agedhorse

Different industries source their products differently. Also, there were some earlier suppliers for both the computer and TV/monitor industry that sourced caps from vendors using counterfeit (and defective) materials. This is a much different situation, and not something that i have seen in the audio world that I live in. As long as the design respects the appropriate limitations of the caps being used, i almost never see an issue with caps.

18 hours ago, JapanAxe said:

I don’t think any of us end users are qualified to assess the reliability and failure modes of different amp types as we have so few examples (i.e. amps owned) to work from. Amp repair people are much better placed to comment on this simply because they see so many on their work benches.

 

So here’s a question for them - are the caps in the SMPS sections of Class D amps their weak point?

No, the ONLY cap failures I have seen in (quality) class D amps are in the SMPS when the user connected the amp to 230V while configured for 115V. This is not a cap issue, and generally there’s a lot more damage from this kind of accident.

Here in N. America, the Streamliners are still covered under the factory flat rate service program. I so rarely see a bad power module that it's almost the last thing on the list of potential issues and the replacement modules are in stock and still a current part.

All the other things are generally simple and straight forward for a QUALIFIED tech, but what's becoming far more of a challenge is finding a truly qualified tech... that's FAR more concerning than a class D amp (or any other amp for that matter).

As far as cost of repair of tube/valve amps being cheaper, has anybody priced out a set of tubes or a replacement transformer lately? Replacing a power module (as rare as it might be) is less costly (by quite a bit) than replacing a set of tubes/valves. Tube/valve amps (in my experience) are much less reliable than a quality solid state amp of any type.

On 19/09/2021 at 14:21, Al Krow said:

 

My guess is that the unit is actually a clone of the Genz Benz Streamliner 900 rather than an Ampeg - given the design clues in terms of front panel look and also layout of the knobs which pretty much mirror the Streamliner's. If it is, that's quite a pedigree unit it's been modelled on (I'm basing that on the  huge amount of love that unit got on bass forums, particularly BC).

 

If it is a faithful Streamliner clone then the bass centre will be set at a more useful 55 Hz rather than a too low 40 Hz, but the 4KHz for the treble would still be as you suggested.

Streamliner on the outside, nothing like it on the inside.

On 11/05/2022 at 09:05, chyc said:

Are items available in the west using this stolen IP? I cannot find any information about this online.

Yes, all over eBay, Ali Express and Ali Baba. If they aren’t purchased through ICEPower directly, or one of their AUTHORIZED distributors, there are usually fake. They look just like the real thing, just a little bit cheaper and no warranty.

On 09/05/2022 at 13:46, Chienmortbb said:

Don't get me wrong, I was not criticizing ICEPower per se. I understand the problem as I had a design stolen for a headphone system for passengers stolen by a flag carrying airline. One that IS in a country that does supposedly operate IP properly. I suppose we should realise that the ICEPower  modules do reduce development costs and time to market and the price we pay is lower initially but that component level repair is not possible.

 

 

 

 

I have also had designs stolen, it’s becoming a bigger and bigger deal as design cycles shorten with increased competition. I feel you pain here.

Even if I was to design an SMPS/class D module, due to the complexity and difficulty to troubleshoot versus the cost of building the module, it would still be less expensive in most cases to simply replace the module.

The problem with the higher technology is that it’s very expensive and time consuming to develop, and even more so to do it reliably. (There are plenty of examples of unreliable “roll your own” designs by big and small manufacturers alike).

In order to amortize these costs (and that includes global safety and EMC certification) to keep the cost per module down, the production volumes need to be much higher than most in the bass industry could ever use in several lifetimes. This is why top tier companies like ICEPower exist, they sell to other industries also, in addition to dominating the bass market. This allows them to spread the NRE costs across hundreds of thousands to millions of modules. Economies of scale are responsible for class D being a viable solution AND a good value to the players.

9 hours ago, Chienmortbb said:

I should add that the ICEPower modules, used by many are also impossible to get schematics for. I have repaired one before but they are difficult. 

I can address this specifically. ICEPower did have some IP that was stolen by (ultimately) a Chinese fabricator and they counterfeited one of their modules which cost them a LOT of money (ultimately in the millions of dollars US). The investment in developing this technology at the level that ICEPower (and other major players) have done is staggering and it's simply not right (morally or ethically) to take away such protections from any company developing their own IP. 

