[SGK]

What's a rough practical footprint (and height) for an uncrowded dual mono build?  (stereo with separate power supplies)

[jtwrace]

What's a rough practical footprint (and height) for an uncrowded dual mono build?  (stereo with separate power supplies)

See this thread: http://www.audiocircle.com/index.php?topic=106187.0

[SGK]

A read through that thread has got me wanting to give this a go. I admire the craftsmanship that's gone into some of these builds.

 At the moment I have an old bridged Krell KAV150a driving my centre speaker (Egglestonworks Andra III Center) and another Krell KAV 150a driving the rear speakers (Egglestonworks Rosa).  Driving my front speakers, Egglestonworks Andra III, is a Krel FPB 200.  I wonder how an NCore would compare either as a 3 channel setup to replace the KAVs or stereo to compete against the FPB.

Can I ask some incredibly basic questions? 

I notice people generally seem to be using a switched IEC inlet with a fuse.  Why not use a circuit breaker to avoid the fuse (and use as a main power switch)?

Would a 3 channel setup require a high current inlet?

Would there be any heat issues having 3 PSUs and 3 amp modules in the one enclosure of circa 450W x 300D x 80H (mm)?

Incredibly dumb question... I noticed in Steidl Guitars's build here http://www.audiocircle.com/index.php?topic=106187.20 bolted connections are being made to the inner side of the rear plate of the chassis without going fully through the plate. How is this done? (A short tapped hole plus a threaded insert or more basic?)

Where do you source the cable tie down anchors I see attached to the interior of some of the chassis and how are they affixed?

(I have questions on how to wire an on-off switch (or I guess more appropriately a mute switch) but they can wait.)

[Steidl Guitars]

I noticed in Steidl Guitars's build here http://www.audiocircle.com/index.php?topic=106187.20 bolted connections are being made to the inner side of the rear plate of the chassis without going fully through the plate. How is this done? (A short tapped hole plus a threaded insert or more basic?)

Those are all through holes -- bolts through the outside, nuts on the inside.  You could drill and tap them if you preferred. 

Where do you source the cable tie down anchors I see attached to the interior of some of the chassis and how are they affixed?

Any of the usual general suppliers such as Mouser, etc. 

[SGK]

Those are all through holes -- bolts through the outside, nuts on the inside.  You could drill and tap them if you preferred. 

Any of the usual general suppliers such as Mouser, etc.

Ah silly me.  I looked again at your photos and this time it's obvious.

What are they properly called?  (To help me search)

BTW I think your build is superb!

[Steidl Guitars]

What are they properly called?  (To help me search)

I assume you mean the cable mounts?  I don't know their official name, but Mouser lists 3,000+ items under cable mounting accessories: 

http://www.mouser.com/Wire-Cable/Wire-Protection-Management/Cable-Mounting-Accessories/_/N-apvm6/

BTW I think your build is superb!

Thanks, although it is pretty darned pedestrian compared to some others!

Good luck to you if you build one. 

[SGK]

Yeah I spent quite a lot of time looking through there - like looking for a needle in a haystack.  Perhaps someone else will have the answer that helps me narrow the search, plus answers to my other questions.

I would describe it as elegant.  BTW did you ever sort out the wiring for your front switch so that the light turned off when the amp was muted?

[jtwrace]

I notice people generally seem to be using a switched IEC inlet with a fuse.  Why not use a circuit breaker to avoid the fuse (and use as a main power switch)?

The SMPS has a fuse built in so another isn't needed or required.

Would a 3 channel setup require a high current inlet?

No.

Would there be any heat issues having 3 PSUs and 3 amp modules in the one enclosure of circa 450W x 300D x 80H (mm)?

I don't think so.  Just put a few vents in the top and you will be fine.

[Steidl Guitars]

like looking for a needle in a haystack. 

Yep, but the filtering system works well.  Maybe "cable mounts" or "cable hold downs."  I can check my receipt when I get home. 

BTW did you ever sort out the wiring for your front switch so that the light turned off when the amp was muted?

I did; it was just a matter of wiring it differently. 

[Julf]

The SMPS has a fuse built in so another isn't needed or required.

And make sure the IEC connector doesn't have a filter built-in...

[SGK]

Thanks all.  BTW I noticed some people splashing out on rhodium plated connections.  I found this intriguing given what I had previously read about rhodium.

http://www.mains-cables-r-us.co.uk/sitefiles/15/2/2/152201/On%20the%20Conductivity%20of%20Selected%20Metals.pdf

[Julf]

BTW I noticed some people splashing out on rhodium plated connections.

Maybe they run their gear very hot?

[SGK]

   Nothing like listening next to a blast furnace.   And one wouldn't want their gold plating melting off.

