News is up

sceptic · « **on:** 2 Apr 2003, 09:12 am »

.
http://www.norh.com/news.html

2 months for the price of one!

mbarnes · « **Reply #1 on:** 2 Apr 2003, 08:06 pm »

With all the new products coming out, I think it will be more a matter of updating these pages than writing something new.

sceptic · « **Reply #2 on:** 2 Apr 2003, 08:17 pm »

Its 3-00 am out there!
Are you up late or early?

Xi-Trum · « **Reply #3 on:** 2 Apr 2003, 09:30 pm »

Le Amp II Specs: 200W into 8 ohm, 400W into 4 ohm, 800W into 2 ohm.

Possible with an 800VA power supply?

mbarnes · « **Reply #4 on:** 3 Apr 2003, 09:12 am »

Remember, it is one channel--not two. We need 40 volts RMS dropped across 8 ohms to dissipate 200 watts (40 x 40 /8). We need to increase the rail voltages enough to cover peak output. The peak output for 40 volts would be 40 x 1.414 or 56.56 volts. We will allow another five volts for JFETS which is 61.56 and 7% for additional losses which is another 4.3 volts.

We have our voltage set at 67 volts which is sufficient to support 200 watts.

mbarnes · « **Reply #5 on:** 3 Apr 2003, 09:47 am »

I was typing while I was on the phone so I didn't write out the whole thing.

I showed that we need about 66 volts in order to support the power. To calculate the V/A we then go back to the 40 volts we needed we need across 8 ohms to compute the amps required.

This means we will need 5 amps per rail or 10 amps to support 200 watt. We multiply 10 amps x 67 volts and we have 670 V/A required per channel. This would mean we would need 1340 V/A for two channels.

Xi-Trum · « **Reply #6 on:** 4 Apr 2003, 02:29 pm »

I'm rusty in my freshman circuits class so the numbers just went over my head.

But I don't believe for a moment that an 800 VA power supply can pump out 800W continuously, especially when a LOT of heat is generated. Either the power supply is severely underrated or the output is severely overrated.

mbarnes · « **Reply #7 on:** 4 Apr 2003, 08:12 pm »

Quote from: Xi-Trum

I'm rusty in my freshman circuits class so the numbers just went over my head. But I don't believe for a moment that an 800 VA power supply can pump out 800W continuously, especially when a LOT of heat is generated. Either the power supply is severely underrated or the output is severely overrated.

A standard transformer saturates and becomes less efficient at higher power.
A switching power supply does not work the same way. A switching power supply sets the voltage with a small transformer. A full bit switching power supply uses mosfets to create a constant power output.

A switching power supply is more efficient and runs cooler. We have promoted the amplifier at 180 watts RMS into 8 ohms but we have measured 200 watts RMS.

Why not show me another amplifier on the market anywhere near this price with 800 V/A per channel. I have a Bedini amp that claims 200 watts per channel Class A which is 600 V/A for both channels.

The numbers I used are pretty straight forward. Please look them over . It is simple ohm's law.

Xi-Trum · « **Reply #8 on:** 4 Apr 2003, 08:45 pm »

I'm not questioning the claim that it can produce 200W into 8 ohm. I'm questioning the claim that it can produce 800W into 2 ohm.

Did you actually measure this output or simply calculated it? Please answer this simple question.

ABEX · « **Reply #9 on:** 5 Apr 2003, 07:25 am »

Either way you work the numbers it's a pretty impressive amp given the design features and cost.It should put the newer switching amps that are coming out a real run for the money (no pun intended) .

Or am I missing something here?

mbarnes · « **Reply #10 on:** 5 Apr 2003, 08:25 am »

This has been typical of the way nOrh is challenged since we came into existance. Go back and look at the challenges. They usually try to say that because I am a computer guy and my staff is all Thais, we can't possibly be able to challenge the audio world.

The statement here is that we have an underpowered power supply for an amplifier we state 180 watts. The author claims emphatically--despite the math that I outlined for him, that 800 V/A is not enough power. Please let me refer you to the following review of a Bryston amplifier as follows:

http://www.bryston.ca/reviews/14b/ie14b.html

"The signal path has been kept as short as possible and beefy transformers rated at 750 V/A each assure stability of the power supplies.
Our unit was spec'd out and provided rather impressive measurements. Harmonic distortion is 0.00332% at 20Hz, 0.00288% at 200Hz, 0.00343% at 2kHz and 0.00570% at 20kHz. Intermodulation distortion is 0.00374%; noise was measured at -110dB from 20Hz to 20kHz. Power at clipping measured 582 watts per channel, though the component is rated at 500 watts/ch into 8 ohms and 800 watts/ch into 4 ohms. The input impedance is 15k ohms balanced and 50k ohms unbalanced. Input sensitivity is 2 volts balanced and 1 volt unbalanced (100w/8 ohms). All in all, this amplifier is an excellent piece of work by anyone?s standards. "

The person posting here has said it is impossible to get 800 watts out of a 800 V/A transformer. We show math that you can. He says we are wrong. Above is a review showing that a Bryston amp with 750 V/A power supply gets 500 watts into 8 ohms and 800 watts into 4 ohms.

