Transistor/opamp circuit

soundNERD · 5th September 2004, 01:18 PM

With this circuit, http://www.mif.pg.gda.pl/homepages/t...s/simp200W.gif

which of these transistors would be best, if any?
http://www.centralsemi.com/Selection...TO_220Case.pdf

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?

carlmart · 5th September 2004, 01:47 PM

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

soundNERD · 5th September 2004, 02:10 PM

so this schematic is not a good idea?

soundNERD · 5th September 2004, 02:20 PM

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)

johnnyx · 5th September 2004, 02:36 PM

This circuit is being discussed in the "complementary output transistors in chip amp" thread.
This thread

djk · 6th September 2004, 05:30 AM

The 3875 with the 15003/04 running off a single 75V supply (±37) can do 400W into 4 ohms for a sub amp.

soundNERD · 6th September 2004, 05:16 PM

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?

carlmart · 6th September 2004, 08:32 PM

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

soundNERD · 7th September 2004, 12:54 AM

That circuit is bridged, 2 boosted 3875 in bridge

soundNERD · 8th September 2004, 02:11 AM

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?

5th September 2004, 01:18 PM	#1
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	Transistor/opamp circuit With this circuit, http://www.mif.pg.gda.pl/homepages/t...s/simp200W.gif which of these transistors would be best, if any? http://www.centralsemi.com/Selection...TO_220Case.pdf 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?

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5th September 2004, 02:10 PM	#3
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	so this schematic is not a good idea?

5th September 2004, 02:20 PM	#4
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	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)

5th September 2004, 02:36 PM	#5
johnnyx diyAudio Member Join Date: Jan 2004 Location: manchester	This circuit is being discussed in the "complementary output transistors in chip amp" thread. This thread

6th September 2004, 05:30 AM	#6
djk diyAudio Member Join Date: Feb 2001 Location: USA	The 3875 with the 15003/04 running off a single 75V supply (±37) can do 400W into 4 ohms for a sub amp.

6th September 2004, 05:16 PM	#7
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	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?

7th September 2004, 12:54 AM	#9
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	That circuit is bridged, 2 boosted 3875 in bridge

8th September 2004, 02:11 AM	#10
soundNERD diyAudio Member Join Date: Sep 2003 Location: Illinois	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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