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Re: National Semiconductor Amp Modules [message #10207 is a reply to message #10206]

Tue, 21 September 2004 19:29

Manualblock
Messages: 4973
Registered: May 2009

Illuminati (13th Degree)

Right now mine is playing on a pair of Altec 421 woofers and 811 horns/806 drivers. It sounds pretty darn good actually. Drives them with very little heat on the heatsinks so I geuss they are not being overdriven. I have Brian GT's extra special kit that I will put together soon and see if there is a difference. I get nice full and deep bass outa them on the Altecs. J.R.

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Re: National Semiconductor Amp Modules [message #10208 is a reply to message #10206]

Tue, 21 September 2004 21:19

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

I agree about the regulation. The supply for a powerful amp should have adequate current capacity and should be regulated so that the voltage rails don't fluctuate with changes in current demand.

I understand how some tube amp enthusiasts like using a simple unregulated circuit, but I think this is more for simplicity's sake than anything else. If there is not much of a current demand, then that's sufficient. Small power tube amps are that way.

But high power needs higher current, and the swings can really rob a power supply. So in this case, I think a good, high-current regulated supply is important. You could even do something like using motorcycle batteries or small sealed lead-acid batteries for improved transient current capacity.

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Re: National Semiconductor Amp Modules [message #10308 is a reply to message #10208]

Wed, 13 April 2005 11:18

Chris R.
Messages: 82
Registered: May 2009

Viscount

Wayne,

About supply regulation on these chip amps...
The one I built uses two 12KuF (or maybe 15KuF) caps very close
to the chip itself. Using a scope, I can watch the PS droop.
At the point the amp starts clipping, I'm getting only a small
amount of droop. I could go measure it again if anyone cares.

Adding a ~4A regulator would significantly complicate the design and make the project less attractive.
One thing I noticed that was interesting was that in at least
one of my HT receivers, the PS caps were about the same size I'm
using for a single amp. The accountants got to that desing.

About the previous comment about bigger caps coloring the sound, I
can't imagine how that would work. I can understand how undersized
caps could cause problems, though.

Chris

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Re: National Semiconductor Amp Modules [message #10309 is a reply to message #10308]

Wed, 13 April 2005 12:35

Wayne Parham
Messages: 18792
Registered: January 2001

Illuminati (33rd Degree)

That's some serious capacitance. I'll bet the amp stays running for several minutes without AC power input. I don't know who might have felt the smp sounded better with less capacitance either, but maybe if they were using big 'ol electrolytics that were real lossy or something, maybe they didn't work so well. Sometimes, the real problem is rectifier switching artifacts anyway, and a few small value caps across the diodes work wonders for that. But as far as transient ability and ripple reduction are concerned, high capacitance energy storage is king.

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