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PostPosted: 29 Apr 2011, 05:43 
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Joined: 24 Jun 2010, 00:48
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Location: Christchurch, NZ
Am undecided whether to go for 4X standard 35A 400V bridge rectifiers or discrete ones.
Any suggestions ?

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PostPosted: 05 May 2011, 03:21 
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Joined: 27 Apr 2011, 22:33
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Location: China
welldone,i would do one the same.

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PostPosted: 05 May 2011, 19:27 
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Location: Christchurch, NZ
Inhaos wrote:
welldone,i would do one the same.

What do you mean?
What about the diode selections?

Since I will be using a soft start circuit, the filter caps and diodes will be subject to very little stress, so would the use of high speed diodes do justice?

The other option is just to mount 4X 50A 600V bridge rectifiers to the chassis.

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PostPosted: 06 May 2011, 16:37 
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Joined: 14 Oct 2008, 17:35
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Location: Dartmouth, Nova Scotia
I would recommend using 2x large high current bridge rectifiers if you have a transformer with dual windings, one bridge for the positive rail and the other bridge rectifier for the negative.

I personally don't see much advantage in using fast diodes when using 35-50 amp bridge rectifiers. ;)

Also, my P3A sounds really good using solid copper wire for the power supply rails, 80 farads of supply caps and only running 20 volt rails too! :blush:

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My Mini 12AU7 Tube Preamp, Pioneer SX-D7000, JVC XL-V221BK, JBL L80T, DCM TF700


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PostPosted: 06 May 2011, 17:15 
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Joined: 08 May 2009, 08:20
Posts: 918
Location: Duesseldorf, Germany
Hi Dinesh,

usually i would also use the high current 35A bridge rectifiers, but it sounds like you plan a really BIG and fast power supply.
As you want so, i think to prefer the Vishay 8A Freds from your link (or the MUR860). I took a look onto the datasheet and
it reads very nice :smoking:.

With your softstart it can't go wrong as the softstart allows to charge the caps slowly first.

Without softstart i would prefer the 35A bridges(!) as they have the capability to handle higher current peaks.
4 x 22000uF is a lot and at the first moment of switching on the power they behave like a short circuit to the transformer and the rectifiers.

High speed rectifiers provide a faster reactance, which will help to keep the caps charged faster.

Have fun ;-).

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Some of my projects: TDA2050 Chip Amp, the LM3886 Gainclone Thread and the Szekeres Headamp Thread.


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PostPosted: 06 May 2011, 18:50 
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Joined: 24 Jun 2010, 00:48
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Location: Christchurch, NZ
Thanks guys. Guess I will have to try both solutions as I have already ordered the 35A bridge rectifiers.

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PostPosted: 20 May 2011, 07:55 
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Joined: 24 Jun 2010, 00:48
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Location: Christchurch, NZ
With most of the parts collected, a mock set up on MDF shows the layout which will be fitted into a Modushop 4U case in the future.

The RIFA PEH 169 caps are massive. Dia 70mm by 105mm long excluding the mounting screw. The screw end should end up fixed to the bottom of the chassis. This helps to dissipate any heat stored up in the caps - highly unlikely for a class 100W class AB design.

Soft start circuit resides between the two 300VA encapculated toriodal transformers.
35A 400V Vishay bridge rectifiers in the middle of caps and tranny.

The P3A modules are resting on the 0.33 deg/celcius rated heatsinks.

Finally at the back, two speaker protection modules for safety against DC in case of a fault.

Components used on the P3A modules were ordered from Farnell NZ.
Wima caps / Panasonic FC electros / matched BD139/140, 2SC5200/2SA1928 and BC546.
Vishay 5W 3% 0.33R metal film emitter resistors.


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PostPosted: 20 May 2011, 17:17 
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Joined: 19 Jun 2010, 17:08
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Hi Dinesh,

what pre amp do you use with the P3A? did you use same pre to test other ZCA/Aussie?

I built aussie nxv300 and later sold it. I will be building ZCA soon and also finished buying parts for
ESP P101.

do you think P3A sounds better because it is a different sound from others or it is really that good?

are you using stock BJT parts or different type?

I'm glad you have found success with 'THE' amp to keep :thumbsup:


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PostPosted: 21 May 2011, 01:24 
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Joined: 24 Jun 2010, 00:48
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Location: Christchurch, NZ
Hi,

I used the Dispre 2 Jfet preamp, as well as the P37A DoZ preamp to drive the P3A build when I was in Malaysia. The P37A is extremely good for it's overall costs, but the Dispre 2 is up a by another notch.

Now that I am in New Zealand, I am rebuilding the P3A with higher quality parts and I have used different output transistors - 2SC5200/2SA1943. Previously I used MJL21193/94. The preamp used to drive my new build is the PRE3 preamp.

I did not use a preamp for the ZCA as it had adequate gain for the speakers. (90dB)

I do not have any other amps or preamps to compare with at this stage, so I will have to use my past listening experience to judge the sound.

I like the P3A for it has the exact sound I am looking for - upfront staging, wide and deep soundstage, non-overly damped bass response and vocal clarity. The highs are not sharp and does not bring any fatigue. It is clean but not too dry - perfect IMO.

Hope to have the power supply section up and running tomorrow.

How did you find the NXv300 ?
May I ask why you sold it?

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PostPosted: 21 May 2011, 01:40 
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Joined: 19 Jun 2010, 17:08
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Hi Dinesh,

I built mono block nxv300's. It sounded great for movies but for music, IMHO, it was just okay.
It has great reviews and praises but just not for me. I sold it at big loss but live and learn.

I have dispre 2 I put up for sale in the classified. That one too, I did not care for. just missing something for me,
maybe it's too clinical and missing warmth. it's been awhile so I may go back and try again if I don't sell it.

I'm driving Maggie 1.6QR so maybe I'm too picky. I've built aleph mini/J/F5/P1.7 so have gone through many diy amps.

ZCA build will be driving small Monitor Audio RX1 bookshelf.

I think you have matched your system very well now, so that is really good news.


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