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  • J Tiers
    replied
    <font face="Verdana, Arial" size="2">Originally posted by Paul Alciatore:

    Digital in an amplifier is a farce.

    The output stage is still an analog power amplifier. Digital just adds the possibility of adding digital noise to the mix.
    </font>
    False....falser than false....I ought to know, I design them.

    Output stage is "digital" in that it has two states. Some have two states plus an "off" state, somewhat like a logic circuit.

    <font face="Verdana, Arial" size="2">
    Yes, you need it for a digital system but it is not an automatic increase in quality and it is definitely not a way of providing power to drive speakers.

    </font>
    Again false. You DON't need it for a "digital system", but it very much IS a way of providing power to drive speakers.

    Most people call it digital, but it is generally actually PWM (class-D), or a derivative of that ("class-T" from the tripath folks, etc, etc).

    VERY good performance available, from the top types such as Spectron, and others. But, yes, the audiophile varieties will charge you several thousand per channel.

    Frankly, it isn't justified, good quality Class-D is actually far cheaper than analog.

    Leave a comment:


  • darryl
    replied
    Greg's comment is pertinent. Most new amps aimed at the home theatre crowd are not rated to drive a load less than 8 ohms. When you consider that an 8 ohm load can vary from less than 4 ohms to more than 20 ohms, depending on many factors, then two pairs of 8 ohm speakers can sometimes appear to the amp as a 2 ohm load (per channel). I won't get into the math, but suffice to say that these flashy, feature rich multi-channel components aren't tough or reliable, and they're not up to the task. If what you're looking for is a good solid amp that can deliver real power for considerable periods of time, then you won't find it in that kind of junk. Power ratings are extremely misleading and have virtually nothing to do with quality. And as Greg mentioned, if something goes wrong with the brain, which is usually the front panel, yer hooped.

    As far as dc response goes, the protection network that virtually every amp has will disconnect the speakers if there's a dangerous level of dc on the output. This could come from the system somewhere, usually the pre-amp, or it could come from a failure within the amplifier. Either way it won't matter as long as the protection circuit operates properly, which it almost invariably does. Personally, if I had the choice of amps to have, and one was rated as flat to dc, I would use that one instead of one rolled off at some number below 20 hz. I know that it would be eliminating one potential source of distortion by not having a coupling cap in the signal path, however the difference would seldom be noticable. Used as a sub amp, the lack of phase shift at the low frequencies would result in a lower distortion of the original sound, but here something ironic happens anyway. Some distortion helps the audio to sound 'powerful', and most people like that and would say that it's 'better' sound.
    At any rate, I wouldn't worry about a dc capable amp destroying your speakers, as pretty much any amp is capable of doing that, if a couple of certain faults develop at the same time. The biggest reason to not run the amp in dc mode is to protect against a bumped turntable sending a huge spike down the line to the speakers. If you're still running a turntable, this might be the deciding factor when considering which way to set the dc/capacitor coupled switch on the back of the amp.
    What JRouche says about an underpowered amp clipping, and being more dangerous than a higher powered amp, is also true. If you run the amp to clipping, you're generating large amounts of high frequency conponents, which the crossover network will deliver straight to the tweeter and overpower it. Any good amp will clip cleanly though, minimizing these unwanted artifacts. Some amps, even some purportedly good ones, will freak out when driven to clipping, and anything can happen. Sometimes it'll go into low frequency voltage swings which then makes your woofers vulnerable. If you see this unusual 'flopping' going on with your woofers, that's an amp to get rid of.

    Leave a comment:


  • AZSORT
    replied
    I agree with Darryl, Only buy a new amp if you want home theater. The really good amps were made 20 years ago. They can be repaired forever and are readily available for fair prices on EBAY. All the new stuff is made to be disposable with computerized front panels that are non-repairable. Also be real careful of the fine print on new amps concerning the output impedance. They generally can't handle any speakers in parallel.

    Greg

    Leave a comment:


  • Excitable Boy
    replied
    Here you go:

    http://rotel.com/products/specs/ra1070.htm

    Most Integrated Amp for the money I'm aware of.

