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Amplifier FAQ - Page 5

post #121 of 200
7/7/11 at 3:03pm
In the sentence above that you state "distortion is lower at less power output".
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post #122 of 200
7/7/11 at 3:09pm
Thread Starter 
One sentence says distortion is less at lower power. This is true as a ge
neral rule (except at very low power.)

The other says that a more powerful amp means less distortion (all other factors being the same.)

Both are true.
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post #123 of 200
7/7/11 at 3:22pm
In general, would the difference in distortion measurements between a 250wpc and a 500wpc amp (class D) justify a 30% difference in price?
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post #124 of 200
7/7/11 at 3:53pm
Thread Starter 
Quote:
Originally Posted by cougar75 View Post

In general, would the difference in distortion measurements between a 250wpc and a 500wpc amp (class D) justify a 30% difference in price?

Subjective, really. If 250 watts is enough to play your system as loudly as desired then 500 watts would be a waste of money. Remember there's also a limit to what speakers can handle.

If you have sufficient cash, and think you need more power than 250 watts, and your speakers can use it, it might be worth it to you.
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post #125 of 200
7/9/11 at 7:13am
Since a couple of month I am the owner of a DENON AVR-1611 receiver.
One of the reasons to buy this receiver was the possibility to connect an iPod doc station. For this reason I bought the ASD-11R.
For completion, I also bought an iPod touch (4th generation).
Believe it or not, but this combination doesn't work. When I put the iPod touch in the station, it's impossible to get connection.
With an iPhone (4th generation) it's not a problem and also an ipod touch (3rd generation) doesn't give problems.
A visit to the apple store confirmed this. They went deeper into specifications etc and con-firmed.
Because I can hardly imagine that this is true. The latest IPod touch and it doesn't work. I post this mail in the hope someone can help me out.
Here are the questions:
Has anybody experience with this and know how to handle this?
Is there one or the other way a connection or adjustment I forgot?
Hope someone can help me out, thanks in advance.

Leo
Beverwijk
The Netherlands
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post #126 of 200
7/9/11 at 10:21am
^^ I think you posted in the wrong thread.
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post #127 of 200
7/12/11 at 7:45pm
Thank you for the details!
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post #128 of 200
7/18/11 at 12:18am
Nice FAQ - I once asked an NHT engineer about what power he recommends for their speakers, and I got the response "power is tricky thing" - he was right! So kudos for stepping into a potential minefield. Thought I might add my $.02 to the discussion as well.

- "Best sound for my budget?" Purely my opinion, FWIW: better speakers first. Good speakers with a decent AVR are likely to sound better than average speakers with a good amp. Balance is good, but the scale should favor speaker quality over power. Good advice for the less informed, perhaps?

- There are reasons other than volume (loudness) that can justify a higher-rated amp. A lot of folks pick up way more power than they need (i.e. they aren't trying to make their system louder) for the purpose of improved dynamics. You might consider mentioning something about capacitance (more power "ready to go" in a higher-rated amp) and how a 500W amp can deliver more of a "kick" or punchier sound than a 100W amp at a given loudness. While the need for power is often overstated, many claim to hear the difference with more power, especially in the dynamics. Does that make it so? No, but this view is widespread enough for consideration. I've never done A/B testing myself and can't comment.

- Might also correlate the term "headroom" with the lower distortion you'd expect to see from a higher-rated amp at a given loudness.

- I'd clarify the "power damages speakers" discussion. Driving speakers with too much current (power) can damage them. Using a higher-rated amp will not, by itself, damage speakers. Certainly there's a higher potential for damage with more wattage, because the amp can drive the speaker louder. Assuming no clipping, at 100dB, a 1000W amp is no more harmful than a 100W amp. (Likely less, considering the lower distortion.) The reason a 1000W amp is a bad choice for a 100W-rated speaker is that some jackass can come along and crank your stereo to the max: a 100W amp will do bad things in this scenario, but a 1000W amp will likely blow the speaker outright.

- In absolute terms, ACD measurements aren't helpful as they don't accurately represent how power is used in a 5.1/7.1 setup ... but in relative terms, they DO allow us to compare one amp to another. In that sense, ACD is helpful for judging amps and more manufacturers should include it. Another way to look at it: if an ACD measurement is given, it's likely a much better amp than one without an ACD figure. As you mentioned, most AVRs drastically reduce their per-channel output when using all channels, and an ACD figure would give us some indication of the real-world output.

