Regulated PSU but different powers

[richie00boy]

I have an Alpine MRV-F300 which boasts "Regulated PWM power supply" on the case. However, the rated power output is different for 12V and 14.4V. How can this be if the PSU is regulated?

[Perry Babin]

Regulation doesn't necessarily mean that the output will remain the same at all possible B+ voltages. The regulator may not begin to limit the rail voltage until B+ reaches 14v. Some amplifiers reach their regulated/target voltage as low as 11 volts of B+. For those amps, the output would remain the same from 11 volts up to the point where the over-voltage protection engages.

[richie00boy]

Bit pointless then really, if it needs about 14V before it starts regulating? I suppose it's just a measure of overvoltage protection.

[jol50]

If I understand how these work correctly, maybe full duty cycle on the power mosfets can't give as high of a rail voltage at the lower 12v as 14 when at full output? I just checked mine and at idle it backs the fets way down from 6v gates startup to about .5v after a minute or so.

[Eva]

Alpine MRV regulation is very bad. They should never have dared releasing such a poor circuit to the market. What they do is essentially reducing duty cycle when input voltage is above approx. 13V to protect the components on the secondary side from overvoltage. There is no output inductor, they rely only on the leakage inductance of the transformer and the ESR of the capacitors, which get very very hot in the process.

I bench tested a couple of these amplifiers at full music output with a 125A DIY bench power supply set to 14.4V. The internal power supply of the amplifiers had a really bad time with this high input voltage. The capacitors would get too hot to be touched quite quickly, and the transformer and PSU semiconductors were also exhibiting higher than usual losses.

[richie00boy]

So what 4 channel amp of similar power and cost would you recommend? Also what about 2 channel for subs?

[jol50]

I like the Alpines. They are durable and sound good IMO. There are plenty of other amps that work well also kind of depends on how old, how expensive, what you like, etc.

The newer infinity seem to be screwed together pretty well. I have one but have not used it yet so have no idea how well they work. A lot of lower cost amps today are frail in a physical way, they can't even take vibration.

Speaking of PS, I have an old blaupunkt from the 80s that says 'digital power supply.'