Funny review of the new VM 4ch

[Flastrongman 10+ year member]

VM 4ch quickie review.... - FloridaSPL

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[Linkz 10+ year member]

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Im not signing up to read a fvcking review. copy paste it.

It's crap. don't buy.

/thread

 

[silvercookie 5,000+ posts]

Had this **** beast dropped off today, and well....yeah. I had a few minutes between jobs coming in to crank it up quick, I can do something a little more detailed with more pics if anyone wants but I think this tells the story. First off, whole stole the rest of the guts?

Before we get to numbers here's a few things I noticed:

1. The gain is junk. At full low the amp still puts out a fair amount of sound even with less than 0.5 volt input. I didn't meter the output voltage but at 1000hz it was plenty of sound to hear from my showroom with the speaker in the bay on the bench. Why this matters: Noise Floor! This amp is going to hiss, squeal, whine like nuts. And if you have a good HU/crossover/EQ ahead of it feeding any sort of good input voltage it's going to clip hard real quick. If I have time later I'd like to hook it to one of my 5 volt Sony radios to test this. The manual says it'll take 8 volts. Um, no.

2. It's built dumb. The terminals are under the edge of the endcap, so you have to remove the endcap plastic thing to hook it up.

The test rig was a 12 volt battery sitting at about 12.9 and my nano scope. Speaker was an 8" Bazooka 4ohm. Bass boost was fully off (according to the knob) and x-overs were full range during the whole test.

Numbers:

1 channel playing 60hz got 10.5 volts before it clipped. 4 ohm nominal speaker, rising to around 8.1 while playing. That's under 14 watts of clean power calculating in the rise.

Same setup playing 1000hz got to 10.9 before it clipped. I also noticed an oddity in the waveform, which is the picture below. That notch certainly doesn't belong there. It's always there regardless of how hard the amp is playing. Also the wave constantly shifted up and down while playing the tone, meaning that the output level was varying up and down a few volts even when it should have been holding dead steady. I tried another speaker to verify it wasn't some odd impedance thing and it wasn't.

I also tried 4 ohm load resistors instead of speakers. These actually metered at 5.1 ohm. They still have some rise because they get warm quick and the impedance will shoot up when they're hot so I just just "burping" the amp into them. Still the amp is limited to right at 10.7 volts per channel before it clips. That's simply all the output voltage the amp's guts can make, regardless of input voltage or load. So if we're generous and say it made 11 volts at 5 ohm then it can cleanly make about 23 watts of power per channel.

I verified the DC current draw with a single channel playing 60hz on the speaker. 4.3 amps at the point of clipping.

That's all I got, I've got other cars to work on. But from that 10 minute test I can determine this: This company is junk and is ripping off every person who pays for this stuff. This amp produced less than 10% of it's rated power even if we're being generous. With the bass boost maxed and gain maxed I was able to get a blast of 17.4 volts into the resistors but the wave was darn near square.

Here's the pic of the notch in the wave:

Looks like a piece of shit