[jtwrace]

Just to make sure there was a power surplus. I have a thing about headroom. I didn't know it didn't measure as well as the NC400, because I'm not following that thread.

Oh trust me I know all about headroom.  I had 300wpc Class A amps on 95dB speakers.   

[Rclark]

I can't imagine needing more than 400 watts with dips into 5 or 600 depending on load. But you never know.

[Russell Dawkins]

I'm thinking of it more as a conservatively specified 200 wpc, since that's the rating into 8 ohms and most speakers that interest me are 8 ohms types.
Looking at the 4 ohm "large signal tests" (fig. 9.2 on the NC400 datasheet) I would think of it more as a 300 wpc amp at 4 ohms, since the distortion curve goes pretty much vertical beyond that - or 400 watts with almost zero headroom.

[Rclark]

Well compared to the maxed out 85 or so I'm getting now, that's Cadillac power.

[roscoeiii]

Bummer that they are now not available until May. Great for Hypex that they are selling so well. But a two month wait is rough. Just as I was about to pull the trigger on the batch due in week 11, boom no luck until week 18...

[Russell Dawkins]

Bummer that they are now not available until May. Great for Hypex that they are selling so well. But a two month wait is rough. Just as I was about to pull the trigger on the batch due in week 11, boom no luck until week 18...

It does sound like a worthwhile wait, though, and gives you time to sell your existing amp(s) before word gets out!

[James Romeyn]

Hey, who wants to buy a French YBA-designed 3-ch amp?

Russell, thanks for your critique of the power specs.  300Wrms @ 4 Ohms is about double or more the power of my current amp, so that should be sweet.

What do you make of the power @ 2.7 Ohms with one SMPS600 per channel?  How might you expect 120V performance to differ, if at all, vs. the 230V test specs?     

[Rclark]

Yeah, time to save, casually choose some chassis'...

[Russell Dawkins]

Hey, who wants to buy a French YBA-designed 3-ch amp?

Russell, thanks for your critique of the power specs.  300Wrms @ 4 Ohms is about double or more the power of my current amp, so that should be sweet.

What do you make of the power @ 2.7 Ohms with one SMPS600 per channel?  How might you expect 120V performance to differ, if at all, vs. the 230V test specs?     

YBA are wonderful amps in my book, but this brings up a point in reference to what Rclark said about chassis. Yves Bernard André (YBA) told a friend of mine (in 1993) that if it were not for marketing difficulties, he would sell his amps without metal tops and bottoms because they spoiled the sound, and he advised us to take these panels off our own amps for the improved sound. In fact shortly after telling us this, I think he did sell one of his models - an "Intégré" - with an acrylic or glass top. Yves was early into damping components like capacitors, and considered that was an important part of the YBA sound. As a result we at our store damped everything we feasibly could with some black automotive goop - I forget the name. It was one of our secret weapons. It seemed to help almost everything we applied it to, including IC's.
If I were playing with these Ncore modules, I would experiment with minimally enclosing them, metal-wise. I would compare their performance outside of a case with inside, and with metal and wood cases. I notice that the one trial and review was done with these out in the open - no chassis as such. I just would say when it comes time to drop them in cases, pay attention to any potential effect on the sound. Denis Morecroft is no fool - he pioneered this concept, I think, as well as others which have caught on big time: http://www.dnm.co.uk/materials.html
and with these amps as revealing as they supposedly are, this may be particularly important.

As to the 240 vs 120v question, as well as the 50Hz vs 60Hz factor, I think that with switching mode power supplies this does not make much difference as the transformer operates at a much-higher-than-line frequency, and thus does not need to be bigger as is needed in linear supplies for 120v vs 240v.

As important as the absolute power is the amp's behaviour in recovery from clipping. This was found to be one of the few measurable performance characteristics that co-related with apparent sound quality in a survey done some time ago by HFN in response to the Ongaku sounding so good and measuring so bad. The other, by the way, was the degree to which RF contamination affected the amp's performance. It seems that amps are in some degree of clipping much more of the time than is commonly realized, so clipping recovery behaviour, which is associated with stability as regards oscillation, is important to the sonic character because most amps are spending a lot of their time recovering from clipping. Clipping drives many amps into incipient oscillation which is ringing, and generally doesn't sound good. Anthony Michaelson of Musical Fidelity speaks honestly about this; few do.

