Q&A # 283 - April 12, 2002

Staff

Q The promotional material for SACD and DVD-A mentions an increased frequency response far above 20 kHz. Since we don't really hear above 20 kHz, is this significant?

A We have listened to SACD and DVD-A, and they do sound better than conventional CD. However, I (JJ) believe the improvement is due to more accurate reproduction of the sound in the audible band, rather than increased frequency response. Here are two spectra that I collected from a CD of Verdi's "Requiem Mass", containing chorus and orchestra. Spectrum 1 is an average of the first 1 second when things are just getting going. Spectrum 2 is an average of several minutes of music. Notice that the majority of the sound is concentrated in the  60 Hz - 6 kHz regions. There really is not very much up at 20 kHz, and with SACD or DVD-A, I am sure there would be even less above 20 kHz. Most of what we hear in music is well below 10 kHz. I have seen this 60 Hz - 6 kHz concentration on numerous music discs, using other CD players and analyzers, but in order to have a complete spectrum, you need to use a CD that has a full orchestra and human voices too. In the Verdi test, it was chorus and orchestra.

Q I have a Philips Audio CD Recordable/Rewritable (CDR 770). I recently purchased an RCA digital optical cable to record from various sources that have optical output. It didn't take long to notice something was not right. Whenever the sound I'm recording peaks momentarily above the normal levels, I get an incredibly loud and startling pop or cracking sound.

A That is what clipping sounds like. It has nothing to do with the cable. Turn down the recording level so that the peaks are at 0 dB. Digital recording has an absolute ceiling above which you get clipping. It appears to me that you are taking a digital signal from a source and converting it to analog. Otherwise, the digital copy should be bit-for-bit, and no further clipping than is already there in the original.

Q I have a Denon AVR-3300 receiver and an Onkyo  SV-525 receiver that I want to use for bi-wiring. How do I connect them?

A This would be bi-amping, not bi-wiring. You will need to use a Y adapter to split your analog inputs to go to both receivers. Remove the bus bar that connects the tweeter and mid/woofers on the speakers. Connect the speaker outputs of the most powerful receiver to the woofer and the less powerful one to the tweeter. You won't be able to use the digital output of your DVD player through a Y adapter, only analog outputs. You can also use one of the pre-outs from one receiver to an input on the second receiver.

Q Are preamplifier/processors designed primarily for movies and not for music listening?

A The are designed for listening to any kind of audio source, being able to handle two-channel stereo as well as 5.1 surround sound. We have heard that if you configure your speakers for surround sound, this compromises two-channel stereo, but we have not found this to be the case in practice. The idea that you need one system for stereo and one for home theater is nonsense. That does not mean you can't do it if you want to, but you just don't have to.

Q We have a Technics SA-EX600 receiver and have recently bought a RCA DVD 5 disc changer. Is the Technics able to handle a DVD player? The outputs in the back support CDs but nothing about DVDs, and the manual does not address DVD issues.

A If the Technics is a modern receiver, it will have digital inputs for connecting to your DVD player. If it is an old receiver, then you probably have to use the two-channel analog outputs from the DVD player. These outputs will send the audio from both CDs and DVDs to your receiver. Receivers a couple of years ago had 5.1 analog input jacks (a distinct set of 6 RCA jacks designated for this purpose). If the Technics has those, you would also need 5.1 analog output jacks on the DVD player to use them.

Q I just had a 7 year old Pioneer Pro98 calibrated by an ISF technician. Two days later, a major convergence problem arose that cannot be adjusted. It only involves the lower one-third of the screen. The guns are totally out of alignment in a half circle from the lower right edge to the lower left edge. Everything was fine prior to the calibration. Is it just coincidence?

A I don't think this is a coincidence. I am sure the ISF work has a guarantee. Activate it pronto.

Q I am in the market for a new RPTV and I'm having difficulty justifying the price difference between The Pioneer Pro 620HD versus the Toshiba 57HX81. The Pioneer is twice as expensive. Is it THAT much better?

A It used to be that all TVs had just an on/off dial, volume control, and channel selector. The price difference was based on the size of the screen and cabinet it sat in. Now, it is features. Some use CRTs or LCDs. Some will handle 720p. Some have several sets of various input types. If you can compare them side-by-side, that will be the best way to evaluate them. Have the salesman connect a good progressive scan DVD player to both of them using component video cables. Take a couple of your favorite DVDs.

Q I recently purchased a Marantz SR-8200 receiver and am very pleased with its performance thus far. The manual states that to get the best stereo performance from it, I should use the source direct feature on the receiver. The problem for me is that using the source direct function bypasses the bass management and tone controls of the receiver, and thus the subwoofer does not function in this mode. This mode runs the front two speakers full range, but my front speakers do not produce enough bass on their own (Polk RT-800i). I read that in this instance, I may connect the subwoofer to the pre-outs of either the left or right channel to activate the subwoofer while using source direct. My question is: 1) is this a safe way to get the subwoofer to activate and 2) how does this affect the receiver's performance in any other mode, i.e., DTS, DD, THX,?

A Using the front pre-out for the subwoofer will work for the direct mode, and also for surround sound, but it would only be getting the bass from the front left or right, if you only used one channel to drive the sub. You could connect both the front left and front right pre-outs to the subwoofer, or you could connect the front left pre-out and the subwoofer pre-out to the sub (subwoofers have left and right line-level input jacks). This would give you some bass with direct stereo and also the complete set of low frequencies with surround sound.

� Copyright 2002 Secrets of Home Theater & High Fidelity
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