agedhorse

13 hours ago, stewblack said:

This is my experience. I said that. I can only share my experience everything else is heresay.

I would add that your experience is quite unlucky compared with industry statistics.

11 hours ago, Chienmortbb said:

One of the reasons I would avoid 2 ohm operation. Its too close to a short for my liking. I also agree about protection, its  like contraception. Not 100% effective. My dad got an apology from the condom manufacturer when I was born

There is no problem designing for 2 ohm operation with identical reliability to an amp with 4 ohm minimum load operation. In amps I have designed, the reliability statistics fully support this.

1 hour ago, Chienmortbb said:

No you are right, at least over voltage and over current protection. Some have under voltage protection too. over current will protect against shorts or sub optimal loads. One of the problems with some speakers is that they go under their quoted impedance at certain frequencies, so over current protection is vital.

There are many different protection schemes depending on the type and class of amp. These protection schemes include:

- AC line over-voltage protection

- AC line under-voltage protection

- power amp thermal protection

- power supply thermal protection

-output stage over-current protection

- output stage leading phase angle protection (illegal capacitve load)

- DC offset protection

- power supply over-current protection

- excessive HF content protection

- short cycle inrush current protection

Some amps have many of these protections, some have just a few. There is substantial cost (and design effort) to these but when you can reduce the failure rates to almost zero by including them, in general it's a good choice.

2 hours ago, Downunderwonder said:

I think most of the value would kick in as saved staff time pissing around on invalid warranty claims caused by user error. That would filter back to a slightly keener price.

Unfortunately, there’s little marketing value, but it does save massive costs to both the manufacturer and the player.

14 hours ago, stevie said:

How does protection work on an amp like this? I've always assumed that they all have some kind of protection against sub-optimal loads or short circuits. Am I wrong?

Most do have protection circuits, but it's important to recognize that protection circuits are not 100% effective against all faults and all fault conditions. Different designers and different companies place different amounts of importance on protection circuits since they add to the cost of the design while being almost impossible to market as a valuable feature to the majority of customers.

On 19/07/2022 at 13:53, stewblack said:

Everything is relative of course, however the Markbass is not a cheap brand. The cheap stuff I own has run and run without a problem. All the expensive stuff on the other hand is either economically unfeasible to repair or costs an absolute fortune just to service.

 

This may be your own personal experience with limited brands or models, but my experience is that this is not true in general.

4 hours ago, Stub Mandrel said:

Perhaps the most difficult issue is matching speakers and cabs when it is so hard to understand real world output figures.

 

For example, my main cab is rated '900W RMS (AES Standard)’. Not simple to grasp, and I don't know how it compares to real world figures for bass rather than "mixed programme".

 

Is there an aes standard for amplifiers?

Yes, but there are also other just as valid (and maybe more-so) depending on how powerful the amp might be. What's appropriate for a 100 watts amp that's going to be driven into compression and clipping might not be appropriate for a 2500 watt amp that has the capacity to destroy most speakers if driven into clipping or compression. It depends. 

A designer has to come up with a method that makes their intended customer happy with the results, doesn't result in premature shut-down or self-destruction and delivers adequate performanece.

When an amp is not designed to be repaired at the component level, you generally get the benefit of a more inexpensive purchase price but then suffer the consequences of needing to replace assemblies rather than component level repair. This is not a big deal where the designs have a history of long, reliable life, but can be very costly (for both the manufacturer and end user) if the failure rate is high and the failures affect amps less than say 10-15 years. 

At this point, doing the "true cost of ownership" calculations shows that the cheaper amp built this way may in fact be more expensive than the more expensive amp that has a longer, more trouble-free life. 

As a society, we have become more accepting of "disposable" consumer goods, and there are companies within our industry that specialize in this model. Ultimately, when these products are manufactured "off shore", not only is there the loss due to the cost of a product that is considered disposable, but there is also the loss of income to those within your region who would have built the product "in region" or "in country" that affect the local health of the economy.  This is something that we began studying in engineering economics back when I was in university (a very long time ago, I assure you), I assume that it has taken on added importance in recent years.

If the amp's specs have been revised to operate at a minimum 4 ohm load and you had problems that may have been contributed to be being operated into a 2.67 ohm load, you might have another path to get this resolved in your favor. You should not be responsible for somebody else's mistakes, heck it's tough enough being responsible for our own, right?

1 hour ago, chyc said:

For me one obvious tell, at least in the PA market, is where I can see active PAs with some colossal claim as to what its power rating is, and yet when the same company sells passive units the number is a tiny fraction of it (because they're worried you might *actually* attach it to a powerful amp). While it's possible, it's seriously stretching my disbelief that there isn't some marketing BS going on.

 

By no means are they the only ones, but QSC sell the 2000W K12.2 active top, but their E112 is rated for 400W continuous power. Yes yes they're not the same thing, but to me to be different by a factor of 5 is massaging measurements to the point of dishonesty

There are a couple of things going on here that the marketing departments jumped on like rabid dogs...

