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PostPosted: 02 Dec 2010, 07:35 
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Joined: 02 Dec 2010, 05:33
Posts: 5
Location: Swindon, England
Hi from a noob :D
Fascinating thread...reminds me of the class A amp I built nearly 20 years ago at college. I think I am going to have a go at building this one as my starter project. The only decision is what to use as a PSU, and the pre-amp stage or perhaps I should drive it from my Yamaha AVR amp line level outputs....


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PostPosted: 02 Dec 2010, 10:44 
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Joined: 24 Jun 2010, 00:48
Posts: 788
Location: Christchurch, NZ
Hi,

You can try Rod's P37A discrete SS preamp. Very simple and mates nicely with the P3A. If you need more gain, I think Nelson Pass's BoZwill be awesome (refer to post #2).

For PS, I highly recommend this diagram. It is taken from the DX Blame ES amplifier designed by Carlos Mergulhao. Exceptionally quiet with good performance. I used it with the Blame ES and it resulted in the quietest amp ever.

Have fun with the P3A build. You won't regret it.
(assuming you are not into overly warm and relaxing, lush sound :mrgreen: )

This P3A will breathe life into the music. Brace yourself for the goosebumps !!! ;)

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Dinesh

Some of my diy audio projects:


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PostPosted: 02 Dec 2010, 11:09 
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Joined: 02 Dec 2010, 05:33
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Location: Swindon, England
hehehe, decisions, decisions..... :mrgreen:


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PostPosted: 03 Dec 2010, 03:52 
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Joined: 24 Jun 2010, 00:48
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Location: Christchurch, NZ
Woops, sorry I forgot to add the PS schematics !
Anyway here it is !


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Dinesh

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PostPosted: 03 Dec 2010, 04:04 
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Joined: 02 Dec 2010, 05:33
Posts: 5
Location: Swindon, England
Haha, I thought I was being dumb when I read the original schematic and thought, that's a lovely amp design, but looks doesn't look very much like a PSU!


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PostPosted: 01 Jan 2011, 20:11 
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Joined: 30 Dec 2010, 00:07
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Hi Dinesh,
Loved your tales about the P3A. I built one of these many years ago, with help from and audio friend of mine (I am novice with electronics) and I still use it today.

I note that the PB layout you have is slightly different to mine, as it has a couple of electrolytic caps near the fuses, as shown in the figure. Any idea what these are for? What are their details/ratings and where do they connect as I might try and retrofit these to see if they make an audible difference (or even start another P3A project, with help from my mate).

Skittle


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PostPosted: 02 Jan 2011, 11:46 
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Location: Christchurch, NZ
Hi Skittle,

Those caps, C- and C+, are power supply bypass caps, which connect from either side of the voltage rails to ground. They are like small tanks to store charge which are located much closer to the PCB as compared to the main power supply caps. The addition of these should improve "transient speed".

Each cap is then bypassed by a 0.1uF MKT snubber.

The other change is the removal of the SIM connectors and bridging resistors.

You can solder each cap directly to the fuse holder's metal body or you can add those caps on the underside of the circuit board. Be wary of the polarity.

Am still loving the P3A. Still hasn't left the main listening area =)
One more thing : I never cringe anymore when turning the amp on as there is no pop at all.
Even on turn off there is only a very soft "click" sound.

What are your opinions/thoughts of the amp's sound ?

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Dinesh

Some of my diy audio projects:


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PostPosted: 02 Jan 2011, 20:54 
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Joined: 30 Dec 2010, 00:07
Posts: 4
Hi Dinesh,

thanks for that. They look like 100uF caps, is that right?

I have been more than satisfied with the amp, but haven't had much to compare it to. My audiophile mate said it was a very good amp, and I took his word for it. I am thinking of building another one for the "shed" but will try and etch my own boards using my original as a template, However, I want to incorporate any changes that have been made over the years, hence my questions about the caps.

Skittle


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PostPosted: 02 Jan 2011, 23:20 
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Joined: 24 Jun 2010, 00:48
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Location: Christchurch, NZ
Hi,

Yes they are 100uF/63V according to Rod's documentation.
I used 35V ones as my power supply is only outputting 25V DC.

Do start a new build thread =)

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Dinesh

Some of my diy audio projects:


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PostPosted: 29 Apr 2011, 05:15 
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Joined: 24 Jun 2010, 00:48
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Location: Christchurch, NZ
Having read a lot of excellent SS amp designs on diyaudio, I have decided to stick with a tried and tested successful amp - P3A. This will be a very high end build and serve as a reference amplifier for my small 2 way bookshelf speakers and is pure dual mono in a stereo chassis. All the parts chosen are of the highest reliability and quality I can afford.

300VA 25V X2 encapsulated toriodal transformer from Rs-Components (NZ$140 each)
4X 22,000uF 63V Evox Rifa PEH 169 electrolytic capacitors
All transistors including output transistors (2SC5200/2SA1943) matched tightly -$100 total
16X 8A 600V Vishay ultra high speed soft recovery diodes -$2 each
Chassis 3U type from modushop (with external heatsinks on sides)

Soft start and speaker protectors will be used - Both of which from AussieAmplifiers.

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Dinesh

Some of my diy audio projects:


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