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RE: Ping Charles Hansen - Integrated amp question

Posted by Charles Hansen (M) on July 3, 2012 at 02:15:59

In Reply to: Ping Charles Hansen - Integrated amp question posted by fwestern753 on July 1, 2012 at 08:50:53:

There are lots of possible variations on combining separate functions into one box. Some make more sense to me than others. In the old days receivers were quite popular, but now radio is kind of a dead medium. And of course no receiver could ever match the audio performance of good separate components.

(I've always been tempted to make an FM tuner, but it's hard to make anything of quality in the US for less than $2000 or $3000. By "quality" I mean discrete balanced circuits. For that much money most people would expect incredible RF performance and that is something I currently don't know that much about. The thing that keeps me from learning RF design and doing a tuner anyway is the dearth of good FM stations and the ever-impending threat of analog FM being replaced altogether by some silly compressed digital format. And remember that the Marantz 10B tuner is what drove the original company to near bankruptcy and forced Saul to sell it to Superscope, who basically ruined everything.)

Back to your original question. I think that putting too many things into one box (eg, phono stage, DAC, preamp, and power amp) would lead to a product that would be relatively expensive *and* degrade the overall performance. Amplifying microvolt level MC phono signals in a box that is also delivering tens of amperes to loudspeakers is not conducive to high performance. Similarly, putting complex digital circuitry in the same box with analog circuitry is going to cause problems. The RFI from the digital circuits is going to contaminate the analog signals.

So to my way of thinking the best route to reducing the overall number of boxes in your system is an integrated amp (combining the two analog components into one box) and then a separate box for the digital (either a disc player or a DAC). But even putting a phono stage into an integrated is problematic. Although everything in the box is still purely analog signals, just the problem of having a huge power transformer for the amp section is going to make it difficult to avoid inducing hum into a phono stage with 60 dB or 70 dB of gain. That gain is measured at 1 kHz, and the RIAA curve will create an additional 20 dB of gain at low frequencies. This means you are looking at at least 80 dB of gain at 50/60 Hz (we have to sell world-wide), which is a factor of 10,000 times! It's hard enough to put a small, super-shielded power transformer in the same box as a high-gain phono circuit, but just about impossible with a huge transformer required for a power amp. Toroidal transformers tend to have less stray magnetic fields than E-I (square) transformers, but in my opinion they don't sound as good. A toroidal transformer generally has a really wide bandwidth that couples the RFI on the power line into the audio circuitry.

Our preamps from the '90s (the K-1 and K-3) had phono card options, but to avoid problems with hum had external power supply boxes. So you end up cutting off your nose to spite your face, because you still end up with two boxes. This kind of reminds me of a product that Krell announced in the '90s, a two-box power amp called the Altair. Instead of the using one box for each channel (ie, monoblocks), it had an external power supply box and another box for both audio channels. This actually makes a lot of sense from a performance standpoint, but is unconventional enough that it probably wouldn't sell very well. (I never actually saw one, so it may have never gone into production.)

Now that digital is the dominant source for most audiophiles, we only offer phono stages as separate components. The way I figure it, people into turntables these days are a dedicated bunch and really want to get the most performance possible. After all a good 'table, arm, and cartridge is going to cost at least $2,000 and more like $5,000 to $20,000 for something really nice. To make a phono stage in the $1,000 range means it has to be single-ended only and use IC's. In my opinion this won't give the level of performance that we want to offer in our products.

I think that an integrated amp makes the most sense for combining two functions into one box. One could make a case for combining a DAC (ie, a digital preamp) with an analog preamp and then having a separate power amp but to me this is much more of a performance compromise than having one box for digital and one for analog. I think that combining the volume function with a DAC can make a lot of sense for an all-digital system, but not so much if one has any analog sources. Obviously at least one of the components must have a volume function, but to my way of thinking the best place to put it if you are combining boxes is with the power amp. Then one is not limited to a digital-source-only system when going for maximum performance.

But there is probably a big enough customer base for digital-source-only systems that some day we may build a DAC with a volume control. One big advantage of doing this is that one can make a high quality volume control for significantly less cost. The reason is that a purely digital volume control is practically free, but it degrades the sound quality more and more as the volume is reduced. But with only digital sources, one could make a hybrid volume control. A good approach would be to have (say) six small (eg, 1 dB steps) digitally. Then the maximum degradation would only be one bit. In a 24-bit system this would still leave 23 bits of performance, which is more than enough. (Any real-world system is limited to only 20 or *maybe* 21 bits of resolution.) Then the analog volume control would only need coarse steps of 6 dB. This means a 12-position switch would be more than enough, and that is a *lot* cheaper than (for example) the 60-position switch we use in our KX-R analog preamp.

Another problem with putting too many functions into one box is the lack of ability to upgrade. For example, Linn makes some boxes that have everything in them but the speakers. This is a nice solution for a less-than-maximum performance system, such as a second system for the bedroom or office. But then there are severe price constraints. People might pay $2,000 or $3,000 for a relatively limited performance system with no way to upgrade over time, but not a lot more than that. Again that means using single-ended circuitry, IC's, and possibly class-D power amps. These are all things that don't appeal to me. That doesn't mean that some company shouldn't make them or that customers shouldn't buy them. It's just not the approach that we like to take. It's kind of like tubed products. They can sound great and all, but they're not something that I particularly want to own, or design, or manufacture. But it all works out because there are other companies that *do* take that approach and meet the needs of customers that want to go in that direction. No company can be all things to all people, and one needs to decide on the approach that is "comfortable" to them.

I guess the bottom line is that to me, what you are asking for is not really an "integrated amp" so much as an "integrated system". We will surely offer more integrated amps in the future besides our current AX-7 and quite possibly a DAC with a volume control for digital-source-only systems, but I don't foresee us ever building an integrated system. A very long-winded answer, but I hope that helps you understand where we are coming from.

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