500W PA amplifier with Limiter
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 20th January 2013, 11:34 AM #2401 tranceanddance   diyAudio Member     Join Date: Jan 2013 thank a lot! 1vac=1.2vrms ? is it always working formula? i need psu with 55vac*2 ? for npn-pnp transistors scheme... +55 to pnp and -55to npn? so if u=55, why on the original scheme b500 written +-90Vmax ? and why we double amperes for 2 chanels (11*2) but dont double voltage ? Last edited by tranceanddance; 20th January 2013 at 11:39 AM.
 20th January 2013, 03:00 PM #2402 tranceanddance   diyAudio Member     Join Date: Jan 2013 Ppsu=25A*55vac=1375VA but apexaudio said he use 1000va transformer for this amp, and somebody here use even less VA psu... as I understood we can use less VA psu but then we have upper our voltage,what is algorythm here ? sorry for too much quiestions...the problem is to get 1000-1500va trans here..it is very expensive..so am wondering if its possible to use less VA trans and just upper the voltage of trans...but i cannot understand algirythm of uppering the voltage for example, how much voltage I need for 700VA trans to get 1000wt on stereo, or its not possible? why apexaudio on original scheme wrote Vmax=+-90V..not+-55 as we calculated ?!
 20th January 2013, 03:25 PM #2403 wattaniya diyAudio Member   Join Date: Oct 2009 use 80vdc, ct ,80vdc for safety operation.(55vac, ct ,55vac secondary). u can get 500w with 4 ohm with 90vdc if u use mjl21195/96 or mjl4281. 90vdc for mjl number transistors.
 20th January 2013, 03:37 PM #2404 tranceanddance   diyAudio Member     Join Date: Jan 2013 do u mean 55vac=80vdc? the voltage goes up after capacitors in PSU ? by which formula you calculated it? what means ct? ct=0,ct=ground,ct=?) by the way all comes more clear for me, thank you Brothers ) ps still I cannot understand, why apexaudio use 1000va trans and its ok, the formula said it should be 1375va (25A*55vac) Last edited by tranceanddance; 20th January 2013 at 03:45 PM.
 20th January 2013, 03:45 PM #2405 wattaniya diyAudio Member   Join Date: Oct 2009 ct means center tap of the transformer in secondary , also say gnd. 55vac after smoothing capacitors charged, the voltage will be 75vdc to 80vdc.
 20th January 2013, 03:53 PM #2406 tranceanddance   diyAudio Member     Join Date: Jan 2013 thank you ! also I have to understand how to take voltage on 2 chanels from 1 transformer. so I have on secondary 3 taps, first +55, second CT, third -55 , right? +55 I give to one part of transistors in one chanel, -55 i give to another part of transistores in the same chanel.... and from where I shoud take voltage to second chanel ? from the same pots that I used for first chanel?
 20th January 2013, 04:03 PM #2407 wattaniya diyAudio Member   Join Date: Oct 2009 secondary 55vac,ct,55ac after rectified with smoothing capacitors, u will get +75vdc ct -75 or +80vdc, ct,-80vdc. if ur transformer 1000va or watts +75 goes to positive side of the amp -75vdc goes negative side of the amp, and ct is gnd, use 8,10000uf /100v caps for psu, give psu positve to two channels, negative to two chanels. and the gnd also for two channels.
 20th January 2013, 04:21 PM #2408 tranceanddance   diyAudio Member     Join Date: Jan 2013 thanks a lot, you mean 8*10000uf to get at all 80000uf? is it enough for deep bass with highest volume possible to hear clear sound? by which way I can calculate how much uf I need for ? ps: this amp working in class AB ? Last edited by tranceanddance; 20th January 2013 at 04:24 PM.
diyAudio Member

Join Date: Aug 2012
Location: pasuruan
Quote:
 Originally Posted by Riff with bridge mode 8r load is min impedance for safety with B500. or go to 3ef and you can bridge mode with 4r load. regards...
how if 500 standard given 2 Ohm load, is there a need to change the value of its components?
thanks

 21st January 2013, 09:11 AM #2410 tranceanddance   diyAudio Member     Join Date: Jan 2013 for PSU spec 55vac 25A they count(where I order transformer) for me 2500Wt transformer! how it can be?!!! ((

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