New Lightweight Power Amp Ratings

[John Roberts]

Re: New Lightweight Power Amp Ratings

I think what he's saying is that the performance will be as expected given the price, because that's what we (the buying population) keep driving them to produce.

Jason

Thanks... yes mostly... Improvements in technology has driven down the cost of all power amps strong and wimpy. I recall when $1/watt was cheap... but since then that 1 watt has also been somewhat degraded by lesser duty cycles. This mix of weaker duty cycle amps has been reinforced by customers rewarding cheaper solutions that work for them.

Specifically regarding the new crop of cheaper power amps, I suspect most of the cost reduction is from new technology, not weaker performance but as I have repeated multiple times, there is no easy way to characterize duty cycle that is meaningful, so we need to wait for reports from actual users in the marketplace to learn how these new amps work in real applications.

If the manufacturers have half a clue they should be merchantable (fancy way of saying they should work). However, i don't expect the cheapest value brand to ship an amp that wildly exceed expectations. if they do, they likely missed their design target by overshooting.

Good luck, and listen for user reports.

JR

 

[Chris Van Duker]

Re: New Lightweight Power Amp Ratings

I saw a video recently regarding the IPR 7500 here. I snapped a still from the video showing the guts, here:


A few interesting things I noticed about it: Most obviously, there's a lot of stuff in there. This is certainly not a nearly-empty chassis like the smaller amps in the series are. You can see some fairly beefy caps, chokes, and heat sinks in there. I thought the left-to-right airflow using 3 fans was interesting. Also noticed that it's built "upside-down", similar to the PLX series, to keep stuff from settling on the main circuit board. It will be interesting to hear how these perform.

-Chris

 

[John Roberts]

Re: New Lightweight Power Amp Ratings

I saw a video recently regarding the IPR 7500 here. I snapped a still from the video showing the guts, here:
View attachment 4485

A few interesting things I noticed about it: Most obviously, there's a lot of stuff in there. This is certainly not a nearly-empty chassis like the smaller amps in the series are. You can see some fairly beefy caps, chokes, and heat sinks in there. I thought the left-to-right airflow using 3 fans was interesting. Also noticed that it's built "upside-down", similar to the PLX series, to keep stuff from settling on the main circuit board. It will be interesting to hear how these perform.

-Chris

I wouldn't be so sure that orientation of design has much to do with gravity and loose "stuff". With 3 fans and forced air cooling, even convection is not very suspect. Hot air rises, so that can be a factor in passively cooled amps. I've seen passively cooled install amps that put out less power if mounted at a right angle to normal.

The larger and extra parts are no doubt related to making more power than base reference design.

JR

 

[Ivan Beaver]

Re: New Lightweight Power Amp Ratings

I saw a video recently regarding the IPR 7500 here. I snapped a still from the video showing the guts, here:
View attachment 4485

A few interesting things I noticed about it: Most obviously, there's a lot of stuff in there. This is certainly not a nearly-empty chassis like the smaller amps in the series are. You can see some fairly beefy caps, chokes, and heat sinks in there. I thought the left-to-right airflow using 3 fans was interesting. Also noticed that it's built "upside-down", similar to the PLX series, to keep stuff from settling on the main circuit board. It will be interesting to hear how these perform.

-Chris

As I understand it-the reason the QSC's are mounted with the circuit board on the top (components facing down) is so that if water gets in them (outdoor gis etc) it would have little chance of getting on the circuit board and causing damage. I could be wrong-but that is what I was told.

 

[John Roberts]

Re: New Lightweight Power Amp Ratings

Is that supposed to be a high probability scenario (yes I know rain happens, but I hope you turn off all amps with rain water or other beverages inside, even QSC)? At least a good story like that stops the pesky questions for a while.

I have packaged several products with the board upside down wrt the front, because it was more convenient to locate some PC mounted jacks or controls.

