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Class D Switching Power Amplifiers and Power D/A conversion

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Old 25th August 2011, 04:33 AM   #31
fb is offline fb  Australia
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Saturnus,

Thanks for your explanation. Perhaps my choice of the word 'different' was not good.

Unfortunately, when using compression drivers nearfield (~1.5m in my case), it really is important to get low noise amps. The Panasonic class D receiver I have been using is too noisy.

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Old 25th August 2011, 05:02 AM   #32
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Anybody know what the PSRR of the L20D is?
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Old 25th August 2011, 05:50 AM   #33
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Quote:
Originally Posted by fb View Post
Saturnus,

Thanks for your explanation. Perhaps my choice of the word 'different' was not good.

Unfortunately, when using compression drivers nearfield (~1.5m in my case), it really is important to get low noise amps. The Panasonic class D receiver I have been using is too noisy.
And trevmar's explanation will strongly suggest there will be no noise at your listening position. He said he had to move the speakers closer than 5cm from his ear to hear anything at all. 5cm for his speakers equals 1.5m for your speakers.
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Old 25th August 2011, 11:36 AM   #34
trevmar is offline trevmar  United States
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The Panasonic class D receiver I have been using is too noisy
Usually the preamplifier chain determines the overall noise level of a receiver. If the preamplifier is all-digital, then the preamplifier noise contribution drops to very low levels. That is why I chose to use a Mini-DSP for my "tone-controls" and digital volume control (the MiniDSP has a DC Potentiometer / ADC to set the output level). It is somewhat weird to be able to set up precise tonal compensation via my netbook, but it is also very effective. I don't have to do it very often, as flat sources and flat speakers mean most material sounds excellent without any shaping... If you use optical audio distribution (SPDIF) then you can buy digital switches to select among multiple inputs. I have been using an HDMI switch with SPDIF output, but am now switching to one with analog outputs (which handles AC3-WAV conversion internally).

ps: This is the switcher I use, it has both Toslink SPDIF and Analog outputs:
4X1 HDMI 1.3b Certified Switcher w/ Toslink & Digital Coaxial Port (Rev.2) w/ 3D support.
I use this device to convert my old DVD player to HDMI:
Component (YPbPr) & S/PDIF Digital Coax/Optical Toslink Audio to HDMI Converter
.

Last edited by trevmar; 25th August 2011 at 11:45 AM. Reason: updated link
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Old 26th August 2011, 11:32 AM   #35
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Default Pinout

Hello!, I'm sorry to use this tread but I don't know how to connect my new L20D ... The pinout on ebay page was not very clear... +70V to VCC+; -70V to VEE- and ground to PGND? The speaker + to OUT+ and speaker - to PGND?
Thank you a lot
max
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Old 26th August 2011, 04:25 PM   #36
trevmar is offline trevmar  United States
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Desibros,
I don't know what you read on the Ebay page, I always work out the connections by looking at the circuit board, and seeing where the contacts go. Looking from the top of the board, the order of pins the header block, from the end where is printed the "Voltage DC +-70V Output Power 250W 8R" is -V, Ground (zero for power supply and one side of speaker), Speaker active side, and +V

I hope that helps. If in doubt, you can check where the + and - go to the main bypass capacitors...
.
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Old 28th August 2011, 01:17 PM   #37
gychang is offline gychang  United States
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trevmar thanks for your efforts, following this with interest.
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Good sound from Davis, CA
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Old 28th August 2011, 06:32 PM   #38
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Originally Posted by trevmar View Post
Desibros,
I don't know what you read on the Ebay page, I always work out the connections by looking at the circuit board, and seeing where the contacts go. Looking from the top of the board, the order of pins the header block, from the end where is printed the "Voltage DC +-70V Output Power 250W 8R" is -V, Ground (zero for power supply and one side of speaker), Speaker active side, and +V

I hope that helps. If in doubt, you can check where the + and - go to the main bypass capacitors...
.
Hello! thank you a lot the suggest was usefull!
Bye!!
max
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Old 6th September 2011, 11:36 PM   #39
alkasar is offline alkasar  France
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very interesting measures Trevmar

May I suggest you mention who's who on the graphs. I was very confused at firts to figure out which measure is for which amp
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Old 7th September 2011, 01:00 AM   #40
Bernie7 is offline Bernie7  Singapore
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Originally Posted by alkasar View Post
very interesting measures Trevmar

May I suggest you mention who's who on the graphs. I was very confused at firts to figure out which measure is for which amp
If you let the mouse pointer hover over each image for a sec, the title appears. But yeah, it can be easier to read.
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