Q&A # 168 - March 15, 2000

Staff

Q I read your December 1999 review of the Yamaha RX-V795a and found it very informative. I have the previous incarnation, RX-V795. When I play some CDs at a slightly loud volume (above 9 o'clock on the gain control), any background hiss on the source material is (greatly) accentuated. I've even noticed this on some DVDs that I thought had sounded fairly good on my previous Pioneer receiver (e.g., Ani Difranco's performance on the Sessions at West 54th street DVD). Anyway, I was just wondering if you had experienced any excessive hiss on your Yamaha? My other relevant equipment is a Pioneer DV525 DVD player, and Paradigm Phantom main speakers. (Note: I've also tried a set of Polk speakers to the same hissy end.) Anyway, I don't generally listen to loud music, so it's not really a problem. I'm just wondering whether my receiver is defective.

A In your settings menu, check to see that the "Main Level" is set at 0 and not -10 dB. All amps hiss to one degree or another, but it should not be distracting unless you have a real quiet passage and the volume way, way up. Is the hiss still distracting during a loud passage? Try circumnavigating the built in DACs by connecting your CD player to the main left and right jacks of the 6 channel input and see if you hear a difference (but be careful with the volume as bass management will not be active).  The natural hiss in my 795a is only barely audible when there is silence in a movie that I've been watching really loud. Note that old recordings like Dire Strait's 'Love Over Gold' or Pink Floyd's 'Wish You Were Here' have a hiss all their own at any volume that is unfortunately in the recording forever. Because it is only on certain discs, I don't think there is anything wrong with your unit. Now that digital sound is the norm, when any source (CD, DVD, etc.) has some hiss, we notice it more than we used to when all sources had hiss.

Q What is the definition of High End?

A We prefer to call it High Performance. My definition of it is the point at which the product stops trying to compete on price, and focuses on competing on quality. Mass market equipment competes on price. That is why they all cost about the same, between different manufacturers, for their product range. High Performance equipment varies in price all over the place. You can spend up to $15,000 for a high performance DVD player, for example. They don't compete on price at all . . . but rather, their quality. There is no dollar cutoff amount on this term. You can buy an inexpensive set of interconnects for $5, and a high performance set for $50, which is still not very much money.

Q I would like to ask you for any advice in setting up current system. And any upgrade suggestions and/or additional units if possible. Here is what I have: Adcom Power Amp GFA-555, Adcom GSA-700 Surround Sound Processor/Amplifier, Onkyo Preamp P-304, Front Speaker: Infinity SM-215, Rear Speaker: Infinity Delta-40, PowerSub: Infinity BU-120, Toshiba DVD player 3109, Sony 27' Wega version. I am still looking for a center speaker (suggestion please).

A I would suggest just adding the Infinity CC-3 center speaker. Everything else in your system is fine.

Q 1. Is the bit resolution for a/d and d/a converters an important factor in considering an A/V amplifier/receiver? Is 24-bit always better than 20-bit ? In this case, I am considering a Yamaha RX-V995 and Denon AVR-2800. Obviously, I am looking forward to stuff like DVD-Audio, DTS, and Dolby Digital. 2. Is an optical-out port important? 3. What is the optimum position to place rear effect speakers? Must they be aligned with the two front speakers?

A In general, I would say 24 bit will give better performance than 20 bit, even with 16 bit recordings. It is not clear why this is, but it is probably because the 24 bit DAC has an easier time retaining accuracy with the 16 bit recordings than 20 bit DACs, and certainly easier than 18 bit or 16 bit DACs. Now, especially since DD and DTS are 20 bit, the 24 bit DAC is the way to go with receivers. Optical out (Toslink) jacks on DVD players vs. coax is not really an issue, since all the receivers I have seen have both Toslink and coaxial digital inputs. Placing rear speakers can be more difficult than placing the front speakers, because you have to deal with the couch where you are sitting. Floorstanders will have their mid and/or woofers blocked if the couch has a high back and you put the speakers behind the couch. If you mount them on the wall, then the wall itself becomes critical. It really depends on the layout of your room. I use floorstanders placed near the side of my couch and pointing towards the center of the room. They are about 2 feet away from the ends of the couch.

