What Amplifier Specifications Do You Feel Is Beneficial?

[Old Garage-Bander]

Features rather than specs...

Anyone have a virtual amp on the market yet?
A box with all the usual I/O, but no knobs or switches, save for a power switch.
It has a built in webpage with WI-FI and copper Ethernet access.
Control panel is what you design it to be to display on your iPad/phone or computer.
All features are programmable and includable, or not.
You want para EQ? Make it para. You want graphic? Go graphic. Set up as many EQ knobs as you want.
Make the pots act like linear, audio, something in between.
Include meters, scopes lights, switch types, knob styles.
Even design you own logo and give it a name.

And of course, a fully comprehensive spec sheet and operators manual encompassing all the good stuff we've discussed here today.

Any of that out there yet?

 

[trevcda]

Interesting... why would a 20kHz power spec, or even a 20Hz power spec be appropriate for a bass amp...

...Normally for bass amps, I use 30Hz - 5kHz for rated power testing (your tweeters would last maybe a few mSec at 5kHz) but there would be no difference at 20Hz. I don't do rated power tests (other than duty cycle controlled) above 5kHz due to Zobel network protection.

I got side tracked in my head and started thinking about sub amps rather than bass amps. I always hated seeing an amp's rated power listed at a frequency that I'll never use, just because it looks good on paper. And the second part of what I quoted from you above, is exactly the kind of info I'm interested in.

 

[Passinwind]

Features rather than specs...

Anyone have a virtual amp on the market yet?
A box with all the usual I/O, but no knobs or switches, save for a power switch.
It has a built in webpage with WI-FI and copper Ethernet access.
Control panel is what you design it to be to display on your iPad/phone or computer.
All features are programmable and includable, or not.
You want para EQ? Make it para. You want graphic? Go graphic. Set up as many EQ knobs as you want.
Make the pots act like linear, audio, something in between.
Include meters, scopes lights, switch types, knob styles.
Even design you own logo and give it a name.

And of course, a fully comprehensive spec sheet and operators manual encompassing all the good stuff we've discussed here today.

Any of that out there yet?

I've had a preamp quite a bit like that for quite a few years now: [Invalid or Expired Link Removed]

My matching power amp also has DSP controllable via a Windows GUI.

 

[SLivinghouse]

Assuming that you are asking about a combo amp and not just the head.
1) What SPL will it create without perceivable distortion
2) What SPL will it create with distortion without damage for 2 hours
3) How much does it weigh
4) Polar response curve (or at least 180 degrees in front) at flattest setting in anechoic chamber - on and off axis - similar to mic spec
5) AC low voltage/high voltage tolerance
6) can it survive fluid spills - similar to IP 67 spec on mobile phones
7) Input impedance (suitability for piezo pickup)
8) MTTR for warranty repair service
9) If bi-ampable, what are the cross over frequencies that can be selected

Steve

 

[HolmeBass]

I think this is just terminology, I use head, amp, amplifier all interchangeably.

Yes, me too, but if I make a distinction about a head I don't say it has a pre amp and an amplifier; if I make a distinction about a pre amp then the other part of the head is a power amp, not just "an amplifier", which is what the poster I was answering was saying. They were saying an "amplifier" was just part of a head, rather than synonymous with "head". I took a difference to that; I don't think that is terminology many use.

 

[ThisBass]

Frequency switches are not always documented well. What exactly does the Deep/Bright/etc switch do on an amp?

Valid point. Even Ampeg did never exactly explain the Treble switch for V4 and SVT amplifiers.
So let me do what Ampeg never did since late 60's. That's now rougly 1/2 century.

The effect caused by Treble Boost does interact with different volume adjustment.
E.g. the Treble Boost effect will be biggest if you need only very less loudness volume you control with volume knob of the amplifier. In this case you will add a very "bright" and very intense amount of Treble frequencies to your sound

The Treble Boost effect will add "more balanced" amount of Treble to the sound if you play on stage and need more loudness level you adjust with rather highish volume knob settings

The Treble Boost does have no effect nothing at all if the volume knob is cranked all the way up.


As the Treble Boost is interactive with volume on (oldish) svt and V4 amplifiers I used to EQ the amplifier this way. I try to figure best "balance" of volume adjustment and Treble Boost and adjust loudness level needs with the bass guitar.

