Home Page

Q&A # 176 - May 3, 2000

Staff

Divider

Q I have an old Harman Kardon (Citation 12, Citation 17) power amp and pre amp which was lost in a power surge, and I am wondering what's on the market to replace it. Insurance coverage is cost of replacement. Any suggestions?

A With the way things are moving, I would suggest getting geared up for home theater. Even if you didn't watch any movies, 5.1 music is on its way, so you will need a surround sound system. The best bet is to get a good receiver and a five-channel power amplifier. Receivers have the most features, but they all benefit from an outboard power amp.

Divider

Q I was just wondering if you would know what is causing my subwoofer to thump every time I change sources (e.g. if I switch from video1 to video 3)? This has been going on for about 3 months now, and lately it gives out a different kind of thump even when I don't change source or even when all the other components are turned off (it has an automatic power on). It is a Ditton, made in the UK. I have tried switching it back to manual power-on, but it still thumps. I hope you can help me out with this, thanks.

A I suspect there is some DC at the input to your subwoofer coming from the preamp that is causing this. Since the problem has become worse, and it occurs without the other equipment being on, perhaps a capacitor connected to the input of the subwoofer has gone bad. Sounds like a repair shop is in your future. You should test to see if it occurs when there are no input cables connected to the subwoofer. Then, see if it occurs when you change to the other input jack on the sub, or try using both input jacks if you are only using one (try using just one if you are using both). Also, try using the speaker-level inputs on the sub instead of the RCA inputs (or vise-versa).

Divider

Q I have a Knoll HT-30 projector, and it has a Composite, S-Video, and RGB/Component (15 pin mini d-sub) connector. Currently, I have it hooked up to my DVD player using the Composite output, although I would like to hook it up using the Component Video out for the best possible result. My question is: Does anyone make a Component Video (3 RCA out) TO RGB (15 pin mini d-sub) Adapter?

A The good news is yes, it is called a transcoder. The bad news is that current Component-to-RGB transcoders cost any where from $699 and up.

Divider

Q I am using a pair of Velodyne FSR-1500s for my home theater setup. I would like to know if a single FSR-1800 would outperform the two FSR-1500 subs? Also, which would give a better sound, a pair of amps configured to a monoblock or a pair of the same amps used in a bi-amp setting?

A Velodyne's drivers on the 15 and 18 have pretty much the same maximum forward and backward movement, so we can simply compare the area. For the 15" sub, it is p 7.52 which equals 176.71 in2. There are two of them, so that comes to 353.42 in2. For the 18" sub, it is 254.47 in2. So, the two 15" subs move more air than a single 18" sub. To configure your pair of amps into one, you have to bridge them, which means using only the + binding posts (the + on one amp and the + on the other). It also means having a common ground and one input inverted with respect to the other. I would suggest using the two amps to bi-amp your speakers instead. Bridging reduces the low impedance driving capability.

Divider

Q I am having a very annoying problem with my Pioneer amp. Often when it switches digital modes (usually when navigating menus where the sound switches on or off) there is a loud pop. This can happen two or three times in a row and then stop. I can understand a small amount of switching noise, but I am concerned that these loud pops will damage my speakers. Any advice would be appreciated.

A My Yamaha DSP-A1 does this too, when it automatically switches between DD and DTS. They are produced by transients. The way I combat it is simply to turn the volume down when I switch between digital inputs.

Divider

Q I want those big, beautiful, sexy power (watt) meters like the ones on McIntosh Amplifiers. I'm sure you've had people ask where they could find such things - I've seen posts everywhere, but no one seems to know where to get some watt-meters for their amplifiers or speakers. Have any resources for me?

A They are usually just volt meters connected across the outputs somewhere in the circuit. All you need to do is get some volt meters in the range of your amplifier power. For example, if you have an amplifier rated at 200 watts into 8 Ohms, this translates to 40 volts and 5 amperes (using the formulas E=IR and Power=EI). So, you would get AC voltmeters that register somewhere in the range of 50 volts maximum. Electronic supply stores sell these. Here are some links: http://www.jkelectronics.com/prodpge/panelmtr.htm, http://www.electronicsurplusind.com/volt.htm,  You can expect to pay about $25 for each meter. A 25 volt meter would be appropriate for 75 watt amplifiers. Keep in mind the meters only give a rough idea of watts, since the impedance changes depending on the frequency.

Divider

Q I have VMPS Ribbon Monitor 2 speakers as my left and right front speakers. I am using a conventional speaker for the center, but decided to obtain a Maggie MGCC1 center channel speaker, since it uses a planar design. I just read, however, that the MGCC1 only goes down to 160 Hz. Will this create a problem? I have a Theta Casa Nova and can set a 160 Hz crossover on the center, and direct the lower frequencies to the front left/right speakers. The amp is a Parasound 2205. Any suggestions would be appreciated, including changing the CC to something else. Thanks.

A A lower limit of 160 Hz would be a serious problem since all sound above 50 Hz can be localized as to the direction it is coming from. This means that the sound from 50 Hz to 160 Hz would be localized as coming from your front left/right speakers. You would probably be more satisfied with a ribbon center speaker that goes down to 50 Hz, implying products that have ribbons for the mid/treble and cone drivers for the low frequencies.

Divider

Q How do you hook up a second amp to drive your surround speakers? I use a Pioneer VSX-D608 receiver as the main amp (front & center). It has a center pre-out and a sub pre-out. I have a couple of spare receivers, but am not sure how to get them to work together.

A The way to use your spare receivers is to connect the center channel pre-out of your Pioneer to an input on the spare receiver. This will take a major load off the Pioneer, since most of the energy comes from the center channel anyway.


� Copyright 2000 Secrets of Home Theater & High Fidelity
Return to Q&A Index.