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xrk971 Pocket Class A Headamp GB
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Old 13th November 2017, 07:22 PM   #1341
stellarelephant is offline stellarelephant  United States
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Took me a minute...LOL
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Old 14th November 2017, 06:02 PM   #1342
Aatto is offline Aatto  United States
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Done with the desktop version, just wanted to share this here.

xrk971 Pocket Class A Headamp GB-_dsc6792-jpg

A.
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Old 14th November 2017, 06:15 PM   #1343
xrk971 is online now xrk971  United States
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Super work Aatto! Beautiful case work.
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Old 14th November 2017, 06:31 PM   #1344
prasi is offline prasi  India
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Quote:
Originally Posted by Aatto View Post
Done with the desktop version, just wanted to share this here.
A.
Super work.. Congratulations!

regards
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Old 14th November 2017, 11:18 PM   #1345
Aatto is offline Aatto  United States
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thanks :-) cheers
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Old 15th November 2017, 11:02 AM   #1346
twocents is offline twocents  South Africa
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Stunning case Aatto. Does it sound as beautiful as it looks?
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Old 15th November 2017, 10:17 PM   #1347
Aatto is offline Aatto  United States
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thanks i appreciate it, it sounds even better
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Old 17th November 2017, 01:06 AM   #1348
stellarelephant is offline stellarelephant  United States
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Another beautiful looking head amp, Aatto! What are you using for a heat sink? Are you keeping the bottom wide open for ventilation? Any additional noise from having the SMPS in the case? I also would love to hear your take on the sonic differences between your ZVN4306 build versus this one with the IRF10. Gathering ideas for my eventual desktop build...
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Old 17th November 2017, 03:49 AM   #1349
Aatto is offline Aatto  United States
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Quote:
Originally Posted by stellarelephant View Post
Another beautiful looking head amp, Aatto! What are you using for a heat sink? Are you keeping the bottom wide open for ventilation? Any additional noise from having the SMPS in the case? I also would love to hear your take on the sonic differences between your ZVN4306 build versus this one with the IRF10. Gathering ideas for my eventual desktop build...
Thanks
for heat sink i use a 100x35mm heat sink i bought from ebay, and the bottom piece have some ventilation openings by the heat sink and by the board itself since JFETS and specially the resistors tends to run warm, i do not have a build with ZVN4306 at the moment to do a side by side comparison but it has the same character since I use the same BF862 JFETs, it maybe my imagination but i think IRF10 build is a little louder, the only thing i noticed is that the input 10uF Silmic II caps can emphasis some low mid freqs on certain records ( depends on the record ) not on everything, which is not that noticeable but it's there, it's not annoying enough to push me to switch it back to WIMAs.
as for using SMPS, the amp is dead silent, no noise no hiss or hum coming out of the cans when nothing is playing. going for laptop power supply was the best idea, they are dirt cheap, i got mine for 8$ with free shipping.

Last edited by Aatto; 17th November 2017 at 03:51 AM.
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Old 17th November 2017, 03:02 PM   #1350
xrk971 is online now xrk971  United States
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You now know the secret of a dead silent PSU: start with SMPS at wallplug, go to cap Mx, follow with CRCRC.

I have a new SE Class A preamp design that just finished tweaking and testing last night. It is capable of 40vpp to drive the most difficult unity gain power amps. The distortion levels and profiles are amazing and made possible by using a SMPS and cap Mx CRCRC PSU. I added a DC step up after a 12v SMPS to get 45v to 48v needed.

AKSA's Lender Preamp with 40Vpp Output

Look at this measured FFT - and this is running from a wallplug. Look at the absence of any peaks near line mains 60Hz/120Hz/180Hz. Noise floor is limited by sound interface (Focusrite Solo 2G).
Here is 20v p-p into 7k load:
Click the image to open in full size.

Here it is driving a more typical level of 4vpp into 3.4kohmmload:
Click the image to open in full size.

Who says you need a lot of transistors to achieve almost no distortion. Certainly 6 actives here works quite admirably.

Here is stereo preamp with step up, cap Mx, CRCRC. This is an all BJT design except for the constant current source which is a depletion mode n channel mosfet BSP129 (on left). On right is a DZT5401 PNP capable of 600mA.

Click the image to open in full size.
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Last edited by xrk971; 17th November 2017 at 03:11 PM.
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