I feel confident Bruno has all this well in hand, though, and is one of the factors contributing to the open, revealing and effortless sound spoken of.

[Rclark]

 Very interesting Russell and thanks for the link. Does anyone make a chassis as such, that allows the fields created to "breathe" ? I think an clear chassis could be neat just to see the tiny modules inside as well as the light show they put off.
 
 They'll be butted up to the back end of each speaker and so not really visible unless you walk around to see. So light show is no problem. In fact, with the room lights off, the glow from behind each speaker might be kind of cool.

 (I'm sure someone wanting to experiment with this but not interested in lights could just tint them out)

[James Romeyn]

Russel,
What about plastic boxes?

Also, for future amp/speaker builders: IMO routing speaker level signals through binding posts is hazardous for performance.  Super high-quality posts go up to about $75/pr IIRC. 

I prefer to drill a hole directly next to the posts, in the speaker terminal board and the chassis panel in the amp, to which the posts are attached.  Post composition does not matter as long as they are strong and have large holes for bare wire.

For extra insulation in a metal chassis panel you can add a rubber grommet.

The speaker wire (in the speaker or the amp) exits the hole next to the post.  Tin the bare wire end.  On the amp-to-speaker cables, tin the bare wire ends.   

Insert both tinned wire ends in the post holes and tension with the post knob.  The post is only a mechanical coupler for two tinned wire ends. 

In normal post use you solder (or screw a spade terminal) inside the post, the signal passes along the post length via plating and internal composition, then through the plating again to a spade or banana plug outside the post, from the spade or banana to the wire.     

I'm sleepy and will re-write this tomorrow if not clear.           

[Russell Dawkins]

Russel,
What about plastic boxes?       

Well, Denis Morecroft uses acrylic - poke around his site from the link above. It's an education. He also pioneered the concept of solid core unshielded cables of the smallest gauge to carry the signal, also slit foil capacitors. He has been at the bleeding edge of this stuff consistently for the last 27 years or so, but he was so uncompromising that his product always looked really expensive for the numbers (watts, pounds), partly because it was (is?) made in Switzerland and so never sold in numbers, nor did he advertize much. Not a commercial success, in other words, though he still seems to be around. I never did actually see or hear one of his amps.

edited to add this link to preamp review: http://www.stereophile.com/artdudleylistening/308listen/index.html

[Rclark]

please rewrite that James 

[*Scotty*]

Per Russell's post, this is why he wants extra power or headroom, so that he doesn't have to listen to the amp operate in a condition of clipping. This is what makes 300 watts a channel powering a speaker with 95 dB sensitivity a very sane thing to do.
 I have speakers with 95dB sensitivity also and 108 watts/ch and I always wonder if I am going to run out of steam on peaks. I have Russell's recording of Prokofiev/Tchaikovsky which has little to no compression depending on which CD you are are listening to and I have never tried to play it back with the peak volume that occurred during the live performance, something like 126 dB instantaneous peak SPL. I suspect that I might need about 1000 watts into 8ohms to deal with the recording.
 Most of the music I listen to has a very limited dynamic range compared the aforementioned recording and seldom asks for the kind of power levels that would tax my combination of power amp and speakers. I have one other recording that is worrisome, it is the recording of the 1910 version of the complete ballet The Firebird by Stravinsky, Pierre Boulez conducting The Chicago Symphony Orchestra on the Deutsche Grammophone label. It has what sounds like a fairly wide dynamic range for a commercially released recording. 
 You really can't have too much power.
Scotty

[doug s.]

please rewrite that James 

what jim is saying, is instead of soldering the internal speaker and amp wires to their respective binding posts on the inside of the amps and speakers, drill a hole thru the binding post plates (or speaker/amp chassis, if no plates), and let the wires from inside the amps and speakers hang out the holes.  then, place them into the speaker binding posts on the outside of the amp/speakers, along with your speaker cable.  so, when you tighten the speaker cable in the binding posts, you are also tightening the wiring from the internal speaker wiring harness, and at the amp end, the internal amp output wiring...  by doing this, you are making direct speaker cable to wiring harness connections at both the amp end and speaker end.  no speaker cable spades/bananas connecting to chassis binding posts; but direct wire-to-wire connections.  the chassis binding posts are used merely to tighten down the bare wires of the speaker cables to the internal wiring harness of the amp and speakers...

doug s.

