"Steampunk" DAC headAMP (agdr Audio Super CMoy + WesionTEK Khadas Tone Board)
Oct 21, 2018 at 10:55 AM Thread Starter Post #1 of 26

WoodyLuvr

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:robot::skull::scream: EDITED WITH ADDITIONAL BUILD UPGRADE INFORMATION & PICS :atom::radioactive::biohazard:


My USB-Powered "Steampunk" DAC headAMP build in three (3) parts...

BUILD; PART 1 (Case)
The case was constructed out of two (2) reclaimed/re-purposed wooden cigar boxes; a small sheet of Hardboard - High-Density Fiberboard (HDF); and copious amounts of wood glue. The case was then decorated with vintage postage stamps with decoupage glue... with well over fifty (50) thin layers of finely sanded decoupage varnish.


BUILD; PART 2 (USB-Powered HeadAMP)
I used agdr audio's OPA1688 Parallel (Dual Chip) "Super CMoy" head amp board and it is performing wonderfully! Many thanks to @adydula for assisting me in more ways than one with this build... very much appreciated good sir! The board has been upgraded from 2 X 9V battery operation to a USB-feed DC-DC Converter power supply.

The power module consists of a RECOM RW-0509D DC-DC Converter which converts the 5V (500mA; ~2.5W) from the USB 2.0 DIY power-only cable to the required 9V. USB 2 easily covers the converter's current requirement of ~167mA per rail (~334mA total) and when at max loading this converter is using less than 1.9W!

agdr Audio OPA1688 Parallel Super CMoy Specs
Output Impedance (ohms): ~0 Ω​
Voltage Gain: 1x ("unity-gain amplifier")​
Peak Voltage Swing: 7.4 V (aka Vp or Vdc)​
Peak Output Current: 150 mA per channel​
RMS Output Voltage: 5.23 Vrms​
RMS Output Current: 106.05 mA rms per channel​
Maximum Power (rms): 181 mW @ 16Ω (1.7 V)​
Maximum Power (rms): 360 mW @ 32Ω (3.4 V)​
Maximum Power (rms): 427 mW @ 64Ω (5.23 V)​
Maximum Power (rms): 228 mW @ 120Ω (5.23 V)​
Maximum Power (rms): 182 mW @ 150Ω (5.23 V)​
Maximum Power (rms): 91 mW @ 300Ω (5.23 V)​
Maximum Power (rms): 46 mW @ 600Ω (5.23 V)​

Without further ado, my creation (please kindly excuse the 'shotty' soldering and gluing... I battle severe hand tremors):

THE GUTS (INSIDE)
The copper tomb... no EMI/RFI getting in this here amp!
Ground wire point is at top right
Larger diameter cord grip/cable gland had to be used to allow for USB connector to pass through, as well as for future extra cables and upgrade capability.
Steampunk DAC HeadAMP_7.png


A Silica Gel Pack Has Been Taped On The Under-Side Of The Lid To Battle The Siamese Humidity. As you can see the copper under the lid is already quickly tarnishing.
Chicago Sex Screws (Female Bottoms) for the leather straps are seen on the underside of the lid.
Steampunk DAC HeadAMP_15.png


agdr Audio Super CMoy headAMP module
"OPA1688 Parallel Super CMoy dual-chip headphone amplifier with a real ground and a headphone relay for zero turn-on or turn-off thump and essentially zero (250uV) DC output offset voltage. Uses two (2) of the brand new Texas Instruments OPA1688 ( http://www.ti.com/product/OPA1688 ) headphone driver chips in parallel for 150mA output per channel (6x the output of most op-amps). Ultra low distortion with extremely low idle current for long battery life. Uses 2 9V batteries with a real ground and "solid state relay" technology - no virtual grounds or rail splitters to distort the sound." - agdr audio

The black colored hot glue messes you see are only to protect the power leads solder joints from my inept hands :wink:
Steampunk DAC HeadAMP_16.png


