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Q I have been looking at the California Audio Labs CL-5 & CL-10 and noticed that the CL-10 has a 20-bit D/A converter and the CL-5 has a 1 bit D/A converter with 32x oversampling. What exactly does this mean and is the 1 bit converter worth the money (CL-5 costs $995US)?
A A
single bit converter stacks amplitude of a single device, while
a multi-bit stacks the amplitude (or lack of amplitude) of multiple
devices. This generally translates into better amplitude linearity
with single-bit converters since proportional tolerances between
multiple devices can vary, while a single device is inherently
identical to itself, and hence perfect in that regard. This doesn't
mean that single-bit machines are
always better. Multi-bit DACs can have good amplitude linearity,
but require very close tolerances and hence, necessarily cost
more. Also, jitter, generated by a number of sources, affects
performance in the time domain, and inadvertantly, amplitude response.
In addition, single-bit converters generate more RF hash than
multi-bit converters, and tend to require more elaborate reconstruction
filters at the DAC output. What they seem to be doing with the
high 32x oversampling rate is using a digital filter to move artifacts
even higher than the standard 8x oversampling filter, so that
they can make the analog filter that follows more effective without
adversely affecting the audible range. Exactly how well these
two compare on a technical scheme, we can't say, given the information
since we don't know the jitter performance right before D/A conversion
(the only place it matters, not to say that upstream factors can't
affect this), DAC amplitude linearity, or anything about the reconstruction
filters themselves. Generally, though, I've found that single-bit
players tended to be the best bet for models under $1,000 US,
due perhaps to the high cost of good multi-bit converters. I haven't
heard those specific players yet, so I can't make a recommendation.
What I can recommend is that you take into account any features
you might want, ease of use, and when you whittle down a small
group of players that fit your functional requirements, aesthetic
taste, and budget, you take them all home for a test drive, keeping
in mind to adjust the volume control to compensate for different
output levels.
Q In
your Recommended Home Theater Systems section of your website,
you recommend the Yamaha RX-V992 receiver and the Carver AV-705
5 Channel amp. Does this mean the amp in the Yamaha would sit
idle? Since the signal is being outputted via pre-outs, does
this mean the sound (by using the Carver) is significantly better
and/or just more power for those with bigger rooms. Wouldn't it
be better to just get a preamp with an AC-3 processor (assuming
you don't care for the numerous DSP modes)?
A Because
mass market products are made in such large quantities, you get
excellent value for the money. Preamp/processors are not made
in such large numbers, and so, they are more expensive than receivers
even though receivers have amplifiers built-in. The preamplifier
and processor sections of most receivers are really quite good,
and they have lots of features, so it is very cost effective to
put a receiver together with a five-channel outboard power amplifier,
even though the power amplifiers in the receiver will be idle.
Home theater system # 1 in the recommended systems page is designed
for modest budgets. We will be preparing other systems that include
high performance preamp/processors that cost more, and do offer
better sound than the preamp/processors in receivers. We will
also be modifying system # 1 to include one of the newer receivers
that have DD and DTS processing built-in, rather than just DD.
Our intention is to keep the recommended systems up to date, so
that they always have components that are currently still available.
Also, each recommended system will stay within the same budget,
so that you can go back to it and see what upgrades might be there.
Q I
have a hard time deciding whether I should choose the GTA SE-40
single-ended class A amp (40 watts/ch) or the GTA SE-100 push-pulll
class AB amp (100watts/ch) as an outboard front channel amp for
my DSP-A1. I love the warm sound of a tube amp in music listening
but am also watching a lot of DVD movies at "moderate"
level.
A I
would suggest getting the class A, single ended amplifier because
it will distort at even-ordered harmonics, and the distortion
will not bother your ears at all. Also, 40 watts goes a long way,
particularly with a good class A amplifier, and with most of the
sound coming from the center channel when watching movies, the
DSP-A1's amplifiers will be doing most of the work.
Q If
a DVD player has an optical digital output does that make it DTS
ouput compatible? Or is there something else in addition to the
optical output that makes a DVD player DTS compatible?
A The
output jack, whether it is coaxial or optical, is not the factor
which makes it a DTS output. It is the internal DVD player circuitry
which has to be able to recognize the DTS "flag" on
the DVD, telling the player that the disc has DTS sound, and to
output the DTS digital bitstream to whatever type of jack the
player has. The current issue of DTS compatible DVD players have
stickers on the front stating that they are DTS output compatible.
Probably within a year, all the players will output DTS, but right
now, you need to look for the sticker on the front before buying
the player.
