agedhorse

In general, where the OUTPUT impedance of the SOURCE is less than 1/10th the INPUT impedance of the LOAD, the effects of loading can be ignored. If this is not true, it's possible for issues to occur. This is independent of level, a different parameter entirely. [edit for garbled response, clearly reversed]

Are you aware that SWR as a company has been shut down for almost 7 years and that there is no support available (including parts)?

Running an iPod into the instrument input of an amp shouldn't damage it. I do it all the time as a test signal source.

The ASX-2 models are long in the tooth, but they are actually still quite a ways better or more appropriate (all things considered) that much of the competition. That's why they are still being used in a variety of current products. With regard to rated power, there are different applications that exploit different aspects from all of these modules. That's one of the confusing things, where somebody looks at a data sheet or a marketing sheet and comes to a conclusion that simply does not apply for a particular application. I ran into this head-on when I designed an application around the 250ASX2 module that allowed the amp to operate BTL into 4 ohms even though the specifications stated 8 ohm minimum load in BTL mode. Initially, it was claimed that I was a fake, and that it was impossible, couldn't be done, would blow up, and couldn't deliver 900 watts RMS into such a load. This was from other amp manufacturers, as well as end users who hadn't even the slightest clue about amplifier engineering but were high and vocal on the bully pulpit. In the end, with ICEPower's support and approval, we received a patent for our approach and delivered many thousands of highly reliable amps based on this "impossible" platform. We were the first to use this part like this, and obviously others followed what we did with their own interpretations (some successful and some not). Some of the concepts behind the newer AS1 platform came out of the research and data that resulted from our off-sheet application of the ASX2 parts. I can't go into anymore on this. The short story is that there is more going on in many of these products than the average or even technically inclined person might ever imagine.

ICEPower only sells OEM, that represents 99.9% of their business. That’s likely why it’s not worth the effort or the cost on an older product. Those who buy a product like this on eBay from China, outside of the authorized distribution network, are getting what they pay for in the sense that eBay is well known as a marketplace for counterfeit goods. Profusion is an authorized distributor for some ICEPower models, but yes they are more expensive.

It’s class AB.

The genuine parts are more expensive to build, the test process is very comprehensive, the factory’s are more expensive to operate because they are under NRTL (nationally recognized test lab) inspections, and the products include international safety and EMC compliance which is also costly to maintain. All OEM’s who currently use this part are aware of the situation now, but the damage is done. Most quality OEMs buy directly from ICEPower so there is no issue with us receiving counterfeit parts as the tracking is quite thorough and serial numbered.

It is unfortunate. As a long time (as in almost the beginning of IcePower when they were financed and partially owned by B&O) designer of products using IcePower parts, I have access to much more information than most do. The backstory is complicated and confidential, but it was basically outright theft of their IP. Unfortunately it's hard (read as virtually impossible) to enforce anything in China, and there were some amp manufacturers that used of IcePower product that were tempted by the lower price of the counterfeits (most didn't realize they were counterfeits as they were marketed as surplus from a large Chinese contract manufacturer who got stick with thousands of these parts) only to learn that they were counterfeits and the reliability was nowhere near the same. Counterfeiting is a very real problem. I got burned once (about 20 years ago) when I ordered a National Semiconductor part from a reputable authorized National Semiconductor distributor. The parts didn't work the same, but they looked identical in every way. Sent them to the manufacturer for x-ray analysis and it turned out to be a different die inside the package with different characteristics. It turned out that a customer ordered many thousands of these parts and then returned counterfeit parts in counterfeit sealed packaging to the distributor (common practice) several thousand of the parts for credit. They were an expensive enough part that it was worth the hassle apparently.

Virtually all ICEPower 125ASX modules available on ebay that are shipped out of China and Hong Kong are counterfeit.

True until you have an accident, or a momentary lapse of good judgement.

Impedance looks good I will be able to sleep well tonight!

The "gain factor" of a tube does not necessarily translate into circuit gain. It depends very much on the circuit itself. There are circuits where a tube with "higher gain" will result in a circuit performing with LOWER gain. It really does depend on the circuit the tube is used in. Forgive my use of the word tube in place of valve...

Hopefully, being asked to turn down and your divorce don't have anything in common...

From my experience designing amps, this is generally the most accurate description of what's really going on. And to add... conformation bias is very much a real thing that can be a frustrating source of "non-difference".

In pro audio, mutes can be used for a variety of applications, not just to kill a channel. For example, most pro audio consoles have mute groups, where a number of channels assigned to a mute group can be muted with a single switch. The most common application for this is on effects returns for killing the returns between songs for talking. They can also be used for groups of instruments, where say there's an acoustic set and an electric set (or songs) and to switch between them the unique instruments would be assigned to mute groups so say the acoustic guitars and say mandolin could be muted during the electric set. Why not use subgroups for this? You can if you are not mixing monitors from the FOH console, because the pre effects sends (monitor mixes usually) would not be muted so the benefit is not there. Of course this has all been made a little less relevant with multi-input digital consoles, VCA/DCA's and input to channel patch duplication (main and post eq/fx monitor mixes from the same channel).

It's typical for the bass market to lead the guitar market in useful features and technology, guitarists often have a mute feature in their tuners (when they choose to use them).

See my post above, just because something "works" doesn't mean that it's correct and not causing a problem (or a problem that will rear it's head down the road). For those who claim that all failures in an amp under warranty is because the amp is defective, this is a good example of why this statement is not always true.

This is why amp designers spend so much time and effort designing protection circuitry, but even so, protection circuits are not perfect and failures can occur.

Different players, different needs and different tastes for their "at home" application.

The send impedance isn't going to matter much, it's the return impedance that dictates the effectiveness (based on orders of magnitude and the position of the elements in the circuit.) It's a good exercise to do the math, then it becomes obvious WHY. Return input impedances run anywhere between 10k and 100k, there will be a lot of effect at 10k and almost none at 100k.

A 56k resistor is series will work ok with some amps and not with other amps depending on the topology of the loop. I was just pointing g out a more correct solution for those who care about such things.

Neither, those topologies are used for impedance matched networks. All you need is a simple voltage divider.

Using a resistor like that depends entirely on the input and output impedance of the effects circuit. Generally, a more predictable result comes from a true series/shunt pad where the variables are defined almost entirely by the external circuitry rather than varying based on what is inside the amp.

If there are no bleeders designed into the circuit, or if there is a failure with the bleeder circuit, caps can store charge for a surprisingly long time if there's no load (like a typical plate circuit).

This is something that sound guys deal with daily.