vertically mounted NCC200s?

[Mike Hanson]

Depends on the supply rails and how you couple the thermal feedback loop via TR5. What rails did you use MIke?

Post #35 in your link covers some of the considerations.

The transformer was 35-0-35, combined with my slightly high mains, gave ±53VDC. Perhaps if one were running with typical Naim voltages (±38VDC, IIRC), this may not be as much of an issue. Regardless, I will still never trust steel again as a heatsink material.

 

[hammeredklavier]

Yes, that should be quite easy, as you can use a simple sheet of aluminum cut to size, with holes drilled to match those in the side panels. Get it anodized if you want, but given you'll never see it, I wouldn't bother. Also, the anodizing decreases its heat transfer ability slightly.

BTW, I wouldn't recommend this technique for something like an NCC300, as it puts out quite a bit more heat, but it's definitely adequate for a pair of NCC2x0 boards.

Also, try to keep the input end of the NCC board away from the transformer. Take a look at my build pics for some layout ideas.

Thanks, probably the way forward. As I say, I don't remember the ncc200s getting particularly hot so I didn't think carefully enough!

 

[Arkless Electronics]

I've said it before... but personally I wouldn't go above +/- 40V

 

[hammeredklavier]

I would keep it in one box.
The transformer, rectifiers and main smoothing caps need to be physically close. The speaker return should be taken from the power star point i.e. when the main smoothing caps join.

Ok - just having a think about this, for the first time in my life! The transformer and rectifiers are in the same box, so no difference there. I also - feel free to laugh at me! - don't see why it's hard to connect the speaker return to zero on the CAP6s. I'm not sure I see why separate boxes makes that a problem?

I'm not saying you're wrong or even that I'm going to try it, I'm just trying to learn a thing or two!

Alex

 

[hammeredklavier]

Impedance of earth returns for a start

Can you explain a bit further? I'm not sure what you mean. As before, I'm not saying you're wrong, just trying to understand the problems!

 

[Mike Hanson]

Ok - just having a think about this, for the first time in my life! The transformer and rectifiers are in the same box, so no difference there. I also - feel free to laugh at me! - don't see why it's hard to connect the speaker return to zero on the CAP6s. I'm not sure I see why separate boxes makes that a problem?

I'm not saying you're wrong or even that I'm going to try it, I'm just trying to learn a thing or two!

One of the trickiest aspects of amp building is getting the grounds right. It's not just a matter of where they're connected, but also where the wires are physically run. It's very easy to create ground loops resulting in unexpected hum. I had to completely rewire an amp once (along without repositioning various components) to cure this. The differences between the two didn't seem major, but made all the difference in the world.

 

[Arkless Electronics]

/\ yes and not just ground loop hum either! The way the various ground currents interact and produce voltages through Ohm's Law means grounding issues can also result in degraded sound quality, measurable distortion and even a completely unstable amp that blows up in the worst case! It is certainly one of the trickiest aspects of amp building indeed.

Transformers, rectifiers and smoothing caps in PSU case then further huge caps/more Cap6's in amp box would work fine. Take speaker return to Cap6 grounds in amp box.

 

[hammeredklavier]

/\ yes and not just ground loop hum either! The way the various ground currents interact and produce voltages through Ohm's Law means grounding issues can also result in degraded sound quality, measurable distortion and even a completely unstable amp that blows up in the worst case! It is certainly one of the trickiest aspects of amp building indeed.

Transformers, rectifiers and smoothing caps in PSU case then further huge caps/more Cap6's in amp box would work fine. Take speaker return to Cap6 grounds in amp box.

Ok, my skin is thick, you can laugh at me!

Let's look at the actual electrical difference between amplifiers and PSU in one box vs. putting the amplifiers in a separate box.

I put the ncc200s in a box. This box has the signal in, loudspeaker connections (or at least the 'hot' one), and has the power rails coming in from the power supply box, plus the zeros.

You could even connect the speaker return to the power supply box couldn't you! And thus to zero on the cap6s.

I'm sure I'm being a dunce and missing something but the only difference I can see is the length of the wires between the CAP6s and the NCC200s.

As I say, I've never built amp before in my life so I'm sure I've got a lot to learn, and I'm aware of what Mike said about the physical location of the wires etc.

Where have I gone wrong above? I don't see any actual electrical difference.

 

[Arkless Electronics]

Ok, my skin is thick, you can laugh at me!

Let's look at the actual electrical difference between amplifiers and PSU in one box vs. putting the amplifiers in a separate box.

I put the ncc200s in a box. This box has the signal in, loudspeaker connections (or at least the 'hot' one), and has the power rails coming in from the power supply box, plus the zeros.

You could even connect the speaker return to the power supply box couldn't you! And thus to zero on the cap6s.

I'm sure I'm being a dunce and missing something but the only difference I can see is the length of the wires between the CAP6s and the NCC200s.

As I say, I've never built amp before in my life so I'm sure I've got a lot to learn, and I'm aware of what Mike said about the physical location of the wires etc.

