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    SP-8 phono distortion question

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    Tom

    Posts : 174
    Join date : 2011-04-04

    SP-8 phono distortion question

    Post by Tom on Mon Jun 05, 2017 8:47 am

    Hi All -
    I've got an SP-8 preamp I built some years (7, more?) ago.
    I'm hearing some distortion in dense / heavy passages from the phono which is the only input hooked up right now.
    Did some swapping and it's not the amp, will switch carts to check that too but think I it's in the preamp.
    I had a spare set of line stage 12AU7s that I swapped in, no help.
    I don't have any 12AX7 spares to try on the phono stage but can order some.
    And / or a new rectifier tube that I don't remember the digits on right now.

    Suggestions?

    Thanks! Smile

    Tom

    Posts : 174
    Join date : 2011-04-04

    Re: SP-8 phono distortion question

    Post by Tom on Mon Jun 05, 2017 8:49 am

    Forgot to add that these are NOS RCAs and Sylvanias of unknown quality.
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    corndog71

    Posts : 546
    Join date : 2013-03-19
    Location : It can get windy here

    Re: SP-8 phono distortion question

    Post by corndog71 on Mon Jun 05, 2017 9:18 am

    Have you checked your stylus? Maybe your stylus is due for replacement. If not then it's likely your tubes. 12AU7 is lower in gain than 12AX7 so it might not work well in that circuit. I doubt the rectifier is bad unless your voltages are way off. Time for new tubes!

    ramon68

    Posts : 94
    Join date : 2009-04-12
    Age : 76
    Location : naples fl

    Re: SP-8 phono distortion question

    Post by ramon68 on Mon Jun 05, 2017 9:19 am

    Bent cantilever? Try another cartridge and see what changes.

    Tom

    Posts : 174
    Join date : 2011-04-04

    Re: SP-8 phono distortion question

    Post by Tom on Mon Jun 05, 2017 9:43 am

    Thanks, I'll swap out the cart before anything else.
    This is a Denon DL-110 with maybe 5 years on it.
    May need to be replaced, no fix for this one, right?
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    j beede

    Posts : 394
    Join date : 2011-02-07
    Location : California

    Re: SP-8 phono distortion question

    Post by j beede on Mon Jun 05, 2017 11:05 am

    What you are describing can also be consistent with a dirty stylus. Do you have a LAST or similar stylus brush and fluid? At least try changing your tracking force to see if the behavior changes at all.

    Dogstar

    Posts : 234
    Join date : 2014-06-23

    Re: SP-8 phono distortion question

    Post by Dogstar on Mon Jun 05, 2017 11:23 am

    Tom wrote:Thanks, I'll swap out the cart before anything else.  
    This is a Denon DL-110 with maybe 5 years on it.  
    May need to be replaced, no fix for this one, right?

    I too have a Denon DL-110 cartridge. I do believe the stylus is replaceable but it has to be done by a Denon service tech. It's not a user replaceable stylus.

    Tom

    Posts : 174
    Join date : 2011-04-04

    Re: SP-8 phono distortion question

    Post by Tom on Mon Jun 05, 2017 12:17 pm

    Hey thanks for the info. I checked the tracking mass but did not change it, was ok.

    Also, I brush the stylus with a dry brush but have never "cleaned" it more vigorously.

    May give the "Magic Eraser Method" a try. haha-

    https://uturnaudio.com/blogs/uturn/how-to-clean-your-stylus

    I do play thrift store used vinyl so it could be crunk, invisible to the eye, on the tip.

    Thanks again. You guys are lots of help.

    ramon68

    Posts : 94
    Join date : 2009-04-12
    Age : 76
    Location : naples fl

    Re: SP-8 phono distortion question

    Post by ramon68 on Mon Jun 05, 2017 2:22 pm

    You should never, and I mean NEVER play a second hand record without washing it first after buying. You don't know what's in those grooves.
    You owe it to your stylus and your ears. Good LP cleaning machines are not that expensive.
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    j beede

    Posts : 394
    Join date : 2011-02-07
    Location : California

    Re: SP-8 phono distortion question

    Post by j beede on Mon Jun 05, 2017 8:15 pm

    Tom wrote:Hey thanks for the info.  I checked the tracking mass but did not change it, was ok.