- Consider this link for those concerned about matching the impedance of their speakers: http://www.audioholics.com/education...ector-switch-1
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post #129 of 200
7/29/11 at 7:35am
Thread Starter 
Thanks for the comments.

Addressing a few of them...

Why would a 500 watt amp give you more "kick" than a 100 watt amp, providing the 100 watt amp was not overdriven? By overdriven I am covering clipping, or current limiting. You would have to provide technical reasons for that claim.

I admit to disliking the term headroom, because I feel it's misunderstood. Headroom, by common definition, is power beyond what you think you need to deal with unexpected signal peaks. Say you wanted 100 dB SPL at your listening position for each speaker. You factor in speaker sensitivity and loss due to distance. You decide 200 watts / channel will do the trick. Well, maybe you got it a bit wrong. Knowing this is possible, you decide you want headroom. So you double the power. But that gets expensive! Maybe it's cheaper just to reduce volume a bit. Headroom, IMO, is not dynamics. You should factor in dynamics into your planning - for example using THX's stated 20 dB of dynamic range.

I have probably done a better job with the power vs speaker damage discussion. But I did not see anything wrong with what I said there. It says you can damage speakers with too much power, which is obviously true (but perhaps not common.) You can clearly exceed the speakers mechanical limits or thermal limits, which I did not get into (perhaps the AVR FAQ does a better job with that distinction.) I believe I mention that having more power can be a good thing to avoid clipping.

I won't address ACD Been there, done that. Suffice to say, there's vehement anti-ACD people out there, and vehement ACD people out there. The truth probably lies in between the extremes

Anyway, thanks again for the feedback. I always appreciate it.
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post #130 of 200
9/6/11 at 2:15am
Personally I find that the power output of my ancient HRT-6535 is overkill I do not listen to music or movies at really loud volumes and even when I have pushed the amp it has never produced any oddities...

Seems like even the good amplifiers are getting pretty lightweight now so I am not sure that heft is a good means of judging quality anymore
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post #131 of 200
9/11/11 at 9:26am
One think you didn't address in the FAQ was the use of a pro audio amp in a home theater setup... If one is using a pro studio reference grade amp, would that be quite suitable for a home theater amp??
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post #132 of 200
9/11/11 at 11:29am
Thread Starter 
Quote:
Originally Posted by amosfella View Post

One think you didn't address in the FAQ was the use of a pro audio amp in a home theater setup... If one is using a pro studio reference grade amp, would that be quite suitable for a home theater amp??

It's a good idea. A lot of people happily use pro amps in their HT setups.
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post #133 of 200
9/11/11 at 1:34pm
For what a home theater amp costs, I'd think the pro amp is the way to go... example, a 2 channel 110W per channel at 8 ohm home amp costs about $650 here, while a behringer 2 channel 300W @ 4 ohm studio reference amp is $250 and change....
I can run my 4 ohm speakers (the whole 5.1 setup) for aprox $100 more than a 2 channel home amp costs... Just need a receiver with preouts...
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post #134 of 200
9/16/11 at 8:17am
There are even bigger PKN amplifiers, the newest one has 40.000Watts output power and THREE PHASE(!) 400Vac line. I bet this is the largest amp ever... really, really impressive

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post #135 of 200
9/22/11 at 1:58pm
Thread Starter 
40k watts does not make sense to me even with 3 phase. But I am not sure how that math works.

If each phase could pull 120 volts (not saying this is true,) and 25 amps, and somehow that equates to 360 watts with 75 amps, that's 27,000 watts continuous. I guess you could pull more from each phase without tripping the breakers for a short time. And I would guess it has some capacitor storage, but that has to be limited by a one space form factor.

Interesting, in any case
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post #136 of 200
9/22/11 at 8:53pm
Quote:
Originally Posted by MichaelJHuman View Post

40k watts does not make sense to me even with 3 phase. But I am not sure how that math works.

If each phase could pull 120 volts (not saying this is true,) and 25 amps, and somehow that equates to 360 watts with 75 amps, that's 27,000 watts continuous. I guess you could pull more from each phase without tripping the breakers for a short time. And I would guess it has some capacitor storage, but that has to be limited by a one space form factor.

Interesting, in any case

But if the voltage is at 240 or 480 then it's doable.
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post #137 of 200
9/22/11 at 11:09pm
Thread Starter 
Quote:
Originally Posted by Gooddoc View Post

But if the voltage is at 240 or 480 then it's doable.

