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Old 13th April 2008, 12:53 PM   #1
AD is offline AD
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Default X1 preamplifier circuit advice

I have the Pass X1 preamplifier but have no schematic of it.

Can anyone advise me if there are any capacitors in the signal path of it (I understand - so are the ones in the power supply, but for the sake of simplificity of information let us skip on those here...), and if they are, which value and part number, if you have access to this information.
I have modified the Xono phono amp by changing most of the caps in the signal path (and some in the PS) with good results, so I am curious if I can improve on the X1 preamp as well.

Andrej
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Old 13th April 2008, 03:57 PM   #2
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Default Re: X1 preamplifier circuit advice

Quote:
Originally posted by AD
are any capacitors in the signal path of it

Doesn't look like there are any.
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Old 13th April 2008, 04:32 PM   #3
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There are film input capacitors (1 or 2 uF depending on the rev #)
and 220 uF + film bypass on the outputs.

You may replace the caps with the parts of your choice, but of
course you bear the consequences of mistakes.

As the to 220 uF output caps, we are currently favoring the Elna
Silk capacitors, of which there is an inexpensive 220 uF at 16V
available.
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Old 13th April 2008, 04:59 PM   #4
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Thank you, Mr. Pass for your information and for taking your time to advise me!
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Old 13th April 2008, 05:58 PM   #5
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Quote:
Originally posted by Nelson Pass
220 uF + film bypass on the outputs.


Wow! Was i wrong?

What's the reason for the 220uF? A 100ohm output attenuator?
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Old 13th April 2008, 10:46 PM   #6
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As a practical matter we don't want any offset (ever) at the output
of a preamp. Fearless DIYers can get away with that, but I don't
want to have the conversation with the customer in Sri Lanka about
adjusting DC offset.

(No insult meant to the many fine customers in Sri Lanka)
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Old 14th April 2008, 11:30 PM   #7
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And it's entirely because their Pass preamps aren't causing DC problems that you have fine customers in Sri Lanka.

Grey
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Old 18th April 2008, 05:08 PM   #8
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That is the benefit of DIY...You can connect the whole chain DC if you whish!




(and search & collect the cones of your drivers if you make a mistake....)
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