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    SP14 tube roll - Capacitor upgrade saga



    Posts : 82
    Join date : 2011-04-10
    Location : pittsburgh

    SP14 tube roll - Capacitor upgrade saga

    Post by pigface on Wed Jul 31, 2013 1:52 pm

    So Its been a year since I built the SP14 and have been enjoying it since . It sounds nice
    , but since it was put together  when it was turned on or off there was a crackling sound
    that faded out after a few seconds  . But it didn't have any effect on the sound , just annoying
    and I figured it was a tube .
      I finally decided to try different tubes and   Since I would have it apart to change out the tubes
     and rectifier , and not being able to leave things alone , I figure I would upgrade  the caps while
    I was in there . Easy enough .
       Since they were on sale  and I didn’t want to go way too expensive I decided to going
    to go with the Jenson Copper and oil after reading  alot of reviews  , but they only had
    one of them so I  bought the Dueland’s instead , at unfortunatly alot more $$ .

     Here is where it gets puzzling .   After just changing the caps and nothing else there is  a
    low hum coming from the speakers both channels equally  .  ( It was dead quiet originally
    )  I changed out the tubes  ( three sets ) and rectifier tube (2 different ones ) and  there was  no
    change in the hum doing that in any configuration  ( the original crackling noise is gone
    though ) . It will  hum on either set of output caps the new ones and the old Mundorfs .
    And it gets louder as you go up with the volumn .  It’s not a real loud hum, you don’t
    notice it  from a couple feet away or when the music is playing . but is annoying since it
    was so quiet before the change .

    Also it only hums on when the selector is set to Phono , Aux 1 or Aux 2 , it is quiet on
    CD or Tuner , and it gets a little louder on phono setting when the PH15 is on than when

    I thought it might be because  the caps are so big and where I had them mounted they
    were too close to the wireing that they might be causing the hum from that ( see the
    pictures below ).  I originally soldered them in without removing the board  so as not to
    disturb anything so I didn’t think I hurt any of the wiring .  But after double checking
    everything  I decided to listen to it for a little while  and see what happened .

     Its hard for me to describe but I’ll try my best . Other than the hum  on  first  impression
    right off  the lows - base  was a little tighter smoother not much of a change but it’s there
    . The vocals were the most improved , on a couple of recordings ( blues & rock ) it
    sounded like they were in the room  singing ! very natural sounding .  But the highs which
    they were supposed to be best at reproducing  sounded harsh and brassy , not good at all ,
    at first dissapointing . But after about ten hours or so  they have smoothed out very
    noticably and and sound alot more natural  and right now probobly  not even  fully broken
    in , they are to my ears they are better sounding  all around  than the Mundorf  S/O ‘s  .
    So over all better sounding , and worse at the same time ?

    I decided to take it back apart and move the new caps away from the wires and double
    check the soldering and wires .  The solder looked good but I re-flowed it just to be sure
    the wireing looks undamaged  , but  after doing this  no change  it still hums .

    I did not unsolder the original caps , I just snipped the leads near the board  and soldered
    the new ones in the second set of holes I didn't want to chance damaging the traces . Could
    this be a problem?

    Any suggestions of things to check ? Am I missing somethging obvoius ?  Keep in mind
    I’m not real experienced in troubleshooting , I’m still learing .

    Original build page

    First layout

    New layout


    Posts : 43
    Join date : 2010-02-26

    Re: SP14 tube roll - Capacitor upgrade saga

    Post by ruffian on Thu Aug 01, 2013 12:42 am

    Since the hum changes as you turn up the volume the hum is getting in there between the RCA jacks and the pot.  Are there devices on all of the inputs? Move them around.   If the aux ones are open try shorting them and seeing if the noise goes away.  Does disconnecting the phono and shorting it make the noise go away?

    Is it possible that you damaged some of the leads when installing the Duelunds? Did you unscrew the board and have it away from them when you were soldering?
    Otherwise unscrew the board and pick it up away from the leads and see if the noise changes.  Finally remove the Duelunds.  Don't be afraid to desolder them, just get yourself the right tool to do so.  A wick, braid, a plunger sucker or a Hakko 808 if you want to go all out.
    Also shorten up the unused leads on the torriod while you have it open.


    Posts : 82
    Join date : 2011-04-10
    Location : pittsburgh

    Re: SP14 tube roll - Capacitor upgrade saga

    Post by pigface on Thu Aug 01, 2013 9:59 pm

    First , I forgot to mention there were  the Russian PIO's in the spot I put the Duelands in .

    All spots on the selector have inputs to them including the Aux .  And shorting the inputs , Phono's included didn't change the hum at all .

    I double checked all wire connections and they all looked good .  But while checking the volume and R & L gain attenuator connections  I noticed the hum level changed when I moved the wires . They were in aproxamatly the same place as before the cap change , but I moved them and secured them as close to the case as possible with ties and the hum decreased  about 65% . I then noticed that if I put my hand between the  attenuators and the board the hum decreased  even more  so I made a aluminum shield between the board and the wires and the main hum is 95% gone , you can't hear it unless your ear is within a foot or so of the speaker . I can live with that for now .   Could the bigger capactors be amplifying the noise that the smaller russian caps didn't ?

    I didn't unscrew  and move the board around  since moving the wires going under it didn't make any change in noise . That and because doing so with the caps still soldered in place would be difficult .

    Do you think if i were to use the shielded  "Mogami W2947 S-video"  cable like in this post :     in place of the twisted  wires on the volume attenuator to the board  it would help reduce the remaining hum any  ?   Or could that type cable even be used for that purpose ?

