ESP 3A output power at 4 ohms load - Page 2 - diyAudio
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Old 14th December 2003, 02:10 PM   #11
MaXiZ is offline MaXiZ  Italy
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ok for the MJ15003 but how many power can i've from it? And if i change the final output with another MJ/MJE/MJL should i need to change the schematic?
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Old 14th December 2003, 03:51 PM   #12
Freddie is offline Freddie  Sweden
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MaXiZ,

Why don't you build the P3A amplifier as it is. With no modifications at all? And buy PCB from Rod Elliot.
The P3A is a good amplifier.

/Freddie
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Old 14th December 2003, 05:58 PM   #13
MaXiZ is offline MaXiZ  Italy
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becouse i simply need more power! And this power amp seems the easiest to build and modify!
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Old 14th December 2003, 06:10 PM   #14
sam9 is offline sam9  United States
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I suspect the 200W figure @ 4-ohms is rather close to SOA envelope for the output devices. If it were me, I would go to three pairs if the space to mount them were available. This is partly a personal preference of mine - I like my equipmen (audio, auutomotive or comutational) to run well with in limits rather than to push them to the max.
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Old 14th December 2003, 07:28 PM   #15
MaXiZ is offline MaXiZ  Italy
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Quote:
is rather close to SOA envelope
What mean SOA?
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Old 14th December 2003, 08:13 PM   #16
Freddie is offline Freddie  Sweden
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Quote:
What mean SOA?
SOA = Safe Operating Area

A good article can be found here:
http://www.sound.westhost.com/soa.htm

/Freddie
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Old 14th December 2003, 11:53 PM   #17
djk is offline djk
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"I suspect the 200W figure @ 4-ohms is rather close to SOA envelope for the output devices. If it were me, I would go to three pairs if the space to mount them were available. This is partly a personal preference of mine - I like my equipmen (audio, auutomotive or comutational) to run well with in limits rather than to push them to the max."

Use TO3 outputs for best SOA. Even the old MJ15003/04 have 250W safe area at 50V, and de-rate to zero at 200*C junction.

Plastic parts are a joke at high voltage, high temperature, and high current.

Speed?

Yeah, those plastic 30Mhz outputs are fast at low currents.

But this ESP3A example here is a good case in point: on program material the collector current at full output will be on the order of 12A peak, 6A per device (48V into 4R).

At 6A the speed of the 30Mhz plastic NPNs drops to about 3Mhz, about the same as the older MJ15022, and not as fast as the newer MJ21194 (the PNPs are all faster).

A quick price check at:

http://www.future-active.com/Comerge...ure?cmd=search

Shows the MJ21193/94 to be USD$1.95 each.
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Old 5th January 2004, 05:02 PM   #18
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Quote:
Plastic parts are a joke at high voltage, high temperature, and high current.
Idon't agree with this. Plastic packages suffer in relation to metal cans due to lack of contact surface area for heat dissipation but it's still silicon inside.

Metal cans like the mj15003/04's are expensive compared to plastics so paralleling of the plastic makes them much more appealing.

As for speed Fairchild's fjl4315 (to-264) are rated at 30Mhz @ 1a 5v's and have a 10th of a second repetitive peak of 350watts.
And 30a 10ms collector peak.

Mj15003/04 are rated at 2mhz @ .5a 10v's with a collector current peak of 30a for 5ms. Try matching a comp pair of mj's by there GBP, your head will start to spin. The mj's are more heat tolerant but who wants there heat sink to be almost 400 degrees fahrenheit.

And with plastics ease of mounting and heat sink considerations, I"ll have plastic please.
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Old 5th January 2004, 05:53 PM   #19
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This is an output module, single channell, I'm building. These tip2955/3055 are pretty dated but cheap. I'm shooting for 200~250w's a channel into 4ohms. I'll post the complete, of course, when I'm done.
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Old 5th January 2004, 07:02 PM   #20
sam9 is offline sam9  United States
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I think you will find you can get pretty good results with tip2955/3055 if you under-rate them, i.e., use more than you really need so as to keep them well within their SOA. I did a simulation using Onsemi models that seemed to indicate that if you used enough so that the worst case emmitter-collector current stayed below 2/3 to 1/2 the max rating, the noise and distortion figures would be in the same ball park as much newer and exotic devices. Since these are relatively small and cheap your approach could be quite sensible.
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