Q&A # 262 - November 3, 2001

Staff

Q I saw an advertisement for THX Ultra 2. What is it?

A It is a new seven-channel plus subwoofer playback specification that works with 5.1 audio. Here is a link http://www.thx.com/press/ultra2.html. Seven channels have been available for quite a while actually, in Yamaha receivers, Lexicon and Theta processors, for example. THX Ultra 2 formalizes it for all mass market receivers that want to have it (and willing to pay the licensing fee). My guess is that companies like Yamaha will just continue to have the 7.1 that they have now, and not bother to pay the licensing fee for THX Ultra 2 certification.

Q I need to know the differences between a HEXFET amp and a MOSFET amp. Is either one better than the other?

A HEXFET^� is the Registered Trademark for International Rectifier's Power MOSFET. Whether one company's power MOSFET is better than another company's is a matter of argument, but the HEXFET is a good one.

Q I have a pair of Cerwin-Vega VS-120 home speakers. I have blown one of the woofers in one of the speakers. I was wondering if you have any info on how to order a replacement one.

A Contact Cerwin-Vega with the model number. Here is their Service Department's e-mail address: [email protected]. Here also is their web page that describes the cost of replacing woofers: http://www.cerwinvega.com/service/index.html.

Q In your recent Q&A #261 a reader was having ground loop problems. I have had a similar problem and have found the culprit to be a grounding differential between the house ground and the cable TV ground. A Tributaries Ground Guard in the cable TV run solved the problem for me.  I have been told that this kind of problem can also be caused by having your video equipment plugged into a different house circuit than your audio equipment, but I have not experienced this myself.

A Thanks for the info.

Q I'm not normally one to send in corrections, but I wanted to make sure none of your readers ended up buying one thing and getting another. "Colorstream" is Toshiba's marketing term for interlaced component video. "Colorstream Pro" is their term for progressive scan component. (Your response did not make this point clear.) Either way, it's a cheap, yet effective, way of convincing consumers that they have to buy both a Toshiba DVD player and display to get the true benefit of the trademarked Colorstream semantic technology.

A Yup. Marketing is a very important tool in business.

Q I have a DVD player, Toshiba 2700, that has digital and analog audio outputs. I understand from reading previous Q&A's that the HDCD capability only works when using the audio outputs. So, can I do this: Connect the DVD digital out to my DVD digital input on my receiver for movies, while at the same time connecting the DVD audio outputs to my receiver's audio CD inputs so I can enjoy HDCD music CD's? I don't have a CD player.

A Yes, this should work fine. Most receivers have a hierarchy of choosing input jacks if both digital and analog cables are connected to the same input (such as the "DVD" input jacks). It probably defaults to the digital cable jack, so you will have to manually select the analog audio input jacks when playing CDs. Another way of doing this is to connect the digital cable to one input, say "DVD", and the analog cables to a second input, say "CD". That way, you just turn the dial to DVD with movies and CD with music.

Q In reference to the reader who asked about putting a B&W center channel speaker on top of his TV, it just so happens that I have a B&W HTM-2 sitting on top of a 36" Sony Wega XBR (XBR200), and I can testify that it fits perfectly. The top of the Wega is flat, and deep enough that an HTM-1 would also have fit securely, but since my other speakers are 805s, I found the HTM-2 to be a better match. Because the top of the TV is deep and completely flat, the HTM-1 and HTM-2 form factors fit very well just sitting on top.

A Thanks for the info. Just remember that some TVs don't like heavy objects sitting on them, so be careful.

Q I have been doing a lot of internet shopping for a new power amplifier. I was under the impression that an amplifier's Total Harmonic Distortion (THD) rating was of some importance, but the more I shop, the more I see some of the high end (i.e., Mark Levenson, McCormack etc.) and tube amplifiers with distortion ratings as high as 1%, whereas others have distortion ratings as low as 3 places to the right of the decimal. Is THD really a big deal?

A The total amount is not as important as the type of distortion, i.e., even-ordered harmonic distortion or odd-ordered. Even-ordered is easy on the ears, and odd-ordered is very irritating. You could have 1% even-ordered, which might easily be the case with a tube amplifier, and it would not be as noxious as 0.1% odd-ordered distortion. This is why we analyze the type of distortion in our Benchmark tests. Here is a test tone with only even ordered harmonics added, and here is the same test tone, but with less of the even ordered harmonics, and with some seventh order (this is odd-ordered distortion) harmonic added. So, when someone says to turn down the volume, it is likely they are hearing odd-ordered distortion rather than simply too much SPL.

� Copyright 2001 Secrets of Home Theater & High Fidelity
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