NSI - the first impressions

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Gilbert Y
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Re: NSI - the first impressions

Post by Gilbert Y » Sun Dec 16, 2018 8:13 pm

Here is my first attempt. Feel free to ask questions.

I am not good enough to teach so don’t expect to learn anything. These are only my opinion basic on knowledge and experience.
These are simplified version of a very long and complex topic. I have to omit way more than I need to say in order to get to this “short” version. There are many more points to be discussed.

Electrically, there isn’t much different between an integrated amp and pre/power amp. They both have power supplies, input stage and output stage. If an integrated amp has separate pre/power power supplies, that will make no different between the two.
Signal path wise, there is no different at all. Integrated amp has input stage a.k.a. preamp stage. Output stage a.k.a. power amp stage. Some has more than two stages, I am making things simply here. In real life, preamp has its own input stage and output stage. Sometime these two can combine into one. Power amp has at least two stages, input stage and output stage. The input stage is to accept signal from the preamp. In the case of integrated amp, the input stage of the power amp can be eliminated because they are all in one chassis. If less is more theory applies, this is one advantage of integrated amp being one less stage in the signal path.

Why making the preamp and power amp separate? There are several reasons. One or them is marketing want to sell more gears. Preamp and power amp, that’s two gears. Usually sell for a lot more than one integrated amp. From an engineering point of view, when a power amp get up to a certain power output, it is not practical to put all the parts needs to product such power into one chassis. It is not easy to say at what power. Different Class of output will have a different crossover point from one chassis to two chassis. If I have to make a number for a Class AB output, I will say somewhere around 150 watt per channel. Anything less can be reasonably put in one chassis and still market-able and practical to put on a shelf. Anything higher than 150 watt per channel is going to be difficult to put in one chassis. I understand there are many companies offering high power integrated amp claiming they are Class AB but looking at the size of their heatsink, I am seriously doubt they can sustain the rated power output for a reasonable amount of time. To be fair, if it is for home use, nobody need more than 150 watt per channel to obtain reasonable volume. Higher rating is mostly for marketing purpose.

Unless there is a need for higher power due to speaker demand, etc. It is best to have amp that is 100 watt or less. Higher power mean more number of transistors is need to be paralleled for the require power. Each transistor is never going to be perfect match. Matching transistors mean trying to match them as close as possible but never perfect. When they ages, they aged in a slightly different rate. Therefore, when the amp gets older, the transistors are possible less matched compare to when it is brand new. Therefore best to use one single transistor for output. However, one transistor can only handle up to a certain power. My personal sweet spot of power is 80 to 85 watt per channel.

Form a noise point of view, an integrated amp with separate power supply is much better than pre/power. With the separate power supply, all the signal path from input to output are separate from the transformer(s). Result in low noise. With preamp and power amp, assuming they have transformer(s) inside the same chassis as the signal path. Regardless how much care a designer is taken for lower the noise, there is always some noise caused by the internal transformer. This may not be audible directly from the speaker. Usually these are measurable noise which causes a lesser back background.

Integrated amp also eliminate the needs of interconnect between pre/power amp. The interconnect cable is an unknown to the designer of the pre and power amp. If the user likes to try new cable to “tune” the sound, pre/power may be the way to go. However, in term of pure sonic performance point of view, it is best to have all the signal path in one chassis. Of course if you trust the designer of what he/she is doing.
NSI is an exception. It breaks some of the typical rules being so big and impractical to place on any shelf. It is likely not market-able by any marketing department. That’s why we don’t have one. We, however, will try to make it in two smaller chassis to place on shelves and racks just to make it more useable.

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Don Leman
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Re: NSI - the first impressions

Post by Don Leman » Tue Dec 18, 2018 11:50 am

Thanks Gilbert. I had not thought of the problem of multiple transistors ageing differently and becoming less matched than when new. Makes sense. I had read previously that amps around 50 to 60 wpc usually sounded better and now I know why.

I guess separates still give you the advantage of being able to upgrade either the amp or preamp without the other. Or if you start out with a solid state preamp and want to go with tubes it would allow more flexibility without the expense of changing everything.
Don

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Gilbert Y
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Re: NSI - the first impressions

Post by Gilbert Y » Wed Dec 19, 2018 10:15 pm

Don

If you are looking from an upgrade point of view, you are correct that pre/power offer more flexibility than integrated.

Chowder_head
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Re: NSI - the first impressions

Post by Chowder_head » Thu Dec 27, 2018 12:23 pm

Thanks for the straight shooting in your discussion of the NSI.

nikki
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Re: NSI - the first impressions

Post by nikki » Thu Jan 03, 2019 9:36 am

Happy New Year!

Thanks for the detailed response. When I asked the question, I was wondering if there was a specific design decision that required you to use an integrated approach. I understand and agree with the reasons why an integrated amp can be a preferred approach from a purely performance perspective but these advantages are universal in a sense.

For a statement piece such as the NSI, I would still choose separate components for the reasons already suggested by yourself and others. But this why Blue Circle is so unique - the choices are virtually unlimited!

Very exciting new product, will have to hear for myself one day.

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Gilbert Y
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Re: NSI - the first impressions

Post by Gilbert Y » Thu Jan 03, 2019 8:21 pm

If 2019 Toronto show is as good as 2018, it's worth taking a day or two off to attend. If you want to hear the NSI, I may even keep the door open after hour for you. As long as you bring a couple of chicken omelettes from the diner beside the hotel. I will work for food. You add a daily soup to the order, I will let you play one additional CD. :D :P :lol:

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