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Old 6th October 2002, 06:44 PM   #1
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Default SuperFlea 100+W

I'm tinkering with this circuit. It simulates well, but I can say from experience this doesn't mean it will work at all once it is breadboarded. Gain is low, and I thought about using a bootstrap arrangement on the input, but decided to try it without to start. Your thoughts are much appreciated as always.

Mike
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Old 6th October 2002, 08:00 PM   #2
eLarson is offline eLarson  United States
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A couple of scattered thoughts:

The coupling between the two halves of the amplifier reminds of Figure 3 from US Patent #5,376,899.

I wouldn't think the input impedance would be too difficult to drive.

The thing that would make me most nervous is the nagging fear that one half of the amplifier might fail, leaving a considerable DC voltage at only one of the loudspeaker terminals.

I'd definitely be interested in hearing how it sounds in testing! (I've been contemplating building something like this for the last week or two, but it is financially unfeasible for me to have a go at it right now. *d'oh!* )

Erik
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Old 6th October 2002, 08:25 PM   #3
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Thank you, Erik

The voltage problem is definitely a nagging one. It's tempting to use output caps, but I wonder if there might be some other way to protect it.

I may build a smaller version first with a lower supply voltage, although simulations indicate that it performs much, much better with the higher rail.

Incidentally, the output FETs are supposed to be 240 and 9240 I made a mistake in the drawing.

I let you know if it actually works.

Mike
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Old 7th October 2002, 03:38 AM   #4
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With some feedback, it would be much the same thing.

People worry too much about DC on failed balanced
amps, which is not much more likely than non-balanced
amps.

I haven't lost a speaker to DC in 15 years, and it still
wasn't the amp's fault.

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Old 7th October 2002, 12:19 PM   #5
eLarson is offline eLarson  United States
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NP wrote:
Quote:
People worry too much about DC on failed balanced amps, which is not much more likely than non-balanced amps.
I haven't built any power amps yet, only little line amps. Those have all turned out okay, even being powered up continuously for just over a year. (It is a "Bride of Zen" with a slightly altered power supply.)

Still, I may go down to Radio Shack to find a pair of expendable speakers to break-in my amps with... just in case.

Erik
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Old 7th October 2002, 04:53 PM   #6
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Thanks NP and Erik!

That's good news about the DC.

I was deliberately trying to stay out of "X" territory because there are already a couple of really good threads (AlephX and XSOZ) addressing this topic. I mostly wanted to see if a high powered AB circuit will do alright without the overall feedback.

This is definitely a layperson's design, as I'm mostly self-taught (meaning I have fool for an instructor) I just keep trying different things and maybe one of these times I'll come up with a worthy project. I've had many failures, but I just observe reasonable electrical safety, and go for it. For me, experimenting is where most of the fun is. And when I've abondoned all hope on a design, I can always go listen to my Zens. (thanks Nelson)
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