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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 6th November 2017, 02:47 PM   #471
Mayday is offline Mayday  Sweden
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BF862 based SE Class A Headamp without the HEAT
Thanks
They are 13.4 to 13.8mA IIRC.
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Old 8th November 2017, 08:24 AM   #472
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BF862 based SE Class A Headamp without the HEAT
I went over the boards with the DMM, with PS wires connected as in the attached pics, I got about 22R between VCC and GND. Is that correct?
I had to use 10000uF/25V Dubilier (x2) and 1000uF/35V Panasonic FC as there's no way to fit two of the 22000uF caps on the board.
Edit: resistors on GND side are not yet populated.
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File Type: jpg IMG_20171108_084031.jpg (293.8 KB, 189 views)
File Type: jpg IMG_20171108_084207.jpg (165.8 KB, 188 views)
File Type: jpg IMG_20171108_084056.jpg (290.7 KB, 175 views)
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Old 8th November 2017, 03:17 PM   #473
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BF862 based SE Class A Headamp without the HEAT
Looking good Mayday!

BF862's are N-junction depletion-mode FETs, which are normally conducting (self-biasing capable) when no voltage is applied to the gate. 22R is probably result of natural conduction in the nominal no-voltage applied state. With a 20v rail that would be nearly an amp, nut max is limited by Idss of BF862 (around 10 to 25mA). I think nominal operating bias current is about 50mA to 60mA if I recall, so should go down once powered up.
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Old 8th November 2017, 03:38 PM   #474
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BF862 based SE Class A Headamp without the HEAT
Quote:
Originally Posted by xrk971 View Post
Looking good Mayday!

BF862's are N-junction depletion-mode FETs, which are normally conducting (self-biasing capable) when no voltage is applied to the gate. 22R is probably result of natural conduction in the nominal no-voltage applied state. With a 20v rail that would be nearly an amp, nut max is limited by Idss of BF862 (around 10 to 25mA). I think nominal operating bias current is about 50mA to 60mA if I recall, so should go down once powered up.
Hi,
Thanks
With the boards not connected via PS wiring I got 42R.
The devices are 13.4 to 13.8mA Idss.
I got the resistor needed to complete the headamp today. 715R as I didn't find 710R, does that matter?
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File Type: jpg IMG_20171108_152758.jpg (271.7 KB, 162 views)
File Type: jpg IMG_20171108_152721.jpg (394.6 KB, 154 views)
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Old 8th November 2017, 08:59 PM   #475
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BF862 based SE Class A Headamp without the HEAT
Quote:
I got the resistor needed to complete the headamp today. 715R as I didn't find 710R, does that matter?
Sorry you were waiting on that. Not critical at all, anything from 220R to 2k would have worked
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Old 8th November 2017, 09:11 PM   #476
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BF862 based SE Class A Headamp without the HEAT
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Sorry you were waiting on that. Not critical at all, anything from 220R to 2k would have worked
Well, no worries as I still need to get two more 5W resistors for the CRCRC filter.

Gives me the chance to work on the enclosure for the DAC/headamp combo.
Today I sanded and put the first layer of varnish on the wooden side panels.

Edit: I have two of the same enclosures, that's why there's 4 side panels.
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File Type: jpg IMG_20171108_114112.jpg (660.2 KB, 63 views)
File Type: jpg IMG_20171108_134558.jpg (457.9 KB, 62 views)
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Old 8th November 2017, 09:52 PM   #477
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BF862 based SE Class A Headamp without the HEAT
1W or even 500mW resistors can work for your CRC. We are taking flow of maybe 120mA here Class A so steady.
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Old 9th November 2017, 04:38 PM   #478
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Put a second layer of varnish on the wooden sides.
I also started drilling holes in the alu-enclosure.
Also attached a picture of the DAC board and the XMOS board that will feed the headamp via edcor WSM transformers (600:2K4).
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File Type: jpg IMG_20171109_093210.jpg (146.2 KB, 35 views)
File Type: jpg IMG_20171109_144954.jpg (412.9 KB, 44 views)
File Type: jpg IMG_20171103_100827.jpg (694.1 KB, 81 views)
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Old 9th November 2017, 05:06 PM   #479
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Nice work. You did a DIY DAC? Very cool. I like xmos USB adapter too. I got this and it works quite well. Has BB PCM5102 DAC. Nowadays I mostly use the Focusrite 2i4 2nd gen as a DAC and that sounds very good too. Capable of high speed rates.

New version Assembled XMOS U8 + PCM5102 + TDA1308 USB Coaxial DAC Sound Card 32bit 384K headphone Output ,Free Shipping-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
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Old 9th November 2017, 05:18 PM   #480
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BF862 based SE Class A Headamp without the HEAT
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Originally Posted by xrk971 View Post
Nice work. You did a DIY DAC? Very cool. I like xmos USB adapter too. I got this and it works quite well. Has BB PCM5102 DAC. Nowadays I mostly use the Focusrite 2i4 2nd gen as a DAC and that sounds very good too. Capable of high speed rates.

New version Assembled XMOS U8 + PCM5102 + TDA1308 USB Coaxial DAC Sound Card 32bit 384K headphone Output ,Free Shipping-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Hi,
I have several DIY DAC's in different stages of completion lol.
Dual pcm1794, 3pcs populated Red Baron boards, a WM8740 board, two XMOS boards (one is the later XU208 IC), 3pcs audio-widget USB to IS boards of which one is populated and flashed with firmware, a few WM8805 SPDIF to IS boards (had those made by a board house, the dual pcm1794 too as it's a 4 layer board), one 8x TDA1387 board nearly done, one ES9018K2M board, two or three ES9023 boards and one analog metric completed dac with passive I/V and tube output.
A home etched WM8804 SPDIF to IS board (most fine pitched board I've etched thus far).
I think I remembered them all lol
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