Heavy vs. light power section

[pickles]

Sound program material with an even spectral balance at low SPLs tends to sound thin, with little bass and high treble. This is a phenomenon of human hearing. At higher SPLs the auditory system's bass and high treble response improves greatly and the overall frequency response becomes more even.

This characteristic is beyond anecdotal; it's well known enough that many stereos have a "loudness" switch that boosts low and high frequencies at lower volume settings, to compensate for the SPL-based variations in the ear's frequency response.

Right. Those are the F-M curves. Well established and wonderful. But "quiet" vs "loud" isn't the question. We're talking about "loud" vs "a TINY bit louder". That is the entire basis of your claim.

When auditioning two amps through speakers at about 100db, how much of a difference is 1-2db of additional output going to make in the perceived frequency content of the signal?

 

[Bob Lee (QSC)]

Not everyone auditions at 100 dB. Some people try out one rig at 100 dB and another at 90 dB and then complain that the softer one isn't as loud and ballsy.

 

[Dragonlord]

Well, still, that should apply both ways, so you would have just as many people saying that their lightweight amp sounds fuller than a 40lbs amp they A/Bed it against.

 

[pickles]

Well, still, that should apply both ways, so you would have just as many people saying that their lightweight amp sounds fuller than a 40lbs amp they A/Bed it against.

+1

I'll continue judging with my ears at as fair of volumes as I can arrange.

 

[Jeff A]

How come, when it comes to a conversation in which the lightweight amps are criticized for lacking something, the answer is always proper gain matching, different input sensitivity between the two, etc. (or should I have said mostly because today it is more directed towards volume and although very related, there are subtle differences to the discussion).

The question:
When are the makers of the lightweight amps going to design the amp so the input sensitivety is the same between their heavier and lighter models.

If this is the driver, it seems like a simple fix that could lead to more sales of the more expensive models and less back trouble for all.

The bewilderment:
What I can't figure out is why so many people audition a DB750 or similar amp at a greater volume than one of their lightweight breatheren. Don't they know this is an unfair comparision and they may be passing up on the amp of their dreams.

 

[greenboy]

How come, when it comes to a conversation in which the lightweight amps are criticized for lacking something, the answer is always proper gain matching

I thought it was poperly conducted double-blind tests, which includes but isn't only about gain matching.

; }

Actually there is some merit to that argument if you believe as I do, that a lot of people hear with their eyes, or by peer group proxy.

* * *

I think there have been a fair number of papers written about the effect of unmatchesd levels swaying people to choose the louder system regardless of whether the components were actually changed or not. Also some about how innacurate and subjective human hearing is even for "golden ears", as environmental effects and moods, diets, fatigue, etc all play a part.

Anyway, those who say "prove it" on either side of the equation could as easily LOOK for proof on the net instead of expecting the other parties to always expend the effort, and then have it shrugged away afterwards.

We all pretty opinionated - so I guess that shows how subjective it all really is.

 

[el_Kabong]

I've heard differences among power amps. But only in sighted tests.

But in double blind tests, going by sound alone and not knowing which amp I was listening to, those differences always managed to vanish.

If you believe A to be better than B, even if A=B, A will sound better to you.

Bob, have any of the double blind tests you've seen (can you see a double blind test? ) involved bass players testing with an instrument in their hands, as opposed to subjects just listening to the amps? I suspect that results may differ with players as opposed to listeners as listeners get no sense of feedback and response from an amp.

I agree that preconception can easily lead one in the wrong direction, but I also think that to a player an amp has a feel. What consitutes that feel in scientific terms I don't know, but amps don't all feel the same to play. The audience might not know how hard I'm working to punch out those notes but I do. An amp that jumps under my fingers probably sounds 'loud & ballsy' to me to some degree because it feels loud and ballsy, if that makes sense. I'm not strictly comparing lightweight vs heavy amps, just thinking of amps I've played.

I might well be completely wrong, but if double blind player tests of amps haven't been done it would be interesting to compare results to the listening only tests.

 

[greenboy]

That's certainly a point with heads and preamps, but...