    BUT  there must be two  causes for the him  because the louder hum on the phono position  when the PH15 is turned on is still there. ( when the phono preamp is off the hum is the same as all other  selector switch positions almost gone ) . If I move the phono rca's like to the CD or aux inputs  the hum changes with them so the selector switch isn't the problem .

    Is it possible that this hum problem damaged something in the phono preamp  or could the caps be amplifying something that wasn't noticable before the cap change ?  Or I could have a hum problem in the PH15 starting ?  Pretty coincidental since they were both quiet before the change .
    I would hate to have to remove the new Caps because it does sound better with them .

    I guess I will have to look into the PH15 next  maybe a tube is going bad or a bad connection somewhere in there ?


    Posts : 57
    Join date : 2011-04-05
    Location : Boulder, CO

    Re: SP14 tube roll - Capacitor upgrade saga

    Post by jjones3318 on Thu Aug 01, 2013 10:33 pm

    I'd unscrew the right attenuator and move it to the left of the volume control (just lay it down in the chassis temporarily, on something non-conductive) and see what that does to the hum. I looks like that attenuator may be too close to the transformer.

    Posts : 91
    Join date : 2011-09-20

    Re: SP14 tube roll - Capacitor upgrade saga

    Post by kaner on Thu Aug 01, 2013 10:44 pm

    Did you fix the crackling problem? I've had that issue too and I finally traced it do a bad connection in the tube socket. I cleaned them & then used a small needle to tighten the socket. Problem solved. I don't think it's related to your hum issue, but an easy fix of the crackling.


    Posts : 82
    Join date : 2011-04-10
    Location : pittsburgh

    Re: SP14 tube roll - Capacitor upgrade saga

    Post by pigface on Tue Aug 06, 2013 6:35 pm

    The crackling noise turned out to be a noisy tube .  I didn’t think the cracking noise was
    related to the hum either .  
    Everything is where they were drilled when I recived the kit , The attenuators  are in the
    same place as before the cap change and it’s been quiet for a year before  that  so why
    would they be  a problem now ?

    While checking for any loose connections  I unsoldered the new capacitors  and tried it
    out with just the Mundorfs in there  and the noise was the same as with them  so the new
    caps are not a problem .  

    While I was in there I shortened the tranny wires and also the jumper wires on the bottom of the
    board  and moved them and the  diode light wireing around as far away from the signal
    wires under the board  as possible and that  helped  out  removing a bit of the
    remaining hum also .   So I   reinstalled the Duelands . The main hum problem is almost
    all gone now , you have to have your ear  less than a foot from the speaker to hear it at
    all now.

    On the phono  section hum , I tried out my  GCPH (SS)  phono pre amp from my other
    system  on the SP14 and  that helped  with most of that noise .  The GCPH  is a little noisy
    in the other setup too, but not as much as the PH15 is now .  So I now know the PH15
    must be developing  a noise somewhere.


    Posts : 82
    Join date : 2011-04-10
    Location : pittsburgh

    Re: SP14 tube roll - Capacitor upgrade saga

    Post by pigface on Sat Nov 30, 2013 8:29 pm

    It’s been a while since I posted on my hum problem .  I finally had some time a couple
    weeks ago  to work on it and  I  started out by rewireing  everything except the tape
    monitor  switch . And re-oriented the selector switch wireing  away out from under the
    board  and that  pretty  much got rid of my SP14  hum problem . The only thing I can
    figure is I must have damaged a solder connection on one of the attenuators or broke a
    wire somewere  when I originally mounted the new caps .
     The humming when it was in the Aux position turned out to be from the cablebox as I
    had the tv out plugged in on that position . For now I can live with that as I only use that when
    there is a concert on TV I want to see .

    The humming is now gone and the crackling is gone , sweet
    quiet again .

    The only problem left is the PH15 had developed a hum at I’m guessing at around the same
    time as the SP14 cap mod and it took me a while to figure which one was making  what noise .  
    The power supply on the PH15 had a bulging cap so I completely rebuilt the power
    supply  and that helped some with the noise in it , but not completely . So I have to figure
    that out next . Roy seems to think it's a ground problem so I’m going to start there by eventually
    going over the wireing in it next .When I get some more time .  Hopefully thats all it is and the bad
    cap didn’t damage something else .

    The new caps are not broke in yet but there is  a definate improvement in the sound over
    the  Russian PIO’s and  Mundorf S/O’s .  I can’t explain the differences to you  except to
    say it sounds better  .   The caps worth the big $$$’s though . confused

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    Re: SP14 tube roll - Capacitor upgrade saga

    Post by sKiZo on Sun Dec 01, 2013 3:42 pm

    Could it be the aluminum mounting strap you added for the caps acting as an antenna and inducing noise? Looks like it'd be easy enough to remove that temporarily and see if it makes a difference ...


    Posts : 82
    Join date : 2011-04-10
    Location : pittsburgh

    Re: SP14 tube roll - Capacitor upgrade saga

    Post by pigface on Sun Dec 01, 2013 11:24 pm

    No , thats not a problem , that is in the SP14 .  The last three  are pictures after the re-wireing and it  is quiet again . No more hum .

    In my troubleshooting I tried that , I completely removed the bracket and new caps  and it still had the hum .  So I put them back in .

    It's the PH15 that's  still humming .  I seems I had two different noise problems . I still have to try and figure that problem out yet . When I get some more time.

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