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Author Topic: Crest Pro 8200 amps  (Read 36864 times)

Alan Sledzieski

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Re: Crest Pro 8200 amps
« Reply #10 on: July 21, 2010, 06:14:58 PM »

Tim McCulloch wrote on Wed, 21 July 2010 01:26

Alan Sledzieski wrote on Tue, 20 July 2010 19:36

As far as the regulator, / power consumption.

I did a show a few weeks ago, 115v into the ar 1215.  I ran 3 vs 1500's at just tickling the acl light all night.  So if i only had 13.5 amps available with a ar 1215, I don't see how they amp manufactures come up with power draw.

What I need to do is make a 12'' extension cord, with the hot and neutral apart from each other, put a digital clamp on amp meter on the hot leg, or neutral, and see whats actually going on.


As has been pointed out, with a dynamic signal like music, your measurement will be in vane.  The major amp manufacturers have current draw specifications for various duty cycles.  Pink noise with a 6db crest factor, with the peaks at hard clipping represents a 50% duty cycle.  I doubt your use is that intensive, so I suggest you look at the 1/8 and 1/3 duty cycles and either pick an average of them, or just go with the 1/3 duty cycle rating as the maximum you are likely to draw.

You don't need any type of "regulator" on the power amps.  Use it on something else, like console and outboard gear.

Have fun, good luck.

Tim Mc



I don't think my measurement would be in vain, it would actually show whats going on in real world conditions that the amps are subject to.  I don't really care what they draw when pink noise or other testing is being done.  i care about what they are drawing when a kick is tickling the acl circut, or the snare on the top end.  I've always struggled to find as many different circuits in a bar to make sure all is well, I'm seeing real world conditions are are lot lower for power consumption.

Not sure why you say not to run a regulator on a amp?  Please explain, thanks.

 If they are built and designed around 120v, I doubt they have the same output when voltage is at 105, which can be very common at some clubs i play at.  After you run through 150' of 12 gauge wire in the wall, then another 100' at times to the band, things get pretty scary.  Not to mention in the summer when clubs are running air conditioning and the distribution feeder is below the normal primary voltage, and the electric service is at its limit.

I can hear a difference and see the amps clip sooner when they have low voltage.

Most of the bigger car audio amps give 2 output ratings, 12 volts and 14.2 volts.

I have 4 ar 1215's
2 8200's on 1 ar 1215
1 to 2 ca9's and my board and processing on another
monitor amps and the band on another
And will run 2 more 8200's on the last ar 1215 when I use 4 double 18 box's.

Hoping to replace the 2 ca9's with 1 9200 in stereo, 2400 watss I believe.

My small rig is 9 kw on the bottom, 2 kw on top.  Out side I'll run 18kw on the bottom and 4 kw on the top. ( 4.8kw with a 9200)
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TJ (Tom) Cornish

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Re: Crest Pro 8200 amps
« Reply #11 on: July 22, 2010, 09:23:51 AM »

Alan Sledzieski wrote on Wed, 21 July 2010 17:14

Not sure why you say not to run a regulator on a amp?  Please explain, thanks.


Voltage regulators attempt to mask the problem of "Not Enough Juice For The Gig", a sister problem to "Not Enough Rig For The Gig".  

From a protection standpoint, power amps are the least picky of anything, many of which can continue to operate down to ridiculous levels, like 80 or 90 v, with reduced output as you mention.  A voltage regulator will not make a material difference in amp life.

From an absolute power standpoint I'm not convinced you get much more out of the wall outlet on a high-current load through a VR.  If you're getting 100 volts to the VR (is this a no load reading? You didn't say), it's boosting it 20% to get the voltage back up to 120, which increases the current from the wall 20% plus the thermal losses of the VR.  This puts more stress on your hundreds of feet of wire and the input supply voltage.  You may get a little more out, but you are at much greater risk of breaker tripping, melting your 150' extension cords, etc.

Instead of spending $500 per amp on voltage regulators, that money is much better spent on more efficient amps - ITechs, PL380s, Powersoft, amps with power factor correction, etc.  that can pull more usable watts out of whatever power they get, rather than just wasting power in two places - both in the VR and in an inefficient amp.

VRs may have a place for more sensitive stuff at FOH or on stage, but virtually no one is using them for amps.
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Brian Jojade

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Re: Crest Pro 8200 amps
« Reply #12 on: July 22, 2010, 05:11:11 PM »

TJ (Tom) Cornish wrote on Thu, 22 July 2010 08:23


Instead of spending $500 per amp on voltage regulators, that money is much better spent on more efficient amps - ITechs, PL380s, Powersoft, amps with power factor correction, etc.  that can pull more usable watts out of whatever power they get, rather than just wasting power in two places - both in the VR and in an inefficient amp.

VRs may have a place for more sensitive stuff at FOH or on stage, but virtually no one is using them for amps.



