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Old 17th December 2006, 07:48 PM   #1161
Emeric is offline Emeric  France
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1- What heatsink is advised for the power diodes ?
I want to use these one : RURP3020

http://www.fairchildsemi.com/ds/RU/RURP3020.pdf

i think to employ a 0.9C/w heatsink for 2 rectifier bridges
Is it to much , insufficient or correct ?

2- Do you know the RCore transformer ?

http://www.custommag.com/products/r-core.shtml
http://www.techsavvy.com/industry/fi...sfn/lnc01.html
http://www.lenco-elect.com/r_core_transformers.htm

Do you think it worth to use it ?
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Old 17th December 2006, 08:49 PM   #1162
Netlist is offline Netlist  Belgium
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Both the rectifiers and the transformer criteria depend a lot on the power they'll have to deliver.
A bit of overkill is never bad on a real class A amp.
You'll find a lot of calculators here and on the net.
Roughly, three times the real power dissipation is plenty to stay in the SOA.

/Hugo
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Old 21st December 2006, 07:54 PM   #1163
Emeric is offline Emeric  France
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Hi

How did you calculate the gain of the amp (with this one http://www.kk-pcb.com/alephx.html) ??

And if i replace IRF240 by IRFP044N and if i change the value of 0.47R by 0.44R,
must i change value of some resistor of the circuit ?

Thanks.
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Old 21st December 2006, 09:27 PM   #1164
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As a rule, you don't need to adjust any resistor values
between 240 and 044 devices, as the differences are pretty
minor.

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Old 22nd December 2006, 04:18 PM   #1165
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Hi!

I use the 044n (instead of 044) in Greys schematic.
I changed the R23/R25 from 390 to 360ohm.
With the 390ohm Vgs on the gain devices was too high compared to the CCS devices, and this leads to high DC offset to ground.
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Old 22nd December 2006, 09:48 PM   #1166
Emeric is offline Emeric  France
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I don't understand how to simulate the power supply with PSUD.

In a previous repply (p.26), Hifizen had use a constant-current .
Shouldn't we use a resistor who represent the loudspeakers ?
Because result of the simulation doesn't give the same result (fonction of the impedance of the loudspeaker).

I hope you understand what i'm saying !
()
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Old 23rd December 2006, 07:35 AM   #1167
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Hi,

the PSU is connected to the amp, not to the loudspeaker. Since it is a class A amp the current wont be affected by the speaker impedance or the power that is sent to the speaker.
Therefore you can simulate the load on the power supply by setting the bias current as a constant current.

William
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Old 27th December 2006, 10:37 AM   #1168
Emeric is offline Emeric  France
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Hi all,

What do you think about this configuration ? :

-> CRCRC : 22mF / 1.5Ohm / 22mF / 1Ohm / 47mF .
with a 2x25V transformer .
->On the simulation i have 20V at exit.
->i had simulated it with PSU Designer and with a constant current for the load (4.5A).

Does it work ?
(Because i'm not shure of the result)
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Old 27th December 2006, 12:39 PM   #1169
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Hi,

it will work but have a closer look at the power the R's are dissipating:

2 x 1.5 x4.5^2 plus 2 x 1 x 4.5^2 = ca. 100Watts

This is a bit too much for my liking.

It is much better to use a C-L-C configuration with a 1.5 to 2.2mH coil. This gives a lot less power dissipation and more ripple attenuation.

So something like 47mF-2.2mH-47mF would be nice for 4.5A

William
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Old 27th December 2006, 02:19 PM   #1170
Emeric is offline Emeric  France
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I agree with you but does the L warm if its impedance is 500mOhm ? 10W of dissipation , Is it too much for an AWG14 air coil ?
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