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Confused about connections

 

New member
Username: Gaust

Post Number: 1
Registered: Nov-04
I'll start with some background - I have a Marantz SR5300 AV receiver/amplifier with which I have been using a DVD player connected via a digital coaxial to play CDs with pleasant results. However I have recently changed my DVD player from a Wharfedale which sounded really nice to a pioneer which sounded less nice. I now have a few questions which it would be really helpful is someone could answer

1. Why do these two DVD players sound different when connected through the digital coaxial cable (and therefore presumably using the amplfiers DACs)?

2. Due to the difference in sound quality I was considering buying a separate CD player (something like an NAD 521BEE or a Cambridge Azur 640C is the budget will stretch). However I have read that any input you feed into an AV amplifier goes through the amplifiers DACs - so would this negate the point of buying an expensive CD player? Or would it sound better if conncted through the analogue inputs?

3. Would I be better off just saving up and buying a separate CD player and stereo amp to avoid these problems?

Thanks in advance for any replies / information that you can give me - I have managed to get myself really confused over the last couple of days!!
 

Anonymous
 
Hi there,

I, too, have had the same experience as you. I had two different DVD players on hand, both quite cheap. Connecting them to my NAD T742 receiver sounds different! I was told that besides DAC, there are other factors which determines the ultimate outcome of sound, though I don't know the details. In my mind, probably somewhere in the process of reading/sending digital signal makes the difference.

I think if you indeed buy a higher end dedicated CD player, you would connect through analog output of the player, thus bypassing the DAC in the receiver.
 

Unregistered guest
i need a wiring diagram for a clarion cd player going into a 94 ford explorer
 

Silver Member
Username: Edison

Glendale, CA US

Post Number: 560
Registered: Dec-03
Knapper,

Post it on "Car audio"

If you take it to any car audio shop, you can get the info.
 

Silver Member
Username: Frank_abela

Berkshire UK

Post Number: 154
Registered: Sep-04
Hi guys,

It's odd isn't it? Digital is just digital isn't it? A sequence of 1's and 0's. They should all be the same - and yet they aren't. Nobody can claim they have a complete handle on why different transports sound different - we just agree that they do. It is known that one of the main contributors to the sound change is jitter. The interface you use between the transport (I'll call it that to differentiate that you're using the player as a transport) and AV amp differs depending on whether you're using coax or optical. If you use coax, you use a 75 ohm cable, usually terminated by RCA plugs. This is connected to what is called the Sony/Philips Digital InterFace or S/PDIF. S/PDIF buffers the output of the transport before squirting it down to the external device (in this case the AV amp). The buffer introduces jitter, microscopically small changes in the timing of the signal usually measured in picoseconds.

Now in the case of optical connections, you have even more problems. Not only do you have the buffering, but also the conversion process to light. Then there are the very dodgy connectors (toslink) which vary considerably in quality and tolerance, introducing yet more jitter.

Jitter is known to vary from about 75 psecs up to 250 or so. The higher the number the worse the sound quality. So this is one possible reason for the difference in transports.

But it's not the only one. The Chord DAC64 buffers and reclocks all signals internally. This is meant to make it independant of transport and any ol' transport should sound the same provided the buffer is switched on. But they don't. Different transports sound different. Maybe it's becaus of the interconnect? The Chord uses BNC connectors instead of RCAs. BNCs guarantee the 75 ohm value of the interconnect, and yet it sounds different. In fact, different interconnects sound different!

So there you go.

Now, on your second question Jonathan. A CD player only goes through the AV amp's DAC if you attach it via the digital output of the player to the digital input of the AV amp. If you chose to connect the analogue outputs of the CD/DVD player to an analogue input on the AV amp, you would not go through the DACs. That said, you will probably still go through the DSP part of the AV amp which would give you Dolby Prologic, Hall, Concert and all those other effects which I generally dislike. In my view the most musical result is usually with the effects switched off and using the analogue outputs of the disc player. You often get better separation by going via the AV amp's DACs, but it loses out in terms of cohesion and timing.

Generally, if you save up for a good CD player (such as the C542) and stereo amp, you should get a better musical result, but you need to match the stereo amp carefully to make sure it doesn't change the overall presentation from the AV amp too much. Also, in order to make life simpler it would be good to find a stereo amp that has a unity gain feature on one of its inputs. The unity gain feature makes that input act as a straight power amp independant of the volume control on the stereo amp. Therefore in practice, you'd simply change the stereo amp to that AV input and use the Marantz as the main volume control when playing DVDs. When playing CD's, you'd switch to CD on the stereo amp and use the volume on that amp only.

That said, try to keep saving up so you can afford a better quality pair of stereo separates. So if you could wait and eventually extend the budget to something like an Arcam CD73T and an Arcam A90, then you would get much better CD reproduction and also improved surround sound due to the improved resolution of the A90's power amp.

I hope this helps!

Regards,
Frank.
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