Q A few months ago I upgraded my HT speakers to Mirage's OM-6s, OM-C2, OM-R2s, but I got such a good deal that I impulsively spent the savings on Mirage's Substrata 1000. The Substrata is a "digital" subwoofer, and according to Mirage: "The Substrata 1000 produces an unbelievable 1000 watts from its little frame. This terrifying power is generated by a Pulse Width Modulation system that uses the output device as a switch instead of variable resistors that dissipate power." So my question is, what the heck does that mean? 1000 watts sure sounds like marketing-speak to me. Is it? What else is there to know about "digital" subwoofers?

A Digital switching amplifiers are the newest type of amplification. They switch the voltage on and off depending on the need, whereas Class A and A/B have the voltages on all the time, resulting in heat being dissipated, and power supply current being wasted. They have not progressed to the point that it is easy to generate good digital switching throughout the audible spectrum, although some manufacturers have succeeded. However, they are great for subwoofers because the band of frequencies is restricted to the low end, and this is relatively easy to do. Plus, they are extremely efficient and run cool, so they can be put inside subwoofer enclosures without the need for a big heatsink. Pulse Width Modulation (PWM) is just another type of digital technique. Pulse Code Modulation (PCM) is used for CDs and DVDs. PWM is used on laserdiscs, and believe it or not, it is considered to be analog video and sound rather than digital. (Two-channel PCM tracks are on the laserdisc too, and are considered to be conventional digital sound.) In any case, regardless of the fact that PWM is used as marketing hype, it is a very good product. Having 1,000 watts is extremely important in subwoofers.

Q First let me say I am a novice when it comes to home audio. I am trying to connect a receiver and surround speakers to a Sony Trinitron KV-35S36 TV. I cannot get the center and right front speaker to work. The receiver has a built in noise sequencer test which travels to each speaker, and they all produce sound. Any idea what I'm doing wrong?

A Somewhere from your TV to your receiver, you are losing the right channel audio. The receiver tries to decode the sound as Pro Logic, and it needs a two-channel stereo signal to do that. If the left channel audio is connected properly, but the right channel is not, you end up with left channel audio, no center, and no right. To have center channel sound, the left and right audio have to be working. They could be mono left/right, and that would give you decoded sound into only the center channel, with nothing in the right/left. So, check your right channel connection from the TV going to your receiver. It could be just a loose fit, or perhaps a defective cable.

Q I have a home-theater system with an Onkyo TX-DS575 receiver and Polk Audio RM6500 speakers. My problem is that the receiver's manual recommends the use of the "subwoofer pre-out", while the speaker's manual doesn't recommend the use of the "subwoofer pre-out". I would like to know which connection is better. Thank you.

A Polk is recommending that you use the speaker-level (binding posts) out to the subwoofer, and the speaker-outs from the subwoofer to your Polk speakers. This removes the low frequencies going to your Polks and allows them to concentrate on mids and high frequencies, making them perform better. You may be able to get the same results by using the subwoofer pre-out to your subwoofer, and using the menu in your receiver to set your Polk speakers to "Small".

Q I would like to get any information you could pass on to me about setting up a pair of the Carver Amazing Speakers. I don't know how much to tilt them, distance from wall, distance between the two, etc, etc. The listening place should be focused about 10 - 15 feet from the speakers. I know that direction and distance are VERY important with these things. They sound great already, but I want them to sound the very best they can, and I am clueless as to how this is achieved.

A I have two pairs of the Amazings, and love them. They do have to be placed carefully, as you say. I set them 4 feet out from rear and side walls, and toe them in towards the listener at about 15⁰. They are about 8 feet apart.

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