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In Reply to: RE: Note to self... posted by AbeCollins on October 13, 2016 at 16:46:28
For the amplifier to be stable, you need a load on the output stage at RF in order to damp any oscillation stimulated by induced RF. The load is usually a Zobel or R-L or both. What Naim did was to factor the cable impedance into the design of the network. The advantage of doing that is eliminating some passive components between the output stage and the loudspeaker. But in order to take advantage of it, they need control over the cable impedance.
With Spectral + MIT, the Zobel network is in the cable rather than in the amp.
This isn't bad design, it's just a different way of approaching the problem, by looking at things as a system.
Follow Ups:
I get the design. But the problem is the reality that many audiophiles love to experiment with cables and think they know better than the designer of the amp. Perhaps the cables should have been permanently attached to the amp.
n
I get the design too, and IMHO the manufacturer made a poor design choice.
It's not that the user necessarily thinks he knows better than the amp designer but it is expected that one shouldn't have to worry about blowing up the amp if you choose not to use cables supplied by the amp maker.
If I buy a flashlight made by Duracell should I be forced to use Duracell batteries for fear of wrecking the flashlight?
You are "forced" to use a specific Transmission Fluid with virtually every model car or truck you can buy. Fail to use ATF+4 in your Chrysler Automatic and you can expect to be replacing it in 60,000 miles.Sometimes it matters, sometimes it doesn't, but even with your flashlight analogy, you are "forced" to use a compatible battery.
There are a number of topologies an amplifier designer can choose to explore and implement. Some are more stable than others, even though they may all work into an easy 8-ohm load loudspeaker.
If you want to use unusual cables and loudspeaker loads, then the QUAD 303 is stable unconditionally into any load, including a direct short circuit. Others seem to explode if you look at them funny. It's not like there isn't a choice, but it does help if you meet the amplifier designer half way.
Edits: 11/11/16 11/11/16 11/11/16
n
n
NO, it sounds like for the sake of saving a few bucks in parts they burdened the end user with having to buy wickedly expensive cables as well as taking on an extremely high risk of amp failure.
Hey now that IS a better amp!!!
All else being equal, the fewer the number of passive components between the amplifier output stage and the loudspeaker driver, the better. You need a functioning crossover obviously, but if you can eliminate passive components after the output stage in the amp, why not take advantage of the theoretical performance improvement?Naim's approach eliminates a series resistor and inductor that most other amplifiers require as part of the RF damping circuit, and their approach also provides tighter tolerances on the impedances that make up the circuit.
Naim speaker cables are also on the cheap side compared to what most audiophiles use.
Here's another way to think about it. Some people spend gobs of money on complex speaker cable geometries like Nordost and Cardas to try to minimize the combination of series resistance, series inductance, and parallel capacitance. But inside their amp is usually a Zobel (R-C in parallel with the output), followed by an R-L in series with the output. Instead of spending tons of money to reduce the cable impedance, why not put it to work for you?
Edits: 10/14/16
They came up with expensive version for those who want to spend more on wires!
These Lumina speaker cables are 3300USD/ 3 m pair. Old NACA 5 used to be 10/per foot now it's 25/foot ( plus 88 bucks for Naim banana plugs ) so they are not as cheap as they used to be.
They are becoming more accommodating other manufactures' ware to gain broader customer base.
...that the end user shouldn't be burdened with having to choose special cables for his amp. The amp SHOULD BE engineered to accommodate a very wide range of cables of the customer's choosing. The amp SHOULD BE engineered to that principle. Most are, but there are a few 'tweaky' audiophool amps that are not. ;-)Engineering is always a matter of trade-offs and choices. They made the wrong trade-offs, IHMO.
Edits: 10/14/16
No Abe, that's just YOUR philosophy.
One person's philosophy is to engineer components for maximum compatibility with other components from other makers, and accept you might give up a little performance as a result.
Another person's philosophy is to engineer systems to maximize the performance of their design approach, and accept that their gear may not appeal to audiophiles who want to mix & match and play on the cable merry-go-round.
Both are valid engineering approaches based on different goals.
...they think they know exactly what their customer needs rather than asking the customer.
No Abe, that's just YOUR philosophy.
No Dave, my philosophy is in agreement with most amp manufacturers. Only a couple outliers design 'tweaky' amps that require proprietary cables.
These are essentially general market products and should have been designed as general purpose products.
Otherwise they should be sold as tweakers and DIYers products and NOT for the unknowing general public.
THAT is either poor engineering, poor marketing or the company just didn't give a shit and just wanted it out on the market.
The Naim approach to audio is the OPPOSITE of tweaker. They tend to use custom connectors and connection methods so you can't go cable tweaking. Their separates are specifically designed to be used with each other and NOT be mixed and matched with other company's products. And their unique connection methods make it a hurdle to do so. So no, they are not general market products.
You either buy into their systems approach or not. If you're the kind of audiophile who buys a power amp because it has bass slam, and matches it to a tubed pre to warm up the tone, and uses silver cables to add some top end sparkle and air, and isolation footers because they take away some grain, etc. - then you are not a candidate for a Naim system.
...do not buy tweaky components from manufacturers that require the use of their proprietary speaker cables and interconnects for best performance. Avoid manufacturers that try to lock you into their proprietary line of accessories.
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