Sinusoidal, Pink Noise & Duty Cycles.
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 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
 12th March 2009, 11:53 AM #11 unclejed613   diyAudio Member     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
 12th March 2009, 03:18 PM #12 wg_ski   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.
 12th March 2009, 06:30 PM #13 OMNIFEX   diyAudio Member     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
 12th March 2009, 08:10 PM #14 wg_ski   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.
 13th March 2009, 12:59 PM #15 OMNIFEX   diyAudio Member     Join Date: Mar 2003 Location: Locked Up In The Amp Rack Cheers wg_ski! __________________ OMNIFEX

 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 Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Holton Precision Audio         CSS         Dx Classic Amplifiers         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post OMNIFEX Solid State 18 5th January 2009 03:46 PM jamikl Multi-Way 23 31st July 2008 02:23 AM MisterTwister Everything Else 10 30th April 2007 05:10 PM Lyra Analog Line Level 12 22nd March 2006 09:30 PM 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.