Sinusoidal, Pink Noise & Duty Cycles. - Page 2 - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 12th March 2009, 11:53 AM   #11
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
if you want W/ch, drive both channels full power into whatever load (8r for instance). the formula is E^2/R so if you get 28.3V rms, it's (28.3*28.3)/8 which should give 100.111 watts. total power would then be 200.222 watts, since you're driving both channels to full power. i have no isea where Peavey came up with the 58% figure, unless it was a calculation for heat dissipation or something, or maybe it's a correction factor for watts per channel if you test the power with only one channel driven to full power,
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 12th March 2009, 03:18 PM   #12
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
PV probbaly came up with the 58% figure from efficiency - the CS800 should be about 58% efficient at full power. If it's putting out 400 wpc, it will draw 1379 watts. Leaving a power dissipation of 579 watts. It will draw more than 1379 volt-amps because of the non-sinusiodal AC current draw so you can't use that to calculate thermal dissipation.

Measuring output power should be straightforward in principle. Volts (RMS) squared divided by ohms. The trouble is twofold. First, most modern amps will throw a fit and shut down when asked to dissipate 579 watts of heat. Compare the heat sinks in that old boat anchor vs. its newer bretheren, vs. a "comparable" QSC - RMX1450. No comparison. That figure grows substantially with amps "bigger" than a CS800. Second, 1379 watts can be 2000 or more volt-amps. The transformers can probably take this for an hour or more, but the mains breaker will trip in a few seconds. The test needs to be run quickly enough that the thermals aren't excessive, and the average current draw well under 20A. "Burst testing" is sometimes done - but if the burst is short enough you end up with inflated power numbers. 10 or 50 milliseconds won't drain the filter caps. One second on full sine, 5 seconds off is a good compromise. And a good amp should be able to take that for what would be the duration of a gig.
  Reply With Quote
Old 12th March 2009, 06:30 PM   #13
OMNIFEX is offline OMNIFEX  Jamaica
diyAudio Member
 
OMNIFEX's Avatar
 
Join Date: Mar 2003
Location: Locked Up In The Amp Rack
My confusion lies with the Crown PSA 2 & Macro-tech 2400 amplifier.

The PSA 2 offers 75-volt rails, two Power Transformers each, having its own 20-amp fuse.

The MA 2400 offers 57-volt rails, one power Transformer for each channel in addition to a 15-amp circuit breaker for each transformer.

The PSA 2 is 275 watts per channel @ 8 ohms, 460 watts in a 4-ohm load.

The MA 2400 is 515 watts per channel @ 8 ohms, 710 watts in a 4-ohm load.

When I calculate use the Volts times Volts divided by 4 ohms, I get a sum of 812.25 watts for the MA 2400.

When I calculate the PSA 2, I get 1406. 25 watts.


Can anyone explain what is happening here?

Cheers!
__________________
OMNIFEX
  Reply With Quote
Old 12th March 2009, 08:10 PM   #14
wg_ski is offline wg_ski  United States
diyAudio Member
 
Join Date: Oct 2007
First off, the MA2400 is a bridge configuration with floating supplies for each channel. The effective rail voltage is +/-114 using a normal topology.
And it isn't anything special like class G or H to reduce current consumption or dissipation - it is a hog.

Now in order to get stated performance for the 2400:
Unloaded supply = +/-114V
Assume 75% regulation: Vcc = 85.5V
Two sets of saturated transistor banks @ 5V each: Vpeak = 75.5V
Output voltage = 53.4V RMS, 712W/4R.
At 65% efficiency and 65% power factor the AC current draw would be 3370VA.


Now to get stated performance for the PSA2:
Unloaded supply = +/-75V
Assume 88% regulation: Vcc = 66V
One set of output transistors in saturation: Vpeak = 61V
Output voltage 43.1V RMS, 465W/4R.
At 65% efficiency and 65% power factor, the AC current draw would be 2200VA.


I would say that the PSA2 is more conservatively designed - that is, designed to be pushed harder or run at higher duty cycles, based on the overcurrent protection.
  Reply With Quote
Old 13th March 2009, 12:59 PM   #15
OMNIFEX is offline OMNIFEX  Jamaica
diyAudio Member
 
OMNIFEX's Avatar
 
Join Date: Mar 2003
Location: Locked Up In The Amp Rack
Cheers wg_ski!
__________________
OMNIFEX
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Does Pink noise follow the V x V/R method? OMNIFEX Solid State 18 5th January 2009 03:46 PM
What does pink noise sound like? jamikl Multi-Way 23 31st July 2008 02:23 AM
Pink Noise .wav generator MisterTwister Everything Else 10 30th April 2007 05:10 PM
Pink Noise generator Lyra Analog Line Level 12 22nd March 2006 09:30 PM
level of recorded pink noise MCPete Everything Else 6 17th January 2006 10:16 AM


New To Site? Need Help?

All times are GMT. The time now is 12:05 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2