Agreed.  Spend money on more efficient amps or thicker power cables to reduce voltage loss.  A power amp's demands are extremely dynamic.  While they might be pulling 2-3 amps to play that guitar solo, the kick drum could easily be asking for 20+ amps in very short bursts.  Average power is much lower so the breaker doesn't trip.  If you get massive voltage sag during those periods of kick, the amp taps into its reserve caps for power.  When they are drained, there ain't no more for the speakers and your sound gets thin.  Higher end amps can deal with this better as they typically have more cap reserves waiting.

You can run an amp with a ridiculously low amount of power provided to them, but the performance will suffer when you do.  Remember that watts don't come out of thin air.  A 20 amp circuit at 120 volts is 2400 watts.  If your amp was 100% efficient, that is the maximum power you can get out of it.  Reality is closer to the 80% mark, so you're looking less than 2000 watts available to you sustained.  

In live sound, the kick is usually the peak in your audio, and that's only an extremely short duration so you can get by with less power.  Give the same setup to a DJ that loves wasting energy on bass, and you'll see the breaker trip a lot faster.  They will drive the amp to the 1/3 sustained power and beyond.
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Alan Sledzieski

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Re: Crest Pro 8200 amps
« Reply #13 on: July 22, 2010, 05:31:20 PM »

TJ (Tom) Cornish wrote on Thu, 22 July 2010 09:23

Alan Sledzieski wrote on Wed, 21 July 2010 17:14

Not sure why you say not to run a regulator on a amp?  Please explain, thanks.


Voltage regulators attempt to mask the problem of "Not Enough Juice For The Gig", a sister problem to "Not Enough Rig For The Gig".  

From a protection standpoint, power amps are the least picky of anything, many of which can continue to operate down to ridiculous levels, like 80 or 90 v, with reduced output as you mention.  A voltage regulator will not make a material difference in amp life.

From an absolute power standpoint I'm not convinced you get much more out of the wall outlet on a high-current load through a VR.  If you're getting 100 volts to the VR (is this a no load reading? You didn't say), it's boosting it 20% to get the voltage back up to 120, which increases the current from the wall 20% plus the thermal losses of the VR.  This puts more stress on your hundreds of feet of wire and the input supply voltage.  You may get a little more out, but you are at much greater risk of breaker tripping, melting your 150' extension cords, etc.

Instead of spending $500 per amp on voltage regulators, that money is much better spent on more efficient amps - ITechs, PL380s, Powersoft, amps with power factor correction, etc.  that can pull more usable watts out of whatever power they get, rather than just wasting power in two places - both in the VR and in an inefficient amp.

VRs may have a place for more sensitive stuff at FOH or on stage, but virtually no one is using them for amps.


Interesting. Would i be correct in assuming this?
If a amp puts out 5000w at 120 volts, would it put out 3333 watts at 80 volts?

I understand you do not get more out of the wall in terms of current capacity.  As voltage drops, current goes up.  The wall outlet and wire is protected from the breaker, so there's little chance of melting a wire.

If voltage is low would a amp tend to run hotter because of increased current?

As far as more efficient amps, after hearing and seeing a crown xti on bottom end i would never trust any of crowns newer equipment.  That's just my opinion.

ar 1215's can be bought for $350, that's $1400 to cover my $25,000 dollar system.

If you had a choice of running your amps at 120 v + or - 5 volts or 80, what would you pick?  

It will be very hard for me to ever try a different amp other then a crest.  I love the sound, performance, and durability.

As far as regulators and capacitors.  The 120 volts at you wall pass's through quite a few regulators before it gets to you.  Regs at the generation plant, then regs at the substation, then regs on the individual feeders also.  They all step up, or step down the voltage, most of the time there stepping it up, this raises the voltage on the load side, but also raises the current on the line side.  This is done so the transformer will put out 113 to 124v.  Thats what is needed at your weather head to pass industry standards.  Being a lineman we fight low voltage complaints quite a bit.

I'm not arguing that a amp is the least effected by low voltage, but if there's a way to keep the voltage near 120 I'll spend the little extra money on regs

Thanks for your input,
Al
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Alan Sledzieski

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Re: Crest Pro 8200 amps
« Reply #14 on: July 22, 2010, 06:02:16 PM »

Just looked at some of the amps that were listed.

I techs, The it6000 goes for just under $5000

the pl 380 is class d amp, I have never hear a good d amp.  I run Rotell amps in my home theater. Rb 1080, a ab amp around 200 wpc, There class d amp that was twice as expensive,and twice or 3 times the rated power, fell on its face compared to the rb 1080.

I have Bowers and Wilksons asw 650 subs.  Its a 12 inch 200 w ab amp.  It blows away the asw675 1000w class d amp.Its tighter and hits harder

Car amps are the same, crazy output, that just fall on there face.

The d amps seem quite efficient, but don't sound so good to my ears.

Never heard of the power soft stuff, looks impressive as far as specs.

