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post #1 of 24 Old 03-31-09, 01:49 PM Thread Starter
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types of amps

i am trying to understand different types of amps.......tube, solid, class D, digital etc......how do they differ ?? what do watts per channel for each mean ?? i read somewhere in this forum that somebody is running their 6s on 25wpc !! how is this different than me running the 6s on halo A21 which has significantly higher wpc........sorry if it sound dumb......but wanted some clarity and understanding..........
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post #2 of 24 Old 03-31-09, 05:33 PM
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http://en.wikipedia.org/wiki/Electronic_amplifier

I can't find an article to point you to on watts, so I will wing it from memory.

A watt is unit of power and all you need to know is how many you need.

Start with the sensitivity of the speaker at 1 watt at 1 meter.
Each time you double the distance from the speaker you lose 6db.
To add 3db you need to double your watts.

So if you have a set of speakers with a sensitivity of 90db 1w/1m and you are sitting 4 meters away you will have 90+3-6-6=81db at 1 watt per channel.
90 for the first speaker at 1 watt
+3 for the second speaker
-6 for moving from 1 meter to 2 meters
-6 for moving from 2 meters to 4 meters

So if you want to listen to your stereo at 90db you would only need 8 watts. But if you wanted to watch an action movie 99db may make sense during some scenes that would require 64watts per channel. Now to climb to 105db you need 256watts per channel.

Watts are the easy part now you need to deal with..

distortion (good and bad) tubes add distortion on a good way, most solid state amps distort in a bad way near the top of their rated power.

power supplies (transformer size and capacitance to deal with transients). This is the killer of most cheap home theater receivers. 7 channels at 100watts per channel with only a 450 watt transformer is just not going to work.
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post #3 of 24 Old 03-31-09, 06:29 PM
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power supplies (transformer size and capacitance to deal with transients). This is the killer of most cheap home theater receivers. 7 channels at 100watts per channel with only a 450 watt transformer is just not going to work.
Is there a recommended spec for this? a 1:1 ratio or something?

And when you say it is the "killer" what does that mean? Can't power for loudest scenes to match the SPL in a movie theater, or would this have an impact on all listening, even at moderate levels?

Thanks for the info.
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post #4 of 24 Old 03-31-09, 07:09 PM
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the power supply must be able to supply as much clean power as the amp is capable of demanding.

In most av receivers the power supply cannot supply the rated power to all channels at the same time. This comes into play during loud action scenes. All the detail falls apart. Its still loud, just really sloppy.

I solved this issue on my yamaha rx-v663 with an emotiva upa-2 driving my mains and running 5.1 rather than 7.1 (actually fit my room better). This means the amp in the receiver is only driving 3 speakers.

It made enough of a difference that my wife noticed. :crazy:

As a side note, its not to that hard to setup a home theater to provide higher SPL than a movie theater. Something much harder to create is a two channel stereo system that can sound like you are at a symphony.
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post #5 of 24 Old 03-31-09, 11:36 PM
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As a side note, its not to that hard to setup a home theater to provide higher SPL than a movie theater. Something much harder to create is a two channel stereo system that can sound like you are at a symphony.
No doubt about that. When I first became afflicted with this hobby I was demo-ing music and HT content during my first speaker search. It became quickly apparent that I could leave the HT stuff at home. 2 channel separates the men from the boys.
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post #6 of 24 Old 04-01-09, 02:35 AM Thread Starter
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but how does regular amp differ from tube amps vs solid state vs D class ??

these questions are geared towards finding a good match for the ls series..............right now i am using the parasound halo A21 amps for the ls6 (rather i used to use them as the 6s are still in the boxes)...........
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post #7 of 24 Old 04-01-09, 05:32 AM
 
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All amps are a compromise and you pick what works best for you. For the LS's I'd be inclined to go with some high quality push-pull tube amps that would give you a good blend of lushness and dynamics. You might check on a nice pair of Dodds that Danny is selling.

http://www.audiocircle.com/circles/i...;topicseen#new

The different designs basically are a compromise to maximize a certain aspect - power, efficiency, cost, sound quality, etc. So, the best amp depends on what you're looking for. Here are my general unscientific layman's understanding of the differences - but there are tons of variations and exceptions.

