What!! Really?

[diydidi]

I just received this chinese made subwoofer. 18'' driver in it to be exact. It's driven by a small amp. One TDA7294 chip. Filter caps are 3300uf 50V. They claim 250WRMS and !00W peak???
This is with +/-50V rails.
Is this a joke? Is it even possible for this chip to deliver the needed power?
Any opinions??

[Mark Hammer]

A +/-50v supply and PS caps rated at 50V? Well, if it does live up to its stated specs, it won't do so for very long!!

[g1]

They claim 250WRMS and !00W peak???

I think you mean 100WRMS and 250W peak? It's supposed to be a 100W chip, so technically is should do it.

[diydidi]

I know!! But check this link:
Qtx : Product : Loudspeakers : QT Series : 170.751UK
I'm sure the chip will be able to do 100W. Just looks wrong to see this chip aside its 18" driver.

[pdf64]

The spec in that link says 1000W max! (250Wrms)
Pete

[g1]

Ok, now I see . They're calling it a 1000W sub woofer, and claiming 250W RMS!
The data sheet for the 7294 says 70W RMS and 100W "music power".
To claim 1000W is really quite funny, I'm sure there will be plenty of guys trying to figure out how to run them off 12 volts in their cars .

[J M Fahey]

1 TDA7294? OK

1000W? = LIE

250W? = LIE

150W? = LIE

Anything else?

[Mick Bailey]

Vox claims 150W for its VT120+. The chip is rated at that, (as RMS), but the back of the amp says the power input is 60w maximum. It's the answer to global energy needs - it produces more power than it consumes. An Eco amp.

The Chinese do it with power tools and motors, too. They must be very small horses in China.

[J M Fahey]

The last few years I've been losing sales of my workhorse 8 channel 300W RMS box mixers to imported "800W/1000W/1200W" ones which cost about the same.

Funny thing is that when I get one of those for repair, they invariably have +/-56V to +/- 65V rails (mine +/-63V) and are loaded with 4 ohms total (same as mine).

How do they get 4X the RMS power is a mystery.

As you say, maybe *their* horses and *ours* are not the same

[Mick Bailey]

And they're both still 1 horsepower!

[pdf64]

'How do they get 4X the RMS power is a mystery.'
That's easy - didn't you mention that 120 and 240Vac power outlets were available for most installations?
You clearly aren't plugging it into the correct outlet
Pete

[J M Fahey]

I should hve thought of that !!!

[g1]

By the way, are you sure the rails are +-50V when powered up? I think the max. limit for that chip is +-40V, so they would be pushing it beyond it's limits.
I think they may have had a typo with the power rating for this sub., as their stand alone power amps seem to be a little more realistically rated: Qtx : Product : Amps Mixers & Sources : QA Series Amps : 172.020UK
That being said, what use is a 30A mains fuse going to be to me when all the circuit breakers in our house 120V electrical panel are 15A?

[52 Bill]

I'm not familiar with these units, but are there more than one chip in these things like in a bridged mode configuration?

[diydidi]

Unloaded supply rails are +/- 50 Volts. No bridge mode here. Only 1 IC