....................3.5mm to 3.5mm cable
• Jack.........................6.35mm to 3.5mm
• Headphone Amp......6.35mm stereo in
• Headphone Amp......6.35mm stereo out
• Jack..........................6.35mm to 3.5mm
• Cable 2.....................3.5mm extension lead (male A -> female B)
• Headphones.............3.5mm

What surprises me, is that I get stereo when I slightly remove the 3.5mm (cable 1) from the jack into the amp AND... I also get stereo when I do the same with my 3.5mm headphone jack going into the extension (cable 2).

If I plug Cable 2 directly into the FX there are no problems (but not loud enough). I also get ground buzz sometimes but I doubt this is related.

I then went and got another small amp, with a 3.5mm headphone socket, but this time with a TRS and XLR input. No problems, but sadly not loud enough. So I chained this up to the original (new one, then old one) and the same problem stands, but with distortion (which I can live with when I need volume)

My guess is I need a 6.35mm to 6.35mm stereo between the two amps because of a miss-match in the converting jacks but why does removing my headphones right at the end of the chain still give me stereo?

I need to understand the issue as the last thing I want is a dodgy monitor for performing

Answer 1

My instinct is to blames those adapters (or 'jacks' as you call them, but I've always used 'jack' to refer to the the input assembly on the device or the lead assembly on the cable). Adapters, being conceptually so simple, are easy to botch in production. It's just some bent lengths of wire that fit (or don't!) into little slots in the molded plastic. From your description, my guess is that both adapters have similar problems. If it has a screw and can be disassembled, it may be very easy to repair them; or it may be impossible if it's some kind of solid-molded construction.

If you can disassemble it, you'll see the two spring leads that connect to the tip of the cable (left channel) and that little space between the two tiny plastic rings just past the indentation (right channel). Since it's the right channel that cuts out, I recommend you examine this second lead closely; since you can connect with it by slight removing the cable, I'd suspect that this spring is too long, possibly from having slipped from its correct place in the plastic housing. It could also be corrosion at any of these contact-points (clean with alcohol if you see any corrosion).

Your proposal to use 1/4"-connecting cables and remove the need for adapters also seems like a good strategy.

Answer 2

There are already some good answers, but I just had a couple things to add. In general it's best to minimize the length of cable and number of adapters you use in your signal chain (I think you called the adapters "jacks"). This reduces the number of possible failure points. For example, do you really need the headphone extension cable? And getting the right cables as you suggested will mean you won't need adapters at all. This can potentially improve your sound quality and it will definitely remove extra sources of possible failure.

I agree with the recommendations to check your adapters and cables and make sure they are all stereo on both ends. Obviously if you've got a mono cable or adapter somewhere in your chain, you are going to lose half of your signal.

Also, when you remove the cable halfway and it still works, my guess would be that you are hearing a mono signal, but it's going to both the left and right headphones so it seems like it's working. If the jack isn't fully inserted you probably aren't getting true stereo.

The best way to fix these problems is check each cable and adapter by itself and isolate which ones might either be broken or just mono. Confirm your headphones are working in stereo with some other device, then confirm the FX is outputting stereo with the headphones, then once you know those two are working properly you can use them to test each part of the chain one cable or adapter at a time. That's usually the best way to troubleshoot anything in your signal chain by removing the variables.

Answer 3

Take a close look at both Cable 1 and the adapter (jack) connecting Cable 1 to the amp. Are you sure that these are both stereo devices?

A stereo plug will have three metal sections (tip, ring, and sleeve). A mono plug will only have two (tip and sleeve).

If you are hearing only one side, and then get both sides when you pull it part way out, that is a sign that something in your chain is mono and not stereo. The reason this can happen is that when a stereo plug is inserted into a mono jack, normally you will only hear one side, because the tip of the stereo plug is connected to the tip of the mono jack, and the ring of the stereo plug is not connected to anything. When you pull the plug part way out, the tip of the mono jack touches both the tip and ring of the stereo plug. You hear both sides, but it is actually still mono sound, because both sides are playing the one mono channel.

If you are sure that everything is a stereo device all the way through your chain, then you have a faulty device. Use the process of elimination to find it by removing the elements, one at a time, until the problem goes away.

Answer 4

A mono jack in a stereo socket or a stereo jack in a mono socket will shorten out the right channel.

Maybe your adapters are not what you think they are for.