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Old 27th December 2015, 11:32 AM   #1
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Default F5(25W) help with parts and design

Thank you all who responded and helped me with ideas and valuable information.

So i am going for F5(25W), since its class A i don't want more watts if i am not going to use those extra watts. I'll be using some of the hardware that can be used with F5 turbo in case need arises.

Need feedback here
1. Transformer : F5 needs 300-500VA and F5 Turbo 600-800VA,
i can get 500-800VA locally but which transformer should i go for, what output should i look for that will work with both F5 and F5T?
http://www.toroidal.com/toroidal-transformers2
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Old 27th December 2015, 12:39 PM   #2
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for standard F5 power range (25W/8R) , you need xformer with two separate 18Vac secondaries

for Turbo - look in article

separate econdaries are intended for 2 bridge per xformer arrangement , which is sort of better than 1 bridge/center tap approach , which is sensitive to unequal load on secondary halves

when purchasing , give a note that xformer is intended for A class amp , loaded constantly with 160VA (in case of one xformer/PSU for both channels )
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Old 27th December 2015, 03:50 PM   #3
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thankyou Zen

F5 its 18V(2 separate secondaries)
For F5Turbo its 24V(2 separate secondaries)

Can i use 600VA 24V(2 separate secondaries) and use regulation to output 18V?
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Old 27th December 2015, 03:59 PM   #4
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no need for regulation , just use higher rails

start with F5T schematic without diodes in parallel to source resistors (that needs exact Iq , so plenty in sum) , use higher rails , crank Iq according to heatsinks
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Old 27th December 2015, 04:26 PM   #5
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Quote:
Originally Posted by captJackSparrow View Post
thankyou Zen

F5 its 18V(2 separate secondaries)
For F5Turbo its 24V(2 separate secondaries)

Can i use 600VA 24V(2 separate secondaries) and use regulation to output 18V?
Yes, you can reduce the rail voltage by inserting a voltage regulator. But a voltage regulator will dissipate a lot of power / heat in this position, isn't really necessary (or useful), and may be waste of money; I wouldn't go that route. Use a transformer with the proper specs instead.
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Old 27th December 2015, 05:19 PM   #6
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or , if you are taking custom xformer , ask for secondary taps on 18Vac (with full at 24Vac)
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Old 28th December 2015, 01:57 AM   #7
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custom with two secondary sounds a better idea.

Thank you
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Old 28th December 2015, 02:19 AM   #8
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and nothing new under the sun

some Japanese amps (mainly with sort of STK IC in OS) had at back selector for 4/8 load - nothing else than selector for secondary voltage tap - full (8R load) or lower one (4R load)
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Old 30th December 2015, 01:33 PM   #9
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For JFET/MOSFET can anyone please recommend alternative which are easily available on mouser/digikey having same characteristics as toshiba components that use to be available

2SJ108

2SK370

IRFP240

IRFP9240
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Old 30th December 2015, 01:41 PM   #10
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for JFets ,see in Diyaudio store (LSK , B range) , or member spencer for original Toshiba (2SJ74BL/2SK170BL)

regarding IRFP , there is no need for alternative
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