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Old 20th February 2013, 02:28 AM   #8431
a.wayne is offline a.wayne  United States
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You cant get to 106db with 20 watt not even if you are 1 m away and if its a SS AMP you are way past it's sweet spot for sonics at anything near it's 20 watt limit ...
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Old 20th February 2013, 03:05 AM   #8432
fas42 is offline fas42  Australia
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That's where the audio industry has "got it wrong", so to speak. An amplifier shouldn't have a "sweet spot", if it does it's faulty, it's as simple as that. That's what all those beautiful THD, IMD numbers are supposed to tell you, that the amp has no problems in any area, but of course it does, your ears are telling you it's not working properly at high volumes. Those impressive distortion figures are essentially completely meaningless in terms of assessing how good an amp really is ...

A lot of the time my 20W amp would be running in the 5 to 10W range, that's about right for getting realistic piano volume. It's class AB, but the heatsinks are stinking hot because it's really being worked hard. But it doesn't sound stressed or outside its "sweet spot", because such a thing doesn't exist for it ...

Frank
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Old 20th February 2013, 03:14 AM   #8433
a.wayne is offline a.wayne  United States
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I guess we are going to have to agree to disagree Frank , 20 watts cant power your speakers to 106 db and it takes a whole lot of speaker and amplifier to get realistic Piano sound and levels ....

Very Big speakers ....

Measure your amplifier's thd vs power , a sweet spot will emerge ...
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Old 20th February 2013, 05:30 AM   #8434
gootee is offline gootee  United States
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Quote:
Originally Posted by a.wayne View Post
I guess we are going to have to agree to disagree Frank , 20 watts cant power your speakers to 106 db and it takes a whole lot of speaker and amplifier to get realistic Piano sound and levels ....

Very Big speakers ....

Measure your amplifier's thd vs power , a sweet spot will emerge ...
Maybe only a "sweeter spot" will emerge. A great amplifier should be all "sweet spot".
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Old 20th February 2013, 07:04 AM   #8435
dvv is offline dvv  Serbia
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Originally Posted by a.wayne View Post
You cant get to 106db with 20 watt not even if you are 1 m away and if its a SS AMP you are way past it's sweet spot for sonics at anything near it's 20 watt limit ...
Scusi, signore Wayne, but he sure can if he has something like Altec Lansing of old, which did 103 dB/2.83V/1 m. Frank might even hit 116 dB before his amp gives up.

Theoretically, with my speakers (which are not particularly efficient, just 92 dB/2.83V/1m), his 13 dBW could go pretty loud in absolute.

While I agree with Frank, just give it a good PSU and you're fine, I must also admit that there is some program material his chip amp might struggle with. I haven't studied the topic, but I believe chip power amps do experience problems with funny loads, as they are pretty strictly protected. For example, a tympani hit - it's low, it's powerful and it will tax the amp, any amp.

Point is, chip power amps don't have the dye for really high currents, so will Motorola please prepare.

Which is why I would investigate Nat Semi's driver chips, which require current stage(s) as an external feature.
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Old 20th February 2013, 07:42 AM   #8436
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Dvv and all . I heard the famous Yamaha class A / A/B amp in a good system about 5 years ago . Previously I had thought it anemic . Not so .

I once went out with a girl who is an identicle twin ( see her sometimes ) . Mildly I chose the wrong sister , Joe was the one . The Yamaha is like that . Joe is 20 W , she will win your heart even though she is the quiet one . Caroline is a little more exciting and can be mistaken for identicle . In life I could not easily have both ( don't ask ) . In electronics we can .

The Hiraga . 100 % right .
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Old 20th February 2013, 08:08 AM   #8437
fas42 is offline fas42  Australia
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Originally Posted by dvv View Post
While I agree with Frank, just give it a good PSU and you're fine, I must also admit that there is some program material his chip amp might struggle with. I haven't studied the topic, but I believe chip power amps do experience problems with funny loads, as they are pretty strictly protected. For example, a tympani hit - it's low, it's powerful and it will tax the amp, any amp.

Point is, chip power amps don't have the dye for really high currents, so will Motorola please prepare.
Life's made easy for my particular beast, because it only has to handle above about 180Hz, and there's no crossover, just uses a simple full range speaker. Separately powered single subwoofer which amusingly enough uses a single LM3886 more than adequately fills in the bottom.

But, an earlier exercise using LM3875 did drive a conventional 2 driver plus crossover box. These chips can put out a transient current pulse of nearly 10A, which should cover most situations.

What has overloaded both of these units, of all things, is opera! A soprano, hitting a pure, sustained note at full volume is very close to driving at high level with an audio oscillator, and the DIY unit started glitching as the internal protection cut in, the HT shut down and had to be powered off and on. In both cases it was thermal overload, the chips were starting to cook themselves ...

Frank

Last edited by fas42; 20th February 2013 at 08:10 AM.
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Old 20th February 2013, 08:20 AM   #8438
fas42 is offline fas42  Australia
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Scusi, signore Wayne, but he sure can if he has something like Altec Lansing of old, which did 103 dB/2.83V/1 m. Frank might even hit 116 dB before his amp gives up.
This reminds me, the active studio monitors are a joke. Supposedly capable of hitting over 120dB, the top of the line Mackie was a pretty dismal specimen, the overload light was flashing continually in the showroom while producing not particularly impressive sound levels. And then the left channel died, and couldn't be resucitated.

Spec's only tell so much ...

Frank
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Old 20th February 2013, 08:40 AM   #8439
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Fas42, does this include Genelec, just to mention one brand? In that case, I have to strongly disagree. Most active studio monitors I heard run circles around the stuff that passes for HiFi.
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Old 20th February 2013, 09:54 AM   #8440
fas42 is offline fas42  Australia
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Fas42, does this include Genelec, just to mention one brand? In that case, I have to strongly disagree. Most active studio monitors I heard run circles around the stuff that passes for HiFi.
Yes, and Dynaudio, JBL, a good range of near field units. I had an idea for a project and wanted to suss out what the commercial units were capable of. Spent a day going to all the pro shops in Sydney, and it was a bit of a shock when doing this exercise to hear their limitations. I suspect far field models would do somewhat better but didn't come across any on the day.

Probably my main criticism is that they all sounded very "small". Yes, they're physically small but if they are low distortion, high dynamics units they should project a bigger sound than they did. They all reminded me of a muscle bound midget trying to show off, and not making a very good job of it ...

Frank
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