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Class D Switching Power Amplifiers and Power D/A conversion

Class D and Very Low Impedance loads
Class D and Very Low Impedance loads
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Old 3rd August 2005, 08:38 AM   #31
Pafi is offline Pafi  Hungary
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Originally posted by Kenshin
too big MOSFETs
Yes, they are big for 2*3W, but too small for 50W@0.1ohm. This is just a sample, these tranzies were in my drawer, parts should be replaced.

but the power output is only a few watts.
Up to 240W, but current capability and efficiency are still too low for 0.1 ohm load.
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Old 22nd March 2015, 02:02 PM   #32
tiefbassuebertr is offline tiefbassuebertr  Germany
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Originally Posted by LineSource View Post
I'm excited to see so much activity and hope to see some sample schematics and Spice simulations soon.

The ribbon is 100 db/watt efficient, but at 0.1 ohms, we still need 10 amps to reach 1 watt. I design my speakers for 110 db @ 1m max SPL, as I do most of my listening below 80 db @1m, about 74db at the couch. This is the magic of high efficiency ribbon linesources, you can get goosebump audio at kid safe SPLs.

My current amp is a DIY Class-A that uses a SuperSym folded cascode topology to drive 16 Sanken 180 watt bipolar output transistors. The output stage is a bridge with 4 NPN-PNP pairs on each symmetrical side. I am currently using a +/- 7V power supply for the output stage and +/- 12V for the driver circuits.

I am looking forward to a fully digital signal path: digital outs from the DVD/CD player, going over digital cables to each speaker where there is a digital Xover with room equalization and YOUR DIGITAL AMP.
Are there any news in this matter?

Last edited by tiefbassuebertr; 22nd March 2015 at 02:06 PM.
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Old 22nd March 2015, 06:37 PM   #33
bcarso is offline bcarso  United States
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Going on ten years now! Oh well these things take time, especially when the fully digital signal path has been under fire as more marketing than real improvement. I think this was the first thread I looked at on this site lo those many years ago.
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Old 23rd March 2015, 02:15 AM   #34
soongsc is offline soongsc  Taiwan
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I think it is a nobel goal to try and keep digital music digital throughout the system. Generally it should be a lot easier to control all the interface between equipment. Although, having heard a report from a friend that even optical cables can alter the sound, the signal interface. buffering, and timing probably needs a more thorough investigation.
Hear the real thing!
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Old 23rd March 2015, 02:39 AM   #35
bcarso is offline bcarso  United States
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Yes, it is a myth that digital transmission is perfect and immune to interference.
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Old 23rd March 2015, 03:12 AM   #36
abraxalito is online now abraxalito  United Kingdom
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Looks like getting low enough self-noise on the power supply for satisfying subjective dynamics is going to be the biggest challenge here. Building on Bruno's earlier calculations for the capacitor size (around 0.5F) the ESR needs to scale down too alongside the capacitance scale-up. Given a typical pair of reservoir caps might have 10-20mohms ESR the 0.5F cap should have ESR below 0.5mohm. This level of ESR is achieved with some of the larger Maxwell ultracaps however the large capacitance needed to achieve this (into 1000s of Farads) is inconvenient in terms of switch-on time.

I think using an output trafo is a more practical option.
'The total potential here must be nothing less than astronomical.'
'Nothing less. The number 10 raised almost literally to the power of infinity.'
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