Depends. The amp board has 9, but only 7 need populating if you're using the regulators. In fact you can get away with 6 if you don't carry both grounds back to the star ground -- but I wouldn't recommend that for the amp boards.
The regulator boards have 6. Again you can use only 5 if you don't carry both ground back to the star-ground, and it would be less of an issue for the regulator boards.
One stereo set with regulators and "proper" grounding therefore requires 26. 24 with "less pristine" grounding and 22 with "dodgy" grounding.
Cheers,
Jeff.
The regulator boards have 6. Again you can use only 5 if you don't carry both ground back to the star-ground, and it would be less of an issue for the regulator boards.
One stereo set with regulators and "proper" grounding therefore requires 26. 24 with "less pristine" grounding and 22 with "dodgy" grounding.
Cheers,
Jeff.
A few words on one of Naim's quirks: there's no Zobel network on the output, instead relying on the inductance of the speaker cables.
There was some suggestion that Naim did this to sell their own speaker cables. Whether true or not you certainly don't need to use Naim speaker cables... but you DO NEED a minimum inductance in your speaker cables.
The specs of Naim's cables:
The things to note are the inductance and the minimum length. (The minimum length also means don't power up the amp with no speaker cables.)
Nearly any "normal" speaker cable will meet those specs, but some "avant garde" woven cables (such as Kimber Kable) will not. If in doubt, check the inductance specs of the cable.
Cheers,
Jeff.
There was some suggestion that Naim did this to sell their own speaker cables. Whether true or not you certainly don't need to use Naim speaker cables... but you DO NEED a minimum inductance in your speaker cables.
The specs of Naim's cables:
The things to note are the inductance and the minimum length. (The minimum length also means don't power up the amp with no speaker cables.)
Nearly any "normal" speaker cable will meet those specs, but some "avant garde" woven cables (such as Kimber Kable) will not. If in doubt, check the inductance specs of the cable.
Cheers,
Jeff.
It has been fun to watch a GB take place for one of my favorite amplifiers. I have an old Olive era NAP 250 that has undergone some careful modification. It still sounds wonderful, although my First Watt clones are getting a lot more playing time these days.
I also use a Naim XCD2 and NAC 82 in my system. I built a pair of custom power supplies using two of these: NAIM style Full Aluminum preamp Chassis / Power Amplifier Enclosure 430*90*358mm | eBay
This case has plenty of room to hold a pair of 300VA toroidal transformers, which would be my recommendation. The NAP 250 uses its entire case as the heatsink for the regulator and amp boards. The output transistors may be bolted onto thick wall square aluminum tubing to transfer heat to the case.
I also use a Naim XCD2 and NAC 82 in my system. I built a pair of custom power supplies using two of these: NAIM style Full Aluminum preamp Chassis / Power Amplifier Enclosure 430*90*358mm | eBay
This case has plenty of room to hold a pair of 300VA toroidal transformers, which would be my recommendation. The NAP 250 uses its entire case as the heatsink for the regulator and amp boards. The output transistors may be bolted onto thick wall square aluminum tubing to transfer heat to the case.
I've built all my Pass & FirstWatt clones with Toroidy transformers, and they're great.
But I remember in all my Naim trawlings someone recommending a transformer builder in the UK, and that they used the nice matte-black wrappings as the original Naim.
Only now I can't remember who it was, and Google isn't helping me much.
Anyone know of any clues?
Thanks,
Jeff.
But I remember in all my Naim trawlings someone recommending a transformer builder in the UK, and that they used the nice matte-black wrappings as the original Naim.
Only now I can't remember who it was, and Google isn't helping me much.
Anyone know of any clues?
Thanks,
Jeff.
Hi Jeff,
Thanks for the heat sink (spreader) dimensions from Avondale. As they don't supply these any more, I am sure I can find a very similar C section or 90 deg angle aluminium section extrusion to do the job at 5mm thick.
Also looking forward to your inverted regulator BOM and stuffing guide to complete all the documentation required.