[doug s.]

Per Russell's post, this is why he wants extra power or headroom, so that he doesn't have to listen to the amp operate in a condition of clipping. This is what makes 300 watts a channel powering a speaker with 95 dB sensitivity a very sane thing to do.
 I have speakers with 95dB sensitivity also and 108 watts/ch and I always wonder if I am going to run out of steam on peaks. I have Russell's recording of Prokofiev/Tchaikovsky which has little to no compression depending on which CD you are are listening to and I have never tried to play it back with the peak volume that occurred during the live performance, something like 126 dB instantaneous peak SPL. I suspect that I might need about 1000 watts into 8ohms to deal with the recording.
 Most of the music I listen to has a very limited dynamic range compared the aforementioned recording and seldom asks for the kind of power levels that would tax my combination of power amp and speakers. I have one other recording that is worrisome, it is the recording of the 1910 version of the complete ballet The Firebird by Stravinsky, Pierre Boulez conducting The Chicago Symphony Orchestra on the Deutsche Grammophone label. It has what sounds like a fairly wide dynamic range for a commercially released recording. 
 You really can't have too much power.
Scotty

scott, your amp is 108wrms or peak?  if rms, it should theoretically be able to drive your speakers at ~115db all day long.  could your speaker even do 126db if your amp had 1000w?  realistically, i think you awreddy have plenty of power...  if your room is 30x40, then mebbe a little more would be good.  even then, the nc400 should be ok. 

if you have a big room and pro audio speakers capable of 126+db, and you really want 126db peaks in your listening room, then ya, go for 1000wpc...

doug s.

[*Scotty*]

That's RMS with zero headroom and 180w/4ohms.
There is also no way the midranges and tweeter would take anywhere near that power input. The midranges have a maximum power rating of 90 watts and there are two of them per speaker so the amp will clip at about it's 4 ohm peak output about the time the midranges run out of gas.
 The system might do 115dB all day long but I don't think my lease can take it.
The thing is you can't tell when you might run out of gas the system doesn't sound distorted at + 96 dB and my ears have gone non-linear past this point if it's average SPLs and not peaks.  With a CD like Russell's with no compression the sudden peaks can sneak up on you with no warning, bam.
Real uncompressed music is a roller coaster, it sounds great but it's kind of scary and also addicting in an adrenaline junky kind of way.
Scotty

[doug s.]

scotty, i understand perfectly the excitement of real uncompressed music.  i have a horn system that is close to 100db efficient.     and, i also understand that having more than you need, when it comes to power, can be a good thing.  but, everything you said regarding your system points to the fact that your speakers have enough power.    any more, and you will blow your speakers.   in many cases, speakers (tweeters especially) can be blown by overdriving an amp; the clipping will blow the tweeters.  in your case, you could blow them by simply overdriving the speakers.  don't get too addicted...   

doug s.

[timind]

The system might do 115dB all day long but I don't think my lease can take it.
The thing is you can't tell when you might run out of gas the system doesn't sound distorted at + 96 dB and my ears have gone non-linear past this point if it's average SPLs and not peaks.  With a CD like Russell's with no compression the sudden peaks can sneak up on you with no warning, bam.

Scotty

All I can say is, take care of your ears!

[OzarkTom]

Yes, at 126 SPL's, it will not take long before you are deaf.

No matter what casings you use, or even no casings, try using the Moongel drum pads underneath to isolate the amps from your shelves or floor. These pads beats even the most expensive, and can be had for $6.95 for a set of four on Ebay. This even includes the shipping.

These even beats the expensive Stillpoints. I love finding these bargains.