    Their stuff is good enough that I still recommend it even though they fired us six months ago!

    John

    ------------------
    Pursue Excellence and the rest will follow.

    Leave a comment:


  • HTRN
    replied
    ahem, I was referring to frequency response.

    Yes, I know that most people can't hear below 20hz or much above 10K(that's how they piggyback DSL on the phone, phones don't go above a certain frequency)

    As for the Legacy Monobloc, I first discovered them when doing research for an ubersubwoofer(lemme put it this way, ever heard of a Velodyne F-1800? This was going to be MUCH louder) and was reaaallly impressed by the specs... Most amps really peter out below 100hz...

    review
    manufacturers website


    HTRN


    ------------------
    This Old Shed

    Leave a comment:


  • darryl
    replied
    Having been in the repair end of things for 30 plus years, I'm saddened by the turn of events in amp manufacture. The way they're built now is nearly as throw-away junk, even though they can sound good when working properly. Typical these days is one large pc board with several smaller pc boards stiching up out of it. There's often no bottom to remove to get at things, and if it needs repairs, it can be an expensive nightmare. Makes me sick. Give me one of the older good quality amps, and with some maintenance it'll be good for many years yet, and it can be fixed when and if it breaks down. It is true though that if it's loaded with features, there will be more circuitry inside, with more signal pathways, so the potential for signal interruption is higher. Sometimes the switches don't respond to cleaning, and often enough these days, the part is not easily available, if at all. A general guide to whether it's worth fixing or not, is if the switches aren't easily accessible, it won't be worth fixing.
    A lot of amps are suffering these days because a cassette deck is hooked up into them, and a switch in the deck will cause a high frequency oscillation which can play havoc with an amp. If the amp can respond to a high frequency signal, it will be trying to amplify it, and can overload and cook. The contacts in the deck's switch go bad, and that essentially couples the input signal to the output signal, causing an electronic feedback loop to occur. When it cooks the amp, the most common thing is to get the amp repaired, but to ignore the reason why it cooked in the first place. Chances are it will cook again, because the root of the problem didn't get resolved. The deck doesn't even need to be powered on for this to occur, it just needs to have both sets of patch cords connected to the amp (or preamp, if that's a separate piece). Most people don't accept this as a possibility, since it seems far-fetched, but it's very real. I've seen it at least a hundred times, probably more.
    A really good recommendation for those with oldie but goody stereo systems is if you don't use your cassette deck anymore, then disconnect it (not just the power) and avoid this problem. Remove the patch cords from the amp or pre-amp. The older the deck gets, the more likely it is that it will cause the amp a problem.
    By the way, if one or more of your tweeters have cooked, this is probably the reason why.

    Leave a comment:


  • Paul Alciatore
    replied
    <font face="Verdana, Arial" size="2">Originally posted by HTRN:
    In terms of Digital, go with Legacy Monoblocs...

    .....

    They're also the only amp I know of that will actually go to DC for an output signal

    HTRN
    </font>
    And who's ears are that good? Fact is even the best ears around can not hear under 20 or 15 Hertz. OK, perhaps you can feel it in your skin. But what the hey? Is that really necessairy?

    Likewise, most ears can not hear anything above 20K Hertz. A lot nothing above 10K.

    If I was looking for a better amp I would be looking at other things like signal to noise ratio, crosstalk, harmonic distortion, peak and average power output, power response (most frequency response ratings are for voltage out, not power out. It's a cheat in the way specs are written.)

    Digital in an amplifier is a farce. The output stage is still an analog power amplifier. Digital just adds the possibility of adding digital noise to the mix. Yes, you need it for a digital system but it is not an automatic increase in quality and it is definitely not a way of providing power to drive speakers.

    Paul A.

    Leave a comment:


  • motorworks
    replied
    "Was your QED an integrated amp/preamp or do you have a seperate preamp?"

    John
    It was an integrated amp.
    It sounded very nice. Hand made in the UK.
    It was never turned off in the 18 years, only during a move.(instructions in the owners manual was to turn it on and leave it on!!)
    eddie

    Leave a comment:


  • Excitable Boy
    replied
    Was your QED an integrated amp/preamp or do you have a seperate preamp?

