running quad303 with a pair of MJ15004

[bigpanda]

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

 

[bigpanda]

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?

 

[bigpanda]

So, Its a mass destructive weapon that I am planning?

 

[bigpanda]

Any helping hand at all?

 

[bigpanda]

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.

 

[h_a]

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

 

[bigpanda]

Tks for looking at the supply voltage problem. But the original circuits says 0-67v not +-67v. So do I get it right? Tks.

 

[deduikertjes]

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

 

[Lumba Ogir]

bigpanda,
another possibility

 

[bigpanda]

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.

 

[deduikertjes]

I may be the first crazy one to try a PNP-PNP output config, and I think is worth trying.

No you'r not the first. I remember I've seen a photograph of such conversion. It showed how to modify the pcb where the trannies are mounted on. If I only could remember where ...

But then: Google is our friend:
see: http://www.net-audio.co.uk/quad303upgrade.html

There it is !

succes, MArco

 

[bigpanda]

Hi,
I have gone thru that article before but it is not exactly what I am after. But the idea could be applied. Will try if I have the board made for that. But recently, I was able to get hold of some 003 only. Like I said, it is definitely fun to try so.

Tks anyway.

 

[vendetta]

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

V-A
Quad303 is Single Supply OTL Power Amp. So 67V Aren't Too High.