XE load - How does it work

Killerwatt · Post by **Killerwatt** » Tue Aug 21, 2012 1:51 am

Hi guys
So I Currently own 2 PG xenon amps, a 100.4 and a 200.4. Very impressed with these amps, clean and powerfull.
I asked the following on one of the local forums but i was dricected here for more assistance.

So I know the principals behind xe load and similar strategies by jl, etc. Basically they will cut rail voltage when a lower load/higher current is sensed on the outputs. Am I correct in saying this for the Xenons? Now I also noticed that the front and rear channels on the Xenon’s run of only one power supply.

So assuming a normal setup where you have a 4 ohm sub bridged on 2 channels and a set of 4 ohm splits on the remaining channels. This would reduce the rail voltage to accommodate the sub, right? This would mean that the amp is effectively reducing the power on the splits since its on the same supply?

So to get all the power out of the amp you would either need an 8 ohm sub or 2 ohm splits?
Not that I’m complaining, 100wrms is more than enough for mid-basses in my opinion.

I did some more thinking and came up with the following...
The rail voltage might be regulated after the main capacitors. In which case it is possible to regulate each set of channels seperately. Also does xe load monitor the current draw at the output of the transistors or at the power supply side of things?
If it does it at the power supply then xe load might not even kick in with a bridged 4 ohm sub in which case you could get much more than 400wrm to your sub. Asumming that the voltage is regulated for all 4 channels simultaneously.

I did take the cover off my 100.4 in an attempt to figure out what is going on there but it seem that much is on the bottom of the pcb and i really do not want to take it out. One more thing is that there are 4 pots amongst the output stage, wonder If this is to adjust the gains somehow... Was tempted to touch them but I resisted.

I know its a very long story but any help would be appreciated.
I just would like to learn a bit more about these amps and hopefully how to get the most out of my system

Thank you in advance

Post by **Francious70** » Tue Aug 21, 2012 5:27 am

That's an interesting question because I run the same setup.

Xenon100.4
Front speakers @ 4 ohms
4 ohm sub bridged on the rear channel

Post by **Eric D** » Tue Aug 21, 2012 5:35 am

What if the rail voltage stays the same, and the Xe.load feature just reduces gain of the front or rear amplifier stages independently? (by cutting preamp voltage for example)

I don't think this is what is actually happening on the Xenon amps, but since I have never really been told how they work, I think this could be a possibility.

Killerwatt · Post by **Killerwatt** » Tue Aug 21, 2012 8:12 am

Francious, I suspect that most of us run a similar configuration.

Eric, I suspect you maybe right. I remember the soundbuggy articles that said sometheing about variable voltage regulators for the daughterboards.
But if I remember the 2ch and 4ch amps had the same number of regulators.

So bigest questions are how does xe load actually work and what do those 4 pots do...

Post by **Eric D** » Tue Aug 21, 2012 10:09 am

I don't know if the voltage regulators would be related.

There are a lot of ICs on the board which are not on a typical amp. If any one of them were a digitally controlled analog resistor (they make them, I used some years back on a project), a circuit could cut back the preamp voltage.

I am pretty sure the full range Xenon amps run at normal (max) output, and then cut back their output when the current demand hits a certain threshold. I don't think they step back up to full output until you power them off, which would reset them.

The mono amps on the other hand detect the load, and adjust accordingly upon power up.

There is a good chance that even with a 4 ohm mono load on the rear of a Xenon 4-channel, the amp will not drop down to a low power state with typical use.

Killerwatt · Post by **Killerwatt** » Tue Aug 21, 2012 8:46 pm

Interesting thoughts there Eric, thanks for the info. If you are right then there is really nothing stopping a 200.4 giving a bridged 4 ohm sub up to 800wrms. Provided the other channels are not used or used at a low gain.
By the way, do you do the soundbuggy articles?

00goobs · Post by **00goobs** » Tue Aug 21, 2012 9:57 pm

I almost think it is easier to vary the amperage through the output transistors using PWM switching which would be almost undetectable sonically with capacitor banks and a load. Similar to digital amps but not exactly digital, hehehe...

An easy way to be 100% sure the load never goes above 200 watts per channel is a resistor in line with the outputs, where even a dead short would be the resistance of the in line resistor...

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Killerwatt · Post by **Killerwatt** » Tue Aug 21, 2012 11:44 pm

I think that would be a clas abd amp, ha ha.
I get what you saying, but im not sure thats the best way to cap power or the easiest.