Pearl: Coupling capacitor

h_a · 18th December 2006, 01:23 PM

Hi folks!

First a big thanks to Mr. Colburn and Mr. Pass for sharing the pearl with us!!

I'm getting my parts hopefully this week, so I can start building it - woa my excitement is really unbearable!!

One question crossed my mind: I could get my hands on an supposedly excellent cap (Mundorf Supreme: tan d: 0.0002 bei 1kHz, tan d: 0.0001 bei 10kHz, fully free of induction), however instead of the 10uF only a 1uF would fit nicely.

Are there any disadvantages if I replace the 10uF with a 1uF and raise the resistor R15 from 100K to 1MOhm (since this is a highpass and the product capacity*resitance stays the same the resonance stays also the same)?

Was this particular combination 10uF/100KOhm chosen to minimize noise? If yes would the non-magnetic Visay CMF55 low-noise resistor help?

Thanks a lot!!

With kind regards, Hannes

PS: what do you think: is a Mundorf Supreme worth the money? I mean compared to a standard Mundorf MCap that is.

GRollins · 18th December 2006, 05:19 PM

It's not R15 that you're worried about--it's the input impedance of the device (presumed to be a preamp) that follows the phono stage.
Let's say that you've got a 10k input impedance in your preamp. If you're using a 1uF coupling cap, you're going to be 3dB down at roughly 17 or 18Hz (don't forget that R15 is in parallel with the preamp, lowering the Zin still further). You'll be one or two dB down well up into the audible range, no matter how you look at it.
And that's assuming that your preamp is at 10k--it might be lower, especially some of the DIY designs. If you happen to use a tube unit with a Zin of something like 100k, then things will be much better, but you'll always be at the mercy of whatever the Zin happens to be on any given preamp. In practical terms, your Pearl won't sound the same at your friend's house as it does at home and you're likely to be missing some of the bass.

Grey

h_a · 19th December 2006, 07:54 AM

Thanks a lot for your truly enlightening reply!!

Didn't thought of that.

So thats for me another proof, that one should not change circuits unless one could design them themself.

Whoa. 3dB@18Hz would really hurt

With kind regards, Hannes

GRollins · 19th December 2006, 12:36 PM

There are some parts you can fiddle with and some you can't--at least without having a plan. Changing the DC blocking cap won't break the Pearl. It just won't sound the same.

Grey

wayne325 · 21st December 2006, 11:24 PM

Why not put a 10 uF cap in there and bypass it using your 1 uF Mundorf?
If it will fit - it may not be the most beautiful thing in the world, but
you'll get your Mundorf....

h_a · 10th January 2007, 05:51 PM

Sorry for my late reply!

Thanks a lot for your suggestion! You're right! Nice idea!

Well maybe it's not worth all the fuzz...

Cheers, Hannes

18th December 2006, 01:23 PM	#1
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Pearl: Coupling capacitor Hi folks! First a big thanks to Mr. Colburn and Mr. Pass for sharing the pearl with us!! I'm getting my parts hopefully this week, so I can start building it - woa my excitement is really unbearable!! One question crossed my mind: I could get my hands on an supposedly excellent cap (Mundorf Supreme: tan d: 0.0002 bei 1kHz, tan d: 0.0001 bei 10kHz, fully free of induction), however instead of the 10uF only a 1uF would fit nicely. Are there any disadvantages if I replace the 10uF with a 1uF and raise the resistor R15 from 100K to 1MOhm (since this is a highpass and the product capacity*resitance stays the same the resonance stays also the same)? Was this particular combination 10uF/100KOhm chosen to minimize noise? If yes would the non-magnetic Visay CMF55 low-noise resistor help? Thanks a lot!! With kind regards, Hannes PS: what do you think: is a Mundorf Supreme worth the money? I mean compared to a standard Mundorf MCap that is.

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18th December 2006, 05:19 PM	#2
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	It's not R15 that you're worried about--it's the input impedance of the device (presumed to be a preamp) that follows the phono stage. Let's say that you've got a 10k input impedance in your preamp. If you're using a 1uF coupling cap, you're going to be 3dB down at roughly 17 or 18Hz (don't forget that R15 is in parallel with the preamp, lowering the Zin still further). You'll be one or two dB down well up into the audible range, no matter how you look at it. And that's assuming that your preamp is at 10k--it might be lower, especially some of the DIY designs. If you happen to use a tube unit with a Zin of something like 100k, then things will be much better, but you'll always be at the mercy of whatever the Zin happens to be on any given preamp. In practical terms, your Pearl won't sound the same at your friend's house as it does at home and you're likely to be missing some of the bass. Grey

19th December 2006, 07:54 AM	#3
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Thanks a lot for your truly enlightening reply!! Didn't thought of that. So thats for me another proof, that one should not change circuits unless one could design them themself. Whoa. 3dB@18Hz would really hurt With kind regards, Hannes

19th December 2006, 12:36 PM	#4
GRollins diyAudio Member Join Date: Feb 2001 Location: Columbia, SC	There are some parts you can fiddle with and some you can't--at least without having a plan. Changing the DC blocking cap won't break the Pearl. It just won't sound the same. Grey

21st December 2006, 11:24 PM	#5
wayne325 diyAudio Member Join Date: Jun 2005 Location: Dallas, Texas	Why not put a 10 uF cap in there and bypass it using your 1 uF Mundorf? If it will fit - it may not be the most beautiful thing in the world, but you'll get your Mundorf....

10th January 2007, 05:51 PM	#6
h_a diyAudio Member Join Date: Sep 2006 Location: Graz, Austria	Sorry for my late reply! Thanks a lot for your suggestion! You're right! Nice idea! Well maybe it's not worth all the fuzz... Cheers, Hannes