    Also, I brush the stylus with a dry brush but have never "cleaned" it more vigorously.

    May give the "Magic Eraser Method" a try. haha-

    https://uturnaudio.com/blogs/uturn/how-to-clean-your-stylus

    I do play thrift store used vinyl so it could be crunk, invisible to the eye, on the tip.

    Thanks again.  You guys are lots of help.

    My suggestion was to change your tracking force to see if this changes the distortion. Raise it to 2g or 2.5g (temporarily) to see if the distortion changes. If it does, your preamp is less likely to be the problem.

    LAST stylus cleaner works. Buy it from Amazon or your local record store and use it. The results are visible under magnification. If you are playing dirty records your stylus is dirty. This can produce audible distortion--usually in both channels. Consider ordering a Spin Clean from Amazon along with the stylus cleaner.

    Tom

    Posts : 174
    Join date : 2011-04-04

    Re: SP-8 phono distortion question

    Post by Tom on Tue Jun 06, 2017 8:39 am

    Thanks for the clarification on the tracking.
    I popped the headshell off last night and looked at the stylus with a little scope I have. Yuk.
    Cleaning needed. I'll report back afterwards.

    I do wash some (not all! Embarassed) of the used vinyl.
    Probably should be more diligent.
    Thanks again.

    Tom

    Posts : 174
    Join date : 2011-04-04

    Re: SP-8 phono distortion question

    Post by Tom on Wed Jun 07, 2017 8:32 am

    Well it worked.
    I actually did use the Magic Eraser
    (lifetime supply for 2 bucks at Walmart ;p)
    and dang if it didn't fix it.
    Replayed the same passages and they're crystal clear.
    You guys saved the day.
    Smile
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    WntrMute2

    Posts : 111
    Join date : 2010-11-21

    Re: SP-8 phono distortion question

    Post by WntrMute2 on Thu Jun 08, 2017 2:41 pm

    Glad you fixed your problem but for others with similar issues, don't forget to check the actual alignment of your cartridge.
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    deepee99

    Posts : 1596
    Join date : 2012-05-23
    Location : Wallace, Idaho

    Re: SP-8 phono distortion question

    Post by deepee99 on Fri Jun 09, 2017 2:15 am

    WntrMute2 wrote:Glad you fixed your problem but for others with similar issues, don't forget to check the actual alignment of your cartridge.  

    Even with a good protractor, correctly setting-up and aligning a tone arm and cartridge is the biggest PITA, in my experience, in all of audio-land --- made only worse by the new high-end tone-arms that don't have a detachable headshell, which, set up right the first time can be swapped out for another correctly set up different cartridge/stylus combo with simple tracking weight and anti-skating adjustments. The argument for a single casting over the old detachable sort is that the added stiffness is a Very Good Thing. This may perhaps be true if you're running $10,000 MC carts but my guess is that the real reason is, it's cheaper to make a one-piece unit than bother with all those threads and contacts and such.
    There are a lot of mom'n'pop outfits who can replace the stylus of a one-piece MC cart with just as much precision and quality and at far lower cost than Denon or Ortofon charge.
    A caution about LAST; it's great stuff but make sure it doesn't soften or dissolve the glue that holds the sharp thingie to the cantilever. On some carts it can. And whoever invented Magic Eraser should be given the civilian equivalent of the Congressional Medal of Honour. Best stuff in the world for cleaning old tube pins, too. How it can tell the difference between crud and substance is the sort of miracle around which religions emerge.

    Dogstar

    Posts : 234
    Join date : 2014-06-23

    Re: SP-8 phono distortion question

    Post by Dogstar on Fri Jun 09, 2017 6:56 am

    deepee99 wrote:How it can tell the difference between crud and substance is the sort of miracle around which religions emerge.

    When you put hot liquid in a thermos and it stays hot. And when you put cold liquid in a thermos and it stays cold. How does it know?

    Tom

    Posts : 174
    Join date : 2011-04-04

    Re: SP-8 phono distortion question

    Post by Tom on Fri Jun 09, 2017 8:27 am

    Thankfully, I have an old Technics so can swap headshells,
    and lack a thermos.
    Between those two blessings and my trusty Wattgate 381,
    I feel my life is essentially complete.

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