Perhaps in a passively cooled amp it could affect the accumulation of dust bunnies, while I don't know how problematic they are.

JR

 

[Caleb Dueck]

Re: New Lightweight Power Amp Ratings

Water doesn't only 'interact with' electronics when outdoors. A new install project had a leak in the roof - a few gallons of water made their way into an AV rack.

 

[Tim Duffin]

Re: New Lightweight Power Amp Ratings

Thanks... yes mostly... Improvements in technology has driven down the cost of all power amps strong and wimpy. I recall when $1/watt was cheap... but since then that 1 watt has also been somewhat degraded by lesser duty cycles. This mix of weaker duty cycle amps has been reinforced by customers rewarding cheaper solutions that work for them.

Specifically regarding the new crop of cheaper power amps, I suspect most of the cost reduction is from new technology, not weaker performance but as I have repeated multiple times, there is no easy way to characterize duty cycle that is meaningful, so we need to wait for reports from actual users in the marketplace to learn how these new amps work in real applications.

If the manufacturers have half a clue they should be merchantable (fancy way of saying they should work). However, i don't expect the cheapest value brand to ship an amp that wildly exceed expectations. if they do, they likely missed their design target by overshooting.

Good luck, and listen for user reports.

JR

JR,

What would you think about a measurement method that integrates the total amount of joules of energy from an amp over a long period of time at different frequencies?

For instance, Integrate the total number of joules of energy from an amp at 1 frequency (20k) at 100% output voltage for a period of 8 hours at its lowest stable impedance, say 1.8ohms per channel. Then compare that with the same amp with the same load and same level at 19khz, then 18 etc. THEN, integrate the total amount of energy from all frequencies at max voltage and lowest impedance to arrive at the absolute max amount of energy that this amp can source at a show. Then, to be fair to current limited amps, perform all of those calculations at all useful impedances from 1ohm to 16ohms. Then integrate those results. For the truly anal, one could further perform all of these calculations again at different line voltages.

I think only then will anyone be able to tell with any certainty that amp A actually has more power capability that amp B.

In my mind this would unveil which amps truly have the thermal capability advertised and which amps are nothing more than marketing in a box.

 

[John Roberts]

Re: New Lightweight Power Amp Ratings

JR,

What would you think about a measurement method that integrates the total amount of joules of energy from an amp over a long period of time at different frequencies?

For instance, Integrate the total number of joules of energy from an amp at 1 frequency (20k) at 100% output voltage for a period of 8 hours at its lowest stable impedance, say 1.8ohms per channel. Then compare that with the same amp with the same load and same level at 19khz, then 18 etc. THEN, integrate the total amount of energy from all frequencies at max voltage and lowest impedance to arrive at the absolute max amount of energy that this amp can source at a show. Then, to be fair to current limited amps, perform all of those calculations at all useful impedances from 1ohm to 16ohms. Then integrate those results. For the truly anal, one could further perform all of these calculations again at different line voltages.

I think only then will anyone be able to tell with any certainty that amp A actually has more power capability that amp B.

In my mind this would unveil which amps truly have the thermal capability advertised and which amps are nothing more than marketing in a box.

I wrote about this at length back when Bink did his big power amp shoot out years ago. Measuring amp duty cycle is not the hard part. The hard part is coming up with meaningful less than 100% duty cycle targets that customers can look at and determine if it is more or less than they need. The marketplace has spoken very loudly that they will not pay for 100% duty cycle amps, and will reward amps that cost effectively give them just enough without making them pay for excess capability that they don't need. Putting a number to this opens up an arms race between the amp makers to deliver, just a little more than the next guy, while not so much it hurts pricing/profit.

Ironically perhaps the higher the power point, like with modern big dog amps, the less likely you could ever use 100% duty cycle (even you Tim).

It might be of academic interest for some to know which amp puts out more duty cycle than others in a "my thing is longer than your thing" way, but as long as it puts out enough that is all that is needed for cost effective performance (at least that's what she said.)