FACE (FRONT SIDE)[/B]
Brass Volume Knob (6mm Shaft Diameter X 19mm Knob Diameter); UPDATE: see most recent post in this thread; the knob has been replaced with a 1930s vintage tube radio knob.
Switchcraft 35RA 3.5mm Headphone Jack (Stereo TRS 3-Position Switched)
1840 Penny Black
1841 Two Pence Blue
1841 Penny Red
1853 Four Pence Cape of Good Hope
1901-1934 Federated Malay States (FMS) Tigers
1898 US Battleship Revenues (U.S.S. Maine); aka "Battles"

Steampunk DAC HeadAMP_1.png


BACK SIDE
Left: Hammond Cordgrip / Cable Gland 1427CG7 (2.54mm-6.6mm)
Right: WZOG Ouguan Electric Cordgrip / Cable Gland PG-11 (5mm-10mm)
US Internal Revenue RS114d John Henry Medicine
More "Battles" and "Tigers"...

Steampunk DAC HeadAMP_2.png


LEFT SIDE[/B]
Chicago Sex Screws (Male 6mm Tops; Female 6mm & 8mm Bottoms) with Raw Brown Leather Straps
1898 US Battleship Proprietary Revenue Set RB20-RB31 with a few First Tax Day Issue dates

Steampunk DAC HeadAMP_5.png


RIGHT SIDE[/B]
1898 US Battleship Documentary Revenue Set R161-R172 with a few First Tax Day Issue dates and late/post tax usage dates 2 May 1902

Steampunk DAC HeadAMP_4.png


TOPSIDE[/B]
Bronze Cigar Box Protective Corners
Chicago Sex Screws (Male 6mm Tops; Female 6mm & 8mm Bottoms) with Raw Brown Leather Straps
1936 Germany Zeppelin Airship LZ 129 Hindenburg First Mail Flight Cover

310px-Hindenburg_disaster.jpg

1934 Germany Death Of President Hindenburg; Complete Set (Black Mourning Border)
1936/1938 Germany Zeppelin & Lufthansa Air Post Stamps
1899 Russia Zemstvo Postal; Imperial Post (Moscow)

Steampunk DAC HeadAMP_6.png


UNDERSIDE (BOTTOM)
Bronze Cigar Box Protective Corners
Adhesive Rubber Silicon Feet
1914 US Cover Mailed Onboard SS (RMS) LUSITANIA 1914 (RMS Lusitania was a British ocean liner and briefly the world's largest passenger ship; she was sunk on 7 May 1915 by Imperial German Navy U-boat SM U-20)
Various Great War Propaganda Stamps
More "Battles"

Steampunk DAC HeadAMP_3.png


RECOM RW-0509D DC-DC CONVERTER POWER SUPPLY MODULE (PIC 1 & 2)
CTS Black Aluminum Heat Sink 40mm x 40mm x 9.5mm

Steampunk DAC HeadAMP_10.png

Steampunk DAC HeadAMP_9.png


RECOM RW-0509D DC-DC CONVERTER POWER SUPPLY MODULE (PIC 3)
Heat Sink Insulation & Grounding Pad
Steampunk DAC HeadAMP_8.png


BUILD; PART 3 (DAC)[/B]
For the DAC I used the new Khadas "Tone Board" by WesionTEK after reading the reviews and testing measurements on Audio Science Review (thanks @amirm !). Very detailed measurements are provided by Amir.

