Kevin Ross Posted December 1, 2008 Share Posted December 1, 2008 Morning blueroom, I was having a read through another site I go on and I stumbled across this article from Dave Rat about running amps more efficiently http://www.prosoundweb.com/live/articles/d...amptricks.shtml To save you reading the full article the basic idea is that you flip the polarity of one of the inputs then flip the polarity of that channels output so if you are driving two speakers that are playing mostly the same thing both channels are not fighting over the power from the same rail at the same time I had a spare few hours the other day so decided to try this out on one of our amp racks but instead of running the amp in bridged mode as per the article I just rewired the cable that goes from the amps output to the patch panel as well as flipping the polarity on the LMS. I fired it up in the lockup and all sounded good so I decided to take it out on a job like this. The job was a dub/DJ/MC battle thingy at a night club, in others words a good test of sub power! We set the system up and were happy with the results, now I’m not sure if I could hear any extra power and TBH we had brought a system with enough headroom anyway. I was wondering if anyone else has tried this trick and how they got on. It does seem like a good idea in theory for when you have to run things a little hotter than normal and need every last ounce (watt) of power. Link to comment Share on other sites More sharing options...
Rob_Beech Posted December 1, 2008 Share Posted December 1, 2008 All the amps powering the subs in the aspect systems I use are wired this way, I haven't noticed a massive difference in normal conditions but I tend to notice a significant improvement if I'm limited on mains power, ie a rack from 16A or even 13A. Link to comment Share on other sites More sharing options...
Kevin Ross Posted December 1, 2008 Author Share Posted December 1, 2008 That’s a good point, this particular amp rack has one 3000w amp and one 2000w amp soon to be changed to another 3kw amp that is switch mode and weights about 7kg. We have been testing the prototypes and are just waiting for the final version to come out. Anyway back on topic, this amp rack has 2x16a inlets as most of the venues this rack goes to only has normal mains power. I that case we would use 13a to 16a extension, if we were outdoors and had 16a power available then we just use 16a to 16a cables and if for some reason the gods are smiling on us and we get a 32a drop then we have a small distro of 32a to 2x16a and so on. I’m glad I went through with this modification as most of the time we are running off 13a so sometimes power can be a bit tight. Have any other members got any experience of this setup? I’m glad I’m not the only one that runs things like this Link to comment Share on other sites More sharing options...
Chappie Posted December 1, 2008 Share Posted December 1, 2008 Whether this trick works or not is based on an understanding of the design of the power supply within each amp you want to try it with. Some designs it works with, some is doesn't. It depends on many factors including type of PSU (toroidal/ switch-mode etc), number and location of reservoirs (primary/ secondary, pre/ post transformer etc), number and type of power rails (single/ dual/ quad, single/ dual polarity etc) and what each of these sections or components are actually doing at any one time. Lab Gruppen actually build this into the design of some of their amp ranges to balance the load on their PSUs, so trying this trick on these models will actually have the reverse effect and loose you headroom, so it pays to know what is going on inside your amps. Link to comment Share on other sites More sharing options...
Stuart91 Posted December 1, 2008 Share Posted December 1, 2008 My hunch is that this technique will give greater dividends on larger shows. If you look at Rat Sound's portfolio, they are deploying large quantities of amps, and a 5-10% reduction in consumption is a significant difference. This isn't necessarily the case for two amps running from a 13amp supply. Link to comment Share on other sites More sharing options...
foh_al Posted December 1, 2008 Share Posted December 1, 2008 Our QSC amp racks are wired that way. It definitely helps on the smallest of shows where the power available is very limited and/or suffers from voltage drop. Link to comment Share on other sites More sharing options...
Killyp Posted December 1, 2008 Share Posted December 1, 2008 B&O has done this on consumer-grade amps since the 60s. It helps to improve the sound too by stabalising the power supply at higher volumes.... Link to comment Share on other sites More sharing options...
Kevin Ross Posted December 2, 2008 Author Share Posted December 2, 2008 Just out of interest are people using this trick on all their amps or just the ones on sub duty? Personally I am using it on all of them at the moment and at some point I will get round to wiring the larger amp racks this way. Link to comment Share on other sites More sharing options...
Chappie Posted December 2, 2008 Share Posted December 2, 2008 I was considering doing this on all our racks, irrespective of what they drive, but after discussing it with the manufacturer (QSC in this instance) I'm not going to bother, as in their opinion any benefit will be negligible if at all. The amps we use (Powerlight 2s, mostly) have switch-mode supplies with the primary reservoir located before the power transformer. The reservoir supplies energy equally to both the positive and negative rails, so inverting the signal polarity on one channel really won't gain us any headroom. Link to comment Share on other sites More sharing options...
KevinE Posted December 2, 2008 Share Posted December 2, 2008 I'm struggling to see how this can really help. For a start, the article says the caps are replenished 50 times a second, but surely he means 100 if using a bridge rectifier as surely all pro amps do? Secondly, few pro amps these days share a single split bus for both channels, they have their own toroidals or at least their own secondaries and their own reservoirs! ANd how about grounded bridge...again, very common!?! And that's before we use switch-mode. Link to comment Share on other sites More sharing options...
Rob_Beech Posted December 3, 2008 Share Posted December 3, 2008 But for limited mains? Link to comment Share on other sites More sharing options...
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