agedhorse

I very rarely find defective electrolytic caps, my experience is that caps made in the last 40 years are likely to last 50 years or more provided the designer respected the design requirements of the part. In amps that I designed on the past, going back over 30 years, I have yet to see a bad electrolytic cap (other than one that was damaged by a repair attempt). When sample caps are tested, they are fully within acceptable spec. I have seen plenty of PCB’s damaged by techs or adventurous users doing cap jobs (without the proper knowledge, skills, experience and tools) and creating expensive paperweights out of their formerly perfectly fine amps. I generally recommend leaving well enough alone, it it isn’t broken, don’t break it!

It doesn't even need to be synchronized for the benefit of increased power efficiency (though it may be necessary for other reasons such as EMC control, THD reduction or purely functionality depending on how the topology is achieved.) The PWM frequency is high enough that it all averages out with the lower audio frequency and the reactive power reclamation still works.

Generally, no. The output stage is configured as either 1/2-bridge or full bridge depending on the power supply and the design of the power amp.

This particular mechanism doesn’t apply to class AB/G/H amps, so the increase in efficiency doesn’t apply for these types.

Bridging (internally) on class D amps is done for very different reasons. It allows reactive energy stored in the electro magnetic field of the voice coil moving within the motor to be transferred to the the opposing rail(s) of the power supply rather than to be dissipated as heat. This improved efficiency.

It may not be a bridged output either, which helps by eliminating some particular failure modes.

And now, many amps use bridged configurations (often internally).

Both plugs and jacks are internally specified for ~5000 mating cycles, OEMs would's use them if it was only 1000 (even if the retail paperwork says so) Retail facing paperwork and specifications aren't what OEM's use, and we have access to better data than that.

OEM specs are 5000 mating cycles

A properly built jack (like Neutrik brand) uses phosphor-bronze or Cu-SN6 alloy bronze components that are very spring-like and extremely reliable (rated for 10k mating cycles minimum). Of course there are lesser quality parts with issues, but that's not a design problem. Lesser quality parts may be good for 1k mating cycles or less.

Beware that the insulation on this unjacketed on that type of cable is very vulnerable to damage, both from stage hazards as well as where the top of the strain relief chuck meets the wire. The strain reliefs on these plugs are designed specifically for round jacketed wire to avoid pinching and stress points. This won't hold up for very long in pro applications, whereas proper cable can hold up for a couple of decades.

That's really odd, I've never seen a single PA application wired with 1- wired to 2+ at the load end EVER. In any application where 2+/2- might be present at the source (like in a stereo application w/ left and right carried on pair a and 2), this creates a dangerous load to the amp. On PA applications, the industry that I know follows the Biamp wiring, with 1+/1- being the low pair or full range if not biamped. 2+/- is only wired when used for HF in biamped applications, otherwise is entirely not used. It looks like it was a hack to allow for a series connection, but I've never seen it used in any pro speaker cabinet. The reason is to avoid damaging conflicts when a biamped cabinet might be used just for low frequency applications, or where 4 wire cables are used for all applications. My sound company's inventory includes about a hundred 4 wire SpeakOn cables that get used for everything, so we don't have to worry about what's 2 wire and what's 4 wire. Every sound company I have ever worked with does the same thing. I'm talking about pro companies, not a guy, some speakers and a sketchy van. Here's JBL's application of the SpeakOn standard wiring: https://jblpro.com/zh/site_elements/srx700-users-guide

2 pole panel mount Neutrik jacks are now identified as "2 pole keyed"

Reminder, when using any kind of contact spray (on switching contacts), it hast to actually get in the contact as well a not get elsewhere which can cause new and more expensive issues. never use contact cleaner on pots, it’s a good way to ruin them. DeOxit D5, and only the tiniest amount in the slot that the terminals exit from is generally safe and effective.

Most likely.

Most have 4 pin SpeakOn jacks, wired with only 1+ and 1-.

Correct, Rean jacks are essentially identical to the parent company branded jacks and in fact share the same safety certification file. Rean parts are available to large OEMs with some customization options.

RoHS was in effect when SWR was shipping those combos, most of us in the industry began to migrate well before 2006 to get ahead of that curve.

