Q&A # 124 - July 9, 1999

Staff

Q I have a Pioneer DVD player (DVL-9) which specifies "96 KHz, 20 Bit DAC", My amp is a Yamaha RX-V992 which states in the manual, "All digital audio signal input jacks are applicable to the sampling frequency of 32, 44.1 & 48 KHz". Does this means that my amp is unable to fully explore the capability of this DVD player in term of digital audio? What actually will I miss out in the audio performance ? (example : playing a DVD or CD?) This Yamaha amp has the option for a listener to switch to analog inputs even though all other connections (optical digital, coaxial digital) are linked up in parallel. I choose the analog input when listening to CDs from the DVD player, where the volume of the DVD player output can be adjusted (only for analog) to 'tone down' the voices (vocal not so harsh). At the same time, I can turn up the volume of the amp. How actually does this process work ? Someone told me that I am reducing the 'gain'?

A Conventional CDs have the audio encoded at 16 bit - 44.1 kHz sampling. The audio tracks on DVDs are at 20 bit - 48 kHz sampling (DD and DTS). Since the Yamaha RX-V992 has DD decoding built-in, you can connect the digital output from your DVD player to the digital input on the 992, and the 992 will decode DD soundtracks for you. You can also play CDs on your DVD player, and the 992 will decode them from the 16/44 bitstream that comes out of your DVD player from the CDs, using that same digital connection from the DVD player. There are a few DVD audio discs out there that are 24 bit - 96 kHz sampling, but most DVD players downconvert them to 48 kHz before sending any digital bitstream through the digital output jack of the DVD player. In this case, it is better to use the stereo analog outputs from the DVD player to your 992, since the DVD player will utilize most of the capability of the 24/96, truncating the least significant bits (LSB), meaning that the data in the lowest 4 of the 24 bits will be lost (the ultrafine detail). However, for regular CDs and DVDs, you will get everything that is there, so don't be concerned.

For your reduced harshness setting, I suspect the DVD player is processing the bitstream to reduce the output in the 6 kHz range. This is done mathematically by taking certain samples and dividing them by a number. This results in the bitstream now having samples with new values, and then the DAC converts them to analog audio. For digital volume controls that affect the entire signal, all of the samples are divided by a number to reduce their value. If the number is greater than 1, the new values (representing voltages, or loudness) are now lower, and this means lower volume. If only certain samples are divided, then a certain part of the spectrum (e.g., around 6 kHz) will be reduced in volume. This manipulation of the bitstream values by dividing, multiplying, adding, and subtracting the original numbers, is the basis of Digital Signal Processing (DSP) that gives us all those "Modes" in receivers, such as "Hall", "Stadium", "Sci-Fi Spectacular", etc.

Q  I purchased a used Carver receiver a few years ago, and the seller neglected to provide me with the remote. Now that the Carver corporation seems to have vanished, is there any way I can find a suitable replacement for the factory remote?

A I would suggest buying a universal learning remote control. You have to be careful when shopping for remotes, because "learning" is different than "programmable".  A learning remote allows you to put another remote control in front of the learning remote, and when you press a button on the other remote, the learning remote receives the signal and "learns" it, so that you can execute the learned command. A programmable remote does not necessarily learn commands. The programming feature may just mean that you can teach it some macros. So, get the learning remote, and then find someone with a Carver receiver, and use your new remote to learn the commands from the other Carver remote. Alternatively, you can contact Sunfire Corporation (Bob Carver started Carver Corporation and Sunfire) and ask them if Carver's remote commands are identical to some other major brand's remote commands. In that case, all you need to do is learn the commands from that other brand's remote control (go to a hi-fi store where they sell that brand, and use a remote there).

Q I am very confused over which DVD player to get. My system currently includes Sunfire's Theater Grand Preamp which is capable of Dolby Digital and DTS. I am looking to purchase Sony's new DVP-S7700 DVD Player which is also capable of Dolby Digital and DTS. Should I purchase a DVD player with DD and DTS included even though my Sunfire Preamp already has that capability? Which unit would do the processing then? Does it even matter? What do you suggest for a DVD player? Should I get one without DD/DTS? The Theater Grand is hooked up to Sunfire's Cinema Grand with Monster cable throughout.

