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AKSA's Lender Preamp with 40Vpp Ouput GB
AKSA's Lender Preamp with 40Vpp Ouput GB
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Old 13th January 2018, 02:53 PM   #261
schlomoff is offline schlomoff  France
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top received today, merci
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Old 14th January 2018, 10:51 PM   #262
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Ouput GB
Alert on main PCB. Schematic has error on R141. Should be 10k not 220R. This is the resistor on the cap multiplier.

Sorry did not catch this earlier.
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Old 14th January 2018, 11:24 PM   #263
Vunce is offline Vunce  United States
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AKSA's Lender Preamp with 40Vpp Ouput GB
Good thing it’s not R143!!
That one is buried and would be very difficult to
remove/replace:-)
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Old 15th January 2018, 12:05 AM   #264
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Ouput GB
I think I found a cheap easy solution to the X121 connector: use standard PCB headers cut down to size, use two strips.
AKSA's Lender Preamp with 40Vpp Ouput GB-mb-no2-connector-solution-jpg

Here is my completed board number 2, built with the "good stuff" (all name brand caps) configured specifically to be a headphone amp (1000uF 63v output caps):
AKSA's Lender Preamp with 40Vpp Ouput GB-mb-no2-completed-jpg

I will be using a TH daughterboard with a 2SA1837 in place of KSA1381 (note pins are reversed). Will bias at about 80mA and run from circa 30v Vcc for about 1.2W dissipation.
Attached Images
File Type: jpg MB-No2-Connector-Solution.jpg (372.5 KB, 598 views)
File Type: jpg MB-No2-Completed.jpg (556.8 KB, 595 views)
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Last edited by xrk971; 15th January 2018 at 12:09 AM.
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Old 15th January 2018, 11:46 PM   #265
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Ouput GB
Aksa Lender Headphone amplifier (HPA) completed. I had to move some caps to the bottom to make room for the heatsinks. Running at 130mA for a toasty 1.56w dissipation on 2SA1837 and DN3540 ea. Note that 2SA1837 pins are reversed relative to KSA1381 so fits perfectly on backside of board for more clearance for heatsinks.

Sound is very nice. Powerful and clear - super quiet. Measurements to come later but it is about 0.006% THD for 1.0Vpp into 50ohms with mostly H2 and H3, as usual for Aksa Lender topology.

AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-hpa-amp-cores-jpg

AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-hpa-amp-cores-2-jpg

AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-hpa-amp-main-bottom-jpg

AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-hpa-amp-main-jpg

Edit - just got measurements done...

Measurements for 1.0Vpp into 50ohms, THD is coming in at 0.007% but very nice profile.
AKSA's Lender Preamp with 40Vpp Ouput GB-aksa-lender-hpa-130ma-1-0vpp-50hms-png

Will do some listening now for a while and report back later.
Attached Images
File Type: jpg Aksa-Lender-HPA-Amp-Cores.jpg (481.2 KB, 468 views)
File Type: jpg Aksa-Lender-HPA-Amp-Cores-2.jpg (461.4 KB, 4978 views)
File Type: jpg Aksa-Lender-HPA-Amp-Main.jpg (564.0 KB, 4773 views)
File Type: jpg Aksa-Lender-HPA-Amp-Main-Bottom.jpg (456.7 KB, 345 views)
File Type: png Aksa-Lender-HPA-130mA-1.0Vpp-50hms.png (85.0 KB, 2994 views)
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Last edited by xrk971; 15th January 2018 at 11:51 PM.
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Old 15th January 2018, 11:49 PM   #266
pinnocchio is offline pinnocchio  Canada
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Got my boards today, Thanks!!

Do
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Old 16th January 2018, 04:36 AM   #267
sumotan is offline sumotan  Indonesia
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Am I too late, are the boards still available ?

Thanks
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Old 16th January 2018, 05:00 AM   #268
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Ouput GB
Yes, boards are still available. Send me your PayPal address and qnty and type of board(s) you want.
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Old 16th January 2018, 05:04 AM   #269
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Ouput GB
Listening with my DT880-250's now and sound is excellent. However, 13dB (4k7/1k) gain is not enough. Will need to increase to 6k8 I think. Probably can lower bias to about 105mA as 130mA is pretty hot on those small heatsinks. Right now using two 22ohm in parallel (11ohms) for R15 to set the bias. With the DN2540, the bias runs higher than the same resistor value for BSP129. A 33R and 22R parallel should give me 13.2 ohms for about the right lower bias setpoint. Another option when running lower bias is it allows higher Vcc for high impedance cans running higher gain.
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Old 16th January 2018, 05:29 AM   #270
xrk971 is offline xrk971  United States
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AKSA's Lender Preamp with 40Vpp Ouput GB
Sorry, typo here - this is 2.0vpp.

Click the image to open in full size.
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