ESP 3A output power at 4 ohms load - diyAudio
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Old 17th June 2003, 10:59 AM   #1
Freddie is offline Freddie  Sweden
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Default ESP 3A output power at 4 ohms load

Just measured the output power of my my modified ESP3A amplifier.. Using two pairs of 2SA1216/2SC2922.. Powersupply consists of a 500VA 2*38V toroid transformer, and two 47000uF RIFA caps.

The results into 4 ohms load was:

28,3V RMS, I = 7A (It starts to clip just above this voltage)

So output power is about 200W.. I would have expected slightly more.

Supply voltage (no load): +/-53,6V
Supply voltage (full load): +/-49,6V

So is this normal.. It seems like it only can swing +/-40V.

/Freddie
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Old 17th June 2003, 11:41 AM   #2
Freddie is offline Freddie  Sweden
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The collector resistors of the CFP outputstage is 0,47 ohms.
7A and 0,47R means that I will lose over 3V across those resistors.

Perhaps the output power is reasonable after all.
Think I will reduce those resistor to 0,15R.

Anyone else measured the output power of their ESP 3A?

/Freddie
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Old 17th June 2003, 12:46 PM   #3
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will that drive up the bias?
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Old 17th June 2003, 01:56 PM   #4
Freddie is offline Freddie  Sweden
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Quote:
will that drive up the bias?
It will if I just lower the value of the resistors, but I will readjust the bias to have 100mA.
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Old 18th June 2003, 07:36 AM   #5
Jean is offline Jean  United States
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Hello Freddie,

Did you measure it into a resistive load ? Also for how long ? I would be interested in more specifics of what other components you had to change from the original p3a schematic .
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Old 18th June 2003, 07:52 AM   #6
Freddie is offline Freddie  Sweden
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Quote:
Did you measured it into a resistive load ? Also for how long ? I would be interested in more specifics of what other components you had to change from the original p3a schematic .
Yes, I measured power into a 4 ohm resistive load for a couple of minutes. The 4R resistor got quite hot! Otherwise no problem at all.

Q1, Q2, Q3, Q9 = 2N5550
Q4 = MJE350
Q5 = MJE15030
Q6 = MJE15031

Outputstage transistors = 2 pairs of 2SA12116/2SC2922 (each with a 0,1R emitter resistor)

R9, R10 = 3k3

Q4: Needs a small heatsink
Q5, Q6 : Need a small heatsink

Q9 mounted (glued) at the top of Q5 to create a stable bias current.


/Freddie
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Old 18th June 2003, 10:47 PM   #7
blmn is offline blmn  Brazil
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Freddie

Quote:
The collector resistors of the CFP outputstage is 0,47 ohms.
7A and 0,47R means that I will lose over 3V across those resistors.

Perhaps the output power is reasonable after all.
Think I will reduce those resistor to 0,15R.

Anyone else measured the output power of their ESP 3A?
I think you have to consider the voltage drop on the 0,47R is a function of the peak current (near 4,7v over the resistor). You have 49.6Vcc at full load minus 4,7v. Since you have 39.9v peak and 44.9 available to swing I think you´re reaching a reasonable power level in this case. Did you measure the Vcc at full load using the scope or the DMM?
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Old 19th June 2003, 07:38 AM   #8
Freddie is offline Freddie  Sweden
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Quote:
I think you have to consider the voltage drop on the 0,47R is a function of the peak current (near 4,7v over the resistor). You have 49.6Vcc at full load minus 4,7v. Since you have 39.9v peak and 44.9 available to swing I think you´re reaching a reasonable power level in this case. Did you measure the Vcc at full load using the scope or the DMM?
I measured Vcc at full load using a DMM. But I think I will reduce the value of the 0,47R resistor, perhaps to 0R1.

/Freddie
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Old 14th December 2003, 08:26 AM   #9
MaXiZ is offline MaXiZ  Italy
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Excuse me... from which u say the schematic have modifyed... how? ANd is there a substitute to MJ? Here in italy are very EXPENSIVE (the 2sc too... 17€!)
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Old 14th December 2003, 11:13 AM   #10
Freddie is offline Freddie  Sweden
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Excuse me... from which u say the schematic have modifyed... how? ANd is there a substitute to MJ? Here in italy are very EXPENSIVE (the 2sc too... 17€!)
I haven't got the schematic left, but here are the changes I've done to the P3A amp. Yes the 2SA1216/2SC2922 are expensive. Try MJ15003/15004, they are cheap.

/Freddie


-----------------------------------------------------
Powersupply/channel:

One 500VA toroid transformer
Two 47000uF 63V RIFA capacitors.

Amplifier:

Q1, Q2, Q3, Q9 = 2N5550
Q4 = MJE 350
Q5, Q6 = MJE1503x

I use two pairs of Sanken 2SA1216/2SC299 transistors each with a 0R1 5W emitter resistor.

R9, R10 = 3k3

Q4, Q5 and Q6 need to have small heatsinks.

I also placed Q9 (Vbe multiplier) at the top of Q5 to have a very stable bias current.
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