I think I broke my mixer

[gy]

I've had my Soundcraft Spirit E6 for a couple of years now. Recently the headphone socket stopped working correctly.

Symptoms:
Sound only comes through the right channel. I tried plugging some cheap earphones in, to rule out faulty headphones - the left earphone (and consequently my left ear) got very hot quite quickly.

Possible cause:
In all that time I never read the section of the manual which clearly states that I should use headphones rated at 200 ohms or greater. My Audio Technica ATH-910 Pro headphones are rated at 40 ohms .

Diagnosis:
This is where I was hoping for some help. I guess my headphones drew too much current and eventually broke something. Is that possible/likely?

Solutions:
1) I spoke to a helpful man at Soundcraft, who said it would probably be about £60 labour. Then there's postage, and it's not light.

2) ...?

Any advice appreciated, especially advice including a cheaper solution.

Thanks.

[BertKoor]

Plausible... Especially if you tend to drive the phones quite hard.

Either you get it serviced (worth it!) Maybe you can cut some costs by dropping it off in person at Potters Bar, North London. Tech support teams I've dealt with so far are very willing to try to fix it within an hour (during office hours ofcourse)

Or you write off the headphone socket, and buy a seperate headphone amp to be plugged in to a set of outputs. Not cheap either if you wanna do it right...

[gy]

Thanks BertKoor.

I haven't driven the headphones hard at all - perhaps that wasn't the problem? Having had a quick look around, it seems that very few headphones fall into the 'greater than 200 ohms' category. Am I missing something?

[rp314]

it seems that very few headphones fall into the 'greater than 200 ohms' category. Am I missing something?

I have always been a Mackie user just out of laziness and not having a good reason to switch but have trouble believing that Soundcraft mixers are this restricted when it comes to headphones.

I'm not questioning your claim but surely there must be other Soundcraft users here who can either confirm this or give testimony to having used such cans without incident.

Mixers can be troublesome regardless of brand (which is why I recommend people avoid buying used ones on eBay)and IMHO it may just be that yours needs to be serviced without you having done that much to cause the malfunction.

[gy]

Thanks. I think you're probably right. I've been trying to find fault in my set-up, when it could just as well be a weak component in the mixer.

[deaf dunderkwac]

hmmm we have a spirit mixer... been using 32 ohm headsets for at least 7 years without problems.
The clue is the left headset getting warm. Probably the driver has failed (it happens) and is putting out either DC or a full rail-to-rail oscillation above your hearing.
Either way, get it repaired, if the rest of the mixer does for you what you need.

[Lagrange]

I've had huge problems with the spirit line..
- Powersource overheated and I got this deadly wWWWWAAAAAAHHHHH sound..
- The Phantom power button basically would kill the sound on the master bus (weird one)

The funny thing is that these were 2 different mixers!?

Yea I came to find out the they use some pretty crappy parts (internally).. I'm no expert but I do know I will never f**k with that company again!!

L

[kenn]

try to find a local service depot (eg music store), or a clever friend to have an initial look.

You said the left side got hot AND it didn't have any output. If that's the case, I would say that either the left output cap has shorted (if it has one) or, if there's no output cap, the left output device has fried and is shorted to a voltage rail. To check this, get a new stereo plug (with nothing connected), stick it in the headphone socket, and measure left to ground and right to ground on the jack with a DC voltmeter. Any non-zero DC voltage reading means there's a problem.

The biggest pain about small mizers is taking off 87 knobs, and removing 87 control nuts and 14 screws to get the bloody thing open. Once in, the circuits are usually simple to service and the parts aren't usually exotic.

[gy]

Thanks to everyone for the help.

I plugged in a stereo jack cable, as kenn suggested, and measured the DC voltage from earth to left. I found nothing. Nothing from earth to right either. That was with the mixer turned on and all faders open, but no actual input.

Does that help with the diagnosis? Does it suggest a dead capacitor is the cause?

[deaf dunderkwac]

Thanks to everyone for the help.

I plugged in a stereo jack cable, as kenn suggested, and measured the DC voltage from earth to left. I found nothing. Nothing from earth to right either. That was with the mixer turned on and all faders open, but no actual input.

Does that help with the diagnosis? Does it suggest a dead capacitor is the cause?

At this time you have to tear down the mixer to see where the signal is failing to pass through.
If you don't feel comfortable doing this, take it to a repair center.

[kenn]

I plugged in a stereo jack cable, as kenn suggested, and measured the DC voltage from earth to left. I found nothing. Nothing from earth to right either. That was with the mixer turned on and all faders open, but no actual input.

Hmmmm.

First, can you absitively, posolutely confirm that your left earphone got really hot, that first test? That's what made me think about a DC problem, but if you didn't measure any DC voltage hanging around the headphone out, that seems to rule that out.

So, could you set up to repeat a bunch of tests?
- get a known OK set of headphones
- start with the mixer off (not warmed up)
- turn on, set up the mixer and route a stereo signal to the headphones out, but not set too loud. Plug the headphones in... hearing the signal in both left and right?

if not:
- any chance that you don't have signal to one side? eg twiddle pan pots, confirm that both console L and R meters are bouncing, twiddle the headphone volume control a bit, etc
- try the DC voltage measurement again, once with an empty jack, and again with the headphones connected, if possible.
- wiggle the headphone jack - maybe it's a loose or broken connection in the mixer

If you have sound in both sides, but one side quits after seconds or minutes, there's possibly a heat-related problem with the headphone output circuit.

Anyways I hope these help a bit. We're running out of the easy tests... the next stop may very well be a repair shop

Good luck...

[gy]

Right, I have just measured again and there's 20V across the left headphone output. I must have done something stupid the first time .

I'm going to try and fix it myself and I'd be grateful for any advice on disassembly, diagnosing the exact problem, and fixing it. Thanks to everyone for helping me, it's much appreciated.

[kenn]

Ah.

Depending on the exact output configuration, I expect that you'll find one or more of the following:

- if the output is direct (no capacitor), and the output device is an IC... it's fried and will have to be replaced

- if the output is direct (no capacitor), and the output consists of an IC opamp and 2 or 4 transistors, start checking the transistors, then the opamp.

- if there's an output capacitor (it will be large-ish, like 100 to 470 uF or so) it's likely gone short. This doesn't happen too often, but it's not impossible either. And the shorted cap may have caused the output curcuit to blow as well.

Anyways, it seems like it's not a simple problem. Your best bet is to get help, or to take it to a shop.

Do you have any friends taking electronics at school? They may be able to help, or be able to get an instructor to help.

[gy]

Thanks kenn,

Well, I've found a local man who is fixing it for me, which at least saves on postage. He tells me that the opamp is fried, like you suggested.

I'd quite like to know how it happened, so that I can avoid doing it again.

Is it possible that my headphones broke first and that the faulty headphones then broke the mixer? The left headphone was a bit dodgy before the mixer broke. (I should point out that I managed to step on the cable of my headphones surprisingly often on the short walk from microphone to desk).

[BertKoor]

Hmmm.. The cirquit is designed for a high impedance. If you've managed to short-cirquit it for a longer period (meaning zero resistance instead of the 40 Ohm it would be otherwise, let alone the 200+ Ohm it was designed for) then indeed that increases the risk of frying it.

I'd advice to consider replacement of the cable of the headphone. Shouldn't be that expensive. And you say it's dodgy anyway, which for me definitely would be trigger to fix it.