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Author Topic: What hapenned to HiFi  (Read 16377 times)

Offline LeeE

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What hapenned to HiFi
« Reply #25 on: 24/04/2009 10:46:16 »
The heavy loudspeaker cone might limit the frequency response (though it shouldn't) but it won't do anything to regain the data that was lost when a signal was comressed from the range of human hearing (about 120dB which is equivalent to roughly 20 bits (assuming no oversampling and dithering for those who car about such things)) down to 16 bit (equivalent to about 96 dB).

BTW, LeeE,  at least some DC players had digital outputs and so I presume that there must be something with a digital input. IIRC there was even an optical version called "Tosser" or something.

Bit of an odd, and in the UK at least, unmarketable name.

Yeah, many CD players (and I guess high quality DAB tuners too now) have digital outputs - these usually get fed in to a stand-alone DAC.  Like I said, I imagine that some people have made amplifiers with DAC input stages but most exotic HiFi comes as 'separates', allowing different things to be mixed and matched.  This even extends to stand-alone power supplies for some things like turntables and pre & power amplifiers.

The problem with building a DAC in to an amplifier is that it limits your options quite a bit, not only regarding the choice of DAC but how you amplify your system.  Most people who can afford to will use an active crossover, between the pre & power amplifiers.  This means bypassing the passive crossover inside the loudspeakers (if fitted), which soaks up quite a bit of power and introduces additional components in the signal chain, and then directly driving each separate speaker driver with a dedicated power amp channel.  You can't do this with a single stereo integrated amplifier though, so you need to go the 'separates' route.

This page shows one manufacturer's range of 'separates' components - note the number of separate PSUs, and they actually make a PSU for someone else's turntable too (shown in the analogue section).  No separate DACs there though, which surprises me a bit.

http://www.naim-audio.com/products/products.html
 

Offline graham.d

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What hapenned to HiFi
« Reply #26 on: 25/04/2009 00:13:27 »
Oh dear this is a huge subject. A few points; Most DACs that convert the digital data into analog are sigma delta types. Some of these output a single bit stream at a much oversampled frequency (a few MHz) where the pulse density represents the analogue information. On low cost systems and battery based systems (especially for MP3 players) this can be fed straight into a speaker or headphone. The output is the same as a class-D amplifier and is very efficient and the quality can be quite high. The speaker or headphone itself acts as the reconstruction filter.

Speakers are definitely a weak link. As Soulsurfer said, a major problem is Intermodulation distortion. This results from pushing a wide range of frequencies from one surface. You can think of it as the low frequency moving the cone back and forth and the high frequency doing this as well on the moving cone. The high frequency will get doppler shifted back and forth at the low frequency rate and frequency modulate the higher frequency. Effectively any number of frequencies can be doing this and they all will produce an "FM" spectrum of intermodulation products that would not be present in the original recording. The ear is sensitive to this. The problem is worst with the small long movement bass speakers where the amount of cone movement exacerbates the problem. Multiple speakers, each dealing with its own band of frequencies, helps quite a bit. There are no easy ways to eliminate this, although it can be reduced. One design that does avoid the problem, at least in a high frequency unit (a tweeter), was the ionophone where a stream of ionised air was modulated, which avoids the IM distortion. They never caught on much and I never heard one. Did you come across these at EMI, SS?

I have to say that I am also impressed with the quality now available from relatively cheap and amazingly small speakers that are around now. They may not be HiFi but they are better than many large units that used to be sold as HiFi in the past. The trouble is, as I've got older, I think my ears cause distortion if the music I am listening to is too loud, especially with live music where the distortion probably is not coming from the band or orchestra. It actually sounds like what I used to recognise as IM distortion too. I guess expensive speakers would be wasted on me now.
 

lyner

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What hapenned to HiFi
« Reply #27 on: 25/04/2009 00:27:33 »
If they're big enough you can also rest your beer glass on them - two birds with one stone.
 

Offline syhprum

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What hapenned to HiFi
« Reply #28 on: 25/04/2009 11:57:28 »
I am not at all or surprised to see my query removed to technology which of course is the proper home for it, I posted in P,A & C knowing that it would be viewed by a wider audience.
I much appreciate all the wise comments it has received.
 

Online Bored chemist

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What hapenned to HiFi
« Reply #29 on: 25/04/2009 16:32:33 »
"Bit of an odd, and in the UK at least, unmarketable name."

Oops, I meant toslink
 

Offline syhprum

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What hapenned to HiFi
« Reply #30 on: 25/04/2009 20:42:57 »
I was inspired by the view of a Murphys beer advert in my rear view mirror.
 

Offline roscoe

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What hapenned to HiFi
« Reply #31 on: 27/04/2009 00:32:43 »
I still have my old JBL L-19 speakers and they are excellent.
 

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What hapenned to HiFi
« Reply #31 on: 27/04/2009 00:32:43 »

 

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