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General Asylum: Power amp brain dump. . . . by Pjay General audio topics that don't fit into specific categories. |
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This is blog format, so apologies on editing, length and rant factor. In fact it may not even make sense!It seams every year I take a single stepping stone toward the great audiophile pie in the sky. This year is it power amplifiers. A good friend is an amplifier designer and brought some power measurement equipment over to play*. We listened to a number of tracks and tried a couple of amplifiers. Some amps did quite well while some well rated amps did not come close to the rated power, no surprise there. What was a surprise were the actual requirements of the amp. I had always thought 60 watts of good power were plenty, that is what my professor in college used to say . . . in 1977. What we found is that playing most anything loud runs about 5-8 watts average. But within that average are a lot of peaks up to 300 watts or more, that is as high as my amp went. For all I know, momentary peaks could cross 5000 watts. Ray Kimber’s gunshots did not register at all, too short a read for a signal that is probably uses lot of momentary wattage. At first, this was fun and that was that. But this little test tipped off a lot of thinking about power and amps and tubes and the whole shebang.
What this means is that most amps are clipping at normal listening levels. It is not a question of when the amp is clipping but how much at any given point. I generally don’t listen very loudly, but this test showed that even at a comfortable levels, there is some clipping. Given the harshness of an amp that is in full clip, logic would suggest a lot of the SS harshness is minor clipping. Stay with me here, so far this is elementary but I am about to go off track and into the ditch.
I am suggesting that in a concert, the lack of clipping is a major ingredient in the clarity. Conversely, at home, perhaps short clips are one of the major sources of harshness. So some people use tubes to cut that clipping harshness. That would explain why a 10 watt tube amp can sound good. At 10 watts, it is only clipping a small percentage of the time. So many prefer a tube amp softening the peaks than a SS amp clipping them. The sin of omission is better than the sin of distortion. I can live with that.
So if preamps, CD players, and other line level components don’t clip the sound at some point, operating within design parameters, then the need for tubes does not exist. Unless the unit is artificially voiced to sound tubey. So either a line level device must also clip or we simply prefer distorted sound. Again, if both SS and tubed line level devices clip, tubed devices will sound better for the same reason as larger amps. Or more expensive SS line level devices clip less than cheap ones. I can live with that.
I got some validation of this last week in an audio shop in Berkeley, one of the few shops I have been to who a) were really nice, b) had the rooms set up pretty well and c) did not run around the rooms talking and adjusting things while I listened. But in the middle of this oh so very pleasant excursion (listening to Halcro, Wilson and CJ) the sales guy made an incredibly insightful and obvious point; “at this level, you won’t hear much difference between tubes and SSâ€. Hmmm. What he probably meant was the *I* would not hear much difference at this level. I can live with that.
What I think he was really saying was that when the wattage of the SS amp is high enough to remove almost any clipping, you don’t need tubes to suppress the clips and the amps will sound similar. I can live with that.
While I would never claim this narrow path to cover all the issues in amp design, I think this is clipping distortion one of the key points. The next question is why SS amp designers don’t (except NAD) include a soft clip circuit as part of the basic design. My amp buddy says they are not hard to do and a number of people have done them. Must be something I am missing. I can live with that.
Brain empty now, back to work.
My next question is why do people think we can hear every little phase distortion in a speaker, yet in a concert hall, the instruments are spread out all over the place and there is no planned phase relationship? Did that last Stones concert sound bad because some roadie put the bass speakers two feet back from the lead guitar speakers? Is a long row of violins all in phase to every audient?
* We will have this power measurement setup at DIY DC on Oct 22.
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Topic - Power amp brain dump. . . . - Pjay 11:24:10 10/14/05 ( 63)
- Remember that Carver ad wherein a sissor-snip correctly needed a 1,000 watts? - Elizabeth 10:43:25 10/16/05 ( 0)
How can the average power output be 5 to 8 watts when a typical speaker will play 88dB with one watt = VERY LOUD - Richard BassNut Greene 11:32:44 10/15/05 ( 4)
