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Old 28th September 2005, 11:04 AM   #1
gongken is offline gongken  Sweden
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Default PWM amplifier hooked onto a tube preamp


Im about to build myself a guitaramp. The philosophy is to use a tube preamp (for good distortion) and hook a Class-d power amp onto that, say for an example an UcD-180...

The preamp schematic looks someting like this

Click the image to open in full size.

How would a class-d amplifier reakt to being hooked onto a preamp like this?

What about the output impedance of the preamp, how would it interact with a PWM amp???

Any general tips or hints on the schematic?

Im not really good at this so i'm thankful for all support, and I
would humbly ask ypu to keep a modest technical level of your answears so I can understand you folks

This topic can also be found in the "Class-D" section.

Kind regards

A white Volvo turns into the Ringroad
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Old 28th September 2005, 11:16 AM   #2
EC8010 is offline EC8010  United Kingdom
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I think you will need a cathode follower added to the output in order to drive the low input impedance of a solid state amplifier. The input of a switching ampliier is almost certainly an op-amp, but it will probably have quite a low value shunt resistor (10k is likely). Some Tripath switching amplifiers are configured to be inverting amplifiers and are supplied 49.9k input resistance.
The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...
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Old 28th September 2005, 02:25 PM   #3
gongken is offline gongken  Sweden
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Join Date: Jul 2005
Location: Southern Sweden
So, I've herad that it's possible to build a little input buffer for the PWM with an OP-amp to ensure that the output impedance is kept low of the tube preamp. I've seen an article i think, but i can't remember where...

Can anyone please make a drawing of such a schematic??

Kind regards

A white Volvo turns into the Ringroad
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