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PostPosted: 21 May 2011, 11:57 
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Hi Lynx,

Im not sure if P3A can drive maggies, but you may be very happy with P37A + P3A combo.

I like my ZCA but it is quite low in power, even for 90dB speakers. Might struggle driving your bookshelves.

My setup shown here will not only be used for the P3A, but am going to try many more SS amp modules that run on 25V transformers. A couple more will be the Symasym V1.5 and Carlos's DX Blame ST.

Thanks for your thoughts, it shows we all have varied tastes and expectations on what makes a good amp.

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PostPosted: 22 May 2011, 21:00 
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By tonight I will have the power supply and soft start circuit wired up.
Pics to come...

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PostPosted: 22 May 2011, 22:24 
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Amp modules stuffed :mrgreen:

Input caps : Auricap 1.5uF MKP


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PostPosted: 23 May 2011, 04:30 
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Both PS sections wired up with soft start circuit.
Fuse for mains = 2A

PS now is at a steady +/- 36.1V :lildevil:
I did not add any other components to the PS as I feel the caps are good enough to not need additional
snubbers or bleeder resistors.

What do you think? :confused:

Hope to have the drilling done tomorrow for securing the amp modules to the heatsinks.
Can't wait to hear my fav amp again!!! :D


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PostPosted: 24 May 2011, 02:38 
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OMG. I wired up one channel, using computer as a source(no preamp) and was blown away.
Bass thundered, shook the room. Pristine clear vocals and separation. :o
Ahhh finally true high quality sound after months of torturous nothingness.
There is not the slightest hiss from the tweeter.

Akon's "I wanna f**k you" song deep bass resonates through the room though my $100 2nd hand speaker (Goodmans XB35). The sound eats up my Wharfedale Diamond 8.1s for lunch.
I really wasted $$$ investing in a Wharfedale Sub (Power cube 12'') which simply cannot go as deep as the Goodmans sealed 8''. :bawling: Neither has it the finesse to do so without overloading the room.

The sound is huge and fills the room though one speaker is playing. I cannot imagine if both are on.
Bias is set at 70mA, and DC offset is on the high side for both channels - 88mV and 79mV.
This is clearly a step up from my old P3A. The bass is simply incredible.

My Wharfedale speaker and sub shall be sold immediately !! :lildevil:
I am confident enough to take on Krell or Mark Levinson amps any day! :mrgreen:


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PostPosted: 24 May 2011, 05:52 
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I have two channels hooked up now. DC offset somehow has reduced to 10mV and 12mV for each respective channel. Bias is rock stable at 52mA. I tried listening tests at different bias levels, 25mA, 50mA and 100mA and the treble quality sounds the best at around 50mA.

Heatsinks are a few degrees above ambient temp.

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PostPosted: 24 May 2011, 08:01 
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Pic of 2 channels in operation...


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PostPosted: 25 May 2011, 04:12 
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Hi guys,

I did a test with and without Pavel's PRE 3 preamp and found no difference. I tested mono tracks for an hour doing A/B comparisons with one channel hooked up to the preamp, and the other direct to the P3A with volumes matched equally. My source is a $150 blue ray player. Am rather disappointed and impressed at the same time as the preamp did not add any special tone/signature to the sound though it added plenty of gain - 10X without adding any noise to the whole system. It is like wire with gain. Every other preamp that I have built has added something to the sound - with the exception of Dispre 2 Jfet.
In essence, the preamp is "invisible" as part of the audio chain as it lets the true tone/qualities of the power amp shine though.

I am not sure if I should be happy or disappointed. :bawling:


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PostPosted: 25 May 2011, 12:28 
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Not coloring the sound can be a good thing. But it sounds like you really don't need the gain from the preamp.
Cheers

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PostPosted: 26 May 2011, 02:43 
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Gio,

True, but then I would have to add a pot to the power amp and I'd rather have it on the preamp.

I am hearing much better layering and separation in the music than I ever had with my P3A + Scanspeak speakers back home , and these are Vintage $100 speakers !! Goes to show that the amp can have a very large effect on the sound.

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