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Author Topic: Increasing Amp power-Dave Rat article  (Read 5259 times)

Mario Roman

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Increasing Amp power-Dave Rat article
« on: April 18, 2011, 11:14:20 am »

Hi All,

I just read an article here written by Dave Rat and I'm curious of what others think. I have a couple of questions too. Here's the link: http://www.prosoundweb.com/article/fighting_for_power_a_way_for_amplifiers_to_increase_actual_power_delivered_/
Question one: Dave says they run all their amps in bridge/mono mode for optimum system performance but I've heard the opinion of many on these forums that running in this mode increases the THD of the amp which negatively effects sound quality and most prefer to not run in bridge mono for this reason.....opinions??

Qusetion two: Dave states that all the bridge/mono switch does is reverse the polarity of the B channel. My experience is that it also ties the outputs to input A only. If this it true then Dave's method will only work if your running a mono mix. Running stereo (which is how I run my system so I can pan the drums and stereo the guitar out of the center) it is not possible to use his method. Am I correct in this?? Thanks.

Mario
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Ivan Beaver

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Re: Increasing Amp power-Dave Rat article
« Reply #1 on: April 18, 2011, 12:00:25 pm »

Hi All,

I just read an article here written by Dave Rat and I'm curious of what others think. I have a couple of questions too. Here's the link: http://www.prosoundweb.com/article/fighting_for_power_a_way_for_amplifiers_to_increase_actual_power_delivered_/
Question one: Dave says they run all their amps in bridge/mono mode for optimum system performance but I've heard the opinion of many on these forums that running in this mode increases the THD of the amp which negatively effects sound quality and most prefer to not run in bridge mono for this reason.....opinions??

Qusetion two: Dave states that all the bridge/mono switch does is reverse the polarity of the B channel. My experience is that it also ties the outputs to input A only. If this it true then Dave's method will only work if your running a mono mix. Running stereo (which is how I run my system so I can pan the drums and stereo the guitar out of the center) it is not possible to use his method. Am I correct in this?? Thanks.

Mario

It only works on certain types of amps and is tied to how the power supply is handled.  Amps with a sperate power supply for each channel will not generate any more power.

Yes it inverts the B channel with respect to the A channel.  And ties the B channel input to the A channel input.  This only works if you are sending the same signal to both outputs-which is not the case in stereo.

So you would need 2 amplifiers with 4 loudspeakers hookedup to do this in stereo.
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Chris Hindle

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Re: Increasing Amp power-Dave Rat article
« Reply #2 on: April 18, 2011, 12:12:36 pm »

Hi All,

I just read an article here written by Dave Rat and I'm curious of what others think. I have a couple of questions too. Here's the link: http://www.prosoundweb.com/article/fighting_for_power_a_way_for_amplifiers_to_increase_actual_power_delivered_/
Question one: Dave says they run all their amps in bridge/mono mode for optimum system performance but I've heard the opinion of many on these forums that running in this mode increases the THD of the amp which negatively effects sound quality and most prefer to not run in bridge mono for this reason.....opinions??

Qusetion two: Dave states that all the bridge/mono switch does is reverse the polarity of the B channel. My experience is that it also ties the outputs to input A only. If this it true then Dave's method will only work if your running a mono mix. Running stereo (which is how I run my system so I can pan the drums and stereo the guitar out of the center) it is not possible to use his method. Am I correct in this?? Thanks.

Mario

Q1: Dave is not running the amp in bridge mono. He is just using the bridge switch to invert 1 of teh inputs. THD doesn't change.

Q2: RTFM. It depends on the amp. Some require you to "match input knobs", others require you to set levels on A. There may be other variations as well.
If you need to match knobs, you're OK. Tied to input A gain, dunno what would happen. Probably not good.

