thatblokewiththelaser Posted August 16, 2006 Share Posted August 16, 2006 I was working last sat when at the end of the night my sound went down, ive not had chance to look at them till today and noticed the sound is coming out but quiet, checked leads and amp all fine, signal ok but when turned up the amp starts clipping like mad. ive taken the driver out and checked it full rnage, works fine, mid range works fine and compression driver all tested without the c ross over and work fine, now the cabs are studiospares 312b, 600watt rms cabs, usually on these I find the ceramic resistors go and once replaced work fine, but there is still noise coming from the cabs so surely it cant be that? any ideas. if I cant fix tonight its new speakers time for me tmmorow! Link to comment Share on other sites More sharing options...
Chris Hinds Posted August 16, 2006 Share Posted August 16, 2006 I have a crashed car, can anyone tell me how it crashed??? Anyone? Nope. That's because I didn't tell you anything about what the car is, what I was doing with it at the time it crashed, or the conditions in which it happened. In order to answer your question it would be necessary in much the same way to know what the speakers are, what did you notice going when they failed i.e. mids, his, lows, all and whether both were affected. Was the amp clipping at the time they failed or just after. How about the mixer? I also had to read twice to decide you are talking about a passive crossover in a cabinet rather than an active one before the amps. More information please. Buying new speakers is a poor solution because unless you understand WHY these ones failed the new ones will go the same way, maybe quicker. Regards Chris Link to comment Share on other sites More sharing options...
thatblokewiththelaser Posted August 16, 2006 Author Share Posted August 16, 2006 right sorry for the vague post. I run a behringer dx700 mixer, running main out straight into my amp (cmark mr2650) 2 x 650rms at 8ohms, speakon out to just these cabs. the cabs were answered in the post they are STUDIOSPARES 312Bs (they are sold on www.studiospares.com) it was 2.55am and I was playing one more as they ask me to and half way through the record I noticing clipping which does occur every now and then (I was playing robbie williams angels BTW so no thumping tunes) all of a sudden the red clip light lit up like a xmas tree and the cab went off, I turned the channel down and unplugged the speakon checking the cable hadnt come loose, just before the track finished he other one done the same, now the amp is 3 weeks old and I sell these to others from electrovision and never had a problem with them, I tested the amp today for an hour or so and no problems, most cables were replaced a couple of weeks ago and again checked today. now I have taken each driver and compression horn and tested it without the xover (and I mean passive I think as in the board built in, even though I do have a behringer 3 way rackmount xover which I use with my big rig.) and they all work fine. so I have arrowed it down to the xover.now in the past I have found the ceramic resistors blow and need replacing however they usually blow apart and look burtn, this however doesnt look like any damage had occured and I am getting a signal through the speakers allbeit very low and the amp clips. I have only tried this quickly when I first plugged them in, so I dont cause any more damage. if someone could tell me what compnant would let a current through (sound) but sort of withhold it (ie the clipping) and chris I think you crashed your car because you wernt looking where you were going! thanks Edit: Unnecessary quoting of previous post removed Link to comment Share on other sites More sharing options...
Simon Lewis Posted August 16, 2006 Share Posted August 16, 2006 Thermal problems with the amp? If the protection lights went on, and it shut itself down, that would explain the loss of sound.... Link to comment Share on other sites More sharing options...
thatblokewiththelaser Posted August 16, 2006 Author Share Posted August 16, 2006 but the amp is fine, I ran it today for an hour or so. the clips lights now come on like there is a short or I am putting a 50watt speaker through it. Link to comment Share on other sites More sharing options...
mal421 Posted August 16, 2006 Share Posted August 16, 2006 If as you say the amp is working fine until you turned it up . What did you turn up ?Was it the gains on the mixer , was it the gains on the amp , was in the master fader on the mixer , Or did you turn all the eq's up to 11 ? Link to comment Share on other sites More sharing options...
thatblokewiththelaser Posted August 16, 2006 Author Share Posted August 16, 2006 I was running a flat signal (cd player) straight into the unbalanced iunput of the amp. this way the source comes out at 0db if you get me, no eq or anything to mess with the sound, this was today BTW, and when I turned the amp up on the gain on the channel, the clip light would light up and even stay constant past say 2oclock on the gain dial (about 7 out of 10!) Link to comment Share on other sites More sharing options...
