A Question Regarding Peavey's CS 800 Power Transformer

[OMNIFEX]

Hi.

On the rear of the Peavey CS 800, it states 1500 watts and offers a 15-amp fuse.

I would imagine the power transformer would be no less than 2 kVA. However, upon reading two passages from the PDF manual, I am uncertain if my assumptions are correct. This is what it states,

“Due to the high currents (greater than 14 amps) at full output, it is recommended to use No.16 or larger wire be used whenever possible.” In addition to, “It should be connected to a circuit capable of at least 20 amps continuous, or greater.”

14 amperes in a 4-ohm load equates to 784 watts or 56 volts per channel.

Would that make the power transformer 3.4kVA taken into consideration how cool it operates?

Cheers!

[jaycee]

If it was 3.4kVA you wouldn't be able to pick it up

The transformer is probably a lot less, maybe 1kVA or so. The larger fuse is to prevent it rupturing due to inrush current when the power supply is started from cold and the filter capacitors are drained. From a few pictures it looks like a toroidal type and these have very high inrush when they first magnetise.

Here's a link to a service manual if you really want to check it

http://www.eserviceinfo.com/download...ey_cs-800.html

[jaycee]

Actually, by the look of it, the CS800 doesn't use a conventional transformer - it seems like it uses some kind of switch mode supply, with IGBT's as the switching devices! I wonder if they were trying to copy Carver...

[OMNIFEX]

Cheers jaycee!

What you are examining is the CS 800S. I am referring to the CS 800.

That amplifier is completely different from the near 40-year-old design I am questioning.

[wg_ski]

The power trafo in the older ones is about 1.5kVA. A 2kVA would barely fit in the chassis - let alone have room for that much heatsink. I have a bunch of modern 2 and 2.5kVA Signals - and they are WAY larger than what's in any CS800 from any vintage.

The old CS800, putting out 1/3 power with pink noise at minimum impedance will draw around 13A off the wall. That's about 1500 VA which is what the trafo will be sized for. With light clipping with the usual 10dB dymanic, the current draw will actually be less. For more modern 2U amps, they size the trafo for 1/8 power at typical impedance (not minimum). It will draw more - in the neighborhood of 20A - at full signal sine wave. Although full power peaks will be short enough not to trip a 15A breaker, it will still draw that full 20A for a few hundred milliseconds evert time the bass hits. The voltage drop in your AC distribution system is determined by your peak load - NOT the average! That's why you need as much copper as practical. Also note that output (speaker) current and AC mains draw are not the same thing.

[OMNIFEX]

Cheers wg_ski!

Based on your reply would that mean the majority of pro amplifiers on the market offering 2 - 4 times the amount of the CS 800 in terms of watts is using 1 kVA or less Power Transformers?

[wg_ski]

That is exactly what they do.

[OMNIFEX]

I am at a lost of words.



Cheers!

[Rembulan]

Hi,
I see why the used CS800 still has good value