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Old 24th April 2003, 10:33 PM   #1
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Exclamation Elliott Sound - "The Project 3A"

Now i dont go on risk..... i will go on safe !!
i will build the The Project 3A with the parts :

and i want to ask... if somebody build this amp before.... ?....

and what the real RMS power that i can get in 4 ohm (35-40V -/+)
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Old 25th April 2003, 02:41 AM   #2
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I'm building this DJ, but it'll be a while. I'll post pics and stuff when I'm done. But I know a lot of guys have done this before. Hopefully someone else can give you exact #'s.

-Matthew K. Olson
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Old 25th April 2003, 06:14 AM   #3
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I just finished the latest evo of my P3A yesterday. As always, no digicam available, so still no pics...

I used MJ15003/15004 and BD139/140 as transistors.

I exchanged C2 (220pF) ceramics for Mica (Mica way better than anything else), C7, C+ and C- (100 nF MKT) for MKP-type, C1 for 4.7 uF MKP and C4, C6 (100pF ceramic) for FKP

No other changes. I used a semi mono supply design (one big toroid - 500VA 30-0-30 - and two seperate supply boards), and also split the original P3A board in half. For rectifying I used four MUR860 disodes, and for supply caps I used 2 * 10.000 uF BHC SlitFoil for each channel, so 40.000 uF and 8 diodes at all (and R. Elliot himself has underlined it time and again that more capacitance really would be a waste of money... he even told me to use a 300VA transformer instead of the 500VA one, but since that only costs 8€ more than the 300VA type...)

I heatsinked (very small cute TO220 sinks) all the BD transistors, so that in spite of Elliots recommendations I should be able to run the amp into 4 ohms with the 42 V supply voltage I use...

Well, how does it sound? I am not an expert at describing sounds, and the only stuff to compare it with ( ) are a GainClone (OPA548) and a LCAudio End Millenium module...

I cannot really spot a lot of differences between the GC and the P3A, but of course P3A seems more powerful when it comes to high volumes (actually my speakers are 6 ohms), and does not clip as fast (but I only can get all amps into clipping by adding a pre-amp, normally I am running all my amps without a pre-amp)

No noise (only some hissing from the tweeter which gets unhearable when more than 10 cm away from the tweeter), and overall a neutral, if slightly warm sound (a lot warmer than the LCAudio End Millenium, which must be the most neutral amplifier ever build, therefore I normally only use it as monoblock for my subwoofer).

Overall I must have spent about 140 € (including everything, also case and a vandalism proof push button and a solid state Finder relais). About 40 - 50 € more than for my GC, but since now I like the "massive" appearance of the P3A (19" case) more than the very small GC, and I also plan to use 83dB speakers in the future, for which the GC would be a little underpowered...



PS: As for power, I estimate (no way of measuring it) my amp at about 90 - 100W per channel into 8 ohms. Take a look at Anidin's site, there is a power calculator for the P3A...
P3A Construction Guide
A Sacrifice For Freedom
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Old 25th April 2003, 12:21 PM   #4
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With 60V rails I get about 180W RMS in 8 ohm. I'm using the MJL3281A / MJL1302A pair.
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Old 25th April 2003, 01:51 PM   #5
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thamks for all to the answers.....

sayang001..... how u can get 180W RMS with 60+/- and in the ESP site thay say that 90W RMS MAX on 8 ohm speakers.....
u are change something ? if it is yes..... so what u change..?
u can post your circuit ?
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Old 25th April 2003, 01:54 PM   #6
tiroth is offline tiroth  United States
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60V rails means +/-60V.
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Old 25th April 2003, 01:57 PM   #7
sajti is offline sajti  Hungary
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I recommend to use more output transistors, for +/-60V rails, to get better safety.

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Old 25th April 2003, 02:09 PM   #8
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if i build this amp with my part...... and each amp us in 6 O/P devices...... of 2sc5200/a1943......how much power i can get in 4 ohm ? and 8 ohm ? ( with +/- 68v ) and i need to change something in the circuit to make him work in this high volt....?
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Old 25th April 2003, 02:20 PM   #9
sajti is offline sajti  Hungary
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Hi DJ,

this is not very esay to increase the output power of any amplifier. If You just add some more output devices it can results oscillation, which can kill Your transisitors. If You connect together more power transistors You have to use some small resistors to equal the current flow thru the devices.
If You want to build high power amplifier just go, and search for high power amplifier schematics!

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Old 25th April 2003, 02:22 PM   #10
sajti is offline sajti  Hungary
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One more problem:

BC640 can handle 80V only. If You use this part as Q4, the maximum supply voltage +/-40V!

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