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Hi-end DSP based multi-channel integrated Preamp/Crossover/DAC project
Hi-end DSP based multi-channel integrated Preamp/Crossover/DAC project
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Old 20th July 2018, 09:37 PM   #1111
pos is offline pos  Europe
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For perspective, here is how Benchmark handles this common noise phenomenon in the DAC3 (ES9028PRO) : Review and Measurements of Benchmark DAC3 | Page 16 | Audio Science Review (ASR) Forum
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Old 21st July 2018, 01:30 AM   #1112
Tranquility Bass is offline Tranquility Bass  Australia
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Hi-end DSP based multi-channel integrated Preamp/Crossover/DAC project
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Originally Posted by pos View Post
For perspective, here is how Benchmark handles this common noise phenomenon in the DAC3 (ES9028PRO) : Review and Measurements of Benchmark DAC3 | Page 16 | Audio Science Review (ASR) Forum
Yes well spotted article I have already implemented the IV converter using diff opamps in the next revision some months ago in preparation for the change from the ES9028PRO to the ES9038PRO chip. Probably go for 0.1% metal film resistors in the IV converter if I can get them. However this won't fix the pin 1 problems I have been having with this other amp I have been dealing with but not much I can do about that. That is completely out of my control unfortunately

Just some more measurements on it. It appears the CM DAC noise is about 30dB higher than the DM noise or background level of the sound card and rolls off at higher frequencies so is predominately audible and not RF like originally thought. Measured with an Agilent 6.5 digit DMM I get about 0.2mv RMS. Top trace is the CM noise spectrum. Bottom trace is the balanced noise or sound card background noise spectrum.

It appears that some balanced inputs on amps and other equipment just aren't up to the task of handling the CM noise from the DAC. I have had excellent results with some amps including a CARY valve amp which must have used a transformer in its balanced input because the noise was totally absent even right up to the throat of the horn. Same deal with a Valvet solid state power amp. No noise coming from an ion plasma horn tweeter ! However a Vitus power amp driving woofers was a different story. It's as though the balanced input was implemented by taking the signal from pin 2 and 1 instead of from pin's 2 and 3 of the XLR connector !! This one was an epic fail on its balanced inputs. It's a good test though

cheers
david

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Last edited by Tranquility Bass; 21st July 2018 at 01:36 AM.
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Old 21st July 2018, 02:01 AM   #1113
dch53 is offline dch53  Australia
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Default New ES9038PRO board

Hi David,

Will I be able to retrofit the new ES9038PRO board to the unit I purchased 9 months ago?

Or do the changes go deeper? I see it has different power supply requirements.

Thanks, Dave.
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Old 21st July 2018, 02:09 AM   #1114
Tranquility Bass is offline Tranquility Bass  Australia
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Hi-end DSP based multi-channel integrated Preamp/Crossover/DAC project
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Hi David,

Will I be able to retrofit the new ES9038PRO board to the unit I purchased 9 months ago?

Or do the changes go deeper? I see it has different power supply requirements.

Thanks, Dave.
The new board will be a drop in replacement to the existing board except for the higher power requirements. I will see what the current requirements are once I have the new board running otherwise everything else should work ok. I have already beefed up the power supply with a 50VA transformer to replace the pcb mounted 30VA one but it may be ok with the existing power supply.

cheers
david
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