PS I found the cable tie mounts here  http://uk.rs-online.com/web/p/cable-tie-mounts/0521140/

[SGK]

Julf

I have read and re-read the discussion on pg 33 of this thread regarding whether or not the chassis should be connected to the mains "ground" (by connecting the ground pin of the IEC inlet to the chassis).  Of course, the easy/safest thing to do is connect it and move on. But with respect to the specifics of building a supplied NC400 amp with a SMPS600 power supply, I'm a bit confused as to what specific things need to be adhered to in order to comply with Class II and hence not need to link the chassis to mains supply ground? Double insulated wire for the internal AC wiring?

You might respond "if you have to ask, just wire the ground IEC pin to the chassis and play safe" but I'd like to understand this better.

Regards

Steve

If it's relevant, I would be using balanced XLR input (from the rear of the chassis connector: left pin 1 to cable shield, right pin 2 to +ve, bottom pin 3 to -ve and top pin to chassis. I also understand from reading here that the nAmpon "thin black wire" needs to be connected to the chassis although I do not yet understand the wiring if nAmpon and a front panel mute switch.

I feel like there is an installation manual I am missing even though I have read the data sheets and manuals for both the NC400 and SMPS600.  Perhaps it's just a case of reading them again!

[Julf]

Steve,

I'm a bit confused as to what specific things need to be adhered to in order to comply with Class II and hence not need to link the chassis to mains supply ground? Double insulated wire for the internal AC wiring?

While Class II is usually involves double insulation (not just of the wiring, but everything that carries a voltage), the real guiding principle is "no single failure should result in dangerous voltage becoming exposed so that it might cause an electric shock". Class I accomplishes this by having the chassis connected to safety earth, so that a failure will be shorted to earth and causes the fuse(s) to blow. In Class II you have to accomplish the safety function without grounding the chassis to safety earth, so insulation requirements are much stricter.

If you have a metal case, you need to make sure the electronics are well enough insulated from the case, and that nothing can be inserted into any hole in the case so that it makes contact with any of the electrical circuits.

There are formal requirements for Class II, but they shouldn't apply to a hobbyist making something for their own use - but do understand that I can not recommend anything else than conforming to the formal Class II safety requirements and standards.

If it's relevant, I would be using balanced XLR input (from the rear of the chassis connector: left pin 1 to cable shield, right pin 2 to +ve, bottom pin 3 to -ve and top pin to chassis. I also understand from reading here that the nAmpon "thin black wire" needs to be connected to the chassis although I do not yet understand the wiring if nAmpon and a front panel mute switch.

nAmpon needs to be connected to ground (the cable shield). Ground (the cable shield) might or might not be connected to the chassis (the Hypex recommended connection is to connect both the cable shield and pin 1 of the XLR to the chassis). If you have a metal shell XLR connector, the top (shell) pin will be connected to the chassis anyway through the metal contact between the XLR shell and chassis.

[SGK]

Steve,

While Class II is usually involves double insulation (not just of the wiring, but everything that carries a voltage), the real guiding principle is "no single failure should result in dangerous voltage becoming exposed so that it might cause an electric shock". Class I accomplishes this by having the chassis connected to safety earth, so that a failure will be shorted to earth and causes the fuse(s) to blow. In Class II you have to accomplish the safety function without grounding the chassis to safety earth, so insulation requirements are much stricter.

If you have a metal case, you need to make sure the electronics are well enough insulated from the case, and that nothing can be inserted into any hole in the case so that it makes contact with any of the electrical circuits.

There are formal requirements for Class II, but they shouldn't apply to a hobbyist making something for their own use - but do understand that I can not recommend anything else than conforming to the formal Class II safety requirements and standards.

Ok. So presumably proper installation means (in this respect) making sure the non-isolated spacer on the PSU has proper contact with the chassis, using the cables provided in proper fashion (I'm assuming that everything that one gets from Hypex of course conforms) but that using something like Cardas 15.5AWG litz wire for internal AC wiring would not technically conform to Class II due to the lack of double shielding?

http://www.hificollective.co.uk/catalog/cardas-137mm-diameter-copper-multistrand-metre-p-8288.html?chooseimage=1

nAmpon needs to be connected to ground (the cable shield).

Where are the instructions for connecting nAmpon? (Or is that it?) I would want to have a front switch mute the amp in very much the way Steidl Guitars did (with the switch light off when the amp is muted).  I don't yet understand how to achieve this.

Ground (the cable shield) might or might not be connected to the chassis (the Hypex recommended connection is to connect both the cable shield and pin 1 of the XLR to the chassis). If you have a metal shell XLR connector, the top (shell) pin will be connected to the chassis anyway through the metal contact between the XLR shell and chassis.

