agedhorse

This is a critical bit of information IMO.

Perhaps I can help you understand why some designers choose to use a fan? Neither of the amps you listed are rated for 2 ohm operation, and neither are rated for as much power (RMS) either. When considering cooling strategies, my general goals (and others with similar philosophy) might choose to insure that their products are capable of operating at a higher duty cycle into a lower minimum impedance at higher ambient temperatures (I typically use 105 deg F) than other designers might choose to use. Also, the warranty offered often factor into the decision. The companies I have designed for over the years have offered longer than average, which predisposes me to a more conservative approach. I do work hard to minimize fan noise, but a small amount will always be present. If a fan bothers you enough, simply choose an amp without a fan and accept those compromises compared with the compromises of using a fan (noise)

Assuming that no new damage is created. That's another topic, but I see folks try to do this kind of repair and damage otherwise perfectly good PCBs because they don't have the proper tools or experience to work on double sided PCBs (the norm now).

Generally, IF THE POT HAS NOT BEEN CLEANED WITH "MIRACLE CURE-ALL" CLEANER, dust is not a problem with the rotary pots. What can be a problem is microscopic insulating layers of oxides and sulfides that are angstroms thick, just thick enough to inhibit reliable contact with the fingers of the pot's wiper element. DeOxit D-5 in particular is quite effective on this without damaging the conductive element (especially at the terminal rivets), but liberally applied will wash the lubricants from around the bushing onto the conductive track which will attract abrasive debris and grind the track and fingers into oblivion. Other substances can do this as well, but also damage the conductive surface, making it MUCH more vulnerable to wear. Some techs refer to such substances as "disaster in a can", because when they work on amps that have been serviced this way, they often can become disasters. A full set of pots on some amps can push the cost of repair beyond the realistic market value of the amp.

If it's the can that comes with the small removable tube that sticks directly into the nozzle it's not to bad, but the new style with the swivel is a real pain and you have to have just the right touch. Also, NEVER spray down the shaft (no matter what you might have seen on the internet). That's a quick way to ruin a complete set of pots as it washes the bushing lube everywhere it doesn't belong. I see units with spray residue all over the PCBs, and this attracts little conductive bits that then provide leakage paths. This is especially true on circuits with very high voltages and also very high impedances. Once this happens, the PCB must be removed and washed in an approved solvent to remove the oily residues. Then the usual production wash in a saponifier with a DI or distilled water rinse and mild temperature (like 120-130 deg F) bake dry. Pots and switches (and anything that can't be washed in production after wave soldering) must be protected. Different parts have different requirements, which is why I try to avoid this and when it happens it's costly to remedy because it takes a lot of time to do right. In my shop where I still service Genz Benz products, I know what parts are safe to wash and what aren't, but even then it adds between 30 minutes and an hour to a repair. It's one reason why I discourage DIY repairs, they are MUCH harder to correct and repair right. The other reason is that we have to examine the amp closely for any additional, hidden repairs that may jeopardize reliability in the future. Everything that goes through our shop carries a 90 day service warranty and I don't want to see any repairs back because I missed something. Generally I can keep it to one or less service re-work per year because of this policy. Hope this helps.

Yes, often "not cheap" goes along with very good. A little bit goes a very long way.

Use the TINIEST amount of cleaner, less is more in this case. In the US, DeOxit D-5 is the only substance that I have tested extensively with no long term (over 20 years) issues. I do see a lot of pots for units in for service that were cleaned with a variety of "miracle cure-all sprays" that have subsequently become ruined (either from the product, or from over-application which washes incompatible lubricants into places that causes additional damage). I do not know if there are equivalent products across the pond, but based on what I have seen acceptable products are few and far between.

When using the FET channel, there should be a delay of about 3 - 4 seconds.

I can pretty much guarantee that it has nothing whatsoever to do with capacitors (regardless of all the bad advice on the internet). In 12 years, I have never seen a bad cap on a ShuttleMax and I handle all the factory service/support for North America. By any chance do you have the amp set for the tube channel only, and you are waiting for the tube to warm up? That's about the right time for this to happen.

For those wondering why all manufacturers are experiencing delays, here are a couple of good shipping industry articles that outline the specific issues being encountered, and why: https://www.hellenicshippingnews.com/will-container-shipping-reliability-come-back/ https://theloadstar.com/blanked-sailings-and-covid-19-bounce-back-bring-new-congestion-at-ports/ What we are seeing more shipments (both inbound to us outbound to Europe) being delayed for a variety of reasons, but primarily from canceled sailings where the shipping line simply eliminates a ship's trip and consolidates those containers on a later shipment. Since ships do not leave every day, and in fact they can leave every other week between some ports, resulting in accumulated delays if two trips get canceled back to back. This makes predicting anything related to delivery more and more difficult (and frustrating to everybody concerned, including us).

Here's another review of the TT-800, comes from a player perspective: https://bassmusicianmagazine.com/2020/10/review-mesa-boogie-subway-tt-800-bass-amplifier/

Steve - I'm sorry. I shouldn't have said "your" amp because there's no way for me to know which particular amp you might end up with. I should have said "amps destined for Europe". My appologies.

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.