No sound > crank the gain > sound pops on and works fine. What causes this?? - diyAudio
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Old 17th May 2012, 04:34 PM   #1
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Unhappy No sound > crank the gain > sound pops on and works fine. What causes this??

I've experienced this problem with a couple different solid state devices in the last week alone. (a Mackie SRM450 powered speaker and one channel on an Allen & Heath GL2000 mixer) I'll get no, or little sound, I'll crank the gain, and then the sound will BURST through and it will work fine. What type of problem usually causes this??

I always check for cracked solder joints on the input connectors and any buttons, switches, and knobs the user might be pounding on, and also for any parts that are obviously fried. That usually gets most things fixed, but if I have to, I'll bust out the DMM and O-scope, pray that a schematic is available for whatever it is and go hunting...
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Old 17th May 2012, 06:19 PM   #2
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Is this referring to your whole audio system output or just each device, regardless of what's connected? If there are devices connected, perhaps there is a common factor like a noise gate operating in the mixer even to kill all sound when no input is detected.
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Old 17th May 2012, 07:18 PM   #3
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Everything in my test system is working perfectly.

I'm just hoping one of you guys will say something like; "Oh, yeah man, when THAT happens it's ALWAYS a capacitor problem on the input.", or something like that.

I realize that this may be an overly generic question...
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Old 17th May 2012, 08:23 PM   #4
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Happens a lot with dirty connectors, jacks, plugs, and pots. Get a caig kit.
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Old 17th May 2012, 10:19 PM   #5
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Quote:
Originally Posted by cyclecamper View Post
Happens a lot with dirty connectors, jacks, plugs, and pots. Get a caig kit.
^ I'd put my money on this.

Example: borrowed my borther's Tandbergs and they sounded great. When turning it up, the amp would go into protect. More or less the opposite of your problem. It turned out to be the temporary connectors I used for rigging the speakers up: they were too big and shorted out through the aluminum backplate surrounding the speakerconnectors. But only at higher levels when the voltage was high enough to 'jump' the oxidationlayer on the aluminum.
That is at least the explanation I gave to it... And where it shorted my amp and causes me grief, it lets your sound come through and temporarily solves your problem...
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Old 17th May 2012, 11:44 PM   #6
cihtog is offline cihtog  United States
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Quote:
Originally Posted by cyclecamper View Post
Happens a lot with dirty connectors, jacks, plugs, and pots. Get a caig kit.
I third this motion - "when I turn it up, it goes away" is right up there with, "when I smack the side it works".

On the mixer, I would look at seldom used effects/insert jacks (anything that breaks the normal connections if you plug something into it). And on the powered speaker, I would give the solder joints another once over, maybe even a cracked leg on a passive (Large cement resistor are famous for this).

When reflowing known cold solder joints, it's always best to use some fresh flux, and remove all of the old solder first (If it's dirty underneath, adding fresh solder/flux to the top does little to correct this).

Try the wiggle and poke test with some chop sticks or a wood skewer - clean all connectors, and pots (powered down) with deoxid or deoxit contact cleaner.

Tracing the signal flow while it is NOT working correctly is also something that should not be overlooked. If you can narrow down the locality of the actual "point", that the signal is lost, you can start testing from that point outward, and in most cases, find the culprit rather quickly.

With the mixer you have the advantage of "working" channels, with in which to compare as well.
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Old 18th May 2012, 07:18 PM   #7
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Don't forget relay contacts. Protection relays at the output are a common trouble spot in amplifiers.
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Old 25th May 2012, 05:18 PM   #8
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I have a similar issue with an Allen and Heath GS3. I have not used it in a couple of years and there are a few issues with it now.

1. I have the same issue in that I need to turn the input gain up full on some channels to start getting sound from it. What should I be looking to clean here? The jack input? (incidentally, if I insert a compressor or something, there is no issue at all).

2. The master output is pretty dodgy - there's a fluttering noisy sound coming out one side. Almost like wind blowing into a mic. Is this the reverse of the first issue? I.e. will cleaning the output jack fix this?

3. Some EQ pots are quite crackly. How do I go about cleaning these?

4. For the above three issues, which would I need to open the desk to fix? I am thinking all, but would be good to know if I could fix some of the issues quickly. Also, any tips on how to properly clean the parts would be great.

5. In general, would generic alcohol based electronic cleaner and/or lubricant work (which I have) or do I need deoxit?

Sorry for all the questions, but this is the only thread I have found which talks about the gain issue and some of the answers so far make a lot of sense to me. I really appreciate any feedback you may have. Even if that is to say "bring it to professional"!
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Old 25th May 2012, 06:52 PM   #9
cihtog is offline cihtog  United States
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@trevox,

You would get quicker and better results if you start you're own thread (titled accordingly) - most replies here, will be from the OP and those that have replied since.

1. The insert jack is most likely corroded - happens a lot.

2. Probably not, this can be caused by many things, but most likely a dried out cap.

3. Either spray cleaner where the wafer meets the case, or put a snug straw over the shaft and spray into the straw. Scratchy pots can also be caused by bad coupling caps.

4. More than likely.

5. DeOxit is over priced - I use DeOxid, others will recommend WD-40, CRC 2-26, etc... as long as it does what you want, and does not cause problems - do what works for you.

I have never seen anyone on this forum, harp on anyone, for starting new threads and/or not searching well enough before posting - if we can help, we'll reply, if we can't or don't want to, your thread will fall off the front page into obscurity - simple as that. The only thing really required, is as much information as possible - we aren't sitting in front of your bench, you are - share gratuitously ;-)

This is a community that likes talking about all things audio, and even some things not audio - not whether or not you posted correctly.

(As a matter of personal opinion, especially where hazardous electrical troubleshooting is concerned - even if the brand and model are the same - all issues of analysis must be kept as separate and distinct as possible. Two identical devices may have exactly the same symptoms, but entirely different causes, and any assumption of continuity over ambiguity, is in err of he who shall be corrected.)

Last edited by cihtog; 25th May 2012 at 07:08 PM.
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Old 25th May 2012, 07:07 PM   #10
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Quote:
Originally Posted by cihtog View Post
You would get quicker and better results if you start you're own thread (titled accordingly) - most replies here, will be from the OP and those that have replied since.

1. The insert jack is most likely corroded - happens a lot.

2. Probably not, this can be caused by many things, but most likely a dried out cap.

3. Either spray cleaner where the wafer meets the case, or put a snug straw over the shaft and spray into the straw. Scratchy pots can also be bad coupling caps as well.

4. More than likely.

5. DeOxit is over priced - I use DeOxid, others will recommend WD-40, CRC 2-26, etc... as long as it does what you want, and does not cause problems - do what works for you.

I have never seen anyone on this forum, harp on anyone, for starting new threads and/or not searching well enough before posting - if we can help, we'll reply, if we can't or don't want to, your thread will fall off the front page into obscurity - simple as that.

This is a community that likes talking about all things audio, and even some things not audio - not whether or not you posted correctly.
Thanks for the reply! I will start a new thread with the issues. And in regards to apologizing in advance for my questions, it was more down to expecting abuse as happens most places on the web and put simply, my nature. I'm happy to hear there are some places on the web where valid questions get valid answers rather than a torrent of abuse!
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