I've seen it before, specially with rough DIY repair handling. If lucky, it can be pushed back onto the rivet with a little 2 part epoxy to keep it there. I would compensate him for the damage rather than spending at least that much for the cost of the return shipping plus eating the initial shipping charges too. It's the least of the evils IME, and you will come out way ahead.

You better be sure that whatever solution you choose actually achieves the necessary cooling. I see a fair number of DIY solutions that fall far short of this goal, sometimes with costly consequences.

That would be a nominal 4 ohm driver not an 8 ohm driver, by any definition of nominal impedance. 8 ohm nominal would average greate r then 8 ohm’s impedance, with less than 20% of the bandwidth dropping below 8 ohms and dropping no more than 20% below 8 ohms when measured in the cabinet. The cabinet affects the impedance below about 250Hz. This is a good rule of thumb IME as an amp and speaker designer. There are 2 different mechanisms that need to be respected for an amp to work reliably, maximum peak current and power dissipation. Average and minimum impedance affects both mechanisms.

I know we sent a bunch of bass amps to Europe, it’s possible that some retailers are still filling backorders. I don’t have access to any of that.

This American bashing stuff gets really old, and it's ironic in this case because the SpeakOn was a European design that was horribly flawed when first introduced. Everybody seems to forget the ridiculously unreliable locking ring that was changed in short order to various versions of the thumb latch... and the lack of the metal insert was part of the original Neutrik design for at least 5 years! Since Alec posted a rant thread on TalkBass which I answered, in the spirit of accuracy and honesty I provided the following information to set the record straight for those who think they know more about this subject than they actually do. ---------------------------------------- The original Neutrik part did NOT have the metal insert, they didn't start using metal inserts until a little later. Our replacement part was developed at a time when Neutrik was so backed up that they couldn't ship the NL4MP part for over 1 year when they were struggling with regulatory compliance for flame spread and their original jack series was non-compliant to the necessary safety standard under the 60065 edition 8 fire enclosure regulations (which specifically applies to amps, but using 2 different parts for amps and speakers (if we could even get the old part) made no sense. This was actually a licensed Neutrik part manufactured Neutrik's Rean division using a different glass filled Nylon (PA-66) compound that had lower flame spread. Ironically, they had to do another update to comply with the flame spread requirements for IEC 62368, where the punched opening in the sheet metal was close enough to a PIS that the part needed a lower flame spread rating, it's due to the (much) more compact nature of the newer amps. Below is the original Neutrik branded part that we used at that time, it suffered from exactly the same wear issues as well, every pro audio manufacturer of that time dealt with the same thing. You have to remember that your speaker is between 15 and 20 years old, technology and regulations change through over time. If you had really understood what you were talking about, you might have chosen your words more correctly and diplomatically. Also, you may not know this either, but the Genz Benz factory service program is still "a thing". Factory support for the products exists throughout the US, Canada, and much of Europe, Australia, New Zealand and Japan. --- Follow-up: The glass filled PA-66 material that's used on the jacks is about the same wear as the original material, but the flame spread rating is higher on the updated part in order to comply with the newer safety standard. The metal insert was introduced by Neutrik and Rean at the same time because of wear issues, it's unrelated to perceived "quality" differences. Perhaps you are unaware, but Rean is owned by Neutrik AG and handles much of the OEM development of connectors as well as the manufacturing of Neutrik, Rean and OEM branded components and connectors for products and assemblies built in Asia and some markets in North & South America. OEM's often use customized versions of connectors for the purposes of regulatory compliance, cosmetics (color, logo, cosmetics), and in some cases to achieve things that can't be done with stock off the shelf components (like for example bonding modifications for pin 1 terminal on XLR jacks) in high volume applications. The models with R in front are marketed through the Rean channels but are identical in performance and share the same ETL safety listing certificate because they are in fact the same company:

The half-rack concept never caught on by itself, therefore most manufacturers that originally signed onto the concept dropped it (except for side by side applications into a standard 19” rack. There are 2 official EIA rack standards, 19” and 24”. 19” is what we use in the MI and pro audio industry.

Not necessarily, if your cabinet is high sensitivity and you have reasonable expectations.