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Old 28th April 2012, 05:32 PM   #1031
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Old 30th April 2012, 10:23 AM   #1032
protos is offline protos  Greece
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Quote:
Originally Posted by Salas View Post
Maybe a bit OT, maybe not given this kind of amp's power supply range. There are $200 double and $130 single linear high current regulated bench supplies about. I have a double 30V 5A unit for series linking up to 60V high or up to +/-30V symmetric. Also because I could find one of the fan-less variety in doubles. Maybe good for checking out such amps fast, listening, and then deciding to keep and build them their own costly supplies. And for a number of other projects of course. For Matching MOSFETS, SiC JFETS, SITS, also. But don't use it as a circuit's CCS, you remember it did not work correctly for member Protos amp. It takes to fit an NTC primary side not to trip 10A breakers (I put one there). That trafo is 500VA easily. Construction is so-so, but OK for the price. Its meters look set true. Setting the scope's trigger for single shot, I captured the power on event. Looks smooth, no over voltage or ringing. That one's a 5V/Div 100mS/Div ramp up.
I was looking at those recently. I always felt slightly challenged with single linear supply.What is the best source to buy from?
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Old 1st May 2012, 12:39 AM   #1033
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Please excuse my lack of transistor knowledge here. Is bias the same as Id (indicated by the arrow) and determined by the setting of P1?

Regards,
Dan

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Old 1st May 2012, 01:58 AM   #1034
Salas is offline Salas  Greece
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Originally Posted by protos View Post
I was looking at those recently. I always felt slightly challenged with single linear supply.What is the best source to buy from?
If you mean in Greece, there are enough on line local retailers with good for European standards price (~220 for the 5 Amp ones) if you will google the brand name + type choosing to show Greek results only. Best prices in general are in USA especially when factoring in $<EUR.
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Old 1st May 2012, 02:51 AM   #1035
Salas is offline Salas  Greece
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P.S. If you will get another same single you can still link them in series and have the equivalent of a double with less cost and still utilizing the older one.
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Old 1st May 2012, 04:05 PM   #1036
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Originally Posted by dantwomey View Post
Please excuse my lack of transistor knowledge here. Is bias the same as Id (indicated by the arrow) and determined by the setting of P1?

Regards,
Dan

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Yes, sounds like you've got the idea.

Id is controlled by the voltage between the Gate and Source pins. Here, P1 adjusts this voltage. Id is temperature dependent and will need to be adjusted initially, and again after an hour, once things have equalized.
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Old 1st May 2012, 06:36 PM   #1037
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hohoho les amis, the SIT now sing with my 2 supermalloy grid choke .
with the high AC impedance i can now reduce the coupling Cap to a 0.22uf VCAP CUTFT .. sounds very very good now and sure i 'll stay with No source degeneration version
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Old 1st May 2012, 06:54 PM   #1038
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Great juanitox !!
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Old 1st May 2012, 07:40 PM   #1039
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Old 2nd May 2012, 06:17 PM   #1040
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Originally Posted by Michael Rothacher View Post
Yes, sounds like you've got the idea.

Id is controlled by the voltage between the Gate and Source pins. Here, P1 adjusts this voltage. Id is temperature dependent and will need to be adjusted initially, and again after an hour, once things have equalized.
Michael,

Thanks for your response. After some searching I finally found a novice-friendly description of JFet biasing.

Regards,
Dan

FET biasing - Electronic Circuits and Diagram-Electronics Projects and Design

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