I guess I would have expected the PA system amps to be built around durability, not necessarily home-audio clarity. Never having connected the two (PA amp to hi-fi speakers) I'll claim ignorance.

-Scott

There have been so many blind tests over the years concerning "audiophile" and good average stuff it's a complete joke. By good average I'm not talking about those Awia home theater in a box things for $199. Say it's a $1,200 component system.

Nobody older than 18 and certainly no one over 40 could tell any difference at all between one of these PA amps and a $4,000 Macintosh or a $10,000 Silver going through a good speaker system in a blind behind the curtain test. The speakers are 90% of this IMO.

Bob

I bought my last home stereo receiver/amp combo used at Goodwill for $25, so I probably shouldn't even be in the discussion. I will attempt to gracefully bow out now....

I've been reading up on Mac's suggestions and am leaning towards the QSC - made in USA and has 6 year warranty. The Crown would be my next choice.

Another question...

My 'old' amp had an auto sensing which would turn the amp on when a signal is received. After a few minutes of no signal, it would shut off. This is important because the amp is not in an easily accessed area. Neither the QSC or Crown have this ability. I assume that leaving the amp on continually is not a good idea?

Does anyone know of audio signal sensor that would automatically turn power on/off to the amp? No, the Clapper won't cut it!

Thanks

Electrical and electronic components are under the most stress at switch-on, so continually powering up and down isn't the best idea. You've possibly noticed how light bulbs only fail when you switch on the lamp.

Many studios leave everything on 24/7 whether it's being used, or not. Personally, I'd switch off at night, or when leaving the house, just as a fire risk.

ROG.

there are power strips available that have master-slave outputs, and the slave outputs only become active when whatever is plugged into the master outlet is turned on. My son just bought a couple of them for exactly the same reason as yours, Rachel. He has music equipment that he uses at the same time, and only one of the items has an ON switch that is conveniently located. So he plugged that device into the MASTER outlet, and all the other stuff into the SLAVE outlets.

He keeps the switches turned on all the time for the slave devices, so they can be active when their outlets are active. Then, by turning on only the master device, everything comes on and stays on until the master device is turned off.

For equipment that is all used at the same time, and is located close enough to share the same power strip, it's a pretty neat solution.

They cost about $20-$30. I'll ask where he bought it and post that info later

Pat and Rachael,

Given that these things exist, there's something you have to be careful of. Some quality audio gear has a power-on delay circuit intended to avoid the transient "thump" on power up which can damage speakers and ears. Bypassing the onboard power switch also bypasses this safety feaure. I'd like a remote switch for my powered monitors, but I'd be afraid to use it. Unfortunate, but I'll stick with the inconvenient* device switches for that one.

FYI,

R.

*I have to take two steps from side to side. What a drag.

You speak of bypassing the switch...

I'm not talking about a short circuit in which some part of the wiring is skipped.

In a device that is always plugged in, power waits at the switch until it gets turned on. The switch itself is just an on-off gate. Once the gate is open, power proceeds to the circuitry and whatever features are built into the electronics do their thing.

Seems to me that this feature would not be a function of the switch, so leaving it in an ON position wouldn't change the flow of electricity at all. Any buffering would still be there, happening after the power got past the switch.

And even if it IS built into the switch... the power will still pass through the switch, so... what changed?

What we have here is failure to cmyoonicate. I know what I'm saying is true but can't explain it any better at the moment (working). I'll come back to it, or maybe someone can clarify it before then.

Okay, I'm on break. Let me try again.

When you turn on a power switch it is considered "energized." Doing this from our notional amplifier's switch starts a timer connected to a relay which suppresses audio output until the power-on transient has passed. This is a one-shot device. The delay won't happen again until you cycle the unit's onboard power switch again, i.e., turn it off and back on.

Therefore, if the switch is left on while the device is powered down, when you reintroduce power you will get an inrush transient as the device powers up, but with no delay as the relay has already been triggered. Therefore the transient will be passed to the speakers if they are on. Megathump to the max. Bad. Krunk says not do.

Is mo' bettah?

You can buy a rack-mounted power distro that is designed to delay the power to the outlets for amps. Used it for years in a built-in rack at the listening room at GM, but can't remember the name of the brand!

IMO, every amp rack in a PA system should have one of these boys.

-Scott

here's a link to the strip I was talking about for anybody whose devices don't have the feature Richard is talking about:

http://1000bulbs.com/product/56488/TCP-L...=www.become.com

a similar device:
http://www.brookstone.com/smart-strip-automatic-power-controller

I especially like the "ergonomic design." Whaddya, gonna sit on it?

I don't use a preamp. I use a Logitech Duet to stream music from my computer and Pandora. The output from the Duet goes to the amplifier via RCA plugs. Volume and anything else is controlled via the Duet.

The power strip that shuts everything off when the master is powered down looks very interesting. I am not sure it would work for me as the Duet goes into a standby mode which really is not off. However, I am able to turn it off with a few extra steps from a remote. I'll read up on these and see if it would work.

A comment on the audio sensing switch - I suspect this may contributed to the Audiosource to fail twice. I recall several occasions during a storm where the amp switched on/off several times. And during soft music passages, the amp would cycle off/on a number of times.

Despite being connected to a voltage regulator and whole-house surge suppressor, it still managed to die twice in 3 years with sparse usage. Another reason to favor the QSC is the 6 year warranty.

Thanks everyone for the input.

