TomHoward Posted January 8, 2013 Posted January 8, 2013 Evening all Just after a bit of advice, I've got a setup of a Sonfix S2, a pair of Tannoy Reveals (analogue), and some other stuff (CD players, PCs and the like) all switched from a socket, and I'm getting a massive power-on thump through the Reveals - I don't think it's doing them any good. The setup is all switched at the wall, through a power splitter (one of those rackmount jobs with IEC all over the back - no switching). I think the thump is the desk. At work we've got EMO switchers, but these are a bit overprices for this application. Does anyone have any advice or circuit diagrams for avoiding the power-on and off thump? Thoughts I've had are switch the desk over to hard power (never turn it off), build a unit with a relay switching the audio off before the desk thumps (but I'm not sure if it'd be fast enough), or build my own timed power on/off unit using RC networks and 240V relays or similar - but I'd need a diagram for that. Any thoughts? This is a community radio setup, so budget is low, and it needs to be idiot friendly.
dbuckley Posted January 8, 2013 Posted January 8, 2013 You need power sequencing to switch the amp on last and off first. Timer relays (from RS) are the easiest solution, but cost a bit, but not in the same bracket as an EMO switcher, I wouldn't have thought.
J Pearce Posted January 8, 2013 Posted January 8, 2013 Would a blank panel with two switches, one labelled "on first/off last" and the other vice versa, be too much for the users to understand? Obviously not foolproof, but depending on the training of the users it could catch 90% of the thumps at a fraction of the price of a true power sequencer. Failing that its a time delay relays and all the fun that brings.
TomHoward Posted January 8, 2013 Author Posted January 8, 2013 Time delay relay on the monitors could avoid the power-on thump for about £20 - but doesn't stop the power-off thump. A sequencer would be nice, if I could find one for under £300 it might be an option. I'm wondering whether there's a way just to do it with shorting the audio to earth or disconnecting the audio, using a power supply powered from the same switching as the mains power - but I don't know whether the relay would be faster than the thump from the desk - if it mutes the audio afterwards, it's a bit of a waste.
J Pearce Posted January 8, 2013 Posted January 8, 2013 How's this then?http://www.studiospares.com/mains-distribution/trojan-sps06-15a-power-sequencer/invt/348010/?VBMST=Power%20sequencer
TomHoward Posted January 8, 2013 Author Posted January 8, 2013 Christ's sake, why couldn't I find anything that cheap?I've been all over thomann and Canford - Canford's are 595 ex VAT.
J Pearce Posted January 8, 2013 Posted January 8, 2013 I didn't just stumble over it, I had a similar issue a few years ago, so had a huge dig for power sequencers. I ended up installing a rather swish remote system automation setup instead.
themadhippy Posted January 8, 2013 Posted January 8, 2013 couple of suggestions ,either a ramp generator into a lm3914,relays on the output of the lm3914,or a delay switching the speakers on,but disconnecting them instantly,something like http://sound.westhost.com/project33.htm although this needs a bit of thought if your using valve amps
TomHoward Posted January 9, 2013 Author Posted January 9, 2013 I reckon I might be able to add a timer relay within the power distro rack unit to give a delay of a few seconds on the 240V outputs for the monitors. They are active studio monitors so I can either switch the 240V to them or switch the audio. For avoiding the power-off thump I'm not sure what could be done - I don't know if a relay would be fast enough to beat the thump - the on thump is much worse though so that's a start
Nicktaylor Posted January 9, 2013 Posted January 9, 2013 I am at a loss to understand why people cant switch the kit on or off in the right sequence? I like the two switch idea for those who really need their hand holding!
Brian Posted January 9, 2013 Posted January 9, 2013 Power-on delay, origins lost in the mists of time although I think I stole it from HH amps... Have you definitely determined the cause to be the mixer? Might it not be better to get rid of the thump rather than try to mask it?
Andrew C Posted January 9, 2013 Posted January 9, 2013 I've done this with a rotary switch and some relays. Use solid state relays as big amps will fry the contacts. However, with that sequencer at <£200, I/m not sure I'd bother again!
sleah Posted January 9, 2013 Posted January 9, 2013 This little fella will do the trick for £20, so long as you don't mind either modd'ing the amp, or it could be built in to a seperate box and wired between the amp ans speakers.
jamesperrett Posted January 9, 2013 Posted January 9, 2013 I am at a loss to understand why people cant switch the kit on or off in the right sequence? I like the two switch idea for those who really need their hand holding! I'd agree. In every studio I've had for the last 20 years I've always had a set power sequence - currently it is switch on the left socket followed by the right. To switch off I switch off the right socket, wait for 5 seconds and then switch off the left. That's about as simple as you can get! The power amps are on the right socket while everything else is on the left. My mixer outputs a large thump on power on/off which has possibly destroyed a monitor amp in the past so power sequencing is important around here. James.
Andrew C Posted January 9, 2013 Posted January 9, 2013 That's OK if you, or a "competent person" are the only people using a system. Most of us however, live in "the real world" and have to deal with a mixed bunch of losers. :huh:
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