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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Simple High Performance DC Coupled Class A HPA with sub PPM THD
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Old 19th June 2018, 10:32 PM   #61
vvs07 is offline vvs07  United States
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
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Old 20th June 2018, 03:41 AM   #62
xrk971 is online now xrk971  United States
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Quote:
Originally Posted by stellarelephant View Post
Cool PSU... Out of curiosity, does it sound any different to you compared with the torroid?
I could hear a tiny bit of 60Hz hum when using linear supply on more sensitive headphones. There is no audible hum with the new DC-DC PSU. Also, turn-on transient thumps are completely eliminated with the new PSU as cap multipliers have about 20 second long time period to get up to full voltage. With music playing there is no discernable difference with dynamics as that is all based on bias current in SE Class A design.
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Old 20th June 2018, 07:33 AM   #63
Morde is offline Morde  Finland
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
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Old 21st June 2018, 05:12 PM   #64
sarathssca is offline sarathssca  India
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Originally Posted by Morde View Post
Badboygolf16v - 1 pair
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funch - 1 pair
kartk - 1 pair
Yourownbuzz - 1 pair
BabyDontHertzMe - 1 pair
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passive420 - 1 pair
Pinnocchio - 1 pair
vvs7 - 2 pairs
Gwrskien - 1 pair
Ernesternest - 1 pair
jwjarch - 1 pair
ermine22 - 2 pairs
Morde - 1 pair
I think my name got added by mistake, removed it for now...
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Old 21st June 2018, 05:17 PM   #65
silasmellor is offline silasmellor  Denmark
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
What are you planning with the psu? Can that be fed off a trafo/diode bridge instead of an alps?
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Old 21st June 2018, 06:26 PM   #66
s610adam is offline s610adam  United States
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Old 22nd June 2018, 02:12 AM   #67
xrk971 is online now xrk971  United States
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Quote:
Originally Posted by silasmellor View Post
What are you planning with the psu? Can that be fed off a trafo/diode bridge instead of an alps?
The input for the on-board PSU is 8v to 18v, so a
Ideally a 12vdc Class 2 wall transformer (like those for old routers), or a 12v smps work fine. If you want to use a trafo and diode bridge and a few caps to generate your 12v thatís fine. One of the main goals was to get away from mains AC levels for safety.
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Old 24th June 2018, 10:25 PM   #68
stellarelephant is offline stellarelephant  United States
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Quote:
Originally Posted by xrk971 View Post
The input for the on-board PSU is 8v to 18v, so a
Ideally a 12vdc Class 2 wall transformer (like those for old routers), or a 12v smps work fine. If you want to use a trafo and diode bridge and a few caps to generate your 12v that’s fine. One of the main goals was to get away from mains AC levels for safety.
One option: DDU120100H4480: Jameco Reliapro : AC to DC Power Supply Wall Adapter Transformer Single Output 12 Volt 1 Amp 12 Watt : Power Supplies & Wall Adapters

I'm using this 12V 1A Jameco Reliapro linear wall wart, along with three(!) of the 5V version, to separately power each board in my RPi DAC setup. Mine were modified by member Greg Stewart, so I haven't heard them stock, but at least in modified form, they absolutely walk all over the much pricier iFi iPower for noise performance and natural sound. I'm sold on Class 2 vs. SMPS now.

From what I understand, Greg's mods include an AC filter cap (that works as the final C in a CLC filter that has a CL between the wall and the power strip), as well as upgraded diodes and some DC caps. I know he is working on providing a mod tutorial but not sure when that'll be posted.

Anyway, for $15, I reckon its a good candidate, even in stock form.
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Old 26th June 2018, 05:15 AM   #69
xrk971 is online now xrk971  United States
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Simple High Performance DC Coupled Class A HPA with sub PPM THD
Default Some Measurements with DC-DC PSU

I think we can see that the new DC-DC PSU is working very well with the data here. It is almost like a battery in terms of a flat noise floor. A DC-coupled amp has a slight rise as frequency goes down to sub-audio (rumble range). But clearly, there is no 60Hz mains or any of its harmonics present.

This is my usual standard of 1Vpp into 47ohms FFT for intercomparison with my other amps. The level of third harmonic distortion is 10x less than second harmonic, which is very nice. This amp will have a clean and engaging natural sound to it. Data below is for 142mA bias made possible using 2.2R source resistors.

1.02Vpp into 47ohms:
Simple High Performance DC Coupled Class A HPA with sub PPM THD-tims-hps-dc-dc-psu-142ma-1-02vpp-47r-fft-2-png

4.0Vpp into 47ohms:
Simple High Performance DC Coupled Class A HPA with sub PPM THD-tims-hps-dc-dc-psu-142ma-4-11vpp-47r-fft-png

I think the higher distortions I am seeing may be result of thick film SMT resistors being used. I will need to order metal thin film equivalents.
Attached Images
File Type: png TimS-HPS-DC-DC-PSU-142mA-1.02Vpp-47R-FFT-2.png (71.4 KB, 2967 views)
File Type: png TimS-HPS-DC-DC-PSU-142mA-4.11Vpp-47R-FFT.png (73.7 KB, 266 views)
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Old 27th June 2018, 12:58 AM   #70
stellarelephant is offline stellarelephant  United States
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Wow, X, looks like you nailed it!
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