agedhorse

This could certainly be part of it, though I have heard from players in the EU who have received their Subway amps (including a few TT's) so it's possible that a limited number of amps from earlier shipments were already sold. Just because a shipment enters the country doesn't mean that it hasn't been sold to another customer who was already waiting, I don't know how dealers manage waiting lists. I don't have this information, and it's not really my area. I am trying my best to be helpful and provide honest, transparent information. Obviously I am sometimes wrong or miss an important detail, but I can assure you that it's not intentional on any level. I do understand everybody's disappointment, really.

I don't know what may have happened or why such delay, though there are constant shipping issues with inland freight at both ends, at the ports, on the water through customs and in destination transportation. I'm not making excuses, and I am truly sorry for your experience. I really do understand and appreciate your frustration.

There are many ways to skin a cat, what is critical is understanding the difference between real performance and marketing performance. There are also plenty of companies/designers that did not understand how the ratings were derived and how the protection schemes were mapped to the various performance parameters, so in order to keep their products from shutting down (or failing), some chose to derate the modules in order to make them work. This is true of several of the modules, where there are different levels of performance depending on the amount of engineering that a company was willing to invest. Regarding the 250ASX2, there is a lot of hidden additional performance available provided the designer understands the intricacies of the part. I actually have a patent on some aspects of this as it relates to this part and it's based on close to 20 years of historical hands on design experience with IcePower products going back to some touring pro audio products I designed or consulted on. The more you know about a subject like this, the more you realize that you don't know... and the more interesting it becomes.

Their implementation is different than most others IME. It's just how they chose to use that part. There is also a lot more to the IcePower specs than what's published, in fact most of the important information about the module resides between the lines, and requires a lot of experience to exploit safely, with high reliability.

Designers design (or should design) for worst case conditions, different regions have different needs and a product needs to be able to be used in most habitable locations. Your choice may be different than another player's choice, therefore (most) amps are designed for everybody's possible choices and if a fan bothers you enough, you can seek out an amp without a fan.

Do I see a market for gold plated horse manure?

We do a 3 week long event (pro audio) with 6 or 7 sound systems (small up to arena size) and we design everything around 105 deg F (~40C), everything works fine for hours and hours but that's because everything is designed around these ambient conditions. As long as a designer is aware of the conditions, it's not that big of a deal. It might involve derating things a bit, but generally it's not a big deal.

Yes, there have been quite a few cases of designers underestimating how much effort goes into a successful design. This is especially true where the SMPS and the amplifier work together to improve performance even more as a pair. I know how difficult it is to design reliable SMPS and class D amps, I've done it a few times and it took longer and cost more than I expected every time. Ultimately, even though I have the background and education to do so, I simply couldn't compete with the depth of highly specialized talent that IcePower has in-house. The smart decision (IMO) was to partner with the best designers in the world and exploit their strengths as well as have input into their evolution of new products. Sometimes it better to put ego aside and keep your strengths for where they can make the greatest contributions.

You made the claim that class A amps are always better than class B amps, yet in the bass amp world (this is a bass forum after all) class A amps of any practical power level simply do not exist. therefore a product that does not exist can't be better. That's why I wondered if you understood the nature of conduction angle as it applies to class A, versus AB, versus B, versus C.

Yes, you are essentially correct. I know of no practical examples of class A bass amps available.

This is a good question, and I believe it has been discussed before (maybe not here but on other forums). One way to determine rated RMS power is to go to the AC power rating, which by safety agency standards must be a MINIMUM of what the amp draws from the source at rated audio power at the lowest rated impedance USING RMS metrics at a minimum of 1/8 rated power. According to the published specs below, we can determine the likely power in RMS terms: The calculation would be to assume an overall average efficiency of 85% for the power supply and amplifier, and run the following numbers using the published 110 watts input power: (110W x .85%) /.125 = 748 watts RMS rated audio power as used in the safety certification. If the overall average efficiency was 80%, then the calculated value would be 704 watts RMS (both into 4 ohms). Under maximum power output, it's listed as 2000 watts peak, but without a concrete definition of peak being provided, no conclusions can be accurately drawn. Peak will always be less than when using RMS metrics however, usually twice the RMS value but sometimes more depending on the definition. I hope this helps answer and clarify your question.

Interesting perspective. Would you care to give and example of a class A bass amp (power amp) that fits your above theory? From your description it sounds like you are unclear about what amp class actually means. All class D amps have power supplies, and what may be surprising to you is that some of the power supplies used in class D amps are actually bigger (in capacity) than their line frequency brethren. Sometimes by a LOT. The physical size can't be used as a comparison because the SMPS that are most often used with class D amps operate at a higher frequency which requires smaller magnetics (transformer) and also recharge the supply bus at ~100,000 times per second rather than at 120 times per second (100 times per second in 50hz regions)

Actually, the bigger problem is the end users who think they understand what the data sheets mean without actually understanding the technical data behind the numbers and WHY they might be used in describing specific specs. When an experienced designer learns all of the ins and outs behind the performance of the module and what is actually happening between the lines, it becomes apparent that there are additional performance gains present to those who understand how to exploit them. As a specific example, when I was designing around an earlier IcePower module, we used to get "armchair techies" who would insist that the module wasn't capable of driving 4 ohms BTL and that it was was only capable of 250 watts into 4 ohms therefore we were not being truthful. In fact, the amp could easily deliver 900+ watts RMS into 4 ohms BTL, and that the 250 watt single ended specification didn't even apply. This was such a valuable off sheet applications (that required specialized cooling and over-modulation management) that we received a patent for the techniques that we employed. It's very similar to what's happened in the automotive industry over the years. Power output per cubic inch (or litre) of displacement has increased greatly through the introduction of fuel injection, variable valve timing, variable ignition timing, stoichiometric fuel management through combustion products feedback, advanced combustion chamber design, tighter tolerances, lighter reciprocating mass, etc. The same applies to many of the successful applications in all industries. The more you know, the easier it is to be successful and deliver successful, reliable products.

