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Old 2nd February 2012, 12:57 PM   #1021
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For the thermistor :

1.6A bias translates to ~150W dissipation. With transformer and rectifier losses, assume some 200VA going in on the primary side.
Mains on your end is likely 220Vac, 200VA divided by 220V makes ~0.9A

Suppose you used a CL-110 thermistor from General Electric, 10R and 3.2A
At 0.9A current, it would have a resistance of about 1 Ohm, thermistor steady-state dissipation would be around 3/4 W.

(from back of my head guessti-culus, you can pinpoint the exact figures if you download a CL datasheet and type in the numbers)

The primary fuse is for your protection, not the output stage.
Whatever you feel comfortable with.
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Old 5th February 2012, 02:58 PM   #1022
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I didn't find at my supplier same value resistors for R9-R13(221 ohms) closest values that I found are 210 ohms and 237 ohms.Now i know that for R9-R12 I could use 210-237 ohms
without problems, but what about R13? would be ok one of those two values? which one?
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Old 5th February 2012, 10:31 PM   #1023
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Hardly makes a difference, Q3 is just a safeguard.

R13+R14 make a voltage divider, Q3 is turned on when the current through Q7 goes above a couple of amps, draws down the voltage on the gates of Q7+Q8.
210 or 237 makes peak current go up/down 2 to 3%.
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Old 6th February 2012, 06:20 AM   #1024
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Thank You
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Old 10th February 2012, 05:27 PM   #1025
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Hello

I want to build the amp with Peter Daniels boards and will be two monoblocks.Now i don't know where to mount the boards exactly but I am thinking at two possibilities :
first one is to mount the board on the rear panel and connect each of the mosfets with 1.5 mm diameter and 20-22cm long wire
second one is to mount the board on one of the heatsinks and solder Q7 and Q8 directly so I will have a short signal path and connect with 1.5 mm diameter and 20-22cm long wires only Q5 and Q6 (ccs)
Heatsink size is 300x164x40 mm and interior of amplifier case is 300x164x200 mm
What do you recommend?
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Old 10th February 2012, 05:53 PM   #1026
Zen Mod is offline Zen Mod  Serbia
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put pcb horizontally in a middle of the amp

then shorter wires for mosfets left and right

it's wise to ensure that mosfet's gate resistors are near gate pins
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Old 10th February 2012, 07:17 PM   #1027
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Thanks.I will try to design something to see how it will look like
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Old 10th February 2012, 08:50 PM   #1028
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More easy is to mount the board on one heatsink because you have sufficient space, thus you can screw the IRF's directly on the heatsink using mica or polyimide sheets for electrical isolation.
The PSU you can mount flat on the bottom together with the rectifiers.
This is the way I have even assembled the stereo version in one case, without any thermal problem.
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Old 17th February 2012, 03:05 PM   #1029
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How can I read the psu ripple from the attached photos?
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Old 17th February 2012, 05:19 PM   #1030
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By reading the table ?

[Smart man calculates by head to check. First 66,000uF (33,000) capacitor & 4A current gives primary ripple (easy formula). 0R5 plus second 66,000uF (33,000) cap makes a standard RC filter ]
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