- SPL @ 1 m does not = SPL @ listening position ( nt ) - Sean 21:34:50 10/15/05 ( 3)
- You might learn something by measuring SPL's at various locations within a typical listening room -- your post is wrong - Richard BassNut Greene 13:26:06 10/16/05 ( 2)
- A while back I measured the level of some FM interstation noise with my RS SPL meter. - Pat D 23:27:44 10/18/05 ( 0)
- You might learn something by looking below ( and above ) the surface - Sean 13:45:21 10/16/05 ( 0)
Volume and clipping. - Chris Jennings 04:51:09 10/15/05 ( 4)
- This overlooks energy storage in speakers. - Al Sekela 12:34:59 10/16/05 ( 1)
- Re: This overlooks energy storage in speakers. - Chris Jennings 14:05:47 10/16/05 ( 0)
Re: Volume and clipping. - Ozzie 10:51:18 10/15/05 ( 1)
- Re: Volume and clipping. - Christine Tham 15:34:17 10/15/05 ( 0)
I think you've nailed it, Pjay - Feanor 04:34:57 10/15/05 ( 0)
This is not what tube amplifier advocates argue - Soundmind 03:48:58 10/15/05 ( 6)
- Re: This is not what tube amplifier advocates argue - morricab 01:32:42 10/17/05 ( 0)
You're saying that those who enjoy tube amps - Bersani 18:48:36 10/15/05 ( 2)
- Re: You're saying that those who enjoy tube amps - Soundmind 21:08:15 10/15/05 ( 1)
- Re: You're saying that those who enjoy tube amps - Bersani 09:22:25 10/16/05 ( 0)
Interesting. I like the "to pad down shrill speakers". nt - Pjay 06:48:08 10/15/05 ( 1)
- Re: Well I did agree with... - Dave-A 11:23:13 10/15/05 ( 0)
Thanks - i pretty much came to the same conclusion myself a few weeks ago - Christine Tham 03:12:38 10/15/05 ( 15)
- Things are a little bit different in your case - Jacques 05:53:18 10/15/05 ( 5)
- Re: Things are a little bit different in your case - Christine Tham 15:22:45 10/15/05 ( 4)
- Re: Things are a little bit different in your case - Jacques 16:49:12 10/15/05 ( 3)
- With all due respect ... - Christine Tham 18:17:30 10/15/05 ( 2)
- Re: With all due respect ... - Jacques 01:51:03 10/16/05 ( 1)
- Re: With all due respect ... - Christine Tham 06:04:54 10/16/05 ( 0)
Re: Thanks - i pretty much came to the same conclusion myself a few weeks ago - Jacques 05:51:12 10/15/05 ( 0)
IMO, 110 db peaks are ear shattering and possibly dangerous - Soundmind 04:10:38 10/15/05 ( 7)
- you should never attend live events if you are concerned - Christine Tham 15:27:40 10/15/05 ( 6)
- Perhaps there are peaks of 115 db where your mikes are near the musicians - Soundmind 15:52:50 10/15/05 ( 5)
- No - the mics were positioned at roughly where the "best listening seat" is - Christine Tham 16:39:47 10/15/05 ( 4)
- Re: No - the mics were positioned at roughly where the "best listening seat" is - Soundmind 16:51:24 10/15/05 ( 3)
- Re: No - the mics were positioned at roughly where the "best listening seat" is - Christine Tham 18:10:29 10/15/05 ( 2)
- Re: No - the mics were positioned at roughly where the "best listening seat" is - Soundmind 18:32:12 10/15/05 ( 1)
- Re: No - the mics were positioned at roughly where the "best listening seat" is - Christine Tham 19:21:52 10/15/05 ( 0)
Possibly lame questions about distortion from a technical ignoramus. - Rick W 17:49:13 10/14/05 ( 2)
- Nothing lame at all .... - Sean 18:01:07 10/14/05 ( 1)
- Read your last post. I lack your tech. knowledge, but I'm coming from the same place. nt - Rick W 18:40:28 10/14/05 ( 0)
Re: Power amp brain dump. . . . - Bruce from DC 14:19:25 10/14/05 ( 3)
- Not accurate at all.... - Sean 15:04:50 10/14/05 ( 2)
- Jeez, I'm glad I asked, Sean - Bruce from DC 15:36:26 10/14/05 ( 1)
- Re: Jeez, I'm glad I asked, Sean - Sean 17:37:48 10/14/05 ( 0)
Great article, Pjay ... - andyr 13:57:32 10/14/05 ( 4)
- measurements - Pjay 19:24:23 10/14/05 ( 3)
- Re: measurements - andyr 20:03:52 10/14/05 ( 2)
- Re: measurements - Pjay 06:41:49 10/15/05 ( 1)
- Hence ... active is better! ... - andyr 14:32:22 10/15/05 ( 0)
RE: SS vs. Tube - Audiopolous 11:52:18 10/14/05 ( 15)
- Clipping versus damping factor and other things. - Presto 14:54:51 10/14/05 ( 10)
- Too many variables here... - Sean 17:44:28 10/14/05 ( 3)
- We should mention this one too - Jacques 04:45:36 10/16/05 ( 1)
- Same things i said before, but i did miss some other important factors - Sean 08:44:23 10/16/05 ( 0)
- I forgot to mention this one.... - Sean 17:57:12 10/14/05 ( 0)
Re: Clipping versus damping factor and other things. - Steve Eddy 16:17:24 10/14/05 ( 1)
- Re: Clipping versus damping factor and other things. - Presto 17:49:19 10/14/05 ( 0)
Hummm.... - Audiopolous 15:41:24 10/14/05 ( 3)
- Re:No showboating intended sir. - Presto 17:55:06 10/14/05 ( 2)
- Spikes etc. - John Swenson 17:43:23 10/15/05 ( 0)
- Oh jeeze, no problem at all!!! - Audiopolous 21:03:17 10/14/05 ( 0)
Re: RE: SS vs. Tube - Doc B. 14:39:27 10/14/05 ( 3)
- Re: Explodential=tubes - Dave-A 07:28:38 10/16/05 ( 0)
Potato, Potato, let's call the whole thing off ; ) -t- - Audiopolous 15:33:11 10/14/05 ( 1)
- You forgot Potatoe. ;) - Dan Quayle 16:20:01 10/14/05 ( 0)