 

[xk49w]

I'd like to see some kind of clueful consumer-level specification that told something about the amplifier's linearity and power output capability. There are tests and spec's that could be devised but frankly I don't think they would be useful to the average consumer.

How about the amplifier's power output at the 1 dB compression point?

• It is a single, steady-state number useful for comparison.
• It is single tone measurement so is relatively independent of tone controls.
• It would account to some degree for baked-in compression or limiting, though other tests would be better.

The THD at the 1 dB compression point could be interesting though IMO might be a bit too much information.

 

[groovaholic]

Bass Gear mag specs amps with RMS output at 40 Hz.

That strikes me as both an empirically measurable and practically applicable number to indicate real-world capability for bass amplification.

 

[agedhorse]

I'd like to see some kind of clueful consumer-level specification that told something about the amplifier's linearity and power output capability. There are tests and spec's that could be devised but frankly I don't think they would be useful to the average consumer.

How about the amplifier's power output at the 1 dB compression point?

• It is a single, steady-state number useful for comparison.
• It is single tone measurement so is relatively independent of tone controls.
• It would account to some degree for baked-in compression or limiting, though other tests would be better.

The THD at the 1 dB compression point could be interesting though IMO might be a bit too much information.

Interesting idea, but single point isn't always an accurate description. Some amps include frequency dependent compression, some with adaptive compression where threshold, attack, release, hold and ratio vary with level and how quickly the signal approaches the threshold.

 

[Old Garage-Bander]

I'd like to see some kind of clueful consumer-level specification that told something about the amplifier's linearity and power output capability.

I'm not sure what you are trying to get the specs to say here.

An audio amplifier, by it's very nature, is linear until it is driven into distortion or compression is applied.
Even if the process to get there is not linear, the output is, and that's what matters.
And power figures that are not measured under stable conditions are tantamount to stretching the truth, which we do suspect that some manufacturers tend to do.

If by "clueful" you mean dumbing down linearity and power stability specs, I'm not sure how you would do that.
Power is measured in watts. It is a technical thing, that is already about as basic as it can get yet still explain the power.
Stability is measured over time. Would your specs show power at a certain level to be stable over 1 hour, or four, or a day?
And do those stability specs relate to real world use? In most cases, no. So what's the reason for wanting something that has no bearing on how an amp will perform at the next gig?

At some point, the person reading the specs has to take some responsibility to understand the very basics.
After all, they learned to read, and bothered to read the specs. They have some relative concept about power, at least that more is good. They understand the concepts of time. They can usually do simple arithmetic and math. So just take a few more minutes to read up on Ohms law.

Now if "clueful" has a different meaning than what I inferred, then accept my apology for the mini-rant.
I just think at some point, drawing pictures for people to explain power is beyond the scope of what a spec sheet should do.

 

[Old Garage-Bander]

Bass Gear mag specs amps with RMS output at 40 Hz.

That strikes me as both an empirically measurable and practically applicable number to indicate real-world capability for bass amplification.

That spec that tells you nothing about how well an amp will work in the mix. Which when it all boils down, is what we really are interested in knowing. Is Amp A going to do a better job at my next gig than Amp B?

It's the harmonics of 40 Hz (a slightly mis-tuned E string) that should be of more interest to players. Why focus on frequencies that do more to suck power and are not well heard? 40 Hz by itself is mud. Care about 80 Hz and up through around 5K or so. Just about any amp out there can do that with little or no trouble, likewise for your ears.

 

[tombowlus]

Bass Gear mag specs amps with RMS output at 40 Hz.

That strikes me as both an empirically measurable and practically applicable number to indicate real-world capability for bass amplification.

Actually, we have not done that since issue #1. Our output power tests for continuous and burst power employ specific modules in the Audio Precision APx software. The burst power module uses the CEA-2006 test standard, which is limited to testing at either 50Hz or 1kHz. In light of the high-pass filtering issue and other issues, we use the 1kHz option.

