What Amplifier Specifications Do You Feel Is Beneficial?

[Downunderwonder]

FTC continuous power rating for JUST the power amp section, with the rated THD for JUST the power section... at all allowable impedances.

I think those are the Trace Watts.

No burst whatsoever handicaps modern output devices though. If some bass appropriate duty cycle is agreed I would be all for that.

Something that lets you know how much weight is behind you when you smash out ringing 1/8 notes for an hour?

 

[Jeff Scott]

...when you smash out ringing 1/8 notes for an hour?

May I suggest whole notes and a tremolo unit; this will save you a lot of energy.

 

[J-Bassomatic]

Well, I am going to add my two cents. AgedHorse, I have to thank you for all the posts I have read, I don't know diddly about EE but I find myself looking up stuff you mention all the time so in a minor way I assume I am getting smarter. For me, I just want to know that this <amp> is going to be loud enough for the situation I am going to be using it in and is it going to sound OK. If I see an amp that is (self) rated at 1000W, 2000 peak and costs 299.00 I am going to question that. Doesn't it come down to the buyer? I am going to admit here that I wanted an inexpensive amp to get back into bass playing, the Rumble 500 is what I settled on because I tried a Rumble 200 amp and I found the sound was great, for the bucks and for the sound and I cannot see a situation where I would need more than 500W (covering my bases as far as headroom ). And it has great EQ FOR ME! The thing is I found it out by trying it. If I was more pro I would have tried a Mesa Amp because they have such a good rep. I guess what I am saying isn't a player's opinion (or experience) as much of a driver as pure spec?
Again, no disrespect intended, your posts are very educational.

 

[Brad Johnson]

Maybe I am missing something here. We provide a 2 ohm rating at the same duty cycle as our 4 and 8 ohm ratings. They happen to be the same as the 4 ohm rating, much the same as a tube amp with impedance taps.

Or do you mean the ability to drive 2 ohms without shutting down easily?

I didn't take this thread to be anything specific to what you offer, I thought it was asking a general question as to what specs people would like to see. So I stated a preference and offered an example of what I considered a fairly useless impedance spec. If an amp can work fine at 4 and 8 ohms but might clip at 2 when pushed... the 2 ohm rating wouldn't lead me to try to use it at that impedance. It either works normally or it doesn't.

The Quilter amp that I use has this disclaimer and because of that I consider it a 4 ohm minimum amp for gigging... which is where I use mine.

 

[Al Kraft]

If an amp can work fine at 4 and 8 ohms but might clip at 2 when pushed... the 2 ohm rating wouldn't lead me to try to use it at that impedance. It either works normally or it doesn't.

I think that's a fair expectation and especially given that some manufacturers might try to push capability simply to be competitive with other manufacturers who have provided rock solid 2 Ohm operational specs (OBTW this is a generic comment and not implying anything about any specific brand).

 

[Brad Johnson]

I'm an electrical / electronic idiot, so I would not even attempt to make suggestions in this crowd.

But, I would only have two 'wishes', if you will:

1) A common set of standard tests / published outputs that EVERY manufacturer would have to adhere to. This might involve changing consumer law, so who knows how that would go . . . .

2) Some sort of similar common standard for cabinets along the lines of the 1 watt at 1 meter sort of efficiency standard, again where any builder would have to use the same tests.

That would take agreement among manufacturers and likely won't happen anytime soon. Probably not a big enough market to try to enforce standardization on.

 

[Brad Johnson]

I think that's a fair expectation and especially given that some manufacturers might try to push capability simply to be competitive with other manufacturers who have provided rock solid 2 Ohm operational specs (OBTW this is a generic comment and not implying anything about any specific brand).

Agreed. I guess someone might use two 4 ohm cabs (or four 8 ohm cabs ) and not push them hard but I think that generally defeats the purpose of carrying the two cabs. The idea of gigging and hoping things don't get "too loud" goes against my model of not making my rig work too hard.