Q Am
I correct in assuming that if a DVD contains THX, DTS or Dolby
Digital 5.1 encoded audio, that an optical connection from the
DVD player will pass that audio information to a separate decoder
unchanged leaving the external decoder to figure out what to do
with it? If not, how can I be assured that the DVD player I purchase
can send all formats to an external decoder unchanged? A way
of looking at the technical specs for sampling rate, # of bits
etc. would be helpful.
A All
DVD players will handle THX and DD, and will output the DD digital
bitstream via the optical or coaxial digital ouput jack. They
will also play DTS DVDs, outputting the DTS bitstream through
those same jacks to the decoder. For DTS DVDs, you need to look
for that DTS digital out sticker on the DVD player that I mentioned
in the question/answer above. Also, some of the DVD players with
DTS DVD compatibility need to have the DTS output turned on from
the DVD setup menu. Otherwise, the DTS DVD will deliver the video,
but the DTS sound does not work, and it can be very frustrating
if you don't know the DTS output is factory set to be off.
Q Why
is it better to have a wide bandwidth in power amplifiers, even
though the audible bandwidth extends only to 20 Khz?
A The
bandwidth is usually defined as the extent of the frequency response
where it is down by 3 dB. With the drop in frequency response
comes phase shift, meaning that the waveform is not where it should
be in the time sequence. The position of high frequency harmonics
in the music end up not quite in the right spot with respect to
the lower frequency fundamentals. It can result in the perception
of a rolled off high end. This starts occurring long before the
3 dB down point. So, by having a wide bandwidth, the phase shift
occurs in a region that is not audible. A bandwidth of at least
100 kHz or so is desirable to keep the phase shift away from the
20 kHz region. A bandwidth of 300 kHz and above usually means
that the amplifier is so stable at high frequencies, no bandwidth
limiting components (inductors) are in the output signal path.
This does not mean every amplifier with a bandwidth of 100 kHz
or less will not sound very good because it has an inductor in
the output path. We are talking about good solid equipment vs.
very high performance equipment. By putting an inductor in the
output path of an amplifier that has limited stability at high
frequencies, a designer makes the amplifier compatible with the
majority of speaker loads, so that high frequency oscillation
does not happen.
Q As
a person who only buys a new receiver every ten years or so, I
want to do it right. Had I purchased one last year, I would have
missed out on DTS. Question: If I purchase a new receiver
with DD and DTS, will I be at least even with the "curve",
or is there something else out there that will make one of the
new Sony's obsolete in the next year or two? I know I can't wait
forever to buy and that technology keeps advancing and that new
formats come and go, but...HELP! Last year I would have missed
out on DTS. What will I miss out on next year?
A DD
and DTS are about the end of it for movie sound tracks. HDCD is
a CD format that some receivers may start decoding, but you can
play those CDs even if you don't have an HDCD decoder. DVDs with
24 bit 96 kHz two-channel stereo music are becoming available,
and the new DVD players will decode them, outputting the two channel
analog signal, so you don't have to worry about that in your receiver.
There may be a new two channel stereo format that uses even higher
bit rates, but decoding will be built into players once that format
is finalized. All in all, now is an OK time to go ahead and get
your new receiver.
Q Today
I auditioned a couple of receivers, Yamaha's RX-V793 and Nakamichi's
AV-1s. The Yamaha has tons of DSP modes and 80 watts to all 5
channels. The Nakamichi, on the other hand has 120 watts per side
in stereo, and 100 watts across the front with 50 watts in back
in surround. I will not be buying a DVD player for a while, so
I'm not sure I need the built in AC-3, plus who knows what will
happen with DTS. In a head-to-head comparison there was a significant
difference in stereo, in favour of the Nak. If this is any indication,
I'm sure the results would be similar in Pro Logic. Will the
50 watts in rear compared to 80 watts make a difference, after
all how loud can you tolerate a 2 hour movie? I'm now leaning
towards the AV-1s because it will accept any 5.1 format through
a decoder. Incidentally the 793 and AV-1s are about the same price.
Do I pay for features or amplifier quality?
A It
really depends on two things. One is how far down the road you
will be buying a DVD player. The second is the relative amount
of time you spend listening to two channel stereo vs. watching
movies. Once the signal is decoded into Pro Logic, sound quality
differences are less noticeable. If you use the system mostly
for CDs, then get the Nakamichi. On the other hand, Yamaha has
just announced the RX-V795 which has DD and DTS built-in, 80 watts
to all channels, pre-in jacks and pre-out jacks, which means you
could add a better power amplifier later. The 795 lists for $799
and should be available pretty soon. This last option is the one
I would go for, since I could build the system with added components
and not have to put anything away in the closet.