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Old 7th December 2009, 03:07 AM   #1
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Default Borbely cascode power requirements

I'm going to build one of the small Borbely cascode amps with the 2SK1058/2SJ162 output pair but would like to know how big a toroid to get for a stereo pair? Also what should the bias current be set for? The rails are going to be +/- 24 volts. Thanks.
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Old 10th December 2009, 10:49 PM   #2
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Anyone? Heres the schematic...
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Old 10th December 2009, 11:14 PM   #3
Zen Mod is offline Zen Mod  Serbia
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Iq up from 1A
when you decide what Iq , calculate dissipation per channel , then multiply that with 2,5 (or even more , if you wish)

example - PSU +/-24V , Iq 1A , that means 48W dissipation per channel ..... which means at least 125VA xformer for one channel

with adequate cooling - I would go to 1A5 Iq , maybe with 2 pairs of output per channel , meaning that each pair have Iq of 750mA

good for xconductance ( read - dampingfactor ) etc ...
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Old 11th December 2009, 05:45 AM   #4
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astouffer,
linearity improves with increasing Iq. Say 250mA would be sufficient to avoid the most nonlinear portion of transfer characteristic. I would set the bias current with just a resistor.
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Old 11th December 2009, 12:40 PM   #5
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Quote:
I would set the bias current with just a resistor.
By changing R21/22?
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Old 11th December 2009, 01:07 PM   #6
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Quote:
Originally Posted by astouffer View Post
By changing R21/22?
no.
By removing Q9.
The inherent temperature stability of the Lateral FETs shown do not require a temperature compensated Vbe multiplier. A resistor is sufficient for applying the gate to gate voltage.
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