IcePower module

So you didn't have to really get into the drive circuitry, right ? I don't wish that on anyone, even you.

I saw one in a bass amp years ago. It had carbon tracks near the input. (on the board) It was fried, I looked into getting a replacement but for that unit it would be $100 for the part so the job didn't get done. Except for t he big boys here, musicians are cheap, and by necessity because they are br oke.

It had arced over from hot to cold, you could see it. And the same guy had another amp or something in it with the same type of fault, well not really but the same cause I would guess. Too much voltage between hot and cold, b oth of them.

One unit I fixed, but the one with the Icepower no. I quoted it for the who le module which I found for a hundred bucks. I might do like you and fix th e choppers and rectifiers and all that but I am not getting really into it. Too small, probably a four sided board. I would probably have to charge a hundred bucks to not change a hundred buck module.

I don't want to work for three bucks an hour but I will sometimes for my bu siness. It makes up for the times when I make a hundred bucks an hour. Otha , worked for the olman in his days. Got rid of Vette bodies, scrapped the s teel and somehow dealt with the fiberglass n shit. He told the olman "I tak es the good with the bad". That whole episode is a (his)story in and of its elf.

Anyway, nice that you go it working. But you know if you want to get into t he intricacies of it that is a pain in the ass and for a hundred buck thing is not worth it. But this was, kinda.

I would guess you charged fro diodes, transistors, caps and whatever, how m uch did you actually make ?

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** Well tanks pal - it's got enough SMD to choke a brown dog.

** Maybe hit by a lightning spike ?

** No full schem available anywhere - a new Ice Power 125A module would cost me about A#300 plus postage from the USA or Europe. If that were needed, I would get the owner to buy it for me. ** Only the two mosfets were gone, plus a 5AT fuse. I billed the owner A$150 for my time, so it came just inside my estimate/quote of A$200.

But one thing still worries me, the amp output operates as bridged pair and may fail if the ever shorted. It only has a single Speakon on the back, but the owner may well try to use a Speakon to jack lead. Bad news with a 350W amp.

So I'm gonna include a Speakon to Speakon, made with a metre of fancy round cable, plus a matching socket sitting on one end for him to use - for an extra consideration of course !!

Also I will advise NOT sitting it on top of his bass cab, cos doing that shakes stuff to bits.

.... Phil

My comment would be, it's nice to have AC power integrated with the amplifier.

I've been getting class-D amplifier PCBs from China, very cheap, yet many of them seem well engineered and well built. But none of them include a power supply, nor do they offer a suitable power supply. But, damn, these high-power supplies can be more complicated than the amplifier!

--
 Thanks, 
    - Win

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** FYI to Win:

The majority of SMPS integrated with a high powered audio amplifier on the same PCB ( or otherwise) are simple, square wave inverters.

In the wide, wonderful world of power audio engineering, there is simply no need for a regulated or supply frequency free PSU - in order to feed DC p ower to such an amplifier.

Linear amps ( class B or AB or whatever ) are easy to design with almost an y desired degree of PSRR - while class D amps can also have that same abili ty with little difficulty. Just include a sample of the ripple voltage in t he feedback loop.

However, professional power amps ( 2kW per ch and above ) need their PSUs t o incorporate PFC - so that the RMS current draw does not become some insa ne number. Otherwise, it's a PITA to supply enough AC current power to run dozens of the damn things as needed for a major concert.

With PCF, the DC supply for the following *square wave inverter* is virtual ly ripple free and *regulated* - so the amp has the same power spec almost regardless of supply variation. Consider that the AC supply in use may well be a diesel generator, on the end of a long length of three phase cable.

The various IcePower modules ( engineered in Europe, by the B&O company of Denmark ) are decent designs mostly intended for the domestic, hi-fi market - but complete bastards if you are asked or fix one that has failed for an y reason.

Same comment goes for most SMD boards of any complexity.

.... Phil

Yes. Well done, Phil. I enjoy reading about troubleshooting methods. Thanks.

not quite china prices but they have a few with psu

Half-bridge class-D amps are interesting. As they pull power out of one supply rail, they pump power into the other one.

All those huge-power specs must be some sort of intermittent peak music thing. There's no way those tiny boards can get rid of much heat.

You don't think this board can do 100 watts "RMS" into 8 ohms?

I bet it can just fine

What heat? the high quality ones are like 95% efficient just like a SMPS.

With that big heat sink, maybe so. But they have 500 watt units, and kilowatt boards, that look scary.

We're designing a 120 watt full-bridge class D amp, and I'm sure going to have a big heat sink and forced air flow.

The problem with naive class D for consumer audio applications is that the efficiency is quite good, way better than a linear amp, when running flat out but nobody uses an amp that way, at normal volume levels the power efficiency stinks and is not that much better than a class B.

In cheap audio gear they put the cheap kind in there cuz they're cheap and you have to heat sink a linear amp for the worst case. If you want great efficiency at low power outputs on a class D you have to resort to many of the same tricks as a linear amp like rail tracking/switching for a fixed supply or dynamically boosting the supply voltage of SMPS supply for the peaks

Do they spec that it can?

The audio business is dominated by various techniques of creative lying. The aerospace business isn't.

1KW x 5% is 50 watts. If indeed it is 95% efficient.

Some of the wire on those inductors looks absurd for the specified currents.

Yeah, but... the usual situation in audio is that you allow 5x headroom (current over 20% of the peak value is always going to make distortion). It's part of the creative lying process to rely on statistical low averages for dissipation, while quoting the peaks...

I tried a class D amplifier design around 1980; it just wasn't feasible to handle the current spikes with low-cost hardware (in fact, for some reason, my best choice for power transistor was PNP silicon). That high current makes a strong impetus to use short wires, so the excessively-compact design of the IcePower module looks... efficient.

You can buy a 300 watt Chinese amp that comes with a tiny wall wart.

I'm planning to use the TI TPA3255. We have the eval board and it seems to be unbreakable. But it will have a heat sink and some planned air flow.

For low powers of a watt or two at audio frequency from a uP I just run PWM into an LM386 pulling double duty as a 2 pole Sallen-Key filter, a Bessel/Butterworth hybrid from the TI Filterpro designer. 2.2k, 4.7k,

0.47u x2. inverting input biased through a divider from the output with a diode drop to compensate for the internal offset. the old '386 can drive inductive loads and small motors too and take a lot of punishment

oh, and cap to bypass the internal feedback so it has high open loop gain

That chip has on-board MOSFETs, with high Ron, so it can't be optimized for high efficiency. I prefer to separate the two functions. For example, an IRS2092 clocks to 0.8MHz, and it has optimized MOSFET pairs to go with it, like the IRFI4020H. Or select other MOSFETs with much lower Ron, and proper thermal tabs, like the 330-watt IRFB4227, 20-milliohms (that's 5x lower), used in some 1kW-rated amplifiers.

--
 Thanks, 
    - Win

The fets in the TPA3255 are 85 mohms, and in mono mode I'll parallel the two half-bridges. I only need 120 watts!

The advantage of a single amp chip is all the protections that it includes. And the small size and low parts count. And price, although that's not a big deal on this project... one output transformer costs

10x the TI chip. One heat sink will cost a bunch more than an amp chip.