    Cambridge has very little presence in the US these days. I worked at one store back in teh late 80s that sold it. It sounded pretty good, but was not the most reliable stuff. That was a long time ago though.

    In the price range you're looking, a good choice might be someting from Rotel. Engineered in the UK and Japan, then built in tehir own factory in China, Rotel components win a lot of awards for sound quality.

    If you're talking about US dollars they have either a 125 watt ($700.00) or 200 watt per channel ($1000.00) stereo power amp that sounds quite nice. If you need an integrated amp/preamp they have a 60 watt per channel at around $700.00 and a 100 watt per for around $1200.00. The only hang up is that Rotel doesn't allow their dealers to mail order the stuff.

    You might also look into something from Anthem. They are Canadian made so the pricing might be more favorable. Anthem makes nice gear and is a bit more affordable than the Sim Audio stuff.

    John

    ------------------
    Pursue Excellence and the rest will follow.

    Leave a comment:


  • JRouche
    replied
    <font face="Verdana, Arial" size="2">Originally posted by HTRN:
    They're also the only amp I know of that will actually go to DC for an output signal HTRN</font>

    Wonder if you might be thinkin of 1 ohm not frequency. Amp manufacture like to show that their amps will drive very low impedance and will claim they can drive down to 1ohm without damage.

    Or you may be talking about freq response. They will advertize very low freq response even though out hearing response does not go into the range they are advertizing. They will even go very high on the high side into the hundreds of khz touting the need for amplifying harmonic freq. Bunch of sales gimmicktry.

    JRouche

    Leave a comment:


  • motorworks
    replied
    John
    Thanks for the offer.
    I am a long way from So Cal!!
    East Coast of Canada
    I was running a QED A230 amp with Energy Pro-22 Speakers.
    Looking for something in 750-$1000.00 range.
    I only want it for Hi-Fi not home theatre.
    40+ watts or greater, but good sound quality more then "loud noise".
    Where I live there are no high end Hi-fi stores. Back in the mid eightes when I got the amp I had to order it in.
    What do you think of the Cambridge line
    link:
    http://www.cambridgeaudio.com
    There is someone local selling these.
    take care
    eddie



    [This message has been edited by motorworks (edited 05-01-2005).]

    Leave a comment:


  • Excitable Boy
    replied
    I should have clarified as there are some higher end digital amps like Tact out there, but at this time, there's a lot more choices in more traditional designs.

    DC at the output eh? Most amp companies go to some lengths to keep an amp from generating DC. It's kinda hard on voice coils. Turns them into expensive fuses.

    John

    ------------------
    Pursue Excellence and the rest will follow.

    Leave a comment:


  • HTRN
    replied
    In terms of Digital, go with Legacy Monoblocs...

    You'll need two of them as they're mono amps.

    Yer also gonna need a deep wallet as they're something like $2600 EACH.

    They're also the only amp I know of that will actually go to DC for an output signal


    HTRN

    ------------------
    This Old Shed

    Leave a comment:


  • Excitable Boy
    replied
    Much of the better stuff can't be bought over the internet.

    If you've been listening to the QED for all these years, I doubt that you'd be happy with a digital switching amp or much from the big Japanese names.

    Give me some budget guidelines and tell me about the rest of your system and I'll make some recommendations. I've worked in the hifi business for over 20 years and these days make my living as an independent manufacturer's rep. . I spend a lot of time visiting hifi stores and doing product training for the eleven manufacturers I represent. I probably couldn't sell you anything directly, but if you're near toe So CAl area, I could definitely point you to the right store and probably arrange a friendly price.

    John


    ------------------
    Pursue Excellence and the rest will follow.

    [This message has been edited by Excitable Boy (edited 05-01-2005).]

    Leave a comment:


  • motorworks
    replied
    Thanks guys
    Been doing some looking and came across this
    Canadian making amps.
    Have a look at his factory:
    http://www.simaudio.com/tour.htm

    take care
    eddie

    Leave a comment:

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