• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Possible [Power?] Amp Malfunction

amos

amos

Oct 23, 2003
1,692
8
40
SE Portland Oregon
#1
Forward: QSC PLX 1602; bridged. Speakon from QSC to Aguilar GS112. 1/4" TRS from first GS112 to second GS112.

So here's what happened tonight: Towards the end of rehearsal we are playing a song and all of a sudden I hear a loud *POP* I stop playing and there's a signal spike without me even touching my bass. There's massive hissing/static coming out of my tweeters. The hissing was the first thing I noticed so I turn off my tweeters, the static goes away, I'm starting to think I somehow blew tweeters on BOTH cabinets. I was quickly proven wrong as we continued playing (guitarist: you sure, dude?) I hear another pop. Turn off amp completely. About 10 minutes later turn amp back on. Turn tweeters back on, and no hissing everything fine. We messed with the PA for a while setting it up for vocals and I goto play again and again a noise but this time I realize the once it pops/signal spikes and starts hissing the volume drops hard. I'm assuming this is a problem with my poweramp. Calling Bob Lee: How do I get this fixed ASAP? We have our first big show coming up, I do not have a backup amp (other than an Ampeg BA115:rollno:). Help.:help:

Footnote: You fix one problem and another one arises. For anyone who read my previous post about having problems attaining a normal tone/volume, it was indeed caused from elevating both my 1x12s well over a foot as well as tilting them back.

Edit: I also tested my speakers through another [guitar] head, the speakers are fine.
 
#3
Why are you using a TRS cable between the cabs? Is it just a standard shielded TRS cable (which you shouldn't be using for speakers), or does it have thick conductors suitable for speaker connections? I don't know what your problem is, but you should be using a proper 'speaker cable' between your cabs.
 
#4
I had something similar happening to me. Turned out to be the spring clips on one of my battery boxes needed tightening up to make a better contact. No more problems so +1 on checking your battery.

BTW just because your battery IS new doesn't mean it is not causing problems. I replaced one once and the bass sounded really strange. Nothing I could put my finger on but definitely not right. Changed the battery several times still the same. I was beginning to doubt my sanity (that's always in question anyway :) ) until I opened a new box of batteries and put one of those in. Problem solved!!! The entire original box had some sort of a problem that my electronics didn't like. I've never encountered the problem again but it was weird!!

Paul
 
#5
zombywoof5050 said:
Why are you using a TRS cable between the cabs? Is it just a standard shielded TRS cable (which you shouldn't be using for speakers), or does it have thick conductors suitable for speaker connections? I don't know what your problem is, but you should be using a proper 'speaker cable' between your cabs.
Click to expand...

I am using a 1/4" speaker cable between cabinets. I thought TRS stood for tip-ring sleeve, meaning the three contact plug that the cable is terminated with. a 1/4" TRS speaker cable?

This certainly isn't a problem from low-battery juice, the battery is only probably 50 hours old, though the weak contacts could be responsible for intermittent volume drop/transient noise/hissing
 
#6
No such thing as as a tip-ring-sleeve (TRS) speaker cable. I think you are misunderstanding the term. A standard 1/4" speaker cable end is a "tip-sleeve" plug. TRS is when there are THREE sections on the plug (as with stereo headphones) instead of two as on a 1/4" speaker cable jack.

If indeed you ARE using a TRS cable for speaker, stop using it and get a proper speaker cable to avoid potential damage to your amp.
 
#7
Eric Moesle said:
No such thing as as a tip-ring-sleeve (TRS) speaker cable. I think you are misunderstanding the term. A standard 1/4" speaker cable end is a "tip-sleeve" plug. TRS is when there are THREE sections on the plug (as with stereo headphones) instead of two as on a 1/4" speaker cable jack.

If indeed you ARE using a TRS cable for speaker, stop using it and get a proper speaker cable to avoid potential damage to your amp.
Click to expand...

Thank you for clearing this up. I am using a Monster Speaker Cable.
 
#9
BassmanPaul said:
I'm glad you got that sorted out! ;) If you have the choice replace the 1/4" cable with a speakon. Unplugging the 1/4" shorts the tip and sleeve momentarily and can cause damage to your amp. Wired +1 and -1 at each end.