Simon Lewis Posted August 16, 2006 Share Posted August 16, 2006 With regards to the "thermal" comment, your amp could have been running hot when run flat out at the gig, and decided to shut itself down to protect itself. Testing it later when it had cooled off and wasn't being pushed hard would show it to be OK. With regards to the CD player direct into the amp: There is no guarantee that a) the CD outputs at "0dB" or that b) the amp has a sensitivity of "0dB". Therefore, the CD could conceivably overdrive the amp input. Furthermore, unless you give a reference value (dBu, dbV etc.) "dB" is simply 10log p1/p2, not an absolute measurement! Simon Link to comment Share on other sites More sharing options...
jayselway Posted August 17, 2006 Share Posted August 17, 2006 A few years ago, I had, what seems to be, a similar problem with a Hill amplifier. It was running well, albeit at fairly high levels (nowhere near the top though), and one output displayed error, followed by a pop, and no sound whatsoever. Shortly after, the other channel did the same, leaving me with no top end at all. I couldn't re-patch the tops to another amp, as it would appear that (and actually had) taken out both 12" mids in the tops. Not nice. On checking it over after the gig, it had blown both channel fuses, and a few components were not functional either (3 output transistors a side, and some caps + resistors). I replaced the non functional parts, and ran it into a dummy load. All was well, until 30 seconds had elapsed, when both error/clip LEDs came on (no other LEDs apart from power), and off went the amp again, taking the new components out with it. All the while the fault was present, the amp looked to be normal with the level controls at minimum, however, when they were increased, the error light would come on and stay on until the amp was switched off. It's still in the garage, and no, I haven't fixed it yet. Don't know if that's a similar problem to yours, obviously your drivers aren't going, but about the clip lights.... just a little thought that's all :unsure: £0.02 Link to comment Share on other sites More sharing options...
mal421 Posted August 17, 2006 Share Posted August 17, 2006 I don't know the Cmark amps but what I have seen on the 'www' suggests they are budget amps . Are they gain controls or are they volume controls ? I have used some budget amps in the past with volume controls , which appear to control the output rather than the input , and if you overdrive them they clip regardless of control setting . Link to comment Share on other sites More sharing options...
Simon Lewis Posted August 17, 2006 Share Posted August 17, 2006 I'd suggest that it is unusual for any power amp to have a gain control on the front panel. Most amps are fixed gain with a front panel variable attenuator placed after the input balancing circuit (if used). Link to comment Share on other sites More sharing options...
mal421 Posted August 17, 2006 Share Posted August 17, 2006 You are correct Simon . However I have yet to come across an amp with the front panel controls marked 'Input Attenuator' all the amps I have come across have said 'gain' or 'volume' . The intention was to help the OP solve his problem . I had a similar problem with a budget amp , actually a SoundLab . Nothing I did with the contols on the front of the amp would put out the clip lights out until I reduced the output from the desk . So I'm agreeing with you that it is possible a signal mismath somewhere . Link to comment Share on other sites More sharing options...
Rob_Beech Posted August 17, 2006 Share Posted August 17, 2006 I know a few amps (I say I know I've seen them but I can't remember what they were) where the clip LED's are driven by both the output and the input circuits. so light if the amplifier clips, or if the input signal is too high. Alot of mixing consoles channel peak lights work in the same fashion. they can peak at various points in the circuit (pre or post insert, eq, or just general overdriven pre.) each of which will light the peak LED, it doesn't necessarily need all the other led's on the channel meter to be lit either. Rob Link to comment Share on other sites More sharing options...
Bobbsy Posted August 17, 2006 Share Posted August 17, 2006 You are correct Simon . However I have yet to come across an amp with the front panel controls marked 'Input Attenuator' all the amps I have come across have said 'gain' or 'volume' . Beware though that, whatever the front panel control may be labelled, it's almost certainly an input attenuator just mis-named. This is probably most common at the budget end of the range where non-professional users are more comfortable with terms like "volume". Bob Link to comment Share on other sites More sharing options...
Rob_Beech Posted August 17, 2006 Share Posted August 17, 2006 I think that is what he was implying. Whilst things are labelled up with alsorts they usually refer to the same thing, in this case, input attenuator, with GAIN and VOLUME being WRONG. Bit like the active/passive vs. powered/unpowered thing.. I'm going to run and HIDE. Rob Link to comment Share on other sites More sharing options...
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