I know Crown's 10,000 watt amp used something like 3 phase. I never did the calcs on that one, but I am sure that one was pretty legit...I think one of it's main uses was to drive some medical imagry equipment (MRI? CAT?)
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post #138 of 200
9/29/11 at 8:47am
I have a Yamaha V571 . Would I benefit from a amp?
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post #139 of 200
9/29/11 at 4:47pm
Thread Starter 
Try posting to the main forum for more responses on that.
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post #140 of 200
12/19/11 at 7:05am
Hello everyone, I have been looking for a decent 5 Ch amp for a while now, and over the weekend I walked into a local high-end audio dealer and may have made an impulse buy!

I purchased a Parasound Halo A52 5 channel amp....its being used with my Integra 7.6 DTR receiver which has unbalanced pre-outs, so it will "act" like a pre-pro and both amp & Receiver are driving Elac's FS 247's LRC SR SR in a 5.1 configuration.
I set it up over the weekend and WOW, I can truly hear a difference especially at louder volumes (no distortion or muddiness) as compared to before.
Anyway, I am not here to talk about that but to ask if it is necessary to run the Integra's audio calibration set up again. In all honesty everything sounds "right", I just want to know what the concensus is on this!

PS. I paid $ 800.00 Can for the used A52 in the box absolutely flawless, and it included 5 "Canare" 3' cables, I think that's how its spelled, did I pay it too much?

Paul
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post #141 of 200
12/20/11 at 9:43am
Thread Starter 
Repost this in the forum. Posts in this thread should be about the FAQ (and you will get better responses by posting to the AVR/Amp forum.
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post #142 of 200
2/5/12 at 12:30pm
I just want to say a big thanks to the OP for writing this FAQ. I always wondered what the hell a amp/prepro was and what it was used for. Reading the sticky clarified a lot of questions I had.
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post #143 of 200
2/5/12 at 12:35pm
Thread Starter 
Glad it helped
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post #144 of 200
2/24/12 at 3:58pm
If I want to build a 2.0 system for now and perhaps 5.1 in the future, will a 7.1 AVR overkill or it doesn't matter? It's for the bedroom and not going to be too loud at most of the time. Thanks in advance for your comment?
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post #145 of 200
2/24/12 at 9:00pm
Thread Starter 
Repost your question to amp/receiver forum. Posts in this thread should be about the FAQ (and you will get better responses by posting to the AVR/Amp forum.)
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post #146 of 200
3/9/12 at 1:26pm
Is there sort of a standard range for external amplifier input sensitivity and gain?

Or if not, does anyone know how big of a swing in gain there can be with typical HT amps?
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post #147 of 200
3/10/12 at 6:24pm
Thread Starter 
Most are in the 1 V to 1.3 V range for input sensitivity.
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post #148 of 200
3/10/12 at 6:28pm
Quote:
Originally Posted by MichaelJHuman View Post

Most are in the 1 V to 1.3 V range for input sensitivity.

What about gain, is there a similar range and is it tied to wattage?
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post #149 of 200
3/10/12 at 8:51pm
Thread Starter 
Quote:
Originally Posted by rnrgagne View Post

What about gain, is there a similar range and is it tied to wattage?

If I recall, it's something like this...

Gain = 20 * log ( v1 / v0)

So 28 dB of gain is 25 time voltage?

Say the amp was 120 watts...

p = v^v / r [ into 8 ohms]

So then voltage is 31 Volts at peak wattage? (Never can remember if I have to factor in peak vs average)

So if voltage gain is 25 times, then input sensitivity must be ... 1.25 volts?
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post #150 of 200
3/13/12 at 9:01am
Dear Friends,

My name is Sudhakar and I need some help in making a decision to buy a good Amp/Receiver.

I have decided to buy the BOSE 901 Series VI with EQ.

I wanted to know what is the ideal AMP / Receiver that I should buy to get the best performance out of 901 series. Here again, I did some study (to my limited knowledge) and have an inclination to buy Yamaha product but considering the variety of options available, I need help to decide on a particular model that complements Bose 901 to its best.

As an alternative to Yamaha, if you have suggestions for other brand/models, please do give me your thoughts.

Price is not a constraint here and I am only looking at getting the best combination for Bose 901.

Looking forward to suggestions and inputs.

Regards
Sudhakar
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