Important note - amps with 2 power supplies will not see any benefit from this mod.
Note 2 - If you go this way, usa a bloody patch panel. Nothing worse than having to remember which a way you plug em in ! (the speakers, that is)

Chris.
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Tim McCulloch

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Re: Increasing Amp power-Dave Rat article
« Reply #3 on: April 18, 2011, 12:23:42 pm »

Hi All,

I just read an article here written by Dave Rat and I'm curious of what others think. I have a couple of questions too. Here's the link: http://www.prosoundweb.com/article/fighting_for_power_a_way_for_amplifiers_to_increase_actual_power_delivered_/
Question one: Dave says they run all their amps in bridge/mono mode for optimum system performance but I've heard the opinion of many on these forums that running in this mode increases the THD of the amp which negatively effects sound quality and most prefer to not run in bridge mono for this reason.....opinions??

Qusetion two: Dave states that all the bridge/mono switch does is reverse the polarity of the B channel. My experience is that it also ties the outputs to input A only. If this it true then Dave's method will only work if your running a mono mix. Running stereo (which is how I run my system so I can pan the drums and stereo the guitar out of the center) it is not possible to use his method. Am I correct in this?? Thanks.

Mario

Also note that at best you get *maybe* 1.5dB of additional output.  If you're already running WFO, that additional output will likely be consumed in power compression.
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John Roberts {JR}

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Re: Increasing Amp power-Dave Rat article
« Reply #4 on: April 18, 2011, 12:47:51 pm »

Hi All,

I just read an article here written by Dave Rat and I'm curious of what others think. I have a couple of questions too. Here's the link: http://www.prosoundweb.com/article/fighting_for_power_a_way_for_amplifiers_to_increase_actual_power_delivered_/
Question one: Dave says they run all their amps in bridge/mono mode for optimum system performance but I've heard the opinion of many on these forums that running in this mode increases the THD of the amp which negatively effects sound quality and most prefer to not run in bridge mono for this reason.....opinions??

Qusetion two: Dave states that all the bridge/mono switch does is reverse the polarity of the B channel. My experience is that it also ties the outputs to input A only. If this it true then Dave's method will only work if your running a mono mix. Running stereo (which is how I run my system so I can pan the drums and stereo the guitar out of the center) it is not possible to use his method. Am I correct in this?? Thanks.

Mario

This would be an excellent topic to research in the archives, as this has been explored at length, numerous times.

My short answer is the benefit is pretty slender, and potential for getting things wrong real, so YMMV.

 It is the human condition to pursue something for nothing schemes.. good luck, what's the worst thing that could happen?   8)

JR
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Greg_Cameron

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Re: Increasing Amp power-Dave Rat article
« Reply #5 on: April 18, 2011, 02:05:23 pm »

Question one: Dave says they run all their amps in bridge/mono mode for optimum system performance but I've heard the opinion of many on these forums that running in this mode increases the THD of the amp which negatively effects sound quality and most prefer to not run in bridge mono for this reason.....opinions??

FWIW, that article is pretty old now. I believe it was written over 10 years ago and was based on their Rat Trap 5 system configuration. Rat Sound is pretty much an all L'Acoustics house now for main speakers and have mostly retired and sold off pieces the Rat Trap 5 systems, save for some inventory used for smaller festival stages and side fill monitors. That said, I own some of their racks & stacks which the article is discussing. To answer your question about bridging, it's true that the amps for the subs, the 15", and the 10" drivers are all run bridge mode. The amps are all the old Crest x001 series amps which are very robust and can easily handle the thermal stress of bridged low impedance loads. That fact that some of these amps are nearing 20 years old and are still running great after being toured & pounded relentlessly says a lot about their design and construction. They also don't have anymore *audible* distortion running bridged vs. stereo on the bandpasses they're being used on. The amps for the 2" JBL drivers and 1" TAD or EV drivers are running stereo since not that much power is required to drive them to full output.

Now that that market is flooded with cheap amps that claim they're usable down to 4 ohms, it may not be wise to run such amps that way. In my experience, cheap amps have limited thermal capacity and aren't likely to hold up over the long or even short term very well if you run them bridged and hammer them a lot.

Qusetion two: Dave states that all the bridge/mono switch does is reverse the polarity of the B channel. My experience is that it also ties the outputs to input A only. If this it true then Dave's method will only work if your running a mono mix. Running stereo (which is how I run my system so I can pan the drums and stereo the guitar out of the center) it is not possible to use his method. Am I correct in this??

