X1 preamplifier circuit advice

AD · 13th April 2008, 12:53 PM

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

analog_sa · 13th April 2008, 03:57 PM

Quote:

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

Doesn't look like there are any.

Nelson Pass · 13th April 2008, 04:32 PM

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.

AD · 13th April 2008, 04:59 PM

Thank you, Mr. Pass for your information and for taking your time to advise me!

analog_sa · 13th April 2008, 05:58 PM

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?

Nelson Pass · 13th April 2008, 10:46 PM

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)

GRollins · 14th April 2008, 11:30 PM

And it's entirely because their Pass preamps aren't causing DC problems that you have fine customers in Sri Lanka.

Grey

Tarasque · 18th April 2008, 05:08 PM

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....)

13th April 2008, 12:53 PM	#1
AD diyAudio Member Join Date: Jan 2003 Location: Slovenia	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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13th April 2008, 04:32 PM	#3
Nelson Pass The one and only Join Date: Mar 2001	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.

13th April 2008, 04:59 PM	#4
AD diyAudio Member Join Date: Jan 2003 Location: Slovenia	Thank you, Mr. Pass for your information and for taking your time to advise me!

13th April 2008, 10:46 PM	#6
Nelson Pass The one and only Join Date: Mar 2001	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)

14th April 2008, 11:30 PM	#7
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	And it's entirely because their Pass preamps aren't causing DC problems that you have fine customers in Sri Lanka. Grey

18th April 2008, 05:08 PM	#8
Tarasque diyAudio Member Join Date: Dec 2002 Location: Netherlands	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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