2x 500w amplifier

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#3
the spec thingy says 700watt RMS into 4ohm. theres 8 chips on the heatsink. the two on the far sides are identical and the 4 in the middle are identical. The datasheet says 200 watt for the 2SA1494. Im guessing from the looks of it that this thing is push pull.
The power supply specs says +/- 70. thats 140 volts difference. If you calculate the watts thats 1120 per rail or 2240 watts total @ 16 amps.

So in my conclusion yes the power output is very possible because at 700 watts its running at 87% of its max capability. But if its drawing the 16 amps in class A its only 62% efficient. But keep in mind thats RMS not peak and thats per channel if it was designed right. Your gonna need ALOT of speakers, or very large enneficient car subs OR an ESL to use this. also this thing is gonna need a heatsink several several times larger than the board (probably the size of a cinder block)
 
#5
Woa...what a surprise

The schematics are actually posted on the auctions. Have seen all these designs before and any one of these boards wound save a DIYer a lot of time and trouble. It is far easier to modify than to build from scratch!

What someone said about heat sinks is true. If free air cooled pretty much figure at least 1 square inch per watt of power. That is a big heat sink!

Looks pretty good to me really.
 
#7
from the looks of it it is bridged. 4 400 watt push pull amps bridged together per channel.
The only reason i specced the rail voltage is because it gave the amperage. watts = volts x amps. this means your kenwood should only be pulling 1.8 amps if thats 125 per channel rms

speaking of which if you do buy this good im wishing you good luck on finding the 140v ct transformer with 16 amp secondaries
 
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#8
I wouldn"t buy a BGR Kit EVER again , Total rip off , First I ordered a Kit but it came Pre built , Then the Schematic that comes with it isn"t even the circuit used on the Board , The schematic comes with a Partial Datasheet of the Mosfet output Transistors That has been Altered so it looks like the Mosfets are for audio when they are High voltage switching Transistors ......

Then to top it off I connect it to a Power supply and it doesn"t work ......
 
#10
From the schematic and rail voltages I would assume this might make 200 watts into 8 ohms without distortion. A lot of cheap amps rate their power at 10% distortion so it is feasible that it might do 250 watts/channel. A lot of cheap amps also rate power by total watts divided by channels. It is a deception but in honesty, 500w out of two channels is possible. I would not expect the output devices to survive sine wave loading into four ohms for very long, should be twice as many to handle that load.

Figure a 10 volt drop from rail to output: 70 - 10 = 60. Making sine wave would take that number times .707 to get 42.42 volts rms. 42 X 42 = 1764. To get the wattage: 1764/8 = 220.5. That is assuming you have a very stiff power supply.
 
#11
thank you gearheaddruid. I was about to post the same. referring back to my old/new kenwood the rails are +/- 68. The published rating is 125 watts rms @8 ohms worst case is .03%thd 20-20khz both channels driven. A single channel will clip at around 175 watts. The ebay ad is generous in its statement. Here is another great ebay amp

NEW GEM SOUND 3000watt PRO DJ AUDIO AMPLIFIER POWER AMP on eBay.ca (item 380209762793 end time 25-Mar-10 23:52:33 EDT)

3000watts or is it 1400 watts or is it 1000 watts or what watt is it.

from the add
Brand New Gem Sound EXA-3955

Shake the Room! The Gem Sound EXA-3955 produces a booming 1400 Watts Peak of earth-shattering sound!

"Gem Sound has introduced the latest in the range of audio amplifiers customized for DJs and musicians. The Gem Sound EXA-3955 Stereo Power Amplifier can boost sound levels up to 1000Watts Peak Power".

from a DJ equipment supplier GEM 3950

# 1400 watts RMS @ 4 ohm bridge mono
# 700 watts per channel RMS@ 4ohm
# 350 watts per channel RMS @ 8 ohm

350 @ 8 ohms is nothing to sneeze about, but it is a far cry from 3000

ah the truth in advertising
 
#14
multisync said:
# 1400 watts RMS @ 4 ohm bridge mono
# 700 watts per channel RMS@ 4ohm
# 350 watts per channel RMS @ 8 ohm

350 @ 8 ohms is nothing to sneeze about, but it is a far cry from 3000
Click to expand...

A-choo! I wouldn't believe those ratings either - it looks like a CE1000 clone, which is a cheap amp to begin with. 475W per channel into 2 ohms. Spend $100 more and at least get a Behringer.
 
#16
what everyone has missed is that the ad says MAX of 500w 8 ohms. this is the old car stereo trick of over rating the power. this amp is no more then a 200-250w at 8 ohm amp. with a maximum of 500w either peak or at some ungodly distortion figure etc. some companies these days will say xxxRMS, xxxPeak, xxxMusic Power! which is the same type of **!

I would say 200w is probably a safe figure with the right heatsinks and PSU etc etc etc the moon is blue etc.
 
#18
this is an sziklai amplifier so eficiency is between 55-60% so it is expected to produce as is arround 200 W at 8 ohms load but in for ohms with only 2sets of outs per board its kinda risky

then again there is no protection in the outputs and belive me at this power is necessery

so for a lo fi application with a good power supply and 8 ohm speakers it will rock

all the above given as afact that outputs are bearly decent
 
#20
500 watts versus 250 watts

You know 500 watts is only 3dB more than 250 watts and 250 watts is whole lot easier to come by. 350 watts is not at all uncommon for a bridged 120 watt per channel stereo amp (bridging makes a 120 watt stereo a 350 into 8 ohms mono) which is only 1.5dB less than 500 watts and is available widely.

Would you consider a little less power for something far easier to get?
 
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