For those of you that might suggest that ICEPower goes after the Chinese company that stole the IP, you must be unfamiliar with the "their country, their rules" concept of business. It's almost impossible to be successful, the loss is both real and unrecoverable.

7 hours ago, tauzero said:

 

As regards listening comparisons, I recommend looking for reviews of hi-fi speaker cables and experiments in double-blind listening tests. Even more revealing, look for reviews of digital interconnect cables (USB and HDMI), for example https://www.whathifi.com/vertere/pulse-d-fi/review

Most claims made in the HI-Fi cable world are preposterous at best and many border on fraudulent IME)

6 hours ago, wateroftyne said:

 

Interesting - I wouldn't have had the Streamliner, TC RH450 or Demeter down as "Euro-modern hard rock/metal" flavour.

Correct, they are not, and that’s what I thought I posted. 

37 minutes ago, Jack said:

 

1x Sansamp RBI or similar popular, bass specific rack preamp 

1x line level a/b switcher 

2x pa power amps, 1 class ab and 1 class d

2x identical (at least identical models) cabinets

Gain match both sides with an rta, put the whole thing (besides the cabs) behind a curtain, walk away, let some fresh people run a double blind test. 

 

I suppose even that wouldn't get to the bottom of this though would it? The amps are going to have different filters, the cabs will have had different lives, etc. Close though. 

This would get you a lot closer to determining the closeness of the two amps, but you would want to repeat the tests swapping the speakers so that if the preference changed it would indicate that the speaker was the most significant variable. 

Speaker variables can vary by as much as 20% in a production run. This CAN be significant.

6 hours ago, stevie said:

 

No, that's hearsay.

No, it's the truth and it was a statement that I posted publicly several times.

7 hours ago, Downunderwonder said:

Only my recollection of Agedhorse's story told on another forum. My first mention of it on this thread was noticed by the man himself so you can take it as fact.

Yes, it is true.

Actually, there are several stories and one (not involving class D specifically but involving confirmation bias and over-confidence in listening abilities) where I rigged a double-blind listening test to select between the same power amp and added only 1/2dB to one amp's level caused a high percentage of people to be "positive" they were listening to two different amps (presented to the group as 2 quite different circuits). Of course there was the cork sniffing swagger, the golden ears proclaiming all kinds of absurdities, the hyperbole, etc. When the curtain was parted and they saw that they had been listening to the SAME amp, the excuses started coming out and it became clear that I had just finished my last day with that company (and the high end Hi-Fi industry as a whole). This was in 1981 or 82 and I was planning on quitting the next day anyway, so it wasn't an unexpected or even unwanted outcome   (This industry was just full of snake-oil marketing that had no bearing on reality or truth of any kind).

The point being that even a small difference in level, or in preamp voicing can make a much bigger impression than most folks realize. 

10 hours ago, wateroftyne said:

 

So in that case I would say I never found a preamp I clicked with on the Cass D's owned, but had a very good hit rate on the A/B's.

Quite a coincidence!

It might be a coincidence, but it's also just as likely (maybe more likely) that you prefer the voicings that were more common in the older designs. Preamp (and speaker) voicings have evolved a lot in the 40 years that I have been designing products and this has been driven primarily by changing player preferences along with changes in music styles. One of the best examples of this that I can think of (off the top of my head) is the Darkglass models, they are what the industry refers to as "Euro-modern hard rock/metal" and is quite different from products we used to offer in our lines (Carbines and Strategy/Prodigy) which were American hard rock/metal oriented. The Euro tone evolved from the American tone as the music itself evolved. Because class D wasn't available (in practice) when these older products were developed, they were by default class AB. When Darkglass revisited this theme with their approach, class D was available and a practical option so that's the direction that they went. The appear to be very successful for those players seeking that voicing.

I did test a Carbine preamp with a class D power amp, it was close enough that nobody was really sure which power amp they were listening to when testing... but that voicing was becoming less and less popular so the decision was made to evolve the Subway line into something that followed the evolving tastes.

In no way does it make you wrong for preferring the amps that you like, but there's a lot more involved than just the amp class.

1 minute ago, Downunderwonder said:

Agedhorse might have some 500w frequency  response curves to change some minds?