 

[Bob Lee (QSC)]

Bob, have any of the double blind tests you've seen (can you see a double blind test? ) involved bass players testing with an instrument in their hands, as opposed to subjects just listening to the amps? I suspect that results may differ with players as opposed to listeners as listeners get no sense of feedback and response from an amp.

I agree that preconception can easily lead one in the wrong direction, but I also think that to a player an amp has a feel. What consitutes that feel in scientific terms I don't know, but amps don't all feel the same to play. The audience might not know how hard I'm working to punch out those notes but I do. An amp that jumps under my fingers probably sounds 'loud & ballsy' to me to some degree because it feels loud and ballsy, if that makes sense. I'm not strictly comparing lightweight vs heavy amps, just thinking of amps I've played.

I might well be completely wrong, but if double blind player tests of amps haven't been done it would be interesting to compare results to the listening only tests.

I don't know of any that have, but what you describe--how the amp feels and responds to your touch on the bass--would still be a matter of gain. If the gains are matched on the two amps being compared, then you'll still just be dealing with just the sound.

I lent Passinwind my ABX comparator for a while so that he perhaps can do just what you propose.

 

[Passinwind]

I don't know of any that have, but what you describe--how the amp feels and responds to your touch on the bass--would still be a matter of gain. If the gains are matched on the two amps being compared, then you'll still just be dealing with just the sound.

I lent Passinwind my ABX comparator for a while so that he perhaps can do just what you propose.

That's part of my plan actually, but only if we go through the standard drill with recorded material and find no meaningful differences. I'm hoping to do this on Sunday actually. Anyone from the Portland area (or beyond if you like to drive) can PM me if they want to come out to the Gorge and check it out.

 

[joegeezer]

I have heard enough guys, who use the light weight amps, all say that they hear a slight delay in the attack from those amps, that I've got to say that I beleive them. I've personally never used one, but I think the technology will have to get a little better before I rush out to get one. The price point difference at this time is also a drawback for me. I think a persons ear is the real tell tale test for any amp or cab. All the figures in the world don't mean squat, if it doesn't sound right to the guy with the fingers.

 

[Bob Lee (QSC)]

I have heard enough guys, who use the light weight amps, all say that they hear a slight delay in the attack from those amps, that I've got to say that I beleive them. I've personally never used one, but I think the technology will have to get a little better before I rush out to get one. The price point difference at this time is also a drawback for me. I think a persons ear is the real tell tale test for any amp or cab. All the figures in the world don't mean squat, if it doesn't sound right to the guy with the fingers.

Why do you believe there is a delay in the attack? Power amps don't delay the signal.

 

[greenboy]

I have heard enough guys, who use the light weight amps, all say that they hear a slight delay in the attack from those amps, that I've got to say that I beleive them.

Yes. I had to replace all the lead sleds in a PA system once because there was one Class D amp there and it sounded like a digital delay line was in use for those frequencies. Getting rid of all the lead sleds had a benefit besides the low weight. We could put down our instruments and go on break to chat up the barmaids while the music was still playing. That made guitarists very happy!

 

[seamonkey]

I have heard enough guys, who use the light weight amps, all say that they hear a slight delay in the attack from those amps....

How about listing which brand/model of amp had this problem so other can confirm or avoid. I do know of any brands that have this, so it doesn't look to be a general problem.

 

[pickles]

Anyway, those who say "prove it" on either side of the equation could as easily LOOK for proof on the net instead of expecting the other parties to always expend the effort, and then have it shrugged away afterwards.

The natural state of affairs for any two devices designed to do the same thing is that they would perform differently in reality. Bob claims that the state of the art in power amps is so advanced that it is impossible for one to behave differently from the next, which I find hard to swallow. Power amps are very complicated pieces of equipment, why would you ever expect they all perform exactly the same? Because they are "designed" to? So I'm to trust the guy building and selling the amp, huh?

The burden of proof is on the guy making the claims which are contrary to the natural order of things. Until I see somebody put the amps on a scope and measure the waveforms on a real-world signal, I'm going to have trouble believing that all amps are created equal. I'm not big on taking leaps of faith.