 

[sawzalot]

Ok so I had another thought. I focused my last post on sort of technical things--current draw, the standards used, etc. But not so much on the musical aspect. So here's another one:

For heads with a digital preamp section, I need latency specs. My head has a digital preamp and it has low latency but trying to find that spec was a nightmare. It's an important spec because all the new 2.4 ghz wireless units are digital. Some have very low latency and some are quite high. So (wireless latency) + (digital preamp latency) + (digital mixer latency) = actual delay to my IEM mix. When you combine the 3-6ms from my wireless, 2.5ms from the head, and 2ms from the digital mixer it starts to add up. I used a new-ish digital preamp pedal with >7ms latency and the delay became audible and threw me off to the point where I had to get rid of it.

Regarding power amp specs: These days I don't care much about power amp specs beyond the electrical current draw. I use IEM's 95% of the time and rely on the PA amps to deliver the volume. My bass is loud in my ears vs the other instruments and that's all I need, plus the rumble from the PA subs. For the few gigs I do without IEM's my little micro-head is fine.

So what specs are important from a musical standpoint? EQ frequency points. Things like "low", "low mid", "high mid", "high" are next-to-useless to me. For semi-parametric EQ's I want the Q and frequency range. Compressor attack, decay, hold, release, knee, etc paramaters are nice to have. Latency is really important also, for digital preamp sections. Any built-in LPF or HPF cutoff points are important too. Another technical spec: if it has a preamp output, the output voltage is important to match the input sensitivity of a power amp.

Tom

 

[xk49w]

Interesting idea, but single point isn't always an accurate description. Some amps include frequency dependent compression, some with adaptive compression where threshold, attack, release, hold and ratio vary with level and how quickly the signal approaches the threshold.

A 1 dB compression measurement made after the dynamic behavior has settled out is no more or less an accurate description than a steady-state power spec', because that is really what it is. It would indicate (for the steady-state case), where the amplifier is starting to run out of gas. IMO it would be a useful supplement to the usual "some power @ some THD". OTOH, the steady-state power output at 10% THD gives somewhat similar information.

Measuring dynamic behavior - that's something for the amp reviewers in their labs to do. There are ways it could be specified I suppose, but I see no way that would make sense in a consumer-level product data sheet.

... Now if "clueful" has a different meaning than what I inferred, then accept my apology for the mini-rant...

None needed. (I couldn't tell what you inferred .) I was using "clueful" in the sense of the consumer being technically aware of what such a specification means. It could be a stretch on my part.

 

[longfinger]

So I'm sitting at my desk pondering some thoughts for an update of specifications provided, and while there are a ton of possible specs. to include I think many of them are virtually meaningless to the overwhelming majority of players. Of course there are some important ones as well.

Now's your opportunity to state your opinions as to what an "ideal" amplifier spec. sheet should contain. As ideas come up, I may wish to discuss them to be sure we are on the same page.

The one thing I am not going to accept are disrespectful posts however, and this is not (yet another) class D amp debate as the class of amp does not matter for this discussion.

(I didn't read all of the previous pots to date)

- A measurement of SPL level 1 meter in front of the cabinet with THD ratio (based on a standard signal like a sine wave or similar). It would be great if all speaker companies did something like this. The 1 meter is just an example. Point is, sound level a certain distance from the speaker before a fixed number of THD is reached. The more capable a, amp-speaker combo is, the higher SPL rating before the fixed THD is reached. (It could also be the SPL level is fixed, but the rating is from the THD at that SPL level. Though I think buyers would be more interested in "how loud can it go before it starts to sound bad")

This can be problematic with tube amps where THD might be high but is aesthetically pleasing.

- Acknowledgment of where the knobs have to be to give a "flat" response. (Since most amps have a built in voicing when all the knobs are set to neutral.)

 

[GreyBeard]

RMS at 1% distortion, damping factor at 8 ohms, tone control specs, a spec that describes its' cooling efficiency

 

[agedhorse]

A 1 dB compression measurement made after the dynamic behavior has settled out is no more or less an accurate description than a steady-state power spec', because that is really what it is. It would indicate (for the steady-state case), where the amplifier is starting to run out of gas. IMO it would be a useful supplement to the usual "some power @ some THD". OTOH, the steady-state power output at 10% THD gives somewhat similar information.