Where have I gone wrong above? I don't see any actual electrical difference.

I'm afraid if it seems straightforward then you need to start the thought train again from scratch.... It's the single biggest pitfall known to the amp builder and in some ways more of a PITA than actually designing the amp!!

You need to think of the wires as resistors.... Yes the 0.1 and 0.01 Ohms resistances are critical!

I've been designing amps for decades, as a pro as well as a DIYer, and it still has me pulling my hair out!

Way beyond the scope of this thread (or any thread) to try and fully explain it.

 

[hammeredklavier]

I'm afraid if it seems straightforward then you need to start the thought train again from scratch.... It's the single biggest pitfall known to the amp builder and in some ways more of a PITA than actually designing the amp!!

You need to think of the wires as resistors.... Yes the 0.1 and 0.01 Ohms resistances are critical!

I've been designing amps for decades, as a pro as well as a DIYer, and it still has me pulling my hair out!

Way beyond the scope of this thread (or any thread) to try and fully explain it.

That's fine, as long as I know why it won't work. If the increased impedance on the power rails is why then ok. I'm surprised, but as you can see, amplifier design isn't what I do!

That is the only difference though isn't it? I mean, the connection to the signal, the connection to the speakers, these are exactly the same as a single box. It's purely the additional length of wire required to connect the CAP6s to the NCC200s?

 

[Gervais Cote]

Yeah but Naim amps don't have vents in the bottom... look closely and you'll see the problem.

If it was a solid sheet of metal I'd go for the first layout no messing. Indeed, it's what I originally planned.

I took for granted the enclosure was made of aluminum, not steel. Aluminum is mandatory to dissipate the heat.

 

[hammeredklavier]

I took for granted the enclosure was made of aluminum, not steel. Aluminum is mandatory to dissipate the heat.

Yeah I hadn't got my brain in gear when I ordered the case. I was busy working on something else at the time so just bought one the right size!

I'll probably just buy a proper aluminium one, but I'm intrigued by the technical problems of putting the amplifiers in a separate box now!

 

[Mike Hanson]

That's fine, as long as I know why it won't work. If the increased impedance on the power rails is why then ok. I'm surprised, but as you can see, amplifier design isn't what I do!

That is the only difference though isn't it? I mean, the connection to the signal, the connection to the speakers, these are exactly the same as a single box. It's purely the additional length of wire required to connect the CAP6s to the NCC200s?

Nowhere near that simple! There's also the concept of wire proximity, etc. Keeping bundles of wires tightly bound helps. You also don't want to have any physical (not just electrical) "circles".

Hypothetical example: You have two ground wires going from one place to another. One runs to the left, while the other runs to the right. Both end at the same place, and seem similar from a simplistic electrical connection perspective, but you've just created a circle that could cause electrical oscillations, magnetic fields, etc.

It involves Kirchhoff's circuit laws, and a whole bunch of other stuff that, as Arkless stated is "Way beyond the scope of this thread (or any thread) to try and fully explain it."

 

[Mike Hanson]

I'm intrigued by the technical problems of putting the amplifiers in a separate box now!

You're a curious one, just like me.

I've occasionally considered a design like this. There is a small benefit in getting the transformer away from the amp boards, but with toroids, there isn't much EM leakage. Just having the input end of the transformer is generally sufficient. But if you have the power supply enclosure far away from the amp enclosure, then you're going to lose some benefits of the PS smoothing.

Then you have the hassle of the connectors and cabling between the boxes. It adds extra resistance and is hard to solder.

Instead, if I'm running out of space in the enclosure, I just buy a bigger enclosure.

 

[hammeredklavier]

Nowhere near that simple@ There's also the concept of wire proximity, etc. Keeping bundles of wires tightly bound helps. You also don't want to have any physical (not just electrical) "circles".

Hypothetical example: You have two ground wires going from one place to another. One runs to the left, while the other runs to the right. Both end at the same place, and seem similar from a simplistic electrical connection perspective, but you've just created a circle that could cause electrical oscillations, magnetic fields, etc.

It involves Kirchhoff's circuit laws, and a whole bunch of other stuff that, as Arkless stated is "Way beyond the scope of this thread (or any thread) to try and fully explain it."

Sure, I'm not disputing any of that. What surprises me is that Avondale (for e.g.) aren't far more prescriptive about enclosure sizes, layouts, and precise cable routes! I've just double checked what was on the CD that came with the kit and there's nothing in there about any of this, it just says what should be connected to what.

I'm minded to try it just out of idle curiosity! I don't actually need another amplifier, the point of this exercise was always to try to learn a thing or two and indulge a bit of NCC200 nostalgia!

 

[Mike Hanson]

Sure, I'm not disputing any of that. What surprises me is that Avondale (for e.g.) aren't far more prescriptive about enclosure sizes, layouts, and precise cable routes! I've just double checked what was on the CD that came with the kit and there's nothing in there about any of this, it just says what should be connected to what.

