What Amplifier Specifications Do You Feel Is Beneficial?

[GonzoBfiddy]

From my experience many of the bass amp mfr's don't provide too much of the pertinent info for their products. As 'somewhat' of an audiophile I spend lots of time looking at specs such as THD, damping factor, the 'flatness' of the frequency response across the spectrum, min impedance ratings, etc when I'm looking to purchase hi-end home audio equipment. I honestly have really used a different set of data when choosing my bass gear. Typically, the most important thing for me in bass amp/head/combo and or cabinets is how they sound, how reliable they are, and how flexible they are. I used to be in the "consumer electronics" business years ago and as a rule I would encourage my customers to buy as much power as they could afford when it came to amplifiers because so many other things depend on that factor. When playing live I use different cabinet combinations depending on the type of gig and venue, so I always keep in mind the differing requirements for specific combinations....mainly driver size/number and rated impedance of the individual cabinets. In the situations I have found myself playing in I have always wanted to ensure I had more than enough power for the situation and that the tone didn't suffer from the gear being run too hard (i.e. 'Headroom'). Not sure if that answered your question, but that's my answer.
Peace, Bro!

 

[AshInAmsterdam]

All I look for it watts (for some
Idea of volume) and the frequency band for each EQ knob, though in general I'd expect these to be similar across various amps.

The rest is do I like the sound more than anything.

 

[seamonkey]

For me, there is a distinction between "Amplifier", "Pre-amp", "Head"
Which I think this thread could be titled:
What Head Specifications Do You Feel Is Beneficial?

 

[sawzalot]

I'll just mention the things that I don't usually see but I wish I did:

Power rating with the method used to measure it. "Watts" means nothing without the context of the method used to measure it--FTC is quite different from EIA. So "500 watts per channel FTC, 20-20Khz" tells me a lot more than "it's a 500 watt power amp".

The other thing that is almost NEVER on bass amps, but is important to me, is power draw. How many (electrical) amps are being pulled out of the wall at 1/8 power, etc. As the sound guy for my band, I need to know how many circuits I need and which equipment needs to go on what circuit. The bass amp, if it's powerful enough and depending on the class of amp, sometimes is a factor in that decision.

For the preamp section, the eq points and, if a semi parametric eq, what the Q is preset to. If a one-knob compressor, the compression settings and which ones the knob affects and how.

Tom

 

[sawzalot]

For an amp the is intended to generate harmonics

+1

I don't care one whit about THD. There is a difference between music production and music re-production. My bass amp is in the former category and I care about how it makes my bass sound. I don't care how it does it, if it introduces small amounts of harmonics that weren't in the signal from the pickups, or if it is outputting something entirely different than what I put in.

I *DO* care about THD for hifi stereo amps and my PA power amps--but not my bass amp.

td

 

[maxschrek]

Being able to handle a 2 ohm load is always nice.

 

[Dbassmon]

Power is important to me. Good bass sound needs lots of watts. Great eq. Good Eq points with parametric mids.(which you do anyway). Transparent sound. I want the sound to my bass, not the amp. Two Channels foot switchable channels on the preamp, at least one of them for some tube crunch, maybe with some choices for overdrive character (more than just amount). Light weight, small footprint. Some tone shapes scoop/vinatage.

 

[blubass]

This is kind of where the pondering started, there are additional specs that might be important but there is also the potential to get so buried in the specs that they become meaningless (or worse, confusing) to those seeking information.

I've seen at times, where some manuals actually have explanations of what you're looking at. I know it's sometimes difficult to dumb things down, but not everyone has an engineering degree for audio, or has the inclination to scour the internet for information that may or may not be accurate.

When people ask, "is xxx watts loud enough" I try and reference them to a db chart that shows typical household equipment or senarios and their respective db ratings. If I start in on how identical wattage ratings between two amplifiers don't mean they have the same maximum db production, or that watts aren't directly proportional to volume and discuss the different variables considered, their eyes often glaze over and they're lost.

In the military we called it, "Barney style". Breaking things down into the simplest of terms.

 

[agedhorse]

Reading a bit further I see other did bring up my points. Of course I don't understand how Q is related to dB/octave, or if the idea of a slope is applicable outside of HPF/LPFs.