WesionTEK Khadas Hi-Res Audio Board (Generic Edition) Specs
XMOS: XU208-128-QF48 (8x Cores up to 500MIPS)​
DAC: ESS Sabre ES9038Q2M (32-Bit Stereo Audio)​
Output Impedance (ohms): ~100Ω​
RMS Output Voltage: ~2Vrms​
THD+N: ≤ 0.000337% @1KHz​
SNR: ≥ 120dB @ 10Hz~20KHz​
DNR: ≥ 120dB @ 10Hz~20KHz​
Crosstalk: ≥ 127dB @ 10Hz~20KHz​
Frequency Response: ±0.08 dB @ 10Hz~20KHz​
Sampling Frequency: PCM: Up to 768KHz @ 32bit; DSD: Up to DSD256 @ 1bit​
Clock Jitter: Reference Clock Jitter < 3ps; Data Clock Jitter < 30 ps​
Audio Formats: APE2/FLAC/OGG/WAV/ACC/ALAC/MP3/WMA…​
Line Out: 1x Red RCA for Right, 1x White RCA for Left​
S/PDIF IN: Up to 192KHz (S/PDIF OUT: Not Supported)
USB-C Port: Power Supply (DC: 5V/500mA) & USB 2.0 Data​
Compatibility: Windows PC; Linux PC; Mac OS X; Raspberry Pi​
Dimensions: 82.0 x 74.5 x 17.0 mm​

GENERIC EDITION TONE BOARD
Steampunk DAC HeadAMP_12.png

PCB - PERFBOARD MOUNTING w/ STANDOFFS
I super glued two (2) perfboards together and mounted the Tone Board to them.
Steampunk DAC HeadAMP_11.png


BOTTOM OF BOARD
Heat Sink Insulation & Grounding Pads before removing the adhesive backing strips to affix to bottom of case
Steampunk DAC HeadAMP_13.png


INTERCONNECT
ghentaudio B02 3.5 (⅛") TRS to RCA (+) Canare L-2B2AT Cable
Length: 10 cm; customized order.
Steampunk DAC HeadAMP_14.png
 
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Oct 22, 2018 at 5:58 AM Post #4 of 26

WoodyLuvr

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Thus far, it is dead silent even with the volume pot at max volume.

Here are some details and specs:

"OPA1688 Parallel Super CMoy dual-chip headphone amplifier with a real ground and a headphone relay for zero turn-on or turn-off thump and essentially zero (250uV) DC output offset voltage. Uses two of the brand new Texas Instruments OPA1688 ( http://www.ti.com/product/OPA1688 ) headphone driver chips in parallel for 150mA output per channel (6x the output of most op-amps). Ultra low distortion with extremely low idle current for long battery life. Uses 2 9V batteries with a real ground and "solid state relay" technology - no virtual grounds or rail splitters to distort the sound." - agdr audio

150 mA output per channel
zero output impedance (yes, 0 Ohms)
unity gain

 
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Oct 22, 2018 at 4:08 PM Post #6 of 26

adydula

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The OPA 1688 is a very nice op amp.....and its nice to see TI making a chip designed especially for this area of our hobby.

AGDR did a great job designing this amp in its form factor and I was elated to wire it up and it worked wonderfully for me.

I actually built three of them in AGDR's development phases....I still have a prototype and a single 1688 version. Sonically they are identical.

I dont know if AGDR is still selling the pc boards..but you can PM him over at diyaudio.com

Some of the soldering is indeed challenging!!

Enjoy!
Alex
 
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Nov 4, 2018 at 1:03 AM Post #9 of 26

WoodyLuvr

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Oh my this little amp sure is powerful!

I have had to set foobar2k music player down to -16dB so it won't blow up my 32Ω Nhoord Reds or 300Ω Blurs! It pushes both drivers way too hard especially on a few prominent sub-bass tracks that I have (e.g. Gustav Holst: The Planets, Op.32/H.125: vii. Neptune, the Mystic; Andante Original Ending - Mark Elder; Hallé Orchestra & Choir or Jóhann Jóhannsson's Sicario: ii. The Beast).

System volume (Win10) is still set at 100% though.