I’m not going to get into those specifics here. 

3 minutes ago, wateroftyne said:

 

Fair enough. I'd say my issues in general are more due to response than voicing, though.

There are all kinds of dynamics and voicing modifiers that go into a preamp design. The Streamliner that was mentioned earlier was very much about voicing and dynamics and sounded/felt totally different from the Shuttles even though they both used the same power modules. 
 

There’s a lot more to how an amp sounds/feels than just the power amp design (which can also be designed in ways to exploit or reject a particular aspect of tonality and feel. 

7 hours ago, wateroftyne said:

[deleted duplicate post]

7 hours ago, wateroftyne said:

or maybe … Class D power amps don’t behave in a way people who prefer A/B find pleasing.’

 

I used a Demeter for a few gigs once. Liked the simple preamp, but at volume the sound was the usual blah that I’d experienced many times before with a micro.

 

Tried the Handbox, which has a very similar pre bolted to an A/B power stage. Bingo. Never looked back.

How are the pre’s “very similar”? 
 

Change one or two component and the voicing can change wildly. Unless the preamps are IDENTICAL, you aren’t comparing power amps, you just think you are (which is where confirmation bias comes into play)

Now if you were to say that you preferred one amp over another without insisting that it’s due to the class of power amp, I can totally appreciate that.

I have done double-blind tests regarding which preamp players prefer (not just my designs) and it’s ironic that what many players are convinced they like ends up not being what they chose when they couldn’t see it. 
 

This is why double-blind testing is come, to remove the effects of confirmation bias.

I have designed some very high powered class AB amps back in the day, well received in the pro touring world, but today’s better class D designs are every bit as good when mated to the identical preamp. 

10 hours ago, Stofferson said:

I whole heartily agree.

I went through several class D amps and all failed in some way, either over heating, poor volume or just plain rubbish.

ABM 600 now for the past 3/4 years doesn't weigh a ton and tone and power for days.

Horses for courses I know, and everyone of us has a different idea of what they need, but I need loud and reliable and that's what my amp gives me

Failure and overheating is not a class D issue, it's a "poor design" issue.

I haven't had any of these issues with any of the class D amps I have designed, going back over 15 years.

7 hours ago, EBS_freak said:

 

No problem. Use ambient mics for monitoring (to keep volume down in your ears) and a PA speaker as your rig.

 

I set somebody up with an XR18, a RCF 735, a mic stand with a stereo condenser on. IEM feed from XR18. Job done.

Alternatively, IEMs an a Zoom field recorder work nice for monitoring.

Of course the powered speaker is class D with a SMPS

On 30/04/2022 at 22:58, Waddycall said:

Could there be a difference between the quality of class d technology used in a large rack mount power amp and that squeezed into a tiny bass head?

In some cases they are identical. I have designed both bass amps and touring pro audio powered cabinets using the same modules.

On 29/04/2022 at 13:22, Woodinblack said:

well, don't pit your own money on that bet. 
a class B amp has to lose a lot of heat, class A more so. A class c doesn't have to lose anywhere near as much heat and doesn't need a transformer to get the voltage level down.

the smaller you are, the less heat you can lose, so unless you are at a very small output, an A/B is not going to be that small.

Class C is not a viable topology for audio signals, not in any way.

ALL amps must have a power supply transformer in order to pass safety standards everywhere in the EU and just about everywhere else in the world as well.

Kris needs to put him in touch with Rich. Rich will be able to help him.

There is another problem that’s causing these symptoms. It could be a failed bias supply, a short from grid to cathode in one of the tubes, a screen to grid short in one of the tubes, etc. 

Correctly identifying the cause is essential to a proper repair.

He can always e-mail our service manager Rich, he will know who to contact in the UK/EU.

The speaker muting relay stuck in the mute position is unlikely (very unlikely) to cause a set of power tubes to fail. 

21 minutes ago, Woody1957 said:

I should have also added that when I opened up the amp I found that all 3 valves did not have a brand name on them, hence the reason for swapping them out.

That’s not uncommon for OEM valves, some manufacturers purchase them unlabeled or labeled with a code only. This is especially true if they have an arrangement to test/screen all parts and return those that don’t part their test criteria.