Paul
Click to expand...

BassmanPaul: I have always used a 1/4" speak cable. I haven't yet had a chance to get this all sorted out. Here's the deal though, the only thing I found wrong when this all started was the 1/4" cable had popped out of the speaker(I think). Is my Amplifier damaged? why did this happen with heavy duty speaker cable? At only rehearsal-level SPL?
 
#11
It's definitely not a problem with my bass. I played through two different combos, and the input jack; battery are all fine. It's an issue with the amp or speaker cable (bad ground? it's a Monster brand speak)...tomorrow when the music shops reopen I'll take my rack down and plug it into a cab see whats up...if I can't reproduce the problem I try a new speaker cable when I go up to rehearsal.
 
#13
Try this: Unplug your pre from the power amp. Turn the power amp on and let it warm up real good and listen for tweeter problems. If none, try running your home stereo pre amp out into it. Crank it real loud preferably with some bass heavy music. If you still get no problems with it try your preamp running into your home stereo (watch the volume).

when you get problems during practice:

Try a guitar in it

Unplug the pre - the amp should be dead silent.

If you hear noises with no pre connected to it then it is the power amp.

Hope that helps you!
 
#15
I was referring to the power amp side of the 1/4" cable. Shorting the preamp mutes the signal. In fact when you take your guitar cord out of the input jack, the jack self shorts the input to ground. Giving you pleasant silence instead of hum.

The power amp jacks do not short unless your cord is partly plugged in. Hence another benefit of speakon cords.
 
#16
bassmodder said:
I was referring to the power amp side of the 1/4" cable. Shorting the preamp mutes the signal. In fact when you take your guitar cord out of the input jack, the jack self shorts the input to ground. Giving you pleasant silence instead of hum.

The power amp jacks do not short unless your cord is partly plugged in. Hence another benefit of speakon cords.
Click to expand...

bassmodder: It's a QSC power amp. I use a speakon cable at the power amp side and the first speaker side. my two cabs only have one speakon connector each, so with daisy chaining them I have to run one connection (one speaker to to the other speaker) with a 1/4".
 
#17
Shorting a 1/4" jack in a speaker cable shouldn't be an issue if you only plug in and unplug speakers with the power turned off, which is how you should do it. I think there's an amp issue going on with something shorting out momentarily.
 
#19
amos said:
I'm really worried about this. Can some one please tell me what happens when a 1/4" speaker cable momentarily comes half-way out while playing?
Click to expand...

Invariably the tip will be shorted to the sleeve by the barrel of the jack socket. If this happens on the supply end you'll short your speakers momentarily - no biggie. If it is the speaker end you will short circuit your amp possibly leading to damage. If you can stop using 1/4' cables and go speakon.

Paul
 
#20
amos said:
Forward: QSC PLX 1602; bridged. Speakon from QSC to Aguilar GS112. 1/4" TRS from first GS112 to second GS112.

So here's what happened tonight: Towards the end of rehearsal we are playing a song and all of a sudden I hear a loud *POP* I stop playing and there's a signal spike without me even touching my bass. There's massive hissing/static coming out of my tweeters. The hissing was the first thing I noticed so I turn off my tweeters, the static goes away, I'm starting to think I somehow blew tweeters on BOTH cabinets. I was quickly proven wrong as we continued playing (guitarist: you sure, dude?) I hear another pop. Turn off amp completely. About 10 minutes later turn amp back on. Turn tweeters back on, and no hissing everything fine. We messed with the PA for a while setting it up for vocals and I goto play again and again a noise but this time I realize the once it pops/signal spikes and starts hissing the volume drops hard. I'm assuming this is a problem with my poweramp. Calling Bob Lee: How do I get this fixed ASAP? We have our first big show coming up, I do not have a backup amp (other than an Ampeg BA115:rollno:). Help.:help:

Footnote: You fix one problem and another one arises. For anyone who read my previous post about having problems attaining a normal tone/volume, it was indeed caused from elevating both my 1x12s well over a foot as well as tilting them back.

Edit: I also tested my speakers through another [guitar] head, the speakers are fine.
Click to expand...

Do you plug your bass directly into the PLX amp?
 

Latest posts

Top Bottom
Back