Mini 0r Micro Amps.... I Must Be Missing Something?

[IntrepidCellist]

Psychoacoustics is powerful stuff; without complicated adjectives, the high-end audiophile market wouldn't exist.

I went from an Eden WT400 to an Aguilar TH500. Fairly different preamps, but the Aguilar was punchier and more authoritative to me. And, I saved myself lugging 10-12lbs. across NYC on a trolley!

[seamonkey]

Originally Posted by fdeck

I read it as painting a completely qualitative picture, and drawing conclusions from it, without defining any terms or demonstrating a quantitative basis for those conclusions. This is a schoolboy mistake. It would be like saying that water contains deuterium oxide, and deuterium oxide is toxic, therefore water is toxic.

The audiophile community has a habit of generating verbiage consisting of stringing technical terms together in ways that make no technical sense. This text can seem impressive, if not convincing, to the layperson, while seeming like utter drivel to an expert or serious enthusiast.

The following is drivel:

+1
Many audiophile boards are big on Class-d. Even taking off the shelf pro audio power amps and modding things a bit (quieter fans) and using them in home theater.

I think they started to realize what exactly "transparent" sounds like, or doesn't sound like.

[willsellout]

Originally Posted by agedhorse

Ummmm, the preamps are different?

The GBE-750 uses a totally different preamp than the Shuttle uses, just the summing section can be responsible for significant sound and feel. Playing say the GBE-750 with the ShuttleMax 9.2, which are more similar (but still not identical) would be a closer match based on my lab testing.

A better way to test would be to use the same preamp with the different power amp sections (easily done with the pre send, pwr return insert point at the fx loop) and under those conditions, in a level matched lab environment, I was not able to tell the difference between the 9.2 and the GBE power amps.

I'm not saying either way, I just know there were significant differences in a live situation, which is more applicable than an A/b test in a lab for me. It just really seemed like the 750 seemed to be on another level, similar to the Mpulse when compared to the Streamliner 900 I owned. They just seemed to have more presence. The Mpulse in particular has a really muscular punch to it. There are a million variables, I'm sure, and a million reasons why what I heard is imagined. I'm open to a lightweight head opening my eyes, I just haven't met one that did yet.

[willsellout]

Originally Posted by IntrepidCellist

Psychoacoustics is powerful stuff; without complicated adjectives, the high-end audiophile market wouldn't exist.

I went from an Eden WT400 to an Aguilar TH500. Fairly different preamps, but the Aguilar was punchier and more authoritative to me. And, I saved myself lugging 10-12lbs. across NYC on a trolley!

I really want to try the TH500. I might have to buy one from MF or something so I can return it. If something can take the place of my Mpulse or GK800RB without sacrificing anything, I'm all for it.

[60bass]

Originally Posted by fdeck

Meanwhile, here's what I expect from a power amplifier of any class in a bass amp:

1. The output is just like the input, only bigger.

2. Departures from this ideal at normal signal levels are inaudible.

3. If I push the amp to overload, it will take care of me in a musically forgiving way.

Everything else, I can take care of by tailoring other parts of the signal chain, most likely by using the built-in preamp and being happy. If there are enough other people like me, it would explain why the typical "micro" head lasts about 1/2 hour in the TB Classifieds before getting snapped up.

Regarding #3

I've yet to find another amp where if you overload it the limiter works as well as it does in Genz Benz's amps. IMO it's very musical sounding, never seems to choke the output and one of the reasons I love GB's amps. I always hated the limiters in my previous amps and rarely if ever used them because they squashed the tone and output. Not so with my GB amps. I honestly feel like you're not getting the benefit of just how great the GB amps sound unless you push em till the limiter starts to kick in. IMO it's almost "tube like".

I've owned the Neo-Pak 3.5, GBE1200, Shuttle 6.0, and currently have the Contour 500 single 15. They all have one thing in common. They sound great when cranked due to the way GB designed the limiters.

I don't know if the limiter circuit is the same in each amp but I'm sure agedhorse can elaborate on the differences if any. All I know is that they work and work well

Keep Low

[agedhorse]

Originally Posted by joelb79

I didn't read it as fear mongering. It seemed like a more drawn out text of the same thing this: http://en.wikipedia.org/wiki/Class-D_amplifier

Even wikipedia states stuff about RF, and design limitations and complications. Is mentioning that stuff considered fear mongering then?