Ok so cable shield (and nAmpon) to pin 1 and pin 1 to chassis.  Leave the top pin alone. Keep it simple. Because I'm a bit of a Cardas fan I may use these:

http://www.thecableco.com/Product/CM-XLR-F-Chassis  (despite the rhodium)

[Julf]

using something like Cardas 15.5AWG litz wire for internal AC wiring would not technically conform to Class II due to the lack of double shielding?

As long as you can ensure the litz wire doesn't make contact with the metal case you should be OK. You could use spacers, or a separate, insulated sub-chassis.

Independent of the Class II issue, I am not sure litz wire is such a good idea. Litz wire has a higher inductance than ordinary stranded wire, and for something like the nc400/smps600 you probably want the lowest possible inductance. Litz wire is good for conducting frequencies in the 1 MHz range - but with the nc400/smps600, you want to attenuate, not accentuate, anything above 50/60 Hz.
 

Where are the instructions for connecting nAmpon? (Or is that it?)

Pretty much, yes. Formally I guess it is specified in the NC400 data sheet, under 8.3 "Pulling nAMPON low enables the amplifier" and table 3 specifying logical high as  2.65-3.6V and logical low as -0.3-0.5V, with a 27K pull-up to 3.3V. Thus grounding the nAMPON enables the amplifier. Ground is different from safety earth.

I would want to have a front switch mute the amp in very much the way Steidl Guitars did (with the switch light off when the amp is muted).  I don't yet understand how to achieve this.

I suggest using a double pole changeover (DPDT) switch, with one pole for the nAMPON signal and another for the light. Another possibility is using a relay.

Ok so cable shield (and nAmpon) to pin 1 and pin 1 to chassis.  Leave the top pin alone. Keep it simple.

Agree.

Because I'm a bit of a Cardas fan I may use these:

http://www.thecableco.com/Product/CM-XLR-F-Chassis  (despite the rhodium)

Fine if you like bling

[SGK]

As long as you can ensure the litz wire doesn't make contact with the metal case you should be OK. You could use spacers, or a separate, insulated sub-chassis.

Independent of the Class II issue, I am not sure litz wire is such a good idea. Litz wire has a higher inductance than ordinary stranded wire, and for something like the nc400/smps600 you probably want the lowest possible inductance. Litz wire is good for conducting frequencies in the 1 MHz range - but with the nc400/smps600, you want to attenuate, not accentuate, anything above 50/60 Hz.

Any particular recommendations for a quality build? (I live in the UK)
 

Pretty much, yes. Formally I guess it is specified in the NC400 data sheet, under 8.3 "Pulling nAMPON low enables the amplifier" and table 3 specifying logical high as  2.65-3.6V and logical low as -0.3-0.5V, with a 27K pull-up to 3.3V. Thus grounding the nAMPON enables the amplifier. Ground is different from safety earth.

Thanks.  I'm new to this sort of DIY.  I will read the sheets again and try to understand this better.  Presumably a mute switch simply lifts this ground for disable?

I suggest using a double pole changeover (DPDT) switch, with one pole for the nAMPON signal and another for the light. Another possibility is using a relay.

I very much like the look of what Steidl deployed with the light part of the switch itself.  He used a part similar to the Bulgin MP0045/1E2BL012.  http://www.mouser.com/ds/2/57/Bulgin_2010_p193-15602.pdf  It's a DPCO switch which I believe is similar in practice (?). (I note his point about needing a resistor because of the higher voltage.)


Gotta have a little bling... 

[Julf]

Any particular recommendations for a quality build? (I live in the UK)

For the AC wiring, my recommendation is just decent 2.5 mm copper-cored AC wiring cable. The effect of the length of wire inside the amp case is rather insignificant compared to the run from the IEC plug to your local AC supply transformer through the house wiring...

Presumably a mute switch simply lifts this ground for disable?

Yes - the active pull-up will pull it up to 3.3 V (and thus disable the amp) if unconnected (as many of us discovered when we first tried our amps and wondered why there was no sound ).
 

I very much like the look of what Steidl deployed with the light part of the switch itself.  He used a part similar to the Bulgin MP0045/1E2BL012.  http://www.mouser.com/ds/2/57/Bulgin_2010_p193-15602.pdf  It's a DPCO switch which I believe is similar in practice (?). (I note his point about needing a resistor because of the higher voltage.)

I assume you would use the switch as a mute switch, rather than to switch the AC - in the latter case I would be concerned about the 3A rating of the switch.

Yes, a DPCO is perfect fr your use - one pole for the mute, the other for the light.

[SGK]

I assume you would use the switch as a mute switch, rather than to switch the AC - in the latter case I would be concerned about the 3A rating of the switch.

Yes, a DPCO is perfect fr your use - one pole for the mute, the other for the light.

Correct.  Not sure I see a need for turning off the AC.  Thanks for all the help.