Telling folks if your frequency knobs are linear or log is a *fantastic* idea. When I was an Eden user I interpolated the frequencies for their classic pre-amp semi-parametric mid filters. My first interpolation was linear, and I got lambasted by people suggesting they were log. Then the Eden team chimed in and indeed they were log! I published new interpolations. The Eden team made me post a disclaimer due to the lack of precision of the pots that the frequencies should still be thought of as approximations.

So judging by this post, the semi-para mid frequency knobs on the ShuttleMax 9.2 should be linear as well? I created an interpolation for myself, and we chatted about that, I actually did post those here on TB...

ShuttleMax semi-parametric freqs, nominal

Those appear to be roughly logarithmic to me @agedhorse, and they come from your data. I hate to throw a monkey wrench in the proceedings, but now I am really curious. Did you switch to linear at Mesa?

Actually they are pretty linear, take the CW endpoint minun the CCW endpoint, divide by two and you end up right around 12:00 in the middle. The anti-log function of the typical log RC function is already handled within the hardware design. Mixing consoles have been doing this for over 30 years, I can't think of an excuse not to do it this way actually. Everything I have ever done with sweep mid eq's and filters in general have used linearized circuit techniques.

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

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.

In the case of the Subway amps, output tube emulation circuitry is included within the power amp signal path that mimics to a large extent exactly what happens when a tube amp is driven near it's limits (well before clipping), in that a gradual increase in harmonics are added in a way that allows the amp to enter and exit clipping in a benign and "musical" way, as we all know (or should know) that MI amps are more often than not operated this way. This is why big tube amps (and a few big solid state amps too) remain popular. A lot of effort goes into making amps usable under REAL WORLD operating conditions.

What specs? Pretty much the same ones that high-end stereo power amps publish. And to the same picky standards...

I worked in that industry as an engineer for less than a year, right out of university. This is one of the most slimy, dishonest, consumer manipulative, marketing driven industries I have ever worked in. Picky standards, yeah... pick a standard, pay your price, and it gets published. I felt like I had to take a shower after every design/marketing meeting, it was that bad. I left when it was clear that the house of cards that marketing had built (for months before I had even started) was going to come down in a very ugly way... and it did. The (smug and cocky) owner lost everything he owned, and ultimately died from the effects of his broken dreams (and the pressure to repay all the "other people's money" he lost too.

Measuring power using Hifi standards, so measuring output between 120 Hz to 15 KHz, with a tolerance of 1db with less than 1% total harmonic distortion in the signal.

"And set things to where we think will be an approximation of the sound we get on another amp..."

Are you saying you're trying to achieve the same sound on 2 completely different amps? Plus, when going out to try other amps, won't you end up fiddling with all the knobs to find the sound that's most pleasing?

While this seems good on the surface, it would be so incredibly time consuming and costly that it's not likely to happen except as somebody's labor of love.

 

[agedhorse]

I've seen at times, where some manuals actually have explanations of what you're looking at. I know it's sometimes difficult to dumb things down, but not everyone has an engineering degree for audio, or has the inclination to scour the internet for information that may or may not be accurate.

When people ask, "is xxx watts loud enough" I try and reference them to a db chart that shows typical household equipment or senarios and their respective db ratings. If I start in on how identical wattage ratings between two amplifiers don't mean they have the same maximum db production, or that watts aren't directly proportional to volume and discuss the different variables considered, their eyes often glaze over and they're lost.

In the military we called it, "Barney style". Breaking things down into the simplest of terms.

Good point. I have always worked to make the manuals as complete and comprehensive as possible, with educational information where it may be helpful (especially when introducing features not yet common within the industry). I have also been told (sometimes by marketing folks) that nobody will read more than 2 pages of a manual, and I'm sure there is some truth to this as well.

Sometimes, we just have to accept that a task is a "no win" project. This is why I am asking these questions here, this is a more sophisticated crowd with lots of diversity (and the comments show this clearly I think)

 

[BassmanPaul]

I think some of the more esoteric specifications that some people have mentioned are overkill. Few people will know what they mean, and would not be likely to be published by other manufacturers so you could make a comparison between various amplifiers. Anything beyond the basic specifications found in the D800+ owners manual would not help me predict how it sounds, or how it performs in various circumstances. I ether like how it sounds, or I don't.

