HPS 4.0 phono stage - Page 35

Joachim Gerhard · 3rd January 2010, 04:18 PM

People at Revox (i know the design team very well) told me about the BF682. They got great results so you are in good company. As far as i can see from the data sheet they have between 25 and 40mS so some sorting may be needed. Idss varies a lot too, between 10 and 25mA.

kamis · 22nd May 2010, 08:28 PM

Syn08, how close parallel transistors (N to N and P to P ) should be matched in HPS-4.0 ? I wish to use Sanyo 2SC3601 and 2sa1407 of which I have many pairs, all E gain groups.

syn08 · 22nd May 2010, 11:05 PM

Quote:

Originally Posted by kamis

Syn08, how close parallel transistors (N to N and P to P ) should be matched in HPS-4.0 ? I wish to use Sanyo 2SC3601 and 2sa1407 of which I have many pairs, all E gain groups.

Same beta class is more than enough. Just make sure you trim the pot to cancel the input current. It can be done down to 20nA.

kamis · 23rd May 2010, 09:28 AM

Quote:

Originally Posted by syn08

Same beta class is more than enough. Just make sure you trim the pot to cancel the input current. It can be done down to 20nA.

Thank you. I think that HPS-4.0 pcb PT holes are not wide enaugh for TO-126 transistor leads.

syn08 · 23rd May 2010, 03:16 PM

Quote:

Originally Posted by kamis

Thank you. I think that HPS-4.0 pcb PT holes are not wide enaugh for TO-126 transistor leads.

Right, they are not.

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3rd January 2010, 04:18 PM	#341
Joachim Gerhard diyAudio Member Join Date: Mar 2009	People at Revox (i know the design team very well) told me about the BF682. They got great results so you are in good company. As far as i can see from the data sheet they have between 25 and 40mS so some sorting may be needed. Idss varies a lot too, between 10 and 25mA.

22nd May 2010, 08:28 PM	#342
kamis diyAudio Member Join Date: Mar 2006 Location: Obrenovac,Serbia	Syn08, how close parallel transistors (N to N and P to P ) should be matched in HPS-4.0 ? I wish to use Sanyo 2SC3601 and 2sa1407 of which I have many pairs, all E gain groups.

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