A Pretty much all the new DVD players will output DD and DTS digital bitstreams through their digital output jacks. However, a few DVD players have a set of six RCA jacks through which they output 5.1 analog audio (for DD, not for DTS) for those consumers who have a receiver with a set of 5.1 analog audio input jacks. Since your Sunfire will decode DD and DTS bitstreams, the set of 5.1 analog output jacks is not necessary on any DVD player that you purchase. On the other hand, you should not rule out a DVD player just because it may have this set of jacks. Select your player on the other features. If it happens to have the 5.1 jacks, you just won't be needing them. For those consumers who have a receiver with DD and DTS decoding along with a set of 5.1 analog inputs, plus a DVD player with 5.1 analog outputs, you should use the decoding in the receiver, because the DSP capabilities on receivers are usually only active when the regular inputs are used. The 5.1 inputs bypass the receiver's DSP and only use the volume control and tone controls.

Q I am currently debating purchasing a DVD player. My question is, do the analog outputs on a DVD player send a Pro Logic signal? I understand the differences between Pro Logic and DD, but I am not interested in upgrading to a digital receiver yet. Will only certain models output Pro Logic? Or only certain movies?

A On all DVD players, there are at least two outputs. One is the digital output, which can be either a coaxial RCA jack, or an optical Toslink jack (some players have both). The second is a set of two coaxial RCA jacks, which carries a stereo signal that has been downconverted from the DD track. That stereo signal can be played through a two-channel stereo system, or, using a surround sound receiver, decoded to four-channel Pro Logic (front left/center/right and rear). All DVD players will output this two-channel analog signal. When you upgrade to a DD/DTS receiver, you then add a digital cable from the DVD player to your receiver. You can keep the two-channel analog connection too, because this can be used when you are playing CDs. Otherwise, the digital output from the DVD player will send the digital bitstream to your receiver for decoding, whether it is from a DVD or CD. Some of the old movies are in mono, and in this case, you will get two-channel mono from the stereo outputs on the DVD player. The digital output will carry DD, but only two of the six (5.1) channels have any audio on them, and sometimes, just one. Using DD decoding in your receiver might give you a front left/right mono, while use of the stereo analog inputs would give you Pro Logic, decoded to the center channel speaker.

Q I have a Yamaha RX-V793, Sony 300 DVD, and MovieWorks speaker package from Cambridge Soundworks. This comes with a 12" powered sub. I've added the slave sub also. I currently hook the sub up using the left right speaker terminals. The subs crossover is set at 140 Hz. The selections for crossover frequencies are 55, 80, 100, and 140 Hz. Question 1: Should I keep this setup or connect the sub to the sub-out of the receiver? If so, where should the crossover on the sub be set? Question 2: Is it ok to set the front speaker on top of the sub?

A This depends on how your MovieWorks system is designed. If the speakers are not designed to handle low frequencies, then you should use the speaker-level inputs on the sub, and speaker-level outputs from the sub to the main speakers. If on the other hand, the other speakers can handle full range signals (even though they might not respond to the deepest signals), then use the subwoofer output jack on your receiver. Set the crossover to either 55 Hz or 80 Hz, depending on whether or not the 80 Hz setting results in boominess.

Q I just got a TEAC surround receiver recently, not real expensive. My front speakers, about 15 years old now, are Kenwood JL 760. I don't have center or subwoofer yet. I've tried cheap rear speakers, and also a pair of Bose for the rear surrounds, and there just doesn't seem to be much volume from them in any mode, Pro Logic, theater, hall, with the level up to +10 dB. I have about 45 feet of wire running to them, but I'm using 16 gauge wire (this is within the recommendations that came with the Bose for that distance). Is it the receiver itself? The front nominal ratings are 70 watts, and the rears are nominal 50 watts . . . is that what's going on? I put 8 Ohm power resistors in series with the fronts, and this helped out, getting more out of the rears relative to the fronts . . .  but is that an OK thing to do?