I agree that for most of us 'how it sounds’ is going to be of vital importance. How one can specify that is a big question mark.

For me, using a pre/power system, it’s more about how the pre-amp can set up what I hear in my head. Power can be provided by any number of different power amps.

When I design an amplifier, I’m designing it for me and to suit my needs. What others might make of the system is unknown though I have had many compliments on how my bass sounds.

What I consider important is power and impedance, it has to power a pair of ACME B2 2x10 cabinets. They are 4Ω therefore the amp has to be stable at 2Ω. They require about 500W each so 1KW output. Weight, I’m older than I once was.

Pre-amp, I’d like two channels for when I use two basses. That’s not very often but I have it now. Three band EQ with a sweepable mid range. I’m not into distortion of any kind, spent too much of my life getting rid of it to go back. A separate mute for each channel which I also have at the moment I think that’s about it.

Hope this helps a bit Andy but if not, probable, at least I tried.

 

[Timmy-Watts]

For me personally, a scope of what the amp's "EQ at noon" would be nice. I like visuals.

I also want to know all the ohms going in and out. Sometimes I want to know what I can plug into it (I'm a doubler with frequent upright gigs), and sometimes certain pedals sound better in the effects loop or out front.

The frequency of the HPF, whether it's buried or controllable.

I also like to see a diagram of the feature set so I can see what is affecting what.

And this one is very specific. How does the notch filter on the Rosette preamp work? Is it just always on, and you HAVE to tune it to a frequency, or is it somehow able to be bypassed? Nothing I have read has told me how it works and is making me not buy it yet.

 

[jnewmark]

"This is simply impossible because output level is a function of input signal level gain control position, and eq. There is however an easier way to tell when you are reaching the limits of the amp, that's the output limit LED. The operation and detailed functions of which are discussed thoroughly in the manuals." Well then, let me ask another question. How did you arrive at " 800 watts rms, @4 ohms 10% THD ( includes preamp O/D THD)" ? Where was everything set on the amp in order to arrive at that spec ? Or is it simply a matter of me setting the amp how I want, and then turning the Master until I see the output limit LED come on, which means I'm close to full output at 4 ohms ?

 

[blubass]

I have also been told (sometimes by marketing folks) that nobody will read more than 2 pages of a manual, and I'm sure there is some truth to this as well.

I'd absolutely agree that is true. it's daunting to see soo many words. Often manufacturers have their, "quick start guide" and that is great for the plug and play person. Plug in here, set to these settings, plug into a cabinet of this impedance or that one and off you go, have fun"

However, they always show some sort of technical data which i'd suspect is often skimmed though or altogether disgarded as most people don't understand it. Financially, it may be more feasible to simply add a link in a manual and state, "for a more in depth look at these features, specifications and their meanings go to..." Then you can eat up some digital real estate going in depth without the overhead of more paper for the manuals, staples, blah blah.

One thing that's exciting for us, is we get to pick your brain. I can see the amp specs for a Mesa D800/+ but if I want to know why you picked the determined frequency of an eq knob on an amp, I can simply ask you here. However nice you may be though, there could be 1000 others asking the same thing in different threads and it could get old after awhile. Instead, you can blow up a webpage dedicated to the D800. Your thoughts, feelings, and interpretations of why you decided to do whatever you did with the amplifier, and what it all means. Industry standard definitions of things are great bases for knowledge, but your interpretation and possibly easier wording of such information regarding specific equipment you've designed would be without a doubt a great addition to your already stellar technical data included in the manuals.

 

[GIBrat51]

Well, after agedhorse's angry diatribe that resulted from my post... sorry, and good bye...

 

[HolmeBass]

Thanks @agedhorse I looked at the deltas between the detents and I can see now that they are quasi-linear, certainly much closer to linear than log without a doubt.

So any hope for the slopes of HPF, low and high shelving in dB/octave, and a description of how Q maps to dB/octave slopes on semi-parametric mids EQ? Actually just the dB/octave on the HPF and shelving EQs would be pretty interesting to me, just to start to get a handle on how the shelving EQs interact with the semi-para mids. Thanks.

 

[Chrisk-K]

Accurate built-in tuner as in TC amps

 

[agedhorse]

For me personally, a scope of what the amp's "EQ at noon" would be nice. I like visuals.

