30W amp ? P3A, DoGC, OPA549, P101 ? - diyAudio
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Old 17th December 2005, 07:49 AM   #1
00940 is offline 00940  Belgium
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Default 30W amp ? P3A, DoGC, OPA549, P101 ?

I need a rather simple (but not dead simple) around 30W amp. Class AB, I've got a 225VA transformer with dual 21vac secondaries and heatsinks. Load range from 4 to 8 ohms.

Among possible choices there are the ESP project 3A and 101, the death of gainclone new thread or simply a chop amp. I'd prefer something on the punchy side, it's to wake up a pair of wharfedale diamond 8.1 on a small room.
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Old 17th December 2005, 09:14 AM   #2
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Hi 00940,

I can speak of the P3A. It is a reasonably simple amplifier to build. Many in the DIY Audio community have built it and have been very happy. I enjoy mine immensely. I am not sure it will wake up a pair of Wharfdale Diamond 8.1 (86db aren't they?) but the amp is 60W into 8 ohms. I am using Floorstanders in a 20Ft+ room and it fills it with sound with no stress at all. Quite cheap to build too. I am currently building the P101 (on and off efforts I'm afraid), this I think is more expensive.

Hope this is helpful.

Cheers.

Brownlow
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Old 17th December 2005, 09:15 AM   #3
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The perfect power supply for my project - DoGC, for 4 ohms load
Today, but later I'll post the PCB and component location in " the neighbouring" thread...
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Old 17th December 2005, 10:10 AM   #4
rabbitz is offline rabbitz  Australia
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Don't disregard the chip amps like the LM3875 and LM3886 as they can surprise.... they did for me anyway and made me throw my P3A out. That power supply is ideal for those.

http://www.chipamp.com/

http://www.specializedkits.com/
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Old 17th December 2005, 10:46 AM   #5
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The chip amps are class AB amps and sounds "ordinary"...
muddy midranges, "weaky" and "rugged" highs...
"blurred" bass...
Feedforward Error Correction is the better way to achieve clear and natural sound... and 3D...an idea ( may be a few ) below Solid State SE class A...
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Old 17th December 2005, 10:46 AM   #6
MikeB is offline MikeB  Germany
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The symasym might also be a good choice for you ? (An idea above SS SE ClassA... kidding...)

Mike
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Old 17th December 2005, 11:10 AM   #7
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Quote:
Originally posted by rabbitz
Don't disregard the chip amps like the LM3875 and LM3886 as they can surprise.... they did for me anyway and made me throw my P3A out. That power supply is ideal for those.
Interesting, I found the opposite but there wasn't much in it either way. Out of curosity, what output transistors did you use? I have a feeling that there might be a reasonably wide range of performance with P3As depending on component choices.

Anyway, either would be good choices IMHO. The chipamp kits rabbitz pointed out would definitely be easier.

regards
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Old 17th December 2005, 11:27 AM   #8
jmateus is offline jmateus  United States
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Yes, the Symasym 5 would be a good, a very good solution.

I had a chance to build the 3875, 3886 and finally the 4780 and
none of them satisfied me. For this latest one I even bought
the board set from Brian and, frankly, I didn't even try to complete
it as disapointed I was with the sound.

However, in my quest for a good amplifier I found the Symasym,
and yes, this is an amplifier anybody can be proud of.
A winner!
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Old 17th December 2005, 11:45 AM   #9
rabbitz is offline rabbitz  Australia
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Quote:
Originally posted by Greg Erskine


Interesting, I found the opposite but there wasn't much in it either way. Out of curosity, what output transistors did you use? I have a feeling that there might be a reasonably wide range of performance with P3As depending on component choices.
regards
Hi Greg

One P3A on the newer PCBs using MJL21193/4 as well as better quality components through out, using a Harbuch 300VA 25+25, 4 x 4000uF caps and was beaten easily by the other P3A on older PCBs using TIP3055/2955 with very average components, using a Altronics 80VA 18+18, 2 x 5600uF caps. Figure that out.

I preferred the P101 over the P3A, but of course personal tastes come into it, but my AKSA 55N+ is still the favourite.

From my experience, the chipamps I've built (LM3875, LM4780) are very system dependant, but partnered with the right speakers, they shine.... wrong speakers (load????) and very ordinary.

Cheers
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Old 17th December 2005, 01:10 PM   #10
lineup is offline lineup  Sweden
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This one 25 Watt / 8 Ohm amplifier I want to build.
Maybe I'll come around to it, some time.

Click the image to open in full size.

Easy to find components:
- BC560C, BD139, BD140 and IRF530/IRF9530
- Trafo ( 1 channel I think ) 2x25V 120 VA
- Output bias recommended: 100mA

It is nothing spectacular, but as far as I can judge, basically a good amplifier
with very nice and low distortion figures.


RED Free Circuit Designs
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