Actually, I do recall seeing such a test that showed a dramatic difference in the low frequency response of conventional and switching amps under load. There were also differences among the various conventional amps. It was posted here, and my analysis of the data was blown off, as opposed to explained away.

http://www.talkbass.com/forum/showthread.php?p=2753281&highlight=PLX#post2753281

I went out and found some proof of the non-identicality of power amps from a third party on the net, and I was ignored.

 

[pickles]

And I've also finally had enough of this argument.

I've had lots of amps, and I think the PLX amps sound very good. I also think that a Crest CA (or even the old FA) amp sounds slightly different, with more weight and authority in the lows, and a slightly different texture in the highs. I've only done unscientific A/Bs at low to moderate volumes, so I'm not even talking about headroom or volume issues. I've always tried hard to listen at the same volume, and used like basses and cabs. The PLX always came across as "punchy" and the CA was "deep and clear", and it wasn't as subtle as I expected it to be. At the time I had been fully indoctrinated in the "all amps sound the same" camp, and my ears (not my preconceptions) told me that I was wrong.

I've never seen, heard, or read anything that would make me believe they respond the same. I hope people in the future search when asking these questions, since I'm tired of playing the devils advocate.

 

[joegeezer]

The one amp that I remember a post on here about, that the player said had a noticeable delay, was the Peavey DPC1400X.
It also was the amp, that I was thinking about getting. I have also read posts on here , saying that the Stewarts had the same type of an audible delay. They all have said that it wasn't much of a delay, but it was noticeable to their ear. That is all I have to go by, as I have never actually played through one, or owned one, and I probably won't, until the prices come down to the point of the heavy amps. It just issn't worth the extra money in my book.

 

[greenboy]

The one amp that I remember a post on here about, that the player said had a noticeable delay, was the Peavey DPC1400X.

He was wrong. I have that amp. It's done PA duty and its been a mainstay in my bass rig since it was introduced. Wroking in sound reinforcement I've run a lot of different amplifiers over the decades of all types in systems I couldn't even personally afford (or justify anyway) adn I don't think I've EVER heard a single functioning amp that had [/b]ANY[/b] perceptible delay.

It also was the amp, that I was thinking about getting. I have also read posts on here , saying that the Stewarts had the same type of an audible delay.

Used them too. Again, no delay. Got links for these? I don't say I will refute them but I'd like to at least laugh or cry ; }

They all have said that it wasn't much of a delay, but it was noticeable to their ear.

I wonder then how those amps have sold to so many people whose profession is live sound.

That is all I have to go by, as I have never actually played through one, or owned one, and I probably won't, until the prices come down to the point of the heavy amps. It just issn't worth the extra money in my book.

If you are shopping merely by price I can tell you that you will generally get amps with poorer signal to noise ratio, often other perceptible and generally acknowledged specs inferiorities as well. But for bassists that might not matter so much anyway, because a poor s/n is usually in so much other backline gear that hiss is practically wallpaper ; }

 

[Bob Lee (QSC)]

Pickles, I'm not building and selling anything. I'm just telling you what power amps do.

Sure, it's possible for an incompetent designer to develop a power amp that can't reproduce the signal with extremely high transparency, but I think its fate in a competitive marketplace would be less than optimistic.

Power amp performance, like many audio devices, is not an uncertain and open-ended thing, like there's always something that could sound better. It's asymptotic, meaning it can approach but not exceed an ideal, which is faithfulness to the input signal. And yes, the state of the art in pro power amps has been extemely high fidelity for many years now.

 

[Dragonlord]

OK, what I'll try to do one of the next weeks is take fullrangebass and his EA iAmp800, my Eden WT550 and go to the greek dealer of Carvin to A/B/C compare them to the B1500 at similar volumes. I'll try to also use the preamp from the Eden for example into the power section of the Carvin. This way we'll have two un-biased opinions - I'm just not sure how soon this can happen, as we both work and live in different towns... but when it happens I'll let you know how it went.