I also want to know all the ohms going in and out. Sometimes I want to know what I can plug into it (I'm a doubler with frequent upright gigs), and sometimes certain pedals sound better in the effects loop or out front.

The frequency of the HPF, whether it's buried or controllable.

I also like to see a diagram of the feature set so I can see what is affecting what.

And this one is very specific. How does the notch filter on the Rosette preamp work? Is it just always on, and you HAVE to tune it to a frequency, or is it somehow able to be bypassed? Nothing I have read has told me how it works and is making me not buy it yet.

\

While this has mostly been included within each feature part of the manual, I agree that it might be handy in spec. format.

Good points about buried features, we have in fact described these in more detail than most for this reason and we do include the frequency range of sweep filters (thought these too might benefit from being in the spec section)

We have indeed provided detailed block diagrams for the Subway and Rosette products for the reasons you mentioned, and I find myself referring players to this often.

Ont he Rosette, the notch filter in the full CCW position is effectively bypassed as it's buried under the HPF's rolloff. This avoids the need for (yet) another switch and makes it more handy to tune up from. I will look into discussing the more completely in the manual.

"This is simply impossible because output level is a function of input signal level gain control position, and eq. There is however an easier way to tell when you are reaching the limits of the amp, that's the output limit LED. The operation and detailed functions of which are discussed thoroughly in the manuals." Well then, let me ask another question. How did you arrive at " 800 watts rms, @4 ohms 10% THD ( includes preamp O/D THD)" ? Where was everything set on the amp in order to arrive at that spec ? Or is it simply a matter of me setting the amp how I want, and then turning the Master until I see the output limit LED come on, which means I'm close to full output at 4 ohms ?

Your method will work just fine.

In the lab, I might set the gain/master controls at noon and feed a variable input signal into the amp. This gets to my point about input level going hand in hand with gain. For example, if I turn down the master volume by exactly 6dB, I would have to turn up the input signal level by exactly 6dB to arrive at exactly the same power. I also use a distortion meter and harmonics residuals to achieve the intended design operating point, but this is an internal decision based on my design data and the intended use of the amp. Different amps might be presented differently depending on the application.

Well, after agedhorse's angry diatribe that resulted from my post... sorry, and good bye...

Maybe you aren't that familiar with the "audiophile audio" industry, but there are others here who have also worked in that industry and who have experienced much the same as I (or in one case that I recall much worse. This story was an off the cuff glimpse behind the curtain of a most bizarre segment of audio rather than an "angry diatribe". In fact some of the funniest things I ever saw in audio occurred at this job (including a guy getting confronted by the tag team of his wife AND his girlfriend).

This is an adult thread, with adult discussions, and adult stories. If you don't have a thicker skin, that's ok but you might not want to participate. It's your loss.

 

[bass.slinger]

For most bass players, the only spec required is "loud."

And sounds good....

 

[agedhorse]

Thanks @agedhorse I looked at the deltas between the detents and I can see now that they are quasi-linear, certainly much closer to linear than log without a doubt.

So any hope for the slopes of HPF, low and high shelving in dB/octave, and a description of how Q maps to dB/octave slopes on semi-parametric mids EQ? Actually just the dB/octave on the HPF and shelving EQs would be pretty interesting to me, just to start to get a handle on how the shelving EQs interact with the semi-para mids. Thanks.

Nothing is going to be perfectly linear when performing the anti-log function of the adjustment in hardware, but it's almost always within 10%.

On highpass filters I do provide a detailed discussion and info, because I usually use either a 2 pole (12dB/octave) or 4 pole (24dB/octave) depending on the application.

Q and slope are two independent parameters. For active mid eq, slopes typically resolve to 6dB/octave on each side of the bandpass, the Q does vary with boost/cut. At very small amounts of boost & cut it may be as low as 1 and at high boost/cut amounts might increase to say 4 or so. This gives the impression that the slop is greater though the definition of the slope is what the filter response resolves to. It's useful for the Q to increase with more boost/cut, this way when you are making deeper adjustments they become more precise and less intrusive (in %) on the surrounding frequencies.

The shelving filters are ~6dB/octave and with a Q of a little less than 1.

Good question... hope this helps.