Someone said you can't get power out of thin air, thats true for sure.  How do these d amps get so much output?  One part is at the cost of sound quality I know that.

It seems like if you have 1 kw of ab or class h amps, you need 4 kw in a class d amp to get you close as far as headroom, sound quality.

I can't afford $20k in itech amps to run my subs.

I just got 4 8200's for $3400 total, $700 in regs, 18 kw as each sub gets a amp bridged at 4.5 kw.
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Bob Lee (QSC)

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Re: Crest Pro 8200 amps
« Reply #15 on: July 22, 2010, 06:07:29 PM »

Alan Sledzieski wrote on Thu, 22 July 2010 14:31


As voltage drops, current goes up.


Only if you use one of those voltage regulators that the pros here have advised you not to use on power amps.

Quote:

If voltage is low would a amp tend to run hotter because of increased current?


No, because the current will decrease.
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Alan Sledzieski

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Re: Crest Pro 8200 amps
« Reply #16 on: July 22, 2010, 06:35:44 PM »

Bob Lee (QSC) wrote on Thu, 22 July 2010 18:07

Alan Sledzieski wrote on Thu, 22 July 2010 14:31


As voltage drops, current goes up.


Only if you use one of those voltage regulators that the pros here have advised you not to use on power amps.

Quote:

If voltage is low would a amp tend to run hotter because of increased current?


No, because the current will decrease.




Interesting.

P = V x A

1200 watts = 120 volts x 10 amps

1200 watts = 100 volts x 12 amps ?

Still confused why someone would want to run at 100 v when you could run them at 120 fairly cheap for a small system like mine.
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Brian Jojade

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Re: Crest Pro 8200 amps
« Reply #17 on: July 22, 2010, 06:38:10 PM »

At 100 volts, your amp isn't going to be delivering the same 1200 watts.  It will go into clip sooner.  If you use your voltage regulator to bring it up to 120 volts, the same 10 amps is available to the amp, but it needs 12 amps out of the wall to do it.

The result is a higher chance of tripping your supply breaker the lower the voltage gets.
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Alan Sledzieski

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Re: Crest Pro 8200 amps
« Reply #18 on: July 22, 2010, 07:15:46 PM »

Brian Jojade wrote on Thu, 22 July 2010 18:38

At 100 volts, your amp isn't going to be delivering the same 1200 watts.  It will go into clip sooner.  If you use your voltage regulator to bring it up to 120 volts, the same 10 amps is available to the amp, but it needs 12 amps out of the wall to do it.

The result is a higher chance of tripping your supply breaker the lower the voltage gets.



Thanks,

Thats kinda what I was getting at some place in the beginning.  If 2 8200's are not tripping the 15 amp breaker on the 1215, the 20 amp wall circuit will be fine.  15 amps output of the ar 1215 should yield a draw of 17.6 amps on the load side at 100v input.

Stepping the voltage up 20v does not cost you much current draw on the line side.  Also you get more out of your amps.

The other nice part about the ar 1215 is it has a low voltage and high voltage shutdown.  If you loose the neutral between the 2 hotlegs of a 120-240 volts service, you can get huge voltage swings very quickly.  You could have 80 on 1 leg 160 on the other, depending on how each side is loaded.  Or any combination of voltages adding up to 240.
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TJ (Tom) Cornish

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Re: Crest Pro 8200 amps
« Reply #19 on: July 22, 2010, 08:25:55 PM »

Alan Sledzieski wrote on Thu, 22 July 2010 17:02

Just looked at some of the amps that were listed.

I techs, The it6000 goes for just under $5000

the pl 380 is class d amp, I have never hear a good d amp.  I run Rotell amps in my home theater. Rb 1080, a ab amp around 200 wpc, There class d amp that was twice as expensive,and twice or 3 times the rated power, fell on its face compared to the rb 1080.

I have Bowers and Wilksons asw 650 subs.  Its a 12 inch 200 w ab amp.  It blows away the asw675 1000w class d amp.Its tighter and hits harder

Car amps are the same, crazy output, that just fall on there face.

The d amps seem quite efficient, but don't sound so good to my ears.

Never heard of the power soft stuff, looks impressive as far as specs.

Someone said you can't get power out of thin air, thats true for sure.  How do these d amps get so much output?  One part is at the cost of sound quality I know that.

It seems like if you have 1 kw of ab or class h amps, you need 4 kw in a class d amp to get you close as far as headroom, sound quality.

I can't afford $20k in itech amps to run my subs.

I just got 4 8200's for $3400 total, $700 in regs, 18 kw as each sub gets a amp bridged at 4.5 kw.

Do some searching here and you will find that many of your opinions on class D are not shared by the majority of users.  The PL380 and ITechs sound great.  I'm told the Powersofts do to, though I don't have personal experience.  There are a number of used ITechs and PL380s that appear on the forum Marketplace regularly for between $1500 and $2000 depending on model and age.  Those are good buys.  
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