Legacy Connections, Power Strips, Bit Rate

Living Legacy
Why is it that most A/V receivers still have 2-channel RCA inputs? Why doesn't a company make a receiver that has only HDMI, maybe with a few component-video and digital-audio ins and outs? Why the need to include legacy stuff?

Bob Aldridge

Because lots of people still have legacy products, and an AVR is intended to be the central switching station in any home-entertainment system. It's the same for HDTVs, which still have composite and S-video inputs on them.

Vampire Power
When you plug components into a surge protector (or any power strip for that matter), do the peripherals continue to draw vampire power after the switch on the power strip has been turned off, or do they continue to draw standby power? I have read both accounts. Plugging and unplugging from the wall can take a toll on the outlet. I would prefer to just flip the switch on the strip if it powers them all down, but I want to ensure that there is no power going into the components.

J. Casello

As far as I know, turning off a power strip stops all power from flowing to any of the connected devices. However, this might not be such a good idea, especially if the devices have something in memory such as the date and time or other settings that rely on a trickle of power when they're off. Also, if you turn the components on and off with the power strip's switch, they might receive a momentary jolt of power that could shorten the life of their delicate electronics. Finally, if you suddenly stop power from flowing to a device that's on, it may think there's been a power outage and reset itself, requiring you to turn it on separately anyway.

In my view, the trickle of power is negligible and well worth paying a few pennies for in order to keep any memory powered and prevent the possibility of power-on surges. It would be much better to get a good universal remote and power the devices on and off that way.

A Bit of Confusion
I really appreciated your discussion with Leo Laporte a while back in which you were explaining how analog audio signals are sampled to make a digital file. Let me see if I got what you were saying before I get to my question. You start with an analog signal, and you sample it 44,100 times per second for CD, measuring the instantaneous level at each sample point.

Where I get lost is when we throw in the bit rate. I create my podcast recordings at 64Kbps, but I don't know what that actually means. We've measured the amplitude 44,100 times per second, so what's left to do at 64Kbps?

Allison Sheridan

You got it right that to convert an analog audio signal to digital, the signal is instantaneously sampled 44,100 times per second (the sampling rate, often written 44.1kHz). Also, the instantaneous level of each sample point is represented by a 16-bit binary number (the bit depth). BTW, these are the specs for CDs—Blu-rays often use different sampling rates and bit depths.

Bit rate is a measure of how much data must be able to flow through the system to play a digital-audio file, so it is relevant during playback, not sampling. The bit rate required to play a 2-channel signal that was sampled at 44.1kHz/16 bits is 1.4 megabits per second (1.4Mbps). This is uncompressed digital audio, which is technically called PCM (pulse code modulation).

However, podcasts must use a much lower bit rate than this so they can be quickly downloaded or streamed from the Internet, so the PCM data is compressed by discarding up to 90 percent of the original sampled data. If this is done properly, you still perceive much of the intended audio, but the data rate required to play it can be reduced to only 64 kilobits per second (Kbps) or even less.

There are many different types of digital-audio compression; MP3 is the most common. So if you see a digital audio file that is identified as PCM, you know it's uncompressed, whereas an MP3 file is always compressed so it requires a lower bit rate to play back.

When you record audio for your podcast, the computer is compressing the digital audio as it goes, and you can typically specify the bit rate you want to use when the file is played back. In general, the lower the bit rate after compression, the lower the audio quality.

You might want to try a little experiment—record something at the lowest possible bit rate and then record it again at a higher bit rate, then listen to both recordings and see if you can hear the difference in sound quality.

If you have a home-theater question, please send it to scott.wilkinson@sorc.com.

Nathan Ruwe's picture

To J. Casello, supposedly Monster makes a surge protector/power strip that automatically turns all power off to the outlet once you turn the device off, if it actually works I don't know, I guess the only way to know for sure would be to get a Kill-a-watt and hook it up to the outlet to check power consumption.

