tm486 Posted January 5, 2013 Share Posted January 5, 2013 Hi, My Ashdown Mag 300 C115 makes a fairly loud thud when I turn it on. When I turn it off, there is another, louder thud followed after about half a second, by another quieter thud. These are both affected by the volume dial, louder when it's up high and fairly quiet (but still obvious) when it's off completely. I think the thud when I turn it on has always been there, but the thuds when I turn it off are new. They sound a bit like unplugging the bass whilst the amp is still on. The sound comes through both the speaker in the combo and the speaker in the extension cab. Looking at them the speaker cone moves quite a lot. When I'm playing through it, even when very loud, the speaker cone hardly moves visually, but when switching the amp off you can see the speaker cone move a considerable amount. Is this a sign of any damage in the amp and if so does anyone know how to fix it? Is this likely to damage the speakers? Thanks, Tom Quote Link to comment Share on other sites More sharing options...
mart Posted January 5, 2013 Share Posted January 5, 2013 I've got a Hartke combo that also makes a loud thud when turned on or off. It's always done it, and worked perfectly reliably for about 5 years now, so it's not something I worry about. But it's definitely a bassy thud, nothing like the sort of crackly sound you get when unplugging a bass with the amp on. Quote Link to comment Share on other sites More sharing options...
thinman Posted January 5, 2013 Share Posted January 5, 2013 I've got a MAG300 head as a spare. It goes pop/thump a second or two after being switched off. Seems to be normal behaviour in these? Quote Link to comment Share on other sites More sharing options...
tm486 Posted January 6, 2013 Author Share Posted January 6, 2013 Cheers guys, as I say, I've never really noticed it before, but I think I may have found the reason for that. The volume of it is affected by the volume on the amp. I've been using an external preamp recently and for ease of use I control the volume on that so I leave the volume on the amp higher than I normally would, so it must just be this that is making me notice it more than I used to. I was just worrying at how much the speaker moved I guess. I didn't think it would be serious, but thanks for the reassurance. Tom Quote Link to comment Share on other sites More sharing options...
jaydentaku Posted January 6, 2013 Share Posted January 6, 2013 I have noticed this on various hardware over the years. Took it for granted Quote Link to comment Share on other sites More sharing options...
buckers Posted January 22, 2013 Share Posted January 22, 2013 This also happens on mine and I presume its capacitors discharging. I simply turn down the volume control prior to switch off - switch off with no thump - then put the volume control back up to its original position again a few seconds later. Quote Link to comment Share on other sites More sharing options...
uncle psychosis Posted January 22, 2013 Share Posted January 22, 2013 [quote name='buckers' timestamp='1358849391' post='1945866'] This also happens on mine and I presume its capacitors discharging. I simply turn down the volume control prior to switch off - switch off with no thump - then put the volume control back up to its original position again a few seconds later. [/quote] I always make sure the volume on any amp is turned down before I turn it on or off. Its maybe a bit paranoid, but it saves you from nasty surprises if things aren't set where they're supposed to be. Quote Link to comment Share on other sites More sharing options...
BOD2 Posted January 22, 2013 Share Posted January 22, 2013 Yes, standard "recommended" amp switch on/off sequence to protect speakers is as follows - Turn ON 1. Turn master or main volume down to zero 2. Switch on power 3. Turn master or main volume up to normal operating level Turn OFF 1. Turn master or main volume down to zero 2, Switch off power It's what sound engineers do all of the time. And don't always assume that the volume will be at zero because that's where you left it last time you switched off. The "sound fairies" often move the volume control when you're not looking.... Quote Link to comment Share on other sites More sharing options...
Subthumper Posted January 24, 2013 Share Posted January 24, 2013 (edited) I think these amps should be fitted with an anti thump relay. Basically there's a relay that connects and disconnects the speaker outputs during switch on/ off that is powered by a time delay circuit so that the power supply and amp powering up/down doesent make the speaker thump with the switch on transient. Its usually a delay of about 3-5 seconds. It sounds like the relay in your amp has fused shut or the circuit that operates it is faulty and allowing the speaker to thump when you switch on or off. I'll have a look at the schematic to see if it should have one. If this is the case you need to get it to a tech. Cheers Justin Just looked, I've only got diagrams for the ABM but I think its probably very similar or maybe the same power amp and psu for both amp and it should have a delay circuit....sounds like yours is faulty. FWIW some amps dont have this feature...usually smaller ones, but the thump can become more exagerated as the amp gets older and the components especially the smoothing caps age with use and time. Hope this is usefull. Edited January 24, 2013 by Subthumper Quote Link to comment Share on other sites More sharing options...
Subthumper Posted January 27, 2013 Share Posted January 27, 2013 Was that too technical an answer? Quote Link to comment Share on other sites More sharing options...
tm486 Posted January 29, 2013 Author Share Posted January 29, 2013 [quote name='Subthumper' timestamp='1359329847' post='1953262'] Was that too technical an answer? [/quote] Sorry I only just noticed that this had been replied to. No that answer is great, I'd not noticed it before so this would help explain why I might have just started noticing it. Thanks, Tom Quote Link to comment Share on other sites More sharing options...
tm486 Posted January 29, 2013 Author Share Posted January 29, 2013 [quote name='BOD2' timestamp='1358862720' post='1946164'] Yes, standard "recommended" amp switch on/off sequence to protect speakers is as follows - Turn ON 1. Turn master or main volume down to zero 2. Switch on power 3. Turn master or main volume up to normal operating level Turn OFF 1. Turn master or main volume down to zero 2, Switch off power It's what sound engineers do all of the time. And don't always assume that the volume will be at zero because that's where you left it last time you switched off. The "sound fairies" often move the volume control when you're not looking.... [/quote] Cheers for the reply, I've gotten into the habit of doing this since hearing the loud thumps so it's good to know that it is the right thing to do. Tom Quote Link to comment Share on other sites More sharing options...
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