First, there is the obvious limitation of the high frequency driver which is no more than about 35-40 watts RMS above 800hz. There is dynamic mechanical power handling above this, but in practice, due to the sensitivity difference between the HF and LF sections, this doesn't even come into play. Typically the HF section is at least 10dB more sensitive than the LF section on a cabinet like this. So, even if the amp is nominally capable of delivering "1000 watts" (or whatever number), the internal processing limits this back to no more than 100 watts for "survive-ability" reasons.

Second, looking at the LF section, the driver is not going to be capable of more than 400 watts RMS at low frequencies, therefore in the processing, the limiting and HPF algorithms are often dynamic and increase the amount of limiting as level gets higher and frequency gets lower. This too improves "survive-ability". 

Since this is a biamped speaker, the easiest and most common solution is to use the same power amp design for both channels, and use the driver's impedance plus processing to manage the real world power levels delivered to the speaker. For example, the amp might be rated at 1000 watts RMS at 4 ohms, but if the drivers are 8 ohms (or even 16 ohms in the case of  the HF driver), the unprocessed power available would be 500 watts RMS to the LF and 250 - 500 watts to the HF. 

There's nothing wrong (and a LOT right) with managing power this way but IMO the real issue is with the way the numbers are manipulated by the marketing folks in a way that appears deceptive even if that's not the intent. Incidentally, this is a major conflict at many companies, between the design/engineering departments and marketing departments.

It's not quite so easy, though there are rules of thumb that engineers can use to determine the validity of specifications (called cross-checking or cross-verification).

The AC input power is required for any amp to be the current draw at 1/8-rated RMS audio power at the lowest rated nominal impedance for any amplifiers compliant with IEC 60065 or 62368 safety standards. The standards also include a provision that if an amplifier is intended to and marketed to drive more than 1/8-duty cycle, the stated AC input draw MAY be increased to account for the increased (more severe) duty cycle.

That said, the rated AC input power is verified by the test lab and really can't be fudged. RMS rated power can be calculated from the input power using the following method. 

Using an assumed efficiency of 80% for a class D/SMPS, the 110W is multiplied by the efficiency then the result is divided by the duty cycle for rated RMS audio power.

Using the 110W input example:  (110W x .80eff)/.125dutycycle = 704 watts RMS (presumably 4 ohms)

With the Orange Terror, to me it looks like they are using a more severe duty cycle because roughly (500 watts input x .8 eff)/.125 = 3200 watts. In fact, what it looks like is that the rated input is actually the maximum rated input rather than the average rated input. This would conform to a duty cycle  of 1

On the Subway amps, I typically use a duty cycle of between 1/4 and 1/3, therefore the rated AC input is higher than what it would be if we used 1/8-duty cycle (IIRC, I use ~400 watts rated AC input for an 800 watt RMS rated amp). This is because the amps are advertised and marketed to be able to be overdriven, and these numbers would then be accurate. 

Maybe they discovered an error and revised the docs and chassis? Happens sometimes in spite of best efforts.

The 900 watt models are 2 ohm capable and use a switch to operate at 2 ohms.

Not according to the docs on the Darkglass website:

https://www.darkglass.com/app/uploads/2022/05/AO500-Manual.pdf

Maybe you are looking at the wrong model, or there is an error in your documentation? 

3 ohms minimum, which is 4 ohms nominal with room for excursions into sub-nominal territory.  I am very familiar with the module they use and the following is accurate.

4 minutes ago, lewiswhitebass said:

No it auto selects it on the head.

According to the docs, it’s 4 ohms minimum load. I wonder if this is the root cause?

3 hours ago, lewiswhitebass said:

It may well have been. As the head can handle anything down to 2ohm it shouldn't matter to much

Is there a switch that needs to select 2 ohm operation?

As a reminder, this is similar enough symptoms of an intermittent SpeakOn plug.

I have seen intermittent plugs for two main reasons:

1. Counterfeit or knock-off, non-Neutrik branded plugs (major issue, and a cause of a fair amount of warrant claims unrelated to the amp)

2. Improperly assembled SpeakOn plugs where the assembler trimmed the wire, which then cold flowed under the pressure of the binding screw and loosened.

Both of these are well known issues that I deal with way too often in customer support.

Any amp designed to IEC-60965 or 62368 in the EU must operate (and is tested by a nationally recognized test lab) at 230V +/-10%. That would be 253V high line and 207V low line.

If the amp needs certification to operate in regions with nominal 240V, this would include Australia and New Zealand), the national differences approvals would add a 264V high line test.

Virtually everything of any quality these days is designed to operate at a high line of 264V because it makes no sense to design multiple versions (at least with SMPS) because it would add more cost to the certification process than could be justified. 
 