I'm going to disagree here as I have experience designing amps around different platforms. In general, all of the MAJOR power amplifier platforms are really quite good and difficult to discern any real world differences when driven from an identical source. Most of the differences come from the designer's choices that typically reflect what the players are asking for as well as their own personal tastes) The reason I (as a designer) have chosen IcePower is because of my 20 year history with the product back when I was designing touring level pro audio using the IcePower platform. In the industry, they are generally considered the "gold standard" module because of their reliability track record, their ability to supply defect free product without interruption, their product's safety and EMC certification, and the in-house engineering support capabilities. You might be surprised, but cost is actually pretty far down the list of priorities as they are not the cheapest supplier of these parts (not by a long shot).

A solid state amp does not have to distort with odd order harmonics IF the designer chooses to manage HOW the amplifier clips. A tube amp, for example will NATURALLY distort with more lower level, even harmonics but this doesn't mean that a solid state amp (either linear class AB or non-linear class D) can not. In fact, one of the most important aspects of today's current digital based modelers (ie. AxeFx, helix, etc) is all about improving and perfecting what happens (in software) under modeled clipping conditions. Similar things are done by some designers in the purely analog world as well. Often, the power supplies in class D integrated power amp modules with SMPS have GREATER capacity than their linear (class AB with ,line frequency power supplies) counterparts. Often by a great margin too. Just providing some factual information here.

This is true, there are good implementations of amplifiers using these parts and some that have suffered from the symptoms being described. Each designer is different, each has their own preferences, skill set and experience designing with these parts. My design experience with IcePower goes back almost 20 years, when I was also designing for the (touring) pro audio industry. When I started designing bass amps with these class D parts, I already had a 5 year advantage over just about every other designer so I wasn't affected by the learning curve nearly as much. Also, this was the same time that players began demanding smaller, lighter weight cabinets, so some of the differences can be attributed to a general migration of demand and change in tastes rather than just the amps themselves.

It's not just the size of the heatsink, but the effectiveness of transferring heat to the ambient environment. A good deal of thermal engineering goes into high quality designs, it's not the kind of solution you pull out of your butt (or bum) because that's how you end up with thermal problems and noisy fan designs.

I wouldn't recommend 600 watts RMS continuous through a Kappa 15LFA, not if you want a long service life. The "maximum rated power" for most manufacturers (including Eminence) is based on a 2 hour survival rate. My experience through testing of many drivers for calculating warranty exposure purposes suggests that a ~20% reduction minimum is necessary in order to increase this value to 200 hours. I typically use 25% unless testing shows otherwise. Powering with 400-450 Watts (rms) is about ideal for that driver IME.

Where the return currents travel through the aluminum structure, there are voltage gradients all over the plane and no uniform ground reference. These voltage gradients factor into amplifier design too, we want to eliminate as many paths of current (both conducted and induced) in the amp's chassis through the use of star ground networks. The same applies to PCB layouts, every trace is a resistor and as the frequencies increase (SMPS and class D) every trace is also an inductor and capacitor.

It is indeed the designer's choice. It's not just the fan, but the aerodynamics of the air flow, the ratio of laminar flow to turbulent flow, and how the heat is removed from the devices and into the atmosphere. Using the same power module and even the same fan, it's possible to have very different noise levels depending on the choice of the designer and the designer's experience in the area of thermodynamics. I actually am the "inventor of record" on a US patent for the management of thermal loads and peak current management in class D amplifiers, so this is obviously not something that I take as casually as others might. There are many ways to skin this cat, some are quite elegant and some quite messy.

There are many similar styles of jack but beware that there are different mounting heights and pin setbacks from the front edge of the PCB. Sometimes, the best solution is to get 2 identical jacks and replace both, at least that way the mounting height doesn't matter and as long as the mounting surface of jack extends slightly beyond the PCb everything should mount fine. Just don't damage the PCB.

For 400Hz power supplies, noise can enter through the power supply, through the inductive effects of then magnetic field of the transformer or from the effects due to ground loops. Sometimes, bridging topologies can be beneficial because IF you can get the noise to be common mode, much of that can be rejected because the noise falls in a band where the CMMR of most op-amps (including power op-amps) is the highest. The parent company of Genz Benz (one of the companies I designed for) was part of Kaman Aerospace (K-Max high lift helicopters and other aerospace subassemblies) so there were a lot of exposure to resources that revolved around electrical noise control in 400Hz environments.

The fan on the Subway amps (and other amps that I have designed in the past) are quiet by design. It's not something that can really be retrofitted AND still have acceptable performance under hot ambient conditions, As an example, it's not uncommon to reach 100 degrees F in my area so I typically design to somewhere around 105 degrees F as the high ambient temperature condition. At these temperatures, I doubt anybody would want to either play bass or listen to bass or a band or much of anything IME.

For small amps it's almost impossible to beat the performance of the TDA-2050 without spending a LOT more, but it looks like these are all going by the wayside in favor of integrated class D IC based amps. Look ma, no heatsink! There were a lot of cool tricks that could be done with the TDA series too, even paralleling a couple or 3 to drive a 2 ohm load! Paralleling took a good bit of effort to insure stability, and there was also the bridged parallel set-up that could get might impressive power into a 4 ohm load (close to 100 watts IIRC). All of that's now water under the bridge.