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Question about the current biasing pots on the placid bp 2.1.2
Rank: Member
Groups: Member
Joined: 4/6/2009(UTC)
Posts: 12
Location: Oslo, Norway
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Hello! First, thank you very much for making all those nice kits - which I have been bying many of and listening a lot to. I am now taking a look at the schematic for the newest version of the Placid Bipolar Power Supply, and there are a couple of details there that don't make sense to me... The 200 ohm current bias pots VR1 and VR2 are on the newest version of the Pacid BP apparently connected in series with the main current through the output power transistors. Shouldn't those biasing pots instead be in parallell with the base-emitter voltage drops of QP1 and QN1, as they are in the old BP version and in both the new and old single versions? With best regards from audiophile, Oslo, Norway Edited by user Friday, May 21, 2010 6:40:41 AM(UTC)
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
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It is designed to work this way. The new placid BP uses a fixed voltage for the base voltage. This is intentional. :)
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Rank: Member
Groups: Member
Joined: 4/6/2009(UTC)
Posts: 12
Location: Oslo, Norway
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Hello again!
I see that you with a variable series resistor here will be able to open up or to choke the current through QN1 and QP1 in this setup, when the LEDs D5 and D6 serve as fixed voltages. But my concern was the amount of current driven through those tiny trim pots. Will they take the punishment of hundreds of mA's through them...?...
- Excuse me for beeing such an annoyance on this one :)
You are, nevertheless, making some fine products.. :)
best regards from
audiophile, Oslo, Norway
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
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Absolutely they are fine. They are well within their rating.
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Rank: Member
Groups: Member
Joined: 4/6/2009(UTC)
Posts: 12
Location: Oslo, Norway
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Ok, no worries then... :)
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Question about the current biasing pots on the placid bp 2.1.2
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