Q&A # 105 - March 2, 1999

Staff

Q Why do Dolby and DTS use such low bit rates when DVD has so much space?

A The Dolby Digital format is limited to 640 kilobits per second, and usually is performed at 384 or 448. Although DTS is capable of very high bit rates, it sticks to 1.536 megabits per second because copyright issues would have to be addressed if it used higher rates. When the consumer format approaches the quality of the master recording, producers get nervous.

Q In Q&A 104 you state once again that you believe a good CD player is better than a similarly priced DVD player for playing CDs. I don't have a good CD player but I do have a Pioneer CLD-D701 laserdisc player, which I previously used for playing CDs until I bought a Toshiba SD-3107 DVD player. Although the Pioneer laserdisc player is a much older unit, it seems to sound smoother than the Toshiba DVD player when playing some (but not all) CDs. Is this my imagination? Which of my two playback devices would you recommend using for CDs?

A A laserdisc player will play CDs better than a DVD player, but still not quite as good as a dedicated CD player. The reason is that the laserdisc player uses the same laser as a CD player, but it has quite a bit of jitter, perhaps in part because of the large mechanism that is used to play the discs. It has to perform double duty for 5" CDs and 12" LDs. The problem with DVD players is the laser is a shorter wavelength and smaller in diameter than the one used for CDs, and this results in a mediocre sound. Right now it is difficult to diagnose as to what the exact cause is, when "bits is bits" as they say. I suspect some form of jitter because of the small laser beam, but by the time we have it all figured out, the manufacturers will probably have a design that actually does read all types of discs with high resolution and low jitter. Anyway, use the laserdisc player for your CDs rather than the DVD player.

Q In your most recent Q&A issue you make a statement that there are no high performance CD changers presently made by high end companies. I have owned a Proceed music library for the past few years and I feel it is of high quality, it also allows good access and alpha-numeric display of song and title. New PC based software has improved this feature considerably. At my office I have a CAL unit which I feel is of fairly good quality. And the plethora of good and affordable DACs on the market make the so-so changers attractive. So the round and about question is: Have you had an opportunity to hear the CAL units? Would not the nice Mega changers by SONY augmented with a nice DAC have decent sound? My Theta TLC makes very little difference whatsoever.

A No, we have not tested the models you mentioned, but we will sure try to get them for review. The idea of using a basic CD carousel as a transport, with a quality DAC, is a good one. It would be interesting to see how an inexpensive carousel performs. If anyone has a setup that they are really pleased with, let us know and we will post it.

Q I find tube amplification much more transparent, much smoother, and more enjoyable. Wish I didn't like them, but my ears hear a real difference. So my question is what components can I use to get a tube sound out of an HT multichannel system? Carver's Sunfire has a tube-based preamp. Is this a possibility? Does it provide enough channels and would it require a tube amplifier to reap the benefits? What about decoding a DD or DTS signal? Would tube amplification enhance that kind of audio? Give specific products, brands, and manufacturer names when possible.

A At the 1998 CES in Las Vegas, I saw a five-channel tube power amplifier for home theater. It is made in Italy and costs $5,000 for 35 watts per channel. That's the bad news. The good news is that you can get tube sound in home theater simply by using a two channel tube preamplifier for the front left/right channels. The tube preamp is connected as follows. Using a surround sound receiver with pre-ins and pre-outs, connect the front left/right pre-out to a pair of inputs on the tube preamplifier, and connect the tube preamplifier outputs to the main ins on the receiver or to an outboard power amplifier. You can use a tube power amplifier for the front left/right channels if you want, but tube power amps are REALLY expensive, much more so than tube preamps. I have found that using a tube preamplifier and solid state power amplifiers is a nice combination, with the warm tube sound, but with plenty of power for the speakers, and without breaking the bank. One of my favorite tube preamplfiers is the Audio Electronic Supply AE-1 which we reviewed some time ago.

Q You mentioned using the same floorstanding speakers in the rear as in the front with surround sound. Is it necessary to have large floorstanding speakers with DD and DTS?

A No, what we are saying is that it is now important to have the same speakers in the rear as in the front, because all the channels are full spectrum. Bookshelf speakers are fine, but use the same models in the front and rear. The only adjustment you would need to make when using bookshelf speakers is to increase the low pass crossover frequency in the subwoofer. For floorstanding speakers, it should be around 50 Hz, and with bookshelf speakers, around 70 Hz.

Q I am going to purchase a home theater system which will include B&W 602s for the front and rear speakers, B&W center speaker, and a Velodyne FSR12 subwoofer. My question to you is at what height do I put the rear speakers at and do I face them in towards the middle of the room?
A Assuming that your new system will have Dolby Digital and DTS, put your rear 602s in the same relative position as the front 602s. In other words, put them on speaker stands and facing slightly inwards ("toed in") if that is what you are doing with the front speakers. This will be especially useful when you play 5.1 audio discs. There will probably be recommendations from other websites, printed magazines, and dealers to place the rear speakers as you would have in the Pro Logic days, but those are out of date habits. DD and DTS sound best when the front and rear speakers are the same models, and in the same relative positions, IMHO.

Q This is in regards to a letter sent to your Q&A and answered January 19, 1999 about possible problems that may be experienced using US video equipment in countries that have a PAL system. Living in Australia, we use 220 - 240 volts / 50Hz equipment, and I run a Pioneer DVL-700 Laserdisc/DVD player which was made for the US market only and can only be imported personally as it does not comply with Australian standards. The only thing needed is a "step down" transformer (downconverter) which takes the standard 220 - 240 volts / 50Hz signal and turns it into 120 volts / 60Hz signal. Of course you need a TV that can show NTSC. Remember, the transformer also has to change the frequency, otherwise you can get anything from flickering frames, black and white pictures, or in most cases nothing at all. It is pretty much the same with all other US video equipment. Another option, as the reader may already know, is to buy an imported or international version of whatever video equipment he intends to use as they generally have a switch/dial on the back that does all the hard work for you. This should be the same for Europe, as it is the standard on which ours is based, except France and a few former eastern block countries which run SECAM. To add a little more confusion to the issue, don't assume that because a country runs PAL, it will always work. I had this experience in Brazil which runs PAL, but it's called PAL-M I think which runs 120 volts / 50Hz. Anyway, the result of running a Sony Play Station bought in Europe (much cheaper than the local version) with only a "step down" transformer with the right frequency gave a black and white picture. The irony is that they were essentially both PAL systems. Hope all this trivia helps in some way.

A Thank you for your input. This is just the kind of info that will help a lot of people who are moving between countries and taking some video equipment with them.

Q I have been utilizing the "Sub-out" on my Denon 3200 to drive two small Yamaha subwoofers by using a "Y" connecter. I just added a Clark Transducer (LOTS of fun, by the way) powered by an Adcom amp and I now have a "Y" followed by another "Y" to feed the low effects signal to three separate amps. Am I creating a dangerous situation for my Denon and if so is there a reasonable solution?

A As long as the input impedance on all three items (the two subs and the Adcom) is at least 30 kOhms (each), you should be OK. They are probably around 47 kOhms each, which is a typical input impedance. You don't want the input impedance that the preamplifier output "sees" to drop below 10 kOhms. Otherwise, your preamp section might not have enough power supply strength to maintain the proper voltage at the output. This would be manifested by distortion in the sound. If you were using something like a Balanced Audio VK-5i preamp, which has an enormous power supply, it would work with just about any input impedance on the power amplifiers, but mass market receivers don't have that kind of power supply (of course, neither are they $4,500).

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