You're correct that the bridge connects the A input to the B channel but with swapped polarity. The point of the article is that you can potentially benefit from a bit of increased output when 2 identical signals are being reproduced by each amp channel. If you're running a different signal type into each channel, doing the Dave Rat trick may have little or no benefit. But if the signals are identical & the power supply topology is as described, you'll see the benefit since each channel will be drawing from a different reservoir on the power supply. If they're both drawing on the same side at the same time with identical signals, that single reservoir will drain faster. Pretty simple really.

Greg

[edit: spelling]
« Last Edit: April 18, 2011, 07:04:01 pm by Greg Cameron »
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Mario Roman

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Re: Increasing Amp power-Dave Rat article
« Reply #6 on: April 18, 2011, 03:25:52 pm »

FWIW, that article is pretty old now. I believe it was written over 10 years ago and was based on their Rat Trap 5 system configuration. Rat Sound is pretty much an all L'Acoustics house now for main speakers and have mostly retired and sold off pieces the Rat Trap 5 systems, save for some inventory used for smaller festival stages and side fill monitors. That said, I own some of their racks & stacks which the article is discussing. To answer your question about bridging, it's true that the amps for the subs, the 15", and the 10" drivers are all run bridge mode. The amps are all the old Crest x001 series amps which are very robust and can easily handle the thermal stress of bridged low impedance loads. That fact that some of these amps are nearing 20 years old and are still running great after being toured & pounded relentlessly says a lot about their design and construction. They also don't have anymore *audible* distortion running bridged vs. stereo on the bandpasses they're being used on. The amps for the 2" JBL drivers and 1" TAD or EV drivers are running stereo since not that much power is required to drive them to full output.

Now that that market is flooded with cheap amps that claim they're usable down to 4 ohms, it may not be wise to run such amps that way. In my experience, cheap amps have limited thermal capacity and aren't likely to hold up over the long or even short term very well if you run them bridged and hammer them a lot.

You're correct that the bridge connects the A input to the B channel but with swapped polarity. The point of the article is that you can potentially benefit from a bit of increased output when 2 identical signals are being reproduced by each amp channel. If you're running a different signal type into each channel, doing the Dave Rat trick may have little or no benefit. But if the signals are identical & the power supply topology is as described, you'll see the benefit since each channel will be drawing from a different receiver on the power supply. If they're both drawing on the same side at the same time with identical signals, that single reservoir will drain faster. Pretty simple really.

Greg

Just curious, if this article is 10 years old then why is it dated April 14th 2011? What am I missing? I do understand everyones replies and they confirm what I suspected. Thanks

Mario
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Randall Hyde

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Re: Increasing Amp power-Dave Rat article
« Reply #7 on: April 18, 2011, 03:57:47 pm »

Just curious, if this article is 10 years old then why is it dated April 14th 2011? What am I missing? I do understand everyones replies and they confirm what I suspected. Thanks

Mario
Because PSW has a habit of bringing old articles to the forefront every now and then. A few months back I went through and read all 450 or so articles (at the time) in the archives. Probably 2-3 times a month I now see some of the older articles I've read. This activity on PSW's part isn't bad -- most people don't have the endurance to go through and read all the articles like I did, so bring a few "oldies but goodies" to everyone's attention isn't a bad idea.
cheers,
Randy Hyde
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Mario Roman

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Re: Increasing Amp power-Dave Rat article
« Reply #8 on: April 18, 2011, 06:52:05 pm »

Because PSW has a habit of bringing old articles to the forefront every now and then. A few months back I went through and read all 450 or so articles (at the time) in the archives. Probably 2-3 times a month I now see some of the older articles I've read. This activity on PSW's part isn't bad -- most people don't have the endurance to go through and read all the articles like I did, so bring a few "oldies but goodies" to everyone's attention isn't a bad idea.
cheers,
Randy Hyde

Agreed, makes sense now. Thanks

Mario
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Re: Increasing Amp power-Dave Rat article
« Reply #8 on: April 18, 2011, 06:52:05 pm »


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