Jon.Fairbairn@computer-lab.cambridge.ac.uk (Jon Fairbairn) (01/29/91)
No one has mentioned the idea of using a digital crossover. In theory this could solve all the problems of phase and slope. Meridian have them in their D6000 speakers (which have digital inputs only, and cost about 7000pounds sterling), but don't plan to sell separate crossovers "in the forseeable future," which is a bit of a shame. Does anyone know of any company that makes such a beast?
chowkwan@priam.usc.edu (Raymond Chowkwanyun) (01/30/91)
In article <9199@uwm.edu> Jon.Fairbairn@computer-lab.cambridge.ac.uk (Jon Fairbairn) writes: >No one has mentioned the idea of using a digital crossover. >In theory this could solve all the problems of phase and slope. Meridian >have them in their D6000 speakers (which have digital inputs only, >and cost about 7000pounds sterling), but don't plan to sell separate >crossovers "in the forseeable future," which is a bit of a shame. > >Does anyone know of any company that makes such a beast? Muse makes a crossover that they tailor to the particular speaker you use. It's designed to be used in conjuction with their subwoofer and amp but they'll sell it to you separately. It's not digital but it does have adjustments for phase and slope which they set. I met the designer in a store when he was taking measurements to configure the crossover for the Hales Signature. I mentioned that I'd be interested in a board that would permit bi-amping of 801's. He said they'd certainly try to respond to this kind of specific customer demand. (He already has a board configured for subwoofing the 801). Why not drop him a line? It couldn't hurt. Sorry, no name and address. Muse has been around for several years making professional type equipment. More recently, they've entered the consumer market with a 100 watt amp aimed squarely at the PS100. The Sterephile review found it had excellent bass but was a bit rough at the higher frequencies. BTW, Jon, how about disclosing your vinyl sources? Name, address, and fax number would be appreciated. -- ray
leconte@irisa.fr (Thierry Leconte) (01/30/91)
>From article <9199@uwm.edu>, by Jon.Fairbairn@computer-lab.cambridge.ac.uk (Jon Fairbairn): > No one has mentioned the idea of using a digital crossover. > In theory this could solve all the problems of phase and slope. Well It's a good idea if all your sources are digital. If not you have to convert from analog to digital before the digital crossover then to convert from digital to analog after...not a big win. And how about a true digital amp? Now with bitstream technologie digital to analog convertion consist in the modulation of density or width of a high frequency(>> 1Mhz) pulse signal. Why not modulate a high level ouput signal which will be send directly to the speakers ? (in fact a sort of digital class D amp) I think that a simple passive output filter will suffice. Any comment ? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | Thierry LECONTE | , ,--- ,--- | | INRIA/IRISA | / / /--- | | Campus de Beaulieu | (___ (___ (___ | | 35042 RENNES CEDEX | | | FRANCE | (INRIA/BULL) | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | Tel: 99 36 20 00 e-mail: Thierry.Leconte@irisa.fr | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
peter@ames.arc.nasa.gov (Peter Tapscott) (02/07/91)
In article <9319@uwm.edu> mike@brl.mil (Michael John Muuss) writes: > >In article <9230@uwm.edu>, leconte@irisa.fr (Thierry Leconte) writes: >|> And how about a true digital amp? >|> Why not modulate a high level ouput signal which will >|> be send directly to the speakers ? >|> I think that a simple passive output filter will suffice. >|> > >This has actually been done as long ago as 1979. Infinity produced >a 1-bit switching amplifier (code-named the "SWAMP") that operated >at a multi-megahertz rate. 200 W/ch. > Best, > -Mike Even before '79, a friend made one. We were in grad school at Syracuse, and had access to pretty nice labs and instrumentation. We used to make a lot of amplifiers, mostly hybrids like op amps driving class-A current amps, phono-preamps that sounded better than those in our amps, etc. We wondered why switching power supply concepts couldn't be applied to audio amps, so one of the more clever among us decided to design one. (Steve Zahorian, where are you now?) He used a resonant circuit to create the switching frequency, as was common on switching power supplies of the time. This requires some pretty clever use of feedback theory, and the amp itself was the first application I knew of sampled data feedback systems. It provided about 40 watts, but needed only a couple of small pieces of aluminum sheet for heatsinks since the output transistors operated in digital mode. The simple passive output filter that Thierry suggests was a handmade 2" long by 1/2" diameter inductor. When Infinity came out with theirs, I said "Oh, Rats, now everyone will be using switching power amps, and I have missed the window on the market." So I started taking computer classes, and the rest is misery.... er ..., I mean history. They still seem to make sense. 200W switching power supplies are quite common. Rather than having a power supply and a switching amp (like Steve's above), doesn't it make sense to have the switching on the line (mains to UK readers) side, like a switching power supply? -- |----------------------------------------------------------------------| | peter@versatc.VERSATEC.COM -OR- {ames|apple|sun}!versatc!peter| | Peter Tapscott - Xerox Engineering Systems, Versatec Products | | 2805 Bowers Avenue, Santa Clara, Calif (408)982-4235 |