R

Rachael, you're talking about listening to MP3's. You're not listening to CD quality much less audiophile. Read this:

http://help.pandora.com/customer/portal/articles/90985-audio-quality

For that level of audio quality most anything would work fine like Scott's $25 amp from Goodwill. Forget about how great the spec's are for QSC and the like. MP3's are compressed files for pete's sake. If you honestly can't tell or don't care about the difference between listening to a CD quality song in Real Band and that same song compressed to an MP3 at 128K then this whole discussion is academic. Basically anything would be fine as long is it's not humming and crackling.

Bob

Maybe her mp3 files are at higher bitrates or possibly even the no-loss Variable Bitrate.

Maybe she also wishes to listen to CDs.

Maybe she also wants hi fidelity to play BiaB, DAW and other sudio as well.


--Mac

Bob,

Not only Pandora. My music collection is lossless FLAC. So to add to Mac's post: yes, yes and yes

R

As far as I know, variable bitrate .mp3 files are still lossy.

There's always the point about cumulative loss. That is, whatever the quality of the source material, you don't want to degrade it any further.

Just sayin'...

ROG.

I noticed that in the last few months amps weigh way less. I have 2 heavy duty ones. I also note that some new amps have 20 amp male plugs, the club thought they were 220v but it's specd at over 15 amps (most wiring)' so new copper, new plug and off you go.

Oh yeah, 9 puonds for a 1000W stereo amp? Amazing. My old 500W Peavey has to weigh 40 pounds, maybe more. That thing is a real lump. Sounds good though. And then there's the new neo whatever magnets for speakers. That combo is how the new powered Class D PA speakers like the Yamaha DXR series put out 1100W and weighs 34 pounds. I've been looking to upgrade my stage rig and this new stuff is really good. Expensive too, I'm still trying to calibrate my "bang for the buck" meter.

Bob

The heavy weight of the older bipolar transistor power amplifiers was due to the fact that they had to incorporate a heavy "iron" AC power transformer. Since bipolar transistors are Current devices, that meant being able to supply the amplifier itself, which typically weighs less than a pound or two (driver circuit board plus output transistors and lightweight aluminum heatsink) with a voltage lower than the AC power input, transformed to high Current. At 50-60Hz, that requires a lot of iron laminations in the power transformer.

The weight savings in today's designs come from using modern Switching Power Suppy desings, which, while still needing to supply the lower voltage at a higher current, can do so without the need for the big mass of iron because the Switching Supply first rectifies the incoming AC to DC, then "chops" it up into AC at a much higher frequency, typically around 40KHz or higher. They still use transformers, but at that higher frequency the transformers are very small indeed by comparison.

The use of the FET (Field Effect) Power Transistor intead of the older Bipolar Silicon transistor also contributes to the lowered cost and weight of the modern power amp. Means we can control more power with less devices. And a few other good things.

An amplifier of any kind is but a modulated power supply.


--Mac

Rachael, I wasn't being condescending.

Mac, that's all she referenced, streaming Pandora. Pandora's site says consumer stuff only receives it at 128K. At that bitrate, you don't need a good spec amp. How many times have we including you, suggested to people if you want good answers provide complete info in your questions? I've read her posts before, she knows the difference between mixing good audio in a home studio and streaming MP3's. If she's only talking about one and not the other so?? Sorry Rachael, I'm not deliberately talking past you here, this is for Mac. And how many times Mac have you said if on a budget pick up a good name 70-80's era stereo receiver at a yard sale? Or Goodwill like Scott said. Even a 2000 era cheapo Panasonic/Awia/Sony low end consumer home theater receiver is fine for this. And if a person can't hear the difference between an uncompressed wav file and an MP3 anyway then you still don't need a high spec amp do you? Therefore, my answer was complete, correct and not condescending. Just the facts, ma'am.

This brings up another point that we all should consider when thinking about new equipment. There's ear testing websites and we already have home studio setups. Test ourselves if we really can hear these differences or not. I admit I can some of the time. Other times not so much. It mainly depends on the freq range in the source material. Higher freq's are what starts to break up in compressed files and higher freq's are what older folks start to lose first. I can hear cymbals breaking up on some MP3's but mainly on small group stuff like trios where the drums are hot. But, on bigger band higher engergy stuff like traditional big band or TOP things, it's pretty hard to really hear that. For me it's becomming marginal as to whether it's worth it or not. I've been using an Alesis RA100 amp for years and I'm pretty sure that's as good as I will ever need for this stuff at home. You can buy one of those for $100 used all day long now. When I mix stuff after I get it to where I think it should be I deliberately boost the higher freq's above 9K a few db to allow for people with better hearing because my own hearing rolls off about there. I'll never know if that is appropriate or not but I think it is.

Bob

I took no offense to any comments; you would know if I did . My earlier post did say that I listen to both Pandora and music streamed from my computer. Funny how some of these topics drift.

I have always appreciated anyone taking time to respond - this is no exception. Again, thanks for all of the feedback.

R

I'm responding for the appreciation. I bought gear based on inpuT from here or a friend. Makes me seem smart. But I long ago learned I'm not learned enough. Thanks for the mamm..I mean memories.

@Mac- my point was to make sure that folks are not misled into thinking that vbr files are lossless. They are not. FLAC and monkeys audio files are compressed lossless files. I exited the amp specific portion of this discussion with my goodwill purchase comment. Merely correcting a technical point .

As for detecting compressed vs uncompressed, with lame encoding my self imposed limit is 192 Kbps. It's a rare thing for me to hear any differences between files compressed at that rate and any higher up to 16 bit 44.1khz .wav files. I have slightly less than perfect hearing at very high frequencies, not enough to be labelled a loss, but les sensitive than my mid and low frequencies. With lower bitrates I find similar experience as jazzmammal. Ride cymbals are the giveaway.