I'm minded to try it just out of idle curiosity! I don't actually need another amplifier, the point of this exercise was always to try to learn a thing or two and indulge a bit of NCC200 nostalgia!

Avondale has three types of customers:

• Those who have Avondale do everything for them.
• Those who buy a pair of NCC2x0 boards to swap into their Naim amps, which benefits from the predetermined cable routing.
• Those who want to build an entire amp for themselves, at which point it's assumed those people are a bit more savvy, and/or want to tinker.

Given the complexity and nuances of wiring and such, one typically would start by copying someone else's layout. If you forge out on your own path, then you need to have some idea of where you're going and why.

I've assembled at least 10 amps myself (every one different than the rest), and I still consider myself a rank amateur. And all I'm doing is connecting the blocks like Lego!

Keep asking questions! After a decade or so, and you may attain my not so lofty stature, and have a comparable treasure trove of cautionary tales.

 

[hammeredklavier]

Avondale has three types of customers:

• Those who have Avondale do everything for them.
• Those who buy a pair of NCC2x0 boards to swap into their Naim amps, which benefits from the predetermined cable routing.
• Those who want to build an entire amp for themselves, at which point it's assumed those people are a bit more savvy, and/or want to tinker.

Given the complexity and nuances of wiring and such, one typically would start by copying someone else's layout. If you forge out on your own path, then you need to have some idea of where you're going and why.

I've assembled at least 10 amps myself (every one different than the rest), and I still consider myself a rank amateur. And all I'm doing is connecting the blocks like Lego!

Keep asking questions! After a decade or so, and you may attain my not so lofty stature, and have a comparable treasure trove of cautionary tales.

I'm quite happy to tinker. As long as I don't get electrocuted or destroy the parts needlessly! As I say, I don't actually need another amplifier.

I know very basically how an amplifier works and I'm used to electrical stuff so I'm unlikely to end up in hospital. I think I'd like to know a lot more about the principles involved in these 'architectural' problems rather than just trial and error bodging though. That said, I seem to remember Les telling me that considerable trial and error went into perfecting his designs!

I don't doubt that Arkless and others are correct and my two box amp would be a disaster, I'm just not completely sure why!

 

[Arkless Electronics]

I'm quite happy to tinker. As long as I don't get electrocuted or destroy the parts needlessly! As I say, I don't actually need another amplifier.

I know very basically how an amplifier works and I'm used to electrical stuff so I'm unlikely to end up in hospital. I think I'd like to know a lot more about the principles involved in these 'architectural' problems rather than just trial and error bodging though. That said, I seem to remember Les telling me that considerable trial and error went into perfecting his designs!

I don't doubt that Arkless and others are correct and my two box amp would be a disaster, I'm just not completely sure why!

If you make the wire between boxes VERY thick and short as possible (IE one box on top of the other) it will be doable. Adding the extra huge caps or cap6's as I suggested and taking the speaker ground from there would also work.

Hint to understanding the issue: If a wire has 0.1 Ohm resistance and 10A AC is flowing then you have 1V AC generated between the ends of this wire... "Ground" is now 1V AC.... the amp needs less than 1V input for full power output! Multiply this by several wires.... then ask yourself "What truly is ground???"

At the most extreme of examples I've known, ultra high performance voltage regulators I've designed and built, where not only does 1" of wire matter, it matters so much that it works with things connected to one end of the 1" wire but oscillates if connection is made to the other end!

Edit: here's a brain teaser folks. On that mega critical high performance regulator above I had the thing nice and stable at the end of the night but next morning it oscillated.... Why?

Clue is: electrolytic capacitors

 

[hammeredklavier]

If you make the wire between boxes VERY thick and short as possible (IE one box on top of the other) it will be doable. Adding the extra huge caps or cap6's as I suggested and taking the speaker ground from there would also work.

Hint to understanding the issue: If a wire has 0.1 Ohm resistance and 10A AC is flowing then you have 1V AC generated between the ends of this wire... "Ground" is now 1V AC.... the amp needs less than 1V input for full power output! Multiply this by several wires.... then ask yourself "What truly is ground???"

At the most extreme of examples I've known ultra high performance voltage regulators I've designed and built where not only does 1" of wire matter, it matters so much that it works with things connected to one end of the 1" wire but oscillates if connection is made to the other end!

Thanks, I think I'm starting to see the light. Not quite as simple as 'wiring up' it seems..!

 

[say it as it is]

I have used 4mm or 5mm to replace the base on older cases.
If replacing the base is an issue then drop in a 5mm slab inside and mount everything on that the size of it will dissipate heat or add a few heat sinks as close to the boards. All about surface area and conductivity.
The Naim case is basically a big heat sink with the alloy shell.
The older cases were all steel and not great the newer ones with aluminium sides and option of aluminium bases and front/end plates.
Steel case not impossible but need to think about cooling, can work out easier to build it all on the aluminium slab the Avondale A260Z was made that way and the part build ones were sold that way.