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Old 29th January 2010, 07:19 AM   #1251
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Quote:
Originally Posted by martinbls View Post
Well, two things to mention:
- I did not use any input coupling caps, because my dac already has output coupling caps.
- As you can see from the transformer and the heatsinks, this is kind of a low power version. I use a transformer with 2x24V secondaries which gives around +/-34V rail voltage (around 50W per channel at 8 ohms).


placing the rectifier up there is not really a wise thing to go ....to my opinion you should locate the rectifier else were ( distance of the cables is not realy a problem ) and then feed your boards from the capacitor pcb and not the rectifier


regards sakis
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Old 29th January 2010, 09:53 AM   #1252
AndrewT is online now AndrewT  Scotland
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Sakis,
look again.
The transformer feeds the rectifier~&~, the rectifier feeds the ends of the outer copper traces. The centre tap feeds the end of the zero volts trace.
The outputs come from the other ends of the traces with the 4 smoothing caps in between. Effectively the caps feed the power outputs.

I would twist each pair of secondary wires together and then join the zero volts above or to the securing bolt of the rectifier. Then twist the relative sets of +,-,g as triplets to each power amp. This massively reduces loop area and thereby emi fields.
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Old 29th January 2010, 10:00 AM   #1253
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Originally Posted by sakis View Post
placing the rectifier up there is not really a wise thing to go ....to my opinion you should locate the rectifier else were ( distance of the cables is not realy a problem ) and then feed your boards from the capacitor pcb and not the rectifier


regards sakis
Hi Sakis!

Actually the amp boards ARE fed from the cap pcb! If you have a closer look at the attached picture you can see the wires from the transformer going to the rectifier and the common ground on the left side of the pcb, and the wires from the rectifier (+ and -) are also going to the LEFT side of the pcb, while all wires to the amp boards are going off the pcb from the RIGHT side (I'm always referring to the attached pic). So, the amp boards aren't fed directly from the rectifier but from the pcb AFTER the caps.

I did that because I'm of the same oppinion as you are! Amp boards have to be fed from the caps, not from the rectifier.

Further more the rectifier is isolated from the common ground with a heat conductive pad. The placement is just a matter of limited space and shortest possible cable length.

Regards!
Martin
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Last edited by martinbls; 29th January 2010 at 10:03 AM.
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Old 29th January 2010, 10:01 AM   #1254
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Oops, Andrew was a bit faster here...
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Old 29th January 2010, 10:15 AM   #1255
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the question is not were you get the power from i have seen that you take it from the caps ....my sugestion is regarding mostly the rectifier and having it working exactly on the top of your ground trace .... Ac and noises are too close to smoothing caps ...

Assuming that you take my advice and you relocate rectifier then you still need to get power from caps and not from the rectifier

regards sakis
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Old 29th January 2010, 10:23 AM   #1256
AndrewT is online now AndrewT  Scotland
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Quote:
Originally Posted by martinbls View Post
Further more the rectifier is isolated from the common ground with a heat conductive pad.
the rectifier case is isolated from the diodes.
You can connect the rectifier case direct to chassis or direct to the zero volts trace.
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Old 29th January 2010, 10:33 AM   #1257
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puting the rectifier too close to smoothing caps is bad practice is not question of isolation ..... having Ac cables too close to smoothing caps is also bad practice

Also messing up signal 0 volt with chassis ground is also bad practice at most cases, all professional amps of high levels of power feature ground lift switch not only to cancel ground loops issues but others also
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Old 29th January 2010, 11:16 AM   #1258
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Originally Posted by AndrewT View Post
the rectifier case is isolated from the diodes.
You can connect the rectifier case direct to chassis or direct to the zero volts trace.
Well, I know... ;-)
But I thought it might be a good idea to add a heat conducting pad, even though the diodes might not get warm at all. It's a 15A bridge.
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Old 29th January 2010, 02:11 PM   #1259
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Ok, bridge mounting also caught my attention, but being a picture thread I didnt comment
But now you are at it, bridge mount does look dangerous
If it gets loose and turns just a bit, the bridge housing could touch the neg/pos, and short the rails

Anyway, 15A bridge isnt that much really, I have always used 35A bridge
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Old 29th January 2010, 03:11 PM   #1260
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Originally Posted by martinbls View Post
Hi lanchile!

I already noticed your HUGE tranformer! Nice one ;-)
Btw, I spoke to Anthony before I build mine and he told me that a higher supply rail voltage doesn't give better sonic results, that's why I build mine around this rather small 250VA transformer (Thel Audio) with a total of 40.000uF smoothing capacitance (Panasonic TS-HA). For my speakers the power is more than enough (simple 2-way, 90db sensitivity).

Well, yes, I do like the sound! I also build a LM3875 amp before, and I must say I seem to like the sound of discrete transistors better than the chip sound. Discrete designs to me simply do sound more, well, "real", if you know what I mean.
The nxv200 are really very well made amp modules, and Anthony did an excellent job here. Very well build, very reliable and stable.

I would say I find the sound to be just a tad more on the bright side than on the dark side of neutral. But this is a matter of personal preferences and system synergy. Perhaps I have do to some more work on my dac and/or my speakers...
(Or perhaps I listened far too long to a Naim power amp... ;-)

Or, here is another idea: This was the first time I used those Panasonic TS-HA caps in a power amp ps. Now I wonder if some BC Series 051/056 would have been a better choice?

But I think everything else about the nxv200 amps is top notch!

Regards!
Martin
I am using Mundorf caps 10000uf x4 and I like them very much. and I agree with you about LM3875/LM3886 I do not say these chips sound bad, They sound good but, compared to nxv200 there is no contest!. Anthony has build some of the best amp kits no doubt.
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