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BF862 based SE Class A Headamp without the HEAT
BF862 based SE Class A Headamp without the HEAT
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Old 11th November 2017, 11:47 AM   #481
xrk971 is online now xrk971  United States
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BF862 based SE Class A Headamp without the HEAT
Wow, quite the DACmaster.
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Old 11th November 2017, 02:39 PM   #482
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BF862 based SE Class A Headamp without the HEAT
Not really lol
I like to build stuff, and I have alot of projects going at once.
Some would call that a bad thing as my builds tend to take a while to complete.
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Old 12th November 2017, 08:22 AM   #483
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BF862 based SE Class A Headamp without the HEAT
I've gotten a bit more done on this build.
CapMx, CRCRC filter, XMOS to I2S board, CS4397 board, P2P wired LM7812 and some other stuff is mounted in the enclosure. The 7812 is for dropping the +24Vdc to more managable +12Vdc for the two LT1963 that supplies analog and digital supplies to the CS4397.
Still a few things left to do, but I'm slowly getting there.
Edit: the "gunk" is clear, non-conductive silicone glue.
Attached Images
File Type: jpg PS_Wiring_2.jpg (424.3 KB, 220 views)
File Type: jpg CS4397_XMOS_Wiring_1.jpg (893.0 KB, 211 views)
File Type: jpg Enclosure_populating_3.jpg (375.2 KB, 205 views)
File Type: jpg PS_wiring_CS4397_1.jpg (843.3 KB, 202 views)
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Last edited by Mayday; 12th November 2017 at 08:24 AM.
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Old 14th November 2017, 09:37 AM   #484
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BF862 based SE Class A Headamp without the HEAT
All wiring apart from PS wiring is temporarily done. For the headamp part of the project.
I'll shorten some wires and solder in some when I've tested that everything works. Cable to and from the ALPS is four lead shielded cable with shield connected in one end (to gnd).
Question: I know the bcl clone and ad797/buf634 headamp works as preamp, would this design be able to drive two 20Kohm loads in parallel?
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File Type: jpg 20171114_105104.jpg (298.1 KB, 169 views)
File Type: jpg 20171114_105134.jpg (317.1 KB, 52 views)
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Old 14th November 2017, 06:48 PM   #485
xrk971 is online now xrk971  United States
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BF862 based SE Class A Headamp without the HEAT
Driving two 20k loads is nothing. I use my pocket SE Class A amp as a preamp on my main speaker system. This particular amp should be able to drive 30ohm loads so 20k or 10k is nothing.
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Old 14th November 2017, 07:04 PM   #486
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BF862 based SE Class A Headamp without the HEAT
Quote:
Originally Posted by xrk971 View Post
Driving two 20k loads is nothing. I use my pocket SE Class A amp as a preamp on my main speaker system. This particular amp should be able to drive 30ohm loads so 20k or 10k is nothing.
I figured that it would be a simple task it.
Not familiar with this type of topology so I thought best to ask.
Thanks
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Old 15th November 2017, 10:09 AM   #487
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BF862 based SE Class A Headamp without the HEAT
Getting close to first power on of this project.
I seem to have misplaced all my fuses when moving workspace, I've found two of a couple of hundred. The ones I found are both fast blow, one is 100mA, the other 400mA. I'll put the fuse straight at the 24Vdc in, before the capacitance multiplier. Will any of the two work until I find my collection of fuses? I guess I can rule out the 100mA right away.
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Old 15th November 2017, 10:39 AM   #488
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BF862 based SE Class A Headamp without the HEAT
Found a few more:
125mA slow
200mA fast
250mA fast
315mA both slow and fast
750mA fast
800mA slow

I found a few more, these are the ones I think may work.
If it were only the headamp and CS4397 I could calculate the value to use, but I don't know the CapMx (the current it draws on it's own) and I need to account for the two LT1963 and the 7812 as well as the CapMx.
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Old 16th November 2017, 05:57 AM   #489
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BF862 based SE Class A Headamp without the HEAT
Well, I got around to flipping the switch just now.
0.75A fast fuse was ok, the lower values blew very fast.
I measured Vdc at the PS input of the headamp boards, that slowly rose to about 1.5Vdc. At the input of the CapMx I got slightly under 6Vdc. Figured the 24Vdc SMPS was a dud, but without load I got 25Vdc on that. It's only 1A though, could that be the problem?
I also measured at PS in on the CS4397 board (PS chain for that goes: 24Vdc - 7812 - LT1963 - DAC.
I am supposed to get 5Vdc there, I didn't reach 1Vdc.
I am using the 7812 as the max v-in of the LT1963 is 20Vdc. So, do i have an error somewhere or is the SMPS just not up to the task?
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Old 16th November 2017, 08:01 AM   #490
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BF862 based SE Class A Headamp without the HEAT
I found my error.
Next question, the supply voltage for the headamp boards climbs above 20Vdc. At 20.15Vdc I power off as I am unsure about the max voltage for the jfets.
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