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Old 8th September 2002, 07:18 PM   #11
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Default to hugobross

To drive a four ohm load continuesly it will problably not be enough, but if you have a good amount of caps, I'm sure the result will be ok.

The project I'm making at the moment the unloaded rails are +-55 V, but they drop to about 45 at 200 W into 4 ohms.

There is a thread with pictures here.

http://diyaudio.com/forums/showthrea...&threadid=4091

Hope it will work out for you

I still think seperate bridges will be best

\Jens
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Old 9th September 2002, 11:28 AM   #12
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thanks,

Jens, your amp looks wonderful!!!

first, I will make 2 boards of the prototype I've build recently. Later I will add two extra boards (and extra caps) for bridging.

I guess the amp will weight about 35 kg, due to the 8 transformers. I know it's heavy, but I've got to clean up all the components laying around here

best regards,

HB.
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Old 9th September 2002, 11:33 AM   #13
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Quote:
Originally posted by kristijan-k
Hello,


Here is an example of one other way.

(two bridges)

Best regards,
Kristijan Kljucaric
http://web.vip.hr/pcb-design.vip
This is better imho. This way you can make two completely separated psus. You can then run the two returns (ground points) to a star point together with the speaker return. Makes the grounding (and sound) cleaner for the same price.

Jan Didden
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Old 9th September 2002, 01:39 PM   #14
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Default hugobross

Hi

Build a "bank of caps" also.......

Have you measured the diffenence af your transformers ?

\Jens

Pic is my "bank" 24 * 10 mF 80 V
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File Type: jpg caps.jpg (58.2 KB, 220 views)
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Old 9th September 2002, 01:50 PM   #15
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Jens,

It's a long time ago i did that measurement, but I remember the differences where very low.

nice picture, but I would never use that kind of connectors anymore you use over there, it's good to make once a connenction, otherwise your traces on the pcb will suffer!!

HB.
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Old 9th September 2002, 01:56 PM   #16
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Default hugobross

Not sure I know ehat you mean,

Are the connectors bad ? og bad for the PCB ?

\Jens
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Old 9th September 2002, 02:05 PM   #17
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I've used the same type of connectors for the input of DC-controlled dimmers in my own made light-controller (a previous project of mine - looks pretty nice and works very well; I'll post it in the future...). I think I rewired the dimmers about 4 times, and I had lot's of traces broken (the pcb's were of high quality), or solder pins that are 'pulled' out the solder tin and so making bad contacts. The problem with this connectors is that only the pins hold the connector to the pcb and not some extra screws or something else. So each time you turn on the screws you're pcb or solder tin suffers a lot!!!

best regards,

HB.
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Old 10th September 2002, 12:33 AM   #18
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Default Talking about PSUs....

Do you believe that using one bridge/polarity is better than a single bridge? Does this solves the problem with the correct phase on the plug? I'm all ears......
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Old 10th September 2002, 03:59 AM   #19
mbroker is offline mbroker  United States
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Default LeachAmp power output

Quote:
Originally posted by skaara
+-40v = 90w
+-58v = 120w
Isnt that big difference? Ive seen some other amps that can provide 160-180w at this voltage, why is this one an exception?
There's a couple reasons, and I suspect that this is more of a norm than an exception.

The first is PSU droop under load. The actual rail voltages are closer to +-50VDC under full load. The second is the Triple-Darlington output stage, which drops about 3.5V from predriver input to speaker output at full power into 8 ohms. The third is the decoupling of the class A stages through the 82ohm resistors (R32 and R33). The voltage drop across these resistors is about 1V. Next is the 390 (360 plus 30) ohm emitter resistors on the voltage gain (Q12 and Q13), lowering the voltage another ~1.5V. Add it all up and you get about a 6V drop, or essentially 44Vpeak output with "perfect" +-50VDC rails. 44Vpeak = 121W/8, so 125W/8 is about correct for the LeachAmp.

Cheers,

Mark Broker
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Old 11th September 2002, 08:40 AM   #20
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Default what about fusing the whole thing?

Hi again,

I've just mounted all the transformers and the caps in my case, it weights heavy!!
But how do I have to fuse the whole thing(1 psu with 4 transformers / channel), I was thinking about the normal way, two fuses (pos. and negative rail) and one fuse at the primary. But will that primary fuse provide enough protection when one of the 4 (or 2)bridges is shorted (because that one is rated at the current of four transformers).
Or can I place the rail fuses before the rectifiers? probably not because of the turn on current of the psu...
or maybe using more primary fuses?

HB.
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