Building a symmetrical psu B1 buffer - Page 181

Salas · 16th July 2010, 04:36 PM

Any stable DC source, its only a utility. Get a 2SK170 low IDSS, 2N5459 ,or any other 5-6mA IDSS NJFET, connect its drain at B(+), connect its G&S together, crock lead LED's anode there too. Return cathode to (-). Measure Vf across lit LED. Stick it on paper, note its Vf. Repeat for some. Do the sorting later picking from the noted bunch. Alternative and more precise to a resistor.

korben69 · 16th July 2010, 04:53 PM

Thanks Salas,
I was just wondering about the method, stable DC source.
I've done the matching 3 times, very close measures.
I'll try to match 2SK170 too

Schematic here : Transistor matching

Salas · 16th July 2010, 04:59 PM

Just that is enough. Let the fets stabilize for 3 mins, and watch not to short the dvm, it will blow a fuse.

korben69 · 16th July 2010, 07:12 PM

Thank you for the advices !

korben69 · 18th July 2010, 06:24 PM

2SK170BL Matching session today about 100 units.
Results using the previous posted link schema :
6.51/6.52 - 6.61/6.62 - 6.67/6.67 - 6.95/6.96
7.11/7.12/7.13 - 7.17/7.18 - 7.26/7.27 - 7.39/7.39 - 7.48/7.49 - 7.65/7.65 - 7.94/7.94
8.16/8.16/8.16 - 8.49/8.49 - 8.81/8.81 - 8.83/8.83 - 8.96/8.97
9.93/9.94
10.91/10.92

About 18 pairs/trio found.

Question
Which of them should I prefer using in Q1/2 and Q3/4 position as shown in this pic ?
Thanks

Salas · 18th July 2010, 06:33 PM

7.12/7.11 - 7.17/7.18 1,2,3,4

korben69 · 18th July 2010, 06:42 PM

Thank you Salas
It will equilibrate the values in this order Q1:7.12/Q3:7.17 and Q2:7.11/Q4:7.18
Am I right ?

Salas · 18th July 2010, 06:43 PM

No, fit just as I gave the order.

korben69 · 18th July 2010, 06:44 PM

Yes Sir !

Salas · 18th July 2010, 06:47 PM

At ease!

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16th July 2010, 04:36 PM	#1801
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Any stable DC source, its only a utility. Get a 2SK170 low IDSS, 2N5459 ,or any other 5-6mA IDSS NJFET, connect its drain at B(+), connect its G&S together, crock lead LED's anode there too. Return cathode to (-). Measure Vf across lit LED. Stick it on paper, note its Vf. Repeat for some. Do the sorting later picking from the noted bunch. Alternative and more precise to a resistor.

16th July 2010, 04:53 PM	#1802
korben69 diyAudio Member Join Date: Nov 2006 Location: Near Lyon	Thanks Salas, I was just wondering about the method, stable DC source. I've done the matching 3 times, very close measures. I'll try to match 2SK170 too Schematic here : Transistor matching

16th July 2010, 04:59 PM	#1803
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	Just that is enough. Let the fets stabilize for 3 mins, and watch not to short the dvm, it will blow a fuse.

16th July 2010, 07:12 PM	#1804
korben69 diyAudio Member Join Date: Nov 2006 Location: Near Lyon	Thank you for the advices !

18th July 2010, 06:33 PM	#1806
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	7.12/7.11 - 7.17/7.18 1,2,3,4

18th July 2010, 06:42 PM	#1807
korben69 diyAudio Member Join Date: Nov 2006 Location: Near Lyon	Thank you Salas It will equilibrate the values in this order Q1:7.12/Q3:7.17 and Q2:7.11/Q4:7.18 Am I right ?

18th July 2010, 06:43 PM	#1808
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	No, fit just as I gave the order.

18th July 2010, 06:44 PM	#1809
korben69 diyAudio Member Join Date: Nov 2006 Location: Near Lyon	Yes Sir !