Measuring dynamic behavior - that's something for the amp reviewers in their labs to do. There are ways it could be specified I suppose, but I see no way that would make sense in a consumer-level product data sheet.

This is kind of an important distinction, since a lot of perceived "feel" is bound up in this sort of performance spec. You are suggesting to quantify an almost purely dynamic behavior with a purely steady state metric. With some products (and likely even more as this technology and approach evolve), the result will be more inaccurate than you might imagine. It also neglects the (intentional) effects of burst power headroom combined with controlled overshoot which may be responsible for some of the more unique aspects of feel with a few very highly regarded amps on the market. As an extreme example (and I am citing Hitachi research from the 1970's here), having an amp with short dynamic headroom of 3dB above their "continuous" capability, with sufficient time duration to account for the attack, hold and decay envelope, will appear to have the same loudness and dynamic impact as an amp that has twice the continuous rated output but with no dynamic headroom. This was the very beginning of the understanding of how important dynamics management really was, and how it could be possible to apply technology to get more out of a similar sized package by intelligently managing the dynamics. It was ground breaking technology, and of course it has evolved a lot from those early days. Bob Carver was probably the first to grasp the importance of the concept and the potential for exploitation, in his case with his 3 tier "magnetic field" controlled amps (which used phase control) to improve the highest tier efficiency.

To accurately describe the behavior of a multi-dimensional algorithm (either analog hardware OR DSP based) would surely infringe on IP aspects of a design as there are companies in the world who seem to specialize on developing competing products based on another company's R&D. I don't see the benefit of making this any easier (read as "less costly") for them. Besides, for non-engineer types, the published data would not be at all useful, what's important to most players is how the amp feels/sounds to them.

Dynamic and steady state are two very different aspects of amp performance, and different designs play on the performance benefits between the two extremes, as it suits their goals.

 

[Dave Hill]

RMS Power at 2/4/8 Ohms.
Freq's and db's of any knobs/switches.

 

[agedhorse]

(I didn't read all of the previous pots to date)

- A measurement of SPL level 1 meter in front of the cabinet with THD ratio (based on a standard signal like a sine wave or similar). It would be great if all speaker companies did something like this. The 1 meter is just an example. Point is, sound level a certain distance from the speaker before a fixed number of THD is reached. The more capable a, amp-speaker combo is, the higher SPL rating before the fixed THD is reached. (It could also be the SPL level is fixed, but the rating is from the THD at that SPL level. Though I think buyers would be more interested in "how loud can it go before it starts to sound bad")

This can be problematic with tube amps where THD might be high but is aesthetically pleasing.

- Acknowledgment of where the knobs have to be to give a "flat" response. (Since most amps have a built in voicing when all the knobs are set to neutral.)

I see here you are headed with this, but there are all kinds of amps, not just tube amps, that employ harmonics addition in a variety of ways to generate a pleasing (to many players) more interesting, less sterile tone. This is going to be an even bigger thing I predict in the future, and already is in a big was with DSP processing like Axe-FX, Two Notes, etc. where harmonics are generated based on calculations made from not just the instantaneous signal but maybe looking ahead (via a slight delay) a few cycles and accumulating some of the past cycles to get a better perspective on what the signal is about to do next. This is all happening on a very small time slice but is way more comprehensive than an instantaneous "data" sample.

Also, when voicing a speaker that you wish to be overdrive friendly, a designer may choose to modify or take advantage of the non-linearity of the magnetic field at the edges of the gap where they are not straight but are slightly curved. On a speaker like this, the distortions will rise at a lower rate but somewhat earlier in the power curve. The (usual) goal in these instances is for the transition to real non-linearity to be smoother, less abrupt, and thus more useful as a tone sculpting tool. These effects will also vary greatly with frequency!

This is a tough task to describe in a way that gives a single (even marginally useful) useful number IMO.

 

[agedhorse]

RMS at 1% distortion, damping factor at 8 ohms, tone control specs, a spec that describes its' cooling efficiency

What if the 1000 watt amp reaches 1% THD by design at 50 watts? Or what if the super-coveted and highly regarded tube amp doesn't ever dip below 1%? I think we will find that designing to "marketing numbers" will result in some pretty uninspiring amps lacking in mojo, sterile, unforgiving of overdriven operation, etc.