SDA-1C XO upgrade - 750pF cap questions

thsmith
thsmith Posts: 6,082
edited October 2009 in Vintage Speakers
I have been reading everything I can find on upgrading my 1C XO. Mainly these 3 threads.

https://shop.polkaudio.com/forums/showthread.php?t=47379

http://www.polkaudio.com/forums/showthread.php?t=57467&highlight=SDA+crossover

http://www.polkaudio.com/forums/showthread.php?t=40330&highlight=SDA+crossover

I am confused about what to do with the 750pF cap. Seems most people bypass it.

Why ?

Thanks,

Tracy
Speakers: SDA-1C (most all the goodies)
Preamp: Joule Electra LA-150 MKII SE
Amp: Wright WPA 50-50 EAT KT88s
Analog: Marantz TT-15S1 MBS Glider SL| Wright WPP100C Amperex BB 6er5 and 7316 & WPM-100 SUT
Digital: Mac mini 2.3GHz dual-core i5 8g RAM 1.5 TB HDD Music Server Amarra (memory play) - USB - W4S DAC 2
Cables: Mits S3 IC and Spk cables| PS Audio PCs
Post edited by thsmith on
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Comments

  • Face
    Face Posts: 14,340
    edited July 2009
    It was done to improve the SQ of the caps they were bypassing. Capacitor technology has come a long way since then and they are no longer needed. Plus bypassing can cause artifacts and smearing, you should use a single cap(value) whenever possible.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • NJPOLKER
    NJPOLKER Posts: 3,474
    edited July 2009
    Its a bypass cap which is not needed with higher performing capacitors. Majority of people also feel they give a funky/fake/colored sound or something like that.
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  • NJPOLKER
    NJPOLKER Posts: 3,474
    edited July 2009
    Face, your faster than me and more knowledgeable too!!
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  • thsmith
    thsmith Posts: 6,082
    edited July 2009
    Thanks Face, So all I need is the 12uF HQ film cap and remove the 750pF cap ?
    Speakers: SDA-1C (most all the goodies)
    Preamp: Joule Electra LA-150 MKII SE
    Amp: Wright WPA 50-50 EAT KT88s
    Analog: Marantz TT-15S1 MBS Glider SL| Wright WPP100C Amperex BB 6er5 and 7316 & WPM-100 SUT
    Digital: Mac mini 2.3GHz dual-core i5 8g RAM 1.5 TB HDD Music Server Amarra (memory play) - USB - W4S DAC 2
    Cables: Mits S3 IC and Spk cables| PS Audio PCs
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  • Face
    Face Posts: 14,340
    edited July 2009
    Correct.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • Conradicles
    Conradicles Posts: 6,134
    edited September 2009
    Silly question...but when you guys say "bypass"...that means just totally remove this little 750pf and NOT replace with a jumper wire correct?

    Doing mine tomorrow and just trying to get all the facts. Thanks!
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  • ben62670
    ben62670 Posts: 15,969
    edited September 2009
    Yes remove, and place nothing in the hole the bypass cap came out of.
    Ben.
    Please. Please contact me a ben62670 @ yahoo.com. Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.
    Thanks
    Ben
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  • kawizx9r
    kawizx9r Posts: 5,150
    edited September 2009
    Oh whoa, over here Ben's been helping me alot in choosing my caps for my upgrade as well. There's a 750pF in there?...it wasn't in the SDA parts list sticky thread. Glad I read this post, thanks guys!
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  • Systems
    Systems Posts: 14,873
    edited September 2009
    Conradicles wrote: »
    NOT replace with a jumper wire correct?
    Definately no to the wire jumper.Adding one would effectively remove the main cap(12uf)from the signal path,thus the tweets would be receiving the full frequency range.The result will be tweeter failure not to mention horrible SQ before they expire.
    Testing
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  • thsmith
    thsmith Posts: 6,082
    edited October 2009
    Conradicles wrote: »
    Silly question...but when you guys say "bypass"...that means just totally remove this little 750pf and NOT replace with a jumper wire correct?

    Doing mine tomorrow and just trying to get all the facts. Thanks!

    Keep us posted, I am ordering my parts today.
    Speakers: SDA-1C (most all the goodies)
    Preamp: Joule Electra LA-150 MKII SE
    Amp: Wright WPA 50-50 EAT KT88s
    Analog: Marantz TT-15S1 MBS Glider SL| Wright WPP100C Amperex BB 6er5 and 7316 & WPM-100 SUT
    Digital: Mac mini 2.3GHz dual-core i5 8g RAM 1.5 TB HDD Music Server Amarra (memory play) - USB - W4S DAC 2
    Cables: Mits S3 IC and Spk cables| PS Audio PCs
    · Share on FacebookShare on Twitter