The difficult thing about trying to define a X% (less than 100%) duty cycle test stimulus waveform, is what test waveform could possibly represent all customer's typical needs. As I have posted already a mirror image variant of something like loudspeaker power handling tests (band passed noise) could come up with "a" number but not "the" number.

i see no incentive for manufacturers to come up with a new specification, that they would all just try to game for marketing advantage. From my past experience with consumers misunderstanding even simple amp specs, something this complex would probably cause more bad decision making than good with power amp purchases.

The best gauge IMO for new power amps is to listen to early user reports. They will quickly determine if they hang or not. If weak, the new amp will sink to some appropriate user level, or go away if not a true value. If strong they will win increasing market share as the word gets out and they up the cost/benefit calculus.

A appreciate this is rather unscientific, but i do not believe more science would actually help consumers. Amps have been in this "less than 100% duty cycle" gray area for decades and managed so far. Modern technology is making it easier/cheaper to deliver more duty cycle (using saturated switch outputs) so this should become less of an issue not more. While value amp makers are always rewarded for working the margins and pushing the envelope.

Trust (no one) but verify....

JR

PS: As I have also mentioned amp designers routinely use some favorite pre-recorded tracks or maybe a board tape that works for them to represent their customer's expectations. It would be pretty easy to come up some standard sound files, but less easy to make them universally meaningful, for all customers and all applications.

 

[Ivan Beaver]

Re: New Lightweight Power Amp Ratings

I wrote about this at length back when Bink did his big power amp shoot out years ago. Measuring amp duty cycle is not the hard part. The hard part is coming up with meaningful less than 100% duty cycle targets that customers can look at and determine if it is more or less than they need. The marketplace has spoken very loudly that they will not pay for 100% duty cycle amps, and will reward amps that cost effectively give them just enough without making them pay for excess capability that they don't need. .

I remember several decades ago (back in the 100% duty cycle days-like the amps on one whole wall of my office/lab) when a wise man said "what we really need is a 100 watt continuous amp that can deliver 10,000 watt peaks" This would allow for 20 dB peaks. Of course that was before the days of sustained low freq.

 

[John Roberts]

Re: New Lightweight Power Amp Ratings

I remember several decades ago (back in the 100% duty cycle days-like the amps on one whole wall of my office/lab) when a wise man said "what we really need is a 100 watt continuous amp that can deliver 10,000 watt peaks" This would allow for 20 dB peaks. Of course that was before the days of sustained low freq.

I actually designed an amp that intentionally put out short term peak power roughly 4x the long term continuous power. I had planned to do a full series of power points but started out with the smallest one first. The small amp (AMR PMA70+) put out 35W continuous, 60W for around 15 seconds, and 120W peak for several mSec. For most applications it sounded like a 100W+ amp but was sized and cost closer to the 35W amp. This was used to power monitor speakers for bedroom recording and kicked pretty good in that modest application.

Unfortunately it turns out the 1980s amp technology did not scale up as cheaply for higher power points, but the general approach can certainly be applied to modern class D amps by how much long term power the power supply for the amp can deliver.

Real world music is not continuous tones (while some bass bandpasses can get close for sustained periods).

JR

 

[Steve Payne]

Re: New Lightweight Power Amp Ratings

Is that supposed to be a high probability scenario (yes I know rain happens, but I hope you turn off all amps with rain water or other beverages inside, even QSC)? At least a good story like that stops the pesky questions for a while.
JR

Even if it is an unintended byproduct, any design that makes a product more impervious to water penetration/damage is a big plus in my mind. In the world of outdoor summer festivals, sudden and sometimes violent rainstorms are par for the course. Doing the "fire drill" to get everything tarped and adequately protected in time is a regular routine. Invariably, once or twice every season we find our gear spread around the warehouse with the lids opened up and the fans blowing to dry everything out. FWIW.