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Old 1st February 2013, 02:21 AM   #61
Jay is offline Jay  Indonesia
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Default Relax... Just check the power supply

Murphy was comparing B1 with WIRE. So naturally the WIRE would win, especially through headphone audition where power supply NOISE will usually be heard.

AFAIK, the original B1 power supply is only on-board regulator. It was advised to have external regulator. And it was not a perfect regulator.

Check also if there is wrong resistor value that will affect impedance.

K389 is imo better than K170.
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Old 1st February 2013, 04:13 AM   #62
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okay thanks Jay, that what I thought really. Its normal that I hear a slight degradation and I never said that the b1 sounded bad for god sake. still I will measure the jfet. Also, I do not use a board, its point to point wiring.

For the powersupply, I have a regulated powersupply WDU12-1900 - TRIAD MAGNETICS - AC-DC CONV, EXTERNAL PLUG IN, | Newark/element14 Canada
then:
PSU Jack -> 3.3 Ohm -> 1,000uF Silmic -> choke -> 1,000uF Silmic ->
Supply to B1 circuit.

What can I do to upgrade that?
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Old 1st February 2013, 05:45 AM   #63
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2sk170bl. Pm me your address.
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Old 1st February 2013, 06:14 AM   #64
lupulin is offline lupulin  United States
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Default psu question

perhaps it will sound better with 18 volts rather than 12?
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Old 1st February 2013, 07:23 AM   #65
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Definitely change the pot to something that is resistor based.
Here are some examples:
δ1 relay-based R-2R stereo attenuator
Dantimax RelVol
HifiCollective
ebay
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Old 1st February 2013, 09:50 AM   #66
AndrewT is offline AndrewT  Scotland
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The LSK389 is the equivalent of the 2sk389.
This is a dual jFET in a 7pin package.
The two jFETs are roughly equal Idss and when wired properly would make an excellent thermally coupled B1.

Do not dismantle. Measure Vgs for the 4 jFETs.
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Old 1st February 2013, 10:04 AM   #67
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Should be equal if not not superior, assuming a great many things.
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Old 3rd February 2013, 12:34 PM   #68
gk7 is offline gk7
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Quote:
Originally Posted by brianco View Post
... LSK389 has incorrect transconductance. [The B version is but marginal],
No, its perfectly suited. (2 matched 2sk170 equivalents in one package.)

Quote:
Originally Posted by brianco View Post
LSK370 is the recommended alternative choice.
No. LSK370 is a multicolor LED made by Siemens.
There is no FET named LSK370.
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Old 3rd February 2013, 12:40 PM   #69
tinitus is offline tinitus  Europe
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I was looking for a j310
could only find it as SMD

I guess all new jfets are SMD
probably not designed to drive ClassA power amps
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Old 3rd February 2013, 12:50 PM   #70
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Bf862 is alternative smd. Can solder leads to pin and pkug right in.
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