Why don't the Aleph amplifiers have input RC filters? - diyAudio
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Old 13th December 2012, 02:28 AM   #1
GregH2 is offline GregH2  Australia
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Default Why don't the Aleph amplifiers have input RC filters?

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

Cheers,

Greg.
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Old 13th December 2012, 02:41 AM   #2
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The input filter is usually to filter out RF and stop the amplifier amplifying out of band signals.
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Old 13th December 2012, 02:58 AM   #3
GregH2 is offline GregH2  Australia
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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.
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Old 14th December 2012, 06:35 AM   #4
wayne is offline wayne  United States
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If you think about it they did. MOSFET 250 PF or more JFET 5-30 PF. Add some resistance and a Zener = low pass.
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Old 14th December 2012, 06:54 AM   #5
Zen Mod is offline Zen Mod  Serbia
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funny Wayne ;

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

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Old 15th December 2012, 01:20 PM   #6
GregH2 is offline GregH2  Australia
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Quote:
Originally Posted by wayne View Post
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!
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Old 15th December 2012, 01:22 PM   #7
AndrewT is offline AndrewT  Scotland
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I'll repeat the question:
Quote:
Why don't the Aleph amplifiers have input RC filters?
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Old 15th December 2012, 04:18 PM   #8
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Because they cost money.

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Old 16th December 2012, 12:22 AM   #9
srh is offline srh  New Zealand
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They don't need bandwidth limiting and the fets don't have the problems with rfi that bipolars do.
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Old 16th December 2012, 02:35 AM   #10
wayne is offline wayne  United States
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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.
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