Full Specs for agdr Audio OPA1688 Parallel Super CMoy
Output Impedance (ohms): ~0 Ω
Voltage Gain: 1x ("unity-gain amplifier")
Peak Voltage Swing: 7.4 V (aka Vp or Vdc)
Peak Output Current: 150 mA per channel
RMS Output Voltage: 5.23Vrms
RMS Output Current: 106.05mA rms per channel

Maximum Power (rms): 181 mW @ 16Ω (1.7 V)
Maximum Power (rms): 360 mW @ 32Ω (3.4 V)
Maximum Power (rms): 427 mW @ 64Ω (5.23 V)
Maximum Power (rms): 228 mW @ 120Ω (5.23 V)
Maximum Power (rms): 182 mW @ 150Ω (5.23 V)
Maximum Power (rms): 91 mW @ 300Ω (5.23 V)
Maximum Power (rms): 46 mW @ 600Ω (5.23 V)

So this 'little dual-chip head amp that could' should be able to handle not only the power hungry HE6 driving them up to ~105 dB SPL but the mighty AKG K1000 as well... albeit only driving it to 97 dB SPL which is still doable for all but the most dynamic/heavy sub-bass pieces.
 
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Nov 5, 2018 at 5:00 AM Post #10 of 26

DavidA

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I'm so glad that you show sound technical info since lately there are so many that say you need an amp with 1.21 GW of power for even average headphones on some threads but I've found that its more of a synergy effect that tends to make one amp pair better with some headphones over other amps. My Teac UD301 headphone output only has 100mW but even it is enough for my HE560 and LCD-2f but there are still those that are recommending amps of >4W for them.

FWIW I wish I had the time and knowledge to build an amp like you or another Head-Fi member who let me try a powerDAC (a bit like a Mojo) that he built for driving a HE400i but it has enough juice to drive even my HE560 which needs a bit more grunt to get to my listening levels.
 
Nov 5, 2018 at 2:08 PM Post #11 of 26

WoodyLuvr

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I'm so glad that you show sound technical info since lately there are so many that say you need an amp with 1.21 GW of power for even average headphones on some threads but I've found that its more of a synergy effect that tends to make one amp pair better with some headphones over other amps. My Teac UD301 headphone output only has 100mW but even it is enough for my HE560 and LCD-2f but there are still those that are recommending amps of >4W for them.

FWIW I wish I had the time and knowledge to build an amp like you or another Head-Fi member who let me try a powerDAC (a bit like a Mojo) that he built for driving a HE400i but it has enough juice to drive even my HE560 which needs a bit more grunt to get to my listening levels.
Concur, I don't get most of those "more power required" recommendations you speak of nor do the audiophiles that I know here in Thailand whom are very high level electrical engineers! Now there are a few (very few) headphones out there that are indeed power hungry and do require a higher voltage swing to perform well but not the amounts that are being readily recommended. So what it comes down to with insensitive headphones like the HE6 and K-1000 is not so much about the need for extreme wattage but rather the quality amp and it's power supply (synergy being part of that of course).

Look at the recommended specs for your HiFiMAN HE-560:

Nom. power rating: 2W (estimated)
Max. voltage: 10V
Max. current: 210mA
Max. S.P.L.: 119dB
Impedance: 45 Ω
Efficiency: 86 dB/1mW (99dB/1V)

So your HE560s only need 251mW, 75 mA, and 3.4V to reach 110 dB SPL. Your TEAC UD301 is driving your HE-560s perfectly fine providing 106 dB SPL and there is enough dynamic headroom there to handle sub-bass demands. As per the bottom portion of the table a 4W amp hooked up to your HE-560s would be very unwise... feeding your cans over 13.5V @ 300mA which is way beyond the recommended specs for your cans.

The only headphones I can think of that truly would require a ~4W amp to reach ~110 dB SPL would be the almighty AKG K-1000... they require ~182 mA @ ~21.8Vrms! However again, with only 40mW @ 18mA and 2.2V the K-1000 can be easily driven to a very listenable 90dB SPL with all but the most dynamic and sub-bass heavy tracks.

So where does one draw that line of diminishing returns in regards to a higher wattage amp and better yet wouldn't one rather focus on better build quality and power supply than seeking higher wattage?
 
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