These are all design parameters that must be considered when designing a class D amp. Many of the same issues are present in a class AB/G/H amp which we also consider when designing that class of product.

Mentioning it in a way that suggests that ALL class D amps suffer from these problems and that ALL class D amps are inferior to other classes of amp because of these issues is indeed fear mongering because it's inaccurate and presented in a way that is marketing based rather than a factual basis.

A properly designed class D amp suffers from these problems no more than a properly designed class AB/G/H amp.

[agedhorse]

Originally Posted by joelb79

See but pro-touring amplifiers to me are Lab Gruppen, Crown I-tech, ect.. Nobody bothers to call their amplifiers Class D when you are up there. You invent your own class. I just don't buy that they are all popping ice-power units into chassis and calling them "Pro-Touring" amplifiers. I'm staring at gut pictures of an I-Tech right now, and nothing in there looks ice-power at all. They all cost a pretty penny too, like I said thousands.

You are missing all of the powered touring class speakers that use them. Can't say which ones due to non-disclosure agreements but I came from the touring pro audio industry and worked on several successful products that used IcePower modules that have logged thousands of operating hours and millions of tour miles.

There are also many tour products that use the IR chipsets, again very similar in approach. The IcePower folks have integrated some of the technology a bit farther than the IR solution but both can be desgned to perform in a way that I don't think anybody could tell what platform is in the box.

... and Lab Gruppen is not a class D amp. It's a class AB amp with a tracking PWM power supply, which is kind of like a class D amp except a little different. It's based on similar BASH or Sunfire type technology.

... and the I-Tech's use a different modulation scheme to effectively speed up (double?) the slewrate of the high voltage PWM signal. They call it class I which is like class D except a little different.

Everyone has their own twist but the end result is that put into a box, I don't think very many (if any) folks could identify one out of the group at this level.

[agedhorse]

Originally Posted by 60bass

Regarding #3

I've yet to find another amp where if you overload it the limiter works as well as it does in Genz Benz's amps. IMO it's very musical sounding, never seems to choke the output and one of the reasons I love GB's amps. I always hated the limiters in my previous amps and rarely if ever used them because they squashed the tone and output. Not so with my GB amps. I honestly feel like you're not getting the benefit of just how great the GB amps sound unless you push em till the limiter starts to kick in. IMO it's almost "tube like".

I've owned the Neo-Pak 3.5, GBE1200, Shuttle 6.0, and currently have the Contour 500 single 15. They all have one thing in common. They sound great when cranked due to the way GB designed the limiters.

I don't know if the limiter circuit is the same in each amp but I'm sure agedhorse can elaborate on the differences if any. All I know is that they work and work well

Keep Low

The way an amplifier handles overload is indeed a critical (if not THE critical) factor in the way an amp sounds when driven hard. This is also something that I have understood and have worked with intensively for over 25 years, it's not something that was pulled out of thin air. IMO, it's one of the most fascinating parts of an amp.

For bass guitar, all kinds of factors come into play. Using descriptive terms (not totally accurate in an absolute sense), if the attack and release times are too fast, the limiter can modulate the harmonics with the fundamental (nasty), if the attack time is too fast with a slow release time, you can loose some of the leading parts of the dynamic envelope burying what's left, too slow of an attack time and you can get attack envelope artifacts, etc. Without going into any propriatary information, all of these factors, along with operating bandwidths, area under the curve algorithems, supplemental harmonic enhancement and power supply dynamics management all factor into how an amp feels when driven hard. All of these factors also come into play with tube output stages which is what I used as a general approach (I have designed a few large tube power amps, so there's plenty of continuity between tube, class AB and class D products since I work with all of these topologies. The 3DPM technology used in the Streamliners and Shuttle X.2's is just a further refinement of the evolution of our output management techniqies.

[Marcus Willett]

Originally Posted by Shane Carter

I love seeing these tiny things where people have to buy the mounting brackets and mount them in a rack.

Me too, that's why I have my micro amp in a micro rack.

[Jeff Scott]

Originally Posted by Shane Carter

I love seeing these tiny things where people have to buy the mounting brackets and mount them in a rack.