CARL75014's picture

Excellent. But what I'm still waiting for, to buy my AVR, is a true 6x3 HDMI 1.3 switch integrated, allowing 2 x independant content outputs sent to my 2 x Full HD displays (main room and bedroom LCDs) both up-scaled to 1080p independantly, ideally with HVQ Reon/Realta. The 3rd HDMI-out would be to connect an HD RECORDER that no AVR of any price offers today via HDMI while many HDMI Blue Ray recorders are on the market for a while. In today AVRs the HDMI content can't be passed to lower sockets (non-HDMI I mean) so DVR out plugs only offered in non-HDMI today can't be used to record un-protected HD content from HDMI connected sources at all (Camcorders, Pop Corn Hours...etc). This is an incredible dead-lock nobody comments ! I was hoping the new Denon AVR-4310 would solve this but it's only adding marketing features this time. How long will I have to wait ? Can I expect something from next ONKYO range (they were 1st on HDMI 1.3 AVR but releassed nothing significant since their 905). Others ?

Cliff's picture

I have actually used the Monster power center Nathan refered to, the MP HDP 900G. It does work well. It retails for 129.00 and does have basic power filtering. Now, hopefully I will see a product like this from a company I like better, say Panamax or APC.

Scott Wilkinson's picture

Boy, Carl, you don't ask for much, do you? I know of no AVR that provides multiple HDMI outputs that can send independent signals simultaneously—in fact, most AVRs with two HDMI outputs make you select one or the other. Also, Blu-ray recorders have been on the market in Japan for years, but they are not available in the US, and even if they were, they would not allow recording from an HDMI source. You'll be waiting forever for that.As for "downgrading" HDMI to analog in order to circumvent copy protection for recording, the studios have gone to great lengths to prevent unauthorized copying, so they will surely never allow that.I disagree that the Denon 4310 offers only "marketing" features—for example, its inclusion of DSX is very significant. You're right that it doesn't do what you're asking for here, but no AVR is likely to do that in the foreseeable future.

John Nemesh's picture

Carl, I think you may wait for a LONG time for any kind of HD recording option...longer for something to record from HDMI. Remember, HDMI was designed, no, ENGINEERED, to connect a single component to a single display. It was specifically designed NOT to allow connection to multiple displays simultaneously. However, Gefen (and others) have HDMI "splitters" that will give you multiple HDMI outputs simultaneously. It does this by only showing a "reference" EDID to the source (or using the EDID from only the 1st connected display). This works GREAT if you have the same setup in both rooms (same resolution TV, and A/V receiver in both rooms). If you are using one TV with an AVR and one with TV speakers only, you will have trouble. Keep in mind, these are NOT inexpensive. It is generally cheaper to just buy another cable box, blu-ray etc for the bedroom, but if you REALLY need to share, it can be done! Feel free to mail me at john.nemesh@avad.com if you have questions!

Scott Wilkinson's picture

There's also the option of an HDMI matrix switcher, which can take several HDMI inputs and send them independently to one or more of its HDMI outputs. These devices are generally VERY expensive—typically in the thousands of dollars—but they will do the type of routing you are asking for. Also, since your TVs are in different rooms, you'll probably need an HDMI extender for the farther one, which is another few hundred bucks.

rex's picture

my favorite surge protectors are panamax and furman.They both offer sequentual turn on,on all but their lowest priced models I think (check their websites).In the case of many home theater receivers and some dvd players digital output setting for example they will not hold memory settings so it probably is best to leave them plugged in-however using a panamax or furman would still save energy(and your money)by using the always on outlets for those components and if you have others that don't require constant power plugging those into the other outlets(which are powered on by turning the surge protector on and off)-of course if all your compnents require memory such as receiver,maybe dvd player,cable box,tv etc then it's probably a mute point although you still might get better a/v performance from using one of these units and if you live in a home that's at risk from surges it's well worth an investment to protect your equipment.

Anonymous's picture

LIVING LEGACYI loved Bob Aldridge's question and would like to lobby for a more thorough response...Have any manufacturers done the research on the percentage of consumers who crave legacy inputs? I'll bet a simpler, cleaner, AVR would prove very appealing to a significant percentage. Get rid of the cable mess, decrease the manufacturing cost, and upgrade the interconnection quality in one fell swoop -- power, HDMI, speakers, done!Would a manufacturer (who has a reputation for valuing quality/simplicity) be willing to comment on this?Thank you in advance!

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