| carlmart |
| quote: | Originally posted by soundNERD
I plan to use this with an 3875. Does anybody know about how much RMS and peak power can be delivered to an 8ohm speaker? |
IMHO using any power amp chip as a stage for a transistor based output is not too smart. Except if you already have the parts.
It's much better to use a good wide-bandwidth chip on first stage and go from there.
Carlos |
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| soundNERD |
| so this schematic is not a good idea? |
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| soundNERD |
Well, I do have mj15003 and MJ15004 transistors, but they are TO-3 and are hard to mount on a heatsink. I coul get samples of the chips in that pdf file also, and they are to-220
forogt to mention, this is a subamp, so power is more important than clarity and sound quality (except I do want a good sounding amp for bass) |
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| johnnyx |
This circuit is being discussed in the "complementary output transistors in chip amp" thread.
This thread |
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| djk |
| The 3875 with the 15003/04 running off a single 75V supply (±37) can do 400W into 4 ohms for a sub amp. |
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| soundNERD |
:bigeyes: :bigeyes: 400 peak? or 400RMS?
Either way, wow... i think i found my amp...
Plus my supply is close to that, +-/34 so I might even be close to that amount of power!
Since it would be getting so much power out of that circuit, would any of the components need to be more powerful? especially the diodes? |
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| carlmart |
| quote: | Originally posted by djk
The 3875 with the 15003/04 running off a single 75V supply (±37) can do 400W into 4 ohms for a sub amp. |
I think there might be something wrong with those figures, as you can't get 400w in 4 ohms with just +/-37v on your supply. Only in bridged mode.
Where did you get those numbers?
Carlos |
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| soundNERD |
| That circuit is bridged, 2 boosted 3875 in bridge |
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| soundNERD |
Has anybody used this amp and would recomend me use the 3875 and mj15003/4 for my subamp? Are those transistors good for this? I have them sitting around.
Also, any comments on this design just using the 2030? |
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| soundNERD |
Can somebody at least tell me how well they think that this amp will perform with a 3875, mj15003/4 transistors, +/-30VDC supply, and an 8ohm 12" sub (sealed box)?
And, I still want to know, 400W RMS or Peak? |
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| djk |
"And, I still want to know, 400W RMS or Peak?"
Maybe you should learn something about your hobby.
400W avereage power, what the great unwashed refer to as 'watts RMS', is 40V RMS across 4 ohms. That would be 56.56V peak.
The suggested supply was 75V.
The 75V is obtained from a 55V AC transformer, rectified and filtered under no load you will have about 75V, as you load the supply by driving the amplifier this voltage will drop.
The transformer should be about 800VA, the main filter cap about 6,800~10,000µF at 80~100V, the rectifier about 25A at 200V. |
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| soundNERD |
| When building this, would it be a bad thing if I use short wires to connect the transistors to the PCB? Its hard to connect both 2 to-220 devices and 4 to-3 devices to a heatsink if they are all soldered to a board. |
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