I missed this line; you mean like this?

[B String]

Originally Posted by 60bass

Regarding #3

I've yet to find another amp where if you overload it the limiter works as well as it does in Genz Benz's amps. IMO it's very musical sounding, never seems to choke the output and one of the reasons I love GB's amps. Keep Low

I completely agree with this.

[Shardik]

I have more experience with hifi and home theater audio than instrument amplification, but I find it a bit ironic that the bass community is so sceptical of class D. In Home theater and hifi, the first widespread application of high power amplification was in the bass and subwoofer range, the reason being that class D requires a low pass filter on the output stage that introduces some measurable deviations in the high frequencies if not done properly.

ICEpower, which have had a lot of focus is not a new technology. It has been around since at least mid nineties, and is better documented technically, in principle and in practical use than most other OEM amplification modules, regardless of technology. The availibility of that documentation makes it easier to attack, but since the older, competing technologies rarely offer the same level of meticulous documentation, it is like comparing apples to a nondescript fruit basket.

In home theater subwoofers, class D amplifiers and other PWM topologies rule almost exclusively in the high power range, and work with full control in known commercial subwoofers down to subsonic frequencies (well below 20Hz) with no problems (the limitation is usually in the speaker elements and the cabinet), providing sound that you feel, rather than hear.

I am always baffled by the statement that the heavy equipment based on class A/AB is considered to have more control in the bass range. Measurements do not support that. That said, it may sound like more punch when the amplifier is unable to control the bass elements, and they start to resonate at certain frequencies. That may be more fun, but accuracy may be sacrificed to reach that goal. That is a valid choice.

My bottom line: I have a lot of experience with the larger ICEpower modules (I own a pair of 600W monoblocks in my hifi setup), and I have been involved in a consulting capacity in evaluating custom speaker setups in the $100000 range using high end active crossovers/DSPs and class D amplifiers. Achieving the same control with class A/AB power amps would easily push the price of such a system past the $200000 mark and consume double the power (which would also take its toll on the power lines of said house).

Size and weight is probably what fools everyone into the assumption of "lightweight sound", but it is all about efficiency. Switch mode power supplies do not require heavy transformers, an amp efficiency well above 95% compared to the normal 50% efficiency of class AB means a lot less need for heavy cooling solutions (think less than 10% of the cooling needs for a class D amp of the same power rating), and also reduces consumed power from the wall to almost half, compared to traditional topologies.

There IS a valid point that when pushing a class D module past its power rating, there is a large increase in THD, but that goes for all amps, and the circuitry preventing that overload or makes it detoriate in an ear pleasing manner is a challenge for both class AB and class D. I have pushed enough SS class AB preamps and small combos into clipping overdrive, and honestly it sounds like s... That is why you may prefer tubes or sometimes some FET transistors that do this more gracefully. But if you want a clear, articulate bass sound, you have lost no matter what topology you choose if you push the amp hard into overdrive.

The prices for good class D amps are also usually lower than their AB counterparts. The reason is simple: Large transformers and heavy cooling solutions (usually fans and a lot of aluminum) costs a lot of money in parts. In a competing market this means good class D can be had for less than equally powerful class AB.

So it is really down to what you hear. Myself, I hear transparency in good class D amplifiers. I also hear that in class AB amplifiers, but they weigh and cost more to achieve the same power and clarity. I know what my next choice will be.

[KJung]

Originally Posted by willsellout

I'm not saying either way, I just know there were significant differences in a live situation, which is more applicable than an A/b test in a lab for me. It just really seemed like the 750 seemed to be on another level, similar to the Mpulse when compared to the Streamliner 900 I owned. They just seemed to have more presence. The Mpulse in particular has a really muscular punch to it. There are a million variables, I'm sure, and a million reasons why what I heard is imagined. I'm open to a lightweight head opening my eyes, I just haven't met one that did yet.

This is again a case of comparing two things that sound different and then attributing the difference to the wrong thing (power amp design).