A Your 45 foot cables are probably the culprit. That is a LOT of wire. Putting 8 Ohm resistors in series for the front results in a 16 Ohm load there, assuming they are 8 Ohm speakers, and that is balancing out the increased impedance you have in those long rear speaker cables. Try some 6 foot cables in the rear just for a test (obviously, you will need to move them close to the front for this test), and see if this makes the volume louder in the rear speakers. If it does, you may need to either use 12 gauge cables for the rear, or get some higher efficiency and/or 4 Ohm impedance speakers for the rear. Look for an efficiency of about 92 dB/w/m or higher.

Q I recently purchased a condo in a circa 1900 brick building. All the floors are refinished wood, the majority of walls are brick - 12 to 13" thick - between my next door neighbor and myself. The down side of this is the floors. While acoustically "alive", they present a problem when trying to get rumble from a subwoofer without also getting grumble from my other "sub" (the neighbor below me)! Luckily, I don't have to worry about anyone above me! Everyone knows that bass is all about moving air, and short of hanging a Bose Cannon off the ceiling, I've run out of ideas. Do you know of any subwoofers that would benefit from an alternative placement (not using the floor as a reflective surface), or can you think of any alternative placement ideas for a "run of the mill" sub woofer?

A Your problem is not that you aren't moving enough air, but rather, you are moving the floor and the walls. They move in and out just like the cone of the subwoofer, and the other side of the floor (your neighbor's ceiling) acts like a cone in his living room. If your subwoofer has a downward firing cone, lay it on its side so that the cone faces toward the center of the room, or even perhaps upside down, so the cone faces upwards (some cones are made to sit in one position or another, so you just have to try them all and see what works). Also, you need to damp the floors and walls by placing a few heavy area carpets here and there. Place the subwoofer on one of the large carpets, or on a small one all its own. Additionally, use a couple of small artistic carpets that can serve as wall hangings. The idea is to reduce the  vibration of the wood and plaster themselves. You can do this without eliminating very much of the deep bass vibration to your ears.

Q I visit your site very often to read your reviews and the Q&A section which I find very informative. Thanks to you I have a much better perspective when making purchases and I am more equipped to solve some of the problems that I encounter in setting up. I have a problem that has been bugging me which I can't seem to figure out. Wondering if you could throw some light: When I am in DVD mode, there is a faint, vertical black line that passes across my TV screen at regular intervals of about 2 -3 seconds. I am wondering if this has to do with the fact that the speaker cables, power cords, and interconnects are crossing each other at the back of my cabinet. I don't have this problem for my LD, regular TV, or cable. My DVD is a Toshiba 2108. The video output is connected directly to the TV through an S-Video cable, and the audio output is sent via an optical cable to my Yamaha 995. I have been experimenting with my setup and discovered that the black line does not show up on my TV screen when my Yamaha 995 is off. This is strange because my S-Video line goes straight into the TV from my DVD without  passing through the amp. Does this mean that I cannot place the amp next to my TV as I am doing now? Are amps magnetically shielded and do they need to be? Why is it that I don't get the same "black/wavy line" problem with my other components, i.e., LD (using composite), and pay TV box (using S-Video) that go through the amp into the TV?

A Receivers that have digital decoding use oscillators that generate radio frequency signals (RF). They are shielded, but they are not perfect. I suspect that RF is somehow getting into the cables that eventually run to the TV, sort of like the way a ground loop works. Even though your DVD player goes directly to the TV, the 995 does connect to the TV in a roundabout way, through the audio and video cables that connect everything together. You will need to experiment to find how the RF is getting to the TV. With everything turned on and connected, and watching the black line, start disconnecting cables one at a time until the line disappears. Assuming you use a digital coax cable between the DVD player and the 995, start with that one. After you disconnect a cable, leave it disconnected before moving on to the next one (it may be a combination of cables that is causing the problem rather than a single cable). When the line finally disappears, then start reconnecting other cables until you find the combination that is causing the problem. Once you have found the source of the RF, then it is a matter of isolating it, perhaps with RF-absorbing graphite accessories that wrap around cables and snap closed (these are available through several suppliers, such as Audio Advisor, an example of such a device shown on the right). If the problem is through the digital coax between your DVD player and the 995, you could go to optical Toslink.

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