Lost track of where you might be up to with the pcb's and the GB.
Received all the original transistors today in the post from Cricklewood in London - great service and very good pricing, original outputs are now exhausted from them though. But for anyone else interested, Donberg in Jeff's homeland do have them in stock - ST Micro.
Also the Mil connectors Jeff has linked in post #17 are very high quality as well - should be absolutely no long term problems with them and very easy to use when testing or trouble shooting.
Cheers,
Gary..
Thanks for the heat sink (spreader) dimensions from Avondale. As they don't supply these any more, I am sure I can find a very similar C section or 90 deg angle aluminium section extrusion to do the job at 5mm thick.
Also looking forward to your inverted regulator BOM and stuffing guide to complete all the documentation required.
Lost track of where you might be up to with the pcb's and the GB.
Received all the original transistors today in the post from Cricklewood in London - great service and very good pricing, original outputs are now exhausted from them though. But for anyone else interested, Donberg in Jeff's homeland do have them in stock - ST Micro.
Also the Mil connectors Jeff has linked in post #17 are very high quality as well - should be absolutely no long term problems with them and very easy to use when testing or trouble shooting.
Cheers,
Gary..
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I did talk to Les about the heat spreaders. He's moved to a CNC machining company who have a 100 piece minimum quantity in order to program the machines. He said they might do a smaller order, but at greater cost (and even the normal cost is more than the cost per board). So probably not cost-effective.
Feck. (That's Irish for... well, you know what it's for.)
The hole spacing is wrong for the TO-3 devices. Not wrong enough so that you couldn't drill them out a bit or bend the leads into them... but wrong enough that I'm not happy with my name on the boards.
So I need to re-run the boards.
I thought about selling the rejects at a reduced price for those interested, but since that would then reduce the quantities for the re-run it doesn't materially help the costings. Worse, I'd still know my name was floating around out there on some dodgy boards, so that's probably a non-starter.
I could also mark them "reject" with a Sharpie and include them as "freebies" when I ship out the new ones. It's possible that would bump the weight over the 500g limit for "large letter", though, and I suspect most of the folks on this GB are beyond needing to practice their soldering. So that one is of dubious value as well.
Or I could just bin them. That's probably the best solution as the cost is already sunk, but it's hard to throw brand new stuff in the bin.
Cheers,
Jeff.
PS: this might mean I also need to redraw the holes on the heat spreader drawing. I haven't checked it yet....
One last thing: I want to double-check nearly ever detail on the board now, so it won't be till next week that I send them back out for production.
The hole spacing is wrong for the TO-3 devices. Not wrong enough so that you couldn't drill them out a bit or bend the leads into them... but wrong enough that I'm not happy with my name on the boards.
So I need to re-run the boards.
I thought about selling the rejects at a reduced price for those interested, but since that would then reduce the quantities for the re-run it doesn't materially help the costings. Worse, I'd still know my name was floating around out there on some dodgy boards, so that's probably a non-starter.
I could also mark them "reject" with a Sharpie and include them as "freebies" when I ship out the new ones. It's possible that would bump the weight over the 500g limit for "large letter", though, and I suspect most of the folks on this GB are beyond needing to practice their soldering. So that one is of dubious value as well.
Or I could just bin them. That's probably the best solution as the cost is already sunk, but it's hard to throw brand new stuff in the bin.
Cheers,
Jeff.
PS: this might mean I also need to redraw the holes on the heat spreader drawing. I haven't checked it yet....
One last thing: I want to double-check nearly ever detail on the board now, so it won't be till next week that I send them back out for production.
Well Jeff, at least you found the error before sending them out, sorry for you as the cost will sink a hole in your budget, but I agree with your thoughts in the post, I am happy to wait on the revised, corrected pcb's - take your time and make sure they are all double checked I suppose.
I will go through the updated documents and print out.
My payment has been sent, thanks.
Cheers,
Gary..
I will go through the updated documents and print out.
My payment has been sent, thanks.
Cheers,
Gary..