Author Topic: Headroom  (Read 90 times)

Offline dbsfgyd1

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Headroom
« on: December 01, 2017, 07:52:50 AM »
I had a discussion on TalkBass.com with regard to headroom specifically about the 3db of headroom Eden Amps are touted to have, bs class D amps. It was stated by several that this was just a marketing ploy by Eden to sell rigs.

Through the this discussion I came to the conclusion that I may not know what “Headroom” is. All I know is what I hear, and I’ve not had a lack of dynamic response running Eden gear as I have with class D amps.

Could somebody explain what it is, and is there validity to Eden’s claim. Thanks.
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Offline Paulinderwick

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Re: Headroom
« Reply #1 on: December 01, 2017, 08:38:17 AM »
Headroom describes the effect you get at higher volumes with an amplifier - so my WT330 is rated at 330 watts into 4ohms but actually it could handle a transient of double that amount - hence the 3db headroom without being 'stressed'.  If I were a dishonest manufacturer I might claim my WT330 is rated at 660 watts into 4 ohms but to attempt that would be distorted and dishonest because you could never achieve that result in practical use.  However my WTX260 is a Class D amplifier and will give me (I'm in the UK at 230 volts) 290 watts into 4ohms but no more than that - it is a digital head so the amplification is generated by a digital process and cannot exceed - it would just stop working (never happened yet) when it reaches that maximum figure.  As a result you might say that in analogue terms, the terms of the WT330, it would be more honest to claim a maximum of 145 watts... Now this is a topic we have discussed before and most people (I think I'm right in saying) would say that the Class D amplifier should really be described in those terms.  Objectively there is very little difference, it would seem, between an amplifier putting out 290 watts and one putting out 330 but as I use both on a regular basis I certainly would accept that the power handling ability of the WT330 is far in excess of the WTX260.  The WTX260 is light, it's a lot less to cart around particularly if I gig in the centre of town and have to walk extended distances with my gear, I love it and I use it far more than the WT330 for gigging - but when I get the excuse to use the power of WT330 and both of my EX112s I really enjoy it.  I'm no technician which is why I have explained this in terms I understand which might not be wholly technically accurate.  After all an atom is for most of us the smallest particle, as we leaned in school physics and chemistry lessons, even though in particle physics it can be broken down further and further and when you get into the quantum world even stranger things occur.
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Offline dbsfgyd1

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Re: Headroom
« Reply #2 on: December 01, 2017, 02:59:36 PM »
Thanks much Paul. That is really helpful. There was some technical wiz-bang at TB that class claiming D amps have more headroom and made a federal case about it and  was trying to make a jack*ss out on me. Trust me, I’m too good at that without any help. I think in plain English, I would say it is safe to say that the way Eden states it’s wattage  is a more honest approach.

I have played several Class D amps and have come away unimpressed from a performance. They kind of reminds me of a Volkswagen Diesel I owned several decades ago. When you tramped on the accelerator, there was no noticeable surge of power, just a slight increase in noise.
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Offline Rip Van Dan

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Re: Headroom
« Reply #3 on: December 01, 2017, 03:09:47 PM »
Hi dbsfgyd1

What that +3db means is that our musical peaks can be 3db louder  than the normal rms watts sound level would produce without causing the amp to clip.  Just to be clear, a 3 db increase in sound pressure level is technically twice as loud.  HOWEVER the human ear doesn't hear it as twice as loud until it is 10db louder. Nonetheless a 3 db increase sounds to us as significantly louder than the source level. So, when you thump hard on a particular note it sounds louder than your normal playing.  And that is what allows us to have dynamics in our playing. Play softly and it sounds soft - play louder and it sounds louder.

I think the big deal with class D amps has been on how they handle clipping when they reach their maximum output (go beyond the +3db rating).  By far and away most class D amps really start making some ugly sounds when they run into clipping.  Comparatively Eden's class A/B amps also clip an anything over about +3db, but they don't nearly sound so bad doing it.  You don't want to run your amp into clipping because it can damage both your amp and your speakers. With a class D amp, you really hear when you've clipped it without seeing a red LED light up on the amp itself because it really sounds like crap.

To be perfectly honest, I'm not sure I understand this correctly myself, but Armin (Bassman1968) can explain this better and straighten out any mis-statements I've made.  Hopefully he will be along soon and he is really the guru on this sort of stuff.

Dan
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Offline dbsfgyd1

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Re: Headroom
« Reply #4 on: December 01, 2017, 07:05:03 PM »
Thanks Dan. As usual, really helpful information.
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Offline Bassmann1968

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Re: Headroom
« Reply #5 on: December 02, 2017, 03:13:57 AM »
Hi,
Dan got it right. It’s the simple version and understandable for everyone.
For a deeper inside
One keyword is THD. Total harmonic distortion.
https://en.m.wikipedia.org/wiki/Total_harmonic_distortion
Also have a read here
https://en.m.wikipedia.org/wiki/Tube_sound#Harmonic_content_and_distortion
Have fun!
Armin

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