what is the output stage class for Dynacord L2400 - diyAudio
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Old 11th June 2014, 07:24 PM   #1
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Default what is the output stage class for Dynacord L2400

Dynacord L2400 output board schematic

I have seen the above amp performing and its just breath taking superb in dynamics and very effortless driving 4 x 18 inch B&C subwoofers per channel and they were literally shaking the walls of the buildings on a live event.

I was just checking the schematics of the above amp that what class is it or what really made that amp to do that job. I have seen labgruppen, crown but none of them came close to such an extreme effortless dynamic sound. sledge hammer tight and absolutely no stint.

Just gone through the schematic and found shocking that there are about 9 x 2200/160V psu caps ( gone mad after seeing this )

saw another thing that the rails are at +/-68V and got shocked again..

how come something could deliver that performance with just such low voltage? is the amp bridged?

just want to know which class is this amplifier? and how come it could deliver such a tremendous dynamics with just less than 20000uf caps?
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Old 11th June 2014, 07:38 PM   #2
llwhtt is offline llwhtt  United States
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I don't know what schematic you were looking at but the one you refer to has 136VDC rails hence the 160VDC capacitors in the supply. But if you notice the PS for the output stage is floating, why would that be? And why does each channel appear to have two output sections? Why is one of the output sections grounded? Go do some research at the Crown site for the answers. I think you'll find it interesting if you can understand it. They call it Grounded Bridge.

Craig

To speed things up download the Crown Power Base 1 service manual and read the theory.

Last edited by llwhtt; 11th June 2014 at 07:53 PM.
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Old 11th June 2014, 07:42 PM   #3
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I was looking at this schematic.. http://www.diyaudio.com/forums/attac...tic-84157e.pdf

is it grounded bridged amplifier?
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Old 11th June 2014, 07:55 PM   #4
llwhtt is offline llwhtt  United States
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That's what Crown calls it.

Craig
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Old 11th June 2014, 08:07 PM   #5
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well I read that its patented? so how come Dynacord using it?
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Old 11th June 2014, 08:42 PM   #6
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Looks like it kinda runs BTL with a floating supply. Not sure how exactly that setup works (one half of the amp would seem to be pulling the floating pair of supplies up and down), but if the schematic says the thing can do 69.3 V into 4 ohms (which is 1200 watts) I'll believe that. The circuit gives the impression of having been competently designed.

9x 2200 F / 160 V might seem modest to you but
a) PA amps generally aren't designed with as much dynamic headroom to begin with and
b) it's not as little as you think if you look at things from an energy storage perspective.
These 9 2200 F caps at ~140 V store as much energy as 2x9 2200 F caps on ~100 V, so they're about the equivalent of 2x 20000 F with +/- 100 V supplies.

I'm not exactly sure why they chose this supply setup, but my hunch is that this one allows the outputs to be run in BTL while still being friendlier in terms of SOA compared to a +/- 100V supply.

Oh, and this looks like your average AB class amplifier, though fully balanced.

EDIT: Looks like I was a little too slow... Anyway...
Quote:
Originally Posted by rhythmsandy View Post
well I read that its patented? so how come Dynacord using it?
Licensed? Patent's run out?

Last edited by sgrossklass; 11th June 2014 at 08:44 PM.
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Old 11th June 2014, 09:04 PM   #7
llwhtt is offline llwhtt  United States
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sgrossklass you are correct, the left side of that schematic pulls either side of the power supply towards ground depending on the signal. A positive signal would pull the negative side towards ground and vice versa. Seems overly complicated to me but what do I know?

Craig
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Old 12th June 2014, 06:41 PM   #8
C3PO is offline C3PO  Philippines
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This is a grounded bridge amplifier, same circuit with Electro-Voice P3000.
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Old 13th June 2014, 03:16 AM   #9
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can we do ground bridge with lme49810s? if so what is the inverter circuit to be used the one which flips the input signal to operate in grounded bridge operation? an inverting opamp?
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Old 16th June 2014, 04:24 PM   #10
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can we use a just an inverting opamp for the signal inversion?
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