 

[David Jayne]

Estimated resale value, extrapolated over several months/years. : D

 

[agedhorse]

I didn't take this thread to be anything specific to what you offer, I thought it was asking a general question as to what specs people would like to see. So I stated a preference and offered an example of what I considered a fairly useless impedance spec. If an amp can work fine at 4 and 8 ohms but might clip at 2 when pushed... the 2 ohm rating wouldn't lead me to try to use it at that impedance. It either works normally or it doesn't.

The Quilter amp that I use has this disclaimer and because of that I consider it a 4 ohm minimum amp for gigging... which is where I use mine.

Gottcha, didn't quite folllow your comment initially.

 

[jnewmark]

So, what are your conclusions, if any, Andy ? Having read most of the thread, it seems like a lot of us want to know where actual " Flat " is on the EQ , some sort of accurate rating of watts, or output, that's understandable, and where various EQ frequencies are in the EQ.

 

[agedhorse]

So, what are your conclusions, if any, Andy ? Having read most of the thread, it seems like a lot of us want to know where actual " Flat " is on the EQ , some sort of accurate rating of watts, or output, that's understandable, and where various EQ frequencies are in the EQ.

There were some good points made that are likely to show up in future spec. sheets provided I can find a way to make it "reasonably useful". It provided some excellent discussion material, though by adding the (important IMO) information you guys have asked for will result in a spec. sheet like nothing else the bass amp industry has ever seen. That's kind of a scary proposition actually.

 

[Al Kraft]

That's kind of a scary proposition actually.

Please tell me you didn't expect a different outcome after throwing a stick of dynamite and box of easy-light matches out to this crowd...

If it matters, I thought this was one of the more interesting threads I've seen and certainly one where the additional questions raised will likely always outnumber the simple, easy answers.

 

[aborgman]

I hear this frequently, and would just mention that the FTC ratings have nothing at all to do with MI amplification. It is strictly a home entertainment system standard (that has had to changed recently to reflect the amps growing larger and with different technologies). Pro audio and MI audio amps are designed with very different priorities, MUCH higher current capabilities, much higher RMS power output capabilities and different design duty cycles and MUCH more robust protection schemes being a few, that place them way outside the intent and structure of the FCC standards. For example, MI amps are designed to be driven hard into overload/clipping on a regular basis into 4 and 2 ohm loads... and survive for years (or decades). This is something that the FCC doesn't test for because for the home entertainment system application it's not considered relevant, but in the MI amp it's one of the MOST important considerations.

While I agree FCC standards aren't perfect - they're significantly better at representing max continuous power capabilities across a wide frequency range than what is provided by almost any MI amplifier manufacturers.

 

[beans-on-toast]

When I buy a good microphone, it comes with quality control test data for various settings, including a frequency plot over the bandwidth. Blueprinting the performance of each amp would be cool to have as a reference.

Of course, marketing probably wouldn't want to provide this sort of detailed information.

 

[agedhorse]

While I agree FCC standards aren't perfect - they're significantly better at representing max continuous power capabilities across a wide frequency range than what is provided by almost any MI amplifier manufacturers.

Except that continuous power simply doesn't apply to a bass guitar signal. As amps get bigger, it applies less and less because there are no speakers in the world that can survive operating under continuous power conditions.

We have run into this with PA systems, where DSP based protection algorithms are intentionally designed into amps that prevent any possibility of operating at continuous power. This helps both speakers and amps survive better under abusive conditions without any real world performance loss by identifying through signal signature what is normal and what is outside the normal bounds of a signal.

 

[Hoochie Coochie Man]

I expect that DSP protection schemes are more common in powered PA speakers because the load seen by the amp is a known entity.

For power amps to which the user may connect various speaker systems is the protection scheme implemented in a different way? In other words, how do you account for an unpredictable load? Is the amp able to know the nominal impedance of whatever load it is connected to?

 

[Old Garage-Bander]

While I agree FCC standards aren't perfect - they're significantly better at representing max continuous power capabilities across a wide frequency range than what is provided by almost any MI amplifier manufacturers.

