Car Stereo's CD players have - One Bit Dac's?

This might not be the right forum for this topic but I think it is relevant
to all Audiophiles.

I was researching an upgrade to my current car stereo. I spend almost
2 hours in the car each day. The sound quality of my factory car stereo
has become an issue of late.

I have built a home system of considerable cost in relationship to a modest
income because I am a music lover and It has to sound good for me to
get the most out of it.

I typically have recorded cassettes from my home system and have been
playing them in my car. The sound is warm and quite nice.

I decided that I needed the convenience of CD's in my car system
so I had an Alpine CD changer installed. I was immediately disappointed
by the digititis that I was hearing from the changer.

I went on Alpines website and discovered that except for their $3,000
head unit, all their car equipment usings one bit dacs.

My Car is a Honda and it came with a Honda Radio Cassette player made
by Alpine with a CD button for seamless integration with the Alpine
CD Changer.

I don't no why Alpine is using one bit dacs in 99.9% of their changers
and head units. But Alpine has a decent reputaion so I'm very surprise.

I was happy with the car cassette sound, but I wanted CD convenience.

Why do you need to spend $3,000 to get a Head Unit with a decent DAC
When Dac chips are dirt cheap?

Best Regards,


Gary S. Freed

 

Why do you think one-bit DACs are inherantly inferior? Perhaps there are engineers on the forum who can correct me, but I think bit count has little or no correlation with sound quality. My favorite CD player is a single-bit, 64x oversampling unit from Technics, which represented the state-of-the-art at the time, well after the ubiquitous 16-bit and 18-bit processors.

The real feature needed in a CD car unit is a delay that can handle potholes and other shocks to the car's suspension. Why this is usually featured prominently in portables but not in car players is beyond me.

 

Hi Ron

Thanks for the reply.

My question is why does the factory radio cassette player sound warmer
than the Alpine Changer. My other question is why does a top of the
line car stereo manufacturer only use a home stereo dac in their top
of the line head unit. Good DACs are a key component for Digital to
Analogue conversion and DAC chips are the least expensive part .

I feel its a given that if you are designing a CD player for a car, that
the player must have good anti-skip capabilities.

With the head unit price points that I'm talking about $500 to $900 range
consumers should be getting a much better D to A conversion and much
better transport mechanisms in the changers.

The Burr Brown 24bit/96 K series chip used in Alpines F series costs Alpine
under $40 per chip.

I still don't get it.

You can get a pretty nice home CD player for $900 with more expensive
and better parts.

My feeling is that the car audio mfgs. are gouging the consumer.

Their mark-ups and profit margins are higher.

 

Gary,
The "1 bit" nomenclature refers to the DAC architecture, namely a delta-sigma DAC. The B-B DAC in the high end unit is a "24/96", here the bit nomenclature describes the maximum word length the DAC can accept, not the architecture. Check the part number and go to Texas Instruments web site and download the application sheet on it and I'll bet you will find that it is a Delta Sigma DAC too.

Delta Sigma DACs are easier to manufacture, therefore cheaper than the older current ladder DACs which required laser trimmed resistors. Both architectures have pluses and minuses, the Delta Sigma has better low level linearity, but make more high frequency noise that has to be "shaped" into inaudibility or filtered out.

Virtually everything uses Delta-Sigmas now, equipment makers throw in that "24 bit" to confuse. There are a few that still use current ladder DACs in home equipment, and some use hybrid DACs which try to use the best of both worlds. But mostly its the "1 bit" guys now.

I doubt if in the car you can really tell the difference with road/engine noise. And $40 for a DAC chip is expensive considering everyone in the manufacturing food chain has to eat and still keep the consumer price to a reasonable level.

Cheers,
Robert

 

Robert,

Thank you for the imformative response. I was also finally able to get a phone number for Alpine yesterday and I spoke with one of their in house
Techies. He explained that the 1 bit dac is used in most of the Alpine
line but that some of their higher priced head units use a 3 bit dac which Alpine refers to the M-Series DACs. This 3 bit M DAC according to the
technician that I spoke to is more natural sounding than the one bit DAC.
The 3 bit DAC is also used in Alpines S634 Changer. But is not used in the
S630 changer. The S630 changer was recommended by Tweeter and
installed by them in my car . Without knowing that the different changers used different DACs I was immediately disappointed in the sound of the S630.
My ears are well trained and I could hear something that wasn't quite
right.
Tweeter is going to replace the S630 changer with the better changer.
The price difference is $40.

Thanks again for your reply.

Gary

 

True. My Sony CDX-C90R CD tuner has it, but they don´t make it any longer. Besides, it was a high-end device. Right now I don´t know of any other head unit that has the buffer.

But then again, if you don´t need a radio, why don´t you use a portable CD player in the car, and connect it to an external power amp in your trunk?

 

Although not an absolute rule, I too prefer the sound of the multibit DACs. I do have one of the Alpine's headunits and yes it is a bit bright. There are some car audio companies that still make multi-bit DACs such as McIntosh and Eclipse. Alpine, while still pretty good, has dropped a few pegs from their earlier days IMO. This seemed to coincide about the time they made their equipment available to the mass retailers like Best Buy versus the traditional car boutiques where Alpine was previously sold exclusively.

I think there are also some players that will accept a seperate outboard DAC through a digital output. I seem to remember a series of articles in Stereophile that featured some car audio tweaks that sounded interesting.