1) The original Shuttle 6 had the hi pass filtering set quite a bit higher than the other amps in the line (Shuttle 9 and the heavier heads) due to optimizing the low end for the little Shuttle cabs (that, by the way, also gave these heads an airy, sweet, mid present sort of vibe that quite a few liked versus the fuller low end of the 9 series, and you could expand the low end a bit with the lo filter button if you choose). That, combined with different preamps and different absolute power levels between the 6 and the 750, well duh. You would find the performance more similar with the updated, beefier voiced low end of the 6.2 (using the same power module). Of course, they would still sound different due to a hundred other differences in execution, and most would like one over the other.

2) Having owned the MPulse600 and the Streamliner900, Mesa makes a point of using almost no hi passing. For better or worse, they put out bigger low end than almost any amp on the market. The Streamliner is big sounding, but very controlled in the sub bass. So, +1 if are looking for rafter shaking low end, the Genz amps are not really designed to do that for a reasons. That being said, the Mesa heads typically put out more volume than their power rating would suggest... impressive executions.


Again, IMO, you are mis-attributing the different sounds and performance of various amps to the wrong thing. A good example is when many of us moved from the very nice Thunderfunk550b to the Markbass LMII when it came out quite a number of years ago. In GTG after GTG, and gig after gig, it was clear that the LMII was more open, louder in an absolute sense, clearer through the midrange, and have a more extended top end. The LMII was class A/B with SMPS. I guess we all could have come to the conclusion that SMPS driven class A/B amps sound much better than traditional power supplies driving a class A/B amp However, most realized that there were many, many other differences between those amps that explained the difference in performance in the low end, etc.

[seamonkey]

Originally Posted by Shardik

I am always baffled by the statement that the heavy equipment based on class A/AB is considered to have more control in the bass range. Measurements do not support that.

Good post!

I dont think "Measurements" are not allowed here

Even highly experienced engineers of amplifier solutions will not publish measurements. It's left to magazines, and hobbyist with the equipment that can measure.

Measurements are required for FOH pro audio. It's demanded. FTC in the US, requires measurements for consumer audio. It has to have the FTC rating.

MI, measurements are just passed over. They'll write some psuedo specs, but nothing deeper than a few nonsense specs.

Consumers in MI do not demand measurements. And most deny that measurements would do them any good.

[KJung]

Originally Posted by seamonkey

Good post!

I dont think "Measurements" are not allowed here

Even highly experienced engineers of amplifier solutions will not publish measurements. It's left to magazines, and hobbyist with the equipment that can measure.

Measurements are required for FOH pro audio. It's demanded. FTC in the US, requires measurements for consumer audio. It has to have the FTC rating.

MI, measurements are just passed over. They'll write some psuedo specs, but nothing deeper than a few nonsense specs.

Consumers in MI do not demand measurements. And most deny that measurements would do them any good.

There are also a lot of amateurs (like me) who do not know how to interpret the measurements they see (there is a reason guys actually go to engineering school!). There was a TBer who recently (I think in this thread) posted a graph of the distortion levels of a class D module and went on and on about 'this describes what he hears in class D amps'. A number of actual EE's chimed in and said that the graph didn't represent what he thought it did, and that even if it did, a graph of a similar output class A/B power amp would look virtually identical

[NWB]

Originally Posted by willsellout

I really want to try the TH500. I might have to buy one from MF or something so I can return it. If something can take the place of my Mpulse or GK800RB without sacrificing anything, I'm all for it.

Send me a PM if you want to try mine. I live very close to Woodinville.

[seamonkey]

It was a chart meant for engineers. It like when you sit in for a player and they give you a conductor chart to play off. It's not really meant for "you"

But, that's it, if the measurements are the same, the charts look the same, and the amps sound the same.

[Shardik]

Originally Posted by seamonkey

But, that's it, if the measurements are the same, the charts look the same, and the amps sound the same.

I am an engineer, and I can tell you that is not true. One chart never tells the whole truth, and you need the whole truth to know that something is the same. You need a whole lot of measurements to establish a fact like that.

[seamonkey]

I said "charts" and "measurements" plural

[KJung]

Originally Posted by Shardik

I am an engineer, and I can tell you that is not true. One chart never tells the whole truth, and you need the whole truth to know that something is the same. You need a whole lot of measurements to establish a fact like that.

Just to be clear, +1. The point I was making is that looking at one chart only is not going to give you the full story. But looking at one chart without any concept of what you are looking at will DEFINITELY give you the wrong story