Wednesday, January 30, 2008

A 160W per channel Quad 303?

On Ebay such a beast is for sale, but what is it?

We get a lot of questions about this offering. Can you do that? Yes we can (maybe), but we won’t. See comments.

Can you also glue new capacitors on old ones, and leave corroded trimmerpot's in to place to maximise the profit? Do you also falsify graphs to proof your point? Yes we can, but we don’t.

The claimed 80W RMS in 8 Ohm is easy done, remove the regulated supply, ignore the fact why Quad did design this in the first place, and run the amp on an unregulated 90V supply voltage.

The second part, 160W RMS in 4 ohm is a lot more difficult, if possible. Our advice: check before you buy it, if the unit really deliver this kind of power. RMS, two channels, not peak-to-peak.

Why don’t we do this kind of work?

We work within the Quad design philosophy. We only upgrade and improve things if they really matter and are necessary because of modern speakers and sources.

If you need a 160W in 4 Ohm, buy a 520 series or a 606, 707 and 909. But remember, you need ten times the power to hear a sound at twice the original volume.

Joost Plugge


Blogger Stefaan said...

No way the transformer can deliver 500VA, the power that would be necessary to get a total of 320 W RMS output power.

You would need 3 of those transformers.


5:31 PM  
Blogger Stefaan said...

Well, the transformer is not the biggest problem, but it is a problem. Every real amplifier has a internal resistance, the 303 has a output capacitor, a coil and a emittor resistance all in series with the loadspeaker. The voltage drop across this impedance is at least linear with the current flowing through this impedance. So it is impossible to get exactly double the power at half the load. There is no amplifier on the world with this kind of specs, read all the Audio magazines. The next problem is to deliver this kind of trick with the same input level, most amplifiers, including the 303 will have a lower gain at high output currents. Increasing the input level to get a result like this is cheating. There are amps with specs close like this one, but they make use of dynamic power supply's and sometimes other special circuits. If it was true, every amplifier manufacturer will pay a fortune to hire the man.

Joost Plugge

2:04 PM  
Blogger Stefaan said...

The seller of this 'wonder' 303 show a diagram in his advertisement that should proof that his amp deliver 160 watts in 8 ohms. He uses the standard power output graph of the 303, he extends the 33V voltage limiter line. In his view this line crosses the 4 ohm impedance line at 160 watts. Simple calculation show's that this line will intercept the 4ohm line at 136.125 watt's. So he does not understand this graph in the first place, I will not help him, second, he lies about the real outcome of this calculation. If you still interested to buy such a amp, you are on your own.
Joost Plugge

3:04 AM  
Blogger Stefaan said...

In the last comment you should read 160 watt's RMS in to 4 ohms instead of 8 ohms.

Joost Plugge

3:23 AM  

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