Why don't the Aleph amplifiers have input RC filters?

[GregH2]

Is it because they don't need them (low noise susceptibility), or for sonic benefit? Would love to know your thoughts!

Cheers,

Greg.

[nigelwright7557]

The input filter is usually to filter out RF and stop the amplifier amplifying out of band signals.

[GregH2]

Thanks Nigel,

I'm well aware of what they are for. My question is why don't the Pass Labs amplifiers have them (unlike nearly every other commercial design on the market)?

Cheers,

Greg.

[wayne]

If you think about it they did. MOSFET 250 PF or more JFET 5-30 PF. Add some resistance and a Zener = low pass.

[Zen Mod]

funny Wayne ;

that's not on input ( I mean -drawn on)

[GregH2]

Originally Posted by wayne

If you think about it they did. MOSFET 250 PF or more JFET 5-30 PF. Add some resistance and a Zener = low pass.

Brilliant!

[AndrewT]

I'll repeat the question:

Why don't the Aleph amplifiers have input RC filters?

[Nelson Pass]

Because they cost money.

[srh]

They don't need bandwidth limiting and the fets don't have the problems with rfi that bipolars do.

[wayne]

One of the first customers for a pair of Aleph 1's was a software engineer for a wireless company. He tested the amps by firing up a transmitter on top of them. They worked fine after others didn't and he bought them on the spot.