FCC standards are codified federal law.
Equipment must meet FCC standards (law) or it will not be allowed to operate within the confines of the FCC's jurisdiction (USA and territories).
To do so will result in fines, loss of licenses, and/or equipment confiscation.
There is no such hammer for the M.I.

 

[agedhorse]

I expect that DSP protection schemes are more common in powered PA speakers because the load seen by the amp is a known entity.

For power amps to which the user may connect various speaker systems is the protection scheme implemented in a different way? In other words, how do you account for an unpredictable load? Is the amp able to know the nominal impedance of whatever load it is connected to?

What is known is bounds of normal operation, things like frequency versus power versus duty cycle, current versus applied voltage versus phase angle between voltage and current. A knowledgeable designer will factor these things into their protection designs.

FCC standards are codified federal law.
Equipment must meet FCC standards (law) or it will not be allowed to operate within the confines of the FCC's jurisdiction (USA and territories).
To do so will result in fines, loss of licenses, and/or equipment confiscation.
There is no such hammer for the M.I.

There is a difference between FCC and FTC. FCC is concerned with radiated and conducted emissions, interference with communications systems, radio and TV. FTC is concerned with trade issues, and how that might apply to consumers on a broad scale.

 

[aborgman]

Except that continuous power simply doesn't apply to a bass guitar signal.

No spec applies perfectly to any signal. Am I running a midi driven synth rig with tons of compression? Continuous power is probably pretty applicable.

Am I using a normal electric bass, playing classic rock? Continuous power isn't very applicable.

...but applicable or not, continuous power tells me (as an electrical engineer) some very specific things about the overall capabilities of the amplifier.

Plus - don't assume I'm only going to use a bass amplifier for bass. It could be used for keyboards, or PA, or any number of other things depending on the situation.

We have run into this with PA systems, where DSP based protection algorithms are intentionally designed into amps that prevent any possibility of operating at continuous power. This helps both speakers and amps survive better under abusive conditions without any real world performance loss by identifying through signal signature what is normal and what is outside the normal bounds of a signal.

What if I'm running pure sin wave synth signals through my PA amp? Doesn't sound at all "out of bounds" to me.

 

[agedhorse]

No spec applies perfectly to any signal. Am I running a midi driven synth rig with tons of compression? Continuous power is probably pretty applicable.

Am I using a normal electric bass, playing classic rock? Continuous power isn't very applicable.

...but applicable or not, continuous power tells me (as an electrical engineer) some very specific things about the overall capabilities of the amplifier.

Plus - don't assume I'm only going to use a bass amplifier for bass. It could be used for keyboards, or PA, or any number of other things depending on the situation.




What if I'm running pure sin wave synth signals through my PA amp? Doesn't sound at all "out of bounds" to me.

Well then, since we are designing the product specifically as a bass amp (not a keyboard amp, not a sine wave reproducer, not a vibration table driver), the most applicable approach is to consider the type of signal consistent with its intended application. Along with this, if you are going to reproduce sine waves with your speakers, you might need to consider derating many of the speakers on the market that otherwise make outstanding bass guitar speakers, because they are designed with a different and clearly marketed application in mind.

I am going to assume that a bass amp is going to be used with a bass. If it isn't going to be used for bass, it's up to the potential user to determine how suitable it is for their particular application. This doesn't just apply to duty cycle, but to input impedance, input sensitivity, high pass filtering, etc.

For bass guitar, continuous power isn't going to give you any additional information specific to the application. Knowing the duty cycle certainly will (and this is something that I have in fact discussed and provided in the past). As an engineer, I presume you would understand why continuous metrics do not apply to non-continuous signals.

Now I do feel that defining the measurement metrics in RMS terms does in fact tell you something, as peak power is nothing more than a mathematical conversion of the same measurement into a different numerical value that is always higher by a factor of 2 (for the RMS to peak conversion of a sinusoidal type wave form). Of course, all this does is piss off the marketing folks as they come form a "bigger is better even if it's exactly the same thing" school.