Xi-Trum · « **Reply #11 on:** 5 Apr 2003, 01:15 pm »

Well... when you publish some specs, it would be natural for others to question them. Is there anything wrong with that? No doubt that the LA2 has a very good power supply for its class. But when I see too-good-to-be-true specs, I can be skeptical. I did not see the Bryston review. But I can tell you that I would express the same skepticism of that review as well.

Just to make it clear. My question was by no mean an attack on you or your company. I don't know how you became very defensive about this. I'm sorry that you feel that way.

Back to the topic at hand. Given that the system is not 100% efficient as evident in the heat loss (LOTS of it), I am skeptical that a 800VA power supply can put out 800W. To be fair, I did raise the possibility that the power supply is underrated. This happens. For example, my 300W (rated) Fortron computer power supply can put out a stable 390W (measured) of power.

Anyway, you still HAVE NOT ANSWER THE QUESTION: Did you actually measure the output or simply calculated it to make the claim?

By now, I'm guessing that you calculated the THEORETICAL power output since you've been throwing math around. Is that correct?

Marbles · « **Reply #12 on:** 5 Apr 2003, 01:25 pm »

I think MB will have the amps or prototypes in Lima in a week.

While I will not be able to measure them, I will be able to listen to them on equipment I am very familiar with.

I think that with all the guys from AC that are going, that there will be a substantial amount of feedback on these amps.

IF they can meet or exceed the musicality (and all that go with it) of the LA's then they will indeed be special at their pricepoint. If they can't meet or exceed the originals, then I think MB will need to tweek them until they do. In either case it will only be a week until a lot of us can listen to them.

Xi-Trum · « **Reply #13 on:** 5 Apr 2003, 01:30 pm »

Thanks, Marbles. I'm very interested in your feedback on this thing. I've been looking around for something more powerful than the LA. The specs of the LA2 sounds too good. But I hope they're true.

Cheers.

ABEX · « **Reply #14 on:** 5 Apr 2003, 02:54 pm »

XI-TRUM
I was not trying to stir the pot or anything by stating what I did and as a consumer you do have a right to be skeptical.Maybe you should use the Emoticons to tone down your directness as others do.

I am not defending MB's defensive point of view either,

but I understand where he is coming from also because in a way I think his integrity is being challanged.When you work at something and are proud of what you have created then someone says no way it can be so it might very well put you on the defensive also.

MARBLES
I look forward to your impression as I really am hopeing that these amps are as MB says they are in stating they are in the SOTA league for a fraction of the $$.

If they are comparable to his Bernings then I do not see why they would not be.The story sounds sweet and he knows what I am looking for in an amp.I'll be saving my pennies for a few sets in the event they are as I am looking to Verticle amp my new speakers which I am eaiting for at present.

Modified NEAR M50's.I will have the most advanced set on the planet and I am really jazzed about that!

Now I can hope to be jazzed about having some great amps to drive them!

Regards,ABEX

mbarnes · « **Reply #15 on:** 5 Apr 2003, 05:40 pm »

When you speak of Computer power supplies, you are talking about half bit switching power supplies. These power supplies only conduct half of the wave cycle. This is why they are only 60% efficient. The switching power supply we have is full bit. This means it conduct during both cycles.

I think that the general misunderstanding is that when we talk about watts, we are talking about DC. For DC, watts = voltage x amps. Volt Amps or VA are the terms for AC apparent power.

Watts is the measure of actual work while VA is the available power.

The rating we are using for now is 180 watts. 800 V/A is a massive power supply for this amount. That makes 1600 V/A per stereo pair.

The issue for selecting the power rating is the amount of heat we have to deal with--not the limit of the power supply. It isn't the power supply that gets hot, it is the heat sinks because of the gain stage running pure CLASS A.

jcoat007 · « **Reply #16 on:** 7 Apr 2003, 10:26 pm »

So how do we get in on the $195 each special for the Le Amp II?

I think the all chrome look for ACA 2b is awesome.

Way to go.

Steve

NealH · « **Reply #17 on:** 8 Apr 2003, 11:10 am »

It looks like to me that this amp is using a classical switching supply. This is far from new technology, even in audio amplifiers. Bob Carver has been using it for some time and Linn uses it and I am sure there others. Properly implemented it can be efficient and effective. Something that bothers me more about this amp is that Nohr claims no negative feedback on the web page. Yet when I look at the schematic of the TDA 7294 it clearly shows global feedback being employed (22K resistor in feedback loop). Now I may be missing something here as I am also a little rusty in my electronics. It is possible that Nohr is having a custom unit built without this feedback resistor or, perhaps he is cutting this part out of the circuit somehow. I certainly do not think he would mislead us on the use of negative feedback so I am interested in what they have done. But an answer is not necessary as I understant it may unveil proprietary information.

sceptic · « **Reply #18 on:** 8 Apr 2003, 03:07 pm »

LeAmp2 does not use the TDA 7294.
Have a look at the recently updated News.
I do not understand the no feedback though.