actual power output?

[Kaa]

Sometimes, when I read Agedhorse's posts, I feel a bit of my brain leak out my ear. It is so far above my CPU capacity it's stunning.

 

[byacey]

Ahhhh yes, Behringer watts LOL.

The last band I was in, when I went to audition it was just a drummer and a guitar player. The drummer had gone on a buying binge and bought some kinda Behringer powered mixer with built in effects and supposedly like 1,000 watts. He also had Behringer speakers.

Well it sounded like ass and the power amp section was clipping just getting over the guitar player, the drummer (he did play loud) and my Ampeg B2-R with a single 2 x 10" cab.

The jam went well and we decided to go ahead and "form a band". I asked the drummer if he minded it I brought over some of my PA stuff the next weekend, he said "great" because he realized the Behringer thing was not getting it.

So I brought over a 12 channel Mackie Onyx mixer, a QSC PLX-1602 and a pair of EV speakers. Oh yeah and an Alesis Wedge for effects. This is what I call my "tiny PA for small gigs" setup.

Even though the PLX was putting out maybe 600 watts total it just mopped the floor with the Behringer. I kind of nicely explained to the drummer the Behringer thing re: watts and all and he sent all the stuff back that week as he had only purchased it a couple of weeks before.

I also explained to him most powered mixers were not sufficient for what we were trying to do (did I mention he played REALLY loud) and what he really needed was a mixer and a dedicated power amp.

Powered speakers with high powered Class D amps were just starting to appear back then and most did not sound that good and a lot of them were rather unreliable. Things are very different with that today of course but I still prefer a dedicated power amp with speaker lines. Running A/C cables to everything all around the place gets old really fast.

But yeah, the formula goes "Behringer watts /4 = actual watts" LOL

Analogeezer

The general rule of thumb in my observations, is the cheaper the product, the more likely the manufacturer will hype the specifications, for marketing purposes. This is to target the potentially unwary consumer.

Most of the pro audio manufacturer specifications are pretty accurately published. To violate this would be a disservice to their reputation in the industry.

 

[Piper Bob]

1. Music is not a continuous sine wave, it has dynamics which are reflected in the duty cycle or crest factor of the waveform. Uncompressed, undistorted bass runs around 12.5% duty cycle which equates to 1/8-rated continuous power. Compressed or distorted bass is around 25% duty cycle which equates to 1/4-rated continuous power.

So if a class D amp is drawing 100 watts from the wall when playing music, would it be fair to say that it's "real world" power rating is probably something like 400 watts?

 

[agedhorse]

So if a class D amp is drawing 100 watts from the wall when playing music, would it be fair to say that it's "real world" power rating is probably something like 400 watts?

No, I can derive via math exactly what the rated RMS output would be (based on a few easy assumptons)

If the rated input power is 100 watts from the power source, and the overall efficiency is 80% (typical of an average class D amp with SMPS), working backwards from this number:

100W x .85 = .125X

X = 100W (.85/.125)

X = 680W RMS

 

[seamonkey]

At this time i don't own a high power resistive load so I cannot measure maximum output. I looked on Ebay and can get a 1`00 watt load for around 40 bucks. I just posted this here to make sure so one else was already doing

I was getting at that by you saying new class-d aren't as loud based on what you hear you may just be using your ears.

Ears don't work. they are not consistent. Distortion make perceived loudness louder. At high volumes, ears change, there are built in muscles that clamp your hearing down to protect your ears. So a louder amp may kick in those muscles and make it seem quieter. Hearing just changes all the time. Not a good measure.

Real instrument measurements are what it takes. There's no standards for bass amps, but you sure can get them for FOH pro amps.

 

[seamonkey]

Maybe some year COMMON AMPLIFIER FORMAT

 

[agedhorse]

Maybe some year COMMON AMPLIFIER FORMAT

Which works fine until you intentionally alter the response of the amplifier to achieve a specific characteristic... ie. damping factor, overload character emulation, compression (especially frequency dependent), etc.

 

[fdeck]

Works perfectly for audio. Most class-D things would melt - or at least thermally shut down / limit - if expected to deliver the rated high power continuously. And with audio this is not an issue.

That's strictly a design decision, and applies to Class-AB amps as well. Either can be designed to stay afloat under continuous full load. Or not.

There have been TB threads about Class-AB amps being driven into thermal protect mode.

 

[teemuk]

That's strictly a design decision, and applies to Class-AB amps as well. Either can be designed to stay afloat under continuous full load. Or not.

You're correct. I think the whole design principle just gets more evident with class-D due to its "conveniance" of pumping power ratings to a whole new level. Where with even class G and H the former high power amps were real lead sleds, with class-D they are now commonplace items size of a lunchbox.

But yes, it's not strictly related to class-D. Mesa's "dynawatt" (TM) is a good example from guitar amp realm of quoting momentary burst power ratings. How come they can get 25W output power from just two EL84's (when everyone else gets just 15)? Easy: it's not a continuous rating, and after the power burst the screens sag to voltage that limits nominal plate dissipation to safer levels.

 

[agedhorse]

You're correct. I think the whole design principle just gets more evident with class-D due to its "conveniance" of pumping power ratings to a whole new level. Where with even class G and H the former high power amps were real lead sleds, with class-D they are now commonplace items size of a lunchbox.

But yes, it's not strictly related to class-D. Mesa's "dynawatt" (TM) is a good example from guitar amp realm of quoting momentary burst power ratings. How come they can get 25W output power from just two EL84's (when everyone else gets just 15)? Easy: it's not a continuous rating, and after the power burst the screens sag to voltage that limits nominal plate dissipation to safer levels.

This was the original concept behind the Hitachi class G “Dynaharmony” design, the high rails of the output stage were only for transient power and not for continuous power. This goes back to the mid 1970’s.