Tubes - Sound better, cost more, less efficient, run hot. I'm currently a tube guy for 2 Channel. The best explanation I've heard for why they sound better is that the type of distortion they produce (low order even harmonics) is not as grating as the type that SS produces, so even if there is more distortion it is less offensive.

Class A - (Can be tube or SS) Best sounding circuit type, runs hot, least efficient, lower power for a particular price point. You most likely need to live with low power or high cost.

Class AB - (Can be tube or SS) Traditionally the most popular design, you give up some sound quality, and add some distortion, but pick up more power at a lower cost. This has tended to be the sweet spot of compromise for a long time.

Class D & T - (SS) Newer technology that is very efficient, originally didn't sound good in higher frequencies and was relegated to sub amps. Recent development has improved them to where many people think they sound better than AB amps and close to class A. This is where amps seem to be moving and seems like it may eventually replace AB as the mainstream best choice, since you can get high power, low heat, high efficiency, small & light packaging and good sound.

Here's a good wiki on the classes:

http://en.wikipedia.org/wiki/Electronic_amplifier

Good luck, but it seems like you've already got a really sweet SS amp, so unless there is something you feel is lacking I wouldn't feel the need to look for something different.

Jim C
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post #8 of 24 Old 04-01-09, 09:06 AM
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Don't you also have to take into account what the ohms rating of the speakers are as to amount of power drawn? for instance, most ratings are all given at 8 ohms. Many speakers are 6 ohm or 4 ohm, which would draw more power.

So a rating for an amp might be something like 100/130/170 wpc for 8/6/4 ohms
(these are not actual values - just an example).

Regards,
Al

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post #9 of 24 Old 04-01-09, 11:49 AM
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Not sure if I would say that tube amps sound better. Itís just a different spice that some people may love and other may hate.

How about looking at it this way? You can build a system that is incredibly accurate to the source, such as a system used by studio engineers. They want to hear every flaw so they can correct them. But if youíre listening for enjoyment you want a system that can hide the flaws and enhance the assets. This means you need to modify (nice word for distort) the sound that is generated. Other than the source, there are two main components that can distort the sound in route to your ears (the room is actually a major component that Iím ignoring) the amp/preamp and the speakers.

Starting with a low distortion amp, you could find a set of speakers that you really enjoy. Or starting with a set of speakers you could find an amp that really works well for you.

A tube system is just a method of getting the sound you want. While it is expensive to get an initial amp, tube rolling is likely cheaper than speaker rolling. If you have a solid state system that you enjoy, itís not a lesser system just because itís solid state.

Given the quality of your current speakers and amp, you should check out a tube buffer. It would be a cheap <$200 way to add some tubeyness to your system. Try out a few different tubes and see if the tube sound is for you.

http://grantfidelity.com/site/B-283+...ocessor+Buffer
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post #10 of 24 Old 04-01-09, 12:56 PM
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Just wanted to share what I have learned about Class D amps. Most Class D amps are at least 80% efficient and upwards of 90% efficient. Translating that means less heat dissipation and less power requirements to reach the rated wattage specified. For example, if a typical Class A amp is rated for 250wpc and generally is only about 40% efficient that means it has to draw 625watts from the wall in order to output at a full 250watts; times that by 7 channels for home theater applications and you've got 1750watts, but in actuality you require a good clean 4375 watts in order to reach that maximum.

Now for class D amplifiers, with its lowest of 80% efficiency that means 250 watts means it will require 450 watts from the wall. Multiply that by 7 again and only 3150 is required to reach its maximum of 250wpc.

As far as Class D amplifiers sound quality lots have changed recently. Originally, what was said was true that the higher frequencies didn't sound all that great, which is why they were used only as subwoofer amplifiers. Fast foward to today, there's a reason why a lot of companies are now starting to use them. The high frequencies have improved greatly. It has the dynamics of a typical solid state, but the highs are smoother like a tube amp. Not exactly like a tube sound, but it's noticeably smoother.
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