The homogenization limits tolerances really do work quite well in practice, and in fact utilities have adjusted their generating and distribution voltages a few percent to improve compliance as well.

Australia has some additional challenges, primarily around voltage regulation on long transmission and distribution lines with varying loads in the Outback.

1 hour ago, Jakester said:

Of course, it happened outside their ‘warranty’ period as it hadn’t been used much due to lockdowns etc. 

That’s unfortunate. 

13 hours ago, Jakester said:

As to the issue, Real Electronics in Sheffield are the Mark Bass appointed repair agents. However, they don’t do component level repairs - if there is a fault they’ll swap out the board, which makes it expensive if out of warranty. 
 

I had a fairly unsatisfactorily experience with them - I had a intermittent fault with my CMD121P, sent it to them, they said there was nothing wrong, replaced all the pots, charged me £125, and then the fault came right back again. 
 

I ended up buying a second hand Little Mark 3 and replacing the head with that. 

Most repairs include a warranty on the repair. Did you follow up with them on this? 

1 hour ago, Chienmortbb said:

It's OK now, Boris has gone (nearly) so we might rejoin next week 😁

I posted before hearing the news... 

47 minutes ago, Chienmortbb said:

Very few in the UK.

If not in the UK, Italy isn't THAT far from the UK (though admittedly farther appearing since BREXIT)

Contact MarkBass and see what service options they have for you. 

15 hours ago, prowla said:

I don't recall you trying to warn me?

eg. in this thread

The following post is from TalkBass, ahead of you post about looking at a cheap 1300W x 4 channel Chinese amp. Yes, the information was provided and discussed by other members in detail.

Some manufacturers understand the value that premium platforms like ICEPower bring to their customers. They also tend to follow safety and EMC rules, and avoid no-name amp solutions because they know the pitfalls in performance and reliability.

Some manufacturers also understand how to exploit unpublished attributes of the ICEPower platforms to go farther than the published specs might (inaccurately) indicate.

13 hours ago, Chienmortbb said:

As some of you know I have used and evaluated many class D modules over the years and some of them included mains Switch Mode Power Supplies. One in particular, from a long established Chinese company would work intermittently but most of the time it would go into the protect mode.  I had contacted some buyers of this amp in Europe to check that they were happy and to get their opinions on the amp. In all cases they gave a glowing report.

 

I contacted the company and re-read the specs and noticed that the upper limit for main voltage was 240V. As @agedhorsementioned a few posts earlier, we used to have a nominal mains voltage of 240V before joining the EU but sensibly WE persuaded the EU that mains voltages should be harmonised. It was of course a compromise but it did remove those two pesky 220/240V taps on amplifiers, reducing costs.

 

As an aged dog myself, I grew up with 240V and sort of assumed that the particular amp would work in the UK. I contacted the company and they were very helpful. As a retired Electronic Engineer, I still have much of my equipment (boasting again) and  I was able to talk to them on a technical level and we soon sorted the problem out. The point here is that there are some good Chinese companies, but many either do not understand out local conditions or simply don't care as they are just resellers.

 

So the lesson is, understand and study the specs and buy from reputable sellers. There are Companies here in the UK, Europe and the USA that sell low cost amps and if they sell them, they are responsible for them. However the safe bet is to buy from reputable brand from a reputable seller.

 

 

The harmonizing of the UK to 230V nominal European standards means that the high line limits are the same. 
 

For amps that truly comply with CE under the CB scheme, they are tested at the high line limits, it’s one of the required tests that the amp must pass.

Most of the “no name” amps available on the various websites do not carry valid CB safety or EMC certifications, and those that have the CE mark applied are often not eligible to carry that mark.

On 02/07/2022 at 14:17, prowla said:

I found a great 4-channel 1U 4x1300 Watt power amp on ebay. 
It took a couple of weeks to arrive and I had to pay duty on it. 
I got around to connecting it up this evening. 
Plugged it in, pop!, house power tripped, slight electrical smell. 
Grrr, now I’ve got to chase up the issue with the seller. 
A load of hassle and presumably I’ll lose money on the inevitable return. 
 

IIRC, some of us tried to warn you (didn't we?) 

We have a saying here... when you choose to sleep with snakes, it's likely that you will get bitten. It goes hand in hand with "buy once, cry once".

2 hours ago, leroydiamond said:

AC voltage in the UK IS RATED AT 240V and has been measured up to 250V. 220V is standard Voltage in EU, so that might be an issue. 

Actually, the standard voltage in Europe is now nominal 230V, the UK began the harmonizing to nominal 230V about 25-30 years ago. Initially, part of this harmonization included a change (lowering) of the maximum voltage to +5% so 240V x 1.05 = 252V which is close enough to the EU's 230V x 1.1 = 253V for high line limits. Slowly the nominal 240V has drifted down, combined in part with a tightening of the low line tolerance (now +10%/-6%) which brings it within the standard EU limits.