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Old 7th December 2008, 03:56 AM   #1
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Default running quad303 with a pair of MJ15004

Hi,

I have got boards for the quad303 that can run with NPN-NPN or NPN-PNP pairs. But I got myself a bunch of MJ15004 lying around for years. I would like to see if the quad303 circuit can be modified to run with PNP-PNP and what has to be done to the circuit. Just want to use what is at hand instead of buying new stuff. BTW what is the transformer secondary output voltage with the original psu unit in place? w/o the original psu unit, I can use 48V which comes out to ~67vDC after rectification, right?

information for NPN-PNP outputs is here :
http://www.net-audio.co.uk/quad303upgrade.html

Tks
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Old 13th December 2008, 02:33 PM   #2
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Hi

It may not be a good idea to do so, but it should be feasible, isn't it?

Can someone give some ideas please?
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Old 19th December 2008, 10:35 PM   #3
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So, Its a mass destructive weapon that I am planning?
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Old 23rd January 2009, 12:49 AM   #4
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Any helping hand at all?
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Old 15th February 2009, 04:14 AM   #5
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OK, I had made a wild guess. Please point out if I am wrong or any other change I might have to make to get it work. Thank you for helping or just looking.
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Old 15th February 2009, 08:54 AM   #6
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Well, from a quick glance I see nothing wrong; however I don't understand why the 2 halfes of the outputstage have different gains and wether that is normal for quads.

Anyway, you could try that, even if I generally would buy proper parts. Ok outputs cost money but in relation to all the other stuff that you need these costs are rather small

~67V is correct; ain't that too high for a quad? That's about 300W into 8 ohm. I've read that the Quad303 is more like 50W into 8 ohm?

If you use such high rails for a 50W amp, it will go up in smoke.

Please double check that your circuit is suited for such high rails!!

And be very cautious as that rail can really bite.

Have fun, Hannes
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Old 15th February 2009, 09:35 AM   #7
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Tks for looking at the supply voltage problem. But the original circuits says 0-67v not +-67v. So do I get it right? Tks.
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Old 15th February 2009, 10:27 AM   #8
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Google is your friend.

There is a LOT of info on the Q303 on the net.

You'll find the Service manual, a description of converting the NPN setup to NPN-PNP, using different transistors and much more.

By memory: the rails are that high because the boards are in series with the PS.

succes, MArco
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Old 15th February 2009, 11:39 AM   #9
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bigpanda,
another possibility
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Old 19th February 2009, 12:37 AM   #10
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Hi Marco,

Sure there is a lot of info available but I just can't find what I